| 摘要: |
| 【目的】研究陕西榆林地区旱柳和小叶杨夜间树干液流的变化特征，为毛乌素沙地造林选种提供依据。【方法】利用热消散探针法测量了陕西榆林地区旱柳（2011-04-28-11-07）和小叶杨（2011-06-27-11-07）的夜间树干液流密度，利用自动气象站测量风速、温湿度、净辐射、降雨量和土壤水分等环境因子，计算空气水汽压亏缺，分析夜间树干液流密度与空气水汽压亏缺、风速和白天总蒸腾量的相关关系。【结果】旱柳和小叶杨树干液流密度均呈现明显的昼夜波动，且白天（07：00-19：00）高，晚上低。白天旱柳和杨树的平均树干液流密度分别为6.79和6.49g/（cm2·h） ，而夜间平均树干液流密度分别是0.82和0.63 g/（cm2·h）。雨天夜间树干液流比晴天大，主要是因为强降雨后，土壤水分明显增多，40 cm以上土层的土壤水分增加了10%左右。夜间树干液流密度与空气水汽压亏缺、风速和白天总蒸腾量呈极显著相关，旱柳夜间树干液流密度与三者的相关系数分别是0.62，0.42和0.44,小叶杨与三者的相关系数分别是0.35，0.29和0.50。旱柳和小叶杨夜间树干液流密度对整树总蒸腾量的平均贡献率分别为11.4%，7.1%。【结论】旱柳和小叶杨2个树种均存在明显的夜间树干液流，且雨天的夜间树干液流比晴天高。影响夜间树干液流的因素是空气水汽压亏缺、风速和白天总蒸腾量，树干液流是由夜间补水和蒸腾共同造成的。旱柳夜间树干液流对总蒸腾量的贡献率较高，且随季节变化大，而杨树夜间液流对总耗水量的贡献率小且稳定。 |
| 关键词: 旱柳 杨树 夜间树干液流 环境因子 |
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| 基金项目:国土资源大调查项目（1212010634204）；中荷水与生态伙伴计划项目；国家自然科学基金项目（41002084）；国土资源部地下水与生态野外科学观测研究基地资助项目 |
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| Characteristics of night time sap flow of Salix matsudana and Populus simonii in Yulin,Shaanxi |
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| Abstract: |
| 【Objective】The characteristics of nighttime sap flow of Salix matsudana and Populus simonii were studied for improve tree selection in the Maowusu desert.【Method】The thermal dissipation probes were used to measure the night sap flow of S.matsudana and P.simonii trees in Yuling,Shaanxi from June 27,2011 to November 7,2011.Wind speed,air temperature,humidity,net radiation and soil water contents were measured at an automatic weather station.Correlation analysis was performed to study the relation between night time sap flow and vapor pressure deficit and wind speed.【Result】The sap flow densities of S.matsudana and P.simonii showed significant diurnal fluctuation with high values in daytime and low values in night time.In daytime,the average sap flow densities of S.matsudana and P.simonii were 6.79 and 6.49 g/(cm2·h) respectively,while that for nighttime were 0.82 and 0.63 g/(cm2·h),respectively.The night sap flows in rainy days were higher than that in sunny days due to the significant increase of water contents after rainfall (10% increase of soil water contents in the top 40cm layer).The night sap flow correlated well with vapor pressure deficit,wind speed and total daytime transpiration with coefficients of 0.62,0.42 and 0.44 respectively for S.matsudana and 0.35,0.29 and 0.50 respectively for P.simonii.The mean contributions of night recharge to the whole tree transpirations for S.matsudana and P.simonii were 11.4% and 7.1%,respectively.【Conclusion】Both S.matsudana and P.simonii had significant nigh sap flow,which correlated with vapor pressure deficit,wind speed and the total daytime transpiration,indicating that the night sap flow resulted from night time recharge and daytime transpiration. |
| Key words: Salix matsudana Populus simonii night time sap flow environmental factors |
