| It is of great significance to obtain information on forest distribution characteristics and change in West Tienshan Mountain（in Xinjiang,western China）in an accurate and timely way,which helps the rebuilding of ecological environment and scientific evaluation and performance of natural forest protection project there.Aiming at existing problems in forest sensing like tedious data acquisition,selection and preprocessing existed in large-scale forest spatial information extraction and long time series intensive monitoring,poor computing efficiency in large data volume of sensing information and low accuracy,this article is supported by the Google Earth Engine platform and makes full use of its strong functions in data organization,storage and computing.According to forest distribution characteristics of arid region in Xinjiang,this article establishes a multi-dimensional（spectrum,texture,topography）feature classification set by integrating multisource data set of sensing and geographical factors,and builds a forest sample data base for West Tienshan Mountain forests,which is assisted by newest ground survey sample data from geography national condition monitoring.At last,this article adopts random forest classification algorithm,achieving multi-period forest information classification extraction in natural forest reserve of West Tienshan Mountain in 1995,2000,2005,2010,2015 and 2018.Based on the above,a preliminary quantitative evaluation is conducted on the benefit of ecological restoration of natural forest reserve project in West Tienshan Mountain by integrating comprehensive ecological factor indicators like forest coverage,vegetation coverage,and productivity through the methods of cloud and local interoperability,completing forest resource classification inspection,mapping and time-space analysis from the year 1995 to 2018.The result of research shows that:（1）In terms of geospatial pattern,the forests of West Tienshan Mountain are mainly distributed on the shady slopes of high mountains due to restriction from growth environment.In terms of spatial distribution,forest is more distributed in mountainous areas,less in plains;most in northwest,southwest and east,less in west and central.In structural composition,coniferous forest is the dominant forest type（advantaged constructive species）in West Tienshan Mountain,with a small proportion of broad-leaved forest,shrub forest and theropencedrymion（mixed broadleaf-conifer forest）.（2）In the process of time evolution,the forest area of natural forest reserve in West Tienshan Mountain has been on the rise from 1995 to 2018（23 years）dynamically on the whole and total forestry area has increased from 3,953.57 km2 in 1995 to 4,243.41km2 in 2018 at an increase rate of 12.60 km2/a approximately.The growth rate of forest has risen steadily in the past 23 years.The growth rate during the time period of2005-2018 is slightly higher than that of 1995-2015.Transformations among different types of forest land are fewer and forest cover newly increased is mainly transformed from non-forest land to forest land.At the same time,the forest cover rate in West Tienshan Mountain also on the linear increase from 1995 to 2018.（3）From the quantitative inversion of ecological factor indicators such as forest vegetation coverage（FVC）and net primary productivity（NPP）in the research area,it can be seen that the average vegetation coverage under forest cover in Natural Forest Reserve of Western Tienshan Mountain reached more than 90%.The overall vegetation coverage has a little change from 2000 to 2018.Except that the fluctuation of vegetation cover is large in Chabuchar Branch,the overall vegetation coverage of each county branch maintains a gentle upward trend.Net primary productivity shows a linear and significant growth trend,among which the average vegetation NPP in West Tienshan Mountain is 270.39 g·m-2·a-1,and the growth rate is 1.68 g·m-2·a-1,the average NPP under the forest cover of West Tienshan Mountain is 314 g·m-2·a-1,and the growth rate is 2.351.68 g·m-2·a-1.It can be seen from the monitoring results above in a comprehensive perspective that West Tienshan Protection Project has yielded positive and significant results since its implementation.In the recent 20 years,approximately 520 km2 of non-forest land has been converted to forest land in West Tienshan Mountain,mainly in the Tekes Forestry Bureau.,Nileke Forestry Bureau.,Zhaosu Forestry Bureau.,Xinyuan Forestry Bureau,Gongliu Branch,Yining Forestry Bureau.Regional vegetation coverage has remained good;net primary productivity has been continued to rise;forest coverage has increased from 14.56%in 1995 to 16.16%in 2018. |
