ALT Illustration of the changes in active layer thickness and water table height from graminoid to wetland tundra and then from prostrate- and erect-shrub tundra toward the boreal forest. Roots of many plant functional types in these highly organic soils are limited in their downward distribution at various points along this latitudinal gradient by permafrost and high-water tables.

ALT Text reads: Our ability to understand and predict belowground plant form and function now and in response to changing environmental conditions over the next 50–100 yr will depend on accurately quantifying baseline values of rooting depth distribution in places like the arctic tundra and boreal forest.