【作者】 叶建圣；

【导师】 李凤民； James F.Reynolds；

【作者基本信息】 兰州大学 ， 生态学， 2010， 博士

【摘要】 通过广泛的观测数据分析和模型模拟研究,联合国气候变化专门委员会(IPCC)在其2007年发表的气候变化第四次评估报告得出全球气候正在变化的结论。全球气候变化强调了理解全球生物群系(Biome)如何响应这些变化的必要性。本研究利用气象数据、遥感数据等多种数据源和基异值分解(Singular value decompositio)、地理信息系统等多种数量化方法,根据实际气候变化趋势设计了气候(主要是降水和气温)变化情景,并利用生态系统模型(Biome-BGC)模拟了青藏高原生态系统净初级生产力对这些变化的响应,取得以下主要进展：净初级生产力对降水变化的敏感性(即净初级生产力与降水量线性关系中的斜率b)随着年降水量的增加而降低。选取每个研究地点降水量最小年份的降水及其所对应的净初级生产力并进行线性回归,得到青藏高原各生态系统的最大水分利用效率(即该线性回归的斜率)。高敏感性(水分限制,即干旱化环境)生态系统的水分利用效率接近于最大水分利用效率,而低敏感性(非水分限制,即湿润环境)生态系统的水分利用效率远小于最大水分利用效率。减少生长季节的降水量和／或气温升高都使生态系统的水分利用效率接近于最大水分利用效率。近30年来中国西部夏季强降水和干旱年份都有所增加,即降水年际变率增大,而平均降水则无明显变化；夏季平均气温的变率和平均值都有所增加。根据这些变化设计情景模拟了青藏高原植被净初级生产力,分析表明净初级生产力年际变率随降水和／或气温年际变率增加而增加,但其随降水年际变率的增加更为明显。在对降水变化不敏感的研究地点,降水年际变率增加导致多年平均净初级生产力有所减少。而对降水变化敏感的研究地点,降水年际变率的增加对多年平均净初级生产力无明显影响。降水变化的另一个重要特征是降水年内变率的增加,如极端降水增加,降水次数减少,降水间隔时间(干旱时间)增长。这些情景下的净初级生产力模拟表明,低敏感性生态系统的净初级生产力随年内降水变率的增加略有减小；中等和高敏感性生态系统的净初级生产力随年内降水变率的增加而增大。对这一部分的结果的分析需要进一步的实验或利用其它生态系统模型的模拟研究来支持。更多还原

【Abstract】 Based on an extensive synthesis of both empirical and modeling research, the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) unequivocally concludes that global climate is changing. Global climate changes underscore the necessity of understanding how climatic change may affect global biomes. Various data sources (e.g., meteorological records, remote sensing data) and methods (statistics, e.g., singular value decomposition; Geographical Information System, e.g., ArcGIS;ecosystem model, e.g., Biome-BGC) were applied in this study. Based on observed climate change, we designed climate change (mainly precipitation and temperature changes) scenarios to simulate Net Primary Productivity (NPP) with an ecosystem process model (Biome-BGC) in order to assess response of various ecosystems to climate changes. The main progress is as following:NPP at 11 terrestrial ecosystems of four biomes across the Tibetan Plateau in a 40-year period (1969-2008) were simulated by the Biome-BGC model. The relationship between NPP and annual precipitation was analyzed. The sensitivities (change in NPP divided by change in precipitation) of ecosystems decreases across biomes as precipitation increase. However, during the driest years at each site, there is convergence to a common maximum rain use efficiency (RUEmax).Water-limited dry and intermediate sites have RUE that close to RUEmax, whereas non-water-limited mesic sites have RUE that deviates significantly from RUEmax. Decrease in growing season precipitation and/or increase in air temperature resulted in site-level RUE approaching RUEmax. The existence of RUEmax suggests a potential response of biosphere to climate change (precipitation and air temperature).In recent decades, interannual precipitation variability increased in West China, with more frequency of wet and dry events. In addition to an increase in interannual temperature variability, a warming trend is also evident in recent decades. Interannual precipitation and air temperature variabilities decrease across biomes with increased mean annual precipitation. Interannual NPP variabilities increase across biomes with increased interannual precipitation and temperature variabilities. Scenarios were designed to assess response of vegetation productivity to increased interannual precipitation and temperature variabilities. The responses of NPP at 11 terrestrial ecosystems under these scenarios were evaluated. The results suggested that interannual NPP variabilities increased with increasing interannual precipitation and temperature variabilities. Increased interannual precipitation variations resulted in decrease of 40-year mean NPP at sites with low sensitivity to precipitation change, while had marginal impact at high sensitivity sites. Increased between-year air temperature variabilities have marginal impacts on 40-year mean NPP at all sites.Greenhouse-gas-induced climate warming is expected to increase intra-annual precipitation variability, such as a higher frequency of extreme rainfall events, a lower frequency of rainfall events, and longer intervening dry periods. Our analysis suggested that intra-annual precipitation variability decreased across biomes with increasing mean annual precipitation. Under the same warming background, simulated NPP slightly declined at low sensitivity sites as intra-annual precipitation variability increasing, which might be attributed to decreased water availability resulted from substantial increase in outflow at these sites; in contrast, NPP increased at intermediate and high sensitivity sites with increased intra-annual precipitation variability, probably due to increased soil water recharge at these sites. However, more field and simulation works need to be done.更多还原