Elevated CO₂ does not offset greater water stress predicted under climate change for native and exotic riparian plants

Abstract

SummaryIn semiarid western North American riparian ecosystems, increased drought and lower streamflows under climate change may reduce plant growth and recruitment, and favor drought-tolerant exotic species over mesic native species. We tested whether elevated atmospheric CO 2 might ameliorate these effects by improving plant water-use efficiency.We examined the effects of CO 2 and water availability on seedlings of two native (Populus deltoides spp. monilifera, Salix exigua) and three exotic (Elaeagnus angustifolia, Tamarix spp., Ulmus pumila) western North American riparian species in a CO 2 -controlled glasshouse, using 1-m-deep pots with different water-table decline rates.Low water availability reduced seedling biomass by 70-97%, and hindered the native species more than the exotics. Elevated CO 2 increased biomass by 15%, with similar effects on natives and exotics. Elevated CO 2 increased intrinsic water-use efficiency (D 13 C leaf ), but did not increase biomass more in drier treatments than wetter treatments. The moderate positive effects of elevated CO 2 on riparian seedlings are unlikely to counteract the large negative effects of increased aridity projected under climate change. Our results suggest that increased aridity will reduce riparian seedling growth despite elevated CO 2 , and will reduce growth more for native Salix and Populus than for drought-tolerant exotic species.

Atmospheric CO2 enrichment and drought stress modify root exudation of barley

“…It has been reported that plants grown at eCO 2 may in part compensate the negative effects of drought due to increased water‐use efficiency. Although this has been shown in some studies (Chaudhuri et al ., ; Chaves & Pereira, ; Morgan et al ., ; Manderscheid et al ., ), these interactions were absent in many other studies (Mousseau & Enoch, ; Grünzweig & Körner, ; Derner et al ., ; Vaz et al ., ; Medeiros & Ward, ; Perry et al ., ). In our experiment, CO 2 fertilization compensated for the negative effect of drought on grain yield and water‐use efficiency at maturity, especially in GP (Schmid et al ., ).…”

Elevated [CO2] does not ameliorate the negative effects of elevated temperature on drought‐induced mortality in Eucalyptus radiata seedlings

“…It is well established that elevated [CO2] leads to reduced stomatal conductance (gs) (Medlyn et al 2001;Wullschleger et al 2002) and could therefore theoretically reduce plant water loss and delay drought-induced mortality by allowing plants to maintain more favourable water status during drought. However, existing studies suggest that plant responses to elevated [CO2] and drought stress are highly variable (Atwell et al 2007;Domec et al 2010;Wertin et al 2010Wertin et al ,2012Ayub et al 2011;Duursma et al 2011;Warren et al 2011;Zeppel et al 2012;Franks et al 2013;Lewis et al 2013;Perry et al 2013). For example,in some studies,elevated [CO2] can partially moderate the impact of drought stress by increasing photosynthesis (Wertin et al 2010;Lewis et al 2013) and carbohydrate reserves (Niinemets 2010;Tissue & Lewis 2010;Ayub et al 2011), thereby providing increased availability of carbon for growth and metabolic activity during mild or moderate drought stress.…”

Increasing atmospheric [CO2] from glacial to future concentrations affects drought tolerance via impacts on leaves, xylem and their integrated function

“…We provide evidence that growth under low‐[CO 2 ] conditions could have increased the drought tolerance of some C 3 plants during glacial times compared with the present. Our work also provides mechanistic support for studies indicating that water availability will remain an important factor limiting the productivity of C 3 plants, even as [CO 2 ] increases (Linares et al ., ; Vaz et al ., ; Perry et al ., ). Furthermore, we show that increased productivity at elevated [CO 2 ] may only occur under conditions where higher water use can be accommodated.…”