Zoning of ecological treatment in typical karst areas based on ecosystem vulnerability assessment
Guohua Demonstration Zone for Ecological Restoration of Desertification(hereinafter referred to as Guohua Demonstration Zone)is located in Guohua town,Pingguo City,Guangxi,with a total area of 30 km2.It is a typical area of karst peak-cluster depression.Before the treatment of rocky desertification,Guohua Demonstration Zone suffered from severe rocky desertification and soil erosion.Few crop varieties grew there with low land productivity.This area was covered with less than 10％of vegetation and less than 1％of forest.Consequently,it was extremely fragile in ecological environment.After more than 20 years of systematic governance,the vegetation coverage in the demonstration area has increased to 85％,and the proportion of rocky desertification area has decreased from the original 76％to 12％.The ecological environment has been greatly improved.This study aims to further provide a scientific basis for the ecological protection and restoration in the demonstration area,and to provide reference for the development of ecological governance strategies in karst areas based on the results of ecosystem vulnerability evaluation at a micro scale.With these purposes,this study has established an index system for ecosystem vulnerability evaluation.Based on the"cause-effect"model,this study selected seven indicators including rock type,slope,comprehensive soil nutrient level,land use status,vegetation coverage,soil erosion intensity,and degree of rocky desertification.In a 10 mx10 m grid taken as a unit,GIS technology and Analytic Hierarchy Process(AHP)were used to conduct a high-resolution ecosystem vulnerability evaluation in Guohua Demonstration Zone.By single parameter analysis,the contribution rate of each evaluation index to ecosystem vulnerability was calculated to analyze the main influencing factors causing ecosystem vulnerability in the study area.The results showed that the proportions of areas with micro,mild,moderate,severe,and extremely fragile ecosystem in the study area were 36.43％,33.90％,18.91％,9.34％,and 1.43％,respectively.The main factor causing micro vulnerability of ecosystem in the study area is natural background,and ecological treatment in micro-vulnerable area should mainly focus on the maintaining of current situation,especially the protection of existing forest and grass vegetation.The main factors causing mild and moderate vulnerability of the ecosystem in the study area are natural background and human activities.Ecological treatment in mild and moderate vulnerable areas should focus on the protection of existing forest and grass vegetation and the limiting of human activities.The main factor causing severe and extremely vulnerability of the ecosystem in the study area is degradation of ecological environment.Ecological treatment in severe and extremely vulnerable areas should focus on the strict restriction of human activities and the restoration of forest and grass vegetation.According to statistical analysis of the overall vulnerability of ecosystem in different land uses in the study area,the main directions in ecological treatment for different land uses were proposed.Paddy fields should be mainly developed and utilized.Dry land,grassland and gardens should be developed and utilized under the premise of protection and restoration.The existing vegetation in forest land should be protected to achieve a positive vegetation succession,with appropriate development and utilization.Mining land should be restored ecologically.Other land types should be maintained in their current status.Based on the slope and land area,the study area was divided into nine zones:the mountainous zone closed off for afforestation,the artificial afforestation zone,the under-forest planting zone,the zone for grassland improvement,the zone for garden transformation,the zone for special economic plants,the zone for returning cropland back to forests,mining restoration zone,and non-treatment zone.Specific measures for treatment were proposed for each zone.To protect existing vegetation and promote natural positive succession of vegetation,human activities such as land reclamation,grazing,and firewood cutting should be prohibited in the mountainous zone closed off for afforestation.In the artificial afforestation zone,heliophilous species such as Dalbergia odorifera T.Chen.,Delavaya toxocarpa Franch.and Leucocephala(Lam.)de Wit,which need light in plots with low vegetation coverage can be planted.In plots with high vegetation height and moderate coverage,neutral and sciophilous species such as Cyclobalanopsis Oerst.and Caesalppinia sappan L.,which need some shade can be planted.Vine shrubs such as Euonymus fortunei(Turcz.)Hand.-Mazz.and Ficus pumila L.can be planted on side slopes and steep slopes to form plant hedges.In the under-forest planting zone,characteristic economic plants suitable for karst areas,such as Erythropalum scandens Bl.and Lonicera japonica Thunb can be introduced.In the zone for grassland improvement,high-quality perennial grass with strong resistance such as Guimu No.1,Cichorium intybus L.and Pennisetum purpureum,can be cultivated to develop livestock husbandry.In the zone for garden transformation,low-stem economic crops such as Erythropalum scandens Bl.and Lonicera japonica Thunb.can be intercropped under the forest.In the zone for special economic plants,evergreen wild vegetables suitable for growing in karst areas,such as Erythropalum scandens Bl.and Sauropus androgynus(L.)Merr.can be introduced to replace traditional crops such as corn.In the zone for returning farmland to forest,afforestation and grass planting should be carried out to promote the restoration for forest and grass vegetation according to local conditions.Ecological slope protection,site leveling,greening,and backfilling with netted soil can be implemented for reclamation and greening in the mining restoration zone.In non-treatment zone,the current situation can be maintained.
karstecological vulnerability evaluationzoning of ecological treatmentGuohua Demonstration Zone for Ecological Restoration of Desertificationenvironmental degradation
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