川西高寒森林岷江冷杉凋落叶分解过程中镉和铬动态特征

The Dynamic Features of Cadmium and Chromium in Foliar Litter of Abies faxoniana during Decomposition in the Alpine Forest of Western Sichuan

为了解高寒森林凋落物分解过程中重金属释放规律,采用凋落物袋法,于2012年11月至2014年10月在川西高寒森林研究了该区域建群种岷江冷杉凋落叶在不同分解关键时期(雪被形成期、覆盖期、融化期和生长季节)镉和铬含量及分解速率特征.结果表明:岷江冷杉凋落叶中镉和铬初始含量分别为(59.7±5.7)μg/kg和(3.81±0.262)mg/kg,而分解2年后,其含量分别增加了3.0倍和87.0%.岷江冷杉凋落叶中镉和铬含量均在雪被形成期和生长季节有较大程度的增加,表明大气湿沉降可能向地表输入一定量的镉和铬.同时镉和铬含量在雪被覆盖期和融化期显著降低,表明川西高寒森林不同雪被覆盖时期,由雪被消融产生的水热条件的差异有利于凋落叶中镉和铬离子的释放.

In order to investigate the releases of heavy metals from plant litter in alpine forest,a litterbag experiment was conducted in a fir primeval forest of western Sichuan from November 2012 to October 2014.The concentrations and decomposition rates of cadmium and chromium in foliar litter of Abies faxoniana,which is the constructive species in this area,were observed to find out about the snow formation stages,snow cover stages and snow melt stages and the growing seasons in the two years.The results showed that the initial concentrations of cadmium and chromium in foliar litter of Abies faxoniana were 59.7±5.7μg/kg and 3.81±0.26mg/kg,respectively,whereas the concentrations increased 3.0times and 87.0%,respectively,after the two years of decomposition.The concentrations of both cadmium and chromium in foliar litter of Abies faxonianaincreased to reasonable extents during the snow formation stages and growing seasons,implying that a certain amount of cadmium and chromium were inputted to soil surface through atmospheric wet deposition.Moreover,the concentrations of cadmium and chromium significantly declined during the snow cover and snow melt stages,suggesting that the heterogeneities of hydrothermal conditions that were induced by the formation and melt of snow cover in various stages promoted the releases of cadmium and chromium in foliar litter in alpine forest of western Sichuan.