Plant Community Roots And Soil Nitrogen In Desert Steppe In Response To Different Grazing Treatments

Grazing is the main utilize way in the nature grassland.Cattle and sheep are the major grazing species.Different kinds of livestock have different feeding behavior,which have effects on the growing of plant communities and complete among species.Consequently it is important theoretical and practical significance meaning to study the effects on mixed,cattle and sheep grazing.Root is the primary connection point of plants and soil,which determines the interaction surface between the soil and vegetation in the grassland.It is an important participant of soil ecosystem function and is also a vital organ to support the aboveground of plant and to fixed plants.The grass roots play a very important role for the whole ecological function.As a very important nutrient element.nitrogen pays an important role in grassland productivity.Nitrogen is one of the important limiting factors within many limiting factor in plant growth.Besides,nitrogen also has important impact on the grassland productivity,ecological system structure,function and the diversity of grassland community.This research set different grazing treatments in Xilamuren Desert Steppe of Baotou in Inner Mongolia.The treatments include sheep grazing alone,cattle grazing alone and mixed grazing and no grazing.Soil nitrogen,plant belowground net primary productivity(BNPP)and root turnover rate and root architecture under different grazing treatments were studied.The results showed that:1.after grazing for 14 months(about 2 growth seasons),cattle grazing alone and mixed grazing significantly increased 10?20 cm soil total nitrogen content,while cattle grazing alone increased the content of nitrate nitrogen,and cattle and sheep mixed grazing mainly improved organic nitrogen content;2.aboveground biomass in no grazing area was significantly higher than that of sheep grazing alone.cattle.grazing alone and mixed grazing areas,and the belowground biomass were not significant among each treatment;3.The root turnover and BNPP were increased by mixed grazing.Root turnover is slow in sheep grazing alone and cattle grazing area;4.There was no significant difference among different grazing treatments in root architecture parameters such as vegetation root length,diameter,surface area and volume,but the overall single grazing would decrease vegetation root length,diameter,surface area and volume and mixed grazing by the cattle and sheep would increase root architecture parameters.5.There are not significant differences of root architecture parameters of Stipa krylovii in different grazing treatments.While the classification of the root diameter showed that root length,volume and surface area in diameter of 4.0-4.5 mm and 2.5-3-5 mm in no grazing area were significantly greater than other grazing areas,indicating that there are more crude.roots of Stipa krylovii in no grazing area.On the whole,since the grazing time is relatively short,and the change of soil and plant root architecture parameters is not obvious.