| Targeting at sap flow velocities(SFV) and foliarδ13C value, the characteristic of three mid-subtropical dominant species (Cunninghamia lanceolata, Schima superba and Castanopsis fabri) in Wanmulin Nature Reserve of Fujian Province were respectively measured by using thermal dissipation probe method and stable carbon isotope technic. Meanwhile, the related environmental factors were also associated with, including photosynthetically active radiation, air temperature and relative air humidity recorded continuously by using automatic weather station, so as to probe deeply into the adaptation mechanism of conifer and broad-leaves species in mid-subtropical forest ecosystem of the three particular kinds of dominant species(Cunninghamia lanceolata, Schima superba and Castanopsis fabri).The results showed that:(1) The overall sap flow velocities trend of the three dominant species varies in different seasons. The mean and peak value of sap flow velocities of Cunninghamia lanceolata was continuously increased from non-growing season to growing season, and the mean value from 0.65±0.82cm-h-1～2.40±2.94cm-h"1, the peak value from 1.55cm-h-1～8.10cm·h-1;while Schima superba and Castanopsis fabri were presented as increased at first and then decreased from non-growing season to growing seasons, and the mean and peak value respectively expressed like these, Schima superba from 3.50±4.56cm-h-1～8.09±9.69cm·h-1,12.20cm·h-1～25.45cm·h-1; Castanopsis fabri from 3.41±3.57cm-h"1-7.11±7.39cm·h-1,13.32 cm·h-1～19.35cm·h-1. The start-up time for sap flow velocities of the three dominant species started earlier and the durations lasted longer in growing seasons than in non-growing season during the daytime. No matter in non-growing season or growing season, the average and peak value of sap flow velocities of the two broad-leaves species were much higher than conifer.(2) Under the circumstance of sunny weather, the correlation between the three dominant species and environment was as follows:water vapor pressure deficit>relative humidity>solar radiation>air temperature. Under the circumstance of cloudy weather, except Castanopsis fabri's more sensitive to solar radiation, the other two were impacted the most by relative humidity, but all three were impacted the least by air temperature. Under the circumstance of rainy weather, the influences affected by environmental factors, water vapor pressure deficit and solar radiation were respectively as follows:basically the same, the most sensitive and least sensitive.(3) The foliarδ13C value of two kinds of broad-leaves species (Schima superba-30.85%o and Castanopsis fabri-32.55%o) were lower than conifer species (Cunninghamia lanceolata -29.46%‰), whereas the transpiration rate of Schima superba and Castanopsis fabri were higher, with the mean SFV value respectively as six or five as Cunninghamia lanceolata. Due to lower WUE and higher transpiration rate, the two kinds of broad-leaves species had faster growth rate, which meant a significant competitive edge of Schima superba and Castanopsis fabri under the circumstance of plenteous sunshine and moisture.The results revealed the characteristic of water physiological and ecological on conifer and broad-leaves species especially in mid-subtropical natural forest ecosystems, reflected the differences trait of water use on conifer and broad-leaves species, which provide theory basis for exploring mid-subtropical evergreen broad-leaved secondary succession in both physiological and ecological aspects.
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