Ericaceous Shrubs Research Articles

Recruitment and ontogenic patterns of stunting and growth release of black spruce (Picea mariana) in post-fire Kalmia heaths

Abstract Recruitment of seed regenerating plants after disturbance depends on adequate seed supply and favourable microsites that allow germination and seedling establishment (safe sites). Forest disturbance in nutrient stressed conifer-ericaceous communities in boreal and temperate forests become quickly dominated by ericaceous shrubs and restrict tree recruitment. Habitat filter due to limitation of safe sites has been attributed to inadequate seedling regeneration. Furthermore, large proportions of the regenerating seedlings exhibit stunted growth but some over time exhibit growth release. Despite wide occurrence of poor natural regeneration of conifers in ericaceous shrubs, the ontogenic patterns of stunting and growth release of conifer seedlings received little attention. We used post-fire black spruce- Kalmia ecosystems to study this. We hypothesized that (i) post-fire residual OM thickness controls seedling recruitment by limiting safe sites even in presence of sufficient seed supply, (ii) black spruce density of a site depends on its OM depth, which controls safe sites, and (iii) partially safe sites, which permit germination and seedling establishment with stunted growth, can become safe sites overtime allowing growth release. We experimentally tested black spruce seed regeneration on seedbeds with variable OM thickness and studied the ontogenic patterns of seedling/sapling growth in eight post-fire Kalmia heaths along an 8–34 year chronosequence. We found that despite ample seed supply OM depth controls seedling recruitment. In the chronosequence study we found only 17.8% of burnt area accounts for occupied safe sites, recruiting only 317 seedlings/ha and only 13% of them exhibit normal growth, others remain stunted for 5–20 yrs. With time, successive cohorts of stunted seedlings overcome growth check. Black spruce density was negatively associated with OM depth and Kalmia cover. The probability of growth release was associated negatively with OM depth and positively with soil respiration. We conclude that poor black spruce regeneration in Kalmia heath is largely due to safe site limitation controlled by OM depth, which also controls seedling stunting and growth release. The novelty of this work is the discovery of ontogenic patterns of conifer seedlings in nutrient stressed habitats. Our findings have implications for tree regeneration in other environmentally and nutritionally stressed ecosystems such as treelines.

Patterns of Early Postfire Succession of Alpine, Subalpine and Lichen-Woodland Vegetation: 21 Years of Monitoring from Permanent Plots

Field observations using chronosequences are helpful to study vegetation succession. This method allows to establish comparisons based on soil composition, stand structure, micro- and macrofossil remains from sites of different ages but on similar edaphic and topographic conditions. In the boreal forest, post-fire succession through time is triggered by climate, disturbance history (insect epidemics, fire and logging), latitude and altitude. The main objective of this research is to identify the main patterns of early post-fire succession, including similarities and differences in vegetation composition and attributes, of three contrasted ecosystems distributed along an altitudinal gradient. To do so, we have monitored the successional development of the alpine, subalpine and boreal lichen-woodland sites during the first 21 years (1991 to 2011) of post-fire sequence in eastern Canada 1991 to 2011. Each site was characterized by a different functional group that became established following fire. A rapid resurgence of ericaceous shrubs and lichens was observed in the lichen woodland and subalpine sites. Bryophyte and lichen species were not an important component of vegetation communities during the earlier stages of post-fire succession. For all three sites monitored, lichens were the last functional group to establish in the chronosequences. Herbs and mosses characterized the post-fire succession in alpine areas, the latter functional group established late in the chronosequence to cover >25% of the site after 15 years. Post-fire chronosequences in the three contrasted environments indicate that plant succession is a repetitive process often involving similar resilient plant assemblages.

The differences in carbon dynamics between boreal dwarf shrubs and Scots pine seedlings in a microcosm study

The ground level of boreal pine forests consists of a dense layer of ericaceous shrubs, herbs, grasses, mosses and lichens. The primary productivity of this forest floor vegetation is notable but the role the most common ericoid dwarf shrub plant species, Calluna vulgaris, Vaccinium myrtillus and Vaccinium vitis-idaea, play in carbon (C) cycling in these ecosystems is poorly understood. Here, we studied their C dynamics in detail using plants of similar size (age 14–19 months) in a microcosm study. We determined the full C balances of these dwarf shrubs for the first time and compared them to those of Pinus sylvestris by using long-term biomass accumulation, ¹³C pulse labelling and CO₂ exchange measurements in a controlled laboratory experiment. Pinus sylvestris had significantly higher biomass-based C fluxes than dwarf shrubs, both aboveground and belowground, but the dwarf shrubs did not differ in the biomass-based fluxes. We showed that root respiration of the evergreen ericoid dwarf shrubs was sensitive to the aboveground light conditions as belowground respiration was 50–70% higher under light compared with dark conditions. Such light-related differences were not observed for Scots pine. The observed differences in C dynamics are important in estimating the origin of belowground CO₂ fluxes and in evaluating their biological relevance. Our results improve current understanding of CO₂ sources and sinks in boreal ecosystems.

Early response of ground layer plant communities to wildfire and harvesting disturbance in forested peatland ecosystems in northern Minnesota, USA

A rare, stand-replacing fire in northern Minnesota, USA provided the opportunity to compare the effects of wildfire and timber harvesting in two peatland forest communities, nutrient-poor black spruce (Picea mariana) bogs (BSB) and nutrient-rich tamarack (Larix laricina) swamps (RTS). We found the response between the two communities and their corresponding vegetation to be highly sensitive to different types and severity of disturbance, ranging from modest shifts in ground layer vascular plants and bryophyte species abundance, to wholesale plant community transformation resulting from the removal of the upper peat surface. Fire had a positive influence on black spruce regeneration within BSB sites, particularly areas experiencing lower levels of fire severity, with seedling densities significantly higher than harvest and control areas. Our results also suggest that ecosystem recovery will be rapid after low-severity fire in these areas, given that localized areas of peat combustion created suitable microsites for black spruce seedling establishment ensuring this species will remain a component of the post-fire communities. In contrast, tamarack regeneration was only documented in harvested RTS sites. For BSB, there was spatial heterogeneity in peat consumption as a result of fire behavior interacting with varying moisture conditions throughout peat hummocks and hollows. Light to moderate burning created suitable black spruce seedbeds by reducing cover of Sphagnum moss and the dominant ericaceous shrub Rhododendron groenlandicum, and increasing the cover of pioneering mosses, such as Polytrichum strictum. In RTS sites, fire typically consumed the entire upper peat surface, resulting in homogenization of community composition and retrogression towards marsh-like conditions dominated by cattails (Typha spp.). These findings underscore the importance of accounting for post-fire microsite heterogeneity when developing silvicultural systems for emulating natural disturbance processes in conifer forests with a naturally accumulated surface peat layer. In addition, the state shifts observed in areas experiencing high severity fire suggest that increases in fire frequency and severity may create significant challenges to maintaining forested conditions in these areas, particularly in RTS.

Estimates of evapotranspiration from contrasting Wisconsin peatlands based on diel water table oscillations

AbstractEvapotranspiration rates (ET) from contrasting Wisconsin bogs (one forested bog, one open bog) were compared over 4 years by analyzing diel oscillations of their water tables. Daily rates of ET from peatlands were also compared to rates of evaporation (E) from encircled bog ponds. We hypothesized that ET would be higher in the forested bog due to the greater leaf area index of forest canopy relative to moss and ericaceous shrubs. We also hypothesized that ET in peatlands would exceed the physical process of E from encircled ponds. Field data supported the first hypothesis, but the second only proved true for the forested peatland. Daily estimates of peatland ET varied widely, ranging from ~1 to >10 mm/d; but average ET was higher in the forested peatland (4.04 vs. 3.09 mm/d; p < .01). Average ET in the forested peatland was also higher than E during summer (4.04 vs. 3.31 mm/d; p < .05); whereas in the open peatland, average ET was slightly lower than E for all measured seasons (p < .01). Methodologically, the performance of three equations used to estimate ET from daily water table fluctuations was similar. The specific yield of peat (S*y), which is a critical variable in all three equations, was found to be an exponential function of water table depth; and absent an empirically derived S*y, errors in estimates of peatland ET can be large. Given landscape composition across this northern temperate region (13% lakes, 20% peatland, and 54% upland forest) and estimates of forest ET gleaned from the literature, our findings suggest that the regional feedback of water to the atmosphere increases from open waters to peatlands to upland forest, consistent with prior observations that the biological process of transpiration dominates continental ET.

Succession changes in diversity and assemblages composition of planthoppers and leafhoppers in natural ancient peat bogs in Belarus

Succession has a strong influence on species diversity and composition of terrestrial ecosystems. Peat bogs are among them. They have a large area in Belarus compared to other Central European countries. While in several studies have analyzed the effects of succession on vegetation in peat bog ecosystems, the response of peatland insects to succession has not been investigated yet. To address this issue were sampled Auchenorrhyncha abundance and environmental parameters on the ancient and one of the largest natural peat bog along a successional gradient from the margin to the bog dome. The results provide evidence that succession of peat bogs has influence on planthoppers and leafhoppers abundance, diversity and species composition. Along the successional gradient from younger towards older successional stages an increase abundance of specialized peat bog species, chamebionts, oligophagous and monophagous was observed. On the contrary, the younger stages of natural peat bog succession offer favorable conditions to eurytopic, polyphagous and chortobiont planthoppers and leafhoppers. The highest abundance and species richness of Auchenorrhyncha were in the lagg zone followed by early stages of natural peat bog succession. The highest diversity was in the middle stages of succession. A determinant of Auchenorrhyncha diversity was the cover of ericaceous dwarf shrubs. Linear models shrub cover and number of plants species had a positive effect on planthoppers and leafhoppers diversity and a negative effect on their abundance. Amount of ericaceous dwarf shrubs within the peat bog could be as a measure of heterogeneity.

Origin, development, and impact of mountain laurel thickets on the mixed-oak forests of the central Appalachian Mountains, USA

Throughout forests of the northern hemisphere, some species of ericaceous shrubs can form persistent understories that interfere with forest regeneration processes. In the Appalachian Mountains of eastern North America, mountain laurel (Kalmia latifolia) may interfere in the regeneration of mixed-oak (Quercus spp.) forests. To verify this possibility, I conducted a dendroecology study from 2001 to 2005 in three mixed-oak stands with mountain laurel thickets to elucidate how and when the thickets originated, developed, and were impacting hardwood seedlings. At all three sites, the oldest mountain laurel dated to the 1930s when the stands emerged from a period of recurring disturbance. However, most of the mountain laurel has originated since the 1950s when the stands were generally undisturbed. More recently, insect defoliations have accelerated the development of the thickets by increasing available sunlight. A strong negative relationship exists between the percent cover of mountain laurel and the density of hardwood seedlings with 20–30% cover being sufficient to inhibit seedling establishment and survival. Perpetuating mixed-oak forests that contain mountain laurel thickets will require reducing shrub cover to less than 20–30% at the beginning of the regeneration process to help ensure adequate densities of hardwood seedlings.

Growth release of stunted black spruce (Picea mariana) in Kalmia heath: the role of ectomycorrhizal fungi and near-ground microclimate

Naturally regenerating and planted black spruce (Picea mariana (Mill.) B.S.P.) in post-fire landscapes in eastern Canada often exhibit stunted growth in the presence of ericaceous shrubs such as Kalmia angustifolia L. After a period of stunted growth, some seedlings experience a growth release, exhibiting growth rates closer to normally growing seedlings. We hypothesized that an increase in colonization of root tips by ectomycorrhizal (ECM) fungi is responsible for this release and that the percentage of root tips colonized by ECM fungi would be higher on seedlings that had a released or normally growing neighbour within close proximity. We quantified ECM fungi diversity and abundance from 255 soil cores from stunted, released, and normally growing black spruce seedlings sampled in two Kalmia-dominated sites in Newfoundland. Growth and microsite characteristics around each seedling were also measured. We found that normal and released seedlings had significantly higher proportions of ECM fungi root tips than stunted seedlings, supporting our final hypothesis; however, there was no significant difference in distance between neighbours. Soil chemical properties are thought to inhibit the vegetative spread of ECM fungi species in this particular system and are identified as an important topic for further research.

Burn Severity Dominates Understory Plant Community Response to Fire in Xeric Jack Pine Forests

Fire is the most common disturbance in northern boreal forests, and large fires are often associated with highly variable burn severities across the burnt area. We studied the understory plant community response to a range of burn severities and pre-fire stand age four growing seasons after the 2011 Richardson Fire in xeric jack pine forests of northern Alberta, Canada. Burn severity had the greatest impact on post-fire plant communities, while pre-fire stand age did not have a significant impact. Total plant species richness and cover decreased with disturbance severity, such that the greatest richness was in low severity burns (average 28 species per 1-m2 quadrat) and plant cover was lowest in the high severity burns (average 16%). However, the response of individual plant groups differed. Lichens and bryophytes were most common in low severity burns and were effectively eliminated from the regenerating plant community at higher burn severities. In contrast, graminoid cover and richness were positively related to burn severity, while forbs did not respond significantly to burn severity, but were impacted by changes in soil chemistry with increased cover at pH >4.9. Our results indicate the importance of non-vascular plants to the overall plant community in this harsh environment and that the plant community is environmentally limited rather than recruitment or competition limited, as is often the case in more mesic forest types. If fire frequency and severity increase as predicted, we may see a shift in plant communities from stress-tolerant species, such as lichens and ericaceous shrubs, to more colonizing species, such as certain graminoids.

Short-term effects of organic matter scalping on the growth and nutrition of black spruce and jack pine seedlings planted in the boreal forest

Scarification contributes to creating planting microsites for reforestation by mixing organic matter (OM) with the upper layers of mineral soil. However, on some boreal sites characterized by a thick humus layer and dominated by ericaceous shrubs, competition seems to limit the benefits of scarification. A potential solution would be to remove OM completely through scalping. The objective of our study was to compare the short-term effects of scarification and scalping on the growth of Picea mariana and Pinus banksiana on such sites. After three growing seasons, we explored the relationships between seedling growth, groups of competing vegetation species, planting depth and distance to the nearest OM accumulation. The two treatments had similar effects on these variables. Growth on plots subjected to scalping was independent from the distance to OM. Planting depth had a nil or positive effect on seedling growth. Pinus seedlings largely outgrew Picea seedlings. However, the lack of short-term difference bet...

Palaeoenvironmental change in Southern Patagonia during the Lateglacial and Holocene: Implications for forest refugia and climate reconstructions

A high-resolution palynological record from Punta Yartou, Fuego-Patagonia (53°51′S; 70°08′W), supported by lithostratigraphy, radiocarbon dating and tephrochronology, was examined to reconstruct the vegetation changes during the last glacial–interglacial transition and the Holocene. Following deglaciation from the Last Glacial Maximum sometime before c. 23,070 Cal yr BP the vegetation was initially dominated by Ericaceous shrubs and following modest climate amelioration between c. 20,480 and 14,820 Cal yr BP the environment favoured the spread of Acaena. The trend to a warmer and more humid climate was interrupted between c. 14,820 and 13,560 Cal yr BP when the vegetation community was dominated by cold tolerant herbs such as Poaceae and Asteraceae (Subfamily Asteroideae), suggesting an open treeless landscape with colder climatic conditions coeval with the Antarctic Cold Reversal. After c. 13,560 Cal yr BP a gradual rise in temperature and humidity is inferred from the colonisation of Nothofagus. A further warming and increase is inferred from the establishment of the forest/steppe ecotone by c. 12,900 Cal yr BP. The early Holocene was then characterised by increasing development of Nothofagus open canopy forest. However, between c. 8080 and 5060 Cal yr BP there was a significant reduction in the forest cover and high values of charcoal which suggest an intense arid phase leading to increased availability of dry fuel. Between c. 5060 and 2170 Cal yr BP there were centennial-scale periods of increased wetter and colder climatic conditions. The Punta Yartou record demonstrates the sensitivity of Fuego-Patagonian forest to changes in the proximity and intensity of the southern westerly winds.

Decades of habitat use reveal food limitation of Newfoundland caribou

Abstract Identifying limiting factors is fundamental to understanding and conserving mammals, yet it often requires long-term data for long-lived species. Numerical changes of migratory caribou ( Rangifer tarandus ), for example, may unfold over decades, but few studies have examined habitat use at similar timeframes. We analyzed multiple decades of habitat use by caribou in Newfoundland, Canada, coincident with their numeric growth ( r = 0.064 in 1980s, 1990s) and decline ( r = −0.099 in 2000s). We examined 2 scales: selection of land cover, based on radiotracking of 520 adult females, and diet, based on microhistological analysis of feces and age-specific tooth wear from jawbones of harvested animals. Caribou responded at both scales. In contrast to previous decades, females during the population decline used proportionally less open coniferous and closed coniferous forests, they used more shrublands (in fall and winter) and barrens, open habitats with greater vascular plant resources. Patterns of selection also changed from nonselection to avoidance of open coniferous forest and from avoidance to nonselection or preference of barrens. The proportion of dietary moss increased at the expense of deciduous shrubs, especially during spring and summer and of ericaceous shrubs, graminoids, and lichens during winter. Teeth of both sexes exhibited premature wear, likely indicative of abrasion from low-quality forages and cropping of foods near the ground. These patterns mirror other responses, including declines in calf weight, female body size, number of male antler points, herd affinities, and time spent on the summer grounds. We surmise that they reflect density-dependent forage limitation of this island population.

Prescribed burning after clearcut limits paludification in black spruce boreal forest

Paludification, the accumulation over the mineral soil of poorly decomposed organic matter mainly originating from Sphagnum spp., transforms black spruce (Picea mariana) boreal forests into forested peatlands in the prolonged absence of fire, which diminishes forest productivity. High-severity wildfires reset this process by burning the soil organic layer (SOL) and reinitiating forest succession. In contrast, low severity wildfires impact mainly the soil surface and tree layer and do not significantly reduce SOL depth. In the Clay Belt region of eastern Canada, an area prone to paludification, the current forest harvest practice (careful logging around advanced growth [CLAAG]) removes trees but has little impact on the SOL and the understorey vegetation. This is thought to further promote paludification, which consequently reduces forest productivity. Conversely, clearcut (CC) disturbs the SOL and the understorey vegetation, and is thought to favor tree growth. Furthermore, prescribed burning after clearcut (CCPB) is used as a site preparation technique, but may also be used to control paludification as it can burn part of the organic soil layer. Using a retrospective approach, our study examines three hypotheses: compared to CLAAG, CC and CCPB: (1) have positive effects on soil conditions (e.g. decomposition level and pH), (2) reduce Sphagnum spp. and ericaceous shrub cover and (3) result in enhanced black spruce growth. We sampled 22 sites in which we measured SOL characteristics (e.g. depth, decomposition state), understorey vegetation cover and black spruce growth. Compared to CLAAG, CCPB resulted in increased soil decomposition level and higher pH. CCPB also reduced Sphagnum spp. cover but not ericaceous shrub cover. Black spruce growth rate was higher following CCPB than CC, and mean dominant tree height was marginally higher following CCPB than CLAAG and CC. Our results demonstrate that CCPB is beneficial to black spruce growth, presumably through its effects on forest understorey and SOL chemistry. While not similar to a high severity fire, prescribed burning after clearcut in paludified stands on the Clay Belt emulates some wildfire effects such as increasing soil pH. We suggest that unlike CLAAG, prescribed burning after clearcut can restore black spruce stand productivity and should be considered in the context of forest ecosystem management.

Spruce grouse decline in maturing lowland boreal forests of New York

Forest succession affects species that rely on specific successional stages of forest development as core habitat. The spruce grouse (Falcipennis canadensis) is a mid-successional boreal forest obligate declining in population size and range extent in the northeastern United States. We evaluated habitat occupancy from 2002 to 2006 and we contrasted spruce grouse habitat use at multiple spatial scales to determine if advancing succession of boreal forest influenced the species’ distribution in New York from 2002 to 2012. We detected grouse at less than half (n=13) of forest patches occupied from 1976 to 1987 and at one previously undocumented patch suggesting in aggregate a 71% reduction in extent of area occupied. Spruce grouse kernel home ranges reflected a 13× greater selection for short (<6m) lowland conifer over tall (>6m) lowland conifer, a 4.5× greater selection of short lowland conifer over upland conifer, and an 8× greater selection for ericaceous vegetation over tall lowland conifer. Within home ranges, bird radiolocations revealed an 8.5× greater selection for short lowland conifer over upland conifer, a 6.6× greater selection of short lowland conifer over ericaceous vegetation, a 5× greater selection of tall lowland conifer over upland conifer, and a 4× greater selection of tall lowland conifer over ericaceous vegetation. Occupied forest patches were 75% closer to other occupied patches than were formerly occupied patches. Moreover occupied patches were 10% larger, they were characterized by 90% less Sphagnum spp., 5× greater ericaceous shrub cover, 34% greater tree density, 71% less live vegetation >6m tall, 8% less coniferous shrub cover, and contained about half of the live vegetation from 4 to 6m above the ground. Trees were 20% younger in occupied versus formerly occupied patches (x¯=43.37 [SE=41.82–44.95] versus 51.87 [SE=50.95–52.81], respectively). We also observed 17% greater importance value (i.e., IV=100×[relative basal area×relative density×relative frequency]/3) of tamarack (Larix laricina) and a 43% less balsam fir (Abies balsamea) importance value suggesting a decreased component of earlier successional species in occupied versus formerly occupied patches. We conclude that reduced size and greater isolation of remaining habitat patches as well as forest succession have contributed to spruce grouse declines in New York, processes that could be reversed through establishment of mid-successional forest patches near remaining grouse-occupied habitats.

Odd for an Ericad: Nocturnal Pollination of Lyonia lucida (Ericaceae)

Abstract Studies of pollination biology are largely diurnally biased, especially in plant species whose flowers conform to diurnal pollination syndromes. Though these syndromes can be useful in generating hypotheses regarding a species’ primary pollinators, they may also lead to incorrect assumptions. This study explores the relative contributions of diurnal and nocturnal pollination to fruit set in Lyonia lucida, an ericaceous shrub of the southeastern United States whose floral form suggests pollination by bumble bees. Floral visitation to L. lucida and pollen loads of visitors were quantified in a population of the species in Central Florida (U.S.A.), and the relative contributions of diurnal and nocturnal pollination tested. Mating system characteristics of L. lucida were also examined. Results show L. lucida flowers are visited mainly by nocturnal moths, who are capable of carrying large pollen loads, and nocturnal pollination is the primary driver of fruit set. In addition L. lucida at the study sit...

A Quarter-Century of Change Without Fire: The High-Elevation Pitch Pine Community on Panther Knob, Pendleton County, West Virginia

The Panther Knob Preserve is important in the Central Appalachians because it is the region's largest high-elevation pitch pine (Pinus rigida) community, containing numerous rare and threatened plants and animals. Plant community structure and evidence of fire in 2008 were quantified to (a) document successional changes since 1985, and (b) test the hypothesis of pitch pine regeneration failure without recent fire. Diameter at breast height (dbh) of trees and percent cover of plants within 19 plots, each 20 × 20 m, were measured. Increment borings were used to estimate stand age, and evidence of fire, such as bark charring and soil charcoal, was recorded. Mineral soil from the top 10 cm was collected to evaluate the connection between soil characteristics and plant composition. Cluster analysis of percent cover values identified four plant community types. Diameter distributions, age structure, and the presence of only seven seedlings indicated little recent pine regeneration on the plateau. Comparisons with Fleming's (1985) observations showed that pines are taller but declined in percent cover, that ericaceous shrubs are denser, and that the threatened variable sedge, Carex polymorpha, has declined. Charred woody debris, fire scars, or soil charcoal occurred at 16 of 19 sites. Plant community structure, represented by nonmetric multidimensional scaling (NMS) ordination axes, was not correlated directly with the presence of fire evidence or soil mineral nutrients (principal components analysis [PCA] axes). A new conceptual model of pine dynamics on Panther Knob is introduced. Successional pathways with and without fire are discussed in the context of management.

Reconciling Harvest Intensity and Plant Diversity in Boreal Ecosystems: Does Intensification Influence Understory Plant Diversity?

Overall demand for forest products in the boreal forest is increasing to supply growing bio-energy demands in addition to traditional forest products. As a result, there is a need to refine current forest policies to reconcile production and ecosystem function within the context of ecologically sustainable management. This study assessed understory plants' richness, evenness, and diversity in six harvested boreal black spruce-dominated stands situated on loam, sand, and peat site types 15years after the application of four harvest treatments of increasing biomass removals. Treatments included uncut, stem-only harvest, full-tree harvest, and full-tree harvest+blading of O horizon. Following canopy removal, species richness and diversity (Shannon's and Simpson's indices) increased on all soil types. The more than doubling of slash loading on the stem-only treatment plots compared to the full-tree plots led to significantly lower species diversity on loam sites; however, the reverse was observed on peat sites where the slash provided warmer, drier microsites facilitating the establishment of a broader array of species. Preexisting ericaceous shrub and sphagnum components continued to dominate on the peat sites. Compositional shifts were most evident for the full-tree+bladed treatment on all soil types, with increases in herbaceous cover including ruderal species. The results suggest that the intensification of harvesting on plant diversity varies with soil type, and these differential results should be considered in the refinement of forest biomass-harvesting guidelines to ensure ecological sustainability and biodiversity conservation over a broad suite of soil types.

A multi-proxy peat study of Holocene vegetation history, bog development, and carbon accumulation on northern Vancouver Island, Pacific coast of Canada

We present a multi-proxy paleoenvironmental study on a 10,400 cal. yr peat sequence from an ombrotrophic bog in coastal British Columbia, Canada. Pollen, non-pollen palynomorph, plant macrofossil, and physicochemical analyses (bulk density, %C, %N, δ13C, and δ15N isotopes) were used to document changes in vegetation, bog development, and carbon and nitrogen accumulation. Pollen assemblages indicate that regional vegetation in the warm, relatively dry early Holocene was mixed coniferous forest with scattered Pseudotsuga menziesii. Herbaceous peat with a C:N of ~28, combined with Nuphar microfossils and relatively high %N, suggests the presence of a herb-dominated peatland with standing water and/or bog pools. Carbon and nitrogen accumulation were at their highest during this early Holocene period at mean rates of 30.6 and 1.2 g/m2/cal. yr, respectively. By 8000 cal. yr BP and under a cooler, wetter climate, northern Vancouver Island supported Tsuga heterophylla rainforest similar to today. Decreasing relative water table, inferred from testate amoebae and fungal remains, facilitated the establishment of a Sphagnum bog by 8000 cal. yr BP with abundant ericaceous shrubs after 5000 cal. yr BP. Temporal variation in carbon accumulation rates corresponds with changes in plant functional types and hydrological conditions: rates were lowest in the early to mid-Holocene during accumulation of Sphagnum peat (7.1 g/m2/cal. yr) and increased in late Holocene ligneous peat (12.4 g/m2/cal. yr). Our multi-proxy approach not only demonstrates the overarching control of climate on bog development and carbon and nitrogen accumulation, with seasonality likely playing a major role, but also highlights the strong influence of autogenic processes at a local scale.

Wild Turkey Prenesting-Resource Selection in a Landscape Managed with Frequent Prescribed Fire

Abstract Forage and nesting cover available to female Meleagris gallopavo (Wild Turkey) prior to nesting can influence nest success. Prescribed burns commonly are conducted during the dormant season in southern Pinus (pine) forests in part to improve vegetation conditions for prenesting Wild Turkeys and reduce risk of fire-related nest failure associated with growing-season burning. However, prescribed burning during the early growing season may provide beneficial food and cover for Wild Turkeys. Therefore, we investigated the influence of fire season and frequency and vegetation characteristics on female Wild Turkey habitat selection during prenesting in a Pinus palustris (Longleaf Pine) community managed with frequent growing-season prescribed fire in North Carolina. Growing-season fire history was not predictive of prenesting habitat selection. Females selected forest stands burned during the preceding dormant season, edges of non-forested cover, and creek drainages. On our study area, ericaceous shrub...

Foliar Nutrient Concentrations and Ratios of Scrubby Flatwoods Species Change with Time After Fire

Plant nutrient stoichiometry, which regulates carbon fixation and plant growth, is often strongly affected by soil nutrient availability. Disturbances such as fire can affect the absolute and relative availability of soil nitrogen (N) and phosphorus (P), as well as biotic constraints on plant nutrient uptake and allocation. In these ways, disturbances can have strong legacy effects on plant growth by altering nutrient stoichiometry. Florida scrubby flatwoods are pyrogenic ecosystems where fires are frequent and intense, and the dominant species resprout after fire. We measured foliar N and P concentrations, nutrient ratios, and δ15N of ten species in scrubby flatwoods 1 yr, 3 yr, and 12 yr after fire to determine how fire affects nutrient stoichiometry. Across all species, foliar %N and %P decreased then increased with time after fire, and were positively correlated with each other. In contrast, foliar N:P ratios increased then decreased with time after fire. The effects of time after fire on nutrient concentrations and ratios, however, were not consistent among species. For example, %P of palmettos was highest 1 yr after fire, while %P of ericaceous shrubs was highest 12 yr after fire. Our study suggests that scrubby flatwoods may be colimited by N and P, species may be differentially limited by N and P, and species may experience greater N or P limitation depending on time after fire.