| With the accelerated rate of species extinction worldwide,the study of the relationship between species diversity and ecosystem stability has become an urgent issue.Functional traits of organisms not only respond to the survival strategies of biological communities,but also are key components that constitute the functional diversity of organisms.Functional diversity and functional redundancy of biological species are the main components of species diversity and play an important role in environmental change,community composition,and ecosystem function.Karst forests in southern China are fragile ecosystems,and research on their stability mechanisms is scarce.The presence of functional redundancy can ensure ecosystem recovery after disturbance and may be more reliable than species diversity for revealing plant community stability.In this paper,we investigated the plant communities at different restoration stages(grassland stage,grass-irrigation transition stage,shrub stage,tree irrigation transition stage,tree stage and terminal stage)of degraded vegetation restoration in the karst plateau area of Guizhou and the karst crest depression area of Guizhou in southern China.By collecting leaves of plant communities in different restoration stages of karst vegetation and their corresponding surface soils,the trends of functional traits,functional diversity and functional redundancy of plant communities in different restoration stages of vegetation were determined to elucidate the changes of plant community ecological strategies during the restoration of degraded vegetation in karst areas.The relationships between environmental factors and functional traits,functional diversity and functional redundancy of plant communities were elucidated through the determination of leaf C,N and P of dominant species and soil C,N,P and K.This study was conducted to compare the changes in functional redundancy and functional diversity of plant communities under different habitat conditions in karst areas,and to use them as the basis of stability maintenance mechanism,both to elucidate the maintenance pattern of community functional redundancy on stability under different species diversity conditions of karst vegetation,and to compare the strong and weak relationships of community stability maintenance drivers under different species diversity conditions.The main findings and conclusions obtained are as follows.(1)During the restoration of degraded karst plant communities,species diversity,biomass and stability all increased gradually and reached the maximum at the end of the restoration process,with species diversity,biomass and stability values of 0.89,129.36 t/hm~2 and 1.21 respectively in the karst plateau area and 0.95,201.04 t/hm~2 and 1.41 respectively in the karst depression.During the revegetation process,the species diversity,biomass and stability of the karst depressions were higher than those of the karst plateau at the same restoration stage.The correlation between the higher species diversity and stability(R~2>0.8)was stronger in the karst crest depressions than in the lower species diversity karst plateau areas.The biomass of karst plant communities showed a significant positive correlation with stability(P<0.05),while none of the relationships with species diversity were significant(P>0.05)(2)The changes of community functional characters in the process of plant community restoration in karst area are closely related to the influence of environment.The specific manifestations are as follows:(1)The performance of plant community functional traits differs in different restoration stages of karst vegetation.Plant communities in the early recovery stage(grassland stage)are mainly influenced by leaf area;plant functional traits in the middle recovery stage(grass and shrub,tree and shrub)are different in different study areas,for the karst plateau area,they are mainly influenced by the carbon,nitrogen and phosphorus content of plant leaves;for the karst crest depression area,they are mainly influenced by the nitrogen content of plant leaves,leaf dry matter mass and specific The plant community in the later stages of recovery(arboreal and terminal stages)was influenced by a combination of functional traits,but overall the effects of plant height and specific leaf area were most pronounced(2)The degree of influence of environmental factors on the functional traits of plant communities varies considerably with their composition.Early in the recovery period(grassland stage)it is influenced by soil capacitance,in the middle recovery period(irrigation stage,shrub stage,tree and irrigation stage)there is a gradual shift towards the most pronounced influence by soil carbon,nitrogen and phosphorus,and at the end of the recovery period(tree stage,terminal stage)the influence of soil organic carbon on plant functional traits is most pronounced.Most functional traits were not independently explained by one environmental factor,but rather showed a combination of environmental factors,with soil organic carbon,soil nitrogen content and soil phosphorus content having the highest rates of explanation.This study shows that during the restoration of karst plant communities,the ecological strategy of plant functional traits on plant communities gradually changes from an open strategy of resource acquisition to a conservative strategy of resisting barren environments;most environmental factors have a limiting effect on plant functional traits,and most plant functional traits can only perform their functions in specific environments.(3)During the restoration of karst plant communities,habitat resources gradually become richer,species diversity increases and functional dispersion decreases over time.As interspecific competition for resources in the plant community decreases,functional richness increases,the functional representation of species in the community decreases and functional redundancy increases.Functional redundancy tended to increase during karst vegetation restoration,with the functional redundancy index in the karst crest depression area(0.712)being greater than that in the karst plateau area(0.553)at the end of vegetation restoration.There were large differences in the rates of explanation for the functional diversity and functional redundancy of plant communities by environmental factors,but the rates of explanation for soil organic carbon content were more highly ranked.The correlation between plant community functional diversity and environmental factors was greater(22.22%;29.29%)than that between functional redundancy and environmental factors(16.67%;16.67%).The functional diversity of plant communities tended to increase and then decrease with increasing species diversity,and functional redundancy increased with increasing species diversity.In particular,for the karst plateau area with low species diversity,the vicinity of the tree and shrub stage may be a turning point for saturation of plant functional diversity in the area,while for the karst crest depression area with high species diversity,the vicinity of the shrub stage may be a turning point for saturation of plant functional diversity in the area.As plant community restoration proceeds,the available resources occupied by plant communities increase,resource use efficiency varies little,ecological niche differentiation increases,and interspecific resource competition.(4)With the increase of stability,both species diversity and functional redundancy of plant community gradually increased,and finally showed an increasing trend of saturation.In the process of karst vegetation restoration,both functional diversity and functional redundancy maintained the stability of plant communities,and functional redundancy maintained the stability(R~2=0.94;R~2=0.49)was greater than that of functional diversity(R~2=0.27;R~2=0.44).Among the factors affecting the stability and maintenance of plant communities,functional redundancy(R~2=0.94;R~2=0.49)>functional diversity(R~2=0.27;R~2=0.44)>species diversity(R~2=0.18;R~2=0.21)>functional traits(R~2=0.11;R~2=0.12),but the effect of biomass on stability maintenance was similar to or even higher than that of functional redundancy(R~2=0.80;R~2=0.64).Environmental factors have strong effects on species diversity,functional diversity and functional redundancy.Functional redundancy,functional diversity and biomass had direct and significant positive effects on stability,while environmental factors and species diversity had indirect positive effects on stability.This paper shows that the stability of plant communities in the early stages of vegetation restoration is mainly determined by community functional diversity,the stability of plant communities in the middle stages of restoration is determined by a combination of functional diversity and functional redundancy,and the stability of plant communities in the late stages of restoration is mainly determined by the pattern of functional redundancy.The mechanisms of species diversity and stability are:adaptation to habitat heterogeneity through functional diversity,and adaptation to habitat homogeneity through functional redundancy.With the restoration of karst vegetation,habitat heterogeneity decreases and homogeneity increases.As a result,functional diversity decreases and functional redundancy increases... |
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