Niche partitioning and photosynthetic response of alectorioid lichens from subalpine spruce–fir forest in north-central British Columbia, Canada: the role of canopy microclimate gradients
Bibliographic record
Abstract
Abstract The distribution of alectorioid lichens in subalpine spruce-fir forests of north-central British Columbia is strongly influenced by vertical position within the canopy; Bryoria dominates upper canopy exposures, while Alectoria dominates lower canopy positions. The hypothesis that this height-related niche partitioning reflects differential growth responses to gradients in canopy microclimate is examined. Field measurements of canopy microclimate, taken over a 2-year period, were used in conjunction with laboratory-based measurements of net photosynthesis (NP) and dark respiration to model net assimilation (NA) response of Alectoria sarmentosa and Bryoria spp. (mixed collections of Bryoria fremontii and B. pseudofuscescens) at two different heights (15 and 4 m) within the canopy. Microclimate measurements indicate that lichen thalli are regularly hydrated from snowmelt events during the winter period (October-April), totalling 26 and 29% of the time, respectively, for Alectoria and Bryoria, though most winter hydration exposure (c. 75%) occurred in the dark. In the summer (May-September), rainfall was the major hydration source, with Alectoria and Bryoria each hydrated c. 16% of the time (45% of this in the dark). The NP temperature optimum (Topt) in light saturated thalli of Alectoria was 18.1 and 22.9°C, for winter and summer measurements, respectively. In Bryoria the corresponding seasonal rise in Topt was smaller, from 15.9 to 16.3°C. Both species showed an increase in maximum rates of NP during the summer period, from 1.52 to 1.92 mg CO2 g−1h−1 for Alectoria, and from 1.79 to 2.33 mg CO2g−1 h−1 for Bryoria. Although lichen hydration events peaked in early winter (October and November), NA modeling predicts that maximum growth should occur during the summer period. In Alectoria, higher rates of NA were predicted for thalli in lower canopy positions, especially during the summer months. In Bryoria, no clear trends of NA uptake with canopy position were observed. Thus, while NP response to gradients of canopy microclimate may provide a basis for niche partitioning in Alectoria, other factors (perhaps exclusionary) may be more important for Bryoria. One such factor is documented, namely the greater sensitivity of Bryoria to extended hydration exposure and we speculate that greater rates of fragmentation in upper canopy exposures may limit upper canopy biomass accumulation in Alectoria. Niche partitioning in these alectorioid lichens may therefore reflect both positive (growth responses) and negative (physical and physiological limitations) responses to gradients in canopy microclimate.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 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".