Litter decomposition and nutrient release in Acacia mangium plantations established on degraded soils of Colombia. Several factors control the decomposition in terrestrial ecosystems such as humidity, temperature, quality of litter and microbial activity. We investigated the effects of rainfall and soil plowing prior to the establishment of Acacia mangium plantations, using the litterbag technique, during a six month period, in forests plantations in Bajo Cauca region, Colombia. The annual decomposition constants (k) of simple exponential model, oscillated between 1.24 and 1.80, meanwhile k 1 y k 2 decomposition constants of double exponential model were 0.88-1.81 and 0.58-7.01. At the end of the study, the mean residual dry matter (RDM) was 47% of the initial value for the three sites. We found a slow N, Ca and Mg release pattern from the A. mangium leaf litter, meanwhile, phosphorus (P) showed a dominant immobilization phase, suggesting its low availability in soils. Chemical leaf litter quality parameters (e.g. N and P concentrations, C/N, N/P ratios and phenols content) showed an important influence on decomposition rates. The results of this study indicated that rainfall plays an important role on the decomposition process, but not soil plowing.

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We have studied nutrient related variables such as reallocation, nutrient use efficiency (nue) and fine litter fall for three years in an oak forest Quercus humboldtii Bonpl. and also in some other forest plantations like pine, Pinus patula, and cypress, Cupressus lusitanica, in Antioquia, Colombia. Leaf litter quantities returned to the soil followed a falling sequence: oak (5313.3 kg ha -1 year -1 ) > pine (4866.5 kg ha -1 year -1 ) > cypress (2460.3 kg ha -1 year -1 ). The coniferous species showed the highest nue for the majority of elements that were examined, except for P, which reached its absolute maximum in the oak forest -where a clear reallocation of this nutrient was also recorded-, probably because of its reduced availability in these volcanic Recepción:

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Tropical forest responses to variation in water availability, which are critical for understanding and predicting the effects of climate change, depend on trait variation among trees. We quantified interspecific and intraspecific variation in 18 branch, leaf and stomatal traits for 19–72 dominant tree species along a local topographic gradient in an aseasonal Amazon terra firme forest, and tested trait relationships with tree size, elevation, and species' topographic associations. We further tested whether correlation and coordination of traits vary among trees, among species and/or among trees within species. Intraspecific trait variation was substantial and exceeded interspecific variation in 10 of 18 traits. For leaf acquisition traits, intraspecific variation was mainly related to tree topographic elevation, while most of the variation in branch, leaf and stomatal traits was related to tree size. Interspecific variation showed no clear relationships with species' habitat association. Although trait correlations and coordinations were generally maintained among trees and among species, bivariate relationships varied among trees within species, across habitat association classes and across tree size classes. Our results demonstrate the magnitude and importance of intraspecific trait variation in tropical trees, especially as related to tree size. Furthermore, these results suggest that previous findings relating interspecific variation with topographic association in seasonal forests do not necessarily generalize to aseasonal forests. Read the free Plain Language Summary for this article on the Journal blog.