Abstract:Extensive areas of the Amazon River basin are underlain by soils with shallow impeding horizons. To evaluate how the distinctive hydraulic properties of soil with a plinthic horizon under forest and pasture affect water storage and runoff process, two first-order catchments drained by ephemeral streams were instrumental in eastern Amazonia. Field measurements showed the presence of a strong vertical gradient of saturated hydraulic conductivity, which declines to extremely low values (median <1 mm h 1 ) at the plinthite layer, limiting both vertical and lateral flow, and keeping the soil water content close to saturation throughout most of the wet season. This scenario led to the frequent occurrence of saturation overland flow (SOF) under both land covers and very small amounts of shallow sub-surface flow (SSF). The annual flow in the exit channels was 3Ð2% of throughfall (2Ð7% of annual rainfall) under forest and 17% of annual rainfall for pasture, while the frequency of days with overland flow (OVF) was about 60% of the days for both catchments during the wet season. In the forest, all OVF originated from saturated areas, while in the pasture, infiltration-excess OVF accounted for 40% of the runoff and SOF accounted for 55% of runoff. The higher flow generation in the pasture could be explained by the higher water storage compared to the forest, promoting more frequent SOF, and additionally by the lower hydraulic conductivity near the surface favouring the occurrence of Horton overland flow (HOF).

[1] Deforestation is altering small catchment hydrobiogeochemistry in the Amazon. To evaluate land use change effects on water chemistry and other measures of water quality, five low-order streams were studied in the eastern Amazon from April 2003 to October 2005. It was hypothesized that 1) cation loads would increase downstream as the area of cleared forest increased, particularly during the wet season, 2) increasing forest to pasture conversion would increase total solute loads, and 3) nitrate concentrations, which are high under mature forest, would decline with conversion to pasture, but would increase with increasing row crop agriculture. The first hypothesis was generally not supported, as there was no consistent observed increase in conductivity or cation concentrations from upstream to downstream. However, elevated wet-season measures of conductivity, alkalinity, and turbidity indicated increased wet season surface runoff of these constituents, with seasonal changes largest in the watersheds that had experienced the most deforestation. The second hypothesis was supported when all data were pooled in a mixed-model analysis such that conductivity declined with increasing percent forest or increased with increasing percent pasture; however, similar correlations with cations were not significant. The third hypothesis was supported, with decreasing nitrate concentrations observed as forest cover declined and pasture cover increased from upstream to downstream positions, except where crops were grown near the stream, which was associated with increased stream nitrate. In addition, stream temperature, dissolved oxygen, and pH were negatively correlated with percent forest cover while sodium, chloride, and turbidity also increased with percent crop cover. Turbidity, temperature, pH, and dissolved oxygen appear to be the simplest and most indicative parameters for detecting effects of land-use change on water quality in this region.

-Human pressure on ecosystems has undesirable impacts on human well-being. After the Millennium Project, much interdisciplinary research has been developed worldwide aiming to understand these impacts on ecosystem flows and processes, and to learn about the costs and the benefits of ecosystem services for production. Soil provides many ecosystem services, since its multi-functionality is the basis for food production, water filtration, nutrient cycling, and other goods essential to life. This article presents the main concepts and classifications of soil ecosystem services and of its functions; the indicators and the methods for assessment, modeling, and valuation of ecosystem services; some recent applications to assess and evaluate impacts of agricultural management practices on soil ecosystem services; as well as challenges and opportunities for research and for development of public policies related to agro-environmental sustainability in Brazil. Although the role of soil in supplying ecosystem services is yet undervalued, scientists are gradually recognizing soil processes and functions as fundamental to assess ecosystem services and the effects of land use and management on them. Interdisciplinary approaches to integrate science and public policies are necessary to build governance based on ecosystem services.Index terms: economic valuation, environmental services, soil function, soil indicators, soil management, public policy, soil quality. Panorama atual e potencial de aplicação da abordagem dos serviços ecossistêmicos do solo no BrasilResumo -A pressão humana sobre os serviços ecossistêmicos tem resultado em impactos indesejáveis sobre o bem-estar humano. Com o Projeto Millennium, várias pesquisas interdisciplinares têm sido desenvolvidas em todo o mundo com o objetivo de entender esses impactos sobre os fluxos e os processos dos ecossistemas e internalizar os custos e os benefícios dos serviços ecossistêmicos para a produção. O solo fornece muitos serviços ecossistêmicos, uma vez que sua multifuncionalidade é a base para a produção de alimentos, filtração de água, ciclagem de nutrientes e outros bens essenciais à vida. Este artigo apresenta os principais conceitos e classificações dos serviços ecossistêmicos do solo e de suas funções; os indicadores e os métodos de avaliação, modelagem e valoração dos serviços ecossistêmicos; algumas aplicações recentes para avaliar impactos de práticas de manejo agrícola sobre os serviços ecossistêmicos do solo; bem como os desafios e as oportunidades para a pesquisa e para o desenvolvimento de políticas públicas relacionadas à sustentabilidade agroambiental no Brasil. Apesar de o papel do solo para prestação de serviços ecossistêmicos ainda ser subestimado, os cientistas têm gradualmente reconhecido os processos e as funções do solo como fundamentais para avaliar os serviços ecossistêmicos e os efeitos do uso e manejo da terra sobre eles. Abordagens interdisciplinares que integrem ciência e políticas públicas são necessárias para construir uma governança com...

Soil ecosystem service (SES) approaches evidence the importance of soil for human well-being, contribute to improving dialogue between science and decision-making and encourage the translation of scientific results into public policies. Herein, through systematic review, we assess the state of the art of SES approaches in tropical regions. Through this review, 41 publications were identified; while most of these studies considered SES, a lack of a consistent framework to define SES was apparent. Most studies measured soil natural capital and processes, while only three studies undertook monetary valuation. Although the number of publications increased (from 1 to 41), between 2001 and 2019, the total number of publications for tropical regions is still small. Countries with the largest number of publications were Brazil ( n = 8), Colombia ( n = 6) and Mexico ( n = 4). This observation emphasizes an important knowledge gap pertaining to SES approaches and their link to tropical regions. With global momentum behind SES approaches, there is an opportunity to integrate SES approaches into policy and practice in tropical regions. The use of SES evaluation tools in tropical regions could transform how land use decisions are informed, mitigating soil degradation and protecting the ecosystems that soil underpins.