【作者】 孙伟；

【导师】 王德利；

【作者基本信息】 东北师范大学 ， 草业科学， 2003， 硕士

【摘要】 温带的半干旱、半湿润区草甸草原属于过渡气候影响下形成的植被类型，对环境气候条件变化十分敏感，为了揭示半干旱、半湿润区草甸草原生态系统土壤碳素释放规律及其对主要环境因子的响应，本研究采用动态室红外气体吸收法测定松嫩草甸草原典型群落——贝加尔针茅群落土壤呼吸速率，分析了土壤呼吸速率日变化规律及表层土壤温度和含水量对土壤呼吸速率日变化的影响，比较了土壤呼吸速率的昼夜差异，探讨了地上生物量和地下生物量与土壤呼吸速率之间的相关关系。结果表明：（1）贝加尔针茅群落生长季土壤呼吸速率为1.05-5.86gC·m^-2d^-1，平均值为4.16±1.08gC·m^-2d^-1，土壤呼吸速率日变化呈明显单峰曲线，最大值一般出现在上午10-13时，最小值出现在凌晨3-5时；（2）土壤呼吸速率日变化与呼吸室内空气温度及大气温度的相关性大于土壤温度（10cm）；（3）呼吸室内水蒸气浓度可以表征温度与表层土壤含水量的互作效应，呼吸室内水蒸气浓度与土壤呼吸速率日变化存在较好的相关性；（4）昼夜土壤呼吸速率存在明显差异，随昼夜温差增大而增大，白天比夜晚平均大35.3％；（5）地上及地下生物量是土壤呼吸空间差异的主要影响因素。 CO₂浓度升高、光辐射强度变化和温度升高显著影响植物的光合及蒸腾生理生态特性，不同光合途径植物或同一光合途径下生理功能不同的植株对全球气候变化的响应存在明显差异，为了阐明C₃光合途径植物——贝加尔针茅及其不同生理功能类型植株对气候变化的响应，本实验设置了一系列CO₂浓度和光辐射强度变化，测量光合及蒸腾特性对CO₂浓度和光辐射强度变化的响应，同时测量并分析了气温日变化对光合及蒸腾生理特性的影响。结果如下：随着模拟CO₂浓度的升高，贝加尔针茅营养枝和生殖枝蒸腾速率均呈小幅增加趋势，营养枝蒸腾速率大于生殖枝，前者约为后者的1.77倍；两种植株叶片光合速率均随CO₂浓度的升高而呈显著增加趋势，二者光合速率对CO₂浓度升高的响应方程均为对数曲线，营养枝光合速率均值为生殖枝的1.72倍；贝加尔针茅两种不同功能类型植株水分利用效率均随CO₂浓度的升高而呈线性增加趋势，即大气COZ浓度升高能够显著提高C3光合途径植物的水分利用效率。生殖枝与营养枝光合速率均随模拟光辐射强度的增强而增大，营养校与生殖校分别在光辐射强度为1200－1400 u mol·m士s－‘及 1000－1200 u mol·m毛s1时达到光合速率的最大值，营养枝光合速率均值为生殖枝的1．35倍；二者蒸腾速率则随着模拟光辐射强度的增强而增大，营养枝蒸腾速率均值为生殖枝的1．29倍；模拟光辐射强度从 0增至 800 u mol·m－Zs”过程中，两种类型植株水分利用效率均呈骤增趋势，模拟光辐射强度超过 800 n mol·m”毛’‘后，水分利用效率增幅不大，甚至有所下降。由此可见，大气污染、烟雾和气溶胶导致的有效光辐射的减小对贝加尔针茅的光合积累影响较小，而水分利用效率则能有所提高。两种类型植株蒸腾速率日变化趋势基本一致，在9－10时达到最大值，随着气温和叶温的升高，气孔导度的降低，水分供应的减少，蒸腾速率逐渐减小。温度主要通过影响与光合作用相关酶活性及叶面饱和蒸气压亏缺而影响叶片的光合和蒸腾作用，无论是全球气候变化导致的极端温度变化还是平均温度升高，均会影响C3光合途径植物的分布范围。本研究认为，CO。浓度升高能够促进C3光合途径植物贝加尔针茅的初级生产，显著提高水分利用效率，增强其生存竞争能力。有效光辐射的减小不会降低贝加尔针茅的光合积累，在一定程度上提高了水分利用效率。植物分布区域的大小及其是否获得最终竞争优势受COZ浓度、温度、辐射强度、降水等环境条件综合作用影响，决非一种因素所能决定。更多还原

【Abstract】 Semi-arid meadow grassland was a vegetation form that developed under the transitional climate. As a typical community of semi-arid meadows grassland, the component species of Stipa baicalensis community are less than other communities in the same region. The community productivity, structure and succession are significantly influenced by global climate changes. This study focused on soil respiration rate of Stipa baicalensis grassland by using dynamic infrared gas absorbed method. We analyzed diurnal pattern of soil respiration rate and the influences of surface soil temperature and water content for this parameter, then compared the differences between day and night soil respiration rates, and explored the correlations between aboveground and underground biomass with the soil respiration. The major results were summarized as following: (a) The average soil respiration rate of Stipa baicalensis grassland was 4.16 1.08 gC-m-1d-1 during the growing season. The diurnal pattern of soil respiration rate had a single peak, the maximum value appeared at 10:00-13:00, and the minimum value appeared at 4:00-6:00; (b) The correlation between diurnal soil respiration rate variation and soil chamber air temperature was better than 10cm soil temperature; (c) The variatons in the chamber water vapor concentrations resulted from the interaction between the temperature and soil water content, so it had a significant correlation with the variation of soil respiration rate; (d) There were considerable significant differences between day and night soil respiration rates. For this study, the day soil respiration rates (averages of four months) were higher than the night soil respiration rates as 35.3%; (e) Above-ground biomass and under-groundbiomass were the main factors resulting to the variation in soil respiration on site.Plant photosynthesis and transpiration characteristics were more significantly influenced by CO2 enrichment, photosynthetic active radiation and climate warming. The variations of these ecological factors were the result of global climate changes. In order to explore the influence of ecological factors on plant physiological characteristics, we carried out a series of experiments on Stipa baicalensis community. With the increasing of CO2 concentrations, the transpiration rate of Stipa baicalensis, either for vegetative shoots or for reproductive shoots were significantly increasing. The average transpiration rates of vegetative shoots were 1.77 times sizes of reproductive shoots. The photosynthesis rates of both two types of shoots were obviously moving up with an increase of simulated CO2 concentrations. The average photosynthesis rate of vegetative shoots was 1.72 times sizes of reproductive shoots. Despite of differences in the physiological functions, the water use efficiency of vegetative and reproductive shoots had a linear increasing with the CO2 enrichment. So we draw a conclusion that CO2 enrichment can obviouely promote the water use efficiency of C3 plants. With intensifying of simulated photosynthetic radiation, the photosynthesis rates for all the shoots were increasing before radiation intensity reached 1200-1400 mol-m-2-s1 and 1000-1200 mol-m-2s-1 respectively for vegetative shoots and reproductive shoots. The average photosynthesis rate of vegetative shoots at all radiation gradients was 1.35 times sizes of reproductive shoots. The transpiration rates of shoots were increasing with the intensity of simulated photosynthetic radiation. As simulated photosynthetic radiation strengthened from 0 to 800 mol-m-2s-1, the water use efficiency of vegetative and reproductive shoots had a trend of suddenly increasing. With the constantly strengthen of simulated photosynthetic radiation, there had no significantly increasing of the water use efficiency, even a little bitdecreasing. We can draw another conclusion that the increasing of air pollution, smog and aerosol that result in reduce of photosynthetic active radiation would have no obvious influences on the photosynthetic accu更多还原