晋西黄土区刺槐和油松树干液流比较

Sap flow in forests of Robinia pseudoacia and Pinus tabulaepormis by using TDP method

应用TDP(Thermal Dissipation Probe)热扩散探针技术,通过对晋西黄土区刺槐和油松进行一个生长季(2010-04—10)的野外实地定位观测,结合同步测定的大气相对湿度、大气温度、太阳总辐射等气象因子,研究刺槐、油松树干液流的日变化及季节变化规律。结果表明:1)刺槐在5月上旬仅产生微弱液流,日均液流速率小于油松,无明显昼夜变化规律,到5月下旬,日均液流速率超过油松,并与油松呈现相同的昼夜变化规律,2树种夜间存在一定的树干液流,液流速率均于09:00开始快速上升,到12:00左右达到峰值;2)8月刺槐日均液流速率均大于油松,2树种液流速率连日变化规律基本相同,液流速率开始快速上升和达到峰值的时间与5月基本一致,峰值分别为5月的1.79和1.49倍,月平均值分别为5月的3.01和1.48倍;3)刺槐、油松树干液流和月耗水量呈现明显的季节性变化规律,耗水旺季集中在6—9月,4月达到最小值,7月达到最大值,在整个生长季(4—10月),油松林的总耗水量是刺槐林的1.63倍。经回归分析可知,影响刺槐、油松液流速率的主要因子均为太阳总辐射。

Stem sap flow of Robinia pseudoacia and Pinus tabulaepormis trees on the Loess Plateau, western Shanxi Province, was measured with the thermal dissipation probe （TDP） method during the growing season from April to October, 2010. Combined with some concurrent meteorological factors, the diurnal and seasonal variations of stem sap flow of both species were comparatively studied. The model of sap flow and meteorological factors was established. The results showed that： 1 ） the sap velocity of R. pseudoacia was lower than that of P. tabulaepormis and no significant diurnal variation in early May. In late May, the average diurnal flow velocity of R. pseudoacia was higher than that of P. tabulaepormis. Their diurnal variations were similar, and their flow velocity began to increase quickly from 9：00am and peaked at about 12：00am. 2） In August, the average diurnal flow velocity of R. pseudoacia was also higher than that of P. tabulaepormis. Their diurnal fluctuations were approximately same, and the time when flow velocity began to increase quickly and peaked was basically identical with that in May, but the diurnal peak values were 1.79 and 1.49 times as much as that in May. The average value of flow velocity in August was 3.01 and 1.48 times as much as that in May, respectively. 3）Stem sap flow and monthly water consumption present seasonality law. Water consumption was high from June to September. Sap flow velocity reached a minimum at April and a maximum at July. From April to October during the whole growing season, the water consumption of R. pseudoacia was 1.63 times as much as that of P. tabulaepormis. The regression analysis revealed that the main affecting factors of sap flow velocity were solar total radiation and vapor pressure deficit for R. pseudoacia and solar total radiation and atmospheric temperature for P. tabulaepormis, respectively.