Plant And Soil Communities Of Different Restoration Years In Karst Fault Basin Area Of Yunnan Province

The rocky desertification is serious and the vegetation restoration is difficult in the faulted basin.Taking certain artificial measures according to the natural restoration law of vegetation is an important way to accelerate the vegetation restoration process.This study takes Daheishan,Pingbian County,Yunnan Province,located in the Karst Fault Basin Area,as an example.Investigated and sampled the natural vegetation of different abandoned year(the abandoned land in that year,abandoned land for 3,6,20,40 years)and almost undisturbed primary forests,analyzing vegetation dynamics during vegetation restoration,soil and seed bank characteristics closely related to vegetation,and their effects on vegetation restoration and response.Fully understand and recognize the natural restoration process of vegetation and reveal the mechanism of community restoration succession,aiming to provide basis for the restoration and reconstruction of degraded ecosystems.Research indicates:(1)A total of 181 vascular plants in 129 genera and 72 families were recorded in the study area.The families with more species distribution include Rosaceae,Lauraceae,Gramineae,Compositae,Polygonaceae,Ulmaceae,Araliaceae,Aquifoliaceae,Moraceae,Oleaceae.During the process of vegetation restoration,the number of families,genera and species in the species composition of the community gradually increased.The herb is gradually transformed from the early Xiyang,drought-tolerant,and barren-resistant herbs to the herbs and ferns that are shaded.Viburnum foetidum,Rubus xanthoneurus,and Itoa orientalis are pioneer species of vegetation restoration in the region.Their early appearance created conditions for the restoration of other plants,and the late positive shrubs were gradually welcomed.Shade species replacement.The tree species in the arbor layer transition from a sunny to a neutral,and gradually change to a negative.After 40 years of restoration,the plant species of the plant community were consistent with the original forest community,and both were made by the Stranvaesia davidiana and Schefflera octophy;the individuals in the abandoned land community were short and dense.With the increase of recovery years,the height of woody plants gradually increased,the density decreased,the coverage of arbor layer gradually increased,and the coverage of shrub layer and herb layer rose first and then decreased.After 40 years of restoration,the diversity,coverage and density of plant communities have basically reached the level of primary forests,and the community height still has recovery space;the species diversity of plant communities increases with the increase of recovery years,and the highest is 40 years,and slightly higher.In the original forest,the difference was not significant(P>0.05).However,the diversity of species at different levels is different.(2)A total of 97 species were released from the soil seed bank in the study area,belonging to 87 genera and 45 genera.The total number of soil seed bank species was the highest at 6 years of recovery,with 47 species.The total density of soil seed bank varied from 1622 to 17233 grains/m2,which showed a downward trend with the increase of recovery years.Among them,the number and density of herbaceous species occupy a high proportion in the soil seed bank,while the proportion of trees and shrubs is relatively low.The similarity coefficient of soil seed bank and surface vegetation in different recovery years is 0.13?0.21,the similarity is generally low,and the maximum value appears when recovering for 6 years.Before returning to arbor forest,the soil seed bank has a higher species richness than aboveground vegetation,and the opposite is true after the formation of arbor forest.The Shannon-wiener index and Simpson index of the soil seed bank are lower than those of aboveground vegetation.In general,the soil seed bank in the study area is rich in seed reserves and high in quality,which can provide a matrix for the natural regeneration of forests in the area.However,the vegetation recovery potential of the soil seed bank is still small,and vegetation restoration requires appropriate human intervention and regulation.(3)In the early stage of vegetation restoration,especially from abandoned land to shrub community stage,the plant growth absorbed more nutrients from the soil than it returned,leading to a decline in soil fertility.But with the further restoration of vegetation,soil fertility gradually improved.Soil physical properties,soil water holding capacity,soil organic matter,total nitrogen,ammonium nitrogen and available potassium contents all showed an increasing trend with the recovery of vegetation.Soil phosphorus showed a contrary response to other soil properties.The total phosphorus content in the soil increased significantly in the three years period from abandoned land-abandoned for 3 years land,and then decreased with the increase of recovery years,but all the communities were improved compared with those in "abandoned" lands,with a range of 0.25?1.29 g/kg.The content of available phosphorus decreased gradually with the increase of recovery years,and the range of variation was 3.37?46.59 mg/kg.The redundancy analysis of vegetation characteristics and soil physical and chemical properties showed that there was a negative correlation between soil available phosphorus content and soil bulk density and tree layer and shrub layer diversity index.It is suggested that phosphorus is the limiting element in this area,and it can be considered to supplement phosphorus during artificial vegetation restoration to accelerate vegetation restoration.After 40 years of restoration,the soil physical properties,water holding capacity,soil organic matter,total nitrogen and available phosphorus content are still somewhat different from those of original forest.