Abstract:
AIM : Nutrient enrichment is associated with plant invasions and biodiversity loss.
Functional trait advantages may predict the ascendancy of invasive plants following
nutrient enrichment but this is rarely tested. Here, we investigate (a) whether dominant
native and non-native plants differ in important morphological and physiological
leaf traits, (b) how their traits respond to nutrient addition, and (c) whether responses
are consistent across functional groups.
LOCATION : Australia, Europe, North America and South Africa.
TIME PERIOD : 2007–2014.
MAJOR TAXA STUDIED : Graminoids and forbs.
METHODS : We focused on two types of leaf traits connected to resource acquisition:
morphological features relating to light-foraging surfaces and investment in tissue
(specific leaf area, SLA) and physiological features relating to internal leaf chemistry
as the basis for producing and utilizing photosynthate. We measured these traits
on 503 leaves from 151 dominant species across 27 grasslands on four continents.
We used an identical nutrient addition treatment of nitrogen (N), phosphorus (P) and
potassium (K) at all sites. Sites represented a broad range of grasslands that varied
widely in climatic and edaphic conditions.
RESULTS : We found evidence that non-native graminoids invest in leaves with higher
nutrient concentrations than native graminoids, particularly at sites where native and
non-native species both dominate. We found little evidence that native and nonnative
forbs differed in the measured leaf traits. These results were consistent in
natural soil fertility levels and nutrient-enriched conditions, with dominant species responding similarly to nutrient addition regardless of whether they were native or non-native.
MAIN CONCLUSIONS : Our work identifies the inherent physiological trait advantages
that can be used to predict non-native graminoid establishment, potentially because
of higher efficiency at taking up crucial nutrients into their leaves. Most importantly,
these inherent advantages are already present at natural soil fertility levels and are
maintained following nutrient enrichment.
