Litter and fine-root production in three types of tropical premontane rain forest in SE Venezuela

We investigated the productivity of three premontane primary forest sites in an extremely nutrient-poor environment on the Guyana shield in SE Venezuela. Aboveground litter production (total 5.58; leaves 4.30 Mg ha(-1) year(-1)) was low, but comparable to other tropical forests. Due to the low nutrient status, net production of fine roots was among the highest ever reported (11.14 Mg ha(-1) year(-1)). Only 20% of fine root stock was alive, 80% consisted of necromass. Similar values were obtained for dead and living root tips. Element concentrations in fine roots (including bio- and necromass), especially Ca, were low, whereas Al concentrations were relatively high. The upper limit of average fine root lifetime was 253 days. We conclude that the high proportion of necromass was mainly caused by slow mineralisation of nutrient-poor fine roots.