Abstract:

Sap flow meters based on the stem heat balance method were used to continuously measure the sap flow of Phyllostachys edulis in the Forest Ecosystem Research Station in Dagangshan mountain, Jiangxi Province and in the meantime automatic meteorological stations were used to observe the meteorological factors from September, 2009 to July 2010. Results indicated that the average sap flow rate showed distinct diurnal change rhythms both in sunny and cloudy days in different seasons. The fluctuations of the daily sap flow rates were relatively mild from day to day in autumn and winter, while the fluctuations were relatively violent in spring and summer due to the influences by rainfalls. The sap flow usually displayed unmoral curves in fine days, however it sometimes showed bimodal curves in spring and summer, without significant "noontime depression" phenomenon. There was weak sap flow at nights regardless of seasons or weathers, likely driven by root pressure. The main meteorological factors influencing the sap flow varied in different seasons probably because of the different moisture absorption modes in different seasons. The sap flow was most related to air temperature during dormant time and most related to photosynthetic active radiation (PAR) in the growth season. The sap flow showed distinct seasonal dynamics and the rate was (97.88±5.73) g·h^-1, (52.27±3.66) g·h^-1, (167.81±20.15) g·h^-1 and (414.04±48.62) g·h^-1 respectively in the end of growth season, dormant period, early- and mid-phase of the growth season. Multiple linear regression matrix was established between the meteorological factors, regarding PAR, solar radiation, air temperature as independent variables, and sap flow rate of different seasons as dependent variables with high significance.

Key words: sap flow, seasonal changes, meteorological factors, Phyllostachys edulis