模拟降水分配季节变化对南亚热带常绿阔叶林凋落物的影响

为探讨降水季节分配的变化对南亚热带常绿阔叶林凋落物的影响,在广东省鹤山国家野外生态观测站模拟干季更干(DD)和延长干季(ED)的野外降水控制实验,对森林生态系统中凋落物变化进行了分析研究。结果表明,该试验林年凋落物总量为9.24 t hm–2,在不同时期均以叶凋落物为主,约占50.7%~69.3%。DD处理显著减少了干季(10–3月)叶凋落物量(P0.01)。虽然DD处理下全年总凋落物量比对照降低了10.3%,但差异不显著。ED处理也减少了春季(4–5月)的叶和花果及总凋落物量,全年总凋落物量则比对照增加了11.3%,但ED处理对春季和全年凋落物量的影响均差异不显著。两种干旱处理对凋落物叶质量总体上影响不明显,但DD处理显著减小了火力楠(Michelia macclurei)凋落叶的木质素含量。因此,降水格局的变化可能会影响南亚热带森林土壤的碳汇能力。

Effects of Seasonal Precipitation Variation on Litter-fall in Lower Subtropical Evergreen Broad-leaved Forest

In order to understand the effects of precipitation pattern on litter-fall in lower subtropical evergreen broad-leaved forest, a field precipitation manipulation experiment at Heshan National Forest Research Station (Guangdong Province, China) was designed to simulate decreasing dry-season (October-March) and spring (April-May) rainfall and the litter-fall respones in the forest was studied. The results showed that annual litter-fall of the experimental forest was 9.24 t hm^-2, of which leaf litter was the main composition at different stages, accounting for 50.7%-69.3% of the total. The decreasing dry-season rainfall (DD) treatment significantly reduced leaf litter production (P<0.01). The whole-year litter production was also reduced by 10.3% under the DD treatment compared to the control, but not statistically significant. Decreasing spring rainfall (ED) also reduced flower-, fruit-, and leaf-litter as well as the total during the spring time, but the whole-year litter production was increased by 11.3% compared to the control. No statistically significant difference of ED effects on the spring and wholeyear litter production was found. Neither DD nor ED treatments had obvious impacts on the quality of leaf litter, but DD treatment significantly reduced lignin content in leaf litter of Michelia macclurei (P<0.05). Therefore, the changes in precipitation pattern could influence the soil carbon sink in the lower subtropical forests of China.