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模拟增温对青藏高原多年冻土区草地生态系统碳平衡的影响
Alternative TitleThe effect of experimental warming on the carbon balance of grassland ecosystems in the permaforst region of Qinghai-Tibet Plateau
Language中文
张涛
Thesis Advisor王根绪
2016
Degree Grantor中国科学院大学
Place of Conferral北京
Degree Name博士
Degree Discipline自然地理学
Keyword气候变化 Otc 冻原 物候 高寒草甸 土壤呼吸 碳库
Other Abstract

CO2等温室气体排放增加,加速了全球气候变暖趋势,而极地、高海拔及高纬度地区对气候变化响应更强烈。青藏高原作为地球“第三极”,平均海拔超过4000 m,区域面积占全国陆地面积比例达25%。青藏高原复杂的地形环境和高海拔,形成了该区独特的气候,使其对全球气候变化尤为敏感。过去45年间青藏高原多年冻土区气温增加明显,气候变暖加速青藏高原多年冻土融化,可能对全球变化产生重要的反馈作用。为揭示多年冻土区草地生态系统碳循环对气候变暖的响应机制,在青藏高原风火山多年冻土区选取典型高寒草甸和沼泽草甸两种具有代表性植被类型,采用OTCs模拟气温升高研究两种草甸生态系统植物物候、生物量、不同季节生态系统呼吸和总碳库等对气候变暖的响应机制,为完善冻土生态系统碳循环的动态平衡机制提供可靠的数据支持。 本研究采用不同高度OTCs模拟增温,高寒草甸年均气温分别比对照(NW)升高了2.08℃ (MW) 和4.91℃ (HW),沼泽草甸分别比对照(NW)升高了2.73℃ (MW) 和5.67℃ (HW)。 基于研究得到如下主要结果:1. 增温使两种草甸植物返青时间显著提前,MW使高寒草甸和沼泽草甸返青时间分别提前6.63天和5.03天,HW分别提前14.52天和12.58天。除沼泽草甸MW处理外,增温使两种草甸枯黄时间显著延后,其中MW使高寒草甸和沼泽草甸枯黄时间分别延后5.11天和1.80天,HW分别延后9.86天和3.34天。两种草甸生长季长度随增温幅度的增加而显著增加,不同增温幅度高寒草甸各物候期温度敏感性均高于沼泽草甸。植物返青时间、枯黄时间和生长季持续时间与年平均气温、土壤5 cm温度、冻土融化开始时间和融化持续时间显著相关(R2:0.47-0.89),而土壤水分对物候无显著影响。 2. 增温延长了两种草甸生长季长度,使地上生物量显著增加,其中高寒草甸较未增温处理增加175.20%(MW)和106.48%(HW), HW增幅显著低于MW,表明随着增温强度的增加,高寒草甸地上生物量响应强度降低。沼泽草甸地上生物量分别增加31.14%(MW)和46.16%(HW)。增温使高寒草甸地下生物量显著增加,而对沼泽草甸无显著影响,表明高寒草甸植物生产力对气候变暖响应更强烈。增温使两种草甸地下生物量向深层土壤转移。植物地上生物量与年均温、土壤5 cm温度、冻融融化持续时间和生长季长度均显著相关。增温对两种草甸植物和土壤全碳、全氮含量均无显著影响。 3. 生态系统呼吸呈明显的日变化和季节变化,高寒草甸日变异系数(0.30-0.92)高于沼泽草甸(0.12-0.29),季节变化与5 cm地温变化一致。两种草甸生态系统呼吸与气温、5 cm和20 cm地温均显著相关。MW使高寒草甸和沼泽草甸生态系统呼吸分别增加62.2%和36.6%;HW使高寒草甸和沼泽草甸生态系统呼吸分别增加101.3%和52.0% 。增温对两种草甸类型的影响存在季节性差异,非生长季增幅高于生长季增幅,致使非生长季生态系统呼吸占全年比例从对照的25%增加到HW的31%(P<0.05)。生态系统呼吸受土壤温度、地上生物量和冻土融化持续时间等因子显著影响。非生长季Q10(3.02-5.02)高于生长季Q10(2.11-2.75),且Q10随温度的增加而降低。 4. 冻融前期土壤呼吸(0.38-0.54 μmol m-2 s-1)显著高于冬季(0.11-0.23 μmol m-2 s-1),且沼泽草甸显著高于高寒草甸,整个非生长季土壤呼吸占到全年四分之一。土壤温度可以解释土壤呼吸76%-85%的季节变异。冻融前期土壤呼吸Q10(5.67-9.43)高于其他季节(2.65-2.99)。通过分季节、全年和生长季指数方程模拟发现分季节模拟土壤呼吸值与实测值间相关性最高,表明分季节指数方程能够相对准确的估算土壤呼吸年碳排放。沼泽草甸自养呼吸和异养呼吸均高于高寒草甸,分别高45.45%和48.33%。两种草甸类型自养呼吸占土壤呼吸比例(Ra/Rs)波动较大,但总体上生长季高于冻融前期。整个观测期高寒草甸和沼泽草甸平均Ra/Rs分别为36.91%和34.91%。Q10值为自养呼吸(4.91-5.17)>土壤呼吸(3.99-5.01)>异养呼吸(3.42-4.88)。5.增温显著增加高寒草甸植物总碳库,增温使植物碳库向地上和深层土壤转移。增温使沼泽草甸植物地上碳库显著增加,但对植物总碳库无显著影响;除高寒草甸HW外,增温降低了两种草甸土壤碳库,其降幅高于植被总碳库增加幅度。MW使两种草甸生态系统总碳库降低,而HM使高寒草甸生态系统总碳库增加,使沼泽草甸生态系统总碳库降低。表明长期增温(6年)对青藏高原多年冻土区草地生态系统总碳库的影响可能因草甸类型和增温幅度而异,但变化不显著。 

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The global air temperature has been experiencing a rapid increase due to the greenhouse gas emission, such as CO2; moreover, the polar and high altitude regions are experiencing a more rapid increase than the global average. As the third polar in the world, the Qinghai-Tibet Plateau (QTP) has a unique environment because of the high altitude and complex topography, which is very sensitive to climate change. The temperature has been increased during the last 45 years in the permafrost region of QTP. Climate warming could accelerate the permafrost thaw, creating a positive feedback to global warming. To understand the warming effect on ecosystem C cycle, we conducted a full year measurements of plant phenology, biomass, carbon pool and ecosystem respiration under experimental warming conditions by using OTCs in alpine meadow and swamp meadow in the permafrost region of Fenghuo mountain on the QTP.The warming treatment was achieved by different hight of OTCs. A moderate warming level (MW) increased the air temperature by 2.09 and 2.73°C, and a high warming level (HW) increased the air temperature by 4.91 and 5.67°C in alpine meadow and swamp meadow, respectively. The main results were as follows:1. The start of growing season (SOS) was significantly advanced by warming in both meadows; MW increased the SOS by 6.63 and 5.03 days and HW increased the SOS by 14.52 and 12.58 days in alpine meadow and swamp meadow, respectively. Warming significantly delayed the end of growing season (EOS) except MW in swamp meadow. MW increased the EOS by 5.11 and 1.08 days and HW increased the EOS by 9.86 and 3.34 days in alpine meadow and swamp meadow, respectively. The duration of growing season (DOS) increased with the warming levels, and the sensitivity of phenology in alpine meadow was higher than that in swamp meadow. The SOS, EOS and DOS were significantly correlated with mean annual air temperature, soil temperature at 5 cm, the start of thawing day and duration of thaw days (R2:0.47-0.89). 2. Warming significantly increased the aboveground biomass in both meadows, which increased the aboveground biomass by 175.20% (MW) and 106.48% (HW) in alpine meadow and 31.14% (MW) and 46.16% (HW) in swamp meadow. The magnitude of the aboveground biomass increase in HW was lower than that in MW, indicating that the sensitivity of the aboveground biomass to warming decreased with temperature increase. Warming significantly increased the belowground biomass in alpine meadow but no difference in swamp meadow, indicating that the sensitivity of plant biomass to warming was higher in alpine meadow compared with swamp meadow. Moreover, warming accelerated the transfer of the belowground biomass to deep soil. The aboveground biomass was significantly correlated with mean annual air temperature, soil temperature at 5 cm, duration of thaw days and duration of growing season. There was on difference of total plant and soil C and N between no warming treatment and warming treatment in both meadows.3. We found that the diurnal and seasonal ER were dynamic with large changes in both meadows, the variable coefficient of diurnal changes in alpine meadow (0.30-0.92) was higher compared with swamp meadow (0.12-0.29), the seasonal variations of ER were dynamic with soil temperature at 5 cm. MW increased the ER by 62.2% and 36.6% and HW increased the ER by 101.3% and 52.0% in alpine meadow and swamp meadow, respectively. The warming effect on ER was greater in the non-growing season compared with growing season, which increased the contribution of non-growing season emission to annual emission from 25% in natural condition to 31% in high warming treatments (P<0.05). ER was significantly affected by soil temperature, aboveground biomass and the duration of thaw days. The Q10 was higher in non-growing season (3.02-5.02) than growing season (2.11-2.75) and decreased with temperature increase.4. Mean soil respiration was higher in initial thaw and freeze period (0.38-0.54 μmol m-2 s-1) than in winter (0.11-0.23 μmol m-2 s-1), and with significant higher in swamp meadow than alpine meadow in the non-growing season. Soil temperature explained 76%-85% of the seasonal variation in the soil respiration, with higher temperature sensitivity (Q10) in the initial thaw-freeze period (5.67-9.43) compared with other seasons (2.65-2.99). The modeled soil respiration based on season-specific Q10 was closer to the measured values than annual and growing season Q10 model, indicated that season-specific model may improve the accuracy of estimating the annual soil respiration. The autotrophic and heterotrophic respiration was 45.45% and 48.33% higher in alpine meadow than swamp meadow. The ratio of autotrophic respiration to total soil respiration showed a large seasonal variation with higher ratio in growing season compared with the initial thaw and freeze period. The mean ratio of autotrophic respiration to total soil respiration was 36.91% and 34.91% in alpine meadow and swamp meadow, respectively. The Q10 of autotrophic, heterotrophic and soil respiration was 4.91-5.17, 3.42-4.88 and 3.99-5.01, respectively.5. Warming significantly increased the total plant carbon pool in alpine meadow; Warming accelerated the transfer of the plant carbon pool to deep soil and aboveground. Warming significantly increased the aboveground plant carbon pool but no effect on belowground plant carbon pool in swamp meadow. On the other hand, warming decreased the total soil carbon pool except HW in alpine meadow. In general,MW increased the ecosystem carbon pool in both meadows, while HM increased the ecosystem carbon pool in alpine meadow but decreased in swamp meadow. Our results indicated that long term warming (6 years) effect on alpine meadow ecosystem carbon pool may depend on vegetation types and warming levels in the permafrost region of QTP, but the changes were not significant. 

Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/18974
Collection山地表生过程与生态调控重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
张涛. 模拟增温对青藏高原多年冻土区草地生态系统碳平衡的影响[D]. 北京. 中国科学院大学,2016.
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