Optimal Function Explains Forest Responses to Global Change

Dewar, Roderick C.; Franklin, Oskar; Mäkelä, Annikki; McMurtrie, Ross E.; Valentine, Harry T.

doi:10.1525/bio.2009.59.2.6

Cited by 95 publications

(108 citation statements)

References 58 publications

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“…Consistent with our analysis that both leaf-and canopy-level characteristics are important determinants of NPP, the model predicts an optimal balance with respect to foliar [N], stomatal conductance, and stand leaf area index (LAI) at which NPP is maximized; the optimum point, which is determined independently for each year, varies as resources change over time. With water and N availability prescribed at levels determined for 1998-2002, the model predicts maximum NPP to occur at a foliar [N] of 16.6 mg·g −1 in aCO 2 and 14.4 mg·g −1 in eCO 2 (24), which compares well with regression analysis of our data (Fig. 3B).…”

Section: Discussionsupporting

confidence: 85%

“…3B). NPP is maximized at a lower value of [N] in eCO 2 because of greater photosynthetic N-use efficiency, which permits a reduction in the costs associated with foliar N (24). Also consistent with the optimization model, the slope of the NPP-[N] relationship was steeper in eCO 2 than in aCO 2 (Fig.…”

Section: Discussionsupporting

confidence: 71%

“…Our analysis of the relationship between NPP and foliar [N] is guided by the predictions of a simple model of the sweetgum stand's C-N-water economy (9,24). Consistent with our analysis that both leaf-and canopy-level characteristics are important determinants of NPP, the model predicts an optimal balance with respect to foliar [N], stomatal conductance, and stand leaf area index (LAI) at which NPP is maximized; the optimum point, which is determined independently for each year, varies as resources change over time.…”

Section: Discussionmentioning

confidence: 99%

“…These stand-level observations and models have mechanistic support from measurements of leaf-level photosynthesis. The simple optimization model can explain the N constraint on CO 2 enhancement from plant physiological considerations (9,24), specifically the reduced stimulation of photosynthesis by eCO 2 as foliar [N] declines. The loss of photosynthetic response to eCO 2 was a proximate cause of the decline in NPP response.…”

Section: Discussionmentioning

confidence: 99%

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CO ₂ enhancement of forest productivity constrained by limited nitrogen availability

Norby

Warren

Iversen

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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859

572

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Stimulation of terrestrial plant production by rising CO 2 concentration is projected to reduce the airborne fraction of anthropogenic CO 2 emissions. Coupled climate-carbon cycle models are sensitive to this negative feedback on atmospheric CO 2 , but model projections are uncertain because of the expectation that feedbacks through the nitrogen (N) cycle will reduce this so-called CO 2 fertilization effect. We assessed whether N limitation caused a reduced stimulation of net primary productivity (NPP) by elevated atmospheric CO 2 concentration over 11 y in a free-air CO 2 enrichment (FACE) experiment in a deciduous Liquidambar styraciflua (sweetgum) forest stand in Tennessee. During the first 6 y of the experiment, NPP was significantly enhanced in forest plots exposed to 550 ppm CO 2 compared with NPP in plots in current ambient CO 2 , and this was a consistent and sustained response. However, the enhancement of NPP under elevated CO 2 declined from 24% in 2001-2003 to 9% in 2008. Global analyses that assume a sustained CO 2 fertilization effect are no longer supported by this FACE experiment. N budget analysis supports the premise that N availability was limiting to tree growth and declining over time -an expected consequence of stand development, which was exacerbated by elevated CO 2 . Leaf-and stand-level observations provide mechanistic evidence that declining N availability constrained the tree response to elevated CO 2 ; these observations are consistent with stand-level model projections. This FACE experiment provides strong rationale and process understanding for incorporating N limitation and N feedback effects in ecosystem and global models used in climate change assessments.CO 2 fertilization | free air CO 2 enrichment | global carbon cycle | sweetgum | coupled climate-carbon cycle models P olicy decisions to mitigate climate change require dependable predictions of the forcings and feedbacks between the terrestrial biosphere and the climate (1). Currently, climate models that are coupled to terrestrial and oceanic carbon (C)-cycle models simulate a positive feedback to climate change such that the airborne fraction of anthropogenic CO 2 emissions increases with, and amplifies, climatic warming (1). However, the uncertainty in these projections is high, largely because of uncertainty in the offsetting negative feedback that may occur if stimulation of terrestrial plant production by rising CO 2 concentration increases land C storage and thereby reduces the airborne fraction of anthropogenic CO 2 emissions. Coupled climate-C-cycle models, including those used in the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) (2), are sensitive to this negative feedback on atmospheric CO 2 (3). For example, dynamic global vegetation models (4) simulate an increased terrestrial C sink resulting from the physiological responses of plants to elevated atmospheric CO 2 concentration (eCO 2 ), and when coupled to climate models, inclusion of the CO 2 fertilization effect slows the increase in...

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Section: Discussionsupporting

confidence: 85%

Section: Discussionsupporting

confidence: 71%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

CO ₂ enhancement of forest productivity constrained by limited nitrogen availability

Norby

Warren

Iversen

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

859

572

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show abstract

“…In the first model version, CLASS SimOpt it is assumed that plant traits are optimal simply when whole stand performance is maximized, meaning that the plants individual performance is optimized as long as it is in a monoculture without any invading strategies. The theory is based on the ecological concept that natural selection may have produced plants with optimal traits that maximize whole stand net photosynthesis independent of competition between plants [Dewar et al, 2009]. We have chosen to optimize the LAI first because leaf area is an important trait driving photosynthesis, growth, and competitive ability of plants and, second, because LAI is a key vegetation parameter in many atmospheric models [Van den Hurk et al, 2003] and is generally thought to play an important role in vegetation-atmosphere feedbacks [Bounoua et al, 2000] due to its influence on the radiation balance and evapotranspiration.…”

Section: Methodsmentioning

confidence: 99%

Understanding the impact of plant competition on the coupling between vegetation and the atmosphere

et al. 2015

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Competition between plants for resources is an important selective force. As a result competition through natural selection determines vegetation functioning and associated atmospheric interactions. Our aim was to investigate how the coupling between vegetation and atmosphere is influenced by plant competition. Though included in some coupled vegetation-atmosphere models, little attention has been paid to systematically study the impact of plant competition in determining the evolution of surface and atmospheric variables. We used a coupled vegetation-atmosphere model and included a new representation of plant competition. We compared the model results with diurnal data from Ameriflux Bondville site over a growing season. Including competition improved LAI (Leaf Area Index) and net ecosystem exchange of CO 2 (NEE) predictions; if competition was not considered, there were strong deviations from observations. Remarkably, competition increased LAI while it reduced whole stand photosynthesis, resulting in a less negative NEE. Finally, independent of competition, latent heat flux, surface temperature, specific humidity, and atmospheric CO 2 are well reproduced by the model. Only the sensible heat flux was overestimated, mainly due to the imbalance in the surface energy balance that can lead to lower measured sensible heat fluxes. Sensitivity analysis showed that the importance of plant competition on model outcomes increases with more nitrogen and water availability and may differ between soil types. We thus quantified the potential effect of plant competition in a coupled vegetation-atmosphere system and showed that it strongly influences this system, and therefore, we propose that competition should be considered in more vegetation-atmosphere models.

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Climate Change and Stomatal Physiology

Matthews

Lawson

2019

Annual Plant Reviews Online

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Stomata control the uptake of CO 2 into the leaf along with water loss through transpiration and are critical for maintaining plant water status and leaf temperature. The predicted changes in future climate conditions; including atmospheric [CO 2 ], temperature, and water availability will greatly influence stomatal development and functional response. As stomata account for 95% of terrestrial gaseous fluxes of water and carbon, their behaviour has major consequences for global hydrological and carbon cycles, with implications for precipitation patterns, land run‐off and drought events. Furthermore, as water demand for agricultural practices is predicted to increase, crop production for sustainable food security will require improvements in plant water use efficiency, to which stomatal conductance and dynamic responses to environmental conditions are key components. Stomatal response is often the combination of several environmental and internal stimuli, and is, therefore, difficult to predict across ecosystem types. Here, we review stomatal response to key environmental factors at the leaf and ecosystem levels, and highlight the influence of changes in stomatal anatomical and functional behaviour on earth systems and ecosystem function in the face of climate change.

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Optimal Function Explains Forest Responses to Global Change

Cited by 95 publications

References 58 publications

CO ₂ enhancement of forest productivity constrained by limited nitrogen availability

CO ₂ enhancement of forest productivity constrained by limited nitrogen availability

Understanding the impact of plant competition on the coupling between vegetation and the atmosphere

Climate Change and Stomatal Physiology

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Optimal Function Explains Forest Responses to Global Change

Cited by 95 publications

References 58 publications

CO 2 enhancement of forest productivity constrained by limited nitrogen availability

CO 2 enhancement of forest productivity constrained by limited nitrogen availability

Understanding the impact of plant competition on the coupling between vegetation and the atmosphere

Climate Change and Stomatal Physiology

Contact Info

Product

Resources

About

CO ₂ enhancement of forest productivity constrained by limited nitrogen availability

CO ₂ enhancement of forest productivity constrained by limited nitrogen availability