| The program of Land Use and Land Cover Change(LUCC)and the Global Land Project(GLP)had led to that the research on the relationship between man and land became a hotspot which takes the human system and land system as the core and emphasizes their mutual influences and effects.More and more studies have shown that irrational land use activities accelerated the land degradation in the ecologically fragile areas.Western Jilin Province located in the agro-pastoral ecotone of Northeast China and the arid climate region,so its regional characteristics and unreasonable human activities led to the serious land degradation in Western Jilin.As the rural settlement is the most direct manifestation of human activities,its spatial pattern and evolution is an important part of LUCC research.In the past 50 years,the total scale of rural settlements in Tongyu County,a county in Western Jilin,has been continuously increasing,whereas the expansion and shrinkage of rural settlements coexisted in space.At the same time,the land salinization around the rural settlements is becoming more and more serious,and their mutual effect reflects relationship between human activities and land degradation.Therefore,it is necessary to explore that how the human activities influence on and interact with land degradation in the eco-fragile areas,and analyze the coordination of the relationship between people and land,to achieve the sustainable utilization of land and the protection of ecological environment in the eco-fragile area.In this paper,with the rural settlement evolution representing intensity and dynamic process of human activities,and with the dynamic changes of saline-alkali land representing the process of land degradation,various statistical analysis methods,landscape pattern index and the spatial analysis technology were used to examine the spatial pattern and dynamic changes of rural settlements and saline-alkali land in Tongyu County and its secondary regions,as well as their influencing factors,then we explored the spatial coupling relationship between human activities and land degradation in the ecologically fragile areas.The main conclusions are as follows:(1)The scale of rural settlements in Tongyu County was increasing,meanwhile its spatial distribution was more and more uniform,and there were periodic and regional differences in the evolution of rural settlements.In the past 50 years,the scale of rural settlements in Tongyu County has continued to increase,but the rate of expansion has slowed down.In the first 40 years,the change of rural settlements was rapid and the intensity was large.During the period of 1965—2005,the total scale of rural settlements was increasing in all the towns,while in 2005—2015,increases and decreases coexisted in the scale of rural settlements of each town.In space,the changes of rural settlements in the towns with larger total land area were faster,while the changes of rural settlements in the towns with less rural settlements had larger intensity,and the regional differences were obvious.The distribution of rural settlements was from the relative balance between the towns to the uniform distribution of the whole county in Tongyu.In 1965,the spatial pattern of rural settlements showed large scatter and small aggregates,the differences of rural settlement scale between towns were small,and the distribution was not balanced.By 2005,with the shift of agglomeration districts of rural settlements,the spatial distribution of rural settlements developed to evenly in county.In 2005—2015,rural settlements increased slightly,but the spatial pattern of rural settlements has not changed.(2)The evolution of rural settlements was obviously influenced by social and economic factors,and it was also affected by the geo-graphical conditions,was the result of a combination of many factors.Tongyu County has the flat terrain and the arid climate,therefore,the evolution of rural settlements was weakly affected by topographic factors,but water was an important factor affecting the distribution of rural settlements in this region,and there were differences on the effect between rivers and reservoirs.Traffic and locational conditions was the main factors to promote the expansion of rural settlements,meanwhile the pollution,noise and other adverse effects,such as urban sprawl led to the reduction of rural settlements near the traffic line and township.Cultivated land and rural settlements showed obvious spatial correlation,and the correlation of rural settlement scale and demographic(agricultural population)trends was significant,which demonstrated that the man-land relationship reflected by arable land resources and population pressure was a key driving factor on the evolution of rural settlements.The ecological migrants and the centralized residence artificially changed the spatial distribution of rural settlements,so becoming one of the factors affecting rural settlement evolution.Overall,the expansion of rural settlements generally occurred in area with the better locational or natural environment,whereas the significantly shrinkage of rural settlements occurred in the area with relatively poor natural environment and geographical conditions.(3)The scale of saline-alkali land in Tongyu County has increased significantly,and its evolution has periodic differences,while the spatial pattern of saline-alkali land has not noticeably changed,but the difference narrowed in the space.From the total scale of saline-alkali land,in recent 50 years,the land salinization in Tongyu County has experienced a rapidly deteriorated to gradually improved trend,in the first 40 years,the change of saline-alkali land was rapid and large.At township scale,the intensity and speed of dynamic changes of saline-alkali land had obvious regional differences,manifesting the saline-alkali land in towns with heavier land salinization increased faster,and the saline-alkali land in towns with lighter land salinization increased greater.In 1965,the majority of saline-alkali land of Tongyu distributed in the Northeast region,and mainly distributed in Shihuadao Xiang,Hongxing Town,Shuanggang Town and Bamian Xiang,while the saline-alkali land was relatively small in the southeast region of Tongyu.In the past 50 years,the land salinization of Tongyu has been aggravated,the spatial pattern of the saline-alkali land has not changed significantly,but with the dynamic evolution of saline-alkali land,the spatial difference of saline alkali land has reduced.The decrease of precipitation,the increase of temperature,the shortage of water resources and the high intensity of human activities has aggravated the soil salinization in the study area.(4)There is a spatial coupling relationship between rural settlement evolution and land salinization,but this relationship is restricted by the degree of land salinization.In the area with serious land salinization,the contradiction between people and land is more prominent,so the rural settlement evolution and land salinization has a strong spatial correlation,while in the region with lighter land salinization,land utilization has more choices,the traffic,locational,environmental and other factors have stronger effects on rural settlements,therefore,there is no spatial correlation between the expansion and shrinkage of rural settlements and land salinization.The expansion of rural settlements reduced the value of land ecosystem services,which was an important attribute of land degradation.In the region of serious soil salinization,the ecological environment is more fragile,and the land resources are scarce,which can easily lead to excessive utilization of land resources.Therefore,it is necessary to make clear the interaction between human activities and land degradation,optimize the spatial pattern of rural settlements in the ecological fragile areas,and then improve the ecological environment,so as to realize the sustainable utilization of land resources. |
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