【摘要】：人類活動(dòng)導(dǎo)致全球變暖和全球大氣環(huán)流發(fā)生改變,進(jìn)而改變?nèi)蚪邓窬帧８珊�、半干旱草原是全球分布最為廣泛的陸地生態(tài)系統(tǒng)類型,對(duì)降水變化最為敏感。而根系作為草原植物地下部分吸收水分的重要器官,對(duì)水分變化的響應(yīng)更為直接。因此,降水量的變化會(huì)改變植物根系的生長(zhǎng)、死亡和周轉(zhuǎn),進(jìn)而影響生態(tài)系統(tǒng)的碳循環(huán)過程。但由于根系是植物“藏著的一半”,以及根系研究方法的局限性,迄今,關(guān)于草原植物根系對(duì)降水量的響應(yīng)及其機(jī)制的研究尚少。本研究在中國(guó)科學(xué)院內(nèi)蒙古草原生態(tài)系統(tǒng)定位研究站進(jìn)行。依托該站完全控水遮雨棚大型實(shí)驗(yàn)平臺(tái),設(shè)計(jì)了以50mm為間隔的100~500mm的9個(gè)降水梯度處理,通過微根管法、土鉆法和內(nèi)生長(zhǎng)法的結(jié)合,深入探討了內(nèi)蒙古典型草原根系對(duì)降水變化的響應(yīng)。主要取得了以下結(jié)果:(1)降水量改變對(duì)土壤濕度和土壤溫度的影響:隨著降水量的增加,土壤水分含量線性增加,土壤溫度線性降低,且土壤水分含量和土壤溫度呈線性負(fù)相關(guān)關(guān)系。(2)降水量改變對(duì)根系的影響:隨著降水量的增加,根生物量、根生產(chǎn)量以及根系垂直分布均沒有發(fā)生顯著改變;而在降水量最大的降水處理下,根系壽命顯著減小,根系周轉(zhuǎn)加快。降水量增加促進(jìn)根系生長(zhǎng)和根系周轉(zhuǎn)加快加速根系死亡的共同作用導(dǎo)致根生產(chǎn)量和根生物量的變化不顯著。表層土壤(0-10cm)的土壤水分含量和土壤溫度分別與該土層的根生產(chǎn)量呈線性正相關(guān)和線性負(fù)相關(guān)關(guān)系,且土壤溫度對(duì)根生產(chǎn)量變化的解釋度高于土壤水分含量。(3)降水量改變對(duì)地上地下生物量分配的影響:內(nèi)蒙古典型草原生態(tài)系統(tǒng)的生物量在地上和地下器官間的分配服從最優(yōu)分配,隨著降水量的增加,根冠比顯著降低,說明對(duì)地上部分的投入增加。這主要緣于地上初級(jí)生產(chǎn)力和地下初級(jí)生產(chǎn)力對(duì)降水量變化的響應(yīng)不同。隨降水量的增加,ANPP顯著提高,且表現(xiàn)為非線性響應(yīng),即降水量較低時(shí),ANPP增加(單位降水量所生產(chǎn)的生物量)較快,降水量較高時(shí),ANPP增加變慢;但是,隨降水量增加,BNPP未發(fā)生顯著改變。綜上所述,本研究的降水梯度處理下內(nèi)蒙古典型草原根系生產(chǎn)沒有發(fā)生顯著改變,可能是由于降水量增加,根系周轉(zhuǎn)加快導(dǎo)致。生產(chǎn)力的地上和地下部分對(duì)降水變化的不同響應(yīng)使該生態(tài)系統(tǒng)的生物量分配不符合等速分配假說而符合最優(yōu)分配假說,即隨降水的增加,光合產(chǎn)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.
【學(xué)位授予單位】：江西師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：S812

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