Assessment Of The Health Status Of Main Forest Types In Gansu Province

Gansu is one of the typical ecologically fragile areas in the northwest of our country,and its forest health level is closely related to ecological problems such as regional soil erosion,land desertification,and fragile ecological environment.The forest health assessment is an important means to understand the regional forest health status.As the premise of improving the regional forest management model and improving the forest health level,it is of great significance to evaluate the forest health status in Gansu Province..This study took 8 main forest types in Gansu as the research object,and selected 16 indicators from 4 aspects of forest productivity,forest ecosystem stability,forest community structure and forest soil condition.Collect indicator data through field surveys of 142 typical sample plots,and use the principal component analysis method,to construct the indicator system for forest health assessment in Gansu,and to estimate the forest health index.Finally,analyze and assess the forest health status in Gansu from four perspectives: forest overall,forest type,forest origin,and forest age group,and analyze the main factors that affect forest health status.The main conclusions are as follows:(1)The main forest types in Gansu are mainly in medium health and unhealthy state.The distribution range of the overall health index in Gansu is 1.059 to 1.149,and the mean value of the forest health index is in the index range of medium health.Overall,the health status of the main forest types in Gansu: med–healthy(35.9 %)> sub–healthy(29.6 %)> unhealthy(19.0 %)> healthy(15.5 %).Therefore,it is necessary to tend the unhealthy stands in time,to improve the stand structure,and to improve the productivity and stability of the stand.(2)Among the different forest types in Gansu,the forest health status of Robinia pseudoacacia plantation and Populus spp.plantation is relatively poor.Overall,the health status of different forest types: Quercus spp.natural forest(0.412)> Larix gmelinii plantation(0.407)> Abies fabri natural forest(0.366)> Picea spp.plantation(0.136)> Pinus tabuliformis plantation(-0.085)> Picea spp.natural forest(-0.114)> R.pseudoacacia plantation(-0.215)> Populus spp.plantation(-0.457).And it is necessary to prune and thin trees in time for the R.pseudoacacia plantation and the Populus spp.plantation in Gansu,replant and replant,adjust the stand density,to improve the productivity and anti-interference ability of the forest,and give full play to the ecological benefits of the forest.(3)Among the forest types of different origins in Gansu,the forest health index of artificial forest was significantly lower than that of natural forest.According to the analysis of forest composition,the plantation forests in Gansu are mainly in the state of med–health(40.0 %),sub–health(28.8 %)and unhealthy(23.8 %),and the forest health level is relatively lower;natural forests are mainly in the state of med–health(30.6 %),sub–health(30.6 %)and healthy(25.8 %),and the forest health level is relatively higher.It is necessary to carry out near-natural management and transformation of the early planted forests with large single species and unstable structure,and adopt methods such as selective cutting and renewal,to improve the forest ecological structure and improve the health level of the planted forests in Gansu.(4)Among the forest types of different age groups in Gansu,the forest health level of mature forest and over–mature forest is relatively higher,and the average value of forest health index is in the range of sub–health state.Overall,with the increase of forest age,the forest health index showed a trend of first increasing and then decreasing.The health status of forest types in different age groups: mature forest(0.349)> over–mature forest(0.318)> near–mature forest(-0.114)> middle–aged forest(-0.118)> young forest(-0.210).Therefore,it is necessary to take comprehensive tending measures for mature and over-mature stands that degenerate and promote stand renewal.For middle-aged and young forests in the growth and development stage,stand density should be adjusted reasonably,stand structure should be optimized,weeding and selective cutting should be done,and soil should be loosened.The results of this study reveal the current status of forest health in Gansu,and can provide reference and suggestions for future forest management in Gansu.It is of great significance to improve the forest structure,increase forest productivity,enhance ecological function and realize the sustainable development of forest resources in Gansu.Moreover,the forest health assessment system in Gansu region constructed in this study also provides a reference for the later related areas to carry out forest health assessment research.