Thermal segregation drives patterns of alder and willow expansion in a montane ecosystem subject to climate warming

1.Tall-shrub expansion into low-statured communities, a hallmark of recent vegetative change across tundra ecosystems, involves three major genera: Alnus, Betula, and Salix. Which genus expands most into tundra landscapes will determine ecosystem properties.

2.We show that Alnus and Salix shrubs segregate thermal space (elevation x insolation) and colonize tundra landscapes differently in response to climate warming, thereby replacing different tundra types.

3.Vegetative change estimated from repeat photography should account for hill-slope. Methodologically, slope determines surface area estimated from orthophotos as projected pixel area times secant of pixel slope. Ecologically, the change in thermally-responsive vegetative area is sensitive to terrain steepness, scaling as the cosecant of hill-slope, so that studies should expect more shrub expansion in areas of shallow slopes than steep slopes.

4.Repeat aerial photography in Alaska's Chugach Mountains from 1972-2012 orthore...

1.高大灌木向低矮植物群落扩张是近年来苔原生态系统植被变化的显著标志，涉及三个主要属：桤木属（Alnus）、桦木属（Betula）和柳属（Salix）。哪个属在苔原景观中扩张最显著，将决定生态系统的特性。

2.我们的研究表明，桤木属和柳属灌木在热空间（海拔×日照）中呈现空间分隔，并且在气候变暖的响应下以不同方式定植苔原景观，从而取代不同类型的苔原。

3.通过重复摄影估算植被变化时，应考虑山坡坡度。方法论上，坡度决定了从正射影像估计的表面积，计算方式为投影像素面积乘以像素坡度的正割值。生态学上，热响应植被面积的变化对地形陡峭度敏感，其缩放比例为山坡坡度的余割值，因此研究应预期缓坡区域的灌木扩张比陡坡区域更明显。

4.1972-2012年阿拉斯加楚加奇山脉的重复航空摄影正射...