降水是影响水文过程的关键因素，为揭示羊草生理生态对降水变化的响应，以内蒙古锡林浩特与海拉尔地区的经过放牧和围封处理的典型羊草草原为研究对象，采用人工模拟降水实验，研究了不同生境管理方式差异下的羊草光合水分生理响应，及其降水和土壤水分的变化规律。结果表明:①不同大小降水事件土壤水分的维持时间不同，降水5 mm后60 h 土壤水分低于降水前水平，降水10～15 mm后60 h 土壤水分与降水前相同，降水20 mm后60 h是降水前的1。5倍。②典型草原羊草叶片净光合速率对降水的敏感性显著高于草甸草原，围封羊草叶片光合作用参数对降水的响应幅度高于放牧。羊草叶片气孔导度和蒸腾速率达到降水前水平，水分利用效率是降水5 mm和10 mm的近2倍。③羊草叶片的光合水分生理受土壤水分和温度的共同作用，其中典型草原与围封的土壤水分和土壤温度解释叶片净光合速率的31％～45％，草甸草原与放牧解释12％～17％。综上所述，降水处理后的羊草光合和生理特性产生了不同程度的影响，羊草叶片光合、蒸腾及水分利用效率提升的关键因素离不开土壤水分和土壤温度的增加或降低，为草地生态系统修复及管理提供重要的科学依据。
Effects of Simulated Precipitation on Photosynthetic Water Physiology of Leymus Chinensis
Precipitation is a key factor affecting hydrological processes.In order to reveal the physiological and ecological response of Leymus chingensis to changes in precipitation,this study took the typical Leymus chingen-sis prairie in Xilinhot and Hailaer areas of Inner Mongolia,which had been treated with grazing and enclosure,as the object of study,and used the artificial simulation of precipitation experiments to study the physiological re-sponse of photosynthesizing water of Leymus chingensis under the difference of different habitats'management modes and its change rules of precipitation and soil moisture.It was found that:①the maintenance time of soil moisture was different for different sizes of precipitation events.Soil moisture 60 h after 5 mm of precipitation was lower than the pre-precipitation level.60 h after 10～15 mm of precipitation was the same as the pre-precipi-tation level,and 60 h after 20 mm of precipitation was 1.5 times higher than the pre-precipitation level.②The sen-sitivity of net photosynthetic rate of typical grassland Leymus chingensis leaves to precipitation was significantly higher than that of meadow grassland,and the magnitude of response of photosynthesis parameters of fenced Ley-mus chingensis leaves to precipitation was higher than that of grazing.The stomatal conductance and transpiration rate of Leymus chingensis leaves reached the pre-precipitation level,and the water utilization efficiency was near-ly twice as high as that of precipitation of 5mm and 10mm.③The physiology of photosynthetic water in fescue leaves is influenced by a combination of soil moisture and temperature,with soil moisture and soil temperature explaining 31％to 45％of the net photosynthetic rate of foliage in typical prairie versus fenestration,and 12％to 17％in meadow grassland versus grazing.In summary,the photosynthetic and physiological characteristics of Leymus chinensis under precipitation treatment had different degrees of influence,and the key factors for the en-hancement of photosynthesis,transpiration and water utilization efficiency of Leymus chinensis leaves could not be separated from the increase or decrease of soil moisture and soil temperature,which provides an important sci-entific basis for the restoration and management of grassland ecosystems.
degeneration and non-degenerationLeymus chinensissoil moisturephotosynthetic water physiolo-gy
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