Research On Evapotranspiration And Influencing Factors Of Secondary Quercus Forest In Purple Mountain

This paper used secondary Quercus forest as research object, the ecological location stationis in Zhongshan Botanical Garden, Purple Mountain. According to instruments and tests, todeterminate the environmental ecosystem’s factors respectively-soil evaporation and Quercustree SAP flow–the purpose is calculating the amounts of forest evapotranspiration in PurpleMountain in2013. Based on the results, it can analysis some kinds of environmental conditionsof evapotranspiration and compare the differences among them. Also, calculate what are the themain factors affect to evapotranspirationin the ecosystem. In a whole, it can provide datainformation supporting of Quercus in Purple Mountain, and reveal the the impact of forestevapotranspiration in North subtropical on the urban water environment.(1)Measured up the data of forest evapotranspiration in Purple Mountain is687.5mm. andthe model of Rithchie and Zhang et al.’s AET methods are897.01mm and637.47mmrespectively. Particularly, in April, May, November and December, Rithchie`s measured valuesalready received the texting data, and in June and October, Zhang et al.’s values nearby reach themeasured data of evapotranspiration. Seasonal dramatic changes in plant transpiration are acutediversificate, and soil evaporation variations are gentle. In a word, solar radiation, air temperature,soil temperature, soil moisture, barometric pressure and dew point are the main environmentfactors that affecting the evapotranspiration in the Quercus.(2) The transpiration of Quercus’s leaves is a single-peak curve in spring and autumn. Andin summer, the rateis are higher than spring and autumn in diurnal variations, which meanstranspiration rate is higher. However, when there are similar temperature and humidityillumination conditions happened in different areas, lighting conditions became the mainlyeffecting factor of leaf transpiration rate. And there is a certain tolerance range of leaftranspiration rate changes, the higher the solar radiation and temperature are, the greatertranspiration rate is. When the temperature reaches a certain value range, parts of leaves’stomatas are closed, as a result, the physiological activity is decline, and it also leads to thereducing of transpiration.(3)The data of total annual transpiration of Quercus is435.71mm. The summer ratios nearlyreach50%percent. The whole Quercus fluid flow rates show that summer is higher than autumn,and autumn is higher than spring in flowing changes render. The lines are single-peaked curve. Itgradually increased over time in spring. And liquid flow rates downward to geranial trend overtime in autumn. This phenomenon showing that air temperature is a major factor that affecting stems SAP flow in spring and autumn. Quercus transpiration rates in sunny day are higher thancloudy day. And diameter height is main indicator to affect growth of Quercus.(4)Annual soil evaporation is426.02mm. The lines in four seasons is one-peak trendedcurve. Soil evaporation in winter is at the minimum value. And soil evaporation in spring’s peakis3.5times than winter, summer’s peak is5.7times, and autumn is2.3times. The highest monthof soil evaporation is July-average daily evaporation is2.11mm. And the lowest month was inJanuary-the soil daily evaporation is0.38mm.