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水分供应不足及水热不同步常导致黄土丘陵地区在春末和夏初出现季节性干旱。为阐明该地区主要造林树种的蒸腾耗水特征及其对降水的响应,使用热扩散式树干茎流计(TDP)于2009年4–10月对黄土丘陵区安塞国家生态试验站刺槐(Robinia pseudoacacia)和侧柏(Platycladus orientalis)的树干液流密度(Fd)进行连续观测,并同步测定了气象、土壤水分等环境因子。结果表明:刺槐和侧柏在生长季内不同生长时期的Fd均表现为单峰型日变化特征,刺槐最高液流峰值为0.120 68m3·m~(–2)·h~(–1),是侧柏最高液流值(0.037 37 m~3·m~(–2)·h~(–1))的3.23倍。除生长旺盛季(7–8月)外,刺槐和侧柏降水后的Fd明显高于降水前。同时反映水汽压差(VPD)和太阳辐射(Rs)的蒸腾变量(VT)能够很好地模拟Fd,且两者呈显著的指数正相关关系,随VT的增加Fd逐渐增大,VT增加到50 k Pa(W·m~(–2))1/2左右时,Fd的变化趋于稳定;通过对降水前后两个树种水力导度(拟合参数b值)分析,相对于侧柏,刺槐更易受降水的影响(p<0.001)。因此,可认为刺槐是降水敏感型植物,而侧柏是降水不敏感型植物。该研究通过分析黄土丘陵区人工林树种对降水的差异性响应,从树木水分利用方面能够为当地生态恢复过程中人工林的管理提供科学依据。
Inadequate water supply and hydrothermal asynchrony often lead to seasonal droughts in late spring and early summer in the Loess Plateau. In order to clarify the characteristics of transpiration and water consumption of main afforestation tree species and their responses to precipitation in the region, heat-dissipating trunks stem-flow meter (TDP) was used to estimate the transpiration rate of Robinia amygdalus pseudoacacia and Platycladus orientalis were observed continuously and the environmental factors such as meteorology and soil moisture were simultaneously measured. The results showed that the Fd of Robinia pseudoacacia and Platycladus orientalis at different growth stages showed single peaked diurnal variation, and the highest peak of R. pseudoacacia was 0.120 68 m 3 · m -2 · h -1 Arborvitae maximum flow value (0.037 37 m ~ 3 · m -2 (-2) · h -1) 3.23 times. Except for the vigorous growth season (July-August), the Fd after precipitation of Robinia pseudoacacia and Platycladus orientalis was significantly higher than before precipitation. The transpiration variable (VT), which reflects both vapor pressure difference (VPD) and solar radiation (Rs), can well simulate Fd, and the two show a significant exponential positive correlation. The Fd increases with increasing VT 50 k Pa (W · m -2) 1/2, the Fd changes tended to be stable. By analyzing the hydraulic conductivity (fitting parameter b) of two tree species before and after precipitation, Black locusts are more susceptible to precipitation (p <0.001). Therefore, Robinia pseudoacacia is considered to be a precipitation-sensitive plant, while Platycladus orientalis is a precipitation-insensitive plant. In this study, by analyzing the different response of plantation tree species to precipitation in the hilly area of the Loess Plateau, this study can provide a scientific basis for the management of plantations in the process of local ecological restoration from the aspects of tree water use.