不同放牧條件下錫林郭勒草原凍融作用對土壤水熱及溫室氣體排放的影響
發(fā)布時間：2018-11-21 09:28
【摘要】：我國作為世界第三凍土大國,多年和季節(jié)性凍土面積占陸地面積的75%,主要分布在青藏高原和內(nèi)蒙古高原等氣候變化敏感區(qū)。冰雪覆蓋、土壤凍結(jié)及其消融過程,會顯著改變土-氣界面水熱交換和平衡特征。尤其是近年來全球變暖引起冰凍區(qū)消退加速,以及人類活動對自然環(huán)境的影響日益加深,有關(guān)凍土水文效應(yīng)及其溫室氣體排放的評價越來越得到重視。本研究依托中國科學(xué)院內(nèi)蒙古草原生態(tài)系統(tǒng)定位研究站,選取區(qū)域內(nèi)具有不同圍牧年限以及放牧條件下的三種土地利用方式(UG79(1979年以來禁牧)、UG99(1999年以來禁牧)、HG(1979年以來持續(xù)放牧))作為研究對象。依據(jù)測定結(jié)果探討不同放牧條件下凍融交替對土壤水分、溫度以及土壤溫室氣體排放的影響,為準(zhǔn)確評估變化環(huán)境下(全球變化和土地利用變化)內(nèi)蒙古季節(jié)性凍土區(qū)土壤凍融的水文效應(yīng)以及N_2O排放提供更準(zhǔn)確的科學(xué)依據(jù)。本試驗研究結(jié)果表明:1、一定厚度的積雪可以有效隔絕氣溫的影響,從而降低土壤溫度下降幅度。HG處理積雪厚度遠(yuǎn)小于其它處理,其土壤溫度變化最劇烈,土壤凍結(jié)和融化速率最快。淺層土壤(0~30 cm)UG79和UG99處理土壤溫度明顯高于HG處理,而在深層100 cm深度處三種放牧條件下土壤的溫度變化趨勢基本一致,放牧對深層土壤溫度的影響有限。2、土壤凍結(jié)期,UG99“聚墑區(qū)”分布范圍最廣,且集中在牧草根系發(fā)達(dá)區(qū)域,對牧草根系層的儲水保墑效果最佳。土壤消融期,土壤液態(tài)含水量高于凍融前,表層土壤UG99液態(tài)含水量增加幅度大于UG79和HG處理,其最大值達(dá)到了0.19 m3/m3,“凍后聚墑”效應(yīng)最為明顯,為春季植被的生長發(fā)育提供了良好的水分環(huán)境。3、錫林郭勒草原CO_2排放通量主要集中在生長季和非生長季的解凍期。盡管解凍期對于全年CO_2排放量的貢獻(xiàn)很低,但其CO_2累積釋放量占非生長季排放量的50%以上,在年際尺度上對CO_2的排放起促進(jìn)作用。CO_2排放通量與土壤溫度表現(xiàn)出極顯著正相關(guān)關(guān)系,但與土壤含水量無顯著相關(guān)關(guān)系。4、在土壤凍結(jié)期(11月~2月),不同處理部分土層表現(xiàn)為弱“匯”,而土壤解凍期N_2O存在脈沖式集中釋放,在全年排放總量中有著舉足輕重的作用。土壤溫度及含水量對N_2O影響相對復(fù)雜,研究區(qū)N_2O排放與土壤溫度水分無顯著的相關(guān)性。非生長季和凍融期HG處理N_2O累積排放通量高于UG79、UG99處理,其原因可能與研究樣地以及放牧年限有關(guān)。
[Abstract]:As the third largest permafrost country in the world, China accounts for 75% of the land area for many years and seasonal permafrost, mainly distributed in the sensitive areas of climate change such as the Qinghai-Tibet Plateau and the Inner Mongolia Plateau. Ice and snow cover, soil freezing and melting process will significantly change the characteristics of soil-gas interface hydrothermal exchange and balance. Especially in recent years, global warming has accelerated the retreat of frozen regions, and the impact of human activities on the natural environment has become more and more serious. More and more attention has been paid to the evaluation of hydrological effects of frozen soils and their greenhouse gas emissions. Based on Inner Mongolia grassland ecosystem location Research Station of the Chinese Academy of Sciences, this study selected three land use patterns (UG79 (no grazing since 1979) and UG99 (no grazing since 1999) in the region with different grazing years and grazing conditions. HG (continuous grazing since 1979) was used as the research object. The effects of freeze-thaw alternation on soil moisture, temperature and greenhouse gas emissions under different grazing conditions were studied. It provides a more accurate scientific basis for accurately evaluating the hydrological effects of soil freezing and thawing and N2O emission in seasonal frozen soil regions of Inner Mongolia under changing environment (global change and land use change). The results of this experiment show that: 1. The snow cover with a certain thickness can effectively insulate the effect of temperature, thus reducing the decrease of soil temperature. The thickness of snow in HG treatment is much smaller than that in other treatments, and the change of soil temperature is the most severe. The freezing and melting rate of soil is the fastest. The temperature of shallow soil (0 ~ 30 cm) treated with UG79 and UG99 was significantly higher than that of HG treatment, but the variation trend of soil temperature at the depth of 100 cm was basically the same, and the effect of grazing on the temperature of deep soil was limited. 2. During the period of soil freezing, UG99 was the most widely distributed area and concentrated in the developed area of forage root system, which had the best effect on water storage and moisture conservation of forage root layer. During the period of soil ablation, the water content of liquid soil was higher than that before freezing and thawing, and the increase of liquid water content of UG99 in surface soil was larger than that of UG79 and HG, and the maximum value was 0.19 m3 / m3, and the effect of "accumulating moisture after freezing" was the most obvious. It provides a good water environment for the growth and development of vegetation in spring. 3. The CO_2 emission flux of Xilinguole grassland is mainly concentrated in the thawing period of growing season and non-growing season. Although the thawing period contributed very little to the annual CO_2 emissions, the cumulative release of CO_2 accounted for more than 50% of the non-growth season emissions. CO_2 emission flux was positively correlated with soil temperature, but had no significant correlation with soil moisture content. 4. During the period of soil freezing (November to February), the emission flux of CO_2 was positively correlated with soil temperature. Some soil layers of different treatments showed weak "sink", while the pulse concentrated release of N _ 2O existed in the thawing period of soil, which played an important role in the total emission of the whole year. The effect of soil temperature and water content on N2O is relatively complex. There is no significant correlation between N2O emission and soil temperature and moisture in the study area. The cumulative emission flux of N2O in HG treatment in non-growth season and freeze-thaw period was higher than that in UG79,UG99 treatment, which may be related to the study land and grazing years.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：S812
本文編號：2346563
[Abstract]:As the third largest permafrost country in the world, China accounts for 75% of the land area for many years and seasonal permafrost, mainly distributed in the sensitive areas of climate change such as the Qinghai-Tibet Plateau and the Inner Mongolia Plateau. Ice and snow cover, soil freezing and melting process will significantly change the characteristics of soil-gas interface hydrothermal exchange and balance. Especially in recent years, global warming has accelerated the retreat of frozen regions, and the impact of human activities on the natural environment has become more and more serious. More and more attention has been paid to the evaluation of hydrological effects of frozen soils and their greenhouse gas emissions. Based on Inner Mongolia grassland ecosystem location Research Station of the Chinese Academy of Sciences, this study selected three land use patterns (UG79 (no grazing since 1979) and UG99 (no grazing since 1999) in the region with different grazing years and grazing conditions. HG (continuous grazing since 1979) was used as the research object. The effects of freeze-thaw alternation on soil moisture, temperature and greenhouse gas emissions under different grazing conditions were studied. It provides a more accurate scientific basis for accurately evaluating the hydrological effects of soil freezing and thawing and N2O emission in seasonal frozen soil regions of Inner Mongolia under changing environment (global change and land use change). The results of this experiment show that: 1. The snow cover with a certain thickness can effectively insulate the effect of temperature, thus reducing the decrease of soil temperature. The thickness of snow in HG treatment is much smaller than that in other treatments, and the change of soil temperature is the most severe. The freezing and melting rate of soil is the fastest. The temperature of shallow soil (0 ~ 30 cm) treated with UG79 and UG99 was significantly higher than that of HG treatment, but the variation trend of soil temperature at the depth of 100 cm was basically the same, and the effect of grazing on the temperature of deep soil was limited. 2. During the period of soil freezing, UG99 was the most widely distributed area and concentrated in the developed area of forage root system, which had the best effect on water storage and moisture conservation of forage root layer. During the period of soil ablation, the water content of liquid soil was higher than that before freezing and thawing, and the increase of liquid water content of UG99 in surface soil was larger than that of UG79 and HG, and the maximum value was 0.19 m3 / m3, and the effect of "accumulating moisture after freezing" was the most obvious. It provides a good water environment for the growth and development of vegetation in spring. 3. The CO_2 emission flux of Xilinguole grassland is mainly concentrated in the thawing period of growing season and non-growing season. Although the thawing period contributed very little to the annual CO_2 emissions, the cumulative release of CO_2 accounted for more than 50% of the non-growth season emissions. CO_2 emission flux was positively correlated with soil temperature, but had no significant correlation with soil moisture content. 4. During the period of soil freezing (November to February), the emission flux of CO_2 was positively correlated with soil temperature. Some soil layers of different treatments showed weak "sink", while the pulse concentrated release of N _ 2O existed in the thawing period of soil, which played an important role in the total emission of the whole year. The effect of soil temperature and water content on N2O is relatively complex. There is no significant correlation between N2O emission and soil temperature and moisture in the study area. The cumulative emission flux of N2O in HG treatment in non-growth season and freeze-thaw period was higher than that in UG79,UG99 treatment, which may be related to the study land and grazing years.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：S812
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