| The most effective way of ecological restoration to control rocky desertification is to restore vegetation in rocky desertification areas.How can quickly increase the vegetation rate and accelerate the succession efficiency of vegetation in as little time as possible.This requires a better understanding of vegetation succession laws.To clarify the succession laws and driving factors of plant communities in different degrees of rocky desertification areas,and explore the succession laws of species diversity,leaf functional traits of constructive species and the spatial pattern of community species with rocky desertification.Based on species diversity succession theory,leaf economic spectrum theory and niche differentiation theory,in 2017-2019,the ecological environment of Guizhou plateau,which represented general structure of different landforms types and rocky desertification degrees of karst in South China,Bijie Salaxi of potential-slight rocky desertification of plateau mountain,Guanling-Zhenfeng Huajiang of moderate-intensive rocky desertification of plateau gorge and Qiandongnan Shibing of non-potential of mountain gorge was selected as the study areas,carried out location observation on38 field sample sites in the study area,and 38 plant communities and constructive species in different degrees of rock desertification succession in the study area were collected and sampled.Using one-way ANOVA,redundancy analysis,linear regression analysis,structural equation model and principal component analysis,etc.,the relationship between species diversity and climate and soil in different degrees of rocky desertification areas,the relationship between leaf functional traits of constructive species and climate,leaf carbon,nitrogen and phosphorus,soil and plant growth form,and the relationship between the spatial pattern of community species and topography were analysed,by studying the plant species diversity in different degrees of rock desertification succession,the leaf functional traits of constructive species in plant communities and the spatial pattern and interspecies correlation of plant communities,clarifying the successional law of species diversity,functional traits of constructive species,spatial patterns of plant communities and interspecies relationships on the rocky desertification gradient,revealing the factors and driving mechanisms that affected their changes,proposing plant community optimization techniques,integrating plant community optimization and control techniques and conduct application demonstration and verification,to provide scientific and technological reference for improving ecological efficiency of vegetation in rocky desertification control.(1)As the intensity of rocky desertification,species diversity showed a downward trend.In the research area of karst plateau mountain,percentage of exposured rock(PER)and total potassium(TK)had the greatest impact on the species diversity of the arbor layer;Available potassium(AK)had the greatest impact on shrub layer species diversity.The species diversity of the herb layer was most affected by available nitrogen(AN)and pH.Climate and soil explained the differences of 9.4%and 65.9%,respectively,indicating that the species diversity was greatly affected by the soil in the research area of karst plateau mountain.In in the research area of karst plateau gorge,PER and AN had the greatest impact on the species diversity of the arbor layer;Available phosphorus(AP)and manual average temperature(MAT)had the greatest impact on shrub layer species diversity;The herb layer species diversity was most affected by manual average precipitation(MAP).Climate and soil explained the differences of 14%and 73%,respectively,indicating that the species diversity was greatly affected by the soil in the research area of karst plateau gorge.In research area of karst mountain gorge,MAT had the greatest impact on the species diversity of the arbor layer;MAP had the greatest impact on the species diversity of the shrub layer;the species diversity of the herb layer was most affected by AN and total phosphorus(TP).Climate and soil explained the differences of 23%and7.6%,respectively,indicating that species diversity was greatly affected by climate in research area of karst mountain gorge.The study found that species diversity in the study area is affected by N and P,and more attention should be paid to the coupling relationship between N and P and rocky desertification in the future.The results can provide theoretical basis for vegetation restoration in rocky desertification area.(2)As the intensity of rocky desertification in research area of karst plateau mountain,specific leaf area(SLA),net photosynthetic rate(Pn)and water use efficiency(WUE)showed an upward trend,while leaf thickness(LT)showed a downward trend.Leaf area(LA)and leaf dry matter content(LDMC)tend to increase first and then decrease with the intensity of rocky desertification;As the intensity of rocky desertification in the research area of karst plateau gorge,SLA and leaf phosphorus content(LPC)showed an increasing trend,while LT and LA showed a decreasing trend.Pn and WUE tended to increase first and then decrease with the intensity of rocky desertification,while transpiration rate(Tr)decrease and then increase;In the research area of mountain gorge,as the intensity of rocky desertification,LT and LDMC showed a trend of increasing first and then decreasing with the intensity of rocky desertification,while SLA,Pn and Tr showed a decreasing trend and then increased.Overall,intensive rocky desertification areas had higher SLA values and lower LDMC,while non-rocky desertification areas had lower SLA and higher LDMC and LT,which indicated the plant evolved from a pioneering strategy in the early succession to a conservative strategy in the late succession.(3)RDA was conducted on the leaf functional traits and climate,leaf carbon,nitrogen and phosphorus,soil and plant growth form of constructive species in the research areas.Analysis showed that LPC and pH had the greatest impact on WUE,AN had the largest impact on Pn and SLA,MAT had the largest negative correlation on Tr,LDMC had the largest LC:P impact,and growth form(GF)had the greatest impact on LT.The four groups of climate,leaf carbon,nitrogen and phosphorus,soil and plant growth form explained 29.4%of the changes in leaf functional traits,of which the individual climate,leaf carbon,nitrogen and phosphorus,soil and growth type explained the differences of 6.8%,6.2%,10.8%and 0.4%,respectively.Structural model equations showed that LPC,LC:P and pH and AN in soil factors directly affected SLA,Pn,Tr and WUE,while the manual average precipitation(MAP)and MAT in climate factors indirectly affected SLA,Pn,Tr and WUE through the changes of LPC,pH and AN.The research results are helpful to reveal the driving factors of leaf functional traits in rocky desertification areas.(4)Using the point pattern g(r)function to analyse the spatial patterns of the communities and dominant species in study areas,it was found that the spatial patterns of the plant communities and main species in study area of karst plateau mountain and mountain gorge were randomly distributed,while the plant communities and main species in study area of karst plateau gorge were mainly clustered.There was no correlation between Pinus armandii and Quercus fabri populations within observation scale in karst plateau mountain,and there was no or positive correlation between Symplocos stellaris and Pinus armandii and Quercus fabri populations within observation scale;There was no or positive correlation between Cladrastis platycarpa and the Broussonetia papyrifera population within observation scale in karst plateau gorge,while there was no or negative correlation between Cotinus coggygria and Broussonetia papyrifera and Broussonetia papyrifera population;There was no or positive correlation among Pinus massoniana,Cupressus funebris and Cunninghamia lanceolate population within observation scale in karst mountain gorge.The results showed that from research area of karst plateau gorge of moderate-intense rocky desertification to research area of karst plateau mountain and mountain gorge of potential-slight,the spatial pattern of community changed from cluster distribution to random distribution,and the relationship between dominant populations changed from negative correlation and uncorrelation to positive correlation and uncorrelation,indicating that the interspecific relationship improved with the positive succession of rocky desertification.CCA showed that aspect,slope and percentage of exposued rock(PER)affected the spatial distribution of community species.Terrain factors explained 23.15%change of species spatial distribution,indicating that habitat heterogeneity had certain influence on species spatial pattern in the deterministic process.(5)Using the improved index system of urgency for management of plant community structure to evaluate the plant community structure in the study areas.The evaluation showed that the density of the plant community in the karst plateau mountain and mountain gorge was higher and the forest mixed degree was lower.The species was limited by the N element;The spatial distribution of forest stands in the karst plateau gorge plant community needed to be optimized,and the cluster distribution was optimized to a random distribution.Similarly,the dominant species in the community also had the problem of N element limitation.The results revealed some common problems existing in the plant community structure of rocky desertification,and put forward optimization measures and techniques.According to the deficiencies of the community,combined with the study of the ecological strategy of the leaf functional characteristics of constructive species,structural management was carried out in the study areas in different degrees of rocky desertification.The community structural management technology was used to demonstrate the research area of karst plateau mountain,plateau gorge and mountain gorge.At present,research areas of plateau mountain,plateau gorge and mountain gorge have demonstrated areas of12.35 hm~2,10.37 hm~2 and 18.63 hm~2,respectively.After demonstration,the species diversity of the communities and vegetation coverage increased slightly compared with that before demonstration.The research can provide a feasible technical reference for the management of plantation communities,the improvement of ecological benefits and and the restoration of species diversity in the karst rocky desertification area. |
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