Nutrient Cycling

When grazing animals reduce biomass and litter and/or change plant species composition, nutrient cycling and energy flow can also be altered. This alteration has an indirect effect on biodiversity in that changes in nutrient cycling can initiate changes in habitat diversity. If grazing animals suppress nitrogen-fixing plants, less nitrogen may be available to the system. Because herbivores feed selectively, their food items usually have higher nutrient content than vegetation not selected. These same highly digestible plants are also those that, if allowed to become litter, would decompose relatively rapidly. If grazing is not managed to prevent the decline of preferred forage plants and the concomitant increase of unpalatable, less-degradable plants, rates of nutrient cycling may decline. Aboveground herbivory can decrease aboveground biomass, belowground production, soil elevation, and expansion of the root zone. Grazing can have a negative effect on the soil-building process.

Conversely, grazing can increase nutrient cycling through the deposition of urine and dung to contribute to the pool of nitrogen in the soil that is readily available for plant growth. This process decreases the carbon-to-nitrogen ratio of the soil, which increases litter decomposition rates. Also in some cases, higher availability of soil nitrogen enhances the productivity of deciduous species, while low availability enhances conifer production.

Deciduous species have more potential as forage plants and themselves provide more readily decomposed litter than conifers.

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