竹林养分循环Ⅰ.毛竹纯林的叶凋落物及其分解

NUTRIENT CYCLING IN BAMBOO STANDS Ⅰ. LEAF LITTER AND ITS DECOMPOSITION IN PURE PHYLLOSTACHYS PUBESCENS STANDS

在我国亚热带毛竹(Phyllostachys pubescens)主要产区的四片试验地上,随机布置了21个区组90个集叶斗,持续观察3a,以研究林内叶凋落物的动态。在相同立地上,又用同样方法布置20个区组400个落叶分解袋,通过林地潜育定期采集潜育样和样袋中残留物养分含量分析等方法,研究凋落物分解时的失重速率和N、P、K、Ca、Mg等养分元素的反馈。试验结果表明,毛竹林叶凋落物量在其年变化周期中有两个高峰期,峰值的出现时间由于立地条件的不同迟早不一。第一高峰值所代表的叶凋落物量因林分的生长特性不同其占全年总量的百分数变动于17—56％之间。竹叶凋落物在分解时其失重速率在初始期变化较快,但经20周林地潜育后渐趋稳定;养分的反馈情况因元素的不同而异,一些大量元素在其向土壤释放前于凋落物分解后的残留物中先有一个累积阶段。

The dynamics of leaf litter in timber stands of Phyllostachys pubescens was studied in four locations in southern China. Ninety litter traps in twenty one blocks and four hundred litter decomposition bags in another twenty blocks were set up and continuously monitored over three years. Loss of weight as well as leaching of N, P, K, Ca, Mg from the litter was recorded by periodic field collections and laboratory analysis.Results indicate that there are two peaks though the dates for these varied with the geographic locations of the stands. Litter fall during the first peak was about 80% of the annual fall. Weight loss of litter was rapid initially, stablising after twenty weeks. Nutrient release differed from element to element and seemed to be released into the soil after an initial accumulation stage.