北京山区典型人工林的耗水规律

在我国的北方地区植被与水资源之间的关系是森林植被构建的关键性问题.如何依据水分条件的承载力,构建水分稳定的森林植被是一项重要研究.以北京妙峰山侧柏、油松为研究对象,应用大型可称量式蒸渗仪测定林木个体耗水规律,并在此基础上进行尺度扩展,分析2种林分群体耗水特征.研究发现：在晴天条件下,侧柏和油松蒸腾强度的日变化趋势均为单峰曲线;在典型阴天和雨天条件下,2树种间蒸腾速率差异明显,受云量动态变化影响,蒸腾强度的日变化趋势为多峰曲线.通过相关分析发现,在选定的环境因子中太阳辐射通量、大气水汽压饱和差、空气温度、土壤含水率和土壤水势均与林木蒸腾速率呈正相关,而空气相对湿度与林木蒸腾速率呈负相关.另外,利用边材面积作为尺度转换因子实现由单木到林分的尺度扩展,根据测定的样木蒸腾量,推算得出侧柏林6-9月总蒸腾量为321.43 mm,油松林的总蒸腾量为192.83 mm.

Water consumption of typical artificial forests in Beijing mountainous area

In North China, how to properly deal with the relationship between vegetation and water resources is one of the key problems for the forest vegetation construction. Hence, how to construct forest vegetation with high moisture stability based on the water bearing capacity is important. Taking Platycladus orientalis and Pinus tabulaeformis, two typical artificial forests as the research object, we measured the water consumed by individual trees with lysimeter installed in Miaofeng Mountain, Beijing. On the basis of the measured data, water consumption by forest stands was revealed. We found that in sunny days diurnal variation of transpiration intensity of two kinds of individual trees appeared as a single peak curve. However, in cloudy or rainy days the transpiration rate varied significantly between the two species. Correlation analysis showed that among environmental factors, solar radiation flux, vapor pressure deficit, air temperature, soil water content and soil water potential were positively correlated with transpiration intensity, while the relative humidity was negatively correlated with transpiration intensity. By using tree sapwood area as transform scalar, based on the measured transpiration rate of sample trees, the transpiration quantity of forest stand was calculated. From June to September, transpiration by the forest stand of Pinus tabulaeformis was 321.43 mm and that of Platycladus orientalis 192. 83 mm.