Impacto de la perturbación crónica por pastoreo sobre la descomposición de la hojarasca y resiliencia de la microbiota edáfica al cambio climático en bosques tropicales secos

The importance of forests and the need for forest restoration is now internationally recognised and one of the main United Nations Environmental Program goals. Seasonally dry tropical forests (SDTF) account for more than half of the forest cover across the tropics and represent one of the ecosystems most threatened by human activities. As a result of long-lasting exploitation of these forests, many are suffering from chronic disturbance that is degrading and compromising forest regeneration. One of the main chronic disturbances in SDTF is livestock grazing, which has worsened in recent years because of increasing drought periods. Indeed, the interacting effects of climatic and anthropogenic disturbances on SDTF are highly unpredictable and more research is urgently needed. Here, we aim to study how chronic disturbance impacts the responses of soil processes, litter decomposition, and soil biota to climate change and particularly drought. Using a disturbance gradient, we aim to assess the effect of goat grazing on litter decomposition and the resistance and resilience of soil microbiota to drought as well as the impact on the ecosystem services they provide. In particular, we aim to investigate how chronic disturbance is affecting: (1) forest microclimate and soil hydraulic and physicochemical properties with a focus on soil structure, (2) litter decomposition processes including the potential role of abiotic processes such as photodegradation and its interaction with microbial decomposition, (3) the structural and functional diversity of soil microbial communities and in turn, the resistance and resilience of soil microbiome, (4) the potential consequences of changes in soil microbiome for C and N cycling, (5) main ecosystem services (e.g., climate change mitigation and soil fertility) provided by soil microbiota. Finally, (6) we will model the consequences of changes in soil microbiota and soil processes for ecosystem service provision. We count with an excellent experimental set up in southern Ecuador (one of the main countries where SDTF are found), consisting of five stages of forest degradation as a result of chronic disturbance by goat grazing. We will set up a litter decomposition experiment along the degradation gradient to investigate the role of abiotic and biotic decomposition processes. We will measure soil microbial functional and taxonomic diversity in two different seasons (wet and dry) in two consecutive years to investigate the resilience and resistance of soil biota to drought periods. Moreover, we will carry out several experiments in mesocosms manipulating temperature and water simulating extreme climate events to assess their impact on soil functionality and greenhouse emissions. We expect that the results from HUMBOLDT project will generate essential knowledge to develop strategies that can help regenerate these degraded forests while mitigating the impact of climate change. As a result, we expect a high scientific impact since HUMBOLDT tackles innovative processes such as the potential contribution of abiotic litter decomposition processes and the possible interaction between forest degradation and vulnerability of soil biota to climate change. Moreover, HUMBOLDT has a marked interdisciplinary approach involving a great variety of analytical and modelling techniques. Finally, we have devoted an entire WP for the transfer of project results to the society and local communities.