Restoration Succession Mechanism Of Degraded Leymus Chinensis Grassland In Northern China

Leymus chinensis is a rhizomatous grass with strong fertility and stress resistance and widely cultivated on the grasslands of Eurasia.Different grassland types of L.chinensis in China often form dominant species or single dominant species community,such as typical grassland and meadow grassland,and hidden meadow.L.chinensis grassland is an excellent pasture and mowing grassland,which plays an important role in the local economic development of the northern grassland area.Due to long-term unreasonable overuse,different areas of L.chinensis grassland occur degradation of different degrees,so that different types of L.chinensis grassland also exist widespread restoration succession community.Therefore,compared with plant structure,biological diversity and productivity,and the space dynamic comparative advantage of L.chinensis in different areas,different types of degraded grassland restoration succession,and combined with the community the analysis of the relationship between productivity and diversity.The paper reveal the ecological mechanism of L.chinensis degraded grassland restoration succession of L.chinensis grassland protection,reasonable exploitation and grassland management to provide scientific basis.This research take different types of degraded grassland in north China as the research object,at the peak of community productivity accumulation.Vegetation survey and population sampling of L.chinensis were carried out for two years.The main areas are the grassland in the south of the Songnen plain(Changling stud horse farm,Jilin province),the grassland in the transition zone between the great Hinggan mountains and the Songnen plain in the north of the Songnen plain(Tumuji nature reserve,Jalainteqi),Hulunbuir grassland(Sheltala ranch)and Xilingol grassland(Baiyin Xile ranch).The concrete results are as following:1.A total of 182 species,belonging to 114 genera,37 families,were recorded in four sampling sites in the past two years.Compositae,gramineae and leguminous family are the dominant families in the grassland of north China,accounting for 49.47% and 51.58% of the total genera,46.62% and 48.57% of the total species in the two years respectively.In the past two years,there were 66 species of 49 genera in 22 families in Changling,111 species in 74 genera in 28 families in tumuji,and 95 species in 67 genera in 29 families in Hulunbuir,and 93 species in 62 genera in 25 families in Xilingol.Species richness was highest in Muji and lowest in Changling.2.Among the frequency distribution grades of plant species,the proportion of class E is lower in all the four areas;moreover,the grassland degeneration is relatively serious under mowing,and most of the early stage of restoration succession belongs to D.The important values of L.chinensis were the highest in the high-density communities in the late stage of restoration succession in the four areas.The middle-density communities in the middle stage of restoration succession and the low-density communities in the early stage of restoration succession under the grazing conditions of Hulunbuir and Xilingol were the highest in the two areas respectively.3.The percentage of annual plants in Changling was higher than that of ground bud plants.In plant growth type,branching plants dominated Changling and Tumuji,while clumps dominated Hulunbuir and Xilingol.The grassland in the four regions dominated by taste-rooted plants,and the water ecology type dominated by mesophytic plants.The proportion of MNDC is the highest in all the four regions.4.Compared with unused pettern,the productivity of L.chinensis community reduced significantly under mowing and grazing petterns in four areas in two years.The productivity of dominant species was not significantly different between restoration and succession communities under the grazing pettern in Changling in 2014,but the mowing and unused pettern of Changling in 2013,as well as the different utilization petterns in other areas in the two years improved significantly with the restoration and succession process.In 2014,the ? diversity of plant species in L.chinensis was generally increased in four regions under the mowing and grazing petterns.In two years,the ? diversity reduced generally in four areas under grazing pettern.The ? diversity of species in Tumuji and Hulun Buir areas was higher than that in Changling and Xilingol.There was a significant correlation between productivity and species diversity index of L.chinensis community in four areas,but no correlation between mowing and grazing petterns.5.The vegetative ramet height of L.chinensis in the four areas reduced significantly in grazing pettern,and the mowing pettern of Tumuji and Hulun Buir reduced significantly.The rhizome length of L.chinensis populations in the four regions was significantly different from each other in the succession communities,and the unused pettern was generally relatively high among the utilization patterns,some of which reached significant levels.The number of ramets in the population of L.chinensis in the four regions increased significantly with the restoration and succession process.The population density of L.chinensis increased significantly in Changling under the grazing pettern,and decreased significantly under the grazing and mowing petterns in Hulun Buir in 2013.With the exception of some individuals,the individual biomass of L.chinensis population increased with the process of restoration and succession,and the differences among restoration and succession communities were significant.6.The number of vegetative ramets of different age classes in the populations of L.chinensis in the four regions was 1age(a),followed by 2a.Only in some regions or years,there were 3a,and the number and proportion were lower,indicating a growth age structure.The number of ramets in L.chinensis population was also 1a,and there were 2a and 3a in some years or under the utilization pattern,which showed a growth age structure.The length of rhizome of L.chinensis in Changling,Tumuji and Hulun Buir areas dominated by 2a,followed by 1a or 3a,which was a stable age structure.The biomass of ramet and rhizome in four regions were all growth age structure and stable age structure.The productivity of ramet of different age classes of L.chinensis population in four regions was the highest at 1a,with significant differences among different age classes,and only partial differences in rhizome storage force among different age classes were significant.In the four regions,the vegetative fertility of L.chinensis populations in different restoration and succession communities was higher than 3a in 1a and 2a fractionals,and the vegetative fertility of rhizome was highest in 1a,respectively 2a and 3a.In summary,there were two common results in the process of restoration and succession of degraded L.chinensis grassland in northern China.One was that the ? diversity of the plant species of L.chinensis community was generally decreased in different regions with different utilization methods.The other was that the population frits of L.chinensis community with different utilization methods in different regions were of increasing age structure.The main ecological mechanism lies in the strong ramet fertility of L.chinensis.L.chinensis increases the density and productivity of its population in the community through constant ramet fertility,resulting in the loss of annual plant growth space and disappearance from the community.The rramet of L.chinensis population always maintains its increasing age structure under various petterns intensity,which is the origin and the basic guarantee of self-organization restoration succession of degraded L.chinensis grassland.