橡胶林生态系统干季微气候特征和通量的初步观测

Characteristics of Microclimate and Flux of a Rubber Plantation Ecosystem in Dry Season of Hainan Island,South China

应用微气象法中的梯度观测系统、涡度相关系统和闭路水汽-CO2廓线系统,使用设置在海南省西部儋州地区一片刚开割的橡胶林中观测铁塔上的观测仪器所得的干季7个晴好天气的微气候观测数据和通量观测数据,对其微气候特征和通量特征进行初步分析研究。结果表明:(1)橡胶林的辐射通量与光合有效辐射(photosynthetically active radiation,PAR)呈明显的昼夜交替变化;橡胶林林内和林冠上风速昼夜变化明显,风向则多为东北风(15°～40°);林冠上方气温和树冠面表温具有显著的日变化特征,树冠表温日变化幅度大于气温;相同时刻干季橡胶林林冠上方和林冠内湿度和水汽压相差不大;林冠内CO2浓度夜高昼低;土壤温度日变化明显,土壤含水量变幅较小。(2)林冠上方显热通量与潜热通量变化趋势相同,显热通量小于潜热通量;净辐射通量日变化呈规则的倒"U"形,主要由下行短波辐射决定;土壤热通量存在日变化,随土层深度增加变化变小;CO2通量随光合有效辐射发生日变化;水汽通量随净辐射发生日变化。

Tropical rubber plantation forests play a great role in the tropical terrestrial ecosystem,however,little is known about its effects on its ecological characteristics and carbon cycle,and there are much controversy about it.The flux tower of Danzhou Key Field Station of Observation and Research for Tropical Agricultural Resources and Environments,Ministry of Agriculture（Danzhou Field Station）,was built in the end of 2009 to study the ecological functions of rubber plantation.Based on the gradient observation method,by using eddy covariance system and closed-path water vapour-CO2 profile system on a 50 m tower in a tapping rubber plantations in Danzhou,Hainan Island,7 clear days data about microclimate factors and fluxes data in dry season were used to analyze the characteristics of them.The results showed that as follows：（1） There had significant characteristics of daily alternation in radiation flux and PAR（photosynthetically active radiation）of rubber plantation.Wind speed under and above the canopy of rubber plantation had obvious alternation and but wind direction above the canopy with more northeast wind（15°～ 40°）.There had significant characteristics of daily variation in air temperature and canopy surface temperature,moreover,the daily range of canopy surface temperature was larger than that of air temperature.In the same time of the dry season,relative humidity and water vapour pressure above and under the canopy of rubber trees varied little.CO2 concentration increased at night and decreased in the daytime.And the soil temperature had obvious daily variation,but the daily range of the soil water content was especially small.（2）The sensible heat flux and the latent heat flux had the same daily change,and the former was less than the latter.The net radiation flux had the rule inverted＂S＂daily variation,and it was determined by the downwelling shortwave radiation.The soil heat flux had daily alternation too,and the amplitude went less with the depth increasing.The CO2 flux was changing with the PAR and the water vapor flux with the net radiation above the rubber plantation canopy in a daily scale.