不同覆被下的温度日变化特征及空间尺度效应——以贵州陈旗小流域为例

DAILY TEMPERATURE CHARACTERISTICS AND EFFECT OF SPATIAL SCALE FOR DIFFERENT TYPES OF VEGETATION——A CASE STUDY OF CHENQI CATCHMENT IN GUIZHOU PROVINCE

选择贵州陈旗流域内具有典型性的4种植被类型(林地、玉米地、灌丛和草地),采用地温计,Hobo压力式水位温度记录仪和手持红外热像仪(FLIR SC620)观测和分析温度垂向和空间日变化特征。结果表明:林地和灌丛垂向温度从冠层向地表明显降低,地表与冠层气温差异大;玉米地和草地的地表气温高于冠层,温度垂向特性与林地、灌丛不同;土壤平均温度及变幅,林地<草地<玉米地,以及林地<灌丛;地表温度及变幅,林地<玉米地<草地,以及林地<灌丛;冠层温度及变幅,林地和灌丛、林地和玉米地差异不大;林地对垂向气温调节能力大于灌丛;玉米地对气温调节能力弱与林地,强于草地;同时,平面空间上,温度差异显著,其空间温度的变幅随平均温度值的增大而增大。

Temperature is one of the most important factors for microclimate affecting the growth of vegetation.Vegetation types,in turn,also have great influence on temperature spatial characteristics.The aim of this paper is to evaluate the microclimatic characteristics of four types of vegetation though field observation.We recorded vertical temperature,spatial temperature and other microclimatic parameters at two sites in Chenqi,a typical small karst catchment located in Guizhou province,compared and analyzed the characteristics of distribution and daily changes of temperature on four types of vegetation which are forestland,bush,cornfield,and grassland.The data recording was carried out by geothermometer,HOBO temperature data logger and hand-hold infrared thermal imager(FLIR SC620)on 8/13/2013 and 8/15/2013.It was found,for each vegetation type,that canopy height,coverage and structure played key roles in creating its own microclimate.Different types of vegetation had affected temperature to varying degrees from canopies to ground.The vertical profile temperature of forestland and bush significantly reduced from canopies to ground and the difference between their air temperatures was large.For cornfield and grassland,the ground air temperature was the highest which indicated that their vertical characteristics were different from forestland and bush.The average of soil temperature and its changing amplitude followed the order of forestland< grassland<cornfield and forestland< bush.Ground temperature and its changing amplitude followed the order of forestland < cornfield < grassland and forestland < bush.Canopy temperature and its changing amplitude did not have remarkable difference between forestland and cornfield at site 1,or between forestland and bush at site 2.With regard to regulation of vegetation on temperature,forestland had a strong effect on vertical temperature.Bush's capability of regulation for vertical temperature resembles forestland,but was weaker on microclimate than that of forestland.Cornfield's influence on vertical temperature was weaker than forestland,but was stronger than grassland.On the other hand,spatial temperature was observed by thermal infrared imager within approximately 5 square meters area selected from four samples of vegetation area with certain representativeness,for example,vegetation coverage,illumination intensity and humidity etc.The spatial temperature,as we found,changed significantly and its variation amplitude increased with the increase of plane mean temperature. The results suggest that the difference of vegetation types and spatial characteristics of temperature should be taken in to consideration,when studying the processes of evapotranspiration and photosynthesis in small scale.