川西高山峡谷区暗针叶林粗木质残体金属元素贮量特征

Metal elements storage of coarse woody debris in dark coniferous forests in the alpine valley of western Sichuan

普遍存在于森林地表的粗木质残体(Coarse woody debris,CWD)是森林生态系统的重要组成部分.金属元素不断在CWD中积累—释放—转移,是认识植物-土壤金属元素循环的关键纽带.因此以长江上游高山峡谷区暗针叶林不同类型不同腐烂等级CWD为研究对象,调查其金属元素含量及贮量特征.结果表明:CWD类型和腐烂等级显著影响金属元素含量.CWD中生物必需非重金属元素(K、Ca、Na和Mg)含量分别介于0.29-2.56、2.41-8.13、0.56-1.65和0.34-1.03 g/kg之间,生物必需重金属元素(Cu、Mn和Zn)含量分别介于1.71-6.00、0.03-1.01和0.06-0.73 g/kg之间,非生物必需重金属元素含量(Cr、Cd和Pb)分别介于3.74-34.54、0.07-3.60和0.73-36.10 mg/kg之间.高山峡谷区暗针叶林CWD生物必需非重金属(K、Ca、Na和Mg)总贮量分别为43.77、220.63、40.78和31.37 kg/hm^2,生物必需重金属元素(Cu、Mn和Zn)总贮量分别为0.12、16.11和9.91 kg/hm^2,非生物必需重金属元素(Cr、Cd和Pb)总贮量分别为0.10、0.16和0.72 kg/hm^2.不同类型CWD金属元素贮量表现为倒木>根桩>大枯枝>枯立木,且不同金属元素在相同类型CWD不同腐烂等级之间基本具有相对一致的变化趋势.可见,CWD是高山峡谷区暗针叶林金属元素重要贮存场所之一,其降解过程中金属元素的释放可能是生态系统元素循环的重要途径.

Coarse woody debris （CWD） is one of the important components in forest floor. The accumulation-releasetransferation of metal elements in CWD is a key part of material cycling in forest ecosystems, which is essential in understanding the linkage between plant and soil by element cycling. So far little is known about the characteristics of metal elements in CWD. This study investigated a dark coniferous forest in the upper reaches of the Yangtze River. The CWD with different types and different decay classes were sampled, and the concentration and stock of metal elements in the CWD were analyzed. The CWD types and decay classes showed significant effects on the concentrations in CWD. Biological essential macroelements （K, Ca, Na and Mg） concentrations were 0.29-2.56, 2.41-8.13, 0.56-1.65 and 0.34-1.03 g/kg, respectively. Biological essential heavy metal elements （Cu, Mn and Zn） concentrations were 1.71-6.00, 0.03-1.01 and 0.06-0.73 g.kg-1, respectively, in CWD. Non-biological heavy metal elements （Cr, Cd and Pb） concentrations were 3.74-34.54, 0.07-3.60 and 0.73-36.10 mg/kg in CWD. Stocks of biological essential macroelements （K, Ca, Na and Mg） in CWD were 43.77, 220.63, 40.78 and 31.37 kg/hm2 in the dark coniferous forest; the stocks of biological essential heavy metal elements （Cu, Mn and Zn） were 0.12, 16.11 and 9.91 kg.hm-2, and the stocks of Non-biological heavy metal elements （Cr, Cd and Pb） were 0.10, 0.16 and 0.72 kg/hm2, respectively. In addition, the stocks of metal element showed the order as Fallen log 〉 Stump 〉 Large branch 〉 Snag, whereas the elements in CWD with different decay classes exihibited the similar tendency. The results suggest that CWD is an important metal elements storage place in the dark coniferous forest. The elements release along with CWD decomposition processes could be one of the primary ways in elements cyling.