模拟氮沉降和降雨量改变对华西雨屏区常绿阔叶林土壤有机碳的影响

从2013年11月至2015年12月,通过原位试验,在华西雨屏区常绿阔叶林内设置了对照(CK)、氮沉降(N)、减雨(R)、增雨(A)、氮沉降+减雨(NR)、氮沉降+增雨(NA)6个处理水平,研究了模拟氮沉降和降雨量改变对常绿阔叶林土壤有机碳的影响。结果表明:华西雨屏区常绿阔叶林土壤各土层有机碳含量表现为夏季较高,春冬季较低,0—10 cm土层有机碳含量高于10—20 cm土层。从各处理土壤有机碳含量的平均值来看,0—10 cm土层土壤有机碳含量高低顺序表现为:RNRCKANNA;10—20 cm土层表现为:RNRACKNAN。模拟氮沉降和增雨处理促进了华西雨屏区常绿阔叶林土壤有机碳的累积,模拟减雨抑制了土壤有机碳的累积。常绿阔叶林0—10cm土层土壤C/N值显著高于10—20 cm,土壤C/N值随土层加深而呈现出增加的趋势,降雨使土壤C/N降低,增雨使土壤C/N增高。同一氮沉降条件下,增雨处理增加了土壤有机碳的含量,减雨处理减少了土壤有机碳的含量;同一降雨条件下,氮沉降增加土壤有机碳的含量。氮沉降和降雨对土壤可溶解性有机碳和微生物生物量碳含量产生显著影响(P0.05),对土壤活性碳含量影响不显著(P0.05);其交互作用对土壤有机碳、可溶解性有机碳、微生物生物量碳和活性碳含量影响不显著(P0.05)。

Effects of simulated nitrogen deposition and precipitation changes on soil organic carbon in an evergreen broad-leaved forest that is part of the Rainy Area of Western China

To understand the effects of nitrogen deposition and precipitation changes and their interaction on soil organic carbon, an experiment was conducted in situ within the Rainy Area of Western China in an evergreen broad-leaved forest from November 2013 to December 2015. The study had six treatments: a control(CK), nitrogen deposition(N), water reduction(R), water addition(A), nitrogen deposition×water reduction(NR), and nitrogen deposition×water addition(NA). The results revealed that the soil organic carbon contents in the different soil layers were high in summer and fall, but low in spring and winter. The soil organic carbon content was higher in the 0-10 cm soil layer than in the 10-20 cm soil layer. The average soil organic carbon content followed the order: R < NR < CK < A < N < NA in the 0-10 cm soil layer and R < NR < A < CK < NA < N in the 10-20 cm soil layer. Simulated nitrogen deposition and water addition promoted soil organic carbon accumulation, but water reduction inhibited it. The soil C/N ratio for the 0-10 cm soil layer was significantly higher than for the 10-20 cm layer and showed a rising trend as soil depth increased. Water reduction reduced the soil C/N ratio, but water addition increased the ratio and soil total organic carbon (TOC) content. However, water reduction reduced the soil TOC content under the same simulated nitrogen deposition conditions. Simulated nitrogen deposition increased soil TOC under the same rainfall conditions. Furthermore, nitrogen deposition and precipitation changes had significant effects on the soil extractable dissolved organic carbon (DOC) and microbial biomass carbon (MBC) (P < 0.05) contents, but their effect on soil labile carbon (LC) was not significant (P > 0.05); and the interaction between nitrogen deposition and precipitation changes did not have a significant effect on the soil TOC, DOC, MBC, and LC contents (P > 0.05)