关键词: 红松, 树干液流通量, 热扩散技术, 环境因子

Abstract:

In a 42-year-old Pinus koraiensis plantation in Maoershan Forest Ecosystem Research Station,3 representative trees each of dominant,intermediate and suppressed trees were selected and sap flux density was measured using thermal dissipation probe (TDP) method from May 29 to October 30,2004. Meanwhile,the related environmental factors,including air temperature,air relative humidity,soil relative humidity,photosynthetic active radiation (PAR) and global radiation were simultaneously measured with various sensors attached to Campbell Scientific dataloggers (CR23X). The sapwood thickness of another 40 trees selected based on diameter distribution in the stand was measured with tree coring method for developing the relationship between sapwood area and diameter at breast height (DBH) A=8.032DBH-46.95(R²=0.82,P<0.001). The result showed that the sapflow density in a sunny day exhibited a mono-peak diurnal pattern with its maximum occurring between 12:00 and 14:00,while that in cloudy and rainy days had no clear diurnal pattern with irregular peak values and even had night-time sapflow signals. In sunny days,the daily maximum sapflow density was in an order of dominant > intermediate > suppressed trees. However,the difference among the tree crown classes decreased in cloudy or rainy days. There was an obvious growing seasonal pattern in daily sapflow flux,in which the daily sapflow flux showed a magnitude order of dominant > intermediate > suppressed trees and declined with the growing season processing. Correlation and stepwise regression analyses indicated that the main environmental factors influencing sapflow density in the growing season were vapor pressure deficit and photosynthetic active radiation. Scaled up from sapflow measurements and sapwood area (89 436.94 cm²·hm^-2 in total) in the stand,the total transpiration from the Korean pine stand during the growing season was 678.95 t·hm^-2 ,of which the dominant,intermediate and suppressed trees accounted for 54.83%,35.68% and 9.48%,respectively. The mean daily transpiration of the dominant,intermediate and suppressed trees was 0.06～1.42 t,0.014～0.83 t and 0.017～0.25 t,respectively.

Key words: Pinus koraiensis, sapflow flux, thermal dissipation probe, environmental factors