A monitoring protocol for the ecohydrological effects of land use changes in tropical mountain ecosystems

Abstract:

In tropical mountain regions, the societal demands for ecosystem services has led to pressure over ecosystems that, in ocassions, may threaten the capacity of ecosystems to provide services. More specifically, global-change processes such as land use change and climate dynamics may lead to uncertainties about the stability of ecosystem functions on which services rely on. Of particular interest are the effects of land cover changes on the hydrological dynamics of the soil, that support multiple regulation and provision services, critical for a large portion of the population settled in mountain regions of the world. In this work, we present a protocol for the combined monitoring of ecohydrological, biogeochemical and sediment dynamics in a group of instrumented plots representing a typical gradient of human intervention in a tropical mountain ecosystem. Land cover categories include: a mature forest, secondary forest, early successional stage, recently abandoned agricultural field, a cattle pasture, permanent cropland, a high rotation cropland. On each plot, water fluxes from the top of the canopy to 1.5 m below soil surface are measured using a diverse array of instruments, along with measurements of sediment load in runoff waters and nutrient loads for all hydrologic compartments (measurements include Ca, Mg, K, P, NH₄, NO₃, Mn, Fe). Our preliminary results indicate that although rainfall does not vary significantly among plots, runoff generation does, with higher values ocurring in the pasture. Conversely, infiltration rates are highest in both types of forests, particularly for shallower layers of the soil. Chemical analysis indicate higher nutrient loads in runoff generating from croplands, highlighting the potential loss of soil fertility and potentially leading to eutrophication in water bodies downstream. After completion, our results will provide land managers tools to assess larger-scale effects of land use changes on the capacity of ecosystems to provide services to society.