Changes in ecological stability across realistic biodiversity gradients depend on spatial scale

TitleChanges in ecological stability across realistic biodiversity gradients depend on spatial scale
Publication TypeJournal Article
Year of Publication2013
AuthorsChalcraft DR
JournalGlobal Ecology and Biogeography
Accession NumberJRN00607
KeywordsChihuahuan Desert, ecosystem dynamics, grasslands, population dynamics, scale dependence, synchrony

Aim: It is unclear how the stability of natural ecosystems and populations varies
with biodiversity at spatial scales relevant to resource managers. This study evaluates
whether theory and prior experiments adequately predict how stability varies
with a measure of biodiversity, plant species richness, at multiple scales in naturally
assembled ecosystems and assesses mechanisms through which biodiversity is proposed
to affect stability.
Location: Chihuahuan desert. Historically, grasslands represented the dominant
vegetation type in this landscape and shrubs were uncommon. Desertification has
degraded many native grassland regions into one of several alternate states dominated
by different shrub species and these regions differ in biodiversity.
Methods: Researchers at the Jornada long-term ecological research site have
amassed 12 years of data on the primary productivity of individual plant species in
735 permanent 1-m2 plots distributed among 15 regions that were all historically
grasslands. I used this information to describe the relationship between biodiversity
and stability at the local (1 m2) and regional (3721 m2) scale and to evaluatemechanisms
through which biodiversity is proposed to affect stability.
Results: At the local scale, ecosystem stability increased linearly with biodiversity
while population stability tended to decline with biodiversity. At the regional scale,
both ecosystem and population stability increased as a saturating function of biodiversity.
Scale-dependent change in the biodiversity–stability relationship can be
explained by the spatial insurance hypothesis, asynchrony in the local productivity
dynamics of the average species, and a change in species evenness with scale that
weakens statistical averaging.
Main conclusions: Results from small-scale experimental studies may not
directly translate to larger spatial scales but they appear to predict patterns in
natural communities at small spatial scales. These results suggest that the maintenance
of high biodiversity over a large spatial area is essential for maintaining
ecosystem services and reducing the potential for further species extinctions.