Research On The Succession Characteristics Of Vegetation And Soil In Grass/White Clover Grassland Under Different Utilization Years

Grass/white clover grassland is one of the main mixed pastures in southern China,and plays an important role in the production of local grassland animal husbandry.It is easy to degrade due to improper managements,and will be reimproved and forms different utilization years grasslands.Most of previous studies focused on the characteristics of vegetation and soil at individual time scale,and the comparative analysis across long time scales was relatively rare,and the sensitive index of vegetation and soil to utilization years and the grasslands succession pattern are still not clear.In this study,we measured the important values of plant species,plant diversity,biomass composition,quantity traits of main grasses and white clover,nutrients in soils and herbages,and the relationship between plant diversity and their respective biomass and forage nutrients in cattle/goat grazing grass/white clover grasslands with different using years(long-term,medium-term and short-term).The purposes of this study: 1)to select the sensitive and inert indices in solis and vegetations to grassland utilization years,2)to clarity the successional trends of different grasslands,3)to derermine the suitable grassland utilization years for different livestock grazing grasslands.The main results are as follows:For cattle grazing grasslands,the important values of Dactylis glomerata and Trifolium repens were the medium-term > short-term and long-term,and plant richness and Shannon-Wiener indices in family level were the long-term >medium-term > short-term.The aboveground biomass compositions of Dactylis glomerata and Lolium perenne were short-term and medium-term > long-term,while for the native grasses it is long-term > short-term > medium-term.The tiller density and the small plants proportion of Dactylis glomerata were low in the long-term and middle-term grasslands,being a declining population,while they were high in short-term grasslands,being a growing population.The stolon density of Trifolium repens was long-term and short-term < medium-term.The total P content in herbages was long-term < short-term < medium-term.The total N and organic matter contents in soils changed steadily between two years.The total P and available P contents in solis were short-term and medium-term > long-term.The soil p H was short-term >medium-term > long-term.For sheep grazing grasslands,the important values of Dactylis glomerata and Trifolium repens were medium-term > long-term and short-term.The biomass proportions of forbs were long-term and short-term > medium-term.The tiller density of Dactylis glomerata was long-term < medium-term and short-term.The weight per plant or per tiller was long-term > short-term and short-term.The total P content in forages was medium-term > long-term > short-term.The total N and organic matter contents in soils were short-term > medium-term > long-term.The available P and p H in soils were short-term and medium-term > long-term.With the increase of grassland utilization years,the cattle/sheep grazing grasslands exhibited a degradation trend,the degradation characteristics is grasses plant aging,plant number and biomass composition decreasing,forage quality declining and soil acidification.For cattle/sheep grazing grasslands,the sensitive indices were soil P content and p H,whereas the inert indices were forage quality.The suitable utilization term for cattle/goat grazing grasslands was medium-term.