Publication Abstracts

Wullschleger et al. 2001

Wullschleger, S.D., R.B. Jackson, W.S. Currie, A.D. Friend, Y. Luo, F. Mouillot, Y. Pan, and G. Shao, 2001: Below-ground processes in gap models for simulating forest response to global change. Climatic Change, 51, 449-473, doi:10.1023/A:1012570821241.

Gap models have a rich history of being used to simulate individual tree interactions that impact species diversity and patterns of forest succession. Questions arise, however, as to whether these same models can be used to study the response offorest structure and composition under a changing climate. In contrast to many process-based models, gap models have traditionally been based on rather descriptive representations of species-specific growth processes. Opportunities now exist to expand upon these simple empirical relationships with more mechanistic descriptions of growth, the response of growth to environmental variables, and competition among species for available light, water, and nutrient resources.In this paper, we focus on several areas of below-ground researchwith the potential to improve the utility of gap models for predicting forest composition in response to a changing climate.Specific areas for model improvement include (1) improved descriptions of the soil environment for seed germination andsubsequent seedling establishment, (2) multi-layer representations of soil water and nutrient availability, (3) moreaccurate information on biomass allocation to roots and rootdistribution within the soil profile, (4) improved treatment ofinter- and intra-specific competition for available soil resources, (5) increased consideration of spatial processes as related to land-surface hydrology, and (6) improved attention to above- and below-ground interactions. This list is meant tostimulate discussion and provide guidance for future field research and model development.As an example of how increased attention to below-ground processes could help address intra-specific competition for wateramong trees of differing size classes, the gap model LINKAGES was modified to include a sub-model of multi-layered soil hydrology. It was then used to examine the impact of root distribution within soils on the simulated drought response of seedlings, saplings, and mature trees. An annual simulation of soil water content for a deciduous forest in eastern Tennessee showed thatseedlings whose roots were restricted to the upper 20-cm of thesoil experienced far more 'drought days' than did saplings and larger trees that otherwise had access to deeper soil water reserves.We recognize that models of forest succession cannot include mechanistic detail on all potential below-ground processes and that there are obvious tradeoffs between model simplicity and more sophisticated parameterizations. We conclude, however, thatfeedbacks among global environmental change, seed germination and seedling establishment, above- and below-ground carbon allocation, root distribution within the soil profile, and soilwater and nutrient dynamics will be critically important for predicting forest dynamics and ecosystem function in the 21stcentury. As a result, steps should now be taken to ensure thatthese processes are represented in future gap models.

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BibTeX Citation

  author={Wullschleger, S. D. and Jackson, R. B. and Currie, W. S. and Friend, A. D. and Luo, Y. and Mouillot, F. and Pan, Y. and Shao, G.},
  title={Below-ground processes in gap models for simulating forest response to global change},
  journal={Climatic Change},

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RIS Citation

ID  - wu02000x
AU  - Wullschleger, S. D.
AU  - Jackson, R. B.
AU  - Currie, W. S.
AU  - Friend, A. D.
AU  - Luo, Y.
AU  - Mouillot, F.
AU  - Pan, Y.
AU  - Shao, G.
PY  - 2001
TI  - Below-ground processes in gap models for simulating forest response to global change
JA  - Climatic Change
VL  - 51
SP  - 449
EP  - 473
DO  - 10.1023/A%3A1012570821241
ER  -

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