Linking Restoration and Ecological Succession (Springer ... - Inecol

50 David A. Wardle and Duane A. Peltzer
Role of herbivory
Compensatory plant
growth responses
high % NPP consumed
most OM returned to soil
as fecal material
Plant traits
high growth rate
short-lived tissue
Decomposer subsystem
high litter quality
high rates decomposition
and mineralization
low rates of carbon
sequestration in soil
high shoot leaf area
poorly defended leaves
high leaf nutrient content
EARLY SUCCESSIONAL
ECOSYSTEMS
High supply
rates of
plant
available
nutrients
Retardation of
succession
(Foliar
herbivores)
HERBIVORY
Acceleration of
(Foliar and root
herbivores)
NUTRIENT REPLETE NUTRIENT-LIMITED
Succession
succession
Low supply
rates of
plant
available
nutrients
Plant traits
slow growth rate
long-lived tissues
low shoot leaf area
well-defended leaves
low leaf nutrient content
Role of herbivory
noncompensatory plant
growth responses
low % of NPP consumed
most OM returned to soil
as litter
Decomposer subsystem
low litter quality
low rates of decomposition
and mineralization
high rates of carbon
sequestration in soil
LATE SUCCESSIONAL
ECOSYSTEMS
Figure 3.2 Mechanistic basis of how herbivores affect the decomposer subsystem at a plant community level,
through altering successional trajectories. Reproduced from Bardgett and Wardle (2003) with permission from the
Ecological Society of America.
3.3 Browsing Mammals and New Zealand Rainforests
Foliar herbivory is an important driver of many ecosystems, and depending
on the ecosystem considered, between 1 and 50% of NPP is consumed by
herbivores (McNaughton et al. 1989). The intensity of herbivory is influenced by
succession, with earlier successional systems often being subjected to a greater
intensity of herbivory than later successional systems. Further, herbivores are
important in influencing the direction and rate of vegetation succession; in fertile
systems, herbivores retard succession while in infertile systems they promote
succession (Bardgett and Wardle 2003) (Fig. 3.2).
Aboveground herbivores influence not just plant growth and plant communities,
but also indirectly affect decomposers and decomposer processes across a
range of temporal and spatial scales (Bardgett et al. 1998, Wardle and Bardgett
2004). In the short-term, herbivory can induce significant flow of C from the
plant to the rhizosphere microflora, creating an aboveground feedback through
enhancing N availability for the plants (Hamilton and Frank 2001). In the longer