【作者】 韩芳；

【导师】 牛建明；

【作者基本信息】 内蒙古大学 ， 生态学， 2013， 博士

【摘要】 气候变化是当今国际社会普遍关注的全球性重大问题,严重威胁自然生态系统和社会经济系统,特别是对环境脆弱地区的影响更加显著。内蒙古中温型荒漠草原植被低矮、稀疏,群落生产力低,气候干旱,自然环境复杂,成为气候变化的异常敏感区域。因此,在全球气候变化的背景下,探讨内蒙古荒漠草原生态系统对气候变化的响应具有重要的理论和实践意义。本项研究以内蒙古中温型荒漠草原为对象,利用1961～2010年荒漠草原区11个气象站资料,分析了气温、降水和干燥度的时空分布格局以及变化趋势；利用2004～2012年荒漠草原区6个生态观测站的植物返青期和黄枯期资料,分析了植物物候变化特征,探讨了气候因子对植物物候的影响；利用2008年和2009年野外考察点146个样方数据,分析了气候因子对物种多样性分布格局的影响；利用1982～2009年NOAA/AVHRR NDVI资料及气候数据驱动EC-LUE模型,对内蒙古荒漠草原GPP进行模拟,分析其时空变化特征,并探讨了气候因子对GPP的影响；采用Thornthwaite Memorial模型模拟荒漠草原气候生产力,探讨未来气候变化情景下,内蒙古荒漠草原气候生产力的变化趋势。得出的主要结论如下：(1)内蒙古荒漠草原气温呈现出非对称变化特征。年平均、年平均最高和年平均最低气温均呈增温趋势,分别为0.47、0.33、0.60℃/10a。气温的增加以最低气温的升温为主导。季节上,四季均为增温趋势,以冬季增温最为明显。(2)内蒙古荒漠草原年降水量自东南向西北呈条带状逐渐减少。近50a来年降水量表现为波动变化、略下降的趋势,近10a来的下降尤为突出。在空间上,与典型草原毗邻地区和中部偏西地区的年降水量明显增加,东北部地区明显减少。在季节上,春季降水量增加,夏季降水量减少。(3)年平均干燥度呈条带状自东南向西北逐渐递增。内蒙古荒漠草原干旱化趋势加重,大部分地区的干燥度指数呈增加趋势,干燥度指数越高的地方,干燥度增加趋势越明显。近10a来,研究区域的干旱化趋势最为剧烈。(4)内蒙古荒漠草原植物返青期和黄枯期均提前,生长季天数缩短。植物返青期与2月平均温度存在显著的负相关关系,4月的降水量对返青起主要作用,可见内蒙古荒漠草原春季升温、降水量增加导致了植物返青期提前。(5)内蒙古荒漠草原群落物种丰富度主要随经度的增加而增加,与该区降水的空间分布格局一致。物种丰富度与潜在蒸散量呈现负线性相关。降水量对一二年生草本、多年生杂类草和多年生根茎禾草功能群物种丰富度分布格局起主导作用,一二年生草本功能群物种丰富度随降水增多而下降,多年生杂类草和多年生根茎禾草功能群物种丰富度均随降水增多而升高。(6)内蒙古荒漠草原GPP呈现南高北低、东多西少的分布格局,与干燥度的空间分布格局具有较高的一致性。从区域上看,东南部减少,西北部增加；从时间上看,1982年以来,内蒙古荒漠草原GPP表现减少的变化趋势,近10a来下降明显,与气候的变化特征一致。年降水量、生长季降水量、夏季降水量均与GPP呈显著正相关,表明降水因素是制约内蒙古荒漠草原植被生产力的关键因子。(7)气候变化对气候生产潜力影响显著。“暖湿型”和“冷湿型”气候可使荒漠草原气候生产力提高,而“暖干型”气候使气候生产力降低,表明内蒙古荒漠草原植被生长受温度的影响较小,降水的作用较大,进一步证实降水是制约内蒙古荒漠草原植被生长的关键因子。(8)根据相关研究与预测,内蒙古荒漠草原未来气候向暖干化趋势发展,因此,内蒙古荒漠草原的植被生产力将呈现出降低的变化趋势。伴随着内蒙古荒漠草原的气候变化,地处干旱、半干旱区的内蒙古荒漠草原植物物候期提前,生长季缩短,植被生产力减少,给当地的农牧民生产生活带来重大社会经济影响,应引起各级政府的高度重视,尽快提出应对气候变化的政策和措施。更多还原

【Abstract】 Today, climate change is of widespread concern in the international community as a major global issue, and seriously threatens natural ecosystems and socioeconomic systems. The impact on environmentally fragile areas is especially significant. In the Inner Mongolia medium temperate desert steppe, vegetation is low and sparse, community productivity low, the climate arid, and the natural environment complex. This makes the area extremely sensitive to climate change. Therefore under global climate change, the study of the response to climate change of the Inner Mongolia desert steppe ecosystem has important theoretical and practical significance.Given this steppe as the study area, we used data from11meteorological stations from1961to2010to investigate spatiotemporal distribution patterns and trends of temperature, precipitation and aridity index. We also used turning-green and withering period data from6ecological stations over2004-2012on the steppe, to analyze variations of plant phenology and the impact of climatic factors on that phenology. Using146-quadrat field data from2008and2009, we studied climate factor influences on the distribution of species diversity. NOAA/AVHRR NDVI data from1982to2009and a climate data-driven Eddy Covariance-Light Use Efficiency (EC-LUE) model were used to simulate Gross Primary Production (GPP) on the desert steppe, to analyze spatiotemporal variations and investigate the influence of climatic factors on GPP. Using Thornthwaite Memorial model simulations of climate productivity on the desert steppe, we examined future climate-change scenario productivity trends.Temperature on the Inner Mongolia desert steppe showed asymmetric variations. Annual average temperature and annual mean maximum and minimum temperatures all showed warming trends, of0.47,0.33and0.60℃/10a, respectively. The minimum temperature increased most significantly. Temperature in the four seasons had warming trends, with the greatest warming in winter.Annual precipitation showed a banded pattern, gradually declining from southeast to northwest on the steppe. In the last50years, precipitation fluctuated but with a slight downward trend, especially in the last decade. Spatially, annual precipitation significantly increased in an adjoining area of typical steppe and the west-central region, and significantly decreased in the northeast. Temporally, precipitation increased in spring and decreased in summer.The annual average aridity index showed a banded progressive increase from southeast to northwest. There was a tendency toward increased aridity on the desert steppe, with a higher aridity index and a clear increasing trend. The drought trend in the study area was most severe in the last decade. Warming was main factor causing the aridity index increase.Turning-green and withering periods of the steppe grassland vegetation were early, and the number of growing-season days were shortened. There was significant negative correlation between the turning-green period and average temperature in February, and April rainfall was important for turning green. Temperature rise and rainfall increase in spring resulted in an early turning green of vegetation.Species richness increased with longitude, consistent with the spatial distribution of precipitation. There was negative correlation between species richness and potential evapotranspiration. Precipitation had a strong influence on species richness distributions for biennial herbaceous, perennial forb, and perennial rhizomatous grass functional groups. With precipitation increase, biennial herbaceous species richness decreased, but that of perennial forbs and rhizomatous grasses increased.The GPP distribution was high in the south and low in the north, plus high in the east and low in the west. The distribution of aridity index had greater consistency than GPP. From a regional point of view, the GPP of the southeast decreased and increased in the northwest. From the time point of view, Since1982, GPP on the steppe has had a declining trend, especially in the last decade, consistent with the characteristics of climate change. GPP decreased in the southeast part of the region, and increased in the northwest. Annual, growing-season and summer precipitation all had significant positive correlations with GPP, indicating that precipitation was a key constraint on GPP.Climate change significantly affected climate potential production."Warm-wet" and "cold-wet" climates increased climate potential production, but this production was reduced by a "warm-dry" climate. This indicates that vegetation growth was less affected by temperature than by precipitation. Precipitation was a key limitation of vegetation growth.According to correlation analyses and forecasts, climate of the Inner Mongolia desert steppe will be warmer and drier in the future. Therefore, GPP will decrease.With climate change, plant phenology became earlier, the growing season shortened, and vegetation productivity declined. This significantly impacted the local economy and the production and living conditions of farmers and herdsmen. This should be urgently addressed by the government, which should formulate policies and measures to combat climate change as quickly as possible.更多还原