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Generalities in grazing and browsing ecology: using across-guild comparisons to control contingencies
1Department of Wildland Resources, Utah State University, Logan, UT, 84322-5230, USA, johan.dutoit@usu.edu.
Oecologia
|January 7, 2014
Summary
Comparing grazing and browsing herbivores reveals general ecological principles. This approach helps understand how plant traits, not just herbivore type, regulate nutrient cycling and structure animal communities.
Area of Science:
- Community ecology
- Trophic interactions
- Large mammal herbivory
Background:
- Spatial replication in community ecology addresses within-group patterns but struggles with across-group contingencies.
- Contingencies in ecological processes across different species groups, like grazing and browsing guilds, remain a challenge.
- Understanding generalities requires methods that transcend specific consumer-resource dynamics.
Purpose of the Study:
- To identify general ecological principles by comparing grazing and browsing guilds of large mammals.
- To use one trophic guild as a control for the other to uncover non-contingent patterns.
- To resolve debates on ungulate impact on nutrient cycling by comparing grazing and browsing effects.
Main Methods:
- Focused review of literature on grazing and browsing by large mammals.
- Comparative analysis of grazing succession and browsing stratification.
- Application of the Jarman-Bell principle to explain resource partitioning and dietary tolerance.
Main Results:
- The Jarman-Bell principle illustrates how metabolic and digestive allometries drive resource partitioning in both grazing and browsing guilds.
- Competition among smaller herbivores, not facilitation by larger ones, structures ungulate assemblages when resources are limited.
- Grazing lawns and browsing hedges exhibit functional similarities, with plant tolerance traits mediating herbivory under enhanced resource conditions.
- Nutrient cycling rates in African savannas are determined by plant traits (tolerance vs. resistance), not the dominance of grazing or browsing.
Conclusions:
- An across-guild comparative approach offers a novel solution for resolving contingencies in community processes.
- General ecological principles can be identified by treating different trophic guilds as comparative controls.
- Plant traits play a crucial role in regulating ecosystem processes like nutrient cycling in herbivore-dominated systems.
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