模拟氮沉降对华西雨屏区天然常绿阔叶林凋落叶分解过程微生物生物量的影响

为进一步深化氮沉降对凋落物分解影响的研究,2016年3月—2017年3月,在华西雨屏区天然常绿阔叶林内,用凋落叶分解袋法研究了模拟氮沉降对凋落叶分解过程中微生物生物量碳(MBC)、微生物生物量氮(MBN)和微生物生物量磷(MBP)的影响。实验设置了对照(0 g N m~(-2)a~(-1))、低氮(5 g N m~(-2)a~(-1))、中氮(15 g Nm~(-2)a~(-1))和高氮沉降(30 g N m~(-2)a~(-1)) 4个处理。结果表明:低氮和中氮处理显著增加了凋落叶分解过程中的MBC和MBN,以低氮处理增加幅度最高;低氮和中氮处理对凋落叶分解过程中的MBP影响不显著;高氮处理显著降低了分解过程中的MBC、MBN和MBP。随模拟氮沉降量的递增,凋落叶分解过程中微生物生物量碳氮比逐渐减少,微生物生物量碳磷比呈现先增加后下降的趋势。研究结果说明,氮沉降影响了华西雨屏区天然常绿阔叶林凋落物分解过程中微生物生物量,进而改变了凋落物的分解过程。

Effects of simulated nitrogen deposition on microbial biomass during litter decomposition in a natural evergreen broad-leaved forest in the rainy area of West China

To understand the in-depth impacts of nitrogen deposition on the processes of litter decomposition, a field litterbag experiment was conducted in a natural evergreen broad-leaved forest in the rainy area, West China, from March 2016 to 2017. Microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) during litter decomposition were investigated under four levels of simulated nitrogen deposition treatments, including control (CK, 0 g N m^-2 a^-1), low nitrogen (LN, 5 g N m^-2 a^-1), medium nitrogen (MN, 15 g N m^-2 a^-1) and high nitrogen (HN, 30 g N m^-2 a^-1) deposition. The results showed that LN and MN treatments significantly increased MBC and MBN during litter decomposition, but a higher increase was observed under LN than under MN treatment. LN and MN treatments did not significantly affect MBP during litter decomposition. However, HN treatment significantly reduced MBC, MBN, and MBP. The microbial biomass C/N decreased gradually with an increase of N deposition levels, although the microbial biomass C/P initially increased and then decreased. The results indicated that nitrogen deposition could play an important role in litter decomposition processes by regulating microbial biomass.