Soil respiration, microbial respiration and mineralisation in soils of montane rainforests of Southern Ecuador: influence of altitude

Impacts of land use and climate change in tropical forests on the global carbon budget are of principal interest in the recent research, as these forests amount to about 48 % of the world’s forested area. Interest has been focused on lowland tropical forests mainly, but tropical montane forests occupy about 20 % of all tropical forests. Soils of tropical montane forests are frequently waterlogged and characterised by high soil organic carbon stocks. Furthermore, along altitudinal gradients, changes in stand structure and net primary production can be observed that have not been fully explained yet. As causes reduced microbial activity and nitrogen turnover in soils of tropical montane forests have been suggested. Against the background of climate change, carbon turnover mechanisms in soils of these forests are of special interest. The present study therefore aimed at determining and quantifying relevant carbon and nitrogen pools as well as nitrogen mineralisation potentials. Furthermore, size, activity, and structure of microbial biomass were characterised. The collected data was supposed to provide basic knowledge on carbon and nitrogen cycling in tropical montane forest soils. Thus, evaluation of the susceptibility of their carbon stocks for climate change as well as nitrogen and carbon limitation of microbial organic matter decomposition was possible. Field work of this study was conducted during 2003–2005 at an altitudinal transect that in- cluded five study sites between 1 050 and 3 060 m amsl. Total soil respiration was recorded biweekly over two years, the contribution of roots to total soil CO2 efflux over one year. Soils of the study sites were sampled twice and biochemical and microbial parameters were determined