Publication Details

Category Text Publication
Reference Category Journals
DOI 10.1007/s00442-012-2538-y
Title (Primary) Walter’s two-layer hypothesis revisited: back to the roots!
Author Ward, D.; Wiegand, K.; Getzin, S.
Source Titel Oecologia
Year 2013
Department OESA
Volume 172
Issue 3
Page From 617
Page To 630
Language englisch
Keywords Savanna; Tree–grass coexistence; Codominance; Equilibrium theory; Patch dynamics; Spatial heterogeneity; Resource partitioning; Root distributions; Water
UFZ wide themes RU5;
Abstract Walter (Jahrb Wiss Bot 87:750–860, 1939) proposed a two-layer hypothesis, an equilibrium explanation for coexistence of savanna trees and grasses. This hypothesis relies on vertical niche partitioning and assumed that grasses are more water-use efficient than trees and use subsurface water while trees also have access to deeper water sources. Thus, in open savannas, grasses were predicted to predominate because of their water use efficiency and access to subsurface water. This hypothesis has been a prominent part of the savanna literature since first proposed. We review the literature on Walter’s hypothesis and reconsider his original intentions. Walter intended this hypothesis to be restricted to dry savannas. In his opinion, mesic and humid savannas were controlled by biotic factors and disturbances. We surveyed the global savanna literature for records of vertical niche partitioning by grasses and trees. We find that, within the scope of Walter’s original intentions, this hypothesis works remarkably well, and in some cases is appropriate for deserts as well as for dry temperate systems and even some mesic savannas.
Persistent UFZ Identifier
Ward, D., Wiegand, K., Getzin, S. (2013):
Walter’s two-layer hypothesis revisited: back to the roots!
Oecologia 172 (3), 617 - 630 10.1007/s00442-012-2538-y