The study examined common plantain, Plantago major; common toadflax, Linaria vulgaris; and common dandelion, Taraxacum officinale. These perennial species were introduced from Europe, have occurred around Churchill for more than 60 years and persist in the study area through seeds or, particularly for toadflax, rhizome fragments. Researchers established two experiments in 2021 and 2023 to examine the overall effect of translocated dump soil rather than trying to separate its potentially overlapping influences, including nutrient enrichment, disturbance and the transport of plant propagules.

Churchill, at 58.5 degrees north, has long received seeds and other plant material from southern agricultural areas. A railway has connected the town’s wharf and grain elevator with southern farming regions since 1931, carrying grain that contained contaminants cleaned from shipments before export. Material from these shipments was disposed of in several dumps near town. Some sites were also used for local manure disposal and may have received household or garden waste. Their soils are visibly darker than surrounding soils, suggesting greater organic content and previous nutrient enrichment, and some have become dominated by persistent non-native plants. Soil from these areas is regularly moved for activities including road construction, power-line maintenance and gardening.

In the first experiment, a spatially replicated common garden was established in August 2021 near the Churchill Northern Studies Centre, about 20 kilometres east of town. The site had sparse vegetation on stony marine sediment and was considered representative of disturbed ground vulnerable to soil dumping. Researchers created thirty 25-by-25-centimetre plots. Half were disturbed with a rake to a depth of five centimetres while retaining their original soil; in the other half, the original soil was removed to that depth and replaced with homogenized soil collected from three dumpsites at the Port of Churchill.

One transplant of each species was placed in every plot: a shoot with five centimetres of rhizome for toadflax and a complete rosette with roots for plantain and dandelion. The plots were monitored through three growing seasons from 2022 to 2024, with survival, plant dimensions and ramet or leaf counts recorded for each species. Soil origin did not significantly affect the survival of any species, although survival declined significantly over time for all three. No toadflax or dandelion in control plots survived beyond 2022. By 2024, only three transplants remained: one plantain in dump soil, one plantain in control soil and one toadflax in dump soil, limiting later comparisons.

Dandelion was the only species whose physical size showed a clear initial response in the common garden. One year after transplanting, its leaves averaged 7.6 centimetres in dump soil and 4.9 centimetres in control soil, a statistically significant difference. The number of leaves subsequently decreased from averages of 8.7 and 7.0 in dump and control soil in 2022 to 5.0 in dump soil in 2023. Plantain leaf numbers also declined over time, while its leaves tended to shorten, although that change was only marginally non-significant. Toadflax height and ramet number did not differ by soil origin. Too few plants survived for meaningful biomass or flowering comparisons, so the experiment could not establish whether dump soil altered those outcomes across the full three-year period.

The second experiment, established in August 2023, tested soil depth across two roadside habitats. Sixteen locations were placed near the research centre, with eight along Palsa Road beside lichen-heath tundra and eight along Twin Lakes Road beside white-spruce-dominated boreal forest. Each location contained three 25-by-25-centimetre plots: one received five centimetres of dump soil, one received 20 centimetres and a control was disturbed to five centimetres while retaining its original soil. Transplants of the same three species were added to every site, and researchers separately recorded seedlings emerging from the seed bank in the imported material.

Plants in the deepest treatment generally grew larger. Toadflax in 20-centimetre dump soil reached average heights of 19.2 centimetres in tundra and 16.2 centimetres in boreal forest, compared with 3.1 and 4.1 centimetres in the respective controls. It also produced more ramets: 9.1 on average in tundra and 7.8 in forest, versus 2.8 and 4.7 in control soil. Plantain had significantly longer leaves in dump soil, with 20-centimetre treatments averaging 7.3 centimetres in tundra and 11.5 centimetres in forest, compared with 5.2 and 4.6 centimetres in controls. Dandelion also had longer leaves and more leaves in dump soil. Habitat effects were generally not significant, although plantain leaves tended to be slightly longer in the forest.

The growth advantage was also reflected in dry biomass after one growing season. Toadflax in 20-centimetre dump soil averaged 2,586 milligrams in tundra and 1,494 milligrams in forest, compared with 235 and 200 milligrams in controls. Plantain averaged 434 milligrams in tundra and 578 milligrams in forest in deep dump soil, versus 172 and 137 milligrams in controls. Dandelion weighed 884 milligrams in tundra and 1,504 milligrams in forest in the deepest treatment, compared with 317 and 151 milligrams in controls. Soil depth significantly affected biomass for all three species, and the models showed a general trend toward greater production with deeper soil. Inconsistent, non-significant habitat effects meant that neither tundra nor boreal forest was consistently more productive for every species.

Improved growth did not consistently translate into improved survival. In the roadside experiment, neither soil depth nor habitat significantly affected the survival of toadflax or plantain, while dandelion survival was higher in boreal forest than in tundra. Seedlings of five non-native species emerged from the imported soil: shepherd’s purse, hemp-nettle, plantain, dandelion and field pennycress. Neither treatment depth nor habitat produced a statistically significant difference in emergence, and the analysis of the number of germinated seedlings was not significant for either factor. The researchers noted that successful germination generally occurs at or near the soil surface, so deeper layers may contain seeds while offering a lower chance of emergence. The experiment recorded germinated seedlings but did not assess ungerminated seeds.

The authors interpret the growth response primarily as a likely consequence of the nutrient-enriched nature of dumpsite soils, although their experiment was designed to measure the overall effect of translocated soil rather than isolate individual causes. Nutrient-poor subarctic environments may benefit plants adapted to productive disturbed habitats, while repeated roadside disturbance can also alter soil properties and microbial communities. The short-lived nature of the response remains central to the findings. Despite increased growth in favourable soil, transplanted non-native plants generally failed to persist, suggesting that ameliorated below-ground conditions alone were insufficient to overcome local environmental constraints. The experiments involved small soil volumes, while the authors have observed multi-year persistence at sites where truckloads of soil were deposited; they did not experimentally compare those larger movements with the small treatments used here.

Climate change may interact with this temporary establishment advantage. High-latitude environments are warming faster than the global average, and previous studies cited by the authors found that warming can improve the performance of non-native plants in northern ecosystems. Dandelion has also been reported as more abundant in warmer microsites in Churchill. The present experiments did not test climate warming directly, but their results identify human movement of soil as a local disturbance that can give temperate-origin species a measurable head start in tundra and boreal forest. The supported conclusion is therefore narrower than a prediction of inevitable invasion: dump soil can briefly improve growth and allow plants to emerge in previously uninvaded habitats, yet persistence depends on conditions and the scale of disturbance, which remain important uncertainties.

Subject of Research: Effects of anthropogenically modified dump soil on non-native plant growth in subarctic ecosystems

Article Title: Anthropogenically-modified soil increases the performance of non-native plants in a subarctic ecosystem

Article References: Zhang, V. M., & Kotanen, P. M. (2025). Anthropogenically-modified soil increases the performance of non-native plants in a subarctic ecosystem. NeoBiota, 104, 59-72. https://doi.org/10.3897/neobiota.104.160626

Image Credits: AI Generated

DOI: 10.3897/neobiota.104.160626

Keywords: non-native plants, dump soil, soil transport, plant invasion, Churchill, subarctic ecology, tundra, boreal forest, plant establishment, field experiments, Anthropogenically-modified, soil

The genus Lochetica is what taxonomists call species-poor: until now, only four species were recognised worldwide, all restricted to the Holarctic region encompassing Europe, northern Asia and North America. For much of the twentieth century, scientists knew of just two species, Lochetica westoni and Lochetica pimplaria, until the latter was synonymised with the former in 1972. A revision in 1983 added two more species, Lochetica farta from Taiwan and Lochetica agonia from the western United States, and in 2021 Lochetica japonica was described from Japan. Apart from L. westoni, every species in the genus is known from only a handful of specimens, and the biology of most of them remains a complete mystery.

The story of the new species began when the author of the study noticed that Finnish museum collections appeared to contain two tentatively distinct morphological forms of Lochetica, even though only a single species, L. westoni, had ever been recorded in Europe. To resolve whether these forms truly represented different species, he assembled a dataset of 88 specimens drawn from museum collections in Helsinki, Lund, Norwich and Odawara, as well as a private collection in Finland. The material included type specimens from the original nineteenth-century descriptions, examined through high-resolution photographs, allowing direct comparison with specimens collected as far back as 1928.

The morphological evidence centred on two quantitative characters. The first, the ovi-tib ratio, compares the length of the ovipositor projecting beyond the tip of the metasoma with the length of the hind tibia. The second, the temple ratio, compares the width of the temples behind the eyes with the maximum width of the head. Statistical comparison using the Welch t-test revealed striking differences. The mean ovi-tib ratio was 2.8 in L. westoni but only 2.1 in the new species, a difference so pronounced that the effect size, measured by Cohen’s d, reached 5.3. Remarkably, no overlapping specimens were found for this character, although the gap between the species is narrow: the maximum recorded for the new species is 2.4 and the minimum for L. westoni is 2.6.

The temple ratio also differed significantly, averaging 0.95 in the new species against 0.88 in L. westoni, although here numerous specimens overlapped. Beyond the measurements, a suite of qualitative characters separates the two wasps. The new species has weak latero-median carinae on the first metasomal tergite that do not reach the level of the spiracles, weaker crenulae along the sternaulus, and black or dark brown tegulae, the small plates at the base of the wings. L. westoni, by contrast, has strong carinae, stronger crenulae, a longer ovipositor and yellow tegulae. Compared with the Japanese L. japonica, the new species shows a uniformly sloping vertex with almost granulate sculpture, predominantly red legs and reddish mandibles, whereas the Japanese species has deeply punctate head surfaces, nearly black legs and predominantly black mandibles.

Molecular evidence sealed the case. Ten specimens were sequenced for the cytochrome oxidase subunit I marker, the standard DNA barcode region, using a single middle leg from each wasp. Combined with three publicly available sequences from Norwegian specimens, the dataset of thirteen sequences produced a distance matrix and a Neighbour-Joining tree. The results were unambiguous: interspecific distances between the two Finnish forms ranged from 7.12 to 8.05 percent, while intraspecific variation within each form was negligible, at most 0.16 percent in the new species and 0.61 percent in L. westoni. This clean barcode gap, visualised in a phylogenetic tree, is exactly the pattern expected when two reproductively isolated species are compared.

The new species was described from a substantial type series, including a holotype collected in June 2021 on the wall of a log barn beside a meadow near Kuopio, and 37 female and one male paratypes spanning Finland from 60 to 64 degrees north. Its known distribution falls mainly within the boreal forest biome, with a few specimens from the northern edge of the temperate broadleaf and mixed forest zone. The specimens were collected from open biotopes and from coniferous forests, with traps mounted on dead and dying Norway spruce, on burned pine forests, and even on the wall of a log building. Intriguingly, both species occur in the same habitats and sometimes the same locations, but the new species appears more common in shaded, spruce-dominated forests, while L. westoni seems to favour more exposed sites. The author cautions, however, that more data are needed for reliable comparisons.

The study also produced new host records that illuminate the strange life history of these wasps. L. westoni is a parasitoid of Passaloecus, a genus of small crabronid wasps that nest in beetle burrows in dead wood, in galls and in plant stems. The new rearing records published in the study include males and females reared from Passaloecus monilicornis, P. eremita and P. borealis, and the new species itself has been reared from P. monilicornis. Earlier work suggested that the female L. westoni must oviposit while the host nest is still under construction, because her ovipositor is not long enough to pierce the outer resin plug that seals the completed nest. The wasp overwinters as a larva inside a silky cocoon within the host’s nest chamber.

One of the most curious patterns in the genus concerns its males. In the studied material, females outnumbered males dramatically, 38 to 1 in the new species and 40 to 5 in L. westoni. Yet the original reared type series of L. westoni from 1880 contained 15 males against 9 females, suggesting a normal sex ratio. The most likely explanation is that the males are simply short-lived and therefore almost never encountered by collectors, although the difficulty of identifying male Phygadeuontinae may also mean they languish unsorted in museum drawers. Three of the five known species remain known only from females, and the males of two species have never been seen.

The discovery carries a broader message about biodiversity in well-studied regions. If a new species of parasitoid wasp could slip through decades of Finnish collecting, hidden inside a genus with only four known species, then many more await recognition. The author notes that the new species is almost certainly present in neighbouring countries and may have been confused with L. westoni elsewhere, and that future work should examine large amounts of museum material across wide geographic areas. For now, the five known species of Lochetica can finally be told apart, thanks to a combination of careful morphology, vintage museum specimens and a few millimetres of wasp DNA. The species name honours the author’s grandfather Raimo, known as Rami, whose influence kindled a love of nature that ultimately led to the wasp’s discovery.

Subject of Research: Taxonomic description of a new Darwin wasp species, Lochetica ramii, from Finland using morphology and DNA barcoding

Article Title:  Lochetica ramii sp. nov. – a new species of Lochetica Kriechbaumer, 1892 ( Hymenoptera , Ichneumonidae , Phygadeuontinae ) from Finland, with a key to world species

Article References: Paappanen, J. (2024). Lochetica ramii sp. nov. – a new species of Lochetica Kriechbaumer, 1892 (Hymenoptera, Ichneumonidae, Phygadeuontinae) from Finland, with a key to world species. Deutsche Entomologische Zeitschrift, 71(1), 193-208. https://doi.org/10.3897/dez.71.121217

Image Credits: AI Generated

DOI: 10.3897/dez.71.121217

Keywords: Lochetica ramii, Ichneumonidae, Darwin wasps, new species, Finland, DNA barcoding, COI, parasitoid wasps, Passaloecus, taxonomy, boreal forest, Hymenoptera

The team, led by Mika Rantanen of the Finnish Meteorological Institute together with ecologists and geographers including Juha Aalto, Miska Luoto, Julia Kemppinen and Pekka Niittynen, installed Tomst TMS-4 dataloggers in three contrasting study areas: Kilpisjärvi in northwestern Finland, dominated by oro-arctic tundra and mountain birch forest; Rásttigáisá in Norway, a rugged treeless mountain terrain; and Värriö Strict Nature Reserve in northeastern Finland, a largely boreal forest landscape with open wetlands. The loggers recorded near-surface air temperature at 15 centimeters height and soil temperature at 6 to 8 centimeters depth at 15-minute intervals, with a precision of 0.0625 degrees Celsius, capturing the thermal world as most organisms actually experience it rather than as represented by standard weather stations or climate models.

From these dense measurements, the researchers calculated four key variables that characterize the thermal growing season: its beginning, its end, its length in days, and the accumulated growing degree day sum, defined as the cumulative sum of daily mean temperatures exceeding the 5 degrees Celsius threshold during the season. The growing season onset was identified using the so-called integral method, which finds the date when daily mean temperature permanently rises to or above 5 degrees Celsius by locating the minimum of the cumulative sum of temperature minus threshold. A single warm day does not start the season if subsequent cold days lower the cumulative sum, making the definition robust against short-term weather fluctuations.

The results reveal a pronounced asymmetry between the start and the end of the growing season. The onset exhibited substantial spatial heterogeneity, particularly in the tundra environments, where the earliest and latest onsets within the same season differed by up to 40 days. In Rásttigáisá, the median standard deviation of the onset across loggers was 13.5 days, 82 percent higher than in Kilpisjärvi and nearly four times higher than in Värriö. In the exceptionally snowy year 2020, the range of variation in onset across the Rásttigáisá loggers reached 74 days, with one logger on a northeast-facing slope recording a growing season that began only on 4 August and lasted just 41 days, accumulating a mere 104 growing degree days.

In contrast, the end of the growing season showed remarkably little spatial variability, with standard deviations between loggers ranging from just 0.2 to 2.8 days. The termination often occurred in distinct pulses, with many sites reaching the end of the season within just a few days, and sometimes a cold spell was intense enough to end the season on the same day for all loggers in an area, as happened in Rásttigáisá on 12 September 2023 and 19 September 2024. This pattern indicates that the end of the growing season is primarily controlled by large-scale meteorological forcing, such as the passage of cold air masses associated with changing weather patterns, rather than by local landscape factors like topography or vegetation.

Consequently, the spatial variability in growing season length was primarily driven by differences in its onset, which were largely associated with spatial variations in snowmelt timing. The correlation between average snowmelt timing and growing season onset was high in the tundra areas, reaching 0.93 in Rásttigáisá and 0.81 in Kilpisjärvi, compared with a weaker 0.51 in the boreal forest of Värriö. The researchers estimated average snowmelt dates using PlanetScope satellite imagery at 3-meter resolution, classifying each pixel as snow or no-snow with a pre-trained Random Forest model and applying a pixel-based binomial generalized linear model to identify the date at which snow probability drops below 0.5. In Kilpisjärvi alone, 429 individual satellite scenes were used for this analysis.

The study also found that growing degree sums varied markedly within areas, with differences of about 400 degree days between the warmest and coldest places. In the predicted fields based on linear regression models using topographic predictors derived from 2-meter resolution digital terrain models, the modelled growing degree day values differed by more than 300 degree days between the summit and base of the Saana mountain in Kilpisjärvi. Interestingly, the relationship between growing degree days and elevation showed opposing patterns between tundra and boreal forest landscapes: in the tundra areas, growing degree days were negatively correlated with elevation, with correlation coefficients of -0.85 in Kilpisjärvi and -0.75 in Rásttigáisá, while in Värriö the correlation was positive at 0.36, likely because the fell tops above the surrounding forested valleys receive more direct solar radiation and accumulate more degree days than the shaded depressions below.

The exceptionally warm summer of 2024 provided a rare opportunity to examine an extreme growing season in high-latitude microclimates. In Kilpisjärvi, the median growing degree day sum of the 185 loggers reached 820 degree days in 2024, exceeding even the highest values recorded at individual sites during 2020 to 2023, and corresponding to conditions normally experienced approximately 200 kilometers further south. The highest logger value in Kilpisjärvi reached 1005 degree days, matching the typical sum observed in Rovaniemi, 300 kilometers south. In Rásttigáisá, the 2024 values were almost entirely above the previously observed microclimatic range, where even the coldest locations in 2024 were at least as warm as the warmest loggers in earlier years, with a median of 891 degree days. In Värriö, the median reached 1037 degree days with a maximum of 1229 degree days.

Placing these values in longer-term context using data from the Finnish Meteorological Institute’s weather stations, the 2024 growing season was the warmest on record at both Kilpisjärvi stations, and at the Sodankylä Tähtelä station, where observations extend back to 1908, the growing degree day sum reached 1314 degree days, clearly surpassing the previous record of 1204 degree days from 1937. Recent analysis suggests that summer 2024 in Sodankylä was very likely the warmest in at least 2,000 years, meaning the growing degree day values observed in 2024 were probably the highest of the entire Common Era. Notably, the exceptionally high degree day sums in 2024 were primarily driven by sustained, unseasonably high temperatures during the growing season rather than by an unusually early start or late termination, and in most cases the within-area variability in 2024 did not differ significantly from previous years according to Levene’s test, indicating that warmer average conditions did not substantially alter the spatial heterogeneity of the thermal landscape.

The findings demonstrate the value of dense microclimate observation networks for advancing understanding of microclimatic processes at ecological scales in cold ecosystems. Because the Arctic is warming two to four times faster than the global average, and because comparisons with climate projections suggest that the 2024 growing season in northern Fennoscandia roughly resembles typical conditions expected at the end of the 21st century, the study provides an early glimpse of the thermal conditions that northern ecosystems may encounter more frequently in the future. The results also suggest that the substantial spatial heterogeneity of growing season characteristics, driven primarily by local environmental conditions such as snowmelt timing and topography rather than by the precise threshold used to define the season, would persist even as average conditions warm, meaning that the fine-scale thermal mosaic of northern landscapes will remain a fundamental feature of these environments as climate change continues.

Subject of Research: Climate Science

Article Title: Substantial spatial heterogeneity in growing season dynamics across northern environments

Article References: Rantanen, M., Niittynen, P., Kämäräinen, M., Kemppinen, J., Rissanen, T., Tyystjärvi, V., Luoto, M., & Aalto, J. (2026). Substantial spatial heterogeneity in growing season dynamics across northern environments. Theoretical and Applied Climatology, 157(11), Article 719. https://doi.org/10.1007/s00704-026-06648-3

Image Credits: AI Generated

DOI: 10.1007/s00704-026-06648-3

Keywords: microclimate, Arctic warming, phenology, growing season, tundra, boreal forest, snowmelt, Fennoscandia, Substantial, spatial, heterogeneity, growing

The scale of the knowledge gap that motivated the study is staggering. Moths and butterflies, with roughly 170,000 to 180,000 described species, are among the most diverse animal groups on Earth, and the vast majority of them rely on pheromones—airborne chemical signals—to find mates. Yet sex pheromones have been chemically identified for only about 700 moth species, and field-confirmed attraction to synthetic mixtures extends that figure to roughly 2,000 species. That is less than two percent of the lepidopteran species presumed to communicate chemically. The shortfall reflects decades of research prioritized by economics: pheromone science has concentrated overwhelmingly on agricultural and forest pests, leaving keystone, indicator, and threatened species in remote regions largely ignored.

The study’s design was elegantly economical. Rather than attempting the costly laboratory work of extracting and identifying a pheromone for each target species, the researchers exploited a well-known shortcut in chemical ecology: many related moth species share the same building blocks for their pheromones. Eight commercially available (Z)-monounsaturated aliphatic compounds—chemicals such as (Z)-7-dodecenyl acetate, (Z)-9-tetradecenyl acetate, and (Z)-11-hexadecenal—were selected based on prior knowledge of noctuid pheromones accumulated by the early 1990s. These were deployed singly and in binary mixtures, some at multiple component ratios, producing 26 distinct lure types, each impregnated onto red rubber septa at a dose of one milligram.

The fieldwork took place across three contrasting sites in the central Kola Peninsula, all within the subarctic boreal forest zone. One was a sparse, dry Scots pine forest severely damaged by emissions from the Monchegorsk copper–nickel smelter; a second, a lightly polluted Norway spruce–mountain birch stand beside a sedge bog; and the third, a dense old-growth spruce forest bordering a peat-moss bog some 64 kilometers southeast of the city. In total, 260 white delta traps with sticky inserts were suspended from tree branches at heights of one to two meters, spaced at least ten meters apart to prevent chemical plumes from interfering with one another. The traps ran from 17 July to 12 August 1993 and were inspected three times over the exposure period.

The catch was remarkable in its diversity for so brief a campaign. The traps captured 18 moth species spanning six families: one Yponomeutidae, one Argyresthiidae, one Coleophoridae, one Crambidae, two Geometridae, and twelve species of Noctuidae, the owlet moths. In total, 352 noctuid individuals were taken, alongside nearly 2,100 specimens from the non-noctuid species. Five lure compositions attracted nothing at all, but the remaining 21 drew moths from across the regional fauna—many of them species that had resisted other collection methods, including the fermented sugar bait traps traditionally used by lepidopterists in the region.

Some of the individual successes were dramatic. A binary 1:10 mixture of (Z)-5-tetradecenyl acetate and (Z)-7-tetradecenyl acetate proved highly attractive to the yponomeutid moth Paraswammerdamia conspersella, snaring some 1,800 individuals even though neither compound alone worked: (Z)-7-tetradecenyl acetate on its own caught only a handful, and (Z)-5-tetradecenyl acetate caught none. The case illustrates a central principle of pheromone chemistry—ratio matters. For the unidentified Coleophora species, the strongest response came to a 10:1 blend of (Z)-5-decenyl acetate and (Z)-7-dodecenyl acetate, with three of the five effective lures for that moth containing (Z)-5-decenyl acetate, a compound already known to attract several of its relatives. Argyresthia pygmaeella, the second most abundant moth in the region, was drawn to (Z)-11-hexadecenyl acetate, the same lure that attracted the crambid Eudonia murana.

Among the twelve noctuids, patterns emerged that echoed findings from as far away as Northern Finland and North America. All four lures attractive to Syngrapha parilis contained (Z)-7-dodecenyl acetate, consistent with earlier Finnish work, and that same compound attracted five related Syngrapha species in previous studies elsewhere. Sympistis funebris responded most strongly to a 1:10 mixture of (Z)-7-tetradecenyl and (Z)-9-tetradecenyl acetates, while Sympistis lapponica favored a 1:100 blend of (Z)-7-dodecenyl acetate with (Z)-9-tetradecenyl acetate. Enargia paleacea was taken with a 10:1 mixture of (Z)-9-tetradecenyl acetate and (Z)-11-hexadecenyl acetate—remarkably, the same two components, at a very different 1:500 ratio, attract its North American cousin E. infumata. Mniotype adusta, Diarsia mendica, and Coranarta cordigera all responded to lures featuring (Z)-9-tetradecenyl acetate, with the latter two showing their largest catches to blends containing a minor proportion of (Z)-11-hexadecenal, a component never before reported as attractive for any Diarsia species.

The study also delivered a sobering lesson about the limits of single-chemical fixes. Several lures attracted multiple moth species, a phenomenon well documented in earlier work: synthetic pheromones aimed at Grapholita plum moths in Bulgarian orchards inadvertently drew 29 and 12 additional leafroller species respectively, and lures developed for six economically important forest pests in Czechoslovakia attracted 32 species in total. Non-target species, it turns out, often share one or more key pheromone components with the intended targets. For monitoring programs, this cross-attraction is a double-edged sword—it can inflate bycatch and complicate species-specific counts, but it also multiplies the informational value of every trap, effectively surveying whole communities with a modest chemical toolkit.

Perhaps the most practically significant finding concerns what the synthetic lures did not catch. Only four of the twelve noctuid species attracted—Enargia paleacea, Mniotype adusta, Diarsia mendica, and Eurois occulta—overlapped with the 21 species collected using fermented sugar bait traps at the same sites in 1991–1993. The two methods, in other words, sample largely complementary slices of the moth fauna. The authors suggest that combining chemical lures with sugar baits would substantially enhance monitoring efficiency in subarctic forests. Meanwhile, several abundant local species, including Acronicta auricoma, Hyppa rectilinea, and multiple Xestia species, remain stubbornly resistant: none responded to the lures, and their attractants are still unknown. The study also failed to confirm an earlier report of (Z)-11-hexadecenyl acetate attracting Anarta melanopa, a species known to fly during the trap period, a reminder that geographic variation in pheromone composition can undermine lure performance across regions.

Why publish a dataset from a field season more than three decades old? The researchers explain that the industrial pollution gradient project the lures were designed for was terminated in 1993, and a comparison with the Pherobase database revealed no published attractant information for 14 of the 18 species captured. Rather than let the data languish, the team released these preliminary but unique results to support future monitoring programs for boreal and subarctic moths. In an era of rapid climate-driven range shifts and expanding industrial footprints in northern forests, reliable tools for tracking moth populations—many of which are keystone pollinators, herbivores, and prey items—are increasingly urgent. The Kola Peninsula experiment demonstrates that straightforward, widely accessible screening of common pheromone analogues can reveal attractants for species rarely targeted by pheromone science, helping to close one of chemical ecology’s most persistent geographic blind spots, one sticky trap at a time.

Subject of Research: Identification of synthetic sex attractants for boreal forest moth species through field pheromone lure screening

Article Title: New sex attractants for 14 boreal forest moth species ( Lepidoptera )

Article References: Kozlov, M. V. (2026). New sex attractants for 14 boreal forest moth species (Lepidoptera). Nota Lepidopterologica, 49, 51-61. https://doi.org/10.3897/nl.49.178270

Image Credits: AI Generated

DOI: 10.3897/nl.49.178270

Keywords: Lepidoptera, sex pheromones, boreal forest, Kola Peninsula, Noctuidae, chemical ecology, field screening, moth monitoring, synthetic lures, subarctic, pheromone analogues, insect conservation

The stakes are far higher than one snowy field site might suggest. Mixed-phase clouds, in which supercooled liquid droplets and ice crystals coexist between 0 and minus 40 degrees Celsius, dominate the mid- and high-latitudes and exert a powerful influence on Earth’s radiative balance and precipitation. At high latitudes, where ice-albedo feedbacks and polar warming amplification are strongest, these clouds play an outsized role in the climate system. Yet their behavior hinges on ice-nucleating particles, or INPs, which are astonishingly scarce: for much of the heterogeneous freezing spectrum, they represent as little as one in a million of all atmospheric particles. Predicting their occurrence and abundance remains one of the great uncertainties in climate modeling, which is why the Hyytiälä team turned to an unconventional ally in their quest.

Between February and June 2018, the researchers deployed two continuous-flow diffusion chambers, the Portable Ice Nucleation Chamber known as PINC and its upgraded successor PINCii, to sample ambient air with unprecedented temporal resolution. Each instrument operated in a repeating cycle of five minutes of particle-free background measurement followed by fifteen minutes of ambient sampling, yielding one INP concentration data point every twenty minutes. PINC ran from 19 February to 2 April at a lamina temperature of minus 31 degrees Celsius, while PINCii took over from 22 April to 10 June at minus 32 degrees, both at a relative humidity with respect to water of 105 percent. The two chambers agreed within a factor of two during overlapping checks, and their sequential operation provided near-continuous high-frequency coverage across the dramatic seasonal transition from snow-covered winter to the awakening boreal spring.

The real innovation lay in pairing these measurements with the staggering observational infrastructure of SMEAR II, a station embedded in the Integrated Carbon Observation System, the Aerosol, Clouds and Trace Gases Research Infrastructure, and the Swedish Infrastructure for Ecosystem Science. The team interrogated 509 individually monitored variables spanning meteorology, radiation, soil conditions, aerosol physics, and trace gas chemistry. After quality screening that removed variables plagued by missing values, constant readings, and redundant duplicates, 84 parameters survived for analysis. All were harmonized to a common twenty-minute time base, creating a multidimensional dataset against which the INP measurements could be tested for hidden structure.

The machine-learning toolkit included random forest and decision tree models for feature importance ranking, alongside principal component analysis and K-means clustering for dimensionality reduction and pattern exploration. Crucially, the authors emphasize that these were exploratory tools for hypothesis generation rather than predictive modeling; no train-test splits or cross-validation were performed. To guard against statistical flukes, the random forest analysis was repeated under 50 independent random seeds, and the top-ranked variables remained stable across all of them. When many variables are screened simultaneously, the probability of finding spurious correlations rises sharply, and the researchers are explicit that their identified associations require independent validation before any causal claims can be made.

The rankings that emerged were revealing. The six highest-ranked predictors included nitrate aerosol mass measured by an aerosol mass spectrometer, the number concentration of particles between 250 and 1000 nanometers, fluorescent biological aerosol particle counts from a Wideband Integrated Bioaerosol Sensor, gas-phase acetone concentrations, cloud condensation nuclei at low supersaturation, and the time air masses had spent over land according to back-trajectory analysis. Fluorescent particles, detected through dual ultraviolet excitation, serve as tracers for primary biological aerosol, a well-studied INP source in forest environments. Surprisingly, indicators of black carbon also ranked highly, despite laboratory evidence that fresh soot is a poor ice nucleator, though atmospheric ageing, oxidation, and organic coating may enhance its ice activity, and a previous study at the same site independently reported short-timescale correlations between black carbon and INPs.

The seasonal split proved to be the study’s most striking finding. The winter measurements from PINC showed no meaningful correlation with any of the 84 examined variables; the fitted exponents in simple power-law relationships collapsed to near zero, meaning predicted concentrations were essentially flat regardless of what the environment was doing. In contrast, the spring and summer data from PINCii responded to ambient aerosol properties, with fluorescent particle concentration and nitrate mass both yielding moderate predictive skill, achieving adjusted R-squared values of roughly 0.5. The authors suggest that a local biogenic contribution, swelling as the ecosystem emerged from winter, augments a transported background aerosol during the growing season, making local proxies genuinely informative only in that regime.

Equally telling was the failure of established parameterizations. Widely used formulations from DeMott and colleagues and from Tobo and colleagues, which predict INP concentrations from temperature and the abundance of particles larger than half a micron, produced negative coefficients of determination against the Hyytiälä data, meaning they performed worse than simply guessing the observational mean. The Tobo parameterization, calibrated in a temperate North American forest where large particles are predominantly primary biological aerosol, systematically overpredicted INPs at the boreal site, partly because frequent new particle formation events there grow secondary organic aerosol into the relevant size range without adding ice-active particles. The team also found the INP concentration distributions to be broadly log-normal, a signature of random dilution and mixing that points to long-range transport from diverse, distant sources as the dominant winter supply mechanism, a conclusion echoing earlier work at the same station.

The deeper lesson is philosophical as much as technical. Correlation, even when machine-assisted and replicated across dozens of random seeds, does not illuminate causation, particularly when the target of interest is a vanishingly small fraction of the total aerosol and its identity remains undetermined without single-particle analysis of ice crystal residuals. The authors argue that the very question of why local measurements cannot predict INPs is itself scientifically valuable, because it constrains the problem space and redirects the field toward approaches that explicitly account for air mass history. They propose that future campaigns pair high-frequency INP measurements with source-apportionment tools such as back-trajectory analysis, receptor modeling, and, where possible, single-particle ice residual analysis, and point to efforts like the ACTRIS cloud in-situ initiative as platforms for such integrated studies.

For climate modelers, the message is clear: site-specific parameterizations rooted in local biogenic and chemical proxies, such as fluorescent particle concentrations and nitrate aerosol mass, offer the most promising path forward for boreal environments during the growing season, while winter INP populations in southern Finland appear governed by processes far beyond the forest. As the Arctic warms and mixed-phase clouds shift the energy balance of the high latitudes, understanding where ice-forming particles come from, and accepting that some of the answers lie hundreds or thousands of kilometers upwind, may prove essential to forecasting the future of the frozen North.

Subject of Research: Ice-nucleating particle concentrations and machine-learning variable screening in a boreal forest environment

Article Title: Exploring ice nucleation particle concentrations in a boreal environment: limits of machine-learning-assisted variable screening

Article References: Wu, Y., Brasseur, Z., Castarède, D., Heikkilä, P., Keskinen, J., Möhler, O., Kulmala, M., Petäjä, T., Thomson, E. S., & Duplissy, J. (2026). Exploring ice nucleation particle concentrations in a boreal environment: limits of machine-learning-assisted variable screening. Aerosol Research, 4(2), 293-309. https://doi.org/10.5194/ar-4-293-2026

Image Credits: AI Generated

DOI: 10.5194/ar-4-293-2026

Keywords: ice-nucleating particles, mixed-phase clouds, boreal forest, SMEAR II, machine learning, random forest, aerosol chemistry, fluorescent bioaerosol, long-range transport, cloud parameterization, HyICE-2018, climate modeling

The stakes are high. Nearly 80 percent of Fennoscandian forests are intensively managed, and Norway spruce is among the most productive industrial species in the region. Warming temperatures and rising carbon dioxide could, in principle, boost spruce growth in the coming decades, but only if water does not become limiting. Climate projections point in the opposite direction, forecasting more frequent droughts across the boreal zone. Norway spruce is an isohydric species, meaning it closes its stomata in response to rising vapor pressure deficit, the drying power of the air, in order to preserve leaf water potential. That strategy protects the tree’s hydraulics but comes at the cost of reduced carbon uptake, and the species’ shallow roots and generally low drought resilience on mineral soils have long worried foresters. Far less has been known about how spruce fares on peat soil, where water tables are managed by drainage ditches.

The study site offered a natural experiment. In March 2021, the stand was divided into two blocks: an untreated control and a block that was selectively harvested according to the principles of continuous cover forestry, a management approach gaining traction in the boreal region. The harvest removed 55 percent of the trees taller than 15 meters, cutting projected canopy cover from 60 percent to 22 percent and reducing leaf-area index from roughly 3 to 2 square meters per square meter. The researchers hypothesized that the thinned block, with less inter-tree competition for soil water, would weather drought better than the dense control stand, and that is largely what the data showed, though with instructive complications.

Meteorologically, the two years could hardly have been more different. The summer of 2020 was warm but drought-free by the Standardized Precipitation-Evapotranspiration Index, while June and July 2021 brought a severe drought, with monthly SPEI values as low as minus 1.87, a rainless spell lasting until late July, a steep drop in the water table, and surface soil moisture falling below the 0.2 cubic meters per cubic meter threshold the team used to define soil drought. Crucially, atmospheric drought, defined as a daily mean vapor pressure deficit above 1 kilopascal, was frequent in both years, and the hottest days saw median daytime temperatures approaching 30 degrees Celsius. The forest was thus exposed to the full spectrum of atmospheric and soil drought, separately and in combination.

The eddy-covariance tower, standing 29 meters tall on the boundary between the two blocks, revealed the ecosystem-scale signature of that stress. Net ecosystem exchange peaked at a vapor pressure deficit of about 1 kilopascal and fell toward zero as the air dried further, reaching essentially zero exchange at roughly 2 kilopascals in both blocks and both years. Light-saturated photosynthesis, ecosystem respiration, and light-use efficiency all dropped markedly in 2021 compared with 2020, and the Bowen ratio, the ratio of sensible to latent heat flux, roughly doubled during the dry summer, a classic indicator that the forest was diverting energy away from evapotranspiration. Yet the picture was not uniformly grim: drought days are typically sunnier, and the extra sunlight at least partly compensated for the reduced photosynthetic efficiency, keeping daily carbon gains comparable to those of milder days.

The most direct evidence of tree-level stress came from the sap-flow sensors installed on 16 spruce trees, eight per block. In the control stand, sap flow rose linearly with vapor pressure deficit up to about 1 kilopascal and then saturated, a sign that stomata were constricting. More striking was a progressive afternoon dip in control-tree sap flow that deepened from June through July 2021, coinciding with the daily peak in atmospheric demand, and then largely vanished in August when rains returned. Most harvest-block trees, by contrast, maintained higher sap flow across the entire vapor pressure deficit range, consistent with the idea that fewer trees sharing the same soil water reservoir face less competition. When the team upscaled tree-level sap flow to the stand using tree height relationships derived from drone imagery, the thinned block transpired roughly half as much water as the control, echoing earlier findings that thinning raises per-tree water use while lowering stand-level totals.

The drone surveys added a spatial dimension that ground sensors cannot provide. Flying a DJI Matrice 210 with thermal and multispectral cameras on four clear days, the team produced orthomosaics of canopy temperature and the Normalized Difference Vegetation Index, then segmented individual tree crowns and corrected temperatures for differences in canopy brightness. Under non-drought conditions, the two blocks were nearly indistinguishable. During peak drought, however, trees in the harvested block tended to run hotter and show lower NDVI than control trees, implying greater susceptibility to extreme drought in the open stand, possibly because thinned crowns receive more solar radiation. Rows of stressed trees also appeared along forest tracks and ditches, a spatial pattern invisible to the tower. A novel touch was the use of wet and dry reference piles of spruce branches, sprayed with the equivalent of 15 millimeters of rainfall, to convert canopy temperatures into estimates of stomatal conductance for every mapped tree.

Perhaps the study’s most valuable contribution is its honest cross-examination of the monitoring tools themselves. The sap-flow data flagged stress in the denser control stand, exactly where competition for water was fiercest, while the drone data highlighted stress in the thinned stand, where exposed crowns heated up. The eddy-covariance system, which averages fluxes over hectares, smoothed over much of this tree-to-tree variation and could not reliably detect a minority of vulnerable individuals. Each technique, the authors conclude, occupies a different niche: sap flow offers continuity and directness but covers only a handful of trees; drones offer stand-wide spatial coverage but only snapshot temporal resolution; eddy covariance offers continuous ecosystem totals but little spatial discrimination. No single method currently combines directness, continuity, coverage, and low uncertainty.

For forest management, the practical implications are tangible. The evidence that selection-harvested trees maintained higher photosynthetic uptake, sap flow, and stem growth during drought supports continuous cover forestry as a strategy for buffering spruce stands against the hotter, drier summers projected for the boreal zone. The authors also propose a deceptively simple early-warning tactic: equip the least resilient trees in a stand, those most disadvantaged by competition or exposure, with sap-flow and stem-diameter sensors, and let them act as sentinels for the onset of drought stress. As boreal summers like that of 2021 become the norm rather than the exception, such sentinel trees, watched from the ground and the air alike, may become an essential part of keeping northern forests productive and climate-friendly.

Subject of Research: Drought ecophysiology of a managed Norway spruce forest on drained boreal peatland

Article Title: Drought responses of a Norway spruce forest on drained peat soil: combining sap-flow sensors, eddy-covariance, meteorological, soil and UAV data

Article References: Alekseychik, P. K., Peltoniemi, M., Mäkipää, R., Tuominen, V., Laurila, T., Jones, H., Müller, M., Lopatin, E., Rautakoski, H., Vesala, T., & Launiainen, S. (2026). Drought responses of a Norway spruce forest on drained peat soil: combining sap-flow sensors, eddy-covariance, meteorological, soil and UAV data. Biogeosciences, 23(19), 7091-7127. https://doi.org/10.5194/bg-23-7091-2026

Image Credits: AI Generated

DOI: 10.5194/bg-23-7091-2026

Keywords: Norway spruce, drought, boreal forest, peatland, sap flow, eddy covariance, UAV remote sensing, continuous cover forestry, vapor pressure deficit, evapotranspiration, NDVI, forest management

The idea at the heart of the research is deceptively simple. In boreal Canada, forests are not uniform carpets of trees; they are patchworks of stands of different ages, shaped by a history of crown fires, insect outbreaks, succession, and, more recently, industrial logging. Before large-scale forestry, eastern Canadian boreal ecosystems supported far more mature and old-growth forest than they do today, and those old stands provided critical ecosystem services, from wildlife habitat and carbon storage to the regulation of surface water. Industrial harvesting has generally reduced the area of these stands and scrambled their distribution, simplifying the mosaic and threatening remnant old forests in some regions. Ontario’s response has been a policy framework that requires forest managers to emulate natural disturbance patterns, including a specific spatial configuration of mature and old-growth forest patches that the province calls texture.

Measuring that texture is straightforward in principle. Ontario’s Forest Management Guide for Boreal Landscapes instructs planners to divide a forested landscape into hexagons of 5,000 hectares, a size chosen because it matches the average footprint of natural disturbances in the province’s boreal forests and is meaningful for characterizing wildlife habitat. Within each hexagon, planners calculate the proportion of the area occupied by mature and old-growth stands, abbreviated as MOG. Those proportions are then sorted into five bins, ranging from hexagons with less than 20 percent MOG to those with more than 80 percent, producing a histogram that summarizes the landscape’s texture at a glance. A landscape shaped only by natural disturbance has a characteristic histogram, and the provincial guidelines ask managers to keep the managed landscape’s histogram as close as possible to that theoretical target.

The difficulty has always been operational. Forest harvest planning relies on mixed-integer optimization models, classic formulations known as Model I, Model II, and Model III, that find cost-effective harvest schedules under sustainability constraints. These models have been extended over the years to control connectivity between forest patches, adjacency between harvested and unharvested sites, and maximum harvest areas. But none of them could directly control landscape texture. Texture metrics, computed with moving-window statistics using tools such as Fragstats or Ontario’s own Landscape Tool, had to be calculated after the fact, as a post-assessment of a finished plan. If the texture came out wrong, there was no way to feed that information back into the harvest schedule. The provincial guidelines, in effect, demanded an outcome the planning machinery could not deliver.

Yemshanov and his colleagues closed that gap by modifying a Model I harvest scheduling formulation so that the texture histogram itself becomes part of the optimization. The landscape is covered with 5,000-hectare hexagons, and each harvestable forest site is assigned to the hexagon containing its centroid. For every possible harvest prescription at every site, and for every ten-year planning period across a century-long horizon, the model tracks whether the site will be in mature or old-growth condition. A decision variable calculates the MOG proportion within each hexagon, and a set of binary indicator variables sorts each hexagon into one of the five histogram bins. The model then computes a penalty measuring how far the resulting histogram deviates, bin by bin, from the theoretical target values that describe a landscape under natural disturbance alone, and it minimizes that penalty alongside its traditional goal of maximizing net harvest revenue.

The theoretical targets were supplied by the Ontario Ministry of Natural Resources and Forestry, based on stochastic simulations with the Boreal Forest Landscape Dynamics Simulator, which integrates the Canadian Forest Fire Behavior Prediction System with empirical forest succession rules. For the study area, the target shares of hexagons in the five MOG bins came out at roughly 0.17, 0.22, 0.20, 0.20, and 0.21. Because achieving an exact match may be impossible given a landscape’s existing age structure, the requirement is formulated as a penalty on deviations rather than a hard constraint, keeping the problem mathematically feasible even when the starting conditions are far from the ideal.

The team tested the approach in the Wabadowgang Noopming Forest, a boreal management unit in northwestern Ontario covering roughly 438,500 hectares across more than 30,000 harvestable sites, where industrial forestry operates under a forest management plan that also implements Ontario’s Dynamic Caribou Habitat Schedule. That schedule, designed to conserve threatened woodland caribou, concentrates harvesting into compact regions that rotate across the landscape over twenty-year cycles, maintaining large tracts of undisturbed habitat through time. The researchers compared a baseline scenario following the current plan against scenarios that added MOG texture control, both with and without the caribou schedule, and even a scenario in which texture control replaced the traditional area-based limits on young, mature, and old forest entirely.

The results were revealing. The baseline plan, constrained by the caribou schedule but blind to texture, produced a lopsided mosaic: in the first three decades, hexagons with less than 20 percent MOG fell well below the target share of 0.17, while hexagons dominated by more than 80 percent mature and old-growth forest substantially exceeded their target of 0.21. Adding texture control changed the picture dramatically. Because the target histogram demands a meaningful presence of hexagons with low MOG proportions, the optimizer dispersed harvest sites more evenly across the landscape, ensuring that every 5,000-hectare window contained some recently disturbed, young forest alongside the old. Notably, the cost of this ecological refinement was modest. Because the caribou schedule already forced harvest into compact, widely distributed regions, layering texture control on top caused only a minor increase in timber supply cost and little change in sustainable harvest levels. Without the caribou schedule, however, texture control alone allowed a higher maximum sustainable harvest of 0.323 million cubic meters per year versus 0.275 million under the combined scenario, and pushed the young-forest share up to 32.1 percent, near the plan’s upper limit.

One caution emerged clearly from the fourth scenario: texture control is not a substitute for traditional age-class management. When the researchers removed the area-based constraints on young, mature, and old-growth forest and relied on texture control plus the caribou schedule, harvested volumes rose, mean forest age fell, and the old-growth area declined substantially, with young stands exceeding the provincial maximum. Texture, in other words, governs the arrangement of the mosaic but not necessarily its total composition, and both dimensions of the landscape need explicit attention.

The study also lays bare the computational price of ecological realism. The baseline problem solved in under thirty minutes, but the texture-controlled formulations ran for seventy-two hours on a workstation with 48 processor cores and still finished with optimality gaps above 15 percent. The indirect, multi-step calculation of the histogram introduces symmetries into the data, since many different harvest configurations can produce the same histogram shape, making the problem combinatorially hard, in the formal sense of NP-hardness. The authors suggest practical workarounds, including optimizing only the most critical histogram bins, dividing large landscapes into regions solved separately, or stabilizing the coarse spatial configuration before switching penalties to hard constraints. They also note that the framework is generalizable well beyond MOG forests: the same machinery could control the texture of wildlife habitat for species such as boreal caribou at ecologically relevant scales of 10,000 hectares or more, or balance working forests, protected areas, and agricultural land in multi-use regions. As climate change alters fire regimes across the boreal zone, tools that can hold a managed landscape to a nature-like pattern, even approximately and at a computable cost, may become indispensable to keeping forestry and conservation from pulling the forest apart.

Subject of Research: Optimization of forest harvest scheduling to control the spatial texture of mature and old-growth boreal forest under competing management objectives

Article Title: Forest landscape planning with textural constraints: How to control the spatial pattern under competing management objectives

Article References: Yemshanov, D., Koch, F. H., Liu, N., & Nielsen, J. (2026). Forest landscape planning with textural constraints: How to control the spatial pattern under competing management objectives. PLOS Ecosystems, 1(2), e0000033. https://doi.org/10.1371/journal.pesy.0000033

Image Credits: AI Generated

DOI: 10.1371/journal.pesy.0000033

Keywords: boreal forest, forest management, harvest scheduling, old-growth forest, landscape texture, natural disturbance emulation, mixed-integer optimization, woodland caribou, Ontario, spatial planning, biodiversity conservation, wildfire regime

The instruments in question are chemical ionization mass spectrometers, or CIMS, the workhorses of modern atmospheric science. They are the only tools capable of sniffing out the ultra-trace gases that drive new particle formation, chiefly sulfuric acid and highly oxygenated organic molecules known as HOMs. These condensable vapors exist at concentrations ranging from parts per trillion down to parts per quadrillion, they stick tenaciously to any surface they touch, and they must be electrically charged before they can be detected at all. Each of those steps is a potential source of error, and because different research groups have built their instruments differently, results from one study have not always been comparable to another. That fragmentation has long frustrated efforts to build a global picture of how new particles form.

To confront the problem, the European research infrastructure ACTRIS organized its first dedicated CIMS field intercomparison, known as CI-FI1, over two weeks beginning on 26 July 2024 at the SMEAR II station in Hyytiälä, southern Finland. The site, surrounded by managed pine forest with only limited local pollution, is a classic location for studying new particle formation. Five of the six instruments were atmospheric pressure interface time-of-flight mass spectrometers, three fitted with traditional Eisele-type inlets and two with the newer multi-scheme MION inlets capable of rapidly switching between reagent ions. The sixth was a Vocus bipolar time-of-flight instrument coupled to a low-pressure AIM reactor, operated with iodide and benzene cluster cations. All six ran in their routine configurations, and all were calibrated using standard procedures, exactly as they would be during a normal field campaign.

The first week was devoted to side-by-side sampling of ambient air, with every inlet facing the same direction to guarantee that all instruments breathed identical air. The second week focused on calibration: sulfuric acid calibrations using a well-established method, background measurements through HEPA filters, and transmission calibrations that probe how efficiently each instrument detects ions of different masses. The conditions were far from ideal for making easy comparisons. Air temperatures ranged from 13 to 25 degrees Celsius, relative humidity averaged a damp 82 percent, and rain fell on several days, suppressing photochemistry and pushing ambient concentrations of the target vapors close to the instruments’ detection limits. In a sense, that made the exercise more valuable, not less, because it tested the instruments where they are most fragile.

For sulfuric acid measured in nitrate mode, the results were moderately good. The conventional sulfuric acid calibration, which has been the community standard for over a decade, brought the five CI-APi-ToF instruments into reasonable agreement, with a coefficient of determination of about 0.58 across the ensemble. The agreement was strongest during the daytime, when photochemical production pushed sulfuric acid concentrations to their peaks. At night, when concentrations dropped, the instruments diverged, and the scatter plots revealed a fan-like pattern with increasing dispersion at lower concentrations. Intriguingly, the data points clustered not by reagent ion chemistry but by inlet type: the three Eisele-type instruments behaved like one another, and the two MION instruments like each other.

That pattern became even more striking for the heavier molecules. When the team examined monoterpene-derived HOM monomers, spanning mass-to-charge ratios of roughly 240 to 390, and HOM dimers, from 480 to 630, sulfuric acid calibration alone was not enough to make the measurements comparable. The missing ingredient was the mass-dependent transmission of each instrument, the fact that ions of different masses are transmitted through the vacuum interface and detector with unequal efficiency. Correcting for this transmission, measured by depleting the reagent ions with a series of perfluorinated acids, substantially improved agreement for the closed-shell HOM monomers, yielding coefficients of determination of 0.68 for non-nitrate monomers and 0.81 for organonitrate monomers, rising to 0.83 and 0.89 when one problematic instrument was excluded. But the study also delivered a caution: for one instrument whose transmission curve fell to nearly zero at high masses, applying the correction produced absurdly large adjustment factors and actually worsened agreement. The lesson is that transmission corrections must be critically evaluated, not blindly applied.

The dimers told a more stubborn story. Even after all corrections, agreement for these heavy, low-volatility molecules remained poor, with a clear separation between the Eisele-type and MION instruments that persisted across the full range of concentrations. The MION instruments, with their shorter inlet tubes and more efficient delivery of ionized sample to the detector pinhole, showed both lower detection limits and higher relative transmission in the dimer mass range, allowing them to distinguish real signal from background noise more effectively. For the lighter organic and inorganic acids below mass 250, agreement was also weaker than for sulfuric acid, and the team could not pinpoint the cause, noting that applying transmission corrections did not help. These compounds, the authors conclude, remain genuinely challenging to quantify.

One of the most consequential findings concerns bromide ionization, a reagent ion scheme prized for its sensitivity to less-oxidized organic compounds but long suspected of being fragile in humid air. During the campaign, relative humidity ranged from 39 to 100 percent, well above the 20 to 40 percent threshold at which bromide sensitivity is known to decline. Yet the two MION instruments, switching every ten minutes between nitrate, bromide, and a non-ionizing mode, showed good agreement with each other for semi-volatile organic compounds, with a coefficient of determination of 0.853. Comparing bromide and nitrate measurements of the same compounds suggested that humidity did not strongly distort the relative performance of the two modes. Bromide-mode measurements, the results imply, may be more robust under real field conditions than laboratory studies had suggested, at least for compounds that form sufficiently stable clusters with the bromide ion.

Perhaps the most important conclusion of the entire campaign is about what does and does not matter. The team compared how the same compounds were detected across nitrate, bromide, and iodide modes, and found that instruments sharing the same inlet design behaved more alike than instruments using the same reagent ion. The way the three Eisele-type instruments detected a five-oxygen organic compound, for example, was clearly distinguishable from the behavior of the two MION instruments, regardless of which reagent ion was in play. The iodide-mode instrument, with its fundamentally different low-pressure reactor, stood apart from all the rest. Reagent ion chemistry matters, but the physical plumbing of the instrument, its inlet geometry, flows, pressures, and voltages, appears to shape the measurement at least as strongly.

The practical message for the atmospheric science community is twofold. First, harmonized, comparable measurements of condensable vapors across different laboratories and field sites are genuinely achievable, provided that calibration factors, inlet-loss corrections, and mass-dependent transmission corrections are all carefully measured and critically applied. Second, the community needs agreed-upon guidelines, including a consistent definition of the limit of detection, which the study showed can swing conclusions depending on how it is calculated. With new particle formation recognized as a major influence on global aerosol numbers and cloud properties, the ability to trust every instrument’s numbers is not a technical nicety. It is the foundation on which the next generation of climate models, and our understanding of how forests, oceans, and human emissions conspire to seed the sky, will be built.

Subject of Research: Intercomparison of chemical ionization mass spectrometers for measuring condensable vapors involved in atmospheric new particle formation

Article Title: Towards harmonized measurements of condensable vapors: insights from the intercomparison of six chemical ionization mass spectrometers at a boreal forest site

Article References: Righi, C., Ciobanu, M., Deot, N., Jokinen, T., Liu, C., Yuan, Q., Quéléver, L. L. J., Jorga, S., Pospisilova, V., Beck, L. J., Simon, M., Zauner-Wieczorek, M., Kürten, A., Soler, R., Vera, T., Muñoz, A., Ahonen, L. R., Yan, C., Petäjä, T., & Sarnela, N. (2026). Towards harmonized measurements of condensable vapors: insights from the intercomparison of six chemical ionization mass spectrometers at a boreal forest site. Atmospheric Measurement Techniques, 19(19), 6357-6378. https://doi.org/10.5194/amt-19-6357-2026

Image Credits: AI Generated

DOI: 10.5194/amt-19-6357-2026

Keywords: chemical ionization mass spectrometry, condensable vapors, sulfuric acid, highly oxygenated organic molecules, new particle formation, boreal forest, ACTRIS, instrument intercomparison, atmospheric aerosols, SMEAR II, reagent ions, mass spectrometry calibration

The research team, led by Enyue Zou and Miao Wang of Northeast Forestry University together with colleagues from Qufu Normal University and the Institute of Applied Ecology of the Chinese Academy of Sciences, worked in a boreal forest dominated by Larix gmelinii, the Dahurian larch. The site sits at the heart of one of Earth’s largest continuous boreal belts, a biome where cold temperatures slow decomposition and keep nitrogen locked away in soil organic matter. Because plant growth in these forests is typically constrained by nitrogen availability, scientists have long assumed that any extra nitrogen arriving from the atmosphere would be snapped up eagerly by trees and soil microbes alike. The new study shows the reality is far more nuanced.

To follow the nitrogen, the researchers used one of the most powerful tools in ecosystem science: isotopic labeling. They applied paired tracers of nitrogen-15, a rare heavy isotope of nitrogen, in the form of both 15NH4+ and 15NO3−. Because the isotope behaves chemically like ordinary nitrogen but can be detected with a mass spectrometer, every atom of labeled nitrogen that enters a leaf, a fine root, or a soil aggregate leaves a measurable fingerprint. The team established four long-term treatments—a control plus low, medium, and high nitrogen addition—and then traced the labeled nitrogen through five distinct pools: leaves, branches, fine roots, coarse roots, and soil.

The first surprise came at the very start of the tracer’s journey. Ammonium-derived nitrogen entered fine roots more rapidly in the early stages, producing a higher short-term uptake rate than its nitrate counterpart. This makes physiological sense: ammonium is already in a reduced form and can be assimilated directly into amino acids inside the root, whereas nitrate must first be reduced by the enzymes nitrate reductase and nitrite reductase before it can be used—a process that costs energy and takes time. Conifers, in particular, have historically been described as ammonium specialists, and the early uptake pattern in these larch trees fits that classical picture.

But the story changed dramatically as time passed. Nitrate-derived nitrogen proved to be the long-distance traveler of the pair. During the middle and later stages of the experiment, especially under medium and high nitrogen addition, nitrate-derived nitrogen was transported more readily to the leaves and branches above ground. This suggests that once nitrate is taken up, it moves through the xylem stream with relative ease, delivering nitrogen to the canopy where it fuels photosynthesis. In other words, the two forms of deposited nitrogen follow fundamentally different routes through the tree: ammonium is captured quickly and processed locally in the roots, while nitrate behaves more like a mobile courier service running from soil to crown.

Perhaps the most consequential finding concerns what long-term nitrogen addition did not do. Contrary to the expectation that chronic fertilization would continuously boost the fine roots’ appetite for nitrogen, the study found no sustained enhancement of fine-root uptake of the labeled tracer. What changed instead was the plumbing. Nitrogen addition promoted the transfer of labeled nitrogen from fine roots—the short-lived, high-turnover organs that do most of the absorbing—into coarse roots and then into aboveground organs. Under elevated nitrogen deposition, the forest essentially rerouted its internal nitrogen traffic, pushing a larger share of newly acquired nitrogen upward through the woody transport network rather than letting it linger below ground.

The soil, meanwhile, played the role of a temporary vault. Immediately after both nitrogen forms were applied, the soil was the major short-term sink, holding the bulk of the labeled nitrogen through microbial immobilization, exchange with mineral surfaces, and physical fixation. This initial retention is critical for the global carbon cycle, because nitrogen retained in soils can influence how much carbon forests store; previous work, including a 2022 analysis in Nature Communications, has linked the retention of deposited ammonium and nitrate to the strength of the forest carbon sink. But the vault does not hold forever. Over the course of the study, accumulation and recovery of the labeled nitrogen in plant pools steadily increased while soil recovery declined—a clear signature of substantial redistribution of deposited nitrogen from the soil into the living biomass.

This shifting balance carries implications that ripple far beyond a single larch stand. Global nitrogen deposition has risen sharply over the past century, particularly across Asia, and models of future forest carbon sequestration depend heavily on assumptions about where deposited nitrogen goes. If soils initially lock up most incoming nitrogen but gradually release it to trees, then the timescale of observation matters enormously: a snapshot taken weeks after deposition tells a very different story than one taken months or years later. The study’s multi-pool, multi-stage design captures exactly this temporal evolution, which is why its authors argue that long-term deposition reshapes not just how much nitrogen trees use, but the relative use of different nitrogen forms and the long-term fate of exogenous nitrogen across the whole plant–soil system.

The work also speaks to a long-running debate in forest ecology. Classic experiments in the 1990s suggested that conifer roots discriminate strongly against nitrate, implying that boreal and temperate conifers rely almost exclusively on ammonium. More recent studies, including work showing that mature conifers can assimilate nitrate as efficiently as ammonium in several plantation settings, have chipped away at that dogma. The new larch data land squarely in the revisionist camp: nitrate is not merely tolerated by these trees, it is preferentially exported to the canopy over time, particularly when nitrogen supply is elevated. The physiological machinery for nitrate uptake, transport, and signaling appears fully operational in this boreal species, and chronic deposition may even upregulate it.

For a warming world, the timing could not be more relevant. Boreal forests store an enormous fraction of terrestrial carbon, and their response to nitrogen deposition is woven into every major Earth system model. By demonstrating that deposited ammonium and nitrate follow distinct pathways—rapid root capture for ammonium, delayed canopy delivery for nitrate—and that years of enrichment reroute nitrogen from soil sinks into wood and leaves, the study provides the kind of mechanistic detail that modelers need to predict how much anthropogenic nitrogen will actually boost carbon sequestration, and how much will simply cycle through soils and back into the atmosphere. The larch forests of northeastern China, it turns out, are not passive sponges for pollution. They are active accountants, balancing a ledger of two very different currencies and deciding, season by season, where every atom should go.

Subject of Research: Fate of ammonium- and nitrate-derived nitrogen in a nitrogen-enriched boreal forest traced with 15N labeling

Article Title: Long-term nitrogen addition alters the uptake, transport, and fate of ammonium- and nitrate-derived nitrogen in a boreal forest

Article References: Zou, E., Wang, M., Liu, G., Huang, B., Yin, L., Liang, C., Xing, Y., Wang, X., & Wang, Q. (2026). Long-term nitrogen addition alters the uptake, transport, and fate of ammonium- and nitrate-derived nitrogen in a boreal forest. Plant and Soil. https://doi.org/10.1007/s11104-026-09077-3

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09077-3

Keywords: nitrogen deposition, boreal forest, Larix gmelinii, 15N tracer, ammonium, nitrate, fine roots, nitrogen uptake, plant-soil system, carbon sequestration, forest ecology, soil nitrogen

The study focused on Volkhov, home to an aluminium smelter launched in 1932 and later replaced by a fertiliser plant, and Syasstroy, where a pulp and paper mill has operated since 1928. Both enterprises were designated regional pollution hot spots in the early 1990s by the Baltic Marine Environment Protection Commission. Volkhov’s emissions were dominated by sulphur dioxide and fluoride compounds, while Syasstroy released dust, sulphur dioxide, and nitrogen oxides. By the mid-1950s, peak sulphur dioxide concentrations in Volkhov had reached roughly 750 times the currently recommended health-protective level, and local ecosystems near Syasstroy were classified as critical or even catastrophic in the 1990s.

Over the study period, emissions fell dramatically. Sulphur dioxide output at Volkhov dropped fourfold between 1988 and 2021, fluorine emissions fell fifteenfold in the early 1990s, and dust emissions were about fifty percent lower in the 2020s than in the late 1980s. At Syasstroy, dust and sulphur dioxide emissions plummeted a hundredfold in the 1990s following an abrupt production decline. The researchers documented corresponding environmental recovery: fluoride concentrations in birch leaves near Volkhov fell from a peak of 200 micrograms per gram in 1988 to 32 micrograms per gram in 2025, and the needle longevity of Norway spruce, a reliable bioindicator of pollution stress, rebounded from roughly half of background values in 1989 to normal or even above-normal levels by 2025.

Against this backdrop of dramatic environmental change, the fate of the insects was surprisingly static. Between 1988 and 2025, the team counted more than 70,000 observation units of birch-feeding herbivores, representing over 60 species grouped into 24 recognisable taxonomic units, across 27 study sites and 9,674 sampled birch trees and branches. The community included external defoliators such as geometrid moths and sawflies, leafminers from several moth families, and leafrollers. Yet when the researchers correlated insect densities with distance from the polluters across all taxonomic-unit-by-year combinations, only 8.1 percent of 383 correlations were statistically significant, barely exceeding the 5 percent expected by chance alone.

A meta-analysis of the spatial patterns revealed that only six of the twenty analysed taxonomic units increased in density near the polluters, while the remaining fourteen showed no association with pollution at all. This variation was not explained by the insects’ abundance or by their feeding guild. During the high-emission years of 1988 to 1996, overall herbivore abundance did increase with proximity to the pollution sources, but the effect size was a mere 0.10, which is considered small by conventional statistical standards. Remarkably, during the low-emission period from 1997 to 2025, abundance continued to rise near the polluters at the same rate as before, even as the emissions that supposedly caused the pattern had largely vanished.

The persistence of elevated insect densities near the towns after emissions collapsed raises a thorny question: if pollution is not driving the pattern, what is? The authors considered urbanisation as an alternative explanation, but the towns are small, and existing meta-analyses suggest urbanisation has no significant overall effect on insect herbivore abundance. The results also cast doubt on earlier syntheses. A previous meta-analysis had reported elevated herbivore abundances near industrial sites, but the authors of the new study point out that mean effect sizes based on randomly chosen years from multiyear datasets did not differ from zero, whereas single-year studies and pseudoreplicated designs produced larger effects. In other words, earlier work may have systematically overestimated the true impact of pollution on herbivorous insects.

Perhaps the most counterintuitive finding concerns plant quality and leaf damage. Larvae of the autumnal moth, Epirrita autumnata, grew 45 percent faster on birch leaves collected in 2017 from sites closest to the polluters compared with leaves from the most distant sites, with the effect reaching 78 percent near Volkhov. Yet the density of this moth did not change with pollution level, and overall foliar damage by insects near both towns was approximately half of that recorded at unpolluted sites. This decoupling between plant quality, herbivore abundance, and plant damage echoes previous reports that improved host plant quality does not necessarily translate into more insects or more defoliation, because better foliage may simply allow insects to eat less while growing faster.

The study also speaks directly to the heated debate over global insect decline. Contrary to predictions, the researchers found no evidence that birch-feeding insects declined over the 38 years, either in polluted or unpolluted sites. Overall abundance remained flat, while diversity increased substantially at both polluted and background sites. The compositional shifts that did occur were guild-specific: leafminer densities decreased over time, defoliators remained stable, and leafrollers tended to increase, a pattern consistent with data from a copper-nickel smelter at Monchegorsk some 900 kilometres to the north. The rise in diversity is most plausibly explained by climate warming, with mean ambient temperature in the St. Petersburg region climbing from 5.7 to 6.7 degrees Celsius between 1985 and 2024, allowing southern species to expand northward.

The authors caution that their findings carry important limitations. The temporal resolution of sampling was uneven across years and taxa, emission and deposition data are incomplete for earlier decades, and the observational design cannot fully disentangle the effects of pollution decline from co-occurring drivers such as climate warming. The use of recognisable taxonomic units rather than species-level identifications may also mask responses of individual species that differ in pollution sensitivity. Nevertheless, the sheer duration and spatial extent of the dataset, with roughly 85 percent of the data collected by the two authors themselves, minimises the observer biases that plague shorter studies.

The broader implications are twofold. First, the study exposes a critical weakness in bioindication: conclusions about ecosystem health depend heavily on which indicator is chosen. Pollution gradients were clearly reflected in fluoride accumulation and spruce vigour, but insect density and diversity told a different and far noisier story, and a researcher relying on a single taxon in a single year could have concluded almost anything. Second, the work challenges the generality of the view that insects are universally sensitive to environmental change and questions the role of moderate industrial pollution as a driver of insect decline, at least for herbivores. The authors describe several of their findings as ecological surprises, unexpected observations that force a re-evaluation of established views. In an era when alarming insect decline headlines dominate the news, this nearly four-decade record from the boreal forests of northwestern Russia offers a sobering reminder that nature’s responses to human pressures are rarely as simple as we predict.

Subject of Research: Long-term effects of industrial air pollution and emission decline on birch-feeding insect communities in northwestern Russia

Article Title: Weak and inconsistent associations between birch-feeding insects and pollution levels around two industrial towns during substantial emission decline (1988–2025)

Article References: Kozlov, M. V., & Zverev, V. (2026). Weak and inconsistent associations between birch-feeding insects and pollution levels around two industrial towns during substantial emission decline (1988–2025). Environmental Monitoring and Assessment, 198(11), Article 1157. https://doi.org/10.1007/s10661-026-15971-1

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15971-1

Keywords: industrial pollution, insect herbivores, birch, emission decline, ecosystem recovery, bioindicators, insect decline, leafminers, Epirrita autumnata, boreal forest, Norway spruce, long-term monitoring