Transpiration Rates of Carex Meyeriana in Relation to Micrometerological Factors in a Mountain Valley Wetland

In order to reveal transpiration rates of wetland plants and its relationships to micrometerological factors in a mountain valley wetland, relative humidity, air temperature, leaf temperature, soil temperature, photo flux density and transpiration rates were measured once two hours in a Carex meyeriana wetland of the Changbai Mountain valley in dry (July) and wet (September) of 2003, respectively. Results showed that the tendency of "decreasing after increasing" was obvious in wet season. However, a relatively stable trend was observed for the transpiration in dry season. Generally, the photon flux density of Carex meyeriana was higher in wet season than that in dry season. However, the variabilities of leaf temperature, air temperature and relative humidity were similar in both seasons. Higher transpiration rates of Carex meyeriana leaves were observed in July (varied from 40 to 150 mol·m⁻²·s⁻¹) compared to those (varied from 7 to 14 mol·m⁻²·s⁻¹) in September. Transpiration rates were significantly correlated with air temperature (P < 0.01), leaf temperature (P < 0.01), and wind speed (P < 0.05), but correlationship between relative humidity and photo flux density was not significant (P < 0.05).