Cedar-hemlock Forests Research Articles

Lifeboat or sinking ship: will the size and shape of Old-Growth Management Areas provide viable future habitat for temperate rainforest lichens?

The Kispiox Timber Supply Area, a 1.3 million ha region in northwestern British Columbia, Canada, supports a significant assemblage of temperate rainforest (oceanic) lichens that depend on old forests. Given their known sensitivity to edge effects, we ask whether or not the current configuration of Kispiox Old-Growth Management Area (OGMA) reserves will provide viable future habitat for oceanic lichens as surrounding landscapes are progressively logged in coming decades. Landscape indicators were calculated from provincial map data sets. Old Interior Cedar–Hemlock biogeoclimatic zone forests, the primary habitat for Kispiox oceanic lichens, had a landscape shape index of 6.4 in OGMAs, indicative of elongate shapes susceptible to edge effects. Mean patch size in OGMAs was 43 ha, with the largest patch size being 1 378 ha. In contrast, the landscape shape index for pre-industrial old cedar–hemlock forests was 1.3, with a mean patch size of 1 293 ha and largest patch size of 23 357 ha. When modelled edge effects were extended to 120 m, only 25% of cedar–hemlock forests in Kispiox OGMAs remained interior habitat (7 754 ha total). Adoption of silvicultural practices that maintain buffer zones around existing OGMAs, and the designation of additional OGMAs, especially in watersheds with intact old cedar–hemlock forests, is recommended to conserve oceanic lichen communities in the Kispiox region.

Retention level affects dynamics of understory plant community recovery in northern temperate hemlock-cedar forests

Retention forestry is replacing clear-cutting as the dominant silvicultural practice in many parts of the world. Higher retention levels are thought to promote faster, more complete ecological recovery after logging, but this hypothesis is insufficiently tested. We compared plant community dynamics in 0%, 40% and 70% retention stands to unharvested stands for 24 years after logging at the Date Creek Research Forest near Kispiox, BC, Canada. The study has a before-after control-impact experimental design with four replicates of each treatment. For terricolous understory plants, we used the similarity of cover, species richness and composition to pre-harvest and unharvested conditions as indicators of ecological integrity. Changes in cover, richness and composition were greatest at 0% retention. For nonvascular plants, changes were generally intermediate at 40% retention and smallest at 70% retention, and recovery increased with retention. The dominant moss Hylocomium splendens responded negatively to harvest in proportion to retention level, while most other species responded positively, shifting community composition. Most vascular plants responded positively to harvest, especially at 0% retention, with the exception of two late seral species, Platanthera orbiculata and Oplopanax horridus. Generally, understory communities in these largely unfragmented northern cedar-hemlock forests displayed less sensitivity to low retention levels than studies conducted elsewhere. For some vascular plant indicators, changes at 70% retention were equal to or greater than those at 40%. Thus, most -but not all- vegetation responses supported the hypothesis that higher retention enhances ecological recovery after logging. The non-linear results were apparently driven by suppression of understory conifer growth in small gaps at 70% retention and illustrate that evaluating ecological integrity strictly in terms of departure from an un-impacted benchmark system risks oversimplifying complex forest dynamics.

Forest vegetation change and disturbance interactions over the past 7500 years at Sasquatch Lake, Columbia Mountains, western Canada

Fire is the most important abiotic disturbance in the interior cedar-hemlock (ICH) and Engelmann spruce–subalpine fir (ESSF) forest zone of southeastern British Columbia, Canada. Other disturbances are also important, such as defoliator and boring insect outbreaks, windthrow, diseases, and rapid mass movements. Few studies have examined the interaction between multiple types of disturbances in these forests over long timescales. Here we present high-resolution analyses of biomass burning, erosion, and vegetation assemblage changes at Sasquatch Lake (NEL02), a valley lake in the Columbia Mountains. The 531.5 cm sediment core was radiocarbon dated and provided a 7500-year stratigraphy that was used for pollen, macroscopic charcoal (>150 μm), and sedimentologic analyses. Pollen and charcoal data provided evidence of forest composition changes and fire activity. Magnetic susceptibility, loss-on-ignition, and particle size distribution analyses characterised changes in erosion into the basin. The results show that coniferous forests, with a high abundance of Pinus pollen, had established in the catchment by the beginning of the record and were subject to intermittent burning and high-energy erosive events. Tsuga heterophylla expanded by 4400 cal BP and the modern interior cedar-hemlock forests expanded throughout the lower elevations due to increased regional continentality since 4500 cal BP. High-energy erosional inputs to the lake were less frequent from 3500 to 750 cal BP and rapid mass movements may have increased in frequency during the Little Ice Age. Dendrochronological evidence in these stands suggests a mixed-severity fire regime during past ∼300 years, which has not been fully examined for charcoal-based fire event reconstruction. Here we use identified peaks as an indicator of increased biomass burning and charcoal movement in the catchment in relation to peaks in allochthonous clastic material to understand the potential relationships between biomass burning and erosion events at multiple temporal scales in the catchment. This suggests that post-fire conditions, up to several decades, were subject to increased erosion to the lake and erosion events were more common during the early Holocene. Establishment of dense ESSF and ICH forests decreased siliciclastic input to the lake throughout the mid Holocene until a recent rockslide. The high-resolution sampling of this lake sediment record provides long-term evidence of variability in the relationships between vegetation cover, fire and erosion at a catchment scale.

Macrolichen diversity as an indicator of stand age and ecosystem resilience along a precipitation gradient in humid forests of inland British Columbia, Canada

The distributional ecology of 87 macrolichens is reported from 14 unmanaged mid-seral and old forest stands along a precipitation gradient in south-central British Columbia. We used a combination of univariate and multivariate statistics to investigate the role of forest structure and stand age in the distribution of epiphytic macrolichens in interior cedar-hemlock forests. Old forests support a higher number of species; although mean species richness is not significantly different between the two age classes. Terricolous and epixylic community structure is correlated with stand age and log characteristics, but the epiphtytic community is not. Epiphytic community structure is strongly associated with precipitation in the old stands, but not in the mid-seral stands. Old forests at the wetter end of the precipitation gradient contained several old-growth associated species, all of which are hygrophytic. Most epiphytic macrolichens associated with old forests are not dependent on specific structural attributes. However, western red cedar (Thuja plicata Donn ex D. Don) harbors the greatest number of arboreal macrolichen species by far in these unmanaged stands and should, therefore, be considered a key indicator in managed forests. Our study suggests that most macrolichen species found in old forests can also occur in 70- to 165-year-old forests dating from stand-replacing fires. Old forests, however, clearly provide important habitat for oceanic epiphytes at the edge of their ecological range in the interior of British Columbia. Our findings illustrate that the macrolichen flora in wet toe-slope stands in humid inland British Columbia has a high level of resilience following disturbance under natural succession conditions. It also underlines the point that some species, like Lobaria pulmonaria, are good indicators of old-growth forests in certain regions but not in others, suggesting a careful use of the term old-growth dependence.

Evidence against planting lodgepole pine monocultures in the cedar-hemlock forests of southeastern British Columbia

Single-species planting of lodgepole pine (Pinus contorta var. latifolia) following clear-cut logging or wildfire has been common throughout interior British Columbia, Canada, but health problems with the species have been documented as it grows beyond the juvenile stage. We examined damage and stocking in twenty-seven 15to 30-yearold lodgepole pine plantations that were previously declared free growing in the highly productive cedar–hemlock forests in southeastern British Columbia, where lodgepole pine is absent from many primary forests. In order to be free growing, stands must meet minimum tree density, height, damage and brush competition criteria as legislated by the Provincial government. Overall, 44 per cent of lodgepole pine trees had unacceptable damage (causing them to be rejected as crop trees), and as a direct result, one-third of the plantations were no longer defined as free growing because there were insufficient crop trees remaining. Natural regeneration of other tree species partially compensated for the unhealthy pine. Logistic regression and odds ratio analysis associated increasing risk of damage from western gall rust with increasing soil moisture, more northerly aspects and mechanical site preparation, and decreasing risk with pre-commercial thinning treatment. Risk of damage from snow and ice was associated with increasing mean annual precipitation, decreasing longitude and broadcast burning. Risk of bear damage was associated with increasing soil moisture, pre-commercial thinning treatment and broadcast burning. Based on our results, we recommend that single-species planting of lodgepole pine be curtailed in the Interior Cedar–Hemlock zone in southeastern British Columbia.

Projecting future distributions of ecosystem climate niches: Uncertainties and management applications

Projecting future distributions of ecosystems or species climate niches has widely been used to assess the potential impacts of climate change. However, variability in such projections for the future periods, particularly the variability arising from uncertain future climates, remains a critical challenge for incorporating these projections into climate change adaptation strategies. We combined the use of a robust statistical modeling technique with a simple consensus approach consolidating projected outcomes for multiple climate change scenarios, and exemplify how the results could guide reforestation planning. Random Forest (RF) was used to model relationships between climate (1961–1990), described by 44 variables, and the geographic distribution of 16 major ecosystem types in British Columbia (BC), Canada. The model predicted current ecosystem distributions with high accuracy (mismatch rate=4–16% for most ecosystem classes). It was then used to predict the distribution of ecosystem climate niches for the last decade (2001–2009) and project future distributions for 20 climate change scenarios. We found that geographic distributions of the suitable climate habitats for BC ecosystems have already shifted in 23% of BC since the 1970s. Consensus projections for future periods (2020s, 2050s, 2080s) indicated climates suitable for grasslands, dry forests, and moist continental cedar–hemlock forests would substantially expand; climate habitat for coastal rainforests would remain relatively stable; and habitat for boreal, subalpine and alpine ecosystems would decrease substantially. Using these consensus projections and data on the occurrence of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) in BC ecosystems, we estimated a twofold increase in seedling demand for this frost-sensitive, commercially important timber species, suggesting managers could begin planning to expand seed inventories and seed orchard capacity to more widely plant this species on logged sites. The results of this work demonstrate the power of RF for building climate envelope models and illustrate the utility of consensus projections for incorporating uncertainty about future climate into management planning. It also emphasizes the immediate need for adapting natural resource management to a changing climate.

Decline of planted lodgepole pine in the southern interior of British Columbia

Lodgepole pine is extensively planted across western Canada but little is known about development of these stands beyond the juvenile stage. We quantified stocking status and damage incidence in sixty-six 15- to 30-year-old lodgepole pine plantations that had previously been declared free-growing in the southern interior of British Columbia. The stands were located in six biogeoclimatic zones: Engelmann Spruce-Subalpine Fir (ESSF), Montane Spruce (MS), Interior Cedar-Hemlock (ICH), Interior Douglas-fir (IDF), Sub-Boreal Spruce (SBS), and Sub-Boreal Pine-Spruce (SBPS). Free-growing standards were no longer met on 27% of plantations, with the worst performance (70% no longer free-growing) in the Interior Cedar-Hemlock forests. Natural regeneration was common but it was half the size of lodgepole pine. Biotic damage, especially hard pine stem rusts, was the dominant factor reducing free-growing densities. Stands were at greater risk of reduced stocking where summer precipitation was higher or soil moisture regimes were wetter and where stands had been broadcast-burned prior to planting or received secondary treatments of brushing or pruning. Reforestation policies that encourage widespread planting of lodgepole pine, particularly in areas where lodgepole pine has limited natural occurrence such as in the ICH zone, should be reconsidered given that health problems are extensive and are expected to increase with climate change.Key words: Pinus contorta, lodgepole pine, free-growing, stocking, forest health, damage, disease

Influence of soil nutrients on ectomycorrhizal communities in a chronosequence of mixed temperate forests

Many factors associated with forests are collectively responsible for controlling ectomycorrhizal (ECM) fungal community structure, including plant species composition, forest structure, stand age, and soil nutrients. The objective of this study was to examine relationships among ECM fungal community measures, local soil nutrients, and stand age along a chronosequence of mixed forest stands that were similar in vegetation composition and site quality. Six combinations of age class (5-, 26-, 65-, and 100-year-old) and stand initiation type (wildfire and clearcut) were replicated on four sites, each representing critical seral stages of stand development in Interior Cedar-Hemlock (ICH) forests of southern British Columbia. We found significant relationships between ECM fungal diversity and both available and organic P; available P was also positively correlated with the abundance of two ECM taxa (Rhizopogon vinicolor group and Cenoccocum geophilum). By contrast, ECM fungal diversity varied unpredictably with total and mineralizable N or C to N ratio. We also found that soil C, N, available P, and forest floor depth did not exhibit strong patterns across stand ages. Overall, ECM fungal community structure was more strongly influenced by stand age than specific soil nutrients, but better correlations with soil nutrients may occur at broader spatial scales covering a wider range of site qualities.

The Northern Inland Temperate Rainforest of British Columbia: Old Forests with a Young History?

The inland temperate rainforest (ITR) in east-central British Columbia is marked by superlative examples of old-growth cedarhemlock forest. How long has this old-growth forest structure been a major component of this landscape? What is the biological and conservation significance of the history of this forest type? Here we present paleoecological evidence from a study in the Robson Valley of the Upper Fraser River. Sediment cores from Gerry Lake and Redmountain Lake show that western hemlock and western redcedar increased in abundance only within the last 2000 years. Thus, the old-growth forests of the northern ITR may have been present for only a few generations of trees. It is even possible, based on our preliminary evidence, that the oldest western redcedar in these stands may be the first colonizing individuals at these sites. Further paleoecological studies, including a combination of stand-age structure and pollen analysis from small lakes and forest hollows, are needed in order to understand the historical significance of these stands. A recent establishment of the ITR has implications for understanding the assembly of the modern diverse biota of the region as well as how the biota will respond to future climate change.

Influence of high-contrast and low-contrast forest edges on growth rates of Lobaria pulmonaria in the inland rainforest, British Columbia

Abstract Forested landscapes in the upper Fraser River watershed face increasing fragmentation from forest harvesting. The resultant edge effects may have a major impact on canopy lichen communities in the surrounding forest matrix. Growth rate responses of large and small thalli of Lobaria pulmonaria were evaluated in transplant experiments conducted in old-growth cedar–Hemlock forest stands located adjacent to clearcut harvest blocks (high-contrast “hard” edges) and variable-retention harvest blocks (low-contrast “soft” edges). Growth response was also assessed in transplants onto retained trees in the variable-retention harvest blocks. There was little observed difference in growth rate responses of large thalli between “hard” and “soft” edges. In fact, contrary to our initial hypothesis, growth rates of large L. pulmonaria thalli were enhanced near forest edges (25% cumulative growth rate over 2-year study period at 7.5 m from clearcut edges compared to only 17% at forest interior sites). Growth rates of large thalli were somewhat reduced at the immediate edge of clearcuts, but not of variable-retention blocks. Optimal canopy openness for growth of large L. pulmonaria thalli fell broadly between 30 and 40%, while for small L. pulmonaria thalli was closer to 30%. Growth rates of small L. pulmonaria thalli placed on “soft” edge transects were also greatest at or near stand edges and on retained trees in harvest blocks. However, in the “hard” edge transects growth rates of small L. pulmonaria thalli show little or no enhancement near edges. Repeated measures analysis of variance confirms a significant treatment effect (“soft” versus “hard” edges) for the small Lobaria thalli. These findings suggest that edge effects near clearcuts (hard edges) may have little impact on previously established large L. pulmonaria thalli. However, they also suggest that future colonization of remnant forest stands near clearcut edges by small L. pulmonaria thalli may be delayed until edge effects are moderated. The adoption of variable-retention harvesting was demonstrated to be an effective means of reducing the impact of edge effects on both large and small L. pulmonaria thalli.

Scale-dependent microhabitat selection by threatened mountain caribou (Rangifer tarandus caribou) in cedar–hemlock forests during winter

Mountain caribou, an endangered ecotype of woodland caribou ( Rangifer tarandus caribou Gmelin, 1788), live in late-successional coniferous forests where they depend largely on arboreal lichens as winter forage. While radio-telemetry has been used to understand caribou habitat selection patterns at broad scales among and within populations, here we use snow-trailing in old cedar–hemlock forests between 1992 and 2003 to study three finer scales of habitat selection: (1) forest stands used for foraging from available forest stands (among-stand selection), (2) foraging paths within selected stands relative to random paths within those same stands (within-stand selection), and (3) feeding items along foraging paths. Relative to stands that were available on the landscape, caribou selected stands with more windthrown trees and standing snags. Within stands, caribou selected paths that had more live trees, snags with branches and bark, and trees with larger diameters. All of these habitat attributes facilitate access to arboreal lichen. Of the potential forage items encountered along foraging paths, caribou preferred to feed on windthrown trees, lichen litterfall and falsebox ( Paxistima myrsinites (Pursh.) Raf.). Our results go beyond telemetry studies by revealing that not all old forests are of equal value to mountain caribou. Prioritization among old stands will help refine conservation measures, as will silvicultural systems that incorporate key habitat attributes to maintain winter habitat in low-elevation cedar–hemlock ecosystems.

Growth rate responses of Lobaria pulmonaria to canopy structure in even-aged and old-growth cedar–hemlock forests of central-interior British Columbia, Canada

The ability of cyanolichens to sustain growth in even-aged forests that develop after clear-cut harvesting is a major conservation biology concern in British Columbia's inland rainforest. This and other conservation issues have led to proposals advocating partial-cut rather than clear-cut harvesting to better maintain the structures that support biodiversity in old-growth forest stands. However, evaluating the potential impacts of alternative harvesting practices cannot occur without first understanding lichen growth responses to the existing range of natural variability in canopy structure. Using transplant experiments with thalli of Lobaria pulmonaria (a tripartite foliose cyanolichen), we evaluate growth responses to canopy structure in both naturally occurring 120 year old small-patch even-aged stands and in adjacent old-growth uneven-aged forest stands. Canopy microclimate was also measured in old-growth reference trees, allowing calculation of energy conversion efficiency for old-growth L. pulmonaria thalli. Growth rates of L. pulmonaria transplants showed a strong correlation with canopy light transmission (CLT). Mean annual lichen dry matter gain over the 2-year measurement period ranged from less than 5% on branches in closed canopy even-aged stands (<1 mol m −2 day −1 CLT) to near 20% on branches under canopy gaps in old-growth stands (>18 mol m −2 day −1 CLT). Intercepted irradiance of hydrated L. pulmonaria thalli ( I wet) under old-growth stand conditions was 24.7 and 45.5 MJ m −2 annually in years 2 and 3 of the study, resulting in an energy conversion efficiency of 1.33 and 0.61%, respectively. Open sky (gap fraction) above lichen transplants in old-growth stands was much greater than that found in even-aged stands, allowing for longer duration sunfleck events in the lower canopy of the old-growth forest stands. These findings suggest that the creation of small openings by partial-cut harvesting in the inland rainforest may result in conditions favourable to continued growth of the dominant canopy cyanolichen, L. pulmonaria. They also support existing concerns about future cyanolichen growth in even-aged forests regenerating after clear-cut harvesting.

Trade-offs between competition and facilitation: a case study of vegetation management in the interior cedar–hemlock forests of southern British Columbia

Vegetation-management practices are applied in temperate-zone forests on the assumption that changing the competitive environment between conifers and unwanted vegetation will improve conifer productivity. We review this assumption using research examining interactions between paper birch (Betula papyrifera Marsh.) and conifers in the highly productive Interior Cedar Hemlock zone of British Columbia. We have found that both competition and facilitation are important in young plantations, where paper birch competes for light, reducing growth of shade-intolerant conifers, but having a facilitative effect on shade-tolerant conifers. This facilitative effect may result from greater ectomycorrhizal diversity, population sizes of Armillaria ostoyae (Romagn.) Herink antagonistic bacteria, and associative nitrogen fixation in plantations where interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) is mixed with paper birch. Where paper birch is manually cut or girdled, conifers grow faster in diameter, but more die as a result of A. ostoyae root disease, and these responses increase with increasing weeding intensity. The weeding treatments do not affect plant community species richness but reduce paper birch dominants and increase understory structural diversity. British Columbia forest policy has been slow to respond to these findings, and we suggest that as a result, the forested landscape incurs substantial risk. We propose additional pathways for managing Interior Cedar Hemlock mixtures to ensure that the natural mix of forest types in the landscape is maintained.

Phylogenetic position of a Pacific Northwest North American endemic cyanolichen, Nephroma occultum (Ascomycota, Peltigerales)

Nephroma occultum is a COSEWIC listed cyanolichen of “Special Concern”. It is endemic to old-growth cedar-hemlock forests in western North America. This is the first study to place N. occultum into a phylogenetic framework using nucleotide sequence and secondary structure data. It also addresses the phylogenetic relationship between N. occultum and N. arcticum. Analysis of fungal Internal Transcribed Spacer (ITS) ribosomal DNA (rDNA) produced four major clades. The cyanobacterial transfer RNALeu intron (tRNALeu) from N. occultum was separated from that of N. isidiosum and fell between the Eurasian and North American epiphytic taxa. Examination of length and complexity of the folded secondary structures revealed different trends in the ITS1 and ITS2 rRNA regions. Even though N. occultum is endemic to North America, it seems more closely related to South American temperate rainforest species than to the sympatric N. arcticum. Nephroma occultum is alone among the studied species of Peltigerales in having an exceptionally long ITS1 region, and a different tRNALeu intron DNA sequence of the photobiont suggesting association with a unique genotype of Nostoc. It may be argued that the fitness of N. occultum may be influenced by the complex ITS1 RNA structure, a unique photobiont genotype undergoing a genetic bottleneck, no sexual reproduction to generate variation, and the inability to associate with different photobionts to adapt to changing habitats.

Effects of Pleistocene glaciations on population structure of North American chestnut‐backed chickadees

The postglacial recolonization of northern North America was heavily influenced by the Pleistocene glaciation. In the Pacific Northwest, there are two disjunct regions of mesic temperate forest, one coastal and the other interior. The chestnut-backed chickadee is one of the species associated with this distinctive ecosystem. Using seven microsatellite markers we found evidence of population structure among nine populations of chestnut-backed chickadees. High levels of allelic variation were found in each of the populations. Northern British Columbia and central Alaska populations contained a large number of private alleles compared to other populations, including those from unglaciated regions. The disjunct population in the interior was genetically distinct from the coastal population. Genetic and historical records indicate that the interior population originated from postglacial inland dispersal. Population structuring was found within the continuous coastal population, among which the peripheral populations, specifically those on the Queen Charlotte Islands and the central Alaska mainland, were genetically distinct. The pattern of population structure among contemporary chickadee populations is consistent with a pioneer model of recolonization. The persistence of genetic structure in western North American chestnut-backed chickadees may be aided by their sedentary behaviour, linear distribution, and dependence on cedar-hemlock forests.

Soil resources and the growth and nutrition of tree seedlings near harvest gap – forest edges in interior cedar–hemlock forests of British Columbia

Observations of tree seedlings with chlorotic foliage and stunted growth near harvest gap – forest edges in interior cedar–hemlock forests inspired a study addressing the following questions: (1) Do seedling foliar chemistry, foliar nitrogen (N) versus growth relationships, and fertilizer responses suggest N-limited seedling growth? (2) Are patterns in soil characteristics consistent with N limitation, and can interrelationships among these characteristics infer causality? Our results suggest that seedling growth near gap–forest edges was colimited by N and light availability. Soil mineral N and dissolved organic N (DON) concentrations, in situ net N mineralization, and water generally increased from forest to gap, whereas N mineralization from a laboratory incubation and total N and carbon did not vary with gap–forest position. Interrelations among variables and path analysis suggest that soil water and total soil N positively affect DON concentration and N mineralization, and proximity to mature gap–forest edge trees negatively impacts mineral N concentration and water. Collectively, our results suggest that soil N levels which limit seedling growth near gap edges can be partially explained by the direct negative impacts of gap–forest edge trees on mineral N concentrations and their indirect impacts on N cycling via soil water, and not via effects on substrate chemistry.

The ones we left behind: Comparing plot sampling and floristic habitat sampling for estimating bryophyte diversity

ABSTRACTAn efficient method for estimating bryophyte diversity in forest stands must consider more than just the dominant forest mesohabitat. We compared two methodologies commonly used for estimating diversity in forest ecosystems. Floristic habitat sampling (FHS) utilizes stratification of all forest mesohabitats, which includes the natural diversity of microhabitats found within and stratifies a mosaic of mesohabitats (e.g. forest, streams, seeps, and cliffs) and microhabitats (e.g. rocks logs, etc.) that are often not considered in forest research projects that use plot sampling to estimate species diversity. In Canadian cedar hemlock forest, FHS methodology recorded more than twice as many bryophyte species as plot sampling (PS). A comparison of the dominant forest mesohabitat concluded that plot sampling was not as efficient as FHS in estimating bryophyte diversity and that plot sampling can result in different interpretations of species diversity. Rare species ordination of stands sampled using FHS showed strong clustering of sites with respect to biogeoclimatic zones and age since the last major disturbance (fire or logging) as compared with rare species ordinations from PS data, which showed no delineation of stands along temporal gradients. Plot sampling has many useful applications in ecology, but floristic habitat sampling is more efficient for quantifying overall bryophyte diversity. FHS provides an excellent way to record a comprehensive list of species.

Retention of canopy lichens after partial-cut harvesting in wet-belt interior cedar–hemlock forests, British Columbia, Canada

Old-growth cedar–hemlock forests of the interior wet-belt of British Columbia are rich in abundance and diversity of canopy lichens, but are subject to forest harvesting. If these distinctive canopy lichen communities are to be conserved, it is important to learn how they are affected by forestry practices, including partial-cutting techniques designed to retain old-growth attributes. The retention of canopy lichens after 30 and 70% partial-cut harvesting (immediate post-harvest and 2-year post-harvest measurements) was examined using direct canopy access methods (tree climbing) in two old-growth interior cedar–hemlock forest stands of the upper Fraser River valley. Mean lichen loading was generally lower in all treatment areas, including control sites, 2 years after harvesting. However, three of four lichen-sampling groups (cyanolichen, foliose, and Bryoria group lichens) did not show significant treatment effects (total lichen loading) by harvesting type (30, 70 or 100% retention), when data sets were standardized against initial post-harvest lichen loading. Only in Alectoria group lichens were treatment effects observed. Although cyanolichen loading was not significantly different in retained trees in most harvest blocks, many thalli, especially those near south-facing edges, were discolored, suggesting that future cyanolichen loading may be lower within partial-cut harvest blocks. Litterfall in general was greater during 2001/2002 than 2002/2003, even in the control units, suggesting weather-related differences between years. For Alectoria, there appeared to be a treatment-related pulse of litterfall that was more pronounced in the 70% removal than the 30% removal treatment unit. Deposition patterns of litterfall components in relation to edges of openings indicated a heightened level of Alectoria litterfall along edges. Treatment-related differences were absent or weak in other groups, and cyanolichen litterfall did not differ between years in any study area/treatment unit combination. These findings suggest that lichen retention in the residual stand of both partial-cut treatments was adequate to meet management goals, but also point to the necessity of future monitoring, as other edge effects (e.g. microclimate changes) influence future lichen growth and mortality.

Organic and inorganic nitrogen nutrition of western red cedar, western hemlock and salal in mineral N-limited cedar-hemlock forests.

Western red cedar (Thuja plicata Donn.), western hemlock (Tsuga heterophylla Raf. Sarge) and salal (Gaultheria shallon Pursh) are the main species growing in cedar-hemlock forests on Vancouver Island, Canada. Based on the dominance of organic N in these systems, we tested the hypotheses that: (1) organic N can be utilized by the three plant species; and (2) salal, which is ericoid mycorrhizal and has high tannin concentration in its tissues, would absorb more N from the complex organic N compounds than the other two species. The abilities of cedar, hemlock and salal to take up 15N,13C-labelled glutamic acid were measured and the capacities of the three species to use nitrate (NO3-), ammonium (NH4+), glutamic acid, protein and protein-tannin N were compared over a 20-day period. Based on 13C enrichment, all three species absorbed at least a portion of glutamic acid intact. Cedar, hemlock and salal also showed similar patterns of N uptake from the NO3-, NH4+, glutamic acid, protein and protein-tannin treatments. The largest proportions of applied N were taken up from the NO3- and NH4+ treatments while smaller amounts of N were absorbed from the organic N compounds. Thus organic N was accessed to a modest degree by all three species, and salal did not have a greater capacity to utilize protein and protein-tannin-N.

Lobaria pulmonaria abundance as an indicator of macrolichen diversity in Interior Cedar–Hemlock forests of east-central British Columbia

Orographic precipitation over interior mountains has resulted in the formation of the inland temperate rainforest, where certain stands are potentially antique and support a rich flora of epiphytic macrolichens. We documented macrolichen diversity across three age-classes in forests of the Interior Cedar–Hemlock biogeoclimatic zone (i.e., ICHwk3 subzone) east of Prince George, British Columbia. Our objectives were to report changes in lichen communities with stand age, identify potential indicators of antiquity, and investigate the functional role of dominant species in the ecosystem. We identified 41 taxa, including 4 alectorioid lichens, 21 foliose chlorolichens, and 16 old-growth-associated chlorolichens and cyanolichens. Older forests supported more species than young or mature forests. The abundance of Lobaria pulmonaria (L.) Hoffm. was strongly correlated with this increase in diversity and may therefore be an appropriate indicator of stand age in the ICH. The increase in L. pulmonaria and other N2-fixing cyanolichens with stand age may have significant implications for forest nitrogen budgets in the interior of British Columbia, where atmospheric nitrogen deposition is relatively low and biological N2 fixation accounts for nearly all of the nitrogen lost to forest harvesting. We hope that this greater understanding of lichen ecology across age-classes will promote sustainable stewardship of the remaining old-growth forests of inland British Columbia.Key words: macrolichen diversity, Interior Cedar–Hemlock zone, Lobaria pulmonaria, indicator species, cyanolichens, stand age.