鼎湖山锥栗粗木质残体的分解和元素动态

Decomposition and Nutrient Release from Coarse Woody Debris of Castanopsis chinensis in Dinghushan Forest Ecosystem

摘要:

选取锥栗（Castanopsis chinensis）粗木质残体（coarse woody debris，CWD）的3个径级（径级1—3分别为5—10cm，10—20cm和20—30cm），并且将每个径级的锥栗粗木质残体分为Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ5个分解阶段。通过测定锥栗粗木质残体3个径级的Ⅰ-Ⅲ阶段的7种化学元素（C、N、P、K、Ca、Na、Mg）的浓度和CWD密度变化来研究其分解过程中的元素动态、分解速率及其分解过程中基质质量的变化。到分解阶段Ⅲ时，3个径级的重量与原来相比分别损失了36％、48％和43％。元素N、P、Mg、Ca、Na的浓度升高。元素N的累积可能和锥栗粗木质残体中寄生着固氮细菌和真菌有关。元素P、Mg、Ca、Na的浓度升高则可能是由于这4个元素因淋溶流失的速度小于锥栗粗木质残体质量的损失速度，造成元素积聚，元素C、K的浓度降低。N／P比值是较好的分解指示指标。虽然存在元素的净释放，但是由于C和其它主要元素的释放速率较慢，因而锥栗粗木质残体是森林中重要的C库和长期的元素来源。

Abstract:

The nutrient dynamics during the decomposition of coarse woody debris （CWD） with different diameters from Castanopsis chinensis in Dinghushan monsoon evergreen broadleaved forest, Guangdong Province, was examined by sampling debris that were at various decaying stages. Changes in debris density were measured in debris with diameters of 5-10 cm （grade 1）, 10-20 cm （grade 2） and 20-30 cm （grade 3） to study the composition rates, nutrient dynamics, and substrate quality during decay. Up to decay stage HI, CWD grades 1, 2, and 3 lost its weight and carbon by 36%, 48% and 43%, and 33%, 47% and 19%, respectively. The concentrations of N, P, Mg, Ca and Na increased while C and K decreased. The increase in element content was likely due to lower leaching rate campared to the loss of CWD mass. N accumulation in CWD might be caused by nitrogen fixing bacteria and fungi. The change in ratio of N to P showed a good decomposition indicator in CWD. The release of carbon and other main nutrients was slow, thus CWD exhibited an important long-term carbon sink in the forest.