祁连山中部不同植被群落土壤呼吸对覆盖物类型的响应

Responses of soil respiration to litter cover types in different vegetation communities in the middle part of the Qilian Mountains

在祁连山中部天涝池流域,选择3个典型植被群落样地(青海云杉林、祁连圆柏林和金露梅灌丛),利用LI-8100土壤碳通量自动测量系统对不同覆盖物下和裸土土壤呼吸速率(R_(S))进行测定.结果表明,苔藓层和枯落物层的覆盖会显著增加土壤呼吸通量,贡献率的大小顺序为青海云杉苔藓>青海云杉枯落物>祁连圆柏枯落物>金露梅枯落物;覆盖物会增加或降低R_(S)对温度的敏感性,R_(S)对土壤5 cm处温度的响应明显大于对地表温度的响应;3个样地不同覆盖物和裸土R_(S)日动态变化曲线均呈单峰型,峰值出现在13:00-17:30,7月枯落物和苔藓覆盖较裸土R_(S)日动态达到峰值的时间提前0.5~2 h,8-9月滞后0.5~3 h;不同覆盖物下和裸土R_(S)的月均值大小均为金露梅>青海云杉>祁连圆柏,枯落物和苔藓层的存在与否不影响土壤呼吸的季节动态规律;各植被群落不同覆盖物和裸土R_(S)与地表温度、地表湿度、土壤5 cm处温度和含水体积分数之间呈显著性指数或幂函数相关关系(P<0.01).

The Tianlaochi catchment in the middle part of the Qilian Mountains was selected as the study area,and the typical vegetation communities of Picea crassifolia forest,Sabina przewalskii forest and Potentilla fruticosa shrub were studies to measure the soil respiration rate(R_(S))under different mulches using Li-8100 soil carbon flux automatic measurement system.The results showed that the moss layer and litter layer significantly increased the soil respiration flux,the order of contribution rate to Rbeing the moss layer of P.crassifolia>litter layer of P.crassifolia>litter layer of S.przewalskii>litter layer of P.fruticosa;mulches could also increase or decrease the sensitivity of R_(S) to temperature,and th response of R_(S) to soil temperature at 5 cm was significantly greater than that to surface temperature.Th daily change curves of R_(S) in both soils covered by litter and none in the three plots expressed an all single peak type,and the peak of the respiration rate appeared between 13:00-17:30.In July,the peak valu of R_(S) in the soil covered by litter and moss was 0.5-2 h earlier than that in bare soil,while it was 0.5-3 h later from August to September.The sequence of monthly mean R_(S) in both the litter covering and the bar soil in different vegetation communities was P.fruticosa>P.crassifolia>S.przewalskii sample plots.Th presence of litter and moss layer did not affect the seasonal change trend of soil respiration.The R_(S) in each vegetation community was related to surface temperature,surface humidity,soil temperatur at 5 cm and volumetric water content.There was a significant exponential or power function correlation(P<0.01).