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Invasive forb benefits from water savings by native plants and carbon fertilization under elevated CO2 and warming

Blumenthal, Dana M., Resco, Victor, Morgan, Jack A., Williams, David G., LeCain, Daniel R., Hardy, Erik M., Pendall, Elise, Bladyka, Emma
New phytologist 2013 v.200 no.4 pp. 1156
Linaria dalmatica, Pascopyrum smithii, biomass, carbon, carbon dioxide, forbs, free air carbon dioxide enrichment, indigenous species, invasive species, photosynthesis, plant communities, plant growth, prairies, prediction, seed productivity, soil water, soil water deficit, stomatal conductance, survival rate, temperature, vegetative propagation
As global changes reshuffle plant communities, invasive plants may benefit. Unfortunately, potential interactions among global changes and limited mechanistic understanding make it difficult to predict invasions in future environments. Here we show that elevated CO2 can strongly promote invasion by increasing availability of two resources, carbon (C) and water, both with and without warming. Four years after transplanting the invasive forb Linaria dalmatica into mixed-grass prairie, Free Air CO2 Enrichment (FACE) had increased L. dalmatica biomass 13-fold, seed production 32-fold, and clonal expansion 7-fold. Warming had no net effect on L. dalmatica biomass, reducing survival, but also increasing growth. Elevated CO2 decreased stomatal conductance in the dominant native grass, Pascopyrum smithii, contributing to an increase in soil water, but increased stomatal conductance in L. dalmatica. Elevated CO2 also increased photosynthetic CO2 assimilation more in L. dalmatica (87%) than in P. smithii (23%), as a result of both increased soil water and increased CO2 when controlling for soil water. These results suggest that rapid growth and less conservative water use may allow invasive species to take advantage of both C-fertilization and water saved by native species under elevated CO2. Water-limited ecosystems may therefore be particularly vulnerable to invasion under future climates.