The Coupling Relationship Between Vegetation Health And Soil Quality During The 150-Year Restoration Succession

Over the past two decades,a range of ecological challenges,including global warming,loss of biodiversity,and increased occurrences of extreme weather events,have posed serious threats to the stability of natural ecosystems and the sustainable development of socio-economic systems.In response,the United Nations,the International Union for Conservation of Nature(IUCN),and several countries have launched joint initiatives such as the Bonn Challenge(Revegetation)and the KunmingMontreal Global Biodiversity Framework,with the aim of restoring environmental functions and achieving stable and sustainable growth by 2030.In this study,we investigated the coupling relationship between vegetation health and soil quality during the restoration succession process in the Ziwuling area,which has a restoration history of more than 150 years in the temperate zone.We selected eight typical vegetation succession stages from different restoration periods,ranging from agricultural land and grassland to shrubs and trees,for field surveys and sample plot sampling,integrating literature to explore the evolutionary mechanisms and functional characteristics of species coexistence,diversity,and stability,as well as evolutionary features and aboveground biomass during long-term vegetation restoration succession.These aspects were examined from multiple perspectives,including plant composition,geographic distribution,community characteristics,and evolutionary history.We revealed the mechanisms of mutual promotion and correlation between vegetation succession and soil physical and chemical properties,constructed comprehensive evaluation indexes of vegetation health and soil quality,and evaluated the role and relationship between vegetation health and soil quality from the perspective of system dynamics with the help of coupled models.Obtaining feasible vegetation restoration suggestions from nature is a significant outcome of this study.It has practical implications for preventing soil erosion and land degradation,maintaining vegetation health and soil quality,and promoting sustainable development of the local ecological environment.The main findings are as follows:(1)The dominant families during the long-term vegetation recovery process in this study were found to be Asteraceae,Rosaceae,Gramineae,and Leguminosae,which collectively accounted for 49.22 % of the total species.Artemisia was the dominant genus(7 species).Monospecific genera accounted for 82.83 % of the total number of genera.The genus has a temperate geographic range type,which is important for community stability;however,tropical component species had a significant impact on plant diversity.Herbaceous plants were the dominant living type,representing 61.72 %of total species,and 69.53 % of plants were mesophytic in ecotype.Overall,the 30 dominant plant species showed a positive correlation throughout the entire vegetation restoration process,with 87.13 % of species pairs exhibiting weak interspecific competition and stable interspecific relationships,reflecting the characteristics of positive community succession.(2)The coexistence mechanism of species within the community is revealed,indicating that species can coexist by reducing interspecific competition through spatially heterogeneous distribution and storage effects,which create asynchronous differences over time.The similarity in environmental resource requirements among dominant herbaceous species was greater than that of woody plants,resulting in the peak diversity of herbaceous plants occurring earlier than that of woody plants.This temporal asynchrony was also an important factor affecting community stability.Additionally,variation in community diversity of woody plants explained 61.2 % of the variation in community stability.(3)The study elucidates that sampling effect and niche complementarity mechanisms are not contradictory.This was attributed to environmental filtering effects that allowed dominant species in the proximal phylogeny to drive changes in AGB,while species in the distal phylogeny could increase the upper limit of AGB during the same period through a complementary ecological niche mechanism.The study found that the highest aboveground biomass(AGB)of 24233.88 ± 2914.85 g/m~2 occurred at the 135-year(mixed coniferous)stage of vegetation restoration.Furthermore,evolutionary diversity of woody plants explained about 84.7 % of AGB variation during long-term vegetation restoration in temperate zones,and phylogenetic diversity(PD)were the main predictors of AGB.(4)The study determines the characteristics of changes in vegetation health and soil quality,as well as their influencing factors.In the phase of vegetation restoration up to 70 years ago,both vegetation health and soil quality indices showed an increasing trend.However,after this period,the vegetation health index started to decline rapidly.The vegetation health index was significantly and positively correlated with community stability and with species richness based on temperate components.Soil quality,on the other hand,was related to soil bulk density,total porosity,and total nitrogen and potassium content.Fine root biomass and litter accumulation were the key mediators of vegetation-soil linkages,explaining 89.5 % of the variation in soil hydraulic conductivity and carbon sequestration properties during vegetation restoration.(5)The study emphasizes that the entire 150-year process of vegetation restoration undergoes a transition from a vegetation-lagged state in the early stages of recovery(approximately before 40 years)to a soil-limited coupled state in the middle and later stages of succession(approximately 70-150 years).Additionally,the coupling coordination was on the verge of becoming dysfunctional at both the beginning and end of the succession.This was related to the accumulation of soil carbon and nitrogen nutrients during the early stage of vegetation recovery and the limiting effect of soil nitrogen and phosphorus elements during the middle and late stages of succession.Total soil nitrogen content was the most important limiting factor in the coupled vegetationsoil relationship,and both vegetation health and soil quality were likely to benefit from the process of plant diversity restoration dominated by species richness.In summary,this study highlights multiple aspects,including species coexistence,community stability,evolutionary history,and vegetation-soil coupling,to suggest several natural solutions for promoting successful vegetation restoration.Specifically,the following actions should be taken: 1)strengthen the conservation of positively correlated species and pay attention to the status of negatively correlated species;2)restore plant diversity to enhance multiple ecological benefits;3)plant a combination of distantly related and different life form species;4)use multiple species mixing or interseeding with leguminous plants;and 5)supplement carbon and nitrogen in the early(before about 40 years)and nitrogen and phosphorus(about 70-150 years)in the middle and later stages of vegetation restoration.These natural solutions can help address the challenges of global change.The dominant species,including Carex lanceolata,Lespedeza bicolor,and Sophora davidii,can coexist with multiple species,play a critical role in maintaining community stability,and provide various ecological functions such as nitrogen fixation and soil conservation,making them valuable biological heritage.Therefore,local afforestation projects could consider increasing these three species,with the leguminous plant Lespedeza bicolor being the best choice among the temperate components.