黄土丘陵区典型土地利用类型土壤-微生物量及其生态化学计量特征

Soil Microbial Biomass and Ecological Stoichiometric Characteristics of Typical Land Use Types in Loess Hilly Region

[目的]为探讨黄土丘陵区“上退下推”典型生态治理模式对土壤-微生物量C、N、P及其生态化学计量比的影响。[方法]以宁夏黄土丘陵区典型土地利用类型(人工林地、梯田和川道地)为研究对象,研究土壤-微生物量C、N、P含量对土地利用变化的响应,并分析其生态化学计量比、微生物熵(qMBC、qMBN、qMBP)及化学计量不平衡性(C∶N_(imb)、C∶P_(imb)、N∶P_(imb))之间的关系。[结果](1)3种典型土地利用类型下,人工林地土壤SOC、C∶P、N∶P高于梯田和川道地,而农耕用地(梯田和川道地)土壤TP含量则高于人工林地。(2)土壤微生物量C、N、P的含量分别为51.56~133.19,7.97~21.98,4.63~12.81 mg/kg。其中,土壤微生物量C、N、P均表现为人工林地>梯田>川道地;微生物量C、N、P的比值及C∶N_(imb)、C∶P_(imb)、N∶P_(imb)在各土地利用类型间无显著差异,具有一定的内稳性特征。(3)3种典型土地利用类型对微生物熵具有显著影响,qMBC表现为梯田地>人工林地>川道地,而qMBN和qMBP均表现为人工林地>梯田>川道地。通过RDA和蒙特卡洛置换检验得出,微生物量C∶P(R^(2)=0.75,p<0.01)和C∶P_(imb)(R^(2)=0.74,p<0.01)是影响土壤微生物熵变化的关键因素。[结论]综上所述,“上退下推”典型生态治理模式引起土壤C、P以及微生物量C、N、P含量的显著变化,典型土地利用类型下土壤-微生物量C、N、P及其化学计量比主要受到P元素的影响。

[Objective]This study was aimed to investigate the effects of the typical ecological management model of“upward retreat and downward push”on soil-microbial C,N and P and their ecological stoichiometric ratios in loess hilly areas.[Methods]Typical land use types(artificial forest land,terrace,and Chuanland)in the loess hilly area of Ningxia were selected to study the response of soil-microbial C,N and P contents to land use changes and to analyze the ecological stoichiometric ratios,microbial entropy(qMBC,qMBN,and qMBP),and stoichiometric imbalances(C∶N_(imb),C∶P_(imb),and N∶P_(imb))among the Relationship.[Results](1)Under the three typical land use types,SOC,C∶P,and N∶P in artificial forest land were higher than those in terraced and Chuanland,while TP content in agricultural land(terraced and Chuanland)was higher than that in artificial forest land.(2)The contents of soil microbial biomass C,N,and P ranged from 51.56 to 133.19,7.97 to 21.98,and 4.63 to 12.81 mg/kg,respectively.Among them,soil microbial biomass C,N,and P were in the order of artificial forest land>terrace land>Chuanland.The ratio of microbial biomass C,N,P,C∶N_(imb),C∶P_(imb),and N∶P_(imb)had certain characteristics of internal stability and had no significant difference among different land use types.(3)The three typical land use types had significant effects on microbial entropy,with the qMBC ranking as terraced land>artificial forest land>Chuanland,while the qMBN and qMBP ranking as artificial forest land>terrace land>Chuanland.Combined with RDA analysis,it was concluded that microbial biomass C∶P(R 2=0.75,p<0.01)and C∶P_(imb)(R 2=0.74,p<0.01)were the key factors affecting the change of qMB.[Conclusion]In summary,the typical ecological management mode of“upward retreat and downward push”caused significant changes in soil C,P and microbial C,N and P contents,and the soil-microbial C,N and P and their stoichiometric ratios were mainly influenced by phosphorus under the typical land-use types.