内蒙古典型草原根系对降水量变化的响应

发布时间：2018-09-12 12:00

【摘要】：人类活动导致全球变暖和全球大气环流发生改变,进而改变全球降水格局。干旱、半干旱草原是全球分布最为广泛的陆地生态系统类型,对降水变化最为敏感。而根系作为草原植物地下部分吸收水分的重要器官,对水分变化的响应更为直接。因此,降水量的变化会改变植物根系的生长、死亡和周转,进而影响生态系统的碳循环过程。但由于根系是植物“藏着的一半”,以及根系研究方法的局限性,迄今,关于草原植物根系对降水量的响应及其机制的研究尚少。本研究在中国科学院内蒙古草原生态系统定位研究站进行。依托该站完全控水遮雨棚大型实验平台,设计了以50mm为间隔的100~500mm的9个降水梯度处理,通过微根管法、土钻法和内生长法的结合,深入探讨了内蒙古典型草原根系对降水变化的响应。主要取得了以下结果:(1)降水量改变对土壤湿度和土壤温度的影响:随着降水量的增加,土壤水分含量线性增加,土壤温度线性降低,且土壤水分含量和土壤温度呈线性负相关关系。(2)降水量改变对根系的影响:随着降水量的增加,根生物量、根生产量以及根系垂直分布均没有发生显著改变;而在降水量最大的降水处理下,根系寿命显著减小,根系周转加快。降水量增加促进根系生长和根系周转加快加速根系死亡的共同作用导致根生产量和根生物量的变化不显著。表层土壤(0-10cm)的土壤水分含量和土壤温度分别与该土层的根生产量呈线性正相关和线性负相关关系,且土壤温度对根生产量变化的解释度高于土壤水分含量。(3)降水量改变对地上地下生物量分配的影响:内蒙古典型草原生态系统的生物量在地上和地下器官间的分配服从最优分配,随着降水量的增加,根冠比显著降低,说明对地上部分的投入增加。这主要缘于地上初级生产力和地下初级生产力对降水量变化的响应不同。随降水量的增加,ANPP显著提高,且表现为非线性响应,即降水量较低时,ANPP增加(单位降水量所生产的生物量)较快,降水量较高时,ANPP增加变慢;但是,随降水量增加,BNPP未发生显著改变。综上所述,本研究的降水梯度处理下内蒙古典型草原根系生产没有发生显著改变,可能是由于降水量增加,根系周转加快导致。生产力的地上和地下部分对降水变化的不同响应使该生态系统的生物量分配不符合等速分配假说而符合最优分配假说,即随降水的增加,光合产物更多地被分配到地上部分。
[Abstract]:Human activities cause global warming and global atmospheric circulation change, and then change the global precipitation pattern. Arid and semiarid steppe are the most widely distributed terrestrial ecosystems and are most sensitive to precipitation changes. As an important part of steppe plants to absorb water, root system is more direct to water change. Therefore, the change of precipitation will change the growth, death and turnover of plant roots, and then affect the carbon cycle of the ecosystem. However, due to the fact that the root system is the "half hidden" of the plant, and because of the limitation of the research method of the root system, so far, there are few studies on the response of the root system of the grassland plant to precipitation and its mechanism. This study was carried out at Inner Mongolia grassland ecosystem Positioning Station, Chinese Academy of Sciences. Based on the large scale experimental platform of complete water control and rain shelter in this station, nine precipitation gradient treatments of 100~500mm with 50mm interval are designed. Through the combination of micro root canal method, soil drilling method and inner growth method, The response of typical grassland roots to precipitation in Inner Mongolia was discussed. The main results are as follows: (1) the effect of the change of precipitation on soil moisture and soil temperature: with the increase of precipitation, the content of soil moisture increases linearly, and the soil temperature decreases linearly. There was a linear negative correlation between soil moisture content and soil temperature. (2) the effect of precipitation change on root system: with the increase of precipitation, root biomass, root production and root vertical distribution did not change significantly. However, under the precipitation treatment with the largest precipitation amount, the root life decreased significantly and the root turnover increased. The effects of increasing precipitation on root growth and root turnover and accelerating root death resulted in no significant changes in root production and root biomass. Soil moisture content and soil temperature in surface soil (0-10cm) were positively and linearly negatively correlated with root production, respectively. And the explanation of soil temperature to root production change is higher than that of soil moisture content. (3) the effect of precipitation change on aboveground and underground biomass allocation: the distribution of biomass between aboveground and underground organs of typical grassland ecosystem in Inner Mongolia From the optimal distribution, With the increase of precipitation, the ratio of root to shoot decreased significantly, indicating that the input to the aboveground part increased. This is mainly due to the different responses of above-ground primary productivity and underground primary productivity to precipitation changes. With the increase of precipitation, ANPP increased significantly, and showed nonlinear response, that is, ANPP increased faster (biomass per unit precipitation) and increased slowly when precipitation was lower, but the increase of ANPP decreased with the increase of precipitation. With the increase of precipitation, BNPP did not change significantly. To sum up, the root production of typical grassland in Inner Mongolia did not change significantly under precipitation gradient treatment, which may be due to the increase of precipitation and the acceleration of root turnover. The different responses of the aboveground and underground parts of productivity to precipitation change make the biomass allocation of the ecosystem not in accordance with the hypothesis of isokinetic allocation but with the hypothesis of optimal allocation, that is, with the increase of precipitation, the photosynthetic products are distributed more to the aboveground part.
【学位授予单位】：江西师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S812

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