陇东黄土高原区人工刺槐树干液流特征

Study on sap flow characteristics of Robinia pseudoacacia artificially grown in hilly and gully region of Loess Plateau in eastern Gansu

【目的】对陇东黄土高原区人工刺槐树干液流动态变化特征,及其与环境因素的响应关系进行研究,为该区域森林生态耗水的准确估计和林地水分的综合管理提供借鉴.【方法】通过热扩散式液流探针(TDP)对生长季刺槐林树干液流进行连续监测,并利用样地内安装的自动气象站同步监测有效太阳辐射、空气温度、相对湿度和风速等气象因素,对液流速率与各气象因素进行相关回归分析.【结果】刺槐树干液流日变化存在"昼高夜低"的现象;刺槐树干液流速率在晴天呈"单峰型"变化,阴天呈"多峰型"变化,雨天呈不规则波动;刺槐树干液流速率在整个生长季月均值呈"低-高-低"的变化,其中10月份的液流速率最小(193.19 g/h),8月份的液流速率最大(652.31 g/h);环境因素对白天树干液流速率的影响表现为:温度(0.839)>相对湿度(-0.747)>太阳辐射(0.721)>水汽压亏缺(0.718)>风速(0.260);对晚间树干液流速率的影响表现为:水汽压亏缺(0.615)>空气温度(0.608)>相对湿度(-0.505)>风速(0.048).典型天气条件下,太阳辐射对晴天和阴天相关性最显著,分别为0.837、0.855(P<0.01),雨天条件下,空气温度影响最显著,相关系数为0.220(P<0.01).【结论】陇东黄土高原人工刺槐液流速率日变化为昼高夜低趋势,整个生长季液流速率为先升高后降低规律,不同时间尺度下影响刺槐树干液流速率的环境因子不同;建立了6种不同时间尺度下树干液流速率和环境因子的回归模型.

【Objective】To provide the reference for accurate estimation of forest ecological water consumption and integrated management of forest water in the Loess Plateau of Eastern Gansu Province by studying the dynamic characteristics of stem sap flow of artificially grown Robinia pseudoacacia and its response to environmental factors.【Method】The sap flow in the trunk of R.pseudoacacia was continuously monitored in growing season with TDP.The correlation and regression analysis between sap flow rate and meteorological factors were conducted based on the data of synchronous monitoring of effective solar radiation,air temperature,relative humidity and wind speed by meteorological stations installed in the sample plot.【Result】The diurnal variation of sap flow was high in day time and low in night time.The sap flow rate shown single peak in sunny days,multi-peak in cloudy days and irregular fluctuation in rainy days.The monthly mean sap flow rate shown a‘low-high-low’pattern in the whole growing season,and it was the lowest(193.19 g/h)in October,and the highest(652.31 g/h)in August.The influence level of single environmental factor on sap flow rate in daytime was temperature(0.839)>relative humidity(-0.747)>solar radiation(0.721)>water vapor pressure deficit(0.718)>wind speed(0.260),and it was water vapor pressure deficit(0.615)>air temperature(0.608)>relative humidity(-0.505)>wind speed(0.048)in night.Under typical weather conditions,solar radiation had the most significant correlation with sunny and cloudy days,which were 0.837 and 0.855(P<0.01),respectively.In rainy days,air temperature had the most significant influence,and the correlation coefficient was 0.220(P<0.01).【Conclusion】The sap flow rate of artificially grown R.pseudoacacia in the Loess Plateau of Eastern Gansu showed a diurnal trend of high and low at night.The sap flow rate increased first and then decreased during the whole growing season.The environmental factors affecting sap flow rate were different at different time scales.The regression models of sap flow rate and environmental factors at six different time scales were established by multiple linear regression.