Spruce shows greater sensitivity to recent warming than Douglas‐fir in central British Columbia
Bibliographic record
Abstract
Abstract The effects of climate change on tree growth in ecosystems limited by cold temperature remain unclear. In some cases, growth may increase, but because warmer temperatures can increase water stress, growth may also decline. As climate changes in the sub‐boreal spruce ( SBS ) zone in central British Columbia, hybrid white spruce ( Picea engelmannii × glauca )—a dominant but drought‐intolerant species of this region—is predicted to decline over much of its range, while species such as Douglas‐fir ( Pseudotsuga menziesii var. glauca ) are likely to replace spruce. To see whether these shifts are already evident, we examined recent trends in basal area increment ( BAI ) of these two species over the past 50 yr (1961–2010) and explored relationships with climate variables in the SBS zone across a range of sites varying in water availability due to differences in climate and soil moisture regimes. In addition, we analyzed wood δ 13 C during this period and root carbohydrate reserve ( NSC ) concentrations at the end of this period as indicators of water and carbon stress, respectively, to help interpret growth trends and climate relationships among sites. Spruce BAI was negatively associated with spring and/or summer temperature on all sites, but growth was never negatively correlated with temperature in Douglas‐fir. For both species, lower BAI on the driest site was accompanied by higher δ 13 C and lower root NSC reserve concentrations, particularly starch, consistent with drought stress reducing water and carbon availability for growth. However, there was no indication that the negative growth response to temperature was more pronounced on drier sites, as the only growth decline in spruce occurred on a mesic site with lower δ 13 C. We conclude that rising temperatures are likely to negatively impact the growth of spruce more than Douglas‐fir in the SBS zone, supporting predictions that spruce will decline and be replaced by other species like Douglas‐fir. And while rising temperatures may have already reduced growth on some sites, these declines are not clearly related to increasing drought stress but may relate to effects on the timing of snowmelt.
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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 | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".