Rising atmospheric concentrations of CO 2 ( C a ) can reduce stomatal conductance and transpiration rate in trees, but the magnitude of this effect varies considerably among experiments. The theory of optimal stomatal behaviour predicts that the ratio of photosynthesis to transpiration (instantaneous transpiration efficiency, ITE ) should increase in proportion to C a . We hypothesized that plants regulate stomatal conductance...

Despite the importance of nitrogen (N) limitation of forest carbon (C) sequestration at rising atmospheric CO 2 concentration, the mechanisms responsible are not well understood. To elucidate the interactive effects of elevated CO 2 (eCO 2 ) and soil N availability on forest productivity and C allocation, we hypothesized that (1) trees maximize fitness by allocating N and C to maximize their net growth and (2) that N uptake is...

An improved understanding of the response of forest ecosystems to elevated levels of CO 2 in the atmosphere is crucial because atmospheric CO 2 concentration continues to increase at an accelerating rate and forests are an important sink in the global carbon cycle. Several CO 2 ‐enrichment experiments have now been running for more than 10 years, with highly variable short‐term results after the first decade. Responses to risi...

In a forest ecosystem at steady state, net carbon (C) assimilation by plants and C loss through soil and litter decomposition by heterotrophic organisms are balanced. However, a perturbation to the system, such as increased mean soil temperature, will lead to faster decay, enhancing CO 2 release from decomposers, and thus upsetting the balance. Recent in situ experiments have indicated that the stimulation of soil respiration...

In this study, we simulated pasture to Pinus radiata land‐use change with the G eneric D ecomposition A nd Y ield (G'DAY) ecosystem model to examine mechanisms responsible for the change in soil carbon (C) under pine. We parameterized the model for paired sites in New Zealand. Our simulations successfully reproduced empirical trends in ecosystem productivity and soil inorganic nitrogen (N), and modeled an increase in soil C an...

Soil carbon is a large component of the global carbon cycle and its management can significantly affect the atmospheric CO 2 concentration. An important management issue is the extent of soil carbon (C) release when forest is converted to agricultural land. We reviewed the literature to assess changes in soil C upon conversion of forests to agricultural land. Analyses are confounded by changes in soil bulk density upon land‐us...

Summary Based on short‐term experiments, many plant growth models – including those used in global change research – assume that an increase in temperature stimulates plant respiration ( R ) more than photosynthesis ( P ), leading to an increase in the R / P ratio. Longer‐term experiments, however, have demonstrated that R / P is relatively insensitive to growth temperature. We show that both types of temperature response may...