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气候变化背景下新疆干旱区农田生态系统碳动态模拟研究
吐热尼古丽·阿木提
学位类型博士
导师罗格平
2015
学位授予单位中国科学院大学
学位授予地点北京
学位专业地图学与地理信息系统
关键词干旱区 新疆 农田生态系统 气候变化 农田管理 碳动态 Agro-ibis
摘要随着全球变暖问题的日益突出,气候变化和人类活动对陆地生态系统碳循环的影响研究受到广泛的关注。 干旱区生态脆弱,对气候变化和人类活动非常敏感,尤其是干旱区绿洲农田生态系统,在绿洲不断扩张、农田集约管理不断加强和气候变暖加速背景下,干旱区农田生态系统碳库变得更为活跃,其碳动态对干旱区碳循环研究具有重要意义。由于干旱区绿洲农田生态系统碳循环研究方法的局限性以及获取研究所需数据的困难性,对亚洲中部干旱区绿洲农田生态系统碳动态及其对气候和农田管理活动响应的定量模拟与评估仍然缺乏。 本项研究以典型的全球动态植被模型 (Dynamic global vegetation models, DGVM) — 集成生物圈模型(the Integrated Biosphere Simulator,IBIS)的最新农业版本(Agro-IBIS)作为主要研究手段,从站点到区域尺度,通过数值模拟分析亚洲中部干旱区典型代表—新疆农田生态系统碳循环的动态及其时空格局特征,揭示新疆干旱区近30多年来农田生态系统碳动态过程及其对气候变化与农业集约管理的响应。首先,本项研究通过搜集和处理历史(1901-2009)逐月月平均格点气候观测数据(CRU)、30年(1961-1990)月平均气候异常数据集(CRU05)、NCEP/NCAR(1948-2009年)逐日气候再分析数据集(CFSR),以及土地利用与土地覆被、土壤、农田管理等数据建立了新疆干旱区气候、土壤、植被和农田管理综合数据集,满足Agro-IBIS模型对所需数据的要求;利用构建的数据集对Agro-IBIS模型进行了参数化和精度验证。最后,利用经过校验的Agro-IBIS模型,重建1979-2009年间新疆绿洲农田生态系统碳动态的时空格局;通过多情景数值模拟实验,分析了新疆农田生态系统碳动态与农田管理、气候变化和CO2浓度升高之间的关系,提出合理的干旱区绿洲农田利用及管理制度,促进农田生态系统的可持续发展。本项研究取得的主要结论包括: 1) 对乌兰乌苏农业气象站主要农作物冬小麦和春玉米生育期内的叶面积指数(LAI)、 地上生物量和净初级生产力(NPP)的模拟与校验表明, Agro-IBIS适用于模拟亚洲中部干旱区—新疆绿洲农田生态系统长期碳动态。 2) 1979-2009年新疆农田生态系统净碳交换量(NEE)年均值为 -63.36 g C m-2 yr-1,新疆农田总体上呈现明显的碳汇特征。30年来,农田生态系统NPP 平均为723.78 gC m-2year-1,并呈逐年增加的趋势,其总碳储量多年平均值为237.15 TgC,其中植被和土壤的碳储量分别约为19.5TgC和217.65TgC。1979-2009年新疆农田生态系统碳动态与气温的相关性较高,气温上升使新疆农田生态系统碳固定增加; 而与降水的相关性较弱。这说明农田生态系统植被NPP的年际变化与气温的关系更为密切。这主要是由于新疆为绿洲灌溉农业,农作物的生长主要依靠灌溉,自然降水对作物生长的影响总体有限很弱。但随着新疆绿洲30年出现降水增加温度上升的暖湿趋势,会促进农田生态系统生产力的提高。 3) 合理的施肥和灌溉措施将增加干旱区农作物NPP,尤其是在气象条件不变的情景下,农田生态系统净初级生产力随施肥施用量和灌溉水量的增加而增加,且与施肥与灌溉表现出较强的相关性。新疆农田平均施肥量在1979-2009年间增长了近7倍,作物单产产量也平均以78.22 kgC/ha/year的速度增长。而灌溉对农作物NPP的贡献程度约为78.37%,并干旱区农田对灌溉的依赖性要高于施肥。 4) 干旱区绿洲农田作物生长发育的人为影响远大于自然因素,干旱区绿洲农业是以灌溉农业为主,施肥等其它农田管理措施为辅。在气候波动情景下,Agro-IBIS模型模拟的农作物NPP总量都很低,春玉米NPP为166 ~ 502 g C m-2,冬小麦NPP为163 ~ 332 g C m-2,即在自然条件,该区域的主要农作物是无法正常生长发育的。同时,在气候波动+灌溉管理条件下,作物NPP值只提高了20%左右。在气候波动+灌溉在气候波动+灌溉+施肥管理措施情景下,其NPP出现显著增加,春玉米NPP达到753 ~ 1294 g C m-2,冬小麦NPP达到493~632 g C m-2,这说明气候波动+灌溉情景下的作物NPP显著高于气候波动+施肥情景下模拟的NPP。农作物的生产力NPP会随着大气CO2浓度的升高而增加,当CO2浓度由目前的水平380 ppm和升高到550 ppm时,新疆农田NPP平均从目前的的41.49 TgC year-1提高到47.13 TgC year-1。 5) 通过对不同施肥管理情景下碳动态的模拟分析,本项研究在理论上确定了240 kg/ha施肥水平,可以有效增加作物产量。氮肥施用过量不能提高作物产量反而可能会加快土壤氮素淋洗损失速度。灌溉是弥补该区域降水量不足影响作物生长发育的主要方式,在风雨年份,灌溉对于农作物NPP的影响较小,而枯水年份,灌溉的影响较大。对农田进行适应性管理,可以维持干旱区绿洲农田生态系统的稳定性和可持续性,并加强农田生态系统的碳汇作用。 本研究实现了Agro-IBIS模型在新疆绿洲农田的成功应用,突破了由于试验站点不足、作物类型多样而无法进行时空动态评估农田生态系统碳水循环的瓶颈。研究成果将为评估区域干旱区生态系统的碳收支时空格局及其生物地球化学机制、评价气候变化和农业管理对碳动态的影响、制定干旱区农田生态系统可持续发展策略、缓解和适应气候变化的区域碳管理规划和政策提供科学支撑。
其他摘要As global environmental problems have become increasingly prominent, the effects of climate change and human activities on the terrestrial carbon cycling have been widely concerned. The ecosystem of arid areas is very fragile, and sensitive to climate change and anthropogenic activities. Especially the agricultural ecosystem in the arid oasis has become more active under the oasis expansion, growing agricultural management activities and climate warming, therefore, its carbon dynamics is of great significance for carbon cycling study in the arid regions. However, there are still lack of studies on the quantitative modeling and evaluation of carbon dynamics of arid agricultural ecosystem on a regional scale and its response to climate and agricultural management activities. This is mainly due to the limitations of the research methods for spatio-temporal simulation of the agricultural ecosystem carbon cycle and the difficulty of obtaining the required data. This study comprehensively evaluated the carbon dynamics from single point to regional scale and its temporal-spatial characteristics as well as its response to climate change and agricultural management in the agricultural ecosystem of Xinjiang, a typical arid zone in the central Asia. A comprehensive ecosystem model (Agro-IBIS) adapted from the dynamic global vegetation model (DGVM) — the Integrated Biosphere Simulator (IBIS) was used for simulation and assessment of the carbon budget in the study area. For this research goal, the long-term (1901-2009) monthly mean observed climate dataset (CRU), 30-year (1961-1990) monthly mean climate anomaly dataset (CRU05) and (NCEP/NCAR) (1948-2009) daily reanalysis dataset(CFSR)were collected and processed to the required format for Agro-IBIS model. A spatial climate, soil and vegetation dataset was set up for the arid zone in Xinjiang. The Agro-IBIS model was calibrated and evaluated, and applied to temporally and spatially estimate the carbon dynamics of oasis agricultural ecosystem in Xinjiang. The relationships between the carbon dynamics and agricultural management, climate change as well as the CO2 concentration were analyzed through scenario modeling approach to put forward rational agricultural land use and management system for sustainable development of agricultural ecosystems. The main results are: (1) The Agro-IBIS model can be applied to simulate the carbon dynamics in the arid oasis agricultural ecosystems in Xinjiang according to the results from the model evaluation (crop LAI, Biomass and NPP) at Wulanwusu agricultural climate observation site. (2) The regional simulation results for the period of 1979-2009 shows that the agricultural ecosystems in Xinjiang acted as a net carbon sink, with a NEE mean value of -63.36 g C m-2 yr-1, and NPP value of 723.78 gC m-2year-1. The mean carbon stock in Xinjiang farmland over 33 years was about 237.15 TgC with the vegetation and soil carbon stock of 19.5TgC and 217.65TgC, respectively. There was stronger relationship between the carbon dynamics and the temperature; however, the weak relationship was found between the carbon dynamics and precipitation anomaly in the last 30 years. This indicates that there is closer relationship between agricultural ecosystem NPP and temperature. This is mainly due to irrigation agriculture dominated in Xinjiang, in which crop growth mainly relies on the irrigation, and overall effects of rainfall on it is very small. However, the trend of warmer and wetter climate in Xinjiang during the last 30 years accelerated the promotion of agricultural ecosystem NPP. (3) The appropriate fertilization and irrigation increase NPP of cropland in arid area, especially agricultural ecosystem NPP increases as increasing fertilization and irrigation amount under the non-changing climate condition. It was found that there was strong correlation between the agricultural ecosystem NPP and the fertilization as well as irrigation amount. During the period of 1979-2009, the amount of fertilization in Xinjiang cropland increased by near 7-times, and crop yield also increased at the rate of 78.22kg/ha year-1. The contribution of irrigation to NPP was about 78.37%, and the reliance of cropland of arid area on the irrigation was greater than that on the fertilization. (4) The human impact on the crop growth in the arid oasis was far greater than the impact of natural factors. The arid oasis agriculture was irrigation-based with assisted by other agricultural management such as fertilization. Total Crop NPP simulated by Agro-IBIS model under climatic vacillation was generally low, of which NPP for sprig maize was 166 ~ 502 g C m-2, and NPP for winter wheat was 163 ~ 332 g C m-2. It increased by about 20% with adding fertilization, while it increased significantly fertilization + irrigation, which was reached to 753 ~ 1294 g C m-2 for spring maize and 493~632 g C m-2 for winter wheat, respectively. This indicates that crop NPP simulated under climate with irrigation was significantly higher than that with fertilization. Crop NPP also increases under elevated CO2 concentration in the atmosphere. Total simulated NPP in Xinjiang cropland was 41.49 TgC year-1 under the current CO2 level (380ppm), and which reached up to 47.13 TgC year-1 when CO2 elevated to 550ppm. (5) This study estimated the ideal fertilization level by scenario modeling analysis with different fertilization amounts that can effectively promote the crop yield. Excessive fertilization is not able to increase crop yield, but is likely to accelerate the soil N leaching loss. Irrigation was the main method that can make up the part rainfall was not enough for crop growth in that area, where the effects of rainfall was lower during the wet years and higher during the dry years. Adaptive management for the cropland could help maintain the steady and sustainable development of agricultural ecosystem in the arid oases, as well as strengthen its ability to sequester carbon. This study implemented the application of Agro-IBIS model in Xinjiang oasis croplands, which made it possible to evaluate the carbon-water cycling of the agricultural ecosystem temporally and spatially despite the limited numbers of experimental sites and the varieties of crop types. The results obtained in this study could help assess the carbon budget spatially and temporally, as well as its biochemical mechanism in the arid areas. It could also help evaluate the effects of climate change and agricultural management on the carbon dynamics. Overall, it contributes to make sustainable development strategy for arid agricultural ecosystem and provide scientific support to make regional carbon management plan for climate adaptation and mitigation.
学科领域地图学与地理信息系统
语种中文
文献类型学位论文
条目标识符http://ir.xjlas.org/handle/365004/14607
专题研究系统_荒漠环境研究室
作者单位中科院新疆生态与地理研究所
推荐引用方式
GB/T 7714
吐热尼古丽·阿木提. 气候变化背景下新疆干旱区农田生态系统碳动态模拟研究[D]. 北京. 中国科学院大学,2015.
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