退化高寒草原浅层土壤冻融作用特征分析

为了探讨退化高寒草原浅层土壤冻融特征,设置研究样地,测定不同退化程度草地0～40cm土层在一个完整冻融周期的土壤温度变化数据,对退化高寒草原浅层土壤冻融作用的发生时间、土壤温度的时空变化等规律进行分析。结果表明:随着高寒草原退化程度的加剧,土壤冻结、消融起始日期提前,重度退化较未退化各土层冻结、消融起始日期分别提前7～12d、16～26d;不同退化程度样地土壤冻结至消融历时207～226d,冻结持续时间随退化程度的加剧而缩短;0～40cm土层,随土层的加深,土壤进入冻结和消融的起始日期延迟,冻结持续时间延长;随退化程度加剧,0～40cm土层完成冻结和消融用时缩短,更快地进入冻结和消融状态;不同退化程度样地土壤冻结锋面自地表向较深土层下移速度不同,退化程度越重,土温梯度及变化速率越大,土壤更易升温和降温;研究样地土温与气温存在相关性,随着退化程度的加剧,各土层土温与气温的相关系数分别为0.907～0.656、0.930～0.681、0.939～0.723、0.942～0.793,土温与气温的相关程度随着退化程度的加剧而增强、随着土层的加深而减弱。在退化高寒草原研究样地,不同退化程度及不同土层影响土壤冻结、消融的发生时间,冻结持续时间,温度变化幅度和速率以及土温对气温的响应程度,由退化导致的土壤冻融作用特征的改变,均不利于高寒草原生态系统的稳定。

Analysis of Freeze-thaw Action Characteristics in Shallow Layer Soil of Degraded Alpine Steppe

Through research sample plots on the alpine steppe, we determined the temperature data of a complete freeze-thaw cycle in plots of different degradation degrees at 0-40 cm soil layers and we also analyzed occurrence times of oil freeze-thaw action,soil temperature spatial,temporal variations regularities and the characteristics of freeze-thaw action in shallow layer soil of degraded alpine steppe.The results showed that with the increase of degradation degree of the alpine steppe, the initial dates of soil freezing and thawing were early, and the severely degraded soils were 7-12 d earlier and 16-26 d earlier than the un-degraded soil layers, respectively. The freezing of soil to thawing lasted for 207-226 d, and the duration of freezing shortened with the increase of degradation degree. In the 0-40 cm soil layer, the start date of soil freezing and thawing delayed and the duration of freezing prolonged with the increase of soil layers depth.As the degradation degree increased, the 0-40 cm soil layer shortened when it was frozen and ablated, and entered the freezing and thawing status faster. The soil freezing frontal surface in different degraded plots had different speeds from the surface to the deeper soil layers. The more severe the degrading, the greater the soil temperature gradient and the rate of change were,the easier the soil temperature rised and falled; the soil temperature and air temperature of the sample plots are correlated. With the increase of degradation degree, the correlation coefficients of soil temperature and air temperature in all soil layers were 0.907-0.656, 0.930-0.681, 0.939-0.723, 0.942-0.793 respectively. The degree of correlation between soil temperature and air temperature increaseed with the increase of degradation degree and with the decrease of soil layers depth. In the study, sample plots of degraded alpine steppe, different degradation degrees and different soil layers affected the occurrence of soil freezing and thawing, the duration of freezing, the extent and rate of temperature changed, and the response of soil temperature to temperature. Characteristics changes of the soil freeze-thaw action caused by degradation were not conducive to the stability of the alpine steppe ecosystem.