Resource limitation of compensatory responses in ecosystem processes after biodiversity loss

Biodiversity loss may result in a decline in important ecosystem
processes. The effect of biodiversity loss on ecosystem functioning is
determined by the functional contribution of the species lost and the
compensatory responses of the remaining species. It is unknown to what
extent the strength of the compensatory response of the remaining species
depends on resource availability. Here we evaluate how the primary
production of an assemblage of salt marsh plants responds to a realistic
sequence of species loss in a 7-year experiment, with and without the
addition of fertiliser. We found near-full compensation of progressive
species loss in gross community primary production by the
extinction-resistant species with fertiliser as long as one species
(Triglochin maritima) remained. Without fertiliser, at least 4 species,
including the particularly abundant species Plantago maritima, were needed
to maintain gross community primary production. These results suggest that
the magnitude of the compensation by extirpation-resistant species for the
decline in ecosystem processes associated with progressive biodiversity
loss depends on the resource context, and that compensation after the loss
of plant species can be accelerated by increasing resource availability.
Ultimately, full compensation appears to be limited by the presence and
abundance of species in the remaining community that possess traits that
allow them to compensate for the species lost. These findings suggest that
the conclusions of a large body of biodiversity-ecosystem experiments
cannot be used for informing the management of natural systems, because
they do not simulate realistic extinction sequences, and therefore cannot
quantify the potential for compensation of ecosystem services in the real
world.