中文摘要：

摘要运用Granier热扩散式探针法，于2010年干湿季对鼎湖山自然保护区针阔混交林4种优势树种马尾松、锥栗、木荷和广东润楠的树干液流密度进行连续监测，并同步观测气温、相对湿度和光合有效辐射等环境因子的变化，研究其树干液流特征及其对环境因子的响应．结果表明：在干湿季，4种优势树种的树干液流速率日变化均呈“昼高夜低”的典型单峰曲线，阔叶树锥栗、木荷和广东润楠的平均液流速率和峰值以及日液流量均显著大于针叶树马尾松；马尾松、锥栗、木荷和广东润楠的最大树干液流密度分别为29．48、38．54、51．67、58．32gH2O·m^2·s^-1优势树种树干液流速率的变化与环境因子的昼夜变化存在时滞；液流速率变化与光合有效辐射、水汽压亏缺和气温等环境因子的变化呈显著正相关，其中湿季以光合有效辐射为主导因子，干季以气温为主导因子．

英文摘要：

Abstract： By the method of Granier＇ s thermal dissipation probe, the stem sap flow density of four dominant tree species （Pinus massoniana, Castanopsis chinensis, Schima superba, and Machilus kwangtungensis ） in a mixed conifer-broadleaf forest in Dinghushan Reserve of South China was con- tinuously measured in the dry season （November） and wet season （July） in 2010, and the environ- mental factors including air temperature, relative humidity, and photosynthetically active radiation （PAR） were measured synchronically, aimed to study the characteristics of the stem sap flow of the tree species in response to environmental factors. During the dry and wet seasons, the diurnal chan- ges of the stem sap flow velocity of the tree species all presented a typical single-peak curve, with high values in the daytime and low values in the nighttime. The average and maximum sap flow ve- locities and the daily sap flow flux of broad-leaved trees （ C. chinensis, S. superba, and M. kwang- tungensis） were significantly higher than those of coniferous tree （P. massoniana） , and the maxi- mum sap flow velocity of P. massoniana, C. valueschinensis, S. superba, and M. kwangtungensis was 29.48, 38.54, 51.67 and 58.32 g H20 ~ m^2.8^1, respectively. A time lag was observed between the sap flow velocity and the diurnal variations of PAR, vapor pressure deficiency, and air temperature, and there existed significant positive correlations between the sap flow velocity and the three environmental factors. The PAR in wet season and the air temperature in dry season were the leading factors affecting the stem sap flow velocity of the dominant tree species