藏北高寒草地土壤有机质化学组成对土壤CO_2排放的影响

Effects of soil organic matter chemical quantity on carbon dioxide emissions in alpine grassland soils in Northern Tibet

土壤有机质(Soil organic matter, SOM)是草地生态系统的重要碳库,但由于SOM形成的复杂性,长期以来对SOM化学组成特征的研究存在一定挑战性。本研究基于热裂解气相色谱–质谱联用(Pyrolysis-gas chromatography/mass spectrometry, Py-GC/MS)的方法,从SOM化学组成的角度分析了其对藏北高寒草甸和高寒草原两种高寒草地土壤CO_2排放的影响。研究结果显示:1)含氮化合物是两种高寒草地SOM化学组成中重要成分,分别占总SOM的38.0%和52.5%;2)多糖类和萜烯类在两种高寒草地SOM中差异性达到显著水平(P <0.05);3)通过分析两种草地SOM化学组成与土壤CO_2排放量之间的相关关系,发现多糖直接影响着土壤CO_2累积排放量,拟合方程为Y=86.76X+344.87(R^2=0.63, P<0.05),式中Y为CO_2累积排放量,X为多糖类的相对含量;4)SOM化学组成中多糖类、含氮化合物和芳香烃物质与土壤中细菌、真菌、放线菌、革兰氏阴性细菌和革兰氏阳性细菌之间显著相关(P <0.05)。综上可知,高寒草地SOM化学组成直接关系着土壤微生物的数量和CO_2的排放过程,SOM的化学成分和化学组成可以在一定程度上直接用于预测土壤CO_2的排放特征。

The soil organic matter(SOM)represents the main terrestrial carbon pool and plays a key role in the carbon biogeochemical cycle.However,it is challenging to characterize the SOM at the molecule scale,due to its heterogeneous composition.To isolate the effects of the SOM composition on carbon dioxide emission,correlations were made between the SOM compositions and cumulative CO2 emissions in two alpine grassland soils.The SOM compositions were investigated using pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS).The results showed that:1)the N-compounds were the main chemical components in the two types soils,with values of 38.0%and 52.5%;2)there was a significant difference in the relative abundance of polysaccharides and terpenes between the two grassland types(P<0.05);3)polysaccharides affect the soil carbon dioxide emissions,the equation for which was Y=86.76 X+344.87(R^2=0.63,P<0.05)(Y is the cumulative CO2 emission,X is the relative abundance of polysaccharides);4)the relative abundance of polysaccharides,N-compounds,and aromatics are significantly(P<0.05)correlated with the bacteria,fungi,actinomycetes,gram-negative bacteria,and gram-positive bacteria.These results indicate that the SOM chemical composition of alpine grasslands is directly related to the soil microbial community and cumulative CO2 emission,and the relative abundance of some compounds can be used to analyze the soil respiration under specific incubation conditions,which is important for understanding the characteristics of soil CO2 emissions under different environmental conditions.