| Horqin sandy land,with fragile ecology,is a typical area in the ecotone of agriculture and animal husbandry in northern China.In recent years,the phenomenon of grassland desertification in this area under the influence of natural and human factors was still serious,the area of grassland desertification in some areas expanded,as well as the natural vegetation continued to deteriorate.Furtherly,the degree of grassland landscape fragmentation increased,and the types of desertification were extremely complex.In 2016,shifting sandy lands,semi-fixed sandy lands and fixed sandy lands were selected as the research objects in a family pasture of Zhalute Banner,Tongliao City.On the basis of fencing,measures such as mechanical leveling,sand barrier setting,artificial grass planting and enclosure fertilization were taken to restore and control the desertification grasslands according to local conditions,and compared with the same type of untreated sandy lands,so as to explore effective ways to accurately restore different types of sandy grasslands.Different restoration treatments were adopted for each type of sandy lands,and random trials were carried out and set three repetitions.The area of each community was 900 m~2.From 2019 to 2020,the plant community characteristics of each treatment were observed by conventional methods in August every year,and the quadrat area was(1×1)m~2,randomly arranged,20 repetitions.The plants in the sample plot were divided into three functional groups:shrub and subshrub,perennial herb,annual and biennial plant.In addition,the height,density,coverage,aboveground biomass the community and each functional group and the nutritional quality of community plants were measured.In 2020,soil samples were collected in the same sample points for the above determination to determine the soil physical and chemical properties and analyze the composition of soil nematode nutritional groups.The community change law and vegetation restoration effect of different types of sandy grasslands were compared.The main results were as follows:(1)In the fourth and fifth years of treatment,the vegetation of all sandy grasslands recovered significantly,showing different community characteristics.The number of plant species in the three types of sandy grasslands increased prominently,and the diversity tended to be rich.In shifting sandy lands,in addition to the normal growth of plants planted,other plants also invaded and the species richness increased;the natural invasive species in semi-fixed sandy lands and fixed sandy lands increased memorably,the composition was complicated,and the diversity was remarkably improved.Among them,the species richness of semi-fixed sandy lands increased evidently,the evenness decreased,and the dominance did not change markedly;the dominance of species in fixed sandy lands increased,the richness and evenness decreased,and the whole tended to be stable.(2)The characteristic indexes of functional groups plants and communities in the three types of sandy grasslands generally increased observably.The common features were that the height increased dramatically,the density,coverage and aboveground biomass of shrubs and subshrubs and perennial herbs increased dramatically,the density and coverage of annual and biennial plants decreased substantially while the aboveground biomass did not change prominently.In 2019,the community height of shifting sandy lands,semi-fixed sandy lands and fixed sandy lands increased by 64.5 cm,48.2 cm and 23.8 cm respectively,the total coverage increased by 37.3%,34.1%and 25.3%separately,and the aboveground biomass increased by 295.4 g/m~2,362.2 g/m~2 and 246.3 g/m~2 severally.In 2020,the community height of the three types of sandy grasslands increased by 51.3 cm,36.7 cm and20.2 cm respectively,the total coverage increased by 18.4%,25.0%and 20.5%separately,and the aboveground biomass increased by 200.1 g/m~2,189.8 g/m~2 and 186.7 g/m~2 severally.There was no significant change in crude protein content,but the content of crude fat increased memorably,the contents of acid detergent fiber and neutral detergent fiber showed an increasing trend,and the content of crude ash decreased dramatically.(3)The soil of the three types of sandy grasslands tended to be stable,and the contents of organic matter,available phosphorus and available potassium increased.Particularly,the changes of various indexes of shifting sandy lands and semi-fixed sandy lands were not significant,and the corresponding nutrient contents of fixed sandy lands increased dramatically.The organic matter contents of 0～10 cm,10～20 cm and 20～30 cm soil layers increased by 2.86 g/kg,12.60 g/kg and 13.65 g/kg respectively;the content of available phosphorus in 0～10 cm soil layer increased by 3.29 mg/kg,which in 10～20 cm and 20～30 cm soil layers increased by 3.25 mg/kg similarly;the content of available potassium in each soil layer increased by 52.87 mg/kg,57.00 mg/kg and 42.93 mg/kg separately.The soil fluidity of shifting sandy lands and semi-fixed sandy lands completely disappeared,and the change range of soil p H value and alkali hydrolyzable nitrogen content was small;the p H value of each soil layer in the fixed sandy lands decreased by 0.55,0.87and 0.94 severally,and the content of alkali hydrolyzable nitrogen increased prominently by8.42 mg/kg,21.78 mg/kg and 22.24 mg/kg individually.(4)In the process of vegetation restoration in sandy lands,the composition of nutrient groups,diversity indices and ecological function indexes of soil nematodes changed differently.In the soil nematode communities,the number of bacterivores was the largest,followed by plant parasites and fungivores,and omnivores-predators were the least.After4～5 years’vegetation restoration,the variation range of nematode diversity,dominance and richness was still small.There was no significant change in the evenness of nematodes in shifting sandy lands and semi-fixed sandy lands,while the evenness of nematodes in fixed sandy lands decreased observably.The enrichment index and structure index of nematodes increased in shifting sandy lands;the enrichment index of semi-fixed sandy lands decreased and the structure index increased;the enrichment index of fixed sandy lands increased. |
