Struktur und Dynamik des Feinwurzelsystems von tropischen Bergwäldern in Abhängigkeit von der Meereshöhe in Südecuador

Abstract

In a tropical montane rainforest in the South of Ecuador the effect of increasing altitude on structure and dynamics of fine root system was assessed. Fine root bio- and necromass, morphology, spatial distribution and seasonal dynamics have been studied on three sites at 1890, 2380 and 3060 m a.s.l. respectively.An increase in fine root mass with increasing elevation was observed in the organic layer as well as in the first 20 cm of the mineral soil. Along the elevation gradient fine root biomass increased from 393 to 978 g m-2, while fine root necromass showed an increase from 640 to 2398 g m-2. Soil water content in the research stands ranged between 20 and 30 %. Fine root biomass/necromass ratio showed an overall large variation. Temporal variability in fine root mass did not correspond with climatic seasonal pattern. With rising elevation fine root production increased from 676 to 2193 g m-2 and fine root litter production from 523 to 2058 g m-2. Life span of fine roots ranged between 0.75 and 0.44 years. Fine root turnover took the same time approximately. Decomposition experiments with litter bags showed that decomposition got slower with increasing elevation. Both specific root area and specific leaf area decreased, while root area index showed an increase with rising elevation. However tree height and leaf litter production declined with increasing elevation.Along the elevational gradient a significant relationship was found between fine root mass and leaf litter production. Factors influencing specific root area, fine root production and fine root mortality are altitude, mean air temperature, nitrogen content, specific leaf area, specific root area, tree stem height and diameter at breast height. Precipitation showed a negativ correlation with fine root turnover and life span.