三江源高寒草甸土壤化学计量特征及酶活性对不同退化程度的响应

Responses of soil stoichiometries and enzyme activities to alpine meadow degradation in the headwaters of Three Rivers

土壤化学计量特征及酶活性是反映植物生长速率和养分限制的重要因子。为探究三江源高寒草甸退化过程中土壤化学计量特征及酶活性的变化特征及相互作用关系,本研究采用野外采样与室内分析相结合的方法,分析了不同退化程度(原生植被、轻度退化、中度退化、重度退化)对三江源高寒草甸的土壤有机碳(SOC)、全碳(TC)、全氮(TN)、全磷(TP)、全钾(TK)含量、pH值、土壤化学计量比、酶活性的影响及相互作用关系。结果表明:(1)随退化程度的加剧,不同土层土壤中的SOC和TN含量整体呈降低趋势,TK含量呈递增趋势,不同土层差异不显著。TP含量表现为轻度退化最高,不同土层TP含量均大于0.7 g·kg^(-1),pH值随退化程度加剧变化不明显。(2)土壤C、N、P、K化学计量比整体随着退化程度的加剧呈降低趋势,其中碳氮比值变化较为稳定。(3)β-1,4-木糖苷酶(BX)、β-N-乙酰氨基葡萄糖苷酶(NAG)、酸性磷酸酶(AP)、β-纤维二糖苷酶(BCE)、β-葡萄糖苷酶(BG)五种酶活性在不同土层中均表现为轻度退化显著高于其他退化程度(P<0.05)。(4)土壤SOC、TN、TP含量及化学计量比与AP、BG、BCE、BX、NAG五种酶活性呈正相关关系,pH值与五种酶活性呈显著负相关关系(P<0.05)。综上,高寒草甸退化与土壤化学计量特征和土壤酶活性关系密切,土壤化学计量特征和酶活性在不同退化阶段表现出较大差异。本研究结果为高寒草甸不同退化阶段的治理与恢复提供了一定的理论依据。

Soil stoichiometries and enzyme activities are important indices for plant growth and nutrient cycles.In order to explore the changes and interaction between soil stoichiometries and enzyme activities during the deg⁃radation of the alpine meadow in the headwaters of Three Rivers,the field sampling and laboratory analysis was used in this study.The effects of different degradation degrees(natural vegetation,light degradation,moderate degradation and severe degradation)on the soil organic carbon(SOC),total carbon(TC),total nitrogen(TN),total phosphorus(TP),total potassium(TK),pH,soil stoichiometries and enzyme activities and their interactions were analyzed.The results show that:(1)With the aggravation of degradation degree,SOC and TN contents in different soil layers showed an overall decreasing trend,while TK contents showed an increasing trend,and there was no significant difference among soil layers.TP content showed the highest values in light degradation areas,with all the values greater than 0.7 g·kg^(-1).The pH value did not change significantly with the degradation degree.(2)The stoichiometric ratio of C,N,P and K of soil decreased with degradation degree,and the ratios of carbon to nitrogen were relatively stable.(3)The activities ofβ-1,4-xylosidase(BX),β-nacetylglucosaminidase(NAG),acid phosphatase(AP),β-fiber diglycosidase(BCE)andβ-glucosidase(BG)in different soil layers were higher in the light degradation(P<0.05)than other levels of degradation.(4)SOC,TN,TP content and stoichiometric ratios were positively correlated with the activities of AP,BG,BCE,BX and NAG,while pH was negatively correlated with the activities of five enzymes(P<0.05).In conclusion,the degradation of alpine meadow is closely related to soil stoichiometries and soil enzyme activities,and soil stoi⁃chiometries and enzyme activities showed great differences among different degradation stages.Our results pro⁃vide a scientific basis for the treatment and restoration of alpine meadow at different degradation stages.