中文摘要：

使用周长传感器（Circumference DC2）研究了太行山南麓低山丘陵上栓皮栎人工林树干直径的日变化及其影响因子.结果表明：在季节性干旱期间,栓皮栎树干的直径变化周期性明显,直径收缩与液流启动时间基本一致,直径最小值滞后于液流速率最大值3～4h;栓皮栎直径日最大收缩量（MDS）呈现低-高-低的变化趋势,与累积液流通量和叶片水势日差值极显著相关,与土壤含水量呈显著的二次方程关系.MDS值受气象因子变化的影响,与温度日差值、蒸汽压亏缺日差值和相对湿度日差值显著相关,而与太阳辐射日差值的相关性不显著.连续降水后,土壤水分不再是栓皮栎直径变化的限制因子,MDS值与累积液流通量、叶片水势、土壤含水量和气象因子差值的相关性均不显著.季节性干旱期和雨季的土壤含水量和温度是影响树干直径日变化的主要因子.

英文摘要：

By using Circumference Dendrometer 2（DC2）,this paper studied the diurnal variation of trunk diameter in Quercus variabilis plantation at the south aspect of Taihang Mountains.During seasonal drought,the diurnal variation of Q.variabilis trunk diameter was quite evident.The time of the diameter shrinkage followed the start-up time of sap flow,but the appearance of the minimum trunk diameter lagged behind the maximum sap flow flux about 3-4 h.The maximum daily shrinkage（MDS） value of the trunk diameter presented a trend low-high-low,being significantly correlated with the diurnal differences of cumulative sap flow flux and leaf water potential and having a significant quadratic relationship with soil moisture content.The MDS value was affected by the variations of meteorological factors,being significantly correlated with the diurnal variations of air temperature,vapor pressure deficit,and relative humidity,but less correlated with the diurnal variation of solar radiation.After successive precipitation,soil moisture content was no longer the limiting factor of the diurnal variation of Q.variabilis trunk diameter.The MDS value had less correlations with the diurnal differences of cumulative sap flow flux,leaf water potential,soil moisture content,and other meteorological factors.Stepwise regression analysis indicated that the soil moisture content and air temperature in seasonal drought and rain seasons were the key factors affecting the diurnal variation of Q.variabilis trunk diameter.