Title: How close are we to a predictive science of the biosphere?
Abstract: In just 20 years, the field of biosphere–atmosphere interactions has gone from a nascent discipline to a central area of modern climate change research. The development of terrestrial biosphere models that predict the responses of ecosystems to climate and increasing CO2 levels has highlighted several mechanisms by which changes in ecosystem composition and function might alter regional and global climate. However, results from empirical studies suggest that ecosystem responses can differ markedly from the predictions of terrestrial biosphere models. As I discuss here, the challenge now is to connect terrestrial biosphere models to empirical ecosystem measurements. Only by systematically evaluating the predictions of terrestrial biosphere models against suites of ecosystem observations and experiments measurements will a true predictive science of the biosphere be achieved. In just 20 years, the field of biosphere–atmosphere interactions has gone from a nascent discipline to a central area of modern climate change research. The development of terrestrial biosphere models that predict the responses of ecosystems to climate and increasing CO2 levels has highlighted several mechanisms by which changes in ecosystem composition and function might alter regional and global climate. However, results from empirical studies suggest that ecosystem responses can differ markedly from the predictions of terrestrial biosphere models. As I discuss here, the challenge now is to connect terrestrial biosphere models to empirical ecosystem measurements. Only by systematically evaluating the predictions of terrestrial biosphere models against suites of ecosystem observations and experiments measurements will a true predictive science of the biosphere be achieved. a global-scale model of atmospheric dynamics. a global-scale model of atmospheric dynamics coupled to a global-scale model of ocean dynamics. a DGVM that is bidirectionally coupled to an AOGCM. a terrestrial biosphere model, which in addition to calculating the fast timescale exchanges of CO2, water and energy between the land-surface and the atmosphere, integrates the carbon fluxes into long-term changes in above- and belowground ecosystem structure and composition. They also track the fate of dead plant material entering the soil, and thus yield predictions for the fluxes of CO2 to the atmosphere arising from the decomposition of plant material instrumented towers that provide nondestructive measurements of the net exchange of CO2, water vapor and other gases between an ecosystem and the atmosphere. The net exchange (vertical flux) is computed by instruments that measure simultaneously the three-dimensional motion of the wind and the concentration of the relevant gas above the top of the plant canopy. Fluxes are typically calculated at 30-min intervals or less, which are then summed to yield daily, monthly and annual estimates of carbon uptake and water loss. the sum of evaporation and transpiration. In terrestrial ecosystems, evaporation arises from the evaporation of moisture from the soil and from the evaporation of moisture on the surfaces of leaves in the canopy. Transpiration is the loss of water from plants, primarily by moisture lost through the stomata of the leaves. Water for transpiration is acquired by the plant's roots and transferred to the leaves by its vascular system. When converted into energy units, evapotranspiration represents the latent heat flux between the land surface and the atmosphere. a terrestrial biosphere model that is being forced with climatalogical observations rather than running interactively with an atmospheric model. a terrestrial biosphere model that is running interactively with an atmospheric model. a functional rather than taxonomic classification of plant diversity based on physiological and morphological attributes, and used to represent different forms of vegetation within terrestrial biosphere models. Common characteristics used to subdivide plant species into functional groups include: photosynthetic pathway (e.g. C3 versus C4), leaf type (e.g. coniferous versus broad-leaved), leaf phenology (e.g. deciduous versus evergreen) and structural type (e.g. trees versus shrubs versus herbaceous vegetation). vegetation that would exist in a region in the absence of humans. a measure of the ease with which water vapor leaves and carbon dioxide flux enters through the stomata of a plant. metrics of terrestrial biosphere model performance that assess their performance at large scales. Examples include regional- or global-scale estimates of CO2 and water vapor exchange between terrestrial ecosystems and the atmosphere.
Publication Year: 2006
Publication Date: 2006-05-13
Language: en
Type: review
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 158
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