Carbon dioxide increase: the implications at the ecosystem level<sup>*</sup>

Shugart, Herman H.; Emanuel, William R.

doi:10.1111/j.1365-3040.1985.tb01673.x

Cited by 32 publications

(15 citation statements)

References 21 publications

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“…This is due to negative feedback effects in the model, particularly increased competition for light in the long term, even in the absence of any reduced longevity. Besides confirming early findings (e.g., Shugart and Emanuel 1985), these results are in agreement with the picture emerging from longer-term CO 2 fertilization experiments, particularly those in closedcanopy stands, where an attenuation of the initial stimulation was observed after a few years (e.g., Oren et al 2001;Schäfer et al 2003;Norby et al 2004;Körner et al 2005). Hence, the present study serves as another example that strong effects at the individual plant level are often greatly attenuated (buffered) at higher levels of organization.…”

Section: Discussionsupporting

confidence: 92%

Will the CO2 fertilization effect in forests be offset by reduced tree longevity?

2010

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Experimental studies suggest that tree growth is stimulated in a greenhouse atmosphere, leading to faster carbon accumulation (i.e., a higher rate of gap filling). However, higher growth may be coupled with reduced longevity, thus leading to faster carbon release (i.e., a higher rate of gap creation). The net effect of these two counteracting processes is not known. We quantify this net effect on aboveground carbon stocks using a novel combination of data sets and modeling. Data on maximum growth rate and maximum longevity of 141 temperate tree species are used to derive a relationship between growth stimulation and changes in longevity. We employ this relationship to modify the respective parameter values of tree species in a forest succession model and study aboveground biomass in a factorial design of growth stimulation 9 reduced maximum longevity at multiple sites along a climate gradient from the cold to the dry treeline. The results show that (1) any growth stimulation at the tree level leads to a disproportionately small increase of stand biomass due to negative feedback effects, even in the absence of reduced longevity; (2) a reduction of tree longevity tends to offset the growth-related biomass increase; at the most likely value of reduced longevity, the net effect is very close to zero in most multi-and singlespecies simulations; and (3) when averaging the response across all sites to mimic a ''landscape-level'' response, the net effect is close to zero. Thus, it is important to consider ecophysiological responses with their linkage to demographic processes in forest trees if one wishes to avoid erroneous inference at the ecosystem level. We conclude that any CO 2 fertilization effect is quite likely to be offset by an associated reduction in the longevity of forest trees, thus strongly reducing the carbon mitigation potential of temperate forests.

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Section: Discussionsupporting

confidence: 92%

Will the CO2 fertilization effect in forests be offset by reduced tree longevity?

2010

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“…Forest gap models were not developed originally for studying the influence of a changing environment on forest dynamics (Botkin et al 1972), but their apparent success in many forest ecosystems of the world made it tempting to apply them also for projecting the future fate of forests under scenarios of global change (e.g., Shugart and Emanuel 1985, Solomon 1986, Pastor and Post 1988, Kienast 1991, Prentice et al 1991, O'Brien et al 1992. Undoubtedly, such applications are useful and timely.…”

Section: Introductionmentioning

confidence: 99%

A Simplified Forest Model to Study Species Composition Along Climate Gradients

Bugmann¹

1996

Ecology

280

276

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Forest models based on the gap dynamics hypothesis (gap models) have gained an important role in forest ecology and have grown rather complex in the last 20 yr. They have been applied extensively to study the impacts of climatic change on ecosystems although they originally were not built for this purpose. The objectives of this study were (1) to develop a new forest gap model, ForClim, that includes only a minimum number of ecological assumptions but robust parameterizations of the effects of climate on plant population dynamics; (2) to test the realism of ForClim as compared to its predecessor model, FORECE; and (3) to examine the behavior of FORECE and ForClim systematically along climate gradients in Europe. ForClim is composed of three modular submodels: ForClim—P for plant population dynamics, ForClim—S for soil carbon/nitrogen turnover, and ForClim—E for providing reliable parameterizations of the abiotic environment. For the core model, ForClim—P, it was found that only four factors are sufficient to model tree growth, another four factors are required to model tree establishment, and only two factors are required to model tree mortality. The behavior of ForClim was tested at a large number of sites in the European Alps. The model yields tree species compositions that conform to field data and are very similar to those of the predecessor model. Based on this evaluation alone, it would not be possible to favor one of the models over the other. The behavior of both models then was examined systematically in a parameter space spanned by the annual mean temperature and the annual precipitation sum. From this exercise it became evident that both the pattern of aboveground biomass and the realized niches of the dominating tree species are simulated realistically by ForClim. Extremely steep gradients are characteristic of FORECE, and many ecotones are simulated to occur in the wrong places in FORECE. Thus, some of the current forest gap models can be simplified without reducing the realism of their behavior, and models other than FORECE should be scrutinized in this respect as well. The present study also suggests that the evaluation of model behavior at scattered sites is insufficient to show their validity for simulating forest dynamics along climate gradients. Further rigorous model comparisons and validation studies are required to increase the reliability of this promising class of models.

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“…The technical difficulties and costs of scaling for such , studies are staggering (Dahlman, 1984: Shugart andEmanuel, 1985).…”

Section: Jmentioning

confidence: 99%

“…The assumption allowed the model to run with differential species responses, unlike the simplifying assumptions of equal species responses made in previous modelling attempts (Botkin et al, 1973;Shugart and Emanuel, 1985). Wright (1974) examined the effects of elevated CO 2 concentrations on photosynthesis of several competing San Bernardino mountain species.…”

Section: Subroutine Nhance Is Calledmentioning

confidence: 99%

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Effects of long-term elevated atmospheric CO{sub 2} concentrations on Pinus ponderosa

Surano¹,

Kercher

1993

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Carbon dioxide increase: the implications at the ecosystem level^*

Cited by 32 publications

References 21 publications

Will the CO2 fertilization effect in forests be offset by reduced tree longevity?

Will the CO2 fertilization effect in forests be offset by reduced tree longevity?

A Simplified Forest Model to Study Species Composition Along Climate Gradients

Effects of long-term elevated atmospheric CO{sub 2} concentrations on Pinus ponderosa

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Carbon dioxide increase: the implications at the ecosystem level*

Cited by 32 publications

References 21 publications

Will the CO2 fertilization effect in forests be offset by reduced tree longevity?

Will the CO2 fertilization effect in forests be offset by reduced tree longevity?

A Simplified Forest Model to Study Species Composition Along Climate Gradients

Effects of long-term elevated atmospheric CO{sub 2} concentrations on Pinus ponderosa

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Product

Resources

About

Carbon dioxide increase: the implications at the ecosystem level^*