The study, published in Neotropical Biology and Conservation, is the first anywhere to examine how silvopastoral practices affect stream water quality. Silvopastoralism is a form of agroforestry that embeds trees into animal pastures, and previous work has shown it improves soil quality, increases shade and fodder for cattle, boosts carbon storage, and provides commercial products for landowners. What remained unknown was whether those benefits extend to the streams that drain the pastures. To find out, the team turned to an unusual but powerful set of witnesses: the aquatic macroinvertebrates living on the stream bottoms.

Macroinvertebrates are classic biological indicators of stream condition. Water chemistry offers a snapshot of the immediate state of a stream, but the insects that spend weeks or months in the water integrate habitat changes over time. Pollution-sensitive taxa such as mayflies, stoneflies, and caddisflies disappear quickly when streams degrade, while tolerant groups such as true flies thrive. By calculating the percent EPT, the percent Diptera, the percent Odonata, taxonomic richness, abundance, and the Shannon Diversity Index at each site, the researchers could score the long-term biological state of each farm’s streams.

The five farms surveyed all participate in the Environmental Leadership and Training Initiative, a program created by the Forest School at the Yale School of the Environment that mentors local landowners in Panama, Colombia, Brazil, the Philippines, and Indonesia to increase forest cover through agroforestry. Each farm contained a mix of pasture, forestry plantations, home gardens, riparian forests, and live fences. During the dry season, between 14 and 18 March 2022, the team selected four stream sections per farm and sampled comparable pools, since low water flow made riffles inconsistent. All sites had primarily sandy or silty bottoms with little cobble.

At each site, the researchers recorded pH and temperature with a combination sensor and tested for fecal coliform bacteria with a field kit. Then came the invertebrate work: disturbing the stream substrate for ten seconds, three times per site, and collecting displaced insects with a 500-micrometer sieve. The animals were washed into a tub, sorted morphologically in an ice cube tray, identified to order, and returned to the stream. Crustaceans were excluded. In total, 852 invertebrates across thirteen orders were identified, with true flies the most abundant group at 358 individuals, followed by mayflies at 189.

The pattern across farms was striking. At farm SP4, where cattle had been excluded from two sample sites, the community was dominated by sensitive taxa: the highest percent Odonata at 16.1 percent, the highest EPT index at 55.6 percent, and the lowest percent Diptera at 7.7 percent. Farm SP3, the largest and most isolated from forest patches, showed the opposite: the lowest percent Odonata at 3.2 percent, the lowest EPT at 12.2 percent, and the highest percent Diptera at 58.7 percent. Shannon diversity and richness peaked at farm SP5, which also stored the most carbon, with 138.4 megagrams of carbon per hectare in riparian areas and 80.4 across the whole farm.

Fecal coliform bacteria were present in every sample, a reminder that cattle manure enters these waterways across the landscape. Yet the physicochemical readings were remarkably consistent: pH ranged narrowly from 6.93 to 7.18, water temperatures from 24.4 to 26.4 degrees Celsius, and canopy cover from 52.83 to 84.75 percent. The biological metrics told a more nuanced story than the chemistry did, which is precisely why the researchers argue that combining both approaches is essential for a comprehensive stream assessment.

When the team ran single linear regressions linking stream metrics to landscape and habitat variables, several relationships emerged. The EPT index rose significantly with live fence connectivity, which explained about 21.5 percent of its variation. Shannon diversity increased significantly with both total farm carbon and riparian area carbon. The EPT index and the EPT index without the pollution-tolerant netspinning caddisflies both rose significantly with riparian area carbon. Notably, the variables the researchers had originally predicted to matter most, riparian area size and distance to the closest forest patch, did not significantly influence water quality in the analysis.

The authors propose that riparian tree carbon may serve as a proxy for riparian area quality rather than quantity. More trees and larger trees mean more aboveground biomass, deeper root systems, and greater capacity to absorb excess nutrients and stabilize stream banks. Live fences, whose carbon is mostly stored below ground, may soak up runoff before it reaches the streams. This would explain why the quality of the riparian vegetation, measured as carbon, predicted stream condition better than the width or total area of the riparian corridor did.

The findings come with caveats. Five farms during one dry season is a small sample, and the researchers emphasize that additional research is needed before drawing firm conclusions. Livestock access likely matters too: at the two SP4 sites where cattle were excluded, the team anecdotally observed greater within-order diversity, though they caution this may have been coincidental. Still, the study provides the first preliminary evidence that implementing agroforestry practices such as silvopastoralism could increase stream condition in the cattle pastures of dry tropical regions, and it suggests that increasing tree cover in agricultural landscapes may be beneficial to streams even when the forest survives only as fragments along the water.

Subject of Research: A preliminary study of five Panamanian silvopastoral farms finds that stream macroinvertebrate diversity and pollution-sensitive taxa rise with riparian tree carbon storage.

Article Title: A preliminary assessment of water quality in silvopastoral systems of Panama’s dry tropical forest

Article References: Portmann, J. M., Davenport, G. H., Starinchak, B. H., & Griscom, H. P. (2024). A preliminary assessment of water quality in silvopastoral systems of Panama’s dry tropical forest. Neotropical Biology and Conservation, 19(2), 173-183. https://doi.org/10.3897/neotropical.19.e111865

Image Credits: AI Generated

DOI: 10.3897/neotropical.19.e111865

Keywords: silvopastoral systems, Panama, dry tropical forest, water quality, aquatic macroinvertebrates, riparian carbon, agroforestry, EPT index, live fences, Azuero Peninsula, stream health, cattle pastures

The research team, led by Julio Henrique Germano De Souza of the University of Santiago de Compostela and the Instituto Politécnico de Bragança, together with colleagues in Spain, Portugal and Brazil, examined soil carbon and nitrogen dynamics in two oak-based silvopastoral systems within Montesinho Natural Park. One system was dominated by Quercus pyrenaica, the Galician-Portuguese deciduous oak, and the other by Quercus rotundifolia, the evergreen oak characteristic of Mediterranean woodlands. Both habitats are listed as of Community interest under the EU Habitats Directive and have developed naturally, without silvicultural intervention, while occasionally hosting extensive grazing by goats and sheep.

Soil organic carbon is one of the largest carbon reservoirs in the Earth system, and understanding how it responds to management is essential for evaluating the climate mitigation potential of grazing lands. Yet the impact of grazing on carbon distribution in Mediterranean oak silvopastoral soils has remained poorly understood, with most previous studies focusing on permanent pastures, intensive agricultural systems, or forests evaluated in isolation. Integrated systems, where trees, shrubs, herbaceous plants and pastoral management interact simultaneously, have been relatively understudied, hindering understanding of the mechanisms that regulate soil carbon dynamics and stability in these environments.

To fill this gap, the researchers collected soil samples at depths of 0 to 10 centimeters and 10 to 30 centimeters, both before grazing cycles in June 2023 and after grazing in June 2025. The grazed plots hosted distinctly different livestock regimes. At the Q. rotundifolia site, a flock of 25 late-gestation Preta de Montesinho goats grazed one plot for 15 consecutive days in July 2024, a low-intensity, short-duration treatment. At the Q. pyrenaica site, 220 pregnant Churra Galega Bragançana ewes grazed for a total of 55 non-consecutive days between May and October 2024, representing higher grazing intensity. The animals were gathered at night due to the presence of wolves in the area, a detail that underscores the wild character of this mountain landscape.

The technical approach was rigorous. After air drying and sieving, the whole soil was physically fractionated by wet sieving into three particle-size fractions: sand (250 to 2000 micrometers), silt (53 to 250 micrometers) and clay (less than 53 micrometers). This slaking-based procedure breaks apart water-unstable aggregates, leaving water-stable aggregates for analysis, and thereby distinguishes carbon that is physically protected within macroaggregates from carbon associated with finer, more organomineral-stabilized pools. Carbon concentrations were measured with a LECO elemental analyzer, and bulk density measurements allowed the team to convert concentrations into carbon stocks per hectare. Multivariate ordination by principal component analysis and generalized linear mixed models were then used to evaluate the effects of stand-forming tree species, presence of grazing, and soil depth.

The results were striking. Soil carbon and nitrogen were significantly influenced by stand type and soil depth, whereas grazing had no significant effect on any fraction analyzed. Under Q. pyrenaica, soil organic carbon in the surface layer reached 35.00 grams per kilogram, compared with 24.6 grams per kilogram under Q. rotundifolia. Carbon stocks ranged from 30.42 megagrams per hectare under Q. pyrenaica to 13.25 megagrams per hectare under Q. rotundifolia across the soil profile. Nitrogen followed the same pattern, with total values reaching 2.28 grams per kilogram under Q. pyrenaica against roughly 0.52 grams per kilogram under Q. rotundifolia. In every case, the sand fraction concentrated most of the carbon and nitrogen, consistent with the global literature showing that macroaggregates account for the majority of variation in total soil carbon stocks.

The ordination analysis reinforced this picture. The first two principal components explained 86.8 percent of the total variance in ungrazed plots, with the first axis representing a clear gradient of soil organic matter accumulation driven by carbon stocks, carbon content and nitrogen content, while bulk density was negatively associated with it. After grazing, the ordination structure remained essentially unchanged, with samples separating along the same vegetation-driven gradient. No substantial temporal shifts were detected in the ungrazed control sites either. The stability of the pattern between sampling periods indicates that grazing, under the conditions evaluated, did not substantially alter the multivariate structure of soil properties.

Why would tree species matter so much? The researchers point to intrinsic attributes of the habitat, including greater litterfall and litter quality, root architecture, and the intensity of biogeochemical cycling. Q. pyrenaica is a deciduous oak that sheds its leaves annually, delivering a substantial pulse of organic matter to the soil surface, while its soils, classified as Umbric Leptosols, feature a dark, humic surface horizon. Q. rotundifolia, by contrast, is evergreen, and its plots had higher bulk density and lower nutrient levels. The strong vertical stratification, with carbon declining markedly in the 10 to 30 centimeter layer, particularly under Q. rotundifolia, highlights the importance of surface organic inputs and the biological activity concentrated in the upper horizons.

The absence of a grazing effect on the silt and clay fractions, which offer the greatest physical and chemical protection of organic matter, suggests that the management strategy did not encourage sufficient aggregate restructuring to affect carbon stabilization in the fine pools. This finding is consistent with a growing body of evidence that moderate or rotational grazing does not necessarily result in losses of carbon associated with stable aggregates, and that silvopastoral systems are structurally resilient to moderate disturbances, maintaining the integrity of soil aggregates and biogeochemical functionality. The balance between organic matter inputs from plant residues and animal excreta and potential losses from trampling or biomass removal may simply result in neutral net effects under extensive management.

The authors are careful to note caveats. The study lacked habitat replication, so differences between the two oak systems should be interpreted cautiously, as site-specific factors may also have contributed. The assessment period was relatively short, and the observed stability of soil carbon stocks should not be read as direct evidence of long-term carbon sequestration. Nevertheless, the implications are significant for the region, where grazing plays an important socio-economic role for small and medium-sized family farms, contributing to income generation, rural population retention and the preservation of traditional knowledge. The findings suggest that well-managed extensive grazing can be compatible with surface carbon conservation, and that tree species composition, particularly the dominance of Q. pyrenaica, is the key lever controlling soil carbon and nitrogen dynamics in Mediterranean silvopastoral systems. Long-term monitoring will be needed to determine whether these systems can consistently sustain their carbon sequestration potential and their contribution to climate change mitigation.

Subject of Research: Distribution of soil carbon and nitrogen in Mediterranean oak silvopastoral systems under grazing

Article Title: Distribution of soil carbon and nitrogen in Mediterranean oak silvopastoral systems under grazing

Article References: De Souza, J. H. G., Difante, G. D. S., Francé, O., Mosquera-Losada, M. R., & Castro, M. (2026). Distribution of soil carbon and nitrogen in Mediterranean oak silvopastoral systems under grazing. Pastoralism: Research, Policy and Practice, 16, Article 16765. https://doi.org/10.3389/past.2026.16765

Image Credits: AI Generated

DOI: 10.3389/past.2026.16765

Keywords: soil organic carbon, silvopastoral systems, grazing, Mediterranean oak woodlands, carbon sequestration, soil nitrogen, agroforestry, Distribution, soil, carbon, nitrogen, Mediterranean

Soil is the largest carbon reservoir in terrestrial ecosystems, holding more carbon than the atmosphere and all vegetation combined. Yet when forests are converted to intensive agriculture, surface soils can lose between 30 and 75 percent of their organic carbon, releasing carbon dioxide into the atmosphere while stripping the land of the fertility that sustains crops. The Food and Agriculture Organization has identified the rebuilding of soil organic carbon as a cornerstone of climate-smart agriculture, making it essential to understand which land-use systems actually deliver carbon gains under real farm conditions.

Zamora Chinchipe, in southeastern Ecuador, provided an ideal natural laboratory. The province sits within the Ecuadorian Amazon, with a humid to sub-humid climate, mean annual temperatures between 18 and 30 degrees Celsius, and annual precipitation of roughly 1,900 to 2,100 millimeters. Its topography ranges from steep mountain terrain to inter-Andean valleys transitioning into the Amazon basin, producing an extraordinary diversity of soils and ecosystems. Those soils, however, are generally shallow, acidic, and of relatively low fertility, and they face mounting pressure from agricultural expansion and, increasingly, mining.

To capture that diversity, the research team evaluated 187 farms across six land-use types: cacao agroforestry systems, coffee agroforestry systems, cacao monocultures, natural forest, extensive pastures, and silvopastoral systems that combine trees, grass, and cattle. The farms were selected in coordination with local producer associations and spread across the cantons of Zamora, Chinchipe, Palanda, Yantzaza, Paquisha, and Centinela del Cóndor. Between 2023 and 2024, the researchers collected 187 composite soil samples from the top 20 centimeters of the profile, each built from six subsamples mixed together. Sampling locations on different farms were separated by at least five kilometers to reduce spatial dependence, and undisturbed soil cores were taken to measure bulk density, a key indicator of compaction.

The laboratory work was exhaustive. Texture was assessed with the Bouyoucos hydrometer method, pH was measured potentiometrically, and available nitrogen, phosphorus, sulfur, boron, and a suite of cations were quantified using standardized colorimetric, spectrometric, and turbidimetric procedures. Soil organic matter was determined by loss-on-ignition and converted to organic carbon using a conventional factor of 0.58, allowing carbon stocks to be expressed in megagrams per hectare. Because the data did not meet the assumptions of parametric statistics, the team relied on the non-parametric Kruskal-Wallis test with Dunn’s post hoc comparisons and Bonferroni correction, supplemented by Spearman rank correlations and a principal component analysis.

The headline result concerns carbon. Coffee agroforestry systems recorded the highest topsoil carbon stocks, averaging more than 80 megagrams per hectare, and differed significantly from most other land uses. Silvopastoral systems and pastures followed closely, while cacao monocultures registered the lowest values. When the researchers compared paired systems directly, the pattern became striking: cacao grown under shade trees stored roughly 20 percent more carbon than cacao monoculture, silvopastoral systems held about 24 percent more than treeless pastures, and forest soils carried approximately 27 percent more carbon than cacao monocultures. Forest stands themselves averaged around 69.45 megagrams of carbon per hectare in the surface layer, a figure consistent with other Amazonian studies even if somewhat below values reported elsewhere in the region.

Fertility told a parallel story. Coffee agroforestry showed the most favorable nutrient profile for nitrogen and sulfur, while cacao agroforestry stood out for calcium, magnesium, and manganese. Pastures, by contrast, generally exhibited the lowest concentrations of sulfur, calcium, and magnesium, along with lower pH values and elevated iron, a signature of acidification and nutrient depletion associated with continuous grazing, trampling, and the removal of nutrients without replenishment. The correlation analysis reinforced these patterns, revealing strong positive associations between calcium and magnesium and between pH and both bases, while carbon stocks correlated positively with nitrogen. Soil pH remained acidic everywhere, ranging from roughly 4.5 to 6.0, with the highest values in cacao agroforestry and the lowest in forest soils.

The mechanisms behind these differences are well understood in principle. Trees in agroforestry systems continuously deposit litter and organic residues, feeding nutrient cycling and raising the soil’s cation exchange capacity. Their deep root systems pump nutrients upward from lower horizons and return them to the surface, buffering acidity and improving structure. In pastures, dense grass roots do promote aggregation and can accumulate substantial carbon, with species such as Brachiaria humidicola capable of building hundreds of grams of root biomass per square meter in the top 15 centimeters. But the study’s authors caution that carbon accumulation in pastures can coexist with chemical degradation, meaning high carbon numbers alone do not guarantee soil health or long-term sustainability.

The implications extend beyond soil science. Many of the participating farms already hold organic certification, and the researchers note that agroforestry and silvopastoral systems can generate higher returns per unit of labor than full-sun monocultures, with income from timber, fruit, and other tree products helping to offset lower cacao yields. By offering viable production alternatives, tree-based systems may also reduce pressure on remaining natural forests, a critical point in a province where extractive mining is expanding. Previous work in the Ecuadorian Amazon has shown that shaded cacao systems store about 40 percent more carbon in aboveground biomass than monocultures, and the new soil data suggest the belowground benefits run in the same direction.

The authors are careful to frame their findings as associations rather than proof of causation, and they acknowledge limitations: the assessment covered only the top 20 centimeters of soil, leaving deeper carbon dynamics unmeasured, and factors such as elevation, slope, and the conventional carbon conversion factor introduce uncertainty. They call for future sampling at depths of 30 to 60 and 60 to 120 centimeters to capture the full vertical distribution of carbon. Even so, the message from Zamora Chinchipe is clear. In tropical production landscapes, keeping trees on farms is not a compromise between agriculture and the environment; it is one of the most practical strategies available for sustaining fertility, storing carbon, and building resilience in the soils on which both livelihoods and the climate depend.

Subject of Research: Effects of tree-based production systems on topsoil fertility and carbon storage in the tropical Ecuadorian Amazon

Article Title: Tree-based production systems and their relationships with topsoil fertility and carbon storage in tropical regions

Article References: Jiménez, L., Carrera, R., Fierro, N., Lasso, J., Roa, J., Ochoa, P., Loján, C., Donoso, R., & Capa-Mora, D. (2026). Tree-based production systems and their relationships with topsoil fertility and carbon storage in tropical regions. Journal of Agriculture and Food Research, Article 103350. https://doi.org/10.1016/j.jafr.2026.103350

Image Credits: AI Generated

DOI: 10.1016/j.jafr.2026.103350

Keywords: soil organic carbon, agroforestry, silvopastoral systems, cacao, coffee, Ecuadorian Amazon, soil fertility, carbon stocks, land use change, tropical soils, pasture degradation, climate-smart agriculture