Spatial-temporal Distribution Characteristics Of Grassland Degradation In Kazakhstan And Its Impact Factors Analysis

Affected by social institutional transformation and climate change,Kazakhstan is the most significant country with ecological degradation and grass-livestock contradiction in Central Asia.Over the past century,the distinct characteristics of various grassland ecosystems have changed due to agricultural reclamation,changes in grazing patterns,and climate change in Kazakhstan.Therefore,it is important to study the process and mechanisms of grassland degradation in Kazakhstan in order to understand the responses of grassland ecosystems to climate change and human activities in Central Asia.These findings may also support regional ecological sustainable development in the construction of green silk roads.This study is based on the spatial consistency of five land cover datasets to extract the typical grassland area with the highest credibility;Retrieving vegetation coverage in typical grassland areas based on long-term sequence of GIMMS NDVI datasets,the temporal and spatial distribution characteristics,grassland degradation distribution characteristics were studied;Combining temperature,precipitation,literature,and statistics to study the influence of grassland vegetation to climate and human activities,results showed that:(1)The data sources of five Land Cover datasets,analyzing the definition of grassland types,remote sensing data sources,auxiliary classification data,classification methods,verification data and method differences,and extracting grassland information of each set of data sets.Using consistency of spatial distribution method to extract typical grassland(CCHC),which has area of 89.57�10~4 km~2,accounting for 39.66% of the tota,which were mainly located in the typical grassland and part of the semi-desert grasslamd.The spatial consistency gradually decreased from the inside to the outside around the typical grassland distribution zone.(2)The vegetation coverage of typical grassland areas shows the difference in zonal distribution,which was lowly in the south and highly in the north.The vegetation coverage was 36.84%,which is in low coverage state.In the past 34 years,the vegetation coverage has shown an overall upward trend.The proportion of areas with extremely significant rise and significant increase is 15.30% and 10.64%;the central and eastern regions show an improvement trend,and the western region shows a downward trend.In the four seasons,only the summer vegetation coverage showed a trend of rising(slope=0.0017),and the areas of extremely significant increase and significant increase were 17.61% and 11.93%.In spring and winter,the grassland vegetation coverage showed a downward trend.There was no significant change of grassland vegetation coverage in autumn.(3)During the period from 1982 to 2015,the average GDI was 2.05 of typical grassland(CCHC)in Kazakhstan,the total area of degradation reached 50.65�10~4 km~2.The region in moderate degraded stage,with slight degradation(38.90%)and moderate degradation(13.67%)accounting for a larger proportion.From four periods(1982-1991,1992-2002,2003-2010,2011-2015),it has the characteristics of overall improvement and increased local degradation,the degraded areas are 61.57�10~4 km~2,52.77�10~4 km~2,50.32�10~4 km~2 and 37.88�10~4 km~2.For four periods,the GDI were 2.09,2.05,2.06 and 1.93.The three stages(1982-1991,1992-2002,2003-2010) were moderate degraded,and the current period(2011-2015) was slight degraded.Slight degraded regions have a tendency shift to undegraded regions,which were distributed in Karaganda,Eastern Kazakhstan,Pavlodar and so on.Slight and moderate degraded regions have a tendency shift to moderate and severe degraded,which was distributed in Aktobe region.(4)During the interannual period,vegetation coverage and precipitation in Kazakhstan showed a significant positive correlation with precipitation,and had no significant relationship with temperature.Vegetation coverage and spring,summer,autumn and winter precipitation were insignificantly correlated,significantly positively correlated,significantly positively correlated and insignificantly correlated.There was a significant negative correlation between temperature and the vegetation coverage of summer and autumn,and the area ratio were 13.64% and 29.56%.There was no significant correlation between temperature and the vegetation coverage of spring and winter.In East Kazakhstan and West Kazakhstan,they are mainly positively promoted and negatively degraded by human activities.After the collapse of the Soviet Union,due to the influence of the government system,large state-owned pastures were abandoned and concentrated on grazing near the place of residence,resulting in serious degradation of local grassland.