摘 要(英文):Succession is a hotspot of ecology all the times, and energy plays an essential role in life activity. The objective of this study is to determine the allocation pattern of caloric values in some dominant species of the secondary forests that were evolved from deforestation of local tropical rain forests in Xishuangbanna and subtropical forests on the Ailao Mountains, Southwest China.
The four communities in Xishuangbanna were Trema orientalis forest, Mallotus paniculatus forest, Macaranga denticulata forest and Millettia leptobotrya forest, which were 2-, 4-, 6- and > 15 years old respectively. Three plots of 20 m 20 m were established in each of the 4 forest types, in which species names, DBH of all trees whose diameters were over 3 cm were measured. Caloric values of 17 dominant tree species were observed. In the Ailao Mountains, we sampled 5 pioneer trees based on the data from previous investigates. Five sample trees comprised of one small, three intermediate and one large-sized tree were investigated for each dominant species. The sampled parts included foliages, branches, stems and roots. The caloric values of three replications for each sample part were measured with SDCM-IIIa oxygen bomb calorimeter, with error under100 J • g-1. Differences were tested by the t - Test. The results show that:
1. Total number of species and species richness increased with forest ages. With the mature of communities, there should be more species diversity to abet energy dissipation.
2. The mean caloric values of T. orientalis forest, M. paniculatus forest, M. denticulata forest and M. leptobotrya forest were 19182.11, 19474.81, 19551.38 and 19445.95 J•g-1 respectively. When the biomass of the community is low, the ecosystem increases the accumulation of energy though biomass growth, so the caloric values of the pioneer trees are low. But as the organic structures build up, the ecosystem augments the fixation efficiency of the energy, and then the caloric values are enhanced.
3. The caloric values of the climax tree species in Xishuangbanna were greater than those of the pioneer. However, the differences between foliages were significant, and the differences between branches, stems, roots and the average were not significant.
4. The caloric values of different parts were ranked as: foliage > stem or branch > root at the average level, although Trema orientalis, Vitex quinata, Aporusa yunnanensis showed lower caloric value in foliage.
5. The caloric values of pioneer species in the Ailao Mountains were higher than the climax, the reason need more investigates.
6. The caloric values of pioneer species in rainy season in the Ailao Mountains were lower than those in dry season. Biomass increased slowly in dry season, so caloric values were higher; Plants grew fast in rainy season, and caloric value decreased.
7. The caloric values of pioneer species in the Ailao Mountains were higher than those in Xishuangbnana.
8. Protein content of pioneer trees in Xishuangbanna was significantly higher than that of the climax trees, and the cellulose content of pioneer trees was significant lower than that of the climax trees. In the Ailao Mountains, the cellulose content of pioneer trees was significant lower than that of the climax trees. The contents of fat and cellulose were significantly higher in the Ailao Mountains than in Xishuangbanna.