油松、侧柏深秋边材木质部液流变化规律的研究

SAP FLOW FLUCTUATIONS OF PINUS TABULAEFORMIS AND PLATYCLADUS ORIENTALIS IN LATE AUTUMN

利用热扩散式边材液流探针和多种气象、土壤因子传感器组成的全自动数据采集系统 ,于深秋季节对北京西山地区低山成龄油松和侧柏林内单株边材液流速率、单木整株耗水量连日变化进行了系统观测。油松和侧柏边材液流每日 8:0 0以后启动 ,并逐渐增强 ,至 13:0 0～ 15 :0 0前后达到高峰 ,然后下降 ,18:0 0以后液流运移缓慢 ,至来日日出前后达到最低值。相同测定部位的边材液流速率 ,侧柏明显高于油松。油松树干不同部位边材液流日变化和连日变化趋势相同 ,但上部边材液流启动早 ,上升幅度大 ,到达峰值后即急剧下降 ,峰形窄而高 ;下部边材液流较上部明显延迟 ,且峰形平缓 ,峰值较低 ;测定期间油松树干上位和下位累计日周期和累计连日边材液流通量基本相同。进入 11月以后 ,单株日耗水量逐日降低 ,11月 6日油松日耗水量下降为 5d以前的 1 5 ,同期侧柏日耗水量已近于 0。油松和侧柏单木日耗水模型为三次曲线。边材液流的连日变化深受太阳辐射、气温、空气相对湿度、风速、土壤温度等因子的影响。利用线性回归方法建立了边材液流速率与环境因子关系的多元线性模型 ,影响边材液流速率的主导因子是 5cm和 2 0cm土壤温度、太阳辐射强度、空气湿度和风速。回归方程达到极显著水平。

By using auto data collection system with thermal dissipation sap flow probe, meteorological and soil sensors, diurnal and daily sap flow velocity (SFV) and whole tree water consumption of Pinus tabulaeformis and Platycladus orientalis were measured in late autumn from Oct. 27 to Nov. 9 in the West Mountains of Beijing. Results showed that diurnal SFV started from 8:00, and ascended to the peak during 13:00～15:00, then went down to the valley after 18:00. SFV of P. orientalis was much higher than that of P. tabulaeformis at the same lower position. Diurnal fluctuation of SFV on lower and upper trunk positions of P.tabulaeformis was similar, but the starting time of SFV on upper trunk position was much earlier, and the SFV peak was higher and thinner compared with lower trunk position. Progressive daily and diurnal sap flux on lower and upper trunk positions were approximately equal during measuring period. Daily water consumption (DWC) gradually descended in November. DWC of P. tabulaeformis in Nov. 6 was only 1/5 of 5 days ago, and DWC of P. orientalis was nearly 0 at the same time. Diurnal SFV was deeply affected by environmental factors such as solar radiation, air temperature, air humidity, wind speed and soil temperature. Multiple linear models of sap flow velocity and environmental factors were developed at significant level,of which the important factors were soil temperature in depths of 5 cm and 20 cm, solar radiation, air humidity and wind speed. Models of daily whole tree water consumption of P. tabulaeformis and P. orientalis were cubic curves.