Photosynthetic responses to a climate‐warming manipulation for contrasting meadow species in the Rocky Mountains, Colorado, USA

Abstract

Summary 1.Microclimate was measured and photosynthetic responses to a climate warming manipulation were compared for the evergreen shrub Artemisia tridentata and the herbaceous forb Erigeron speciosus in the Rocky Mountains, Colorado, USA. 2. Soil was warmer and drier under infra-red heaters compared with control plots. 3. Midday xylem pressure potential did not differ for A. tridentata on heated vs control plots but was lower for E. speciosus on heated plots compared with controls. Leaf temperatures did not vary for the two species on heated or control plots. 4. There were no significant treatment or species differences in the diurnal patterns of CO 2 assimilation or stomatal conductance to water vapour. Also, there were no differences in responses to leaf temperature. 5. The quantum yield for CO 2 assimilation over a range of PPFD was lower for plants on heated plots. There was a marked difference between species in the pattern of stomatal conductance to water vapour over a range of PPFD, but no differences as a result of the heating treatment. 6. The quantum efficiency of PSII electron transport was significantly affected by heating. Non-radiative energy dissipation was greater for A. tridentata compared with E. speciosus . There was recovery of F V / F M for A. tridentata but not for E. speciosus . 7. Heating appears to affect plants via changes in soil water content rather than by increasing leaf temperature. The deciduous species E. speciosus appears to undergo some permanent closure of PSII on heated plots, in contrast to the evergreen shrub A. tridentata . Such differences may help explain the increase in above-ground biomass accumulation in response to heating for shrubs, compared with the decrease observed for deciduous herbaceous species.

Different growth and physiological responses to experimental warming of two dominant plant species Elymus nutans and Potentilla anserina in an alpine meadow of the eastern Tibetan Plateau

“…Indeed, our initial results from a warming experiment in the eastern Tibetan Plateau indicated an increase in soil temperature and a decrease in soil moisture content for plots in OTC, and experimental warming increased the cover degree and biomass accumulation in the grasses, but reduced them in the forbs (Shi et al 2008). Similar responses of different plant groups to a warming experiment have also been demonstrated in the Tibetan Plateau (Zhang andWelker ---1996, Zhou et al 2000) and other cold regions (Harte and Shaw 1995, Arft et al 1999, Henry and Molau 1997, Loik et al 2000.…”

“…The positive effects of warming on gas exchange of some plant species had been reported by other studies (Chapin and Shaver 1996, Bergh and Linder 1999, Loik et al 2004. However, the gas exchange of P. anserina significantly decreased in the warming treatment and this could be attributed to the effect of warming on soil drying, which had been reported by Loik et al (2000). Giorio et al (1999) demonstrated that the decrease of gas exchange under the condition of water stress owed to the limitation of stomata or photosynthetic organelles.…”

“…The responses of gas exchange to experimental warming have been shown to vary largely for different species (Loik et al 2000, He and Dong 2003, Xiao et al 2003. In this study, the E, g s , P max , R D , and AQY of E. nutans significantly increased and the LCP of this species significantly decreased in the warming treatment.…”

“…Among physiological parameters, light-saturated photosynthetic rate, apparent quantum yield of the photochemical efficiency of photosystem II and activities of antioxidant enzymes are temperature-dependent and the most sensitive parameters in response to global warming (Atkin et al 2005, Xiong et al 2000, Jarvis et al 2004, Xin and Browse 2000. Such acclimation may vary for functional groups with different evolutionary backgrounds and survival strategies (Loik et al 2000). In this regard, the changes in aboveground biomass accumulation exhibited by grasses and forbs exposed to a warming manipulation in the eastern Tibetan Plateau (Shi et al 2008) lacks a mechanistic explanation.…”

Efecto del aumento de la temperatura en la fotosíntesis de una especie alto-andina en dos altitudes

“…Loik & Redar 2003, Loik et al 2004, Sierra-Almeida et al 2009). Por ejemplo, Loik et al (2000) encontraron que la conductancia estomática y la tasa de fotosíntesis de Erigeron speciosus y Artemisia tridentata disminuyeron con el aumento de la temperatura, el que a su vez produjo una mayor desecación del suelo.…”