Rangeland Ecology & Management

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An integrated perspective to explain nitrogen mineralization in grazed ecosystems
Author
Schrama, G F Maarten
S, E
Ruifrok, Jasper L
Bakker, Jan P
Olff, Han
Publisher
Perspectives in Plant Ecology, Evolution and Systematics
Publication Year
2013
Body

Large herbivores are key drivers of nutrient cycling in ecosystems worldwide, and hence they have an important influence on the productivity and species composition in plant communities. Classical theories describe that large herbivores can accelerate or decelerate nitrogen (N) mineralization by altering the quality and quantity of resource input (e.g. dung, urine, plant litter) into the soil food web. However, in many situations the impact of herbivores on N mineralization cannot be explained by changes in resource quality and quantity. In this paper, we aim to reconcile observations of herbivores on N mineralization that were previously regarded as contradictory. We conceptually integrate alternative pathways via which herbivores can alter N mineralization. We illustrate our new integrated perspective by using herbivore-induced soil compaction and subsequent changes in soil moisture and soil aeration as an example. We show that the net effect of herbivores on mineralization depends on the balance between herbivore-induced changes in soil physical properties and changes in the quality and quantity of resource input into the soil food web. For example, soil compaction by herbivores can limit oxygen or water availability in wet and dry soils respectively, particularly those with a fine texture. This can result in a reduction in N mineralization regardless of changes in resource quality or quantity. In such systems the plant community will shift towards species that are adapted to waterlogging (anoxia) or drought, respectively. In contrast, soils with intermediate moisture levels are less sensitive to compaction. In these soils, N mineralization rates are primarily associated with changes in resource quality and quantity. We conclude that our integrated perspective will help us to better understand when herbivores accelerate or decelerate soil nutrient cycling and improve our understanding of the functioning of grazed ecosystems.

Language
English
Resource Type
Text
Document Type
Journal Issue/Article
Journal Volume
15
Journal Number
1
Journal Pages
32-44
Journal Name
Perspectives in Plant Ecology, Evolution and Systematics
Keywords
grazing
trampling
soil compaction
soil texture
Soil Type
Water logging
nutrient cycling
Decomposition
Excreta (dung and urine)
Soil Aeration
herbivores
ecosystem ecology
grazing
browsiing
soils nutrients