基于电磁感应成像植被斑块土壤水盐效应研究

土壤水盐过程在植被斑块的形成与演变中起着十分关键的作用,但其与植被斑块间的相互作用关系因研究工具的限制而缺乏深入认识。以青海湖流域芨芨草斑块群落为研究对象,通过采用电磁感应(EMI)产生的表观电导率(ECa)成像解译土壤水分与盐分的时空动态变化,建立芨芨草斑块分布格局与土壤水盐变化过程之间的联系。结果表明:ECa分别与土壤水分、盐分间存在显著相关关系(P0.01),多元回归模型指出,ECa变化的81%可由土壤水分与盐分变化来解释,因此可用ECa变化表征土壤水分与盐分的变化;此外,强降雨事件前后ECa动态变化图指出,芨芨草斑块处土壤水分增加量高于基质区,说明芨芨草斑块能够快速聚集水分;而不论干湿状态或不同季节,芨芨草斑块处土壤水盐含量总是高于基质区,表现出时间稳定性,说明芨芨草斑块是土壤水盐的聚集区。因此,EMI成像可揭示芨芨草斑块土壤水盐空间分布及动态变化过程,为植被斑块的水文过程研究提供快速可靠的方法。

Effects of vegetation patches on soil water and salt dynamics using electromagnetic induction

The surface soil hydrology is extremely important for driving the formation and evolution of vegetation patches in water-limited ecosystems. However, the process of soil hydrology and its response to vegetation patches are unclear due to limited tools. This study chose patchy grass Achnatherum splendens as an indicator plant to reveal the spatial-temporal dynamics of soil water and salt, and soil water and salt responses to spatial patterns of A. splendens patches, were shown by electrical conductivity (ECa) images, in the study area of Qinghai Lake watershed in north-western China. The results showed that there were significant positive correlations (P<0.01) between ECa, and soil water and salt. ECa could be used as a proxy for the changes of soil water and salt, because soil water and salt could explain 81% of the ECa changes based on the multivariate regression model. Moreover, based on the time-lapse ECa images, the increment of soil water under A. splendens patches was higher than that of matrix zones, compared with before and after intensive rainfall, meaning A. splendens patches acted as sink to accumulate water runoff. Analysis of temporal stability showed spatial ECa patterns were highly consistent with the distributions of A. splendens patches, and soil water and salt content under A. splendens patches were remarkable higher than that of matrix zones, whatever the moist conditions or seasons. This indicated that A. splendens patches were the accumulation area for soil water and salt. Therefore, the findings of this study proved that it is a novel method to reveal the dynamics of soil water and salt, and its responses to the spatial patterns of A. splendens patches by EMI method, which might provide valuable insights in understating the hydrological process of patchy vegetation.