NDLI: Walter’s two-layer hypothesis revisited: back to the roots!

Content Provider	Springer Nature Link
Author	Ward, David Wiegand, Kerstin Getzin, Stephan
Copyright Year	2012
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.
Starting Page	617
Ending Page	630
Page Count	14
File Format	PDF
ISSN	00298549
Journal	Oecologia
Volume Number	172
Issue Number	3
e-ISSN	14321939
Language	English
Publisher	Springer-Verlag
Publisher Date	2012-12-25
Publisher Place	Berlin, Heidelberg
Access Restriction	One Nation One Subscription (ONOS)
Subject Keyword	Savanna Tree–grass coexistence Codominance Equilibrium theory Patch dynamics Spatial heterogeneity Resource partitioning Root distributions Water Ecology Plant Sciences
Content Type	Text
Resource Type	Article
Subject	Ecology, Evolution, Behavior and Systematics

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Walter’s two-layer hypothesis revisited: back to the roots!

Walter’s two-layer hypothesis revisited: back to the roots!

CONCEPTS, REVIEWS AND SYNTHESES Walter’s two-layer hypothesis revisited: back to the roots!

The rhythm of savanna patch dynamics

Plant responses to precipitation in desert ecosystems: integrating functional types, pulses, thresholds, and delays

Tree-grass coexistence in a flood-disturbed, semi-arid savanna system

Spatio-temporal trends in tree cover of a tropical mesic savanna are driven by landscape disturbance

Fire controls population structure in four dominant tree species in a tropical savanna

Root‐niche separation between savanna trees and grasses is greater on sandier soils

Walter’s two-layer hypothesis revisited: back to the roots!

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Walter’s two-layer hypothesis revisited: back to the roots!

Walter’s two-layer hypothesis revisited: back to the roots!

CONCEPTS, REVIEWS AND SYNTHESES Walter’s two-layer hypothesis revisited: back to the roots!

The rhythm of savanna patch dynamics

Plant responses to precipitation in desert ecosystems: integrating functional types, pulses, thresholds, and delays

Tree-grass coexistence in a flood-disturbed, semi-arid savanna system

Spatio-temporal trends in tree cover of a tropical mesic savanna are driven by landscape disturbance

Fire controls population structure in four dominant tree species in a tropical savanna

Root‐niche separation between savanna trees and grasses is greater on sandier soils

Walter’s two-layer hypothesis revisited: back to the roots!