Effects Of Beef Cattle Grazing On Vegetation Structure And Function Of Salinized Meadows

Arid,semi-arid,and semi humid regions worldwide are important activity areas for 41%of the population,and saline meadows are important ecological barriers for this vast human settlement,supporting 38%of the population’s livelihoods through grazing.Grazing is the most important and direct way of grassland utilization in saline meadows.Previous studies have focused on the improvement and utilization of saline soil,and exploring the effects and mechanisms of grazing systems and grazing rates on the structure and function of saline meadows communities is of great practical significance for the coordinated development of grassland ecology and production.Therefore,this paper relies on the saline grassland grazing experimental platform of the Linze Grassland Agricultural Experimental Station of Lanzhou University,and takes saline grasslands in the arid inland areas of northwest China as the research object.Two grazing systems,continuous grazing(CG1.33)and rotational grazing,as well as three grazing rates of 0.66 cattle/hm~2(RG0.66),1.33 cattle/hm~2(RG1.33),and 2.66 cattle/hm~2(RG2.66)are set up under the rotational grazing system,Clarify the effects of grazing system and grazing rate on the community structure and productivity of saline meadows,as well as the relationship between vegetation diversity and productivity.The main results are as follows:1.The Effect of Grazing on the Community Structure of Salinized MeadowsGrazing significantly reduced the height of communities and dominant populations(P<0.05).The coverage of communities and dominant populations under continuous grazing is higher than that under rotational grazing,and the density of communities and dominant populations under rotational grazing is higher than that under continuous grazing.Under the rotational grazing system,it increases with the increase of grazing rate.Grazing did not significantly alter the species richness,Shannon Wienner diversity index,and Pielou evenness index of the community(P>0.05).2.The effect of grazing on the productivity of saline meadow communitiesGrazing significantly reduced the aboveground biomass of saline grasslands,while under rotational grazing,the aboveground biomass decreased with increasing grazing rate,with rotational grazing being higher than continuous grazing;The underground biomass of rotational grazing is higher than that of continuous grazing,and the root to shoot ratio is less affected by grazing.RG1.33 significantly reduced the biomass of Phragmites australis stems and leaves,RG0.66 and RG1.33significantly reduced the biomass of sea leek leaves,and the biomass of moss and small flower rush stems and leaves is less affected by grazing.Continuous grazing significantly increased the crude protein content of plant community.Under the rotational grazing system,the crude ash content increased with the increase of grazing rate;The water content of herbage under continuous grazing is significantly higher than that under rotational grazing,and increases with the increase of grazing rate under rotational grazing system.The nitrogen content of vegetation under continuous grazing was higher than that under rotational grazing,and the phosphorus content of vegetation decreased with increasing grazing rate(P<0.05).The impact of grazing on the quality of the four dominant species is different:(1)The crude protein and ash content of Phragmites australis stems were higher under rotational grazing than under continuous grazing,and decreased with increasing grazing rate under rotational grazing system.RG1.33 significantly reduced the crude fat content of Phragmites australis leaves.The nitrogen content of reed stems under rotational grazing was higher than that under continuous grazing,and the phosphorus content decreased with increasing grazing rate under the rotational grazing system(P<0.05).(2)The content of acidic washing fiber in the stems of Triglochin maritimum under continuous grazing is higher than that under rotational grazing,while the content of crude ash is opposite.Under rotational grazing,the content is higher than that under continuous grazing,and under rotational grazing,there is a"camel shaped"change with the increase of grazing rate.Grazing significantly reduced the crude protein and fat content of Triglochin maritimum leaves,while the acid washing fiber content increased with increasing grazing rate under rotational grazing system(P<0.05).(3)Continuous grazing significantly reduced the crude protein content of Carex cinerascens stems,and the neutral washing fiber content of stems decreased with increasing grazing rate under rotational grazing system;The crude protein content of Carex cinerascens leaves shows a"hump shaped"change with increasing grazing rate.The crude protein content of Carex cinerascens moss leaves under rotational grazing was significantly higher than that under continuous grazing,while the crude fat content was opposite.Continuous grazing was higher than rotational grazing.Grazing significantly increased the content of coarse ash in leaves,while RG0.66significantly reduced the content of neutral detergent fiber(P<0.05).(4)RG2.66 significantly reduced the crude protein,neutral detergent fiber,and crude fat content of the stem of Juncus articulatus.Under the rotational grazing system,the crude ash content showed a"hump shaped"change with increasing grazing rate.Grazing significantly reduced the crude protein,neutral detergent fiber,and crude fat content of Juncus articulatus leaves.Under the rotational grazing system,the crude protein,neutral detergent fiber,and crude fat content of Juncus articulatus leaves increased with the increase of grazing rate,and continuous grazing was higher than rotational grazing.Continuous grazing significantly increased the content of coarse ash in leaves,and under the rotational grazing system,the content of acidic washing fibers showed a"saddle shaped"change with increasing grazing rate(P<0.05).3.The effect of grazing on the relationship between vegetation diversity and productivity in saline meadowsGrazing significantly affects the relationship between diversity and productivity(P<0.05).RG1.33 resulted in an increase in crude protein content as species richness increased.Species richness was also strongly correlated with other nutritional qualities of the forage.Under rotational grazing,species richness showed a significant negative correlation with neutral detergent fiber content,and a significant positive correlation with acidic detergent fiber content,crude fat content,and forage moisture content.Under the rotational grazing system,with RG0.66,species richness has the strongest regulatory effect on forage quality.The increase in species richness enhances forage quality and increases its nutritional value.Species richness also significantly affects the yield of forage,with RG1.33.The aboveground biomass decreases with the increase of species,while the underground biomass and root to shoot ratio increase with the increase of species.RG1.33 results in a decrease in aboveground biomass with increasing diversity,while underground biomass and root to shoot ratio increase with increasing diversity.The evenness index has the highest correlation with yield at RG0.66.As the species distribution becomes more uniform,the aboveground biomass increases,while the underground biomass and root to shoot ratio decrease.As an important production base of forage and seeds and an important area for the development of animal husbandry in China,rotational grazing is more conducive to the improvement of forage yield and nutritional quality than continuous grazing.Under the rotational grazing system,RG1.33 is the most effective for the protection of species diversity and the improvement of community structure and function.