土壤动物对柠条灌丛枯落物分解和土壤碳含量的影响

Effects of soil fauna on litter decomposition and soil carbon content in Caragana korshinskii shrub microhabitats

枯落物分解产生的碳是土壤碳含量的主要来源之一,在荒漠草原生态系统物质循环、能量流动中扮演着重要角色。本试验选取柠条锦鸡儿(Caragana korshinskii)灌丛枯落物为研究对象,利用网孔分解袋法(4、2和0.01 mm)研究了大型、中型、小型和极小型柠条灌丛微生境枯落物分解变化对土壤碳含量的影响。结果表明:1)在枯落物分解过程中,中小型土壤动物对枯落物分解的平均贡献率均高于大型土壤动物。且随着时间变化,全部土壤动物的贡献率正效应逐渐减弱,在分解至570 d时表现为负效应。2)全部土壤动物参与枯落物分解时,土壤碳含量表现为大型和中型高于小型和极小型微生境,且仅在分解至150和570 d时不显著(P <0.05)。3) Pearson相关分析表明,灌丛微生境中土壤碳含量与枯落物木质素含量呈显著正相关关系(P <0.01),与土壤动物贡献率无显著相关关系(P> 0.05)。综合分析表明,中小型土壤动物对枯落物分解具有促进作用,但分解所产生的碳不会引起土壤碳含量发生显著变化。

Litter decomposition is one of the main sources of soil carbon content, and it plays an important role in the material cycle and energy flow of desert steppe ecosystems. The objective of the present study was to investigate the contribution of litter decomposition(associated with soil fauna) to soil carbon content in shrub microhabitats. In this study,the decomposition of Caragana korshinskii shrub litter, soil fauna communities, and soil carbon content were examined using the litterbag method(mesh sizes: 4, 2, and 0.01 mm) in microhabitats having different shrub sizes, including large,medium, small, and extremely small crown canopies. The results were as follows. 1) There was a significantly higher contribution of meso-micro soil fauna to litter decomposition than that of soil macrofauna, and the total soil fauna had a positive effect on litter decomposition at an early stage. However, the contribution rate of total soil fauna tended to be negative at 570 d. 2) When total soil fauna was involved in litter decomposition, soil carbon content in the shrub microhabitats of large and medium crown canopies was higher than that in the shrub microhabitats of small and extremely small crown canopies;it was insignificant only at 150 and 570 d of decomposition(P < 0.05). 3) Pearson correlation analysis showed that there was a significant positive correlation between soil carbon content and litter lignin content in shrub microhabitats(P < 0.01), but no significant correlation between soil carbon content and soil fauna contribution rate(P >0.05). In conclusion, meso-micro soil fauna could indeed promote litter decomposition;however, the carbon generated by litter decomposition did not cause significant changes in soil carbon content.