The Effect Of Precipitation Variation On The Utilization Of Water Fall Of Stipa Grandis

Typical grasslands are one of the most representative types of grasslands in semi-arid regions,and water is the main limiting factor in the region.In-depth research on grassland water use under different precipitation conditions can provide a reference for understanding the ecological adaptability mechanism of grassland to climate change.In this study,Stipa grandis typical steppe in Inner Mongolia was selected as the research object.The plant water physiological characteristics under the conditions of natural precipitation and simulated precipitation changes are observed by means of lysimeter,infrared gas exchange measurement,stable isotope method,etc.,Community evapotranspiration,ecological water consumption,community water budget and water use efficiency and other water use changes.The main findings are as follows:1.Under the condition of natural precipitation,the highest evapotranspiration rate of the community is 5.9 mm/d and the lowest one is 0.3 mm/d,with the averageevapotranspiration rate being 2.3 mm/d;the lowest evapotranspiration of 46.1 mm occurred in May and the highest evapotranspiration of 99.3 mm occurred in July.total evapotranspiration in the growing season is 339.8mm.The water balance in the growing season of this year was a surplus of 39.8 mm;The evapotranspiration water use efficiency of Stipa grandis community in the growing season is 0.56g·mm^-1.2.Simulated precipitation experiment,with the increase of precipitation,the community evapotranspiration increased significantly,water reduction treatment174.0mm<control 254.4mm<water increase treatment 337.4mm;community biomass increased significantly,respectively water reduction treatment 109.8g·m^-2<Control176.8g·m^-2<Water increase treatment 217.6g·m^-2;under different precipitation conditions,the utilization efficiency of community evapotranspiration is water reduction treatment 0.63g·mm^-1<water increase treatment 0.64g·mm^-1<Control0.69g·mm^-1,the difference between precipitation treatments is not significant.3.The surplus of the water balance of the Stipa grandis community simulated by the water increase treatment is 17.1mm;the deficit of the water balance of the control community is 1.2mm;the deficit of the water balance of the community of water reduction treatment is 29.9mm.4.With the increase of simulated precipitation,the leaf water potential difference of dominant species Stipa grandis and Leymus chinensis significantly decreased,and the water absorption capacity decreased significantly;the leaf stomatal conductance?Gs?increased significantly,and the leaf photosynthesis and transpiration rate of dominant species increased.;The?¹³C value of the leavesdecreased(?¹³C value of Stipa grandis leaves:water-reducing treatment-22.8‰>control-24.3‰>water-increasing treatment-24.4‰;?¹³C value of Leymus chinensis leaves:Water-reducing treatment-23.9‰>Control-24.2‰>water-increasing treatment-25.1‰),the water use efficiency of the dominant species decreases.