• Energy Research

Enhancing the terrestrial ecosystem carbon sink (referred to as terrestrial C sink) is an important way to slow down the continuous increase in atmospheric carbon dioxide (CO2) concentration and to achieve carbon neutrality target. To better understand the characteristics of terrestrial C sinks and their contribution to carbon neutrality, this review summarizes major progress in terrestrial C budget researches during the past decades, clarifies spatial patterns and drivers of terrestrial C sources and sinks in China and around the world, and examines the role of terrestrial C sinks in achieving carbon neutrality target. According to recent studies, the global terrestrial C sink has been increasing from a source of (-0.2±0.9) Pg C yr-1 (1 Pg=1015 g) in the 1960s to a sink of (1.9±1.1) Pg C yr-1 in the 2010s. By synthesizing the published data, we estimate terrestrial C sink of 0.20-0.25 Pg C yr-1 in China during the past decades, and predict it to be 0.15-0.52 Pg C yr-1 by 2060. The terrestrial C sinks are mainly located in the mid- and high latitudes of the Northern Hemisphere, while tropical regions act as a weak C sink or source. The C balance differs much among ecosystem types: forest is the major C sink; shrubland, wetland and farmland soil act as C sinks; and whether the grassland functions as C sink or source remains unclear. Desert might be a C sink, but the magnitude and the associated mechanisms are still controversial. Elevated atmospheric CO2 concentration, nitrogen deposition, climate change, and land cover change are the main drivers of terrestrial C sinks, while other factors such as fires and aerosols would also affect ecosystem C balance. The driving factors of terrestrial C sink differ among regions. Elevated CO2 concentration and climate change are major drivers of the C sinks in North America and Europe, while afforestation and ecological restoration are additionally important forcing factors of terrestrial C sinks in China. For future studies, we recommend the necessity for intensive and long term ecosystem C monitoring over broad geographic scale to improve terrestrial biosphere models for accurately evaluating terrestrial C budget and its dynamics under various climate change and policy scenarios.

Enhancing the terrestrial ecosystem carbon sink (referred to as terrestrial C sink) is an important way to slow down the continuous increase in atmospheric carbon dioxide (CO2) concentration and to achieve carbon neutrality target. To better understand the characteristics of terrestrial C sinks and their contribution to carbon neutrality, this review summarizes major progress in terrestrial C budget researches during the past decades, clarifies spatial patterns and drivers of terrestrial C sources and sinks in China and around the world, and examines the role of terrestrial C sinks in achieving carbon neutrality target. According to recent studies, the global terrestrial C sink has been increasing from a source of (-0.2±0.9) Pg C yr-1 (1 Pg=1015 g) in the 1960s to a sink of (1.9±1.1) Pg C yr-1 in the 2010s. By synthesizing the published data, we estimate terrestrial C sink of 0.20-0.25 Pg C yr-1 in China during the past decades, and predict it to be 0.15-0.52 Pg C yr-1 by 2060. The terrestrial C sinks are mainly located in the mid- and high latitudes of the Northern Hemisphere, while tropical regions act as a weak C sink or source. The C balance differs much among ecosystem types: forest is the major C sink; shrubland, wetland and farmland soil act as C sinks; and whether the grassland functions as C sink or source remains unclear. Desert might be a C sink, but the magnitude and the associated mechanisms are still controversial. Elevated atmospheric CO2 concentration, nitrogen deposition, climate change, and land cover change are the main drivers of terrestrial C sinks, while other factors such as fires and aerosols would also affect ecosystem C balance. The driving factors of terrestrial C sink differ among regions. Elevated CO2 concentration and climate change are major drivers of the C sinks in North America and Europe, while afforestation and ecological restoration are additionally important forcing factors of terrestrial C sinks in China. For future studies, we recommend the necessity for intensive and long term ecosystem C monitoring over broad geographic scale to improve terrestrial biosphere models for accurately evaluating terrestrial C budget and its dynamics under various climate change and policy scenarios.

AbstractThe photosynthetic rate is considered to be affected by individual biomass and limited by nutrients. Metabolic scaling models are often utilized to predict photosynthetic rates based on plant size and other factors, such as temperature and plant nutrient composition. However, the intrinsic regulatory mechanisms of the combined factors that affect the photosynthetic rates of living organisms are subject to debate. Here, we present a model developed from the metabolic scaling model, the Michaelis‐Menten equation and elemental stoichiometric models to precisely predict the relationship between plant photosynthetic rate and biomass. The developed model was verified against data for small woody and nonwoody plants, and in comparison with the typical metabolic scaling model, this model was shown to be more capable of explaining the photosynthesis‐biomass relationship. Moreover, the results showed that the combined factors affected photosynthesis via the regulatory effect of nutrients on photosynthesis‐biomass allometry. We highlight that nutrients have direct effects on the allocation of plant biomass and photosynthetic investment under stable and balanced growth states.

AbstractThe photosynthetic rate is considered to be affected by individual biomass and limited by nutrients. Metabolic scaling models are often utilized to predict photosynthetic rates based on plant size and other factors, such as temperature and plant nutrient composition. However, the intrinsic regulatory mechanisms of the combined factors that affect the photosynthetic rates of living organisms are subject to debate. Here, we present a model developed from the metabolic scaling model, the Michaelis‐Menten equation and elemental stoichiometric models to precisely predict the relationship between plant photosynthetic rate and biomass. The developed model was verified against data for small woody and nonwoody plants, and in comparison with the typical metabolic scaling model, this model was shown to be more capable of explaining the photosynthesis‐biomass relationship. Moreover, the results showed that the combined factors affected photosynthesis via the regulatory effect of nutrients on photosynthesis‐biomass allometry. We highlight that nutrients have direct effects on the allocation of plant biomass and photosynthetic investment under stable and balanced growth states.