Warming impacts on photosynthetic processes in dominant plant species in a subtropical forest

Abstract

Climate warming could shift some subtropical regions to a tropical climate in the next 30 years. Yet, climate warming impacts on subtropical species and ecosystems remain unclear. We conducted a passive warming experiment in a subtropical forest in Florida, USA, to determine warming impacts on four species differing in their climatic distribution, growth form, and functional type: Serenoa repens (palm), Andropogon glomeratus (C4 grass), Pinus palustris (needled evergreen tree), and Quercus laevis (broadleaved deciduous tree). We hypothesized that warming would have neutral‐positive effects on photosynthetic processes in monocot species with warmer climatic distributions or adaptations to warmer temperatures, but negative effects on photosynthesis in tree species. We also hypothesized that periods of low soil moisture would alter photosynthetic responses to warming. In both monocot species, warming had no significant effect on net photosynthesis (A) or stomatal conductance (gs) measured at prevailing temperatures, or photosynthetic capacity measured at a common temperature. In P. palustris, warming reduced A (−15%) and gs (−28%), and caused small reductions in Rubisco carboxylation and RuBP regeneration. Warming had little effect on photosynthetic processes in Q. laevis. Interestingly, A. glomeratus showed little sensitivity to reduced soil moisture, and all C3 species reduced A and gs as soil moisture declined and did so consistently across temperature treatments. In subtropical forests of the southeastern US, we conclude that climate warming may have neutral or slightly positive effects on the performance of grasses and broadleaved species but negative effects on P. palustris seedlings, foreshadowing possible changes in community and ecosystem properties.

Coordination of leaf functional traits under climatic warming in an arid ecosystem

“…A high temperature above the optimum can result in a decline in A area, as reported by a body of previous results and the present study (e.g., [ 14 , 42 , 58 ]; Tables 1 and 2 ). However, the function of PSII, using both F v ’/F m ’ and Φ PSII as the proxies [ 65 ], remained almost stable (e.g., [ 14 , 66 , 67 ]), and a slight promotion might even occur (Tables 1 and 2 ).…”

“…C 4 plants often dominate warm environments and have been suggested to have a high resistance to high temperature relative to C 3 plants (e.g., [ 61 , 62 ]). Positive responses of C 4 species to warming have been observed in many studies (e.g., [ 58 , 61 ]). However, both C 3 and C 4 plants have been found to have similar photosynthetic responses to warming [ 63 , 64 ], and inhibition of C 4 plants may appear with a high temperature or a combination of warming and water deficit [ 42 , 58 ].…”

“…Positive responses of C 4 species to warming have been observed in many studies (e.g., [ 58 , 61 ]). However, both C 3 and C 4 plants have been found to have similar photosynthetic responses to warming [ 63 , 64 ], and inhibition of C 4 plants may appear with a high temperature or a combination of warming and water deficit [ 42 , 58 ]. Thus, a concurrence of warming and drought jointly presenting severe abiotic stress could largely constrain the photosynthetic performance of either C 3 or C 4 species, especially in a xeric area [ 42 , 58 ].…”

“…However, both C 3 and C 4 plants have been found to have similar photosynthetic responses to warming [ 63 , 64 ], and inhibition of C 4 plants may appear with a high temperature or a combination of warming and water deficit [ 42 , 58 ]. Thus, a concurrence of warming and drought jointly presenting severe abiotic stress could largely constrain the photosynthetic performance of either C 3 or C 4 species, especially in a xeric area [ 42 , 58 ]. This was completely confirmed by the present warming experiment, where warming-induced drought stress occurred (Table 2 ; [ 5 ]).…”

The times, they are a‐changin'

“…Plants growing on the limit of their distribution will likely suffer first from a change in climate, and the southern limit might become too hot and dry for the European oak. The article of Aspinwall et al (2022) in the current issue of Physiologia Plantarum, aims to investigate the effect of a rise in ambient temperature on four plant species, common and dominant in a subtropical forest (FL, USA). The authors found that two monocot species distributed in warmer climatic regions, a palm, and a grass, were able to handle the rise in temperature.…”