Forest Ecosystem Services Driving And The System Function Improving In The Karst Desertification Control

In December 2021,the National Development and Reform Commission issued the "Construction Plan for Major Projects of the Ecological Protection and Restoration Support System(2021-2035)",which requires "promoting research on the structural functions,succession laws,and internal mechanisms of important ecosystems.",and "actively carrying out forest ecological protection and restoration,precise improvement of forest quality,afforestation on difficult sites,and optimization and improvement of urban forest service functions.".The karst desertification leads to significant differences in the structure,functions,and services of forest ecosystems between this region and non karst regions.As the main body of ecosystem functions and service supply in rocky desertification areas,forest ecosystems are crucial for ecological restoration,consolidation of achievements in rocky desertification control,and human well-being.To explore the impact of forest spatial structure,species,and functional diversity on ecosystem services.Based on geography,ecology,ecosystem services,human-land relations,and biodiversity principles theories,the scientific issues of the difference and change of ecosystem services and structure factors under different conditions and key technical problems on the improvement of forest ecosystem functions in desertification control.In Guizhou plateau,which represents the overall landform and habitat of the South China Karst,Salaxi karst plateau mountainous area,Huajiang karst plateau canyon and Shibing karst mountain canyon are selected as study areas.From 2020 to 2023,35 typical sample plots were selected in three research areas to conduct field vegetation surveys and collect plant and soil samples.Select tree height,uniform angle index,mingling index,and competition index to represent the forest spatial structure;Select species diversity(Shannon Wiener diversity,Margalef richness,Pielou evenness)and functional diversity(richness,evenness,dispersion)to represent ecosystem functions;And selecting wood and fruit yield represents provisioning services,soil C,N,P,and K nutrient content represents soil supporting services,and carbon sequestration,oxygen release,and water conservation represent regulating services.Using methods such as variance analysis,redundancy analysis,correlation analysis,and comparative analysis,the differences in the structure,function,and service of different forest ecosystem types in different landforms were clarified.The results indicate significant differences in spatial structure,species and functional diversity,and ecosystem services among different forest types,The driving mechanism of forest ecosystem service change is mainly discussed from two aspects of structure and diversity,and strategies for improving the system function are proposed based on the existing problems and driving factors of forest ecosystem management in desertification areas,with a view to providing scientific and technological reference for ecological restoration and protection in karst rocky desertification areas.(1)It was clarified that there are significant differences in driving factors and ecosystem services among forest types,and that coniferous broad-leaved mined forests have the optimal spatial structure,diversity,and ecosystem services supply capacity.In the three study areas,the monoculture forest is in a regular distribution state,while the mixed forests are in a random or aggregated distribution state;The overall structure,diversity level,and ecosystem service supply capacity of the coniferous and broad-leaved mixed forest are superior to other forest types.In Salaxi and Shibing,the species composition of coniferous and broad-leaved mixed forests are the highest,while Huajiang is the broad-leaved mixed forest with the highest;The tree height of coniferous and broad-leaved mixed forests are the highest.The coniferous and broad-leaved mixed forests has the highest uniform angle index and mingling index,while the monoculture forest has the highest competition index.In terms of diversity indexes,the species diversity index,functional richness,and functional evenness of the coniferous and broad-leaved mixed forest are also higher than those of other forest types,but the functional dispersion is the highest for the monoculture forest,confirming the result of the maximum competition index for the monoculture forest.In terms of ecosystem services,the wood production of coniferous and broad-leaved mixed forests is higher than that of other forest types,and the fruit yield capacity of monoculture forests is the strongest;The content of soil OC and TN of coniferous and broad-leaved mixed forest is the highest,while TP and TK are the highest in monoculture forest;The air and water regulation of coniferous broad-leaved mixed forest were significantly higher than those of other forest types.The species composition of monoculture forests is single and evenly distributed,but the intensity of competition is the largest among the four forest types,which overturns the view that the greater the stand density,the more intense the competition,and is conducive to revealing the spatial structure characteristics of desertification forest ecosystems and their impact on services.(2)The impact of driving factors on ecosystem services varies depending on indicators and environmental conditions,with spatial structure and species diversity driving more than functional diversity.There was a significant negative correlation between soil TP and uniform angle index and mingling index(p<0.05),indicating that there was a reverse effect between soil TP content and forest uniform angle index and mingling index.There is a significant(p<0.05)or extremely significant(p<0.05)positive correlation between tree height and wood supply,reflecting a significant enhancement effect between tree height and wood production.The relationship between other forest structure indicators and ecosystem services varies in different research areas,indicating that environmental conditions may have a certain degree of impact on forest structure and ecosystem services.In terms of diversity,the species diversity index of the three study areas has a significant or extremely significant negative correlation with soil TP and TK content,indicating that there is a trade-off between species diversity and soil TP and TK content.There are differences in the impact of drivers on services in different research areas,indicating that the interrelationship between drivers and services is influenced by the geographical environment.In general,the correlation between ecosystem services and spatial structure and species diversity index is greater than that of functional diversity index,reflecting that structure and species diversity have a greater driving effect on services than functional diversity,which is helpful to provide scientific reference for biodiversity protection and function improvement of forest ecosystems in karst rocky desertification areas.(3)Both structure and diversity have important affects on ecosystem services.In the process of forest management,the multi-functionality of the system can be improved by adjusting the spatial structure of the forest.The monoculture forest has a single species composition and the greatest structural defects.Except for higher fruit supply services than the other three forest types,the supply capacity of other ecosystem services is the lowest among forest types.However,considering that generating economic benefits is its main function,the forest structure and system versatility can be lower than the standards of primitive forests.Properly increasing the diversity of species composition and improving the hierarchical structure of trees,shrubs,and grasses in this forest type will help to improve system stability and functional diversity.The vertical structure of mixed forests is relatively complete,but the spatial structure of broad-leaved mixed forests needs to be optimized through strong artificial management measures,otherwise it cannot effectively improve the overall function of the forest in the short term by itself.The spatial structure of the coniferous and broad-leaved mixed forest is superior to the other three forest types,but there is a situation where the canopy closure is too high,resulting in slow growth or sparse species of understory plants.It is necessary to take measures such as manual pruning or thinning to reduce the density of tree stands and increase the amount of understory vegetation.The spatial structure of coniferous forests is basically complete,but the proportion of coniferous trees is too large,and the ecological function is weaker than that of coniferous broad-leaved mixed forests.The proportion of coniferous trees can be appropriately reduced,and the number of broad-leaved trees can be increased,which helps to improve the versatility of the coniferous forest system.This will helpful for the management of forest ecosystems and the improvement of regional ecosystem functions in rocky desertification control.