van Wijk Mark T, Williams Mathew, Shaver Gaius R
School of GeoSciences, University of Edinburgh, Darwin Building, Edinburgh, EH9 3JU, UK.
Oecologia. 2005 Jan;142(3):421-7. doi: 10.1007/s00442-004-1733-x. Epub 2004 Nov 10.
The large spatial heterogeneity of arctic landscapes complicates efforts to quantify key processes of these ecosystems, for example productivity, at the landscape level. Robust relationships that help to simplify and explain observed patterns, are thus powerful tools for understanding and predicting vegetation distribution and dynamics. Here we present the same linear relationship between Leaf area index (LAI) and Total foliar nitrogen (TFN), the two factors determining the photosynthetic capacity of vegetation, across a wide range of tundra vegetation types in both northern Sweden and Alaska between leaf area indices of 0 and 1 m2 m(-2), which is essentially the entire range of leaf area index values for the Arctic as a whole. Surprisingly, this simple relationship arises as an emergent property at the plant community level, whereas at the species level a large variability in leaf traits exists. As the relationship between LAI and TFN exists among such varied ecosystems, the arctic environment must impose tight constraints on vegetation canopy development. This relationship simplifies the quantification of vegetation productivity of arctic vegetation types as the two most important drivers of productivity can be estimated reliably from remotely sensed NDVI images.
北极景观的巨大空间异质性使得在景观层面量化这些生态系统的关键过程（例如生产力）变得复杂。有助于简化和解释观测模式的稳健关系，因此是理解和预测植被分布与动态的有力工具。在此，我们展示了叶面积指数（LAI）和总叶氮（TFN）之间相同的线性关系，这两个因素决定了植被的光合能力，涵盖了瑞典北部和阿拉斯加广泛的苔原植被类型，叶面积指数在0至1平方米每平方米之间，这基本上是整个北极叶面积指数值的范围。令人惊讶的是，这种简单关系作为植物群落层面的一种涌现特性出现，而在物种层面，叶性状存在很大变异性。由于LAI和TFN之间的关系存在于如此多样的生态系统中，北极环境必定对植被冠层发育施加了严格限制。这种关系简化了北极植被类型植被生产力的量化，因为生产力的两个最重要驱动因素可以从遥感归一化植被指数（NDVI）图像中可靠地估算出来。
