Dynamic Changes Of Karst Rocky Desertification In Wuling Mountain Area And Their Driving Mechanism

Since 2000,a series of actions have been taken by the nation for ecological restoration including returning farmland to forest,grassland,and ecological non-commercial forest protection engineering and comprehensive management of rocky desertification in the southwest karst rocky desertification area.Especially by the state council approved"Comprehensive management outline for rocky desertification in karst region?2006-2015?"in 2008,the control of karst rocky desertification area has been intensified and the vegetation restoration has achieved another milestone.Wuling mountain area covers 4 provinces and 71 counties with multiple nationalities settlement.The climatological and ecological environment is complex and diverse.The occurrence and development of rocky desertification in this area has its own unique characteristics.Based on the monitoring data on rocky desertification in 2012 and 2017 and using ArcGIS10.2,ENVI,CASA model and relevant statistical analysis software and methods,This paper discusses the spatial-temporal evolution of karst rocky desertification and dynamic changes of plant community NDVI and NPP in Pengshui county under the comprehensive control and presents analysis of the driving force for evolution of rocky desertification,aiming at making it known to the dynamic variation characteristics,main driving force and treads of rocky desertification and vegetation restoration in the study area during the two desertification periods,providing a certain reference for the comprehensive treatment of karst rocky desertification and the ecological benefit evaluation of the ecological construction project of returning farmland to forests in the multiple nationalities settlement in Wuling mountain area,as well as a scientific basis for further optimizing the model and method of rocky desertification governance to improve the ecological environment in karst rocky desertification area.The main findings include:?1?The third monitoring of rocky desertification?2017?shows that the area of rocky desertification in Pengshui county is 931.96km²,which is relatively small variation in comparison with the monitoring of the second rocky desertification monitoring?2012?,and the decrease of 23.94 km²only indicates that the situation of rocky desertification in the study area is still serious and remains a treatment problem.Among them,the area of severely,moderately and mildly rocky desertification respectively is 56.28 km²?decreasing from 112.0km²?,506.72 km²?decreasing from593km²?and 368.96 km²?increasing from 239.53?,moderately and mildly rocky desertification take up a large area,which accounts for 93.96%of the desertification area of in the study area.?2?From the superposition and comparative analysis,the overall situation of rocky desertification in the study area shows a degree of alleviation,and the land type of rocky desertification presented a transformation from mild-moderate-severe to mild-moderate-severe rocky desertification in 2012,and the extremely severe rocky desertification basically disappeared.The two times of monitoring indicates medium rocky desertification is mainly presented on the study area,while compared in 2012,the mild rocky desertification was greatly increased in 2017,and the area of severe rocky desertification reduces by approximately half.?3?According to the study on transfer matrix,the evolution of rocky desertification in the research area mainly turns towards good direction,mainly presenting a characteristic of non-rocky desertification and potential rocky desertification with a significant increase in the land area of mild rocky desertification,and the evolution transition of moderate and severe rocky desertification to mild rocky desertification.As a result,the landscape fragmentation index increases with total number of rocky desertification patches increasing while the area slightly reducing,and the area of severely rocky desertification has reduced or even disappeared.The number of severe and moderate rocky desertification is decreasing,but mild rocky desertification is increasing.The total number of moderate and severe rocky desertification patches decreases while the total number and area of mildly rocky desertification patches increase.?4?It is shown that Masson pine,cedar and fir form a dominant vegetation restoration in the studied area by analysis of multi-source image data.The results show that during the monitoring period?2012-2017?on rocky desertification,the area of Masson pine increases while that of cedar and fir decreases.The group of broad-leaved forest and coniferous and broadleaved mixed forest increases slightly.The maximum synthetic value of the vegetation NDVI in the research area increases generally but with no obvious trend.During the two monitoring periods of rocky desertification,the maximum NDVI change in 6 years is small,and the spatial variation coefficient of most areas in the study area shows below 0.15.The NPP/per year in 6a in Penshui autonomous county presents 420 gC?m^-2?a^-1-569gC?m^-2?a^-1(mean 527.48 gC?m^-2?a^-1),which accounts for 11.14%to 23.64%of the net primary production of vegetation nationwide.The overall vegetation is represented on southwest-northwest diagonal distribution with the increasing amplitude of the vegetation NPP progressively decreasing respectively along two southwest-northwest central zone in the study area.?5?The driving force respectively or jointly by the natural environment factor,social and economic factor and ecological restoration factor may be applied to the evolution of the rocky desertification of the research area from different perspectives.Using correlation analysis and multivariate ordered Logit model analysis shows that ecological engineering and its implementation periods in ecological recovery factor constitute the leading driving factor affecting rocky desertification in the study area.?6?Using multiple linear regressions to analyze specific socio-economic factor and ecological recovery factor and the development status of rocky desertification in different regions is researched by superposition of the administrative divisions of towns and villages,and thereby dividing them into rocky desertification-improvement area,rocky desertification-recovery zone and rocky desertification-stabilization zone,and proposing corresponding measures for further desertification control.