Exotic invasive species are nonnative species that thrive outside of their
native habitat, and while it is difficult to determine which exotic plants
will become invasive, successful invaders often share a wide range of traits
including high growth rate and reproductive output, vegetative reproduction,
high population growth rates, early reproductive age, phenotypic and
physiological plasticity, and high resource use efficiency. Here we report
on the response of pampasgrass, an important exotic invasive plant of the
western United States, to experimental variations in soil nitrogen (N) and
water availability. Given its ability to invade a wide variety of ecosystems
in southern California, we hypothesized that pampasgrass would have higher
water and N use efficiency under conditions of low water and N availability
but rapid growth and resource use under conditions of high water and N
availability. Our data support this hypothesis and indicate that pampasgrass
exhibited large variations in growth, carbon allocation, morphology, and N
and phosphorus (P) nutrition to variations in N availability and water table
depth. Many of these traits are highly correlated with invasive performance,
and the high N and P use efficiency observed under low soil N (control) and
water table, coupled with the large increase in physiological performance
and resource use under high N and water table, indicate that pampasgrass is
highly flexible to soil resource levels that are typical for coastal sage
scrub and riparian ecosystems of southern California. Such flexibility in
resource use could allow pampasgrass to persist in low-resource environments
and expand as resource levels increase.