模拟氮沉降对华西雨屏区天然常绿阔叶林土壤微生物生物量碳和氮的影响

Effects of simulated nitrogen deposition on soil microbial biomass carbon and nitrogen in natural evergreen broad-leaved forest in the Rainy Area of West China

为理解模拟氮沉降对华西雨屏区天然常绿阔叶林土壤微生物生物量碳(MBC)和氮(MBN)的影响,通过一年野外模拟氮(NH_4NO_3)沉降试验,氮沉降水平分别为对照(CK,0g N·m^(-2)·a^(-1))、低氮沉降(L,5 g N·m^(-2)·a^(-1))、中氮沉降(M,15 g N·m^(-2)·a^(-1))和高氮沉降(H,30 g N·m^(-2)·a^(-1)),研究了氮沉降对天然常绿阔叶林土壤MBC和MBN的影响.结果表明:氮沉降显著降低了0~10 cm土层MBC和MBN,且随氮沉降量的增加,下降幅度增大;L和M处理对10~20 cm土层MBC和MBN无显著影响,H处理显著降低了10~20 cm土层土壤MBC和MBN;氮沉降对MBC和MBN的影响随土壤深度的增加而减弱.MBC和MBN具有明显的季节变化,在0~10和10~20 cm土层均表现为秋季最高,夏季最低.0~10和10~20 cm土层土壤微生物生物量C/N分别介于10.58~11.19和9.62~12.20,表明在华西雨屏区天然常绿阔叶林土壤微生物群落中真菌占据优势.

To understand the effects of increasing nitrogen deposition on soil microbial biomass carbon （MBC） and nitrogen （MBN）, an in situ experiment was conducted in a natural evergreen broad-leaved forest in Ya＇ an City, Sichuan Province. Four levels of nitrogen deposition were set： i.e., control （CK, 0 g N · m-2 · a-1） , low nitrogen （L, 5 g N · m-2 · a-1） , medium nitrogen （M, 15 g N· m-2 . a-1） , and high nitrogen （H, 30 g N · m-2 · a-1）. The results indicated that nitrogen deposition significantly decreased MBC and MBN in the 0-10 cm soil layer, and as N deposition increased, the inhibition effect was enhanced. L and M treatments had no significant effect on MBC and MBN in the 10-20 cm soil layer, while H treatment significantly reduced. The influence of N deposition on MBC and MBN was weakened with the increase of soil depth. MBC and MBN had obvious seasonal dynamic, which were highest in autumn and lowest in summer both in the 0-10 and 10-20 cm soil layers. The fluctuation ranges of soil microbial biomass C/N were respec- tively 10.58-11.19 and 9.62-12.20 in the 0-10 cm and 10-20 cm soil layers, which indicated that the fungi hold advantage in the soil microbial community in this natural evergreen broad-leaved forest.