Coarse woody debris in a montane forest in Ecuador: mass, C and nutrient stock, and turnover

Coarse woody debris (CWD) in forests temporarily stores C and nutrients and thus contributes to their cycling. To assess the contribution of CWD to element cycles, its element stock and turnover time have to be known. Therefore. we (i) determined the mass and the C and nutrient concentrations of CWD in a montane forest in the south Ecuadorian Andes. (ii) assessed how these properties of CWD related to topographic position and stand properties, and (iii) estimated the turnover rates by using a regression equation of the turnover rate of CWD on temperature from the literature. The study area covers 9 ha and is located at 1900-2180 m above sea level. We selected sixteen 400 m(2)-large plots and determined all fallen and standing dead wood with a diameter > 0.1 m. The average mass of CWD was 9.1 t ha(-1); 40% of the CWD mass did not have soil contact. The individual CWD masses were highly variable among the plots (0.4-23 t ha(-1)). We did not detect any significant relationship beween topographic position or stand properties and mass and C and nutrient stock of CWD. The CWD contributed 4% to the total C stock and < 1.8% to the nutrient stock in aboveground dead biomass (i.e. CWD + organic layer including Oi, Oe, and Oa horizons (taken from a previous publication)). The estimated mean decomposition constant of CWD was 0.09 year(-1) The annual nutrient release from CWD contributed at most 1.5% to the totally plant-available nutrients in the forest soil (nutrient input with throughfall and stemflow + release from organic layer (taken from previous publications) + release from CWD). Our results demonstrate that in the studied montane forest the CWD contribution to C stock and nutrient release is small. This might be specific for forests with a thick organic layer. (C) 2004 Elsevier B.V. All rights reserved.