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

在阿拉斯加冻原生态系统中，灌木和苔藓在调节冬季和夏季地表能量平衡方面发挥着关键作用，并且是植被中限制元素吸收和周转的关键决定因素。 灌木和苔藓的丰富程度预计也会随着气候变暖而发生巨大变化，但目前还不清楚过去几十年的变暖是否真的造成了任何变化。 这项研究将使用长期的实验操作的苔原环境在图利克湖，阿拉斯加，灌木和苔藓的丰度发生了巨大的变化，以提高我们的理解控制灌木和苔藓丰度的变化率，并在气候，灌木和苔藓丰度，树冠结构和表面小气候的变化顺序的时间。 其中一个产品将是灌木和苔藓生长以及与气候有关的树冠结构的人口模型。 第二个目标是记录在阿拉斯加北方的几个苔原站点的产量、生物量和物种组成的年度变化，以便量化这些特征的正常“背景”年度变化。 通过在1960年代和1970年代进行过类似测量的地点进行这项工作，将有可能确定30年或40年的变化是否超过年度变化，或者年度变化是否超过任何长期趋势。 第三个目标是继续开展一系列正在进行的综合活动，以提高对整个北极以及全球气候变化影响的认识。

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.