| Climate change(such as global warming) and change of land use(such as grazing intensity increased) are two main driving force of global environmental change.With the change of global warming and land use, the stability of ecosystem has been seriously affected. the abandoned alfalfa grassland in the semi arid area of the Loess Plateau as the research object of the study, to explore the effects of artificial simulated grazing intensity on grassland ecosystem in semi arid area of the Loess Plateau in the background of global warming, in order to provide a scientific basis for the future development of agriculture and animal husbandry and the management and rational utilization of grassland ecosystem in the area. Mowing intensity as the main factor, warming as the secondary factor in the experiment, the mowing intensities includes 8 levels, each set warming(W) and not warming(N) under mowing intensity, in total of 16 treatments.The result show that:1) Daily average air temperature and humidity in warming were higher than in no warming 1.7 ℃ and 3.6%, respectively;In the two growth seasons, soil temperature increased by 0.74 ℃ and 0.72 ℃,Soil moisture content decreased 3.53% and 3.07%, respectively,Warming compared with no warming.In the 2014 growth season, soil moisture content in warming is higher than in the no warming under the same mowing intensities,however,it showed the opposite trend in the 2015 growing season.2) The effect of mowing intensities on plant communities aboveground biomass was significant(p<0.01).Its trend accorded with normal distribution(Its has maximum biomass in medium mowing intensities). Warming can increase the aboveground biomass of plant communities, but it was not significant(p>0.05).In warming, its tend conformed to significantly normal distribution between the mowing intensities and the trend of biomass recovery.3) With the increased of the mowing intensity, species loss rate increases in 2014,but not significant(p>0.05);Warming can alleviate the effects of mowing intensity onspecies.In warming, there is a quadratic function relationship between species recovery rate and mowing intensities, but not significant(p>0.05);In warming, there is a significant linear relationship between mowing intensity and species recovery rate(p< 0.05).4)Organic carbon of alfalfa increased linearly with time(p<0.05), The content of total nitrogen and total phosphorus was decreased linearly with time(p<0.05).In 2014, mowing intensity had significant effect on total nitrogen and total phosphorus(p<0.05), but mowing intensity had no significant effect on total organic carbon under warming(p>0.05), and mowing intensities had a significant effect on total organic carbon no warming(p<0.05).In 2015, mowing intensities had no significant influence on total organic carbon, total nitrogen and total phosphorus(p>0.05).5) mowing intensity are no significant to soil organic carbon(SOC)(p>0.05);In warming, with the increase of mowing intensity, the content of soil organic carbon decreased;In no warming, with the increase of mowing intensity, the content of soil organic carbon increased.Total nitrogen and total phosphorus have same variation trend.In 2015, there is a quadratic function relationship between mowing intensity and the content of soil organic carbon in warming and no warming, and different mowing intensities has significant effect on the content of soil organic carbon(p<0.05).In warming, mowing intensity had no significant effect on the content of soil total nitrogen(p>0.05);In no warming, there is a significant linear relationship between mowing intensities and the content of total nitrogen(p<0.05). Mowing intensities had no significant effect on content of total phosphorus in warming and no warming(p>0.05). |
PDF Full Text Request