欧亚大陆草原带主要包括哈萨克草原和蒙古草原,是世界上最大的过渡生态系统。同时该区域属于典型的干旱半干旱地带,因此对气候变化较为敏感。但是,针对该区域的净初级生产力(net primary productivity,NPP)研究尚有诸多不足,特别是哈萨克草原。本研究在原有BEPS(Boreal Ecosystem Productivity Simulator)模型的基础上,对光合最大羧化效率(V_(c,max))和自氧呼吸等过程算法进行了优化,以地面实测样方数据对改进后的模型进行精度验证,进而利用改进后的BEPS模型模拟了1982-2008年间的欧亚大陆草原带植被净初级生产力。结果表明,改进的BEPS模型与3个地区(哈萨克斯坦,内蒙古和新疆)的样地观测数据相比均具有较好的拟合精度,且预测能力较原有BEPS模型均有一定程度的提升;27年间,区域内NPP的平均值为120g C/m~2,其中蒙古草原为116.9 g C/m~2,哈萨克草原为122g C/m~2。在区域暖干化的背景下,蒙古草原的NPP呈现上升趋势,而哈萨克草原则在前苏联解体前后先上升后下降。区域内草地主要与年降水具有显著的正相关关系,而对温度的响应普遍较弱,表明降水是该区域植被生长的主要气候影响因子。
英文摘要:
The Temperate Eurasian Steppe(TES)is the worlds largest continuous vegetation transition zone. Made up mainly of the Kazakh and Mongol Steppe.TES is a typical arid/semi-arid zone and sensitive to climate change.However,little is known about its net primary productivity(NPP),especially for the Kazakh Steppe. In this study,an improved boreal ecosystem productivity simulator(BEPS)model was used to simulate NPP in TES from 1982to 2008.The BEPS algorithms for maximum carboxylation efficiency and autotrophic respiration were improved to make them more applicable to arid/semi-arid regions and then validated by long-term field observations in Kazakhstan,Inner Mongolia and Xinjiang.Results indicated that the improved model could enhance NPP simulation.Over the 27-year period from 1982to 2008,the average TES NPP was 120g C/ m~2,of which 116.9g C/m~2 was located in the Mongol Steppe and 122g C/m~2 in the Kazakh Steppe.In a context of a regionalwarming and dryingtrend,the Mongol Steppe exhibited an obvious increasing NPP trend for the entire study period,while NPP in the Kazakh Steppe increased before 1991and then decreased.The regional NPP showed a significant positive correlation with precipitation but was weakly correlated with temperature, suggesting that precipitation is the primary climatic factor that impacts regional grassland growth.