%0 Journal Article
%T Nutrients mitigate the impacts of extreme drought on plant invasions
%A Edwin D. Grosholz
%A Megan A. Kelso
%A Rachel D. Wigginton
%J Ecology - Wiley Online Library
%D 2019
%R https://doi.org/10.1002/ecy.2980
%X Extreme climate events, such as drought, are becoming increasingly important drivers of plant community change, yet little is known about their impacts on invasive plants. Further, drought impacts may be altered by other anthropogenic stressors, such as eutrophication. We found drought dramatically reduced density of invasive Lepidium latifolium in salt marshes, and this die坼back was mitigated by nutrient addition. In a 3坼yr field experiment (2014每2016) conducted during an unprecedented drought (2012每2015), we tracked the effects of drought and nutrient addition on the plant community. We conducted this research at four salt marshes across a salinity gradient in the San Francisco Bay, California, USA. We manipulated paired native and invaded plots, one坼half of which were treated monthly with N and P for 1.5 yr during the most intense period of the drought and one subsequent wet winter. In addition, we monitored unmanipulated L. latifolium坼invaded transects within our freshest and most saline sites throughout the three years of our manipulative experiment and one additional wet winter. We documented a dramatic die坼back of invasive L. latifolium during extreme drought, with reductions in stem density (52每100%) and height (17每47%) that were more severe at low salinity sites than high salinity sites. We found nutrient application lessened the effect of drought on L. latifolium stem density, but not height. In native plots, extreme drought reduced native plant cover (4每24%), but nutrient addition mitigated this impact. Interestingly, native plants in invaded plots did not suffer reductions in cover due to drought, perhaps because they were simultaneously benefiting from the die坼back of the invader. Our results show drought negatively impacted both native and invasive plants and this impact was stronger on the invader, which experienced persistent declines two years after the end of the drought. However, by mitigating the effect of drought on invasive plants, nutrient addition potentially erased the advantage drought provided native plants over invasive plants under ambient nutrient conditions. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article
%U https://esajournals.onlinelibrary.wiley.com/doi/full/10.1002/ecy.2980