The chapter discusses the complex dynamics of terrestrial ecosystem carbon cycles and their interactions with climate, highlighting the potential for positive feedback loops in a warming world. Terrestrial ecosystems play a crucial role in global climate by absorbing and releasing greenhouse gases such as CO₂, methane, and nitrous oxide, and by influencing energy, water, and momentum exchanges between the atmosphere and the land surface. The carbon balance of ecosystems is influenced by photosynthesis and respiration, with significant contributions from both autotrophs and heterotrophs. Empirical evidence shows that these ecosystems respond to climate variations, particularly through the impacts of heat and drought on vegetation, leading to short-term carbon losses. However, long-term interactions between the carbon and climate systems are less well understood, and models often struggle to accurately predict these feedbacks. The chapter emphasizes the importance of considering multiple interacting factors, such as water availability, nitrogen availability, and extreme weather events, which can significantly alter ecosystem carbon dynamics. For example, changes in precipitation and temperature can affect primary productivity and respiration, leading to unexpected carbon release. Additionally, the chapter highlights the role of below-ground processes, such as microbial metabolism and permafrost thaw, which can trigger nonlinear positive feedback loops that enhance carbon release into the atmosphere. Despite the challenges, the authors suggest that combining long-term multifactorial experiments with ecosystem-level observations and advanced modeling can improve our understanding of these complex interactions. They conclude that while there are uncertainties, terrestrial ecosystems are likely to provide a positive, amplifying feedback to climate change, but the magnitude of this feedback remains uncertain.The chapter discusses the complex dynamics of terrestrial ecosystem carbon cycles and their interactions with climate, highlighting the potential for positive feedback loops in a warming world. Terrestrial ecosystems play a crucial role in global climate by absorbing and releasing greenhouse gases such as CO₂, methane, and nitrous oxide, and by influencing energy, water, and momentum exchanges between the atmosphere and the land surface. The carbon balance of ecosystems is influenced by photosynthesis and respiration, with significant contributions from both autotrophs and heterotrophs. Empirical evidence shows that these ecosystems respond to climate variations, particularly through the impacts of heat and drought on vegetation, leading to short-term carbon losses. However, long-term interactions between the carbon and climate systems are less well understood, and models often struggle to accurately predict these feedbacks. The chapter emphasizes the importance of considering multiple interacting factors, such as water availability, nitrogen availability, and extreme weather events, which can significantly alter ecosystem carbon dynamics. For example, changes in precipitation and temperature can affect primary productivity and respiration, leading to unexpected carbon release. Additionally, the chapter highlights the role of below-ground processes, such as microbial metabolism and permafrost thaw, which can trigger nonlinear positive feedback loops that enhance carbon release into the atmosphere. Despite the challenges, the authors suggest that combining long-term multifactorial experiments with ecosystem-level observations and advanced modeling can improve our understanding of these complex interactions. They conclude that while there are uncertainties, terrestrial ecosystems are likely to provide a positive, amplifying feedback to climate change, but the magnitude of this feedback remains uncertain.