Search for: All records

Abstract Carbon use efficiency (CUE) represents how efficient a plant is at translating carbon gains through gross primary productivity (GPP) into net primary productivity (NPP) after respiratory costs (R_a). CUE varies across space with climate and species composition, but how CUE will respond to climate change is largely unknown due to uncertainty inR_aat novel high temperatures. We use a plant physiological model validated against global CUE observations and LIDAR vegetation canopy height data and find that model‐predicted decreases in CUE are diagnostic of transitions from forests to shrubland at dry range edges. Under future climate scenarios, we show mean growing season CUE increases in core forested areas, but forest extent decreases at dry range edges, with substantial uncertainty in absolute CUE due to uncertainty inR_a. Our results highlight that future forest resilience is nuanced and controlled by multiple competing mechanisms. 

Abstract Plant litter decomposition is a central process in the carbon (C) cycle and sensitive to ongoing anthropogenic nitrogen (N) fertilisation. Previous syntheses evaluating the effect of N fertilisation on litter decomposition relied largely on models that define a constant rate of mass loss throughout decomposition, which may mask hypothesised shifts in the effect of N fertilisation on litter decomposition dynamics. In this meta‐analysis, we compared the performance of four empirical decomposition models and showed that N fertilisation consistently accelerates early‐stage but slows late‐stage decomposition when the model structure allows for flexibility in decomposition rates through time. Within a particular substrate, early‐stage N‐stimulation of decomposition was associated with reduced rates of late‐stage decay. Because the products of early‐ vs. late‐stage decomposition are stabilised in soils through distinct chemical and physical mechanisms, N‐induced changes in the litter decomposition process may influence the formation and cycling of soil C, the largest terrestrial C pool.