Plant Community Structure And Function Response To Different Land Use Patterns In Hunshandake Sandland Of Northrn China

Grassland is a part of terrestrial ecosystem in the earth,which plays a very important role on cleaning air,carbon sequestration,releasing oxygen,providing livestock products,maintaining biodiversity,wind prevention and sand fixation.Grassland ecosystem biodiversity,net primary productivity,soil physical-chemical properties,soil nutrient cycling have a significantly response to human disturbance via land use changed(mowing,grazing).The space heterogeneity of Hunshandake sandland was very high,dune,lowland and wetland are all included in the region,plant community was abundant also.Different land use influence grassland of different habitat,we can get a more reasonable grassland management to perfect and restore grassland ecosystem in north china.Our study was carried out for 5 years,which was mainly composed of field investigations and sampling,laboratory experiments and data analysis.1.Our result indicated that moderated grazing was advantageous to plant species richness,however,plant species richness,plant community coverage and height of grassland ecosystem with mowing were all significantly higher than grazing in 2008(P<0.05).The plant species richness of the most plant community with mowing was significantly declined from 2008 to 2012,meanwhile,plant species richness of community with grazing was dynamic stability,the latter was significantly higher the former in 2012 years(P<0.05).For lowland and wetland,plant species richness with grazing were both significantly higher than that with mowing in 2012,despite there was an opposite result in 2008(P<0.05).The result showed that grazing maintain stable net primary production,in spite of there were significantly higher aboveground biomass and belowground biomass in mowing sampling than grazing(P<0.05).Aboveground biomass with mowing were significantly declined from 6.05 to 49.84%,decreased from 7.08 to 60.13%for belowground biomass in 5 years.Aboveground biomass and belowground biomass with grazing were both stable in our experimental treatment.The major provider of Hunshandak sandland were lowland and wetland plant ecosystem,there were significantly decline tendency for biomass with mowing(P<0.05).2.Land use changed affected soil chemical properties and quality,mowing made soil nutrient significantly declined in 5 years experiment,by contrast,grazing maintained soil nutrient and cycling stable(P<0.05).The soil organic carbon,soil total nitrogen,soil available nitrogen and soil available phosphorus all had a significantly downtrend response to mowing,soil organic carbon declined from 7.8 to 22.05%,soil available phosphorus declined from 3.82 to 31.53%,soil total nitrogen declined from 9.59 to 31.65%(P<0.05).Soil nutrient in grazing were more stable,there were no significantly variation of soil potassium both in mowing and grazing(P<0.05).Soil total nitrogen,soil available nitrogen,soil available phosphorus and soil organic carbon of lowland and wetland with mowing all significantly reduction(P<0.05),there were no significantly variation of the above indicators with grazing.3.Soil physical property was stable and equilibrium state with grazing.There were no response to mowing and grazing,both soil bulk density and soil water content did not have significantly variation with different land use in our result(P>0.05).There was the same conclusion for dune,lowland and wetland with mowing and grazing(P>0.05).4.According to regression model(Stepwise multiple linear regression)with aboveground biomass and belowground biomass as a continuous variable were used to determine the general relationship between biomass and species richness various and soil nutrient various,precipitation various and soil physical property various.Our result showed that soil available phosphorus were the driver abiotic factor for both aboveground biomass and belowground biomass with mowing,soil water content was the limited abiotic factor for aboveground biomass with grazing,by contrast,soil available potassium was the most important ecological factor for belowground biomass with grazing.5.To examine the effects of soil nutrient,soil physical property and precipitation with land use changed on plant species richness via regression model(Stepwise multiple linear regression),we got the limited abiotic factor for biodiversity.Soil available potassium was the limited abiotic factor for plant species richness with mowing,soil available phosphorus was the driver factor for plant species richness with grazing.For dune,lowland and wetland,there was the most ecological factor for plant species richness with mowing and grazing.In conclusion,we showed that mowing have a significantly impact on grassland ecosystem structure and function,whereas grazing had almost no effect.Grazing maintained stable aboveground biomass,belowground biomass,plant species richness and soil nutrient,which was more reasonable and effective grassland management for Hunshandak sandland.