Temperature acclimation of leaf respiration differs between marsh and mangrove vegetation in a coastal wetland ecotone

Abstract

Temperature acclimation of leaf respiration (R) is an important determinant of ecosystem responses to temperature and the magnitude of temperature‐CO2 feedbacks as climate warms. Yet, the extent to which temperature acclimation of R exhibits a common pattern across different growth conditions, ecosystems, and plant functional types remains unclear. Here, we measured the short‐term temperature response of R at six time points over a 10‐month period in two coastal wetland species (Avicennia germinans [C3 mangrove] and Spartina alterniflora [C4 marsh grass]) growing under ambient and experimentally warmed temperatures at two sites in a marsh–mangrove ecotone. Leaf nitrogen (N) was determined on a subsample of leaves to explore potential coupling of R and N. We hypothesized that both species would reduce R at 25°C (R25) and the short‐term temperature sensitivity of R (Q10) as air temperature (Tair) increased across seasons, but the decline would be stronger in Avicennia than in Spartina. For each species, we hypothesized that seasonal temperature acclimation of R would be equivalent in plants grown under ambient and warmed temperatures, demonstrating convergent acclimation. Surprisingly, Avicennia generally increased R25 with increasing growth temperature, although the Q10 declined as seasonal temperatures increased and did so consistently across sites and treatments. Weak temperature acclimation resulted in reduced homeostasis of R in Avicennia. Spartina reduced R25 and the Q10 as seasonal temperatures increased. In Spartina, seasonal temperature acclimation was largely consistent across sites and treatments resulting in greater respiratory homeostasis. We conclude that co‐occurring coastal wetland species may show contrasting patterns of respiratory temperature acclimation. Nonetheless, leaf N scaled positively with R25 in both species, highlighting the importance of leaf N in predicting respiratory capacity across a range of growth temperatures. The patterns of respiratory temperature acclimation shown here may improve the predictions of temperature controls of CO2 fluxes in coastal wetlands.

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

“…It has been hypothesized that C 4 species are less capable of thermal acclimation than C 3 species (Yamori et al, 2014). However, C 4 plants sometimes show equivalent acclimation responses to warming (Sturchio et al, 2021; Yamori et al, 2014). Our results are similar to those of Dwyer et al (2007) who found slight positive effects of warming on photosynthetic rates of three C 4 species.…”

Temperature optimum for marsh resilience and carbon accumulation revealed in a whole‐ecosystem warming experiment

“…This, and decreased net primary production observed during elevated regional summer temperatures (Noyce et al, 2019), indicates that moderate amounts of warming in the region are likely elevating temperatures closer to or above this metabolic optimum. Although some studies have indicated that marsh grasses can acclimate leaf respiration and photosynthetic capacity to increasing temperatures (Sturchio et al, 2021;Wang et al, 2020), the warmest treatment likely exceeds the metabolic temperature optimum during warm summer days leading to a reduction in marsh elevation, analogous to the hump-shaped relationships between temperature and productivity proposed for S. alterniflora more globally (Liu et al, 2016(Liu et al, , 2020Rogers et al, 2006;Więski & Pennings, 2014). Our observations of consistent treatment optima, where root production, elevation change, and carbon accumulation rates in two disparate plant communities were maximized at +1.7°C, suggest that the qualitative patterns are applicable beyond our particular study area, but that the exact temperature optimum may vary around +1.7°C (Figure 1c).…”

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

“…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 ].…”