Ecosystem properties determined by plant functional group identity
McLaren, J.R. and R. Turkington. 2010. Journal of Ecology 98:459-469
Abstract
1. Ecosystem properties may be determined by the number of different species or groups of species
in a community, the identity of those groups, and their relative abundance. The mass ratio theory
predicts that the effect of species or groups of species on ecosystem properties will be dependent on
their proportional abundance in a community.
2. Single plant functional groups (graminoids, legumes, non-leguminous forbs) were removed from
a natural grassland in northern Canada to examine the role of group identity in determining both
ecosystem properties and biomass compensation by remaining species. Removals were conducted
across two different environmental treatments (fertilization and fungicide) to examine the context
dependency of functional group identity effects.
3. The degree of biomass compensation in the first 4 years after removal was influenced by the identity
of the functional group removed and also of those remaining. When graminoids were removed,
none of the remaining functional groups compensated for the loss of biomass. Graminoids partially
compensated for the removal of forbs or legumes, with the degree of compensation depending on
environmental treatments.
4. Light interception, soil moisture and soil nutrients were all influenced by functional group
identity, with graminoids having a greater impact than expected based on their biomass contribution
to the community. Legumes, in contrast, had very little effect on any of the ecosystem properties
measured.
5. For most ecosystem properties measured, the role of plant functional groups was not context
dependent; functional groups had the same effect on ecosystem properties regardless of fertilization
or fungicide treatments.
6. Synthesis. We have shown that the effects of losing a functional group do not solely depend on
the group's dominance. In this northern grassland, there are greater effects of losing graminoids
than one would predict based on their biomass contributions to the community, and functional
group identity plays a critical role in determining the effects of diversity loss.
Key Words
biodiversity, ecosystem function, fertilization, mass ratio hypothesis, mycorrhizae,plant functional group, removal experiment
