Herbivore effects of soils and ecosystem processes Flashcards
Why is there low plant consumption in forests?
There is a large allocation to woody material
Why is there higher plant consumption in grasslands?
Most biomass is non-woody
What is another factor that can cause variation in levels of plant consumption?
Herbivore species
What is a negative impact of herbivores on soil ecosystems and what is this known as?
Selective grazing leads to deceleration. Defended plants with low tissue nitrogen are consumed less. Reducing the quality of litter and resulting in low fertility forests.
What is a positive impact of herbivores on soil ecosystems and what is this known as?
Positive impacts are more common in fertile ecosystems. The herbivores consume more nutrient-rich plants, producing nutrient-rich waste.
What does the presence of herbivores in fertile ecosystems result in?
Compensatory growth
What did Pastor et al (1993) find when moose were reintroduced to a boreal forest?
A degenerative feedback loop. A shift to conifer dominance, reduced soil microbial activity, which reduced ecosystem productivity and the collapse of the moose population.
What did Harrison and Bardgett (2003) find when looking at the cull of red dear from a birch forest?
Their grazing had been reducing ecosystem productivity. The ecosystem was regenerating after the cull.
Why is nutrient cycling faster in fertile sites with more herbivores?
Animal faeces is a faster alternative to the mechanism of nutrient cycling than litter
What did McNaughton et at (1997) conclude that African grazers were doing?
They modify ecosystem processes to alleviate nutrient deficiencies and elevate the carrying capacity of the ecosystem by accelerating the recycling of plant available sodium
How did a 1998 study find that bears were modifying their environment for a greater food source?
Bears dig for lily bulbs. Digging increases nutrient content and seed production, resulting in a higher production of a high quality food source.
What are some impacts of the degradation of grassland?
Loss of income, reduced carbon sequestration, reduced capacity to deliver ecosystem services
