Recherche

Dryad Translation missing: fr.blacklight.search.logo
Data from: Depth-to-water mediates bryophyte response to harvesting in boreal forests
Bartels, Samuel F.; James, Ryan S.; Caners, Richard T.; Macdonald, S. Ellen — 2019-02-15 1. Site moisture is an important component of the forest landscape for maintaining biodiversity, including forest-floor bryophytes, but little is known about its role in shaping understory responses to harvesting. 2. We investigated the influence of site wetness, determined using a remotely-sensed, topographic depth-to-water (DTW) index, on responses of bryophyte cover, richness, diversity, and composition to variable retention harvesting (comparing: 2% [clear-cut], 20%, and 50% dispersed green tree retention and uncut controls [100% retention]) in three boreal forest cover-types (broadleaf, mixed, and conifer forests) in western Canada. The DTW index provides an approximation of depth to water at or below the soil surface, and was derived from wet-areas mapping based on discrete Airborne Laser Scanning data acquired over an experimentally harvested landscape located in northwestern Alberta, Canada. 3. The effectiveness of leaving retention (versus clear-cutting) for conserving bryophyte communities depended on site wetness, as indicated by DTW, with the specifics varying among forest types. In broadleaf forests, bryophyte cover and richness were generally low and not much affected by harvesting but drier sites had higher richness and a few more unique species. In mixed and conifer forests, leaving retention (versus clear-cutting) on wetter (versus drier) sites was more effective for conserving bryophyte cover, wetter sites had higher total species richness, and more species were exclusive to wetter sites. 4. Synthesis and applications. Site wetness, as indicated using the remotely-sensed topographic site wetness index "depth-to-water," mediates bryophyte responses to variable-retention harvests. Specifically, our results suggested that in conifer and mixed forests it would be more beneficial to target wetter sites for retention patches or dispersed retention whereas in broadleaf sites there might be a slight advantage to targeting drier sites. Our study demonstrates that this tool could be used to inform management decisions around leaving dispersed or patch retention.28-Jan-2019
Dryad Translation missing: fr.blacklight.search.logo
Dynamics and recovery of forest understory biodiversity over 17 years following varying levels of retention harvesting
Bartels, Samuel F.; Macdonald, S. Ellen — 2023-01-10 <p>1. Retention harvesting is advocated as an alternative to intensive timber harvesting, such as clear-cutting, to better maintain or facilitate recovery of biodiversity and other ecological values in managed forests. However, it is not clear how long the benefits of retention harvests persist.</p> <p>2. We investigated responses of understory vascular plant cover, richness, diversity (inverse Simpson index), and composition to a gradient in dispersed retention (2% [clear-cut], 10%, 20%, 50% and 75% retention; unharvested reference [100% retention]) at 3, 6, 11, and 17 years after harvest, in four boreal mixed wood forest types (deciduous (broadleaf)-dominated, deciduous-dominated with conifer understory, mixed, and conifer-dominated) in western Canada.</p> <p>3. Understory cover and richness tended to increase in the short-term (3 years), peaked at 6–11 years with differences following the gradient of harvesting intensity, then plateaued or declined in the second decade (17 years), by which time there were minimal or no differences among harvesting levels, including the reference. Responses for diversity were minimal. In contrast, composition varied along the gradient of harvesting intensity and showed little recovery towards the unharvested condition over the 17-year period. Generally, for plant community composition, clear-cut and lower retention treatments (10%, 20%) were similar to one another but differed from the higher retention and unharvested reference treatments.</p> <p>4. Synthesis and applications. Retention harvests can moderate the negative impacts of harvesting and facilitate the recovery of biodiversity. Our results suggest that for the cover, richness and diversity of understory vascular plants, this moderating influence is weak and short-lived. However, higher levels of retention can temper changes in understory composition relative to the unharvested forest, but full recovery is likely to be slow and will be complicated by post-harvest regeneration dynamics.</p>
Dryad Translation missing: fr.blacklight.search.logo
Data from: Bryophyte abundance, diversity and composition after retention harvest in boreal mixedwood forest
Macdonald, S. Ellen; Bartels, Samuel F.; Johnson, Derek; Caners, Richard T.; Spence, John R. — 2017-08-23 1. Variable-retention harvest is widely recognised as an alternative to more intensive methods such as clear-cutting. However, present information is inadequate to judge impact of variable-retention on biodiversity of indigenous forest organisms intolerant of canopy removal, such as forest-inhabiting bryophytes. 2. We examined how bryophyte species cover, richness, diversity and composition change with time in response to a broad range of dispersed retention harvest treatments (2% (clear-cut), 10%, 20%, 50%, 75% retention of original basal area) contrasted with uncut controls (100% retention)) in broadleaf deciduous, mixedwood and conifer-dominated boreal forests in NW Alberta, Canada. Bryophytes were studied in 432 permanent sample plots within 72 compartments before harvest and at three, six and eleven years after harvest. 3. Clear-cut and lower (10% and 20%) retention levels resulted in lower cover and richness of bryophytes than in unharvested control compartments in mixed and conifer-dominated forests, but less so in deciduous-dominated forests, which generally supported low cover and richness. Species composition in each forest type varied along the gradient of harvesting intensity; clear-cuts and lower levels of retention supported similar composition, as did control plots and those representing higher retention levels. Over time the retention harvest treatments became more similar to uncut controls. 4. Synthesis and applications. Increased retention moderated the negative impacts of harvesting on bryophyte assemblages across all forest types, and our results suggest that even 10% retention will facilitate faster post-harvest recovery of bryophytes.02-Aug-2017 https://creativecommons.org/publicdomain/zero/1.0/
Dryad Translation missing: fr.blacklight.search.logo
Data from: Reclamation strategies for mined forest soils and overstorey drive understorey vegetation
Dryad
Chen, Han Y. H.; Biswas, Shekhar R.; Sobey, Timothy M.; Brassard, Brian W.; Bartels, Samuel F.; Chen, Han Y.H. — 2018-08-31 1. Understorey vegetation accounts for the majority of plant diversity in forest ecosystems and contributes to ecosystem functioning. In restoration of degraded forested ecosystems, however, understorey vegetation is often restored passively, contrasting to clear strategies such as informed species choice and site improvement intervention for overstorey vegetation. The choice of overstorey-centered restoration strategy may have important consequences for understorey vegetation. 2. We examined the effects of substrate material, overstorey type and time since reclamation (age) on understorey vegetation following reclamation of oil sands mining in Alberta, Canada. We sampled cover, richness, evenness and composition of understorey vegetation at 94 sites of conifer, mixedwood and broadleaf overstorey types on three reclamation substrates (overburden, secondary overburden and tailings sand), with age ranging from 4 to 30 years. 3. Total, woody and non-woody understorey cover and species richness were the highest on secondary overburden and the lowest on tailings sand, and total cover also decreased with age. Woody cover and richness were the highest under broadleaf overstorey, while non-woody cover and richness were the lowest under conifer overstorey. Overall species evenness was not significantly affected by substrate type, overstorey type or age, but woody evenness was the highest on secondary overburden and the lowest on tailings sand, and non-woody evenness showed overstorey-dependent responses to age. Species composition varied with substrate type, overstorey type and age. Indicator species analysis revealed that tailings sand with conifer overstorey favored grasses, while overburden and secondary overburden supported a mix of grasses, forbs and shrubs. 4. Synthesis and applications: Our study demonstrates that overstorey-centered reclamation strategies impact the abundance, diversity and composition of understorey plant communities following oil sands mining. Landforms constructed with secondary overburden substrates and revegetated with mixedwood or broadleaf tree species provide the most favourable habitats for understorey vegetation, while tailings sand to be a poor substrate for understorey species diversity and composition. We therefore recommend utilizing secondary overburden and overburden substrate material during landform construction, and employing revegetation prescriptions that target mixedwood and broadleaf overstorey types to promote productive and diverse understorey plant communities on the reclaimed landscape.

Instructions pour la recherche cartographique

1.Activez le filtre cartographique en cliquant sur le bouton « Limiter à la zone sur la carte ».
2.Déplacez la carte pour afficher la zone qui vous intéresse. Maintenez la touche Maj enfoncée et cliquez pour encadrer une zone spécifique à agrandir sur la carte. Les résultats de la recherche changeront à mesure que vous déplacerez la carte.
3.Pour voir les détails d’un emplacement, vous pouvez cliquer soit sur un élément dans les résultats de recherche, soit sur l’épingle d’un emplacement sur la carte et sur le lien associé au titre.
Remarque : Les groupes servent à donner un aperçu visuel de l’emplacement des données. Puisqu’un maximum de 50 emplacements peut s’afficher sur la carte, il est possible que vous n’obteniez pas un portrait exact du nombre total de résultats de recherche.

(auteur : Bartels, Samuel F.)

Limiter par :

Effacer tout

au