Primary Production in Arctic Ecosystems: Interacting Mechanisms of Response to Climate Change

在阿拉斯加冻土带生态系统中，灌木和苔藓在调节冬季和夏季地表能量平衡中起着关键作用，是植被吸收和转换限制元素的关键决定因素。预计随着气候变暖，灌木和苔藓的丰度也会发生巨大变化，但到目前为止，过去几十年的变暖是否真的造成了任何变化，目前还不清楚，也存在争议。本研究将利用对阿拉斯加图里克湖冻土带环境的长期实验操作，在那里灌木和苔藓丰度发生了巨大变化，以提高我们对灌木和苔藓丰度变化率的控制，以及对气候、灌木和苔藓丰度、冠层结构和地表小气候变化顺序的时序的理解。其中一个产品将是基于人口统计学的灌木和苔藓生长模型，以及树冠结构与气候的关系。第二个目标是记录阿拉斯加北部几个冻土带地点的产量、生物量和物种组成的年变化，以便量化这些特征的正常“背景”年变化。通过在20世纪60年代和70年代进行类似测量的地点进行工作，将有可能确定30年或40年的变化是否超过年变化，或者年变化是否超过任何长期趋势。第三个目标是继续进行一系列正在进行的综合活动，以提高对整个北极以及全球一级气候变化影响的了解。

In Alaskan tundra ecosystems, shrubs and mosses play key roles in regulating surface energy balance in both winter and summer, and are key determinants of the uptake and turnover of limiting elements in the vegetation. Shrub and moss abundance is also expected to change dramatically with climate warming, but it is still unclear and controversial whether the warming of the last few decades has actually caused any changes thus far. This research will use long-term experimental manipulations of the tundra environment at Toolik Lake, Alaska, where shrub and moss abundance have changed dramatically, to improve our understanding of controls on the rate of change in shrub and moss abundance, and on the timing of the sequence of changes in climate, shrub and moss abundance, canopy architecture, and surface microclimate. One product will be demographically-based models of shrub and moss growth and canopy architecture in relation to climate. A second objective is to document annual variation in production, biomass, and species composition at several tundra sites in northern Alaska, so as to quantify the normal "background" annual variation in these characteristics. By doing the work at sites where similar measurements were made during the 1960s and 1970s, it will be possible to determine whether the changes over 3 or 4 decades exceed the annual variation or whether annual variation exceeds any long-term trends. A third objective is to continue a series of ongoing synthesis activities aimed at improving understanding of climate change effects at the level of the entire Arctic as well as globally.