Local Scale Impacts Of Different Land Cover Types On Climatic Factors

The types of land cover lie mainly on vegetation covers on the fieldsurface,as are the results of land use and its embodiment of externalmodality.They represent specific properties and tendencies in a certain timeand space and reflect ecological environment situation in a region.Differenttypes of land cover affect the contribution of moisture and heat quantity on thefield surface and finally influence the changing of climatic elements.Theeffects of different types of land cover on climatic elements have importanttheoretic and practical significances because climatic elements are the mostimportant ecological environment factors which influence human being's lifeand production.Based on field observation and parallel observation,the climatic elementssuch as air temperature,air relative humidity,intensity of illumination,windspeed,ground temperature and soil moisture content were mensurated in thispaper in different land cover (forest land,grass land and uncover land),differentweather(typical fine weather and overcast day)and different seasons(spring,summer,autumn and winter) from January to December in the year2004.The effects of different land cover on climatic elements were analyzedseriatim with qualitative analysis,variance analysis and correlationanalysis.The results were as follows.1.The maximal value of air temperature at the height of 150cm occurredat 14:00 on forest land and grass land in the same weather;while the valueoccurred at 13:00 on uncovered land.During the period of the observation,theair temperature showed the smallest daily range on forest land whileuncovered land the largest.There was a close correlation for 0cm groundtemperature and 150cm air temperature between forest land,grass land anduncovered land by correlation analysis.2.There were significant differences for 0cm ground temperature and150cm air temperature between forest land and grass land in differentweather(fine weather and overcast day)by the test of the significance ofdifference.In fine weather,the daily range rule of air temperature at the heightof 150cm was uncovered land>grass land>forest land; while in overcastday,the daily range rule was grass land>uncovered land>forestland.Therefore,no matter fine day or overcast day, forest land showed thesmallest daily range of air temperature at the height of 150cm. 3.For forest land with low crown density(40%),the air temperatureincreased with the height and in the daytime,the upper part showed the highestair temperature,close to ground part take second place,the middle partlowest;for high crown density(70%)areas,the air temperature rose up steadilyand obviously with the height.The correlation analysis for daily range ofground temperature and air temperature in forest land with different crowndensity revealed notable correlation.As for grass land,the maximal groundtemperature and the day temperature range both reduced with the rising of thecover degree,and the occurrence time for the maximal air temperature at thesame height postponed correspondingly.There was an extremely remarkabledifference between 0cm ground temperature and 150cm air temperature indifferent height grass land by correlation analysis. 4.The rule for air temperature was uncovered land>grass land>forest landin summer and forest land>uncovered land>grass land in winter.During thetransformation process from spring to summer,the air temperature on grassland exceeded gradually that on forest land,and the air temperature onuncovered land showed the maximal value;in the transformation process fromautumn to winter,the reverse.The correlation analysis for ground temperatureand air temperature on forest land,grass land and uncovered land in differentseasons all revealed notable correlation. 5.In the same weather,the air relative humidity on the forest land withdifferent crown density reduced with the increase of height,while theoccurrence time of minimal value postponed with the increase of crowndensity;the air relative humidity increased with the height,but in the upperlayer this trend reversed;there was a similar tendency for daily range of airrelative humidity on different height grass land,that is,decrease first and thenincrease,and the minimal value occurred at about 14:00. 6.In the transformation process from spring to summer,the air relativehumidity on forest land exceeded gradually that on grass land;in summer,therule of air relative humidity was forest land>grass land>uncovered land;in the...