阿克苏市3种绿化乔木树干液流日变化特征

为了测算园林树木的蒸腾耗水量,应用热脉冲技术对阿克苏市3种常见绿化乔木(小叶白蜡、法国梧桐、桑树)进行树干液流的测定,并分析其日变化规律,同时运用自动气象站记录各气象参数数据,分析树干液流日变化与气象因子之间的相关性。结果显示：3种乔木树干液流速率之间有一定的差异,但其日变化过程几乎相似,均有明显的昼夜变化规律。白天的液流速率比夜间大,午间由于太阳辐射( Rs)过强出现午休现象,凌晨和晚上树干液流速率较低,夜间保持微弱的树干液流过程。小叶白蜡、法国梧桐、桑树等树干液流日变化都与太阳辐射、空气温度( Ta)、风速( Ws)呈显著正相关,而与空气湿度( H)呈显著负相关；逐步回归模型显示,影响小叶白蜡树干液流的主要气象因子是太阳辐射和空气湿度,模型拟合度为0.962,法国梧桐的是空气温度和空气湿度,拟合度为0.971,桑树的是空气温度和太阳辐射,拟合度为0.915。不同乔木的日累计液流量大小排序为小叶白蜡(57000±2400) mL﹥法国梧桐(55400±2100) mL﹥桑树(7600±1800)mL。

Sap flow diurnal variation of 3 main urban greening tree species in Aksu City

Stem sap flow ( SF) of common tree species, Fraxinus sogdiana , Platanus × acerifolia, and Morus alba, in Aksu City was determined by applying heat pulse technique, its daily variation characteristics, correlation between sap flow and meteorological factors were analyzed. There were certain differences in stem sap flow rate among three tree species, but there were still certain similarities in their daily change process. All of them had obvious diurnal variation law. Sap flow rate in daytime was higher than that in nighttime. At noon, midday depression appeared due to the high solar radiation. In the early morning and evening the stem sap flow rate was lower, while in nighttime stem sap flow process remained weak. Sap flow diurnal variation had significantly positive correlation with solar radiation, temperature and wind speed, and significantly negative correlation with humidity. According to stepwise regression model, solar radiation and humidity had the highest impact on the sap flow variation of Fraxinus sogdiana (R2=0.962), temperature and humidity for Platanus×acerifolia (R2=0.971), temperature and solar radiation for Morus alba (R2=0.915). Among these three tree species, Fraxinus sogdiana had the highest sap flow daily accumulation (57 000±2 400) mL, followed by Platanus×acerifolia (55 400±2 100) mL, and thirdly Morus alba (7 600±1 800) mL.