Tropical high elevations harbor a unique alpine ecosystem with a yearlong growing season low seasonality and large daily oscillations of temperature and moisture. The ecosystems on the wet alpine areas of the northern Andes (Páramos) provide water for nearly 50% of the population and are important carbon reservoirs. However, temperatures at high elevations are raising faster than any other place in the tropics and we have little insight into how the increments in temperature are affecting the functioning of tropical alpine ecosystems. Here, we studied the patterns of carbon dynamics on soil and vegetation in two sites across an elevation gradient from 2500 to 4350 m a.s.l. from the treeline to the upper limit of the vegetation in Colombia. Our overarching question was to understand how recent changes in climate are affecting the functioning of the páramo. The two sites have contrasting environmental settings: dry vs wet and mineral vs organic soil. We monitored tree carbon dynamics, shrub and herbaceous plant production, litter production and decomposition rates, litter and soil CO2 efflux rates, bulk Soil Organic Carbon (SOC) and SOC content on the first 20 cm.
Our results show a constant rate of tree growth, with tree net primary production affected by high mortality rates during “El Niño” events. The annual variation in climate had a direct effect on production rates of non-woody plants affecting litter production and transfer of organic matter to the soil. Bulk SOC was different between the two sites with values ranging from 112 Mg ha-1 in the wetter sites to 40 Mg ha-1 at the drier sites. Soil CO2 efflux had a close relationship with elevation (mean annual temperature) and with bulk SOC. Litter CO2 efflux and litter decomposition rates showed faster rates of decomposition at lower elevations. Our results showed that bulk SOC, biomass stocks, and litter decomposition rates were influenced by site characteristics (soil and climate). Weather, relative SOC concentration and production during the previous season had an effect on the rates of soil and litter CO2. Our observations highlight the impact that recent changes in climate had on the dynamics of high elevation ecosystems and the possible trajectories that carbon cycling in this ecosystems may follow in the future under warmer climates. This research is the result of a close collaboration between governmental organizations and academia for 10 continuous years.