土壤动物对模拟N沉降的响应

Effects of simulated N deposition on soil fauna

通过人工喷施 NH4 NO3而建立一个模拟 N沉降梯度系列的方法 ,研究了苗圃试验样地土壤动物群落对 N沉降增加的响应。实验分为 5个处理 :CK对照、T1、T2、T3和 T4 ,分别接受 0、5、10、15和 30 g N/ (m2 · a)的处理。经 6个月的施氮处理后 ,土壤动物个体总数随着 N沉降处理强度的变化 ,在水平尺度和垂直尺度上均产生了相应的变化。在水平分布上 ,由于 F1层 (0～ 5 cm)受到 N沉降处理最直接的影响 ,其动物个体数的变化趋势较明显 ,表现为 T2 >T1>CK>T3>T4 ,其中前两者显著高于其它处理 (P<0 .0 5 ) ,但 F2层 (5～ 10 cm)和 F3层 (10～ 15 cm)的情况变化比较复杂 ,趋势不明显。在垂直分布上 ,T2处理下多数土壤动物集中于 F1层 ,土层越深 ,土壤动物愈少 ,但在最大浓度 T4处理下 ,则完全相反 ,由 F1层向 F3层逐渐增多。总的来说 ,土壤动物在低 N沉降下趋向表层 ,而在高氮沉降下则趋向深层分布。与个体总数的分布格局相类似 ,土壤各层动物类群数总体上呈现明显的单峰变化格局 ,T2处理时类群最丰富 ,并显著高于其它各处理 (P<0 .0 5 ) ;在垂直分布上 ,也表现出先向表层集中后向土壤深层发展的趋势 ,T2处理为其拐点。甲螨随 N沉降强度加大变化的规律性很强 ,它也有个先发展后受遏制的过程 ,T2处理时达到峰值。

Nitrogen deposition is a serious global problem and will likely have a significant effect on ecosystem structure and function. The responses of soil fauna to a simulated N deposition were studied in a seedling site of subtropical China. Dissolved NH_4NO_3 was sprayed twice per month to the soil since January, 2003, equivalent to 0 (CK), 5 (T1), 10 (T2), 15 (T3) and 30 (T4) gN/(m^2·a). After six months of the experiment, the total number of individual soil animals varied depending on the N treatment level and soil layer. The number of soil animals exhibited a significant nonlinear relationship with N treatment levels in the upper soil layer (layer Ⅰ: 0~5cm). However, there was no such significant relationship in other soil layers (lay Ⅱ: 5~10cm and lay Ⅲ: 10~15cm). The highest number of individuals occurred in the upper soil layer (layer Ⅰ: 0~5cm) under low N treatment level, however, the highest number occurred in the deeper soil layer (lay Ⅲ: 10~15cm) under high N treatment level. The distribution pattern of the total number of soil fauna groups was similar to that of total individual number. Results from this study also suggested that soil oribatid is a good indicator of N deposition.