| The Northeast China is one of typical regions experiencing intensive humanactivities within short time worldwide. Particularly as the significant changes offarmland and forest, there were typical characteristics of pattern and process ofagroforestry ecotone change. The intensive land use change of agroforestry ecotonehas made significant change for regional land cover, which had significant impact onthe regional climate system elements and the interactions among them, and modifiedthe distribution pattern of regional precipitation, temperature, etc. Research about thepatterns and processes of these changes is representative at the regional LUCC andclimate change researches, which would enrich typical case studies for global researchon a larger scale, and service for regional development in Northeast China.Based on the summary of domestic and international researches concerning onland use change and its climate effects, this paper takes agroforestry ecotone inNortheast China as study object, and establishes temporal and spatial land use changedata of1950s,1970s and2010year. Then multi-researches are carried out includingland use change analysis and climate simulation with WRF model to study the landuse change pattern and its climate effect of agroforestry ecotone. Several conclusionsare obtained:Firstly, the spatial distribution of agroforestry ecotone in Northeast China hassignificant changes in the past few decades. The paper takes Northeast China as basicstudy area, and identifies several ecotones in Northeast China based on land use datafrom remote sensing images and topographic maps, and analyzes the temporal andspatial change and characteristics of agroforestry ecotone. In Northeast China, theagroforestry ecotone could be classified into two types, agroforestry ecotone at forestedge and agroforestry ecotone inner forest, the differences between them rest withregional geomorphological and climatic characteristics, forming into different landuse pattern. The primary ecological problem in agroforestry ecotone is soil erosion.The natural environment determines the vulnerability of land system in agriculturedevelopment.The landscape characteristics of agroforestry ecotone are significantly differentfrom other ecotones, and landscape profiles at different location of agroforestryecotone in Northeast China showes different land use patterns. Five landscape profilesare extracted in different locations of typical agroforestry ecotone in Northeast China.The land use pattern analysis of different profiles showes that different parts of agroforestry ecotone have different land use pattern and process. Then landscapeindex and two environment factors are introduced to compare the landscapeheterogeneity differences and changes of agroforestry ecotone and other ecotones insoutheastern Greater Khingan Mountains. The results show that:(1) the slope ofprimary transition zone between farmland and forest is2.5-7.5°,(2) from1978to2010, the changes of the edge density (ED) and core area index (CPL) show that theregion with slope between2.5-10°has the highest degree of fragmentation for forestlandscape,(3) according to the change of ED curves besides the peak value between1978-2010, the deforestation has a trend to move toward areas with greater slope,(4)The aridity index of different ecotones and different location is significantly different,and the agriculture land in agroforestry ecotone is the most humid area all over theregional agriculture land.With the support of GIS technology, the temperature values from WRF modelwith different resolutions are analyzed from spatial scale view. The comparisonanalysis between the meteorological stations observed values with WRF model outputwith different resolutions indicats that, with the improvement of the spatial resolution,the deviation between the site observations and WRF model output value is gettingsmaller. As the resolution increases, more detail is portrayed, while the informationincrease from3km to1km is limited. Elevation is the most important factorinfluencing local temperature distribution. This paper uses high-resolution DEM todownscale the temperature distribution with9km spatial resolution to3km spatialresolution. Compare with the WRF output, downscaled data could reflect the basictrend of temperature changes in3km resolution, while detail changes are very rough.Besides, this paper takes temperature with1km spatial resolution as dependentvariable, and the longitude, latitude, altitude and topographic factors as independentvariables, where the topographic factor is the combined effects of slope and aspect, toanalyze of the relationship between temperature and these factors. Distribution ofregression residuals reflects the contribution of the vegetation, soil, small-scaleatmospheric processes to temperature distribution pattern.The temperature time series analysis of Nenjiang River basin shows that, therewere overall rising trend, local fluctuations and cycles of5-12years and21years foraverage temperature in July of last60years. The temperature sensitivity to land coverchange analysis based on WRF model shows that, the land cover change between1950s and1970s results a warming effect, and land cover change between1970s and2010year results a cooling effect in agroforestry ecotone of Nenjiang River basin.Comparing with the air temperature, land surface temperature changes are much moresignificant and sensitive to land cover changes. At the same time, the warming orcooling effect of land cover change is more significant in the region scale rather thanspecific land cover area. The comprehensive simulation analysis combining climatechange and land cover change shows that, the temperature increased between1951 and1978, but the increase is lower than the warming effect of land cover change. Thetemperature increased significantly between1978and2010, but it is the result afterthe offset by the cooling effect of land cover change, and the regional warmingtendency was stronger.
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