半干旱地区城市环境下樟子松蒸腾特征及其对环境因子的响应

Transpiration of Pinus sylvestris var. mongolica and its response to urban environmental factors in semi-arid area

作为我国半干旱地区重要的造林绿化树种之一,樟子松在城市林业建设中被广泛使用,研究樟子松在半干旱地区城市环境下的蒸腾耗水及其环境响应对于城市森林建设具有重要的理论意义和应用价值。从2012年8月至10月,以位于内蒙古呼和浩特市树木园内的30年生樟子松为研究对象,按照其径阶分布,选定8株样木,采用热扩散探针法对其树干边材液流进行了连续动态监测,并采用小型自动气象站和土壤水分传感器同步连续测定小气候因子与土壤含水量动态变化。结果表明:在不同天气条件下,樟子松树干液流密度日变化存在差异,晴天时液流密度曲线表现为单峰曲线,且液流密度较大,阴天与雨天液流密度相对较小;液流密度的大小与供试树木胸径无显著相关关系(P>0.05);太阳辐射(r=0.731,P<0.01)和大气饱和水汽压亏缺(VPD)(r=0.877,P<0.01)是影响樟子松蒸腾的主要因子,风速与液流密度极显著相关(P<0.01),但相关系数仅为0.518;土壤水分并未显著影响液流密度(r=-0.071,P>0.05)。以太阳辐射Ra、VPD作为自变量建立的模型能够分别解释樟子松68%、71%的液流变化。

As one of the most important afforestation and greening tree species in the semi-arid area of China, Pinus sylvestris var. mongolica has been widely used in development of urban forests. Study on the transpiration of Pinus sylvestris var. mongolica and its response to environmental factors has essential theoretical significance and application value for urban forestry practices. Using the thermal dissipation probes （TDP） method, sap flow of Pinus sylvestris var. mongolica was monitored at the Hohhot Arboretum, Hohhot, Inner Mongolia, China from August to October in 2012, and environmental factors were measured simultaneously by using a portable automatic weather station and soil moisture sensors. Daily transpiration of trees varied with weather conditions. During sunny days, the transpiration rate curve showed a single peak, and the transpiration rate was higher than that on the cloudy or rainy days. The transpiration rate was not significantly correlated with the diameter of the tree trunk at breast height （P〉 0.05）. The main meteorological factors controlling the sap flow were solar radiation （r= 0.731, P〈 0.01） and vapor pressure deficit （VPD） （r= 0.877, P〈 0.01）. The correlation coefficient between the sap flow and wind speed was significantly low （r= 0.518, P〈 0.01）. In addition, the soil water content did not influence the sap flow significantly. We concluded that VPD and solar radiation can explain 71% and 68%, respectively, of the daily sap flow change.