银川市5种典型城市树木蒸腾耗水特性及其受主要气象驱动力的影响

Transpiration and Water Consumption Characteristics of Five Typical Urban Trees and Their Response to Main Meteorological Drivers in Yinchuan

2021年6月23日-7月20日,在银川市“中山公园和森林公园”试验区域(样地区域),选择柽柳(Tamarix chinensis)、臭椿(Ailanthus altissima)、垂柳(Salix babylonica)、金叶榆(Ulmus pumila)和侧柏(Platycladus orientalis)5种典型城市树木为样木(侧柏和垂柳样木3株,其余树种样木各4株)进行液流监测。应用热扩散液流探针(TDP-30,TDP-50)在每株树树干北侧距离地表1.3 m高度测定树干液流速率,每30 s测定1次,每10 min取平均值存入数据采集器;在中山公园设置自动气象站实时监测气象因子(太阳总辐射、空气温度、空气相对湿度、降雨量),每10 min采集1次数据。以日均液流速率、日均耗水量为评价指标,评价不同树种间日均耗水的差异性;构建液流速率与太阳总辐射、饱和水汽压差之间的回归模型,评价总辐射、饱和水汽压差对液流速率的影响;分析银川市典型城市树木蒸腾耗水特性及其受主要气象驱动力的影响。结果表明:5种典型城市树木日均液流速率均呈现“单峰型”;金叶榆液流启动时间最早(06:30),且液流高峰持续时间最长(8.17 h);臭椿启动时间最晚(08:40);而柽柳的高峰持续时间最短(3.33 h)。侧柏的日均液流速率峰值最大(14.42×10^(-4) cm·s^(-1)),而柽柳的日均液流速率峰值最小(2.05×10^(-4) cm·s^(-1))。不同树种日均耗水量存在显著差异,日均耗水量由大到小依次为垂柳、侧柏、金叶榆、臭椿、柽柳;5个树种的液流速率都呈现出随总辐射的升高而快速升高,随后逐渐平稳甚至出现下降趋势;饱和水汽压差与5个树种的液流速率均呈现显著正相关。

From 23 June to 20 July 2021,five typical urban trees(Tamarix chinensis,Ailanthus altissima,Salix babylonica,Ulmus pumila and Platycladus orientalis)were selected as sample trees for sap flow monitoring in the“Zhongshan Park and Forest Park”experimental area(sample plot area)in Yinchuan City(three sample trees of Platycladus orientalis,three sample trees of Salix babylonica and four sample trees of each of the other tree species).The thermal diffusion sap flow probe(TDP-30,TDP-50)was used to measure the trunk sap flow rate at a height of 1.3 m above the ground on the north side of each tree trunk.The measurements were taken every 30 s and averaged every 10 min and stored in the data collector;an automatic weather station was set up in Zhongshan Park to monitor meteorological factors(total solar radiation,air temperature,relative air humidity,rainfall)and data were collected every 10 min.The average daily sap flow rate and average daily water consumption were used to evaluate the differences in average daily water consumption between different tree species;regression models between sap flow rate and total solar radiation and saturated water vapor pressure deficit were constructed to evaluate the effects of them on sap flow rate;the transpiration water consumption characteristics of typical urban trees in Yinchuan City and their influence by the main meteorological drivers were analyzed.The results show that the daily average sap flow rates of the five typical urban trees are“unimodal”;the Ulmus pumila had the earliest sap flow initiation(6:30)and the longest peak duration(8.17 h),the Ailanthus altissima had the latest initiation(8:40)and the Tamarix chinensis had the shortest peak duration(3.33 h).The highest peak daily sap flow velocity was observed in Platycladus orientalis(14.42×10^(-4) cm·s^(-1)),while the lowest was observed in Tamarix chinensis(2.05×10^(-4) cm·s^(-1)).The average daily water consumption of different tree species differed significantly,in descending order of Salix babylonica,Platycladus orientalis,Ulmus pumila,Ailanthus altissima,and Tamarix chinensis.The sap flow velocity of all five species showed a rapid increase with the increase in total radiation,followed by a gradual stabilization or even a decline.Vapor pressure deficit(VPD)showed a significant positive correlation with sap flow velocity in all five tree species.