不同植物来源可溶性有机质对亚热带森林土壤酶活性的影响

Effects of dissolved organic matter from different plant sources on soil enzyme activities in subtropical forests

探究不同植物来源可溶性有机质(DOM)进入土壤后对酶活性的影响,可以为降水淋溶下亚热带地区不同森林生态系统土壤碳循环提供科学依据。该研究提取杉木(Cunninghamia lanceolata)、木荷(Schima superba)和楠木(Phoebe zherman)3种植物鲜叶中的DOM分别输入杉木人工林土壤中,以等量的去离子水添加为对照,进行25天的室内培养。培养结束后测定土壤理化性质、微生物生物量和酶活性等指标。结果表明:与对照处理(CT)相比,添加3种叶片DOM后,土壤总有机碳(SOC)、总氮(TN)含量和碳氮比均无显著变化。杉木叶片DOM添加处理(CL)的TN含量显著低于木荷叶片DOM添加处理(SL)和楠木叶片DOM添加处理(PL),碳氮比显著高于SL和PL。3种叶片DOM输入整体上提高了土壤溶解有机碳(DOC)和溶解有机氮(DON)的含量。叶片DOM输入后土壤微生物生物量碳(MBC)含量无显著变化,然而CL和SL的土壤微生物生物量氮(MBN)含量分别比CT降低了50.9%和51.1%,PL的MBN含量比CT提高了54.0%。与CT相比,不同植物来源DOM输入后,β-葡萄糖苷酶(βG)、纤维素水解酶(CBH)和过氧化物酶(PEO)3种酶活性均显著上升,而多酚氧化酶(PPO)活性则显著下降;此外,βG和CBH活性均表现出CL>SL>PL的特征。相关性分析的结果表明,添加叶片DOM 3种处理的SOC、TN、MBN含量和βG、CBH活性都与所输入DOM的DOC含量和腐殖化指数(HIX)显著相关,此外,土壤MBN含量和PPO活性与输入叶片DOM的pH呈正相关关系。冗余分析(RDA)结果表明,叶片DOM输入后引起土壤酶活性变化的关键因子是DON和DOC含量。总体来说,不同植物来源DOM性质的差异会影响土壤碳循环水解酶的活性,而叶片DOM输入后增加了土壤碳和氮的有效性,引起4种碳循环酶的不同响应。

Aims This study aims to explore the effects of dissolved organic matter(DOM)from different plant sources on subtropical forest soil enzyme activities in order to provide a scientific basis for soil carbon cycling under rainfall leaching conditions in different forest ecosystems of subtropical areas.Methods Three kinds of DOM,extracted from the fresh leaves of Cunninghamia lanceolata,Schima superb,and Phoebe zherman,were added to the soils of C.lanceolata plantation.Soil treated with deionized water of the same amount as the DOM solution served as the control.Incubation of treated and control soils was conducted for 25 days in the laboratory.The physical and chemical properties,microbial biomass,and enzyme activities of the soils were determined after incubation.Important findings The results showed that,compared with the control treatment(CT),soil total organic carbon(SOC)content,soil total nitrogen(TN)content,and carbon-nitrogen ratio had no significant changes after adding DOM.However,the TN of treatment with added C.lanceolata leaf DOM(CL)was significantly lower than that of treatments with added S.superb leaf DOM(SL)and P.zherman leaf DOM(PL),and the carbon-nitrogen ratio in CL was significantly higher than that in SL and PL.The three treatments with added DOM increased soil dissolved organic carbon(DOC)content and dissolved organic nitrogen(DON)content overall.There was no significant change in soil microbial biomass carbon(MBC)content after all three DOM inputs,while the microbial biomass nitrogen(MBN)content in CL and SL treatments was reduced by 50.9%and 51.1%,respectively,compared to CT.However,MBN content in PL treatment was increased by 54.0%than CT.DOM input significantly increased the activities ofβ-glucosidase,cellobiohydrolase,and peroxidase in comparison with CT,but significantly decreased the activity of polyphenol oxidase.In addition,bothβ-glucosidase and cellobiohydrolase activities showed the following characteristics:CL>SL>PL.The results of correlation analysis showed that the contents of SOC,TN and MBN and the activities ofβ-glucosidase and cellobiohydrolase of the treatments with DOM were significantly correlated with the DOC content and humification index(HIX)of added DOM.In addition,soil MBN content and polyphenol oxidase activity were positively correlated with the pH value of added DOM.The results of redundancy analysis(RDA)showed that the key factors causing the change in soil enzyme activities after DOM input were DON and DOC content.In general,differences in the properties of DOM obtained from different plant sources affect the activities of soil carbon-acquisition hydrolase.DOM input increases the availability of soil carbon and nitrogen,and elicits different responses from the four carbon-acquisition enzymes.This study provides a theoretical basis for exploring the process of carbon cycling in the rain-rich subtropical forest ecosystem.