Aridity and soil fertility, not species richness, interact to affect temporal stability along a large natural gradient in Northern China

There is mounting evidence from experimental studies that drought and
nutrient enrichment can interact to impact the biodiversity and
productivity of terrestrial ecosystems. Whether such interactive effect
influence plant diversity and the temporal stability of community
productivity of natural ecosystems is unknown. To fill this knowledge gap,
we combined a field survey of plant diversity and soil conditions with
remote sensing temporal estimates of primary productivity in grasslands
along a natural gradient in northern China. We found that aridity and soil
ammonium (NH4+-N) interacted to influence temporal stability of NDVI. That
is, the relationship between ammonium and temporal stability of NDVI
shifted from positive to negative due to increased standard deviation of
NDVI with increasing aridity. Species richness was not related to temporal
stability because it influenced the mean and standard deviation of NDVI
proportionally. As a result, soil fertility outweighed the contribution of
species richness to temporal stability. Our study demonstrates the
synergistic effect of aridity and soil fertility, but not species
richness, on temporal stability along a large natural gradient. Predicting
how environmental drivers affect diversity and the stable provisioning of
ecosystem services in real-world ecosystems therefore requires a better
understanding of the complex interactions among environmental drivers.