Study On Evapotranspiration And Ecological Effects Of Grassland Under Different Utilization Patterns In Saihanwula,inner Mongolia

Inner Mongolia grassland is located in the continental arid and semi-arid climate zone,which is with the feature of climate fluctuation,as well as fragile and severe.Therefore,the grassland ecosystem in the arid and semi-arid interlaced agro-pasturing areas is more prone to degradation.Precipitation is the main source of water supply in arid and semi-arid regions,and it is of great significance for vegetation restoration in this region.On the other side,evapotranspiration and runoff are the main water loss channels in arid and semi-arid regions.The vegetation restoration will inevitably increase water consumption and soil water loss.Therefore,it is very important to accurately estimate the evapotranspiration and rainwater resource utilization potential index in arid and semi-arid regions.In order to provide suggestions and theoretical support for regional vegetation allocation and grassland protection and rational utilization,this paper studied grassland evapotranspiration,rainwater resource utilization potential index and ecological effects under different conservation and utilization methods.In this study,the eddy correlation observation technique was used to collect observation data during grassland growth period.The changes of species composition,importance value,aboveground biomass,coverage and diversity under the three types of grassland conservation and utilization were analyzed.The ecological effect and its changing trend were evaluated.The SEBAL model was used to simulate ET and its change from 2000 to 2019,and analyze the spatio-temporal variation characteristics of ET.We calculated the RUP,studied the influences of grassland biomass,richness,abundance and coverage on ET under different utilization modes.The main results were as follows:1)Changes of evapotranspiration and meteorological factors in the growing season of grassland in the study area were observed.In our study,During the experimental observation period,evapotranspiration showed a downward trend from May to June,an upward trend from June to August and reached the peak,and continued to decline after August.The evapotranspiration in the growing season was 313.8 mm.The carbon source and sink effect of grassland fluctuated,and the volumetric water content of soil was consistent with the change of rainfall,and rainfall mostly concentrated in the later stage.2)The method of using water deficit to evaluate whether existing water resources can satisfy the sustainable development of ecosystem is also suitable for Chifeng area.Based on large-scale research,we found that the spatial distribution pattern of the actual ET of grassland was consistent with the potential of rainwater utilization in arid and semi-arid regions.Chifeng City,where Saihanwula located,was taken as an example to study the relationship between large-scale ET and rainwater resource utilization potential.The results showed that the spatial distribution pattern of actual ET matched the RUP.The regions with high ET(>400 mm)corresponded to a relatively small potential of rainwater recycling,while the regions with medium and low ET(<400 mm)generally corresponded to a relatively large potential of rainwater recycling.In our study,most regions were in the state of annual dynamic water surplus.3)The study showed the characteristics of spatio-temporal dynamics of ET in Saihanwula.Through remote sensing and spatial analysis,the high value area of actual ET(>400 mm)was mainly distributed in the forest ecosystem area.In terms of time changes,the actual ET showed an overall increasing trend from 2010 to 2019.From 2000 to 2009,the area of the high value area(>400 mm)of the actual ET showed a downward trend;while the area of the median value area(300?400 mm)showed a rising trend at first and then a downward trend.For the area of water surplus in the reserve,it gradually decreased from 2000 to 2006,and increased significantly from 2006 to 2012.The potential of rainwater resource utilization decreased year by year during 2012 to 2019.The grassland under three different utilization patterns was in the state of annual dynamic water deficit from 2016 to 2019.The results indicated that meteorological factors had significant influence on ET.4)The study revealed the correlation between the actual ET and the main growth indicators of grassland under different conservation and utilization patters.According to our study on ET from Saihanwula during 2016 to 2019,There was a positive correlation between actual ET and evenness index and biomass of grassland under different conservation and utilization methods,and the correlation was stronger in fenced grassland and weaker in grazing grassland.The diversity index of fenced grassland and cut-grassland varied in a wide range and was positively correlated with actual ET,while the diversity index of grazing grassland was negatively correlated with actual ET.The actual ET of grazing grassland and fenced grassland increased with the increase of total coverage,but the correlation between actual ET and total coverage of cut-grassland was weak.5)The study found the changes of grassland ecological effects under different conservation and utilization methods.According to the comprehensive study on the effects of ecosystem diversity,structure,quality,function and wind-sand protection,we concluded that the ecological effect for grassland was positive by fencing and restoring,negative by cut-grass land,and zero by grazing grassland.The results indicated that the fencing and restoration measures of degraded grassland were beneficial to improve the ecological environment,while perennially grazing was not conducive to the improvement of the ecological environment.Fencing restoration was an effective measure to realize the restoration and succession of degraded grassland vegetation to climax community.6)The study found that the grassland enclosure model was more conducive to the restoration of vegetation and was suitable for the restoration of degraded grassland in the agro-pastoral ecotone of arid and semi-arid area.In arid and semi-arid regions with precipitation less than 350 mm,it is suggested to give priority to enclosure protection and restoration,and control the enclosure protection and Mowing grass time of grassland at the same time,so as to improve economic benefits on the premise of protection.In the seriously degraded grassland which needs to be replanted artificially,herbage-remediation should be the first step.Secondly,select tolerant native species which suitable cold and drought,and optimize the planting density of herbaceous plants,so as to reduce the water consumption of grassland,alleviate drought stress,and improve the conservation and restoration efficiency of grassland in agro-pastoral ecotone.Enhance social and economic benefits and maximize the benefits of ecological restoration on the premise of realizing rational utilization of regional water resources.