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Peatlands with ground surfaces near the water table may be sensitive to disturbances that reduce this distance to water. Shrubby rich fens (SRF) in northern Alberta, Canada, are restricted to the wettest landscape positions and are characterized by brown mosses and stunted trees on weakly consolidated and saturated substrates. In situ oil sands exploration (OSE) practices have established thousands of drilling pads to explore for deeply buried bitumen deposits, with many located on peatlands. In the development of OSE pads on peatlands, the vegetation layer is removed, eliminating the functionally important hummock‐hollow surface topography. We examined the spontaneous regeneration of bryophytes and vascular plants and surface microtopography on SRF, 7 and again 14 years after pad abandonment. In both sampling years, drilling pad surfaces were closer to the water table (mean pad elevation 2012 = 3.3 cm, 2019 = 5.6 cm) and had minor topography compared to adjacent reference habitat. We found, however, over the 7 years, that for both drilling pads and reference habitat, bryophyte and vascular plant richness decreased, and most species declined in frequency. Furthermore, for pads and reference habitat, density of tree seedlings decreased, and expansion of hummock‐forming mosses was limited. Findings suggest that drilling pads and their natural counterparts on SRF may be prone to episodic reductions in plant diversity and ecosystem retrogression, likely resulting from prolonged surface saturation during summers with high rainfall. Because of their wet landscape positions and environmental vulnerability, SRF are likely the peatland habitats slowest to recover following OSE pad construction. [ABSTRACT FROM AUTHOR]

Rare moss diversity and distribution patterns are described for the province of Alberta. Multivariate analyses were used to elucidate the distribution patterns of the rare mosses in relation to environmental factors, in comparison with those of the common mosses. Hierarchical clustering of species occurrence among Alberta ecoregions resulted in 11 species groups having similar distributions and four ecoregion groups with similar species composition. Rare and common mosses show comparable distributions at the geographic scale of ecoregions; the analyses did not provide support that rare mosses respond to environment factors differently than common mosses. The rare mosses are more narrowly distributed among the species and ecoregion groups than are common species. The most important environmental variables determining species distributions are mean annual temperature and growing degree days. Other important factors determining moss distribution are mean elevation, annual rainfall, and mountain landscape. Diversity patterns are shown to vary widely among the ecoregions and to differ between rare and common species. Rare species are especially diverse in the Rocky Mountains, which support 81% of the province's known rare moss flora and reflect a complex of diverse landscapes for moss colonization. Only 40% of known rare species in Alberta are found in nonmountainous regions. [ABSTRACT FROM AUTHOR]

Site moisture is an important component of the forest landscape for maintaining biodiversity, including forest‐floor bryophytes. However, little is known about its role in shaping understorey responses to harvesting.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 DTW 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 north‐western Alberta, Canada.The effectiveness of leaving retention (vs. 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 (vs. clear‐cutting) on wetter (vs. drier) sites was more effective for conserving bryophyte cover, wetter sites had higher total species richness and more species were exclusive to wetter sites.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 forests 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. 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 forests 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. [ABSTRACT FROM AUTHOR]

Given the habitat moisture (air humidity or soil moisture) preferences of many forest bryophytes, we explored whether the depth-to-water (DTW) index, derived from remotely sensed Light Detection and Ranging (LiDAR) data, was related to fine-scale patterns of spatial variation in bryophyte abundance, diversity, and composition. The goal was to assess the utility of the topographic DTW index as a tool to decipher trends in bryophyte assemblages along a site wetness gradient in the boreal mixedwood forest. Discrete Airborne Laser Scanning (ALS) data were acquired over the entire Ecosystem Management Emulating Natural Disturbance (EMEND) experimental site located in northwestern Alberta, Canada (56° 46′ 13″ N, 118° 22′ 28″ W), based on which we calculated a mathematical index of approximate depth to water at or below the soil surface at 1 m resolution using the Wet-Areas Mapping model. Bryophytes (mosses and liverworts) were sampled in permanent sample plots in unmanaged forest stands of varying dominant canopy tree composition. The relationships between DTW and bryophyte cover, richness, diversity, and composition in broadleaf (deciduous)-, mixed, and conifer-dominated boreal forest stands were analyzed using linear mixed-effect models and multivariate analyses. Bryophyte cover was highest in conifer-dominated forest, which occupied the wetter end of the DTW gradient, followed by mixed forest, whereas broadleaf forest, which occupied the drier end of the DTW gradient, had the lowest cover but highest bryophyte diversity. Bryophyte cover in conifer-dominated forests was positively related to site moisture (negatively related to the DTW index). In contrast, bryophyte species richness and diversity were negatively related to site moisture (increased at higher DTW values) in all forest types. DTW explained significant variation in bryophyte species composition in mixed forests, while indicator species analysis identified species with preferences for wet, moist, and dry site conditions in each forest type. Our results corroborate the importance of site moisture as a driver of bryophyte assemblages but, interestingly, there were important differences among forest types, which themselves are distributed across a gradient of site moisture. Our study demonstrates the utility of the topographic DTW index for understanding fine-scale (plot-level) variation in bryophyte assemblages in forested landscapes. [ABSTRACT FROM AUTHOR]

Abstract: Variable‐retention harvest is widely recognized as an alternative to more intensive methods such as clear‐cutting. However, present information is inadequate to judge the impact of variable retention on biodiversity of indigenous forest organisms intolerant of canopy removal, such as forest‐inhabiting bryophytes. 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 North West Alberta, Canada. Bryophytes were studied in 432 permanent sample plots within 72 compartments before harvest and at 3, 6 and 11 years after harvest. 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. Synthesis and applications. Variable‐retention harvests can better maintain bryophyte biodiversity in managed boreal mixedwood forests, as compared to clear‐cuts. We found the efficacy of retention harvest scaled with harvest intensity. Higher levels of retention better moderated the negative impacts of harvesting on bryophyte assemblages across all forest types. Our results suggest, however, that even 10% retention will facilitate faster post‐harvest recovery of bryophytes, as compared to clear‐cutting. [ABSTRACT FROM AUTHOR]

Epiphytic mosses and liverworts contribute substantially to the bryophyte diversity of circumpolar boreal forests but are susceptible to altered growing conditions after forest harvesting. Management practices that retain some trees after harvest may enhance epiphyte survival; however, the effectiveness of this emerging method needs to be assessed. We examined the survival, composition, and nearest neighbour relationships of epiphytic bryophytes on trembling aspen (Populus tremuloides Michx.) across a range (10%–100%) of dispersed green-tree retention 5 years after harvest in boreal mixed-wood forest. Growth of the forest floor moss Hylocomium splendens (Hedw.) Schimp. in B.S.G. was used as an indicator of changes in moisture availability for epiphytes following harvesting. Epiphyte richness and abundance increased with canopy retention and were positively correlated with local abundance of coniferous trees. Positive associations among neighbouring species in intact forest demonstrated that interspecies relationships form naturally. However, there was a shift in species composition after harvesting and fewer interspecific associations with declining retention. These trends were accompanied by reduced Hylocomium splendens growth, which implies that moisture may be an important driver of epiphyte response. Although different levels of canopy retention were similarly capable of maintaining some epiphytes, the loss of species associated with intact forest will require consideration of alternative management practices for their conservation. Les mousses et les hépatiques épiphytes contribuent substantiellement à la diversité des bryophytes des forêts boréales circumpolaires, mais sont sensibles aux modifications des conditions de croissance, suite aux opérations forestières. Les méthodes d’aménagement qui conservent certains arbres après la récolte peuvent améliorer la survie des épiphytes; cependant, on doit évaluer l’efficacité de ces méthodes en émergence. Les auteurs ont examiné la survie, la composition et les relations avec les voisins les plus rapprochés des bryophytes épiphytes sur le peuplier faux-tremble (Populus tremuloides Michx.) pour l’ensemble d’une aire (10 % à 100 %) comportant des arbres vivants conservés et dispersés, 5 ans après la récolte dans une forêt boréale mixte. Ils ont utilisé la croissance d’une mousse du parterre forestier, l’Hylocomium splendens (Hedw.) Schimp. in B.S.G., comme indicatrice des modifications de la disponibilité de l’humidité pour les épiphytes, suite à la récolte des arbres. La richesse et l’abondance des épiphytes augmentent avec la rétention de la canopée et montrent des corrélations positives avec l’abondance localisée de conifères. Les associations positives avec les espèces avoisinantes dans la forêt intacte démontrent que des relations interspécifiques se forment naturellement. Cependant, on observe un déplacement de la composition en espèces après la récolte et moins d’associations interspécifiques avec une diminution de la rétention. Ces tendances s’accompagnent d’une réduction de la croissance de l’ Hylocomium splendens, ce qui implique que l’humidité pourrait être un agent causal important de la réaction des épiphytes. Bien que différents degrés de conservation de la canopée peuvent être également aptes à maintenir certaines épiphytes, la perte d’espèces associées aux forêts intactes nécessitera la définition de méthodes alternatives d’aménagement pour leur conservation. [ABSTRACT FROM AUTHOR]