【作者】 王晓东；

【导师】 刘惠清；

【作者基本信息】 东北师范大学 ， 自然地理学， 2011， 博士

【摘要】 当前全球环境变化问题日益严重,尤其是气候变暖的加速已引起高度关注,特别是生态系统对气候变化的响应方式和应对策略更是激起众多学者的极大兴趣。林线对气候变化高度敏感,林线变动是气候变化的指示器。探讨林线与气候变化的关系对揭示生态系统对气候变化的响应有先导意义。长白山地处中国东北东部,为东北亚著名高山,其北坡从针阔混交林带至山地苔原带垂直带谱齐全,林线发育良好,是研究林线变动、生态系统演替与气候变化的理想地段。本文选取长白山北坡林线为典型区,探讨林线变动对气候变化的响应,以此为切入点探讨气候变化对生态系统的影响。在长白山北坡林线带设置7条样带,采用遥感影像、样方调查、树轮分析等手段结合数字地形、气象资料等数据,运用数理统计、GIS技术和树轮分析技术分析长白山北坡林线56年(1953-2008)和近150年(1860-2008)不同时间尺度的气候变化特点,从种群、群落、景观尺度分析林线动态对气候变化的响应方式及地形土壤等生态因子对响应过程的影响。气温变化的动态分析显示长白山林线56年来经历了3次高温期,80年代末以来气温迅速提升;东北地区近150年来气温呈波动上升的态势,有3次明显的高温期(1875-1881;1919-1932;1989-2008)和四次低温期交替出现(1860-1872;1891-1910;1939-1956;1976-1988),且升温幅度逐次攀升,高温持续期延长、低温期缩短的特点。这一特点与长白山北坡56年来的气温变化态势吻合,印证了东北和长白山北坡近年气温升高的事实。在气温升高的大趋势下,无论是在突变型林线、前缘树岛还是整个北坡林线岳桦种群都普遍上侵,对气候变化做出积极响应。突变型林线岳桦按径级从小到大生长阶段明显分为适应期,弱胁迫期和胁迫期,与气温变化规律一致。当气温升高时,岳桦以树高生长加快的方式做出明显的响应。树岛和整个北坡林线岳桦以调整繁殖方式与生存数量对气温变化做脉动式响应。在气温升温不明显阶段,岳桦以无性繁殖的灌木状地下根占领点状生态位完成繁殖和生长过程;在温度明显增高阶段,以有性繁殖的乔木状生长方式实现种群的增长与面状领域的扩张。岳桦以无性繁殖与有性繁殖相结合实现在气候变暖情况下林线的上移和种群的扩张,数理统计和GIS技术的时空分析显示种群动态对气候变化响应积极(相关系数高),对气温变化的敏感度高于降水变化(气温的相关系数与纳入频数>降水),气候变暖导致长白山北坡林线岳桦沿海拔由低向高差异性扩张(p<0.05)。气温变暖不仅使岳桦种群上侵,而且促使岳桦林下灌木草本植物相继移动,即林线上侵不仅是单一岳桦种群的变化,而是森林群落向苔原群落的整体入侵,在空间上抢占生态位的过程。在林线上侵过程中,群落各种组分的上侵与后退亦存在差异。岳桦群落上移过程中当岳桦种群占领苔原生态位后,岳桦林下的牛皮杜鹃随之入侵,开始挤占苔原植物生态位,当小叶章等草本植物完成入侵后,岳桦群落在整体上替代苔原群落。以1989、2000、2005和2009年四期长白山北坡林线影像为数据源,利用22个景观指数分析林线景观动态对气候变化的响应方式。林线斑块面积变化的复杂性变大,斑块形状变动先复杂后简单,林线景观格局在波状中趋于简单。林线景观动态与气温波状上升的态势相吻合,当气温快速上升,林线景观斑块形状、景观格局变为复杂。当气温平稳上升,林线景观斑块形状趋向规则,景观格局趋向简单,气温上升促使林线景观不断调整以实现林线的上侵。采用温暖指数(WI)和湿润指数(HI)分析林线高度变化的交互作用不显著(p>0.05),呈负相关(r=-0.11<0),上侵不能达到各自的潜在高度,位置波动在1975-2231m。林线上缘波动的复杂程度高于下缘,波动幅度与胁迫力的大小呈正相关。长白山北坡林线因小地形的影响其上侵的速率和方式不同。逐步回归分析和相关分析结果表明北坡林线处相邻的三坡(东南、东北、东坡)的岳桦种群扩张差异是坡向导向的气温差异造成的,不同坡向上岳桦种群扩张的差异是对气候变化差异性响应的结果。土壤因子对岳桦种群的扩张亦有一定的制约作用,但不足以决定林线的进退,岳桦通过不断调整生活型克服土壤约束以应对气候变化。更多还原

【Abstract】 The significant climate warming has received high attention with increasingly serious global environmental problem. Many researchers are interested in response modes and coping strategies of ecosystem to climate change. Alpine treeline is regarded as highly sensitive and potential indicator of climate change. Therefore, Alpine treeline has become one of the hotspots in global climate change research. Changbai Mountains lies in the eastern region of Northeast China with the well-known montains in Northeast Asia. Alpine treeline of north-facing slopes of Changbai Mountains provides an excellent opportunity to explore its characteristics associated with climate change. This paper aimed to understand the relationship between climate change and treeline dynamics, treeline as study area. The relationship was a breakthrough point to reveal how expanse strategies of ecosystem to climate change.We sampled 7 typical plots located in the treeline on the north-facing slopes of Changbai Mountains as study area using some mathematical statistics methods associated with GIS and tree-ring technologies, based on remotely sensed information, digital elevation model (DEM), measured meteorological records, tree-ring analysis and field investigations. Specific objectives of this study are to 1) to examine climate change characteristics in the treeline at 56(1953-2008)and 149 years (1860-2008);2) analyze the relationship between Betula ermanii population dynamics and climate change;3) discover the response modes of treeline dynamics to climate change at community and landscape scale;and 4) understand the influence degrees of some factors related to topography and soil on the treeline change.The results of temperature change showed that there were three megathermal periods for 56 years and an obviously increasing trend since the late 1980s at Changbai Mountains treeline. Air temperature had wavelike rise for 149 years with cold and warm period’s alternation. Sustained time was gradually short in cold period and long in warm period. The warm periods overlap, rising amplitude and fluctuation range of air temperature would lead to hazard increase of ecosystem in Northeast China.population expansion of Betula ermanii was obvious as air temperature increasing. The tree height growth for Betula ermanii is divided into adaptive phase, low stress phase and high stress phase according to its size class from small to big at closed treeline. The tree height growth was the well-ordered at high temperature period. However, it was restricted at low temperature period. Different propagation forms and the annual stem recruitment of Betula ermanii population responded significantly to the fluctuation of air temperature increase. The population continued to vary its physiological traits for the population expansion and the domain enlargement. Under global warming background, the population expansion and the domain enlargement of Betula ermanii led to treeline shift. Statistics analyses and GIS technology were completed on the relationship betweenBetula ermanii population dynamics and climate change over temporal and spatial dimensions. The result of showed that Betula ermanii population responded significantly to climate change (high correlation coefficients). It was more sensitive to the change of air temperature than that of precipitation (correlation coefficients and including frequencies of air temperature> precipitation). Increases in air temperature led the population to expand differently along altitude from low to high. The results of statistics analyses showed that population expansion of Betula ermanii drove the shifts of shrub and grass belonged to forest community. Treeline shift was tree change. In addition, forest community invaded tundra community too. Therefore, The ecological niche of tundra community was excluded by forest community. Moreover, the change difference among different compositions of tundra was very obvious. The difference was very obvious during replacement process of varied plants due to the distinction of competitive and status in community.Based on 4 years’images (1989, 2000, 2005 and 2009) at treeline on North Slope of Changbai Mountains. Dynamics response pattern of treeline landscape to climate change was investigated using 22 landscape indices. The results showed that change complexity of patch area got bigber and the change pattern of patch shape area was easy at first and then became complex. Landscape pattern grudually became simple with wavy feature. The treeline landscape dynamics was in accordence with the wavy increase air tempreture. As air temperature quicly increased, landscape pattern and patch shape became complex. When air temperature steadily increased, patch shape became regular and landscape pattern was gradually simple. Air temperature increase made treeline landscape continue to ajust its feature in order to complete treeline shift.The interaction of two treeline shifts determined by warmth index (WI) and humid index (HI) respectively was not significant (p>0.05). In addition, there was negative correlation between two treelines change (r=-0.11<0). Therefore, Two treelines were unable to reach their potential height. The slope of Betula ermanii treeline was estimated as from 1975 to 2231m. The fluctuation process was simple in lower treeline. However, the complex fluctuation process in upper treeline indicated that fluctuation of treeline shift increased due to large stress. The results of correlation analysis and stepwise regression showed that different responses of population dynamics to climate change caused by different temperature on three slopes (southeast slopes, northeast slopes and east slopes). The differences of climate change led to different expansion of Betula Ermanii population on different positions. Soil factor had a certain restrictive function to population dynamics of Betula ermanii. However, it did not play a crucial role in treeline shifts. The population tended to continuously adjust its life forms to adapt air temperature change in order to overcome soil restrictions.更多还原