Reproduction and abundance of the wood frog (Lithobates sylvaticus) in post-harvest variable retention forests
Bibliographic record
Abstract
Many aquatic-breeding amphibians require freshwater habitat for reproduction and terrestrial habitat for refuge, foraging, and overwintering. Variable retention harvesting is a technique where live trees and other forest features are retained during timber harvesting in patterns that emulate natural disturbance. Wood frogs (Lithobates sylvaticus) are often associated with closed-canopy deciduous forests and utilize ephemeral (temporary) wetlands for reproduction. The objectives of this thesis were to (1) investigate the factors influencing upland abundance of wood frogs in post-harvest variable retention forest stands and (2) investigate the effects of wetland size and forest canopy on hydroperiod and tadpole performance in ephemeral wetlands of Alberta’s boreal mixedwood. To address these objectives, I used pitfall traps to live capture wood frogs across 4 levels of retention harvest (clearcut [0%], 20%, 50%, and unharvested control [100%]), and 2 forest types (deciduous and conifer), in 17-year post harvest forests at the EMEND experiment in northwest Alberta. I mapped breeding sites to account for breeding site proximity and used a LiDAR-based terrain moisture index (Depth-to-Water) to account for soil moisture. I also monitored 15 small ephemeral breeding wetlands from May to August 2015, at which I documented drying dates to assess relationships between wetland size (surface area, maximum depth), forest canopy cover, and hydroperiod. In 12 of the 15 wetlands, I measured tadpole performance by sampling tadpoles over repeated sampling sessions until tadpoles completed metamorphosis or until wetlands dried. I also measured physiochemical parameters (pH, conductivity, and temperature) and primary productivity (periphyton growth) to compare conditions between open- and closed-canopy wetlands. Abundance of adult wood frogs varied by season, with most captures occurring during early spring and summer months (May and June). Harvest retention level alone had no effect on abundance, but in late season (July and August), there was a significant interaction between retention and forest type where abundance decreased with retention level in deciduous sites, and increased with retention level in conifer sites. The interaction effect, however, was weak, and differences in capture rates between retention levels were small. During late season capture rates were higher in conifer forests relative to deciduous forests, with soil moisture (lower Depth-to-Water) significantly and positively related to capture rates. These results suggest early regeneration of aspen and availability of moist microhabitats create suitable upland habitat for wood frogs in early seral stage mixedwood forests. Among breeding wetlands, hydroperiod was related to wetland size, but not forest canopy cover. Depth was most related to hydroperiod and may therefore serve as a useful criterion for prioritizing protection of ephemeral breeding wetlands during forest harvesting. Growth and development of wood frog tadpoles were faster in wetlands with less surrounding canopy cover. Water temperature was higher in open-canopy wetlands relative to closed-canopy wetlands which may help explain observed differences in performance. There was, however, were no significant difference in primary productivity between open- and closed-canopy wetlands. I conclude that timber retention level has a weak effect on relative abundance of adult wood frogs in 17-year post harvest stands. Natural regeneration of deciduous species post-harvest may help provide suitable upland habitat for wood frogs in both deciduous and conifer forests. Protection of ephemeral wetlands with adequate depth and hydroperiod will help maintain local populations of wood frogs and other amphibians in managed forests in the boreal mixedwood.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| 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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".