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Natural disturbance‐based management (NDBM) is hypothesized to maintain managed forest ecosystem integrity by reducing differences between natural and managed forests. The effectiveness of this approach often entails local comparisons of species composition or diversity for a variety of biota from managed and unmanaged forests. Understory vegetation is regularly the focus of such comparison because of its importance in nutrient cycling, forest regeneration, and for wildlife. However, larger scale comparisons between regions with distinct species assemblages may require a trait‐based approach to better understand understory responses to disturbance. We compared the long‐term effects of retention harvesting on understory vegetation in two large experimental study sites located in eastern and western regions of the Canadian boreal forest. These sites included the Sylviculture en Aménagement Forestier Ecosystémique (SAFE) experiment and the Ecosystem Management Emulating Natural Disturbance (EMEND) experiment, located in the eastern and western regions of Canada, respectively. EMEND and SAFE share common boreal understory species but have distinct tree communities, soils, and climate. Both experiments were designed to evaluate how increasing tree retention after harvest affects biodiversity. Here, we examined taxonomic richness, functional diversity, and functional composition (using community trait mean values) of understory plant communities, and also examine intraspecific trait variability (ITV) for five species common and abundant in both experiments. We observed the limited impacts of retention level on richness, functional diversity, and functional composition of understory plants 20 years postharvest. However, ITV of leaf morphological traits varied between retention levels within each experiment, depending on the species identity. Common species had different functional responses to retention level, showing species‐specific reactions to environmental variation. Our result suggests that understory plant communities in the boreal forest achieve resilience to disturbance both in terms of interspecific and intraspecific functional trait diversity. Such diversity may be key to maintaining understory biodiversity in the face of future disturbances and environmental change. Our results reveal the significance of ITV in plant communities for understanding responses to forest harvesting and the importance of choosing appropriate traits when studying species responses to the environment. [ABSTRACT FROM AUTHOR]

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Given a seed source, the quality of available substrates is a key factor in determining the success of white spruce ( Picea glauca (Moench) Voss) natural regeneration. We examined the influence of substrate and competing vegetation on survival and growth of natural regeneration of white spruce up to 4 years following harvesting in deciduous-dominated upland boreal mixedwood sites. Feather moss, thick soil surface organic layers, litter, and solid wood were poor substrates for establishment. Early successional mosses establishing on mineral soil, thin organics, and rotten wood were generally favourable microsites but were not highly available on postharvest sites. Mineral soil substrates were not as suitable as expected, likely because on a postlogged site, they are associated with unfavourable environmental characteristics (e.g., low nutrient availability, exposure). There was some evidence that survival and growth of seedlings were improved by surrounding vegetation in the first years, but heavy competing vegetation had a negative impact on older seedlings. Burial by aspen litter greatly increased seedling mortality, especially when combined with a brief period of submergence due to heavy spring snowmelt. The results provide insight into conditions under which natural regeneration could be an option for establishing white spruce following harvesting of deciduous-dominated boreal mixedwood forests. [ABSTRACT FROM AUTHOR]

Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Terrestrial gastropods are important decomposers, herbivores, and prey items in forest systems and constitute a poorly understood element of forest biodiversity in Canada. We sampled terrestrial gastropod assemblages in northwestern Alberta, Canada, using board traps and forest floor sampling to examine their association with forest composition, structure, and environment (forest floor depth and moisture, coarse woody debris, understory vegetation cover) in four boreal mixedwood cover types: broadleaf (deciduous) dominated (DDOM), broadleaf (deciduous) dominated with coniferous understory (DDOMU), mixed conifer and broadleaf (MX), and conifer dominated (CDOM). The highest total gastropod abundance and richness occurred in the DDOM cover type. Furthermore, DDOM assemblages accumulated species more quickly (with sampling effort) and supported more gastropod species at higher levels of dominance than found in other cover types. The mix of coniferous and broadleaved trees influenced gastropod distributions within stands; however, associations observed between gastropod species and tree species differed among cover types, suggesting complex ecological contingency. For example, conifer basal area was an important driver of gastropod assemblage in DDOM and DDOMU forests, whereas broadleaf basal area was the most important driver in the CDOM forest type. We conclude that tree species mixture at a variety of scales sustains diversity of gastropod assemblages and that this understanding is significant for conservation of this taxon on mixedwood boreal forest landscapes. [ABSTRACT FROM AUTHOR]

Abstract: The range expansion of mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae, Scolytinae)) from the focal region of the recent major epidemic in British Columbia, Canada to the north and east into Alberta’s lodgepole pine forests may alter the future successional pathway of these forests. Thus, there is a need for an improved understanding of recruitment dynamics of lodgepole pine in both healthy and MPB-attacked stands arising from this shift from a fire-driven disturbance regime to a disturbance regime that also includes MPB. We evaluated the potential impacts of mountain pine beetle attack and associated forest management on the future regeneration potential of lodgepole pine forests in western Alberta. We quantified seedbed availability and advance regeneration, and compared lodgepole pine recruitment of sown seed on five different seedbed types (i.e., moss, shallow organic, deep organic, decayed wood, and mineral soil) within four different stand treatment types that simulated mountain pine beetle attack and forest management disturbance (i.e., control, moderate MPB attack, high intensity MPB attack, and salvage harvest) in the Upper Foothills of western Alberta. Recruitment from sown seed 1–3years after MPB attack was poor (median 0%, 0–2% 5th–95th percentiles) across stand treatment types for moss and both organic seedbed types. Decayed wood and mineral soil were the best seedbed types, with higher recruitment rates than the organic and moss seedbeds, although recruitment was still relatively low (median 0%, 0–6% 5th–95th percentiles). Recruitment rates of seedlings on decayed wood and mineral soil seedbed types increased with increasing levels of disturbance; recruitment was lowest in control stands, higher in the simulated MPB-attack treatments, and highest in the salvage logged stands. However, these favorable seedbeds were scarce among all stand treatment types. Given the extremely low levels of advance regeneration and lack of natural regeneration we observed initially after MPB attack in our study sites, we anticipate that future stand development will be hampered by a lack of lodgepole pine recruitment, at least in the short term. If the goal is a re-stocked forest, significant silvicultural intervention will be required for lodgepole pine forests attacked by MPB within novel habitat ranges in western Alberta. [Copyright &y& Elsevier]

Abstract: Forest harvesting practices designed to conserve biodiversity require further insight into the relationship between species habitat requirements and how these are preserved after harvest. We examined the effects of different levels (10%, 50%, and 75%) of dispersed green-tree retention (unharvested stands as controls) on the diversity and composition of bryophytes 5–6years after partial harvesting. Bryophytes were sampled in six large (20m radius) plots in 24 forest stands (each 10ha) using a factorial experimental design with replication at the stand level. Sampled stands represented two mixedwood forest canopy types with contrasting abundances of broadleaf and coniferous trees before harvesting. Mosses and liverworts both responded to retention level and forest type but liverwort response was more pronounced. Liverwort richness and diversity were reduced at low (10% and 50%) retention, and composition differed between all harvested levels and the control. In comparison, mosses did not differ in richness or diversity among retention levels but at low retention composition differed from that of intact forest. Bryophyte responses to harvesting were partly explained by species substrate preferences: epixylics on decayed wood and epiphytes on bark experienced declines in richness with any level of harvesting, whereas responses for species on other substrates were not as apparent. Furthermore, partial harvesting influenced regional patterns of species diversity, as revealed by additive partitioning of diversity into within-plot (alpha) and among-plot and among-stand (beta) components. For both mosses and liverworts, total beta diversity explained the greatest proportion of total diversity for each retention level, indicating that species representation in boreal mixedwood landscapes after harvesting needs to be considered at multiple hierarchical levels. Total beta diversity of liverworts but not mosses increased substantially at low retention, reflecting greater among-plot and among-stand differentiation of liverwort assemblages with increasing disturbance. Results highlight the importance of canopy retention and composition for maintaining bryophytes in managed forests. Although several species persisted at low retention, intact forest is required for the conservation of numerous species that are sensitive to any degree of harvest. Implementation of conservation strategies for bryophytes in managed boreal forests should consider species diversity not only at local scales but also differences among entire forest stands. [Copyright &y& Elsevier]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Progress in understanding the patterns of plant diversity requires a conceptualization and quantification of the hierarchy of patch configuration that exists in plant communities across levels of observation. In order to identify the scales at which vascular plant diversity is maximized, we investigated the hierarchical organization of understory vascular plant diversity in relation to canopy patch types in mature boreal mixedwood forests in western Canada. In each of two study areas within a 30km2 landscape (55° N, 112° E) we sampled four canopy patch types: conifer, mixed conifer-broadleaf, broadleaf and canopy gaps. Understory diversity (richness and Shannon’s (H′) index) was additively partitioned in relation to these four canopy patch types across a hierarchy of four scales; α-individual patch +β1-among patches within canopy patch type +β2-among canopy patch types within area +β3-between areas. We also examined understory species abundance patterns by means of rank-abundance plots fitted to relative abundance models. The largest partition of species richness was among patches within canopy patch type (β1). For Shannon diversity index, the largest partition was at the within-individual patch level (α1) indicating that evenness was high at the patch level but that dominance increased at higher levels in the hierarchy. The assessment of relative abundance by means of rank abundance plots suggested that the canopy patch types differed in terms of the ecological mechanisms influencing diversity patterns. Considering plant diversity within a hierarchical framework is critical for the understanding and management of biodiversity as maximum levels of plant richness and evenness do not necessarily occur at the same observational scales. Management practices which retain the natural hierarchies of vegetation patches will help conserve plant community richness and diversity. [Copyright &y& Elsevier]

Increasing environmental concerns with forestry have led to mounting interest in mixedwood management as a possible strategy to achieve a diversity of ecological and productivity goals within the context of sustainable forest management. This review focuses on the effects of mixedwoods on biodiversity including understory plants, birds, soil fauna, and ectomycorrhizae (ECM). It examines stand-level species diversity and composition but particularly focuses on the regional scale (gamma diversity) by examining evidence for the occurrence of mixedwood-indicator species. The main conclusions are as follows: ( i) The existence of different tree species in the canopy is associated with provision of a greater diversity of microhabitats allowing for the addition of understory plant species associated with each canopy species. However, there is little evidence for the existence of understory plant species uniquely associated with mixedwoods. ( ii) Some bird species require or prefer the presence of different tree species within a landscape or within a stand. Mixed forest stands and landscapes are thus critical to support populations of these species. ( iii) A few studies showed a positive effect of mixed stands or mixed litters on some groups of soil organisms, but high variability makes it difficult to draw firm conclusions about any potential benefits of mixedwoods for biodiversity of soil fauna. ( iv) Some ECM taxa are associated with multiple hosts, and could thus benefit from availability of multiple possible host species found in mixed forest stands. Several studies confirmed that there was a greater abundance of multiple-host ECM taxa in mixedwoods. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Reviews is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Provides information on the 4th International Workshop on Disturbance Dynamics in Boreal Forest held at the University of Northern British Columbia on August 9 to 12, 2002. Issues involving forest management discussed at the event; Keynote speakers who were present in the workshop; Discussion on the importance and role of disturbance in shaping boreal forest.