Effect And Mechanism Of Land Cover Change On Climate Change In Heilongjiang Province During 1900s?2010s

During the past several centuries,humans have altered the Earth's environment with unprecedented intensity and speed through land use change.Land Use and Land Cover Change(LUCC),one of the most important anthropogenic activities,affect local and regional climate through altered the near-surface properties such as albedo and roughness length,and result in changes in surface –atmosphere flux of water and energy.Land use forcing is considered as a very important aspect in the anthropogenic impacts on climate.Heilongjiang Province is one of typical regions that experiencing intensive human activities with in short time and fastest-warming in China.Research about the patterns and processes of these changes is representative at regional LUCC and climate change research,which would enrich typical case studies for global research on a larger scale,and contribute to a better understanding of the coupled relationship between land use/cover change and climatic change caused by human activities.Based on the summary of domestic and international researches concerning on land use change and its climate effects,this paper focuses on the processes of land use/cover change and its impact on climate change.Combined the statistical analysis(OMR),spatial analysis and regional climate model(WRF),this paper mainly to reveal the temporal and spatial characteristics of land use change caused by human activities,discuss the effect,contribution and mechanism of land use/cover change to climate change in qualitative.This study provide some useful experiment basis and academic foundation to enrich the theory and practice of regional environmental changes,realize regional sustainable development,and facilitate the harmonious development between human and nature.The main contents and conclusions of the paper are as follows:(1)Based on historical document and maps,remote sensing images,this paper reconstructed the land use and land cover in 1900 s,1950s and 2010 s of Heilongjiang Province firstly.Then the temporal and spatial characteristics of land use change was analyzed in the past century.The results show that: the spatial distribution of land use types in Heilongjiang province has significant changes during 1900s~2010s.The major land use change process were that the forest,grassland and wetland were transformed into cropland.The area of land use change cover about 48.01% of the Heilongjiang Province.The structure proportion of forest,cropland,grassland and wetland converted 63:5:20:12 to 47:37:6:7:2.(2)The land cover change has positive influence on air temperature variation with spatial and season differences.The temperature had good regionalized variable characteristic and spatial structure caused by land cover change: in the north,west and south regions of Heilongjiang Province show the most obvious spatial characteristic.The major transformation type was forest to grassland in the northern areas of Heilongjiang Province,and it show the increasing temperature trends;the major transformation type were grassland and wetland to cropland in the western and eastern areas of Heilongjiang Province respectively,and they show the decreasing temperature trends.The southern areas of Heilongjiang province show the increasing temperature trends with building land.(3)This paper presents temperature trends with land use/land cover change in different degree of the aggregation in Heilongjiang Province with MATLAB.A fitting equation of temperature trends and the degree of the aggregation of land use cover is built.The results show that in different degree of the aggregation of land use types present different temperature trends.The cropland show warming effect,and the higher degree of the aggregation of cropland,the quicker the temperature increased.Relationship between the degree of the aggregation of forest/grassland/wetland and the temperature trend were nonlinear.The temperature increasing rate with the increasing of fractional forest cover.The warming effect of forest accelerated with the more fractional forest cover,and reached the most warming effect at the fractional of 72.22%.And the temperature decreasing rate with the increasing of fractional grassland and wetland cover.The cooling effect of grassland(wetland)accelerated with the more fractional grassland cover,and reached the most cooling effect at the fractional of 90%(60%).(4)This paper studied the effects of LUCC on surface air temperature over Heilongjiang Province in the last century,we found that LUCC resulted in a cooling effect of local temperature,but with spatial differences and seasonal differences.The mean cooling of about 0.415 ? occurred in Heilongjiang Province from 1900 s to 2010 s,and LUCC contributed about 25.57 percent to mediate climate warming in Heilongjiang Province.In seasons,LUCC results in a cooling effect in winter,spring and summer.Autumn showed a contrary tendency that LUCC results in a warming effect.As the typical representation of LUCC in Heilongjiang Province over the past century,the transformation types of grassland and wetland conversion to cropland show the warming effect,but the forest conversion to grassland and cropland show the cooling effect.The warming effect is slightly stronger for the wetland conversion to cropland than the grassland conversion to cropland,and the air temperatures have increased by about 0.024 ? and 0.023 ? repectively in the last century,the contribution of transformation types to climate warming in Heilongjiang Province is 1.94% and 1.88% repectively.The cooling effect is even stronger for the forest conversion to cropland than the forest conversion to grassland,and the air temperatures have decreased by about 0.103? and 0.009? repectively in the last century,the contribution of transformation types to slow climate warming in Heilongjiang Province is 7.86% and 0.71% repectively.Regional temperature change is affected by the LUCC in little degree.(5)LUCC dramatically altered the regional distribution of the surface radiation and energy balance in the past century of Heilongjiang Province.LUCC can bring about the reduction(addition)of the short-wave fluxe layers and sensible hear flux by increasing(decreasing)surface albedo,and results in surface temperature decreased(increased).