民勤绿洲荒漠过渡带梭梭东、西方位树干液流特征及相关性分析

采用Grainer热扩散式探针法( TDP )连续测定了6月份至11月份民勤绿洲荒漠过渡带梭梭﹝Haloxylon ammodendron ( C. A. Mey.) Bunge﹞东、西方位的树干液流速率，并同步测定了相关环境因子；在此基础上，对晴天、阴天和雨天东、西方位树干液流速率的日变化以及实验期间东、西方位树干液流速率和各环境因子的变化进行了分析，并对不同天气和时间尺度东、西方位树干液流速率间的相关性及其与部分环境因子的相关性进行了分析。结果表明：在生长旺盛期(6月份至8月份)，晴天时梭梭东、西方位树干液流速率的日变化均表现为明显的“宽峰型”曲线；在整个观测期内，不同天气的树干液流速率存在一定差异，东、西方位的树干液流速率也存在一定差异，并且其差异在夜间较白天更明显；总体来看，东方位的树干液流速率高于西方位。相关性分析结果表明：不同天气和时间尺度东、西方位的树干液流速率间存在极显著正相关性，其相关系数均在0.90以上并略有差异。总体来看，晴天梭梭东、西方位树干液流速率间的相关性高于阴天和雨天，并且，日尺度东、西方位树干液流速率间的相关性最强。晴天东、西方位树干液流速率与各环境因子的相关性高于阴天和雨天，并且，小时尺度东、西方位树干液流速率与环境因子间的相关性高于日尺度。西方位树干液流速率与环境因子的相关性略高于东方位，说明西方位的树干液流速率对环境因子变化的反应更敏感。晴天和阴天东、西方位树干液流速率与参考作物蒸散量( ET0)的相关性极显著，其相关系数均在0.70以上，说明根据梭梭东、西方位树干液流速率计算其耗水量具有一定的可行性。研究结果显示：梭梭树干液流速率与天气、环境因子、时间尺度和树干方位等均有一定关系。

Characteristics of sap flow of east and west trunks of Haloxylon ammodendron in Minqin oasis-desert ecotone and correlation analyses

Sap flow rate of east and west trunks of Haloxylon ammodendron ( C. A. Mey.) Bunge in Minqin oasis-desert ecotone was continuously determined by Grainer thermal diffusion probe method ( TDP) from June to November, and related environmental factors were determined simultaneously. On the basis, diurnal change of sap flow rate of east and west trunks on sunny, cloudy and rainy days and changes of sap flow rate of east and west trunks and environmental factors during experimental period were analyzed, and correlations between sap flow rate of east and west trunks and correlations of them with some environmental factors in different weather and time scales were analyzed. The results show that during vigorous growth period ( from June to August ) , diurnal change of sap flow rate of east and west trunks of H. ammodendron on sunny day both appears obviously“broad peak type” curve. During whole observation period, there is a certain difference in trunk sap flow rate in different weather, and also a certain difference in sap flow rate between east and west trunks and their difference in the nighttime is more obvious than that in the daytime. On the whole, sap flow rate of east trunk is higher than that of west trunk. The correlation analysis results show that there are extremely significantly positive correlations between sap flow rate of east and west trunks of H. ammodendron in different weather and time scales, their correlation coefficients are all above 0. 90 with a little difference. On the whole, correlation between sap flow rate of east and west trunks on sunny day is higher than that on cloudy and rainy days, and that in day scale is the strongest. Correlation of sap flow rate of east and west trunks with environmental factors on sunny day is higher than that on cloudy and rainy days, and that in hour scale is higher than that in day scale. Correlation of sap flow rate of west trunk with environmental factors is slightly higher than that of east trunk, meaning that response of sap flow rate of west trunk of H. ammodendron to environmental factor change is more sensitive. Correlations of sap flow rate of east and west trunks with reference crop evapotranspiration ( ET0 ) on sunny and cloudy days are extremely significant, their correlation coefficients are all above 0 . 70 , meaning that there is certain feasibility in according to sap flow rate of east and west trunks of H. ammodendron for calculating its water consumption. It is suggested that there is a certain relationship of trunk sap flow rate of H. ammodendron with weather, environmental factor, time scale and trunk position, etc.