Dynamics of soil organic carbon in Andean high-mountain ecosystems of Bolivia

The carbon is one of the main drivers to climate change occurrence. Carbon is distributed along subsystems of the Earth: atmosphere, geosphere, hydrosphere, cryosphere, and biosphere. Carbon distribution has been varying not only as a natural process but also affected by intensive human activities in recent centuries. A recognized and largest storage of carbon is the soil, a dynamic system that respond to climate, vegetation, and use among others. The importance of soil lies in the fact that it provides ecosystem services: physical medium, habitat and biodiversity, nutrient cycling, water cycle and support habitation and human health. On top of that, soil can act as greenhouse gases (GHGs) source or sink which depends on the factors interaction. For this reason, in recent years, interest in soils as strategy to face climate change have amplified. Mitigation when soil act as a GHGs sink and adaptation when the carbon improve the soil quality. Good examples are the development of the international initiative '4 per 1000' defined in the COP21 and Land Degradation Neutrality (LDN), defined by the Parties to the UNCCD. To sum up, those initiatives aim to preserve, recover and regenerate the soil ecosystem services. In natural conditions, soils are in equilibrium, but anthropogenic activities (land use change mainly) have broken their balance. Once the equilibrium is broken, the potential of soil as GHGs emitter may increase (this research will focus on carbon). Changes in land use is a frequent activity in developing countries as Bolivia. Some studies mention that 41% of Bolivian surface suffer degradation processes (condition that make Bolivia work on LDN Plan currently). If Bolivia is divided grossly, there are two opposite ecosystems: tropical lowlands and arid/semiarid highlands. This latter, the Andes is characterized by fragile soils due to adverse climate (low and high intensity rainfall, low and high amplitude temperatures and high rate of evapotranspiration), low coverage, shallow thickness, low fertility, low water retention and reduced microbial activity. However, despite its fragility, agricultural activity is still the main economic incomes and an important population (directly and indirectly) depend on its productivity. The pressure on these soils is also stressed by climate change expressed in extreme weather events (untypical droughts, frost, and erratic precipitation). According to the facts already exposed, carbon dynamics (storage, inputs and outputs) will be studied and located in a small and typical basin of the Andes (in terms of altitude, land use, management). In a vulnerable ecosystem as the Andes, the climate resilience is essential. Subsequently, it is intended to state the soil carbon dynamics. So the research will be structured as follow: firstly, identification of main drivers (soil, climate, vegetation, and land use will be taken into account) for carbon dynamic. Secondly, as an important and more dynamic and present factor, the anthropogenic impact to soil carbon dynamics will be estimated. Thirdly, determination of soil carbon sequestration potential of Andean soils. This section will try to answer the conditions that make possible soils retain carbon. It may help to identify and propose actions of short and medium term effect. Finally, evaluate the carbon emissions in Andean regions under possible future scenarios.