Abstract:

Aims Our objective was to estimate the gross caloric values (GCVs) for two vegetation types and examine the differences.
Methods Samples of fresh leaves were collected from 10 dominant species in mid-montane moist evergreen broad-leaved forest in Ailao Mountain and 11 dominant species in tropical seasonal rain forest in Xishuangbanna. Leaf litter samples also were collected and divided into fresh litter layer (L layer) and fermentation layer (F layer). Samples were dried to constant weight at 60℃, and GCV of each sample was measured by a PARR1261 oxygenic bomb calorimeter.
Important findings There was a wide range of GCVs in fresh leaves and litter layers in both forests. The GCVs in fresh leaves were higher than in leaf litter for all but six species, with the differences between fresh leaves and leaf litter dependent on species characteristics. In both forests, species with higher GCVs in fresh leaves also had higher GCVs in leaf litter. The difference of GCV between L layer and F layer samples was significantly higher in Xishuangbanna than in Ailao Mountain, suggesting that litter layer decomposes more rapidly in Xishuangbanna. The ranking of mean GCVs from the same stand was fresh leaves > leaf litters > L layer litters > F layer litters. Mean GCVs in Ailao Mountain were consistently higher than those in Xishuangbanna, indicating that GCV was correlated with geographical factors. Forest GCVs are higher at high altitude, high latitude evergreen broad-leaved forest than in low altitude, low latitude tropical seasonal rain forest.

Key words: dominant species, gross caloric value, fresh leaf, leaf litter, litter layer, energy ecology