放牧对典型草原优势植物水分利用率的影响

发布时间：2018-03-21 21:13

本文选题：放牧梯度　切入点：典型草原　出处：《内蒙古大学》2016年硕士论文　论文类型：学位论文

【摘要】：水分是草原生态系统生产力的重要决定因子。放牧作为天然草原的一种主要利用方式,往往对草原生态系统的碳、水循环会产生一定的影响。深入揭示放牧对草原生态系统水分利用率(WUE)的影响,有助于从植物个体与群落水平水分代谢角度认识草原生态系统退化机制。本文以内蒙古典型草原为例,运用Li-6400便携式光合测定仪等仪器在叶片水平上测定和分析了不同放牧强度对大针茅和羊草光合特征、瞬时水分利用率和内在水分利用率的影响；在群落尺度上测定和分析了不同放牧强度对群落光合、呼吸及水分利用率的影响。主要研究结果如下：1.适度放牧提高了大针茅的净光合速率；对羊草叶片净光合速率影响不显著。从生长季早期到晚期,两种植物叶片净光合速率呈降低趋势。2.中、强度的放牧干扰提高了大针茅和羊草气孔导度和蒸腾速率；从生长季早期到晚期,两种植物叶片气孔导度和蒸腾速率呈降低趋势。3.随放牧强度增加大针茅瞬时水分利用率(WUEt)有升高趋势,而羊草表现为下降趋势；从生长季早期到晚期,两种植物WUEt也呈升高趋势。两种植物叶片内在水分利用率(WUEi)都随放牧强度增加而表现为下降的趋势,但在生长季各个月份无明显变化。4.从生长季早期到晚期,群落净生态系统碳交换量(NEE)、生态系统呼吸(ER)、总生态系统生产力(GEP)和生态系统蒸散(ET)都呈下降趋势；一定程度的放牧对群落NEE和GEP有促进作用,对ER有抑制作用。5.典型草原群落水分利用率(WUE)季节变化不明显,但适度放牧提高了群落的水分利用率。
[Abstract]:Water is an important determinant of grassland ecosystem productivity. Grazing, as a major use of natural steppe, often affects carbon in grassland ecosystems. The effect of grazing on water use efficiency of grassland ecosystem is revealed. It is helpful to understand the degradation mechanism of grassland ecosystem from the perspective of plant individual and community water metabolism. This paper takes the typical grassland of Inner Mongolia as an example. The effects of different grazing intensities on photosynthetic characteristics, instantaneous water use efficiency and internal water use efficiency of Stipa grandis and Leymus chinensis were measured and analyzed at leaf level by means of Li-6400 portable photosynthetic apparatus. The effects of different grazing intensities on photosynthesis, respiration and water use efficiency were measured and analyzed at community scale. The main results were as follows: 1. Moderate grazing increased net photosynthetic rate of Stipa grandis. There was no significant effect on the net photosynthetic rate of Leymus chinensis leaves. From the early to the late growing season, the net photosynthetic rate of the two plants showed a decreasing trend. 2. In the middle, the stomatal conductance and transpiration rate of Stipa grandis and Leymus chinensis were increased by grazing interference. From early to late growing season, the stomatal conductance and transpiration rate of the two plants showed a decreasing trend. 3. With the increase of grazing intensity, the instantaneous water use efficiency (WUET) of Stipa grandis increased, while Leymus chinensis showed a downward trend; from early to late growing season, The internal water use efficiency (Wue) of both plants showed a decreasing trend with the increase of grazing intensity, but there was no significant change in each month in the growing season. Net ecosystem carbon exchange (NEEN), ecosystem respiration, total ecosystem productivity (GEP) and ecosystem evapotranspiration (et) showed a decreasing trend, and grazing to a certain extent promoted community NEE and GEP. The seasonal variation of water use efficiency (WUE) of typical grassland community was not obvious, but moderate grazing increased the water use efficiency of the community.
【学位授予单位】：内蒙古大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：S812

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