Climate‐induced variation in the demography of 14 tree species is not sufficient to explain their distribution in eastern North America
Bibliographic record
Abstract
Abstract Aim Dynamic range models are proposed to investigate species distributions and to project range shifts under climate change. They are based upon the Hutchinsonian niche theory, specifying that the occurrence of a species in an environmental space should be limited to positions where the intrinsic growth rate is positive. Evaluating population growth rate is, however, difficult for physiologically structured populations, such as forest stands, owing to size‐induced individual variation in performance. Therefore, we still have a limited understanding of which aspect of tree demography contributes the most to their geographical range limit. We develop an index of demographic performance for size‐structured populations and study its variation across a climatic gradient. We then investigate the relationship between the demographic performance index and species distribution. Location North America (57–124° W, 26–52° N). Time period 1963–2010. Major taxa studied Fourteen tree species. Methods We represent forest dynamics with a size‐structured population model and neighbourhood competition with the perfect plasticity approximation. We then derive the lifetime reproduction per individual, , in the absence of density dependence. Using forest inventory data, we assess how tree demography for each species varies with climate. We test the model by comparing and the probability of occurrence within species ranges. Results We find that both growth and mortality rates vary across species distributions, but climate explains little of the observed variation. Individual size and neighbourhood competition are the primary explanatory variables of tree demography. Finally, we find that relates weakly to the probability of occurrence, with no systematic decline in population growth rates towards the range limits. Main conclusions Spatial and size‐induced variation in tree growth and mortality do not explain range limits and are insufficient to enable an understanding of tree dynamics. We propose that phenomena perceived mostly at the metapopulation scale should also be considered.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".