Air temperature optima of vegetation productivity across global biomes

Abstract

The global distribution of the optimum air temperature for ecosystem-level gross primary productivity (Topteco) is poorly understood, despite its importance for ecosystem carbon uptake under future warming. We provide empirical evidence for the existence of such an optimum, using measurements of in situ eddy covariance and satellite-derived proxies, and report its global distribution. Topteco is consistently lower than the physiological optimum temperature of leaf-level photosynthetic capacity, which typically exceeds 30 °C. The global average Topteco is estimated to be 23±6 ºC, with warmer regions having higher Topteco values than colder regions. In tropical forests, particularly, Topteco is close to growing-season air temperature and is projected to fall below it under all scenarios of future climate, suggesting a limited safe operating space for these ecosystems under future warming.

Leaf Area Rather Than Photosynthetic Rate Determines the Response of Ecosystem Productivity to Experimental Warming in an Alpine Steppe

“…Warming can enhance plant photosynthesis when leaf temperature is lower than this optimal temperature, while plant photosynthesis will be constrained after the optimal temperature (Luo, 2007). In this study, the extremely high air temperature inside the OTCs (maximum: 37°C; Figure S5a) might exceed the optimal temperature of plant photosynthesis (Huang et al, 2019) and subsequently constrained plant photosynthesis (Klein et al, 2004;Wang et al, 2012). However, grass could provide shading for forb due to their taller individuals (Table S4) and thus resulted in lower heat stress for forb growth ( Figure S9a).…”

Model parameterization to represent processes at unresolved scales and changing properties of evolving systems

“…Shifts of the optimum temperature of net ecosystem exchange are mostly due to temperature acclimation of GPP. The optimum temperature for ecosystem‐level GPP, however, is consistently lower than the physiological optimal temperature of leaf‐level photosynthesis (Huang et al, ).…”

Estimating site-specific optimum air temperature and assessing its effect on the photosynthesis of grasslands in mid- to high-latitudes

“…The relationship between air temperature and photosynthesis or gross primary production (GPP) of vegetation at the local, regional, and global scales has been studied over many decades (Williams et al 2014;Huang et al 2019). Global warming and climatic extremes (e.g.…”

“…Because of the limitation of electric transport and Rubisco activity, plants tend to have low photosynthesis at cool temperatures, and increase to a maximum rate at optimal temperatures in the 20°C-30°C range and then decrease again at very high temperatures (Fitter and Hay 2012). This optimum temperature (T opt ) response has been described across a wide range of plant species (Kirschbaum and Farquhar 1984;Battaglia et al 1996;Fitter and Hay 2012), and ecosystem biomes (Huang et al 2019). In most satellite-based LUE GPP models, T s has been defined as a function of T opt , maximum temperature, and minimum temperature for vegetation growth.…”

“…Several studies have reported that the use of biome-specific parameters introduced an inaccurate derivation of ε and could be one of the potential error sources in GPP data product (Heinsch et al 2006;Sjöström et al 2013). Note that a vegetation biome often covers a very large geographical domain, and vegetation may adapt to its local climate over years and thus develop a sitespecific optimum air temperature (T opt−s ) (Huang et al 2019). There is a need to quantify the range of T opt−s parameter values and the difference between the T opt−s and T opt−b parameters.…”