| The rocky desertification areas in South China Karst are faced with problems such as prominent contradiction between human and land,serious vegetation degradation,lack of secondary forest structure,low species diversity,poor stability and low efficiency of ecological and economic functions.Tree-shrub-grass restoration and forestry are very important parts of comprehensive control of rocky desertification,playing pivotal role in curbing the occurrence of rocky desertification,controlling soil erosion,maintaining the stability of fragile ecosystems,protecting species diversity,enhancing the economic level and other service functions,which is of great significance to promote the ecological reconstruction and socio-economic development in rocky desertification areas.According to the comprehensive and regional characteristics of geography,combined with the coordinated development of human-land relationship theory,species diversity theory,local conditions theory,sustainable development of tree-shrub-grass counterpoint configuration theory,the multi-angle and multi-domain nutrient balance theory,the succession of plant community theory,the tradeoff and counterpoint configuration of functional traits theory and so on,Bijie Salaxi Area,Guanling-Zhengfeng Huajiang Area and Shibing Karst Area in Guizhou plateau mountainous area on behalf of the overall structure of the south China karst environment were chosen from 2016 to 2020 as the study areas.Based on continuous field orientation and observation in 60 test sample lands,data collection and test for environment factors and plant traits of 71 filtrated dominant species,the research work was carried out with full chain design,integrated deployment,and sub-modules promotion,focus on basic frontier research,research and development of common key technologies,application demonstration and industrialization promotion of the restoration of tree-shrub-grass restoration and characteristic high-efficiency forestry in the management of rocky desertification.Emphasis was given to systematic research on vegetation species diversity and functional traits,high-efficiency characteristic forest adaptation strategies and ecological service functions,forestry model and technology integration,application demonstration,verification and promotion,with a view to providing scientific and technological reference for national rock desertification control projects.?1?In the first part,the change law of plant physiological structure at two levels of species and community with the rocky desertification grades was discussed.And the characteristics of plant diversity and functional traits were clarified.The differences in plant community structure,diversity and functional traits under different levels of rocky desertification and their effects on the nutrient transport and distribution of plant leave-litter-soil were also expounded.The lower the rocky desertification grade is,the higher the species diversity and the more obvious the three-dimensional structure of the community are.With high dry matter content,trees and shrubs have strong resistance to external environmental changes.Herbaceous plants,with high light compensation ability and growth rate,but with low light tolerance,are more suitable to be planted as understory species in the process of community structure configuration.Their specific leaf area is 277.18cm2·g-1,higher than that of trees,153.78cm2·g-1,and that of shrubs,108.85 cm2·g-1.Compared with the nutrient content of global plant leaves,plant leaves in karst rocky desertification areas have a strong C storage capacity(482.31 mg·g-1),which is manifested as N deficiency and sufficient P.Soil variability is higher in Karst area.And the decomposition and mineralization rate of soil organic matter in the areas above moderate rocky desertification are higher,but its nutrient content is lower than that of plant leaves and litter.Following results are obtained after comparative analysis of the three study areas.Firstly,quantum efficiency of plants in the non-potential rocky desertification environment is 0.17 mol·mol-1,higher than that of the other two demonstration areas which is 0.054 mol·mol-1.This is the advantage of plant growth in this area as understory plants have high photosynthetic potential in low-light environments and strong light utilization and organic manufacturing capabilities.Secondly,the advantages of plant growth of arbor forest in potential-mild rocky desertification environment are the wide range of light utilization,with high light saturation point and low light compensation point,and strong adaptability to strong and weak light.These discoveries are conducive to revealing the ecological process and nutrient cycling mechanism of plant communities in rocky desertification environment.?2?In the second part,the driving factors of species and community changes were discussed at first.Secondly,the characteristic high-efficiency forest adaptation strategies and ecosystem service functions based on species diversity was revealed.Thirdly,the driving mechanisms of soil environmental factors on soil enzymes,plant functional traits,and nutrient transport were found.Fourthly,the trade-off strategies and service function regulation strategies were proposed by using the structure-function traits.Soil enzymes respond differently to different grades of rocky desertification environment.The leading environmental factors affecting the enzyme activity are SOC,TN,C:P and N:P in no-potential rocky desertification environment;pH and TP in potential-mild rocky desertification environment;C:N,N:P and TN in moderate-intense rocky desertification environment.The effects of each factor on soil enzyme activity are functionally redundant,and some of the enzyme activities are affected by the superposition of multiple environmental factors.Under the influence of soil environmental factors,the driving mechanism of plant functional traits differs.The main controlling environmental factors are SWC and TN in non-potential rocky desertification environment;SWC,TN and N:P in potential-mild rocky desertification environment;SWC and SOC in moderate-intensity rocky desertification environment.Soil environmental factors have different driving mechanisms for plant nutrient absorption.The main driving factors affecting plant stoichiometry are C:P,N:P and TP in no-potential rocky desertification environment;pH,TP,C:P and SOC in potential-mild rocky desertification environment;C:P,TP,C:N and SWC in moderate-intense rocky desertification environment.Results show that it is necessary to carry out fertilization management and nutrient migration protection for the main control factors in the process of rocky desertification control.There is a correlation between structural traits and physiology,which confirms the existence of leaf economy.71 different functional species adopt different environmental adaptation strategies through the trade-off between leaf traits.Tree species are mostly slow-investment-income species,and shrubs are mostly fast-investment-income species.Generally,the rapid investment pioneering strategy is mainly used to invest in species with fast growth rate and acquisition ability;the slow investment conservative strategy is mainly used to invest in plants with nutrient storage efficiency.Sorting the water conservation and soil conservation performance of 71 species,it is found that trees have higher functional traits,shrubs are second,and herbs are third.Finally,12 functional groups and control strategies are constructed based on service functional traits,which is of great significance for revealing ecological processes and operating mechanisms,predicting community succession trends and improving overall service performance.?3?According to the adaptation strategy and ecosystem service function of characteristic high-efficiency forest,the tree-shrub-grass restoration and characteristic high-efficiency forestry model at different grades of rocky desertification environments were constructed.And common key technologies were developed,integrating the technology system of environment ecological restoration and forestry among no-potential,potential-mild,moderate-intense rocky desertification areas.According to the trade-off strategy and the service function control strategy,the compound management model of ecological restoration and protection and high-efficiency forestry was constructed in the potential-light rocky desertification environment of karst plateau mountainous region in Bijie Salaxi area;the cycle management model of ecological restoration and high-efficiency forestry was constructed in the middle-strength rocky desertification environment of karst plateau gorge in Guanling-Zhenfeng Huajiang area;the sustainable management model of ecological protection and high-efficiency forestry was constructed in the no-potential rocky desertification environment of karst mountain gorge in Shibing Karst area.Theses models are referred to as"Bijie Model","Guanling-Zhenfeng Model"and"Shibing Model",respectively.By summarizing existing mature technologies in the models,common key technologies and technical systems were researched and developed,such as seed storage and treatment,fertilization management,pruning and shaping,fruit processing and storage,inter-forest interplanting,derivative industry development and sustainable development,species diversity maintenance of tree-shrub-grass,plant functional trait monitoring,plant functional group construction technology,and functional trait regulation and control.Aiming at no-potential,potential-mild,moderate-strength rocky desertification environment,the technology integrations such as three-dimensional configuration of tree-shrub-grass,combination of community functions,planning induced natural restoration,development of characteristic economic forestry,undergrowth cultivation,trade-off strategy construction were proposed.?4?The constructed vegetation restoration and forest industry model is operable,with good application demonstration effect,and can play a leading role in demonstration.The most suitable area for the promotion of the“Bijie model”,“Guanling-Zhengfeng model”,“Shibing model”are mainly distributed in the rocky desertification areas in the south,account for 9.89%,5.26%,and 8.95%of the total area in 8 southern provinces in south,Respectively.Since 2016,application and demonstrations of tree-shrub-grass restoration and characteristic high-efficiency forestry model have been implemented in the three study areas of Bijie Salaxi,Guanling-Zhengfeng Huajiang and Shibing karst.A total demonstration area of 223 hm2 in 20 demonstration sites have been constructed,setting a model of rocky desertification control,which is widely recognized and actively responded by the local people.The ecological,social and economic benefits have been improved.From 2016 to 2020,the vegetation coverage rate of the 20demonstration sites increased by 4.77%with 5 913.00 t/y of soil conservation,46 644m3/y of water conservation and 1990.5 million yuan/y of economic forests income,promoting the vegetation restoration and the development of forest industrialization in rocky desertification areas.Based on GIS index grading and weight calculation,and ArcGIS raster data spatial analysis,evaluation indexes such as elevation,precipitation,average temperature,slope,per capita GDP,population density,rocky desertification grade,land cover,soil type,lithology are established.With these indexes,the suitability of promotion of the three demonstration models are evaluated.The results show that in the area of 195.37×104 km2 the most suitable,more suitable,basically suitable,barely suitable and unsuitable areas for the promotion of the"Bijie model"in 8 karst provinces in southern China are respectively 19.12×104 km2,36.17×104 km2,41.28×104 km2,51.72×104 km2 and 47.08×104 km2;those areas of the“Guanling-Zhenfeng model”are respectively 10.17×104 km2,31.14×104 km2,46.13×104 km2,59.65×104 km2 and 48.28×104 km2;those areas of the"Shibing model"are respectively 17.30×104 km2,36.47×104 km2,48.27×104 km2,56.45×104km2 and 36.88×104 km2. |
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