Calamagrostis Canadensis Research Articles

Testing restoration methods for Lake Ontario wetlands at a wetland scale

Sedges and grasses have a competitive advantage over cattails at higher elevations in Great Lakes wetlands where periodic low lake levels result in soils too dry to support cattails. Regulation of Lake Ontario water levels eliminated low lake-level years, resulting in cattail invasion. At a wetland scale at two Lake Ontario sites, we tested restoration methods by dredging channels through cattails, using spoil materials to create mounds suitable for sedge/grass growth, seeding mounds, and controlling cattails (T. × glauca) using methods adapted from experimental studies. Soil moisture and subsidence of mound soils were monitored. Vegetation was sampled pre-restoration and in shoreline sedge/grass meadow, emergent, and mound zones for two years following implementation. Although spoil mounds decreased in elevation at both sites, soil moisture increased more at the site with greater subsidence. Mean percent cover and ramet counts of cattails were reduced in sedge/grass and emergent zones at both sites. Mounds with greater soil moisture held more cattails post-construction. Across years at both sites, Carex lacustris and Calamagrostis canadensis increased in the sedge/grass meadow zone with reduction in Typha; Calamagrostis increased on the mounds. Key factors affecting results were cattail litter and, on the mounds, a second year of seeding with in situ cold, moist stratification, as well as soil moisture related to subsidence. Recommendations for future restorations include conducting more detailed soil surveys to assess potential subsidence, dredging wider and deeper channels to provide spoil for higher mounds, actively controlling invasive species, and conducting additional years of post-restoration data collection.

ОЦЕНКА ЗАГРЯЗНЕНИЯ РАСТИТЕЛЬНОГО ПОКРОВА ГОРОДА ПЕТРОПАВЛОВСКА-КАМЧАТСКОГО (КАМЧАТСКИЙ КРАЙ) ТЯЖЕЛЫМИ МЕТАЛЛАМИ В 2017–2020 гг.

In this work, we identified the content of zinc, copper, lead, and cadmium in the leaves of plants, including Artemisia vulgaris kamtschatica, Betula ermanii, Calamagrostis canadensis and Salix udensis collected from the territories of Petropavlovsk-Kamchatsky in summer 2020. Comparative analysis of changes in the accumulation levels of heavy metals in species-indicators from the urban environment, such as A. vulgaris kamtschatica and S. udensis, collected from 2017 to 2020 was provided. In general, copper content in plants from the city varied slightly over the entire investigation period. Zinc accumulation in the plants of the herbaceous and woody layers increased in 2020. The opposite trend was recorded in the accumulation of lead and cadmium for species-indicators. Their content in the vegetation cover of the city decreased by half from 2017 to 2020. In 2020, the total heavy metals pollution of plants of the herbaceous layer was assessed as weak; in previous years, it corresponded to an average degree. A similar situation was recorded for the tree layer. In Petropavlovsk-Kamchatsky, one of the most polluted sites was “Bus terminal 10 km”.

Plant Community Diversity and Tree Growth Following Single and Repeated Glyphosate Herbicide Applications to a White Spruce Plantation

Glyphosate herbicide is widely used to control bluejoint reedgrass (Calamagrostis canadensis (Michx.) Beauv.), trembling aspen (Populus tremuloides Michx.), and other competing species in regenerating white spruce (Picea glauca (Moench) Voss) plantations in Alberta, Canada. In 2004, we initiated a study to examine the effects of the aerial application of glyphosate herbicide on plant community diversity and tree growth near Calling Lake, Alberta. Four treatments were applied: (a) no treatment (control); (b) herbicide application in the first growing season after harvesting; (c) herbicide application in the third growing season after harvesting; and (d) herbicide application in the second and fourth growing seasons after harvesting (two treatments). After 11 growing seasons, species richness was not significantly affected by treatment, while Shannon and Simpson index values were highest in areas treated with herbicide in the first growing season. Herbicide treatment did not have a significant effect on the cover of bluejoint reedgrass after 11 growing seasons, but did significantly reduce trembling aspen and paper birch cover and height. Application of glyphosate in the second and fourth growing seasons resulted in the greatest reductions to aspen cover and height, as well as significant increases in spruce diameter at age 11. Simulations with the Mixedwood Growth Model indicate that all tested herbicide treatments will reduce aspen volume while increasing spruce volume at age 90, with the largest impacts evident where two treatments were applied.

Sedge/Grass Meadow Restoration on Former Agricultural Lands along a Lake Ontario Drowned-River-Mouth Tributary

Restoration of sedge/grass meadow habitat was implemented on former agricultural lands adjacent to a Lake Ontario drowned-river-mouth tributary at an elevation that historically supports this community type. Four hectares of land were disked in spring and seeded with diverse wetland mixes containing sedges, grasses, and forbs, with additional Calamagrostis canadensis (bluejoint) and Carex stricta (upright sedge) seeds added. Seedling plugs of C. canadensis and C. stricta were also planted. Mowing at a height of 45 cm to control tall, invasive annual weeds prior to seed-set was conducted as an adaptive management practice. Three years after implementation, C. canadensis and C. stricta were not found, but seeded Carex vulpinoidea (fox sedge) was dominant, and seeded Carex lupulina (hop sedge) and Carex lurida (shallow sedge) were also present. Most invasive annuals were rare, but canopies created by larger perennials may pose future problems. Although a greenhouse seed-bank emergence study was conducted, field sampling suggested that plants growing on adjacent lands were a better predictor of future plant communities, with select seeded species serving as a secondary predictor. Failure of some sedges to survive after seeding likely was not related to stratification or diurnal temperature range. However, inadequate soil moisture related to soil type and a second-year drought likely played a role, as might loss of viability of seeds during storage. Future efforts on similar lands might use fresh Carex seeds broadcast in autumn for over-winter stratification, and specially developed seed mixes could focus on species that established at the site and native species found nearby, while avoiding some potential problem species.

Canada bluejoint foliar δ15N and δ13C indicate changed soil N availability by litter removal and N fertilization in a 13-year-old boreal plantation

Canada bluejoint grass [Calamagrostis canadensis (Michx.) P. Beauv., hereafter referred to as bluejoint] outcompetes overstory tree species such as white spruce [Picea glauca (Moench) Voss] by creating a thick litter layer and competing for the available nitrogen (N). This study was conducted to investigate the effects of bluejoint litter layer (with or without litter removal) and N fertilization on soil water and N availabilities using principal component analysis (PCA) and foliar δ15N and δ13C of bluejoint in a plantation in north-central Alberta, Canada. PCA using soil properties and understory growth data demonstrated that N fertilization was more effective in changing the soil environment and resource availabilities for bluejoint growth than litter layer removal. The increase in soil N availability by N fertilization was linked with increased bluejoint foliar δ15N (by around 3‰) in fertilized plots, as a result of greater N isotopic fractionation in the fertilized plots. The more negative δ13C (by around 1‰) of bluejoint in litter layer-removed plots suggested that litter layer removal increased soil water availability, indicating that the litter layer reduced soil water availability on the site. Therefore, results from this and previous studies showed that the litter layer decreased both soil water and N availabilities. Although the exact mechanisms of the benefit of the litter layer for bluejoint remains unknown, bluejoint likely adversely impacted tree growth by competing for N due to its strong N acquisition ability under soil resource-limiting conditions.

Evaluation of a new battery of toxicity tests for boreal forest soils: Assessment of the impact of hydrocarbons and salts

The ability to assess the toxic potential of soil contamination within boreal regions is currently limited to test species representative of arable lands. This study evaluated the use of six boreal plant species (Pinus banksiana, Picea glauca, Picea mariana, Populus tremuloides, Calamagrostis Canadensis, and Solidago canadensis) and four invertebrate species (Dendrodrilus rubidus, Folsomia nivalis, Proisotoma minuta, and Oppia nitens) and compared their performance to a suite of standard agronomic soil test species using site soils impacted by petroleum hydrocarbon (PHC) and salt contamination. To maintain horizon-specific differences, individual soil horizons were collected from impacted sites and relayered within the test vessels. Use of the boreal species was directly applicable to the assessment of the contaminated forest soils and, in the case of the hydrocarbon-impacted soil, demonstrated greater overall sensitivity (25th percentile of estimated species sensitivity distribution [ESSD25] = 5.6% contamination: 10,600 mg/kg fraction 3 [F3; equivalent hydrocarbon range of >C16 to C34] Of/Oh horizon, and 270 mg/kg F3 Ahg horizon) relative to the standard test species (ESSD25 = 23% contamination: 44,000 mg/kg F3 Of/Oh horizon, and 1,100 mg/kg F3 Ahg horizon). For salinity, there was no difference between boreal and standard species with a combined ESSD25 = 2.3%, equating to 0.24 and 0.25 dS/m for the Ah and Ck horizons. The unequal distribution of soil invertebrates within the layered test vessels can confound test results and the interpretation of the toxic potential of a site. The use of test species relevant to boreal eco-zones strengthens the applicability of the data in support of realistic ecological risk assessments applicable to the boreal regions.

Fate of Naphthalene in Laboratory-Scale Bioretention Cells: Implications for Sustainable Stormwater Management

Bioretention cells are increasingly popular in low-impact development as a means to sustainably mitigate the environmental problems associated with stormwater runoff. Yet, much remains to be known regarding the removal and ultimate fate of pollutants such as petroleum hydrocarbons in bioretention cells. In this work, laboratory-scale bioretention cells were constructed inside sealed glass columns. The columns were periodically spiked with (14)C-naphthalene over a 5-month period and the fate of this representative hydrocarbon and the influence of vegetation on naphthalene fate was studied. Three column setups were used: one planted with a legume (Purple Prairie Clover, Dalea purpureum), one planted with grass (Blue-Joint Grass, Calamagrostis canadensis), and one unplanted (i.e., control). Overall naphthalene removal efficiency was 93% for the planted columns and 78% for the control column. Adsorption to soil was the dominant naphthalene removal mechanism (56-73% of added naphthalene), although mineralization (12-18%) and plant uptake (2-23%) were also important. Volatilization was negligible (<0.04%). Significant enrichment of naphthalene-degrading bacteria occurred due to contaminant exposure and plant growth as evidenced by increased biodegradation activity and increased naphthalene dioxygenase gene concentrations in the bioretention media. This research suggests that bioretention is a viable solution for sustainable petroleum hydrocarbon removal from stormwater, and that vegetation can enhance overall performance and stimulate biodegradation.

Morphological Analysis and Phytogeography of Native Calamagrostis (Poaceae) from British Columbia, Canada and Adjacent Regions

The taxonomically difficult and ecologically and phytogeographically important genus, Calamagrostis, was examined for British Columbia (BC). Morphological characters were analyzed by Principal Components Analysis (PCA) to characterize taxa and to aid in the development of a new key. Eight native species (Calamagrostis canadensis, C. lapponica, C. montanensis, C. nutkaensis, C. purpurascens, C. rubescens, C. sesquiflora, and C. stricta) are confirmed to occur in British Columbia, of which C. montanensis, C. nutkaensis, C. purpurascens, C. rubescens, and C. sesquiflora are reliably distinguishable. Comparison of species distribution to regional climatic and vegetation history suggests that Calamagrostis nutkaensis and C. sesquiflora likely survived in coastal refugia during late Wisconsin glaciations. Calamagrostis purpurascens likely persisted beyond the glacial limits or within nunataks and then spread into previously glaciated sites. Two interior continental species, C. montanensis and C. rubescens, probably spread north and west from the unglaciated zone south of the Cordilleran and Laurentide ice sheets. Calamagrostis lapponica likely persisted north of the ice sheets, and then spread southward into high-elevation sites in northern and eastern BC. Calamagrostis canadensis and C. stricta probably survived south and north of the ice sheets, and then spread into the previously glaciated terrain.

Bluejoint Stand Establishment Decision Aid

Bluejoint (Calamagrostis canadensis [Michx]. Beauv.), which is also known as Canada bluejoint grass, reedgrass, marsh reed grass, and Scribner’s reed grass, is a commonly occurring indigenous grass found throughout British Columbia. Bluejoint is a natural part of many ecosystems, but openings caused by fire, flooding, insect outbreak, windfall, timber harvesting, or other larger-scale disturbances have locally increased its abundance. Bluejoint has become a problem weed species on some sites in the northeastern part of the province. Its major impact in forestry is at the stand establishment stage where it can aggressively invade disturbed sites, inhibiting natural regeneration and impeding root and shoot development of planted seedlings. Seedling mortality is often an outcome.This Stand Establishment Decision Aid (SEDA) is a synopsis of key information forest managers in northern British Columbia will need to help understand how to mitigate the impacts of bluejoint. This SEDA describes susceptible site types, hazard ratings, bluejoint development, impacts on forest productivity, other values, and appropriate management practices. The synopsis also includes a short list of references for further reading and contact information for experts on the topic.

Wood‐feeding beetles and soil nutrient cycling in burned forests: implications of post‐fire salvage logging

Rising economic demands for boreal forest resources along with current and predicted increases in wildfire activity have increased salvage logging of burned forests. Currently, the ecological consequences of post‐fire salvage logging are insufficiently understood to develop effective management guidelines or to adequately inform policy decision‐makers. We used both field and laboratory studies to examine the effects of post‐fire salvage logging on populations of the white‐spotted sawyer Monochamus scutellatus scutellatus (Say) (Coleoptera: Cerambycidae) and its ecological function in boreal forest. Monochamus s. scutellatus adults were relatively abundant in both burned and clear‐cut logged sites but were absent from salvage logged sites. An in situ mesocosm experiment showed that the abundance of M. s. scutellatus larvae in burned white spruce bolts was linked to changes in total organic nitrogen and carbon in mineral soil. Organic nutrient inputs in the form of M. s. scutellatus frass increased mineral soil microbial respiration rates by more than three‐fold and altered the availability of nitrogen. Changes in nitrogen availability corresponded with decreased germination and growth of Epilobium angustifolium and Populus spp. but not Calamagrostis canadensis. Although the present study focused on local scale effects, the reported findings suggest that continued economic emphasis on post‐fire salvage logging may have implications beyond the local scale for biodiversity conservation, nutrient cycling and plant community composition in forest ecosystems recovering from wildfire.

Vascular Plant Communities of the Green River Lowlands in Northwestern Illinois

A few high-quality prairies still exist in the sand deposits of the Green River Lowlands. The most extensive remnants are in the Green River State Wildlife Area, Lee County, Illinois. Three upland prairie communities were surveyed; a dry sand prairie dominated by Schizachyrium scoparium, Ambrosia psilostachya, and Amorpha canescens; a dry-mesic sand prairie dominated by Sorghastrum nutans, Schizachyrium scoparium, Antennaria plantaginifolia, and Liatris aspera; and a mesic sand prairie where Sorghastrum nutans and Andropogon gerardii were the dominant grasses, and Parthenium integrifolium, Fragaria virginiana, Liatris pycnostachya, and Euthamia gymnospermoides the common forbs. The lowlands, which included approximately 325 ha, were dominated by the exotic Phalaris arundinacea, but high-quality wet sand prairie, sedge meadow, and marsh communities existed. The wet sand prairies were dominated by Spartina pectinata, Helianthus grosseserratus, and Solidago canadensis; the sedge meadows were dominated by Carex haydenii, Calamagrostis canadensis, and Persicaria coccinea; the marsh communities were divided into distinct vegetation zones. These vegetation zones were surveyed in 2002 and subjected to an extensive uncontrolled fire in 2005. Surveys completed in 2006 and 2007 were used to determine successional changes resulting from the fire. These studies suggested that most communities were returning to the species composition found before the 2005 fire.

Habitat Use by Sedge Wrens in Southern Québec

We studied Sedge Wrens (Cistothorus platensis) along transects in fens of Lake Saint-François National Wildlife Area (NWA) to identify key habitat components associated with breeding territories. Stations (0.13-ha circles centered on clusters of locations) occupied by Sedge Wrens had higher lateral visibility (lower vertical cover) and lower shrub cover (lower tall shrub density, fewer shrub stands, reduced length of stands along transects, and greater distance to the nearest shrub) compared to unoccupied stations. Mean lateral visibility was low (<25%) below 100 cm and did not differ between stations, and visibility was greater for higher height classes at stations occupied by wrens. The relative cover of dominant plant species (Carex lacustris, C. aquatilis, Lythrum salicaria, Thelypteris palustris, Calamagrostis canadensis) did not vary between stations occupied or unoccupied by Sedge Wrens. The habitat structure at the territory scale influenced Sedge Wren occupancy as birds preferred stations with lower shrub cover and higher lateral visibility. We found an average of 0.21 Sedge Wrens/ha along transects, similar to densities reported in some regions of the midwestern USA.

Sand Prairie Communities of Matanzas Nature Preserve, Mason County, Illinois

The Matanzas Prairie Nature Preserve is located near Bath, Mason County, Illinois, in the extensive glacial sand deposits associated with the Illinois River. This Preserve contains the only remaining high quality wet-mesic sand prairie, shrub prairie, and sedge meadow associated with the Illinois River sand deposits. The sedge meadow, about 5 ha in size, was dominated by Carex stricta (Importance Value or IV of 66.6 out of 200), Calamagrostis canadensis, and Rosa palustris (both with IV's of 28.3). The wet-mesic sand prairie occurred on slightly higher ground and was dominated by Solidago canadensis (IV of 34.2), Andropogon gerardii (IV of 25.9), Carex stricta (IV of 21.9), Poa pratensis (IV of 18.0), and Euthamia graminifolia (IV of 17.7). Parts of the Preserve were shrub prairie with a ground layer similar to the wet-mesic sand prairie community. A total of 340 species of vascular plants were encountered on the Preserve: 5 fern and fern-allies; 100 monocots; and, 235 dicots. Except for Poa pratensis, which was among the dominant species in the wet-mesic sand prairie and shrub prairie, the 38 exotic species were rarely encountered (11% of the flora). The Floristic Quality Index (including exotic species) for the sedge meadow was 38.80, the wet-mesic sand prairie 43.65, and the shrub prairie 31.76.

Nitrogen and Water Availabilities and Competitiveness of Bluejoint: Spruce Growth and Foliar Carbon‐13 and Nitrogen‐15 Abundance

How resource availabilities affect the competitiveness of Canada bluejoint grass [Calamagrostis canadensis (Michx.) P. Beauv., hereafter referred to as bluejoint] is poorly understood. Bluejoint is a widespread grass species in boreal forests and competes with tree species such as white spruce [Picea glauca (Moench) Voss] for belowground resources (e.g., soil N and water) when their supply is limited. In this greenhouse‐based study, we tested the following hypotheses: (i) bluejoint competition reduces white spruce growth when belowground resource availabilities are limited; (ii) greater N and water availabilities may increase bluejoint competition and its adverse effects on white spruce growth; and (iii) white spruce foliar δ13C and δ15N are affected by soil N and water availabilities and bluejoint competition. A 2 × 2 × 2 (competition × N availability × water availability) factorial experiment was conducted using pots of planted white spruce seedlings with or without bluejoint. Bluejoint competition reduced the volume index (diameter2 × height) of white spruce by 50%. The competitiveness of bluejoint appeared to be independent of resource availabilities, but bluejoint had greater growth response to increased N availability than white spruce. Bluejoint competition depleted white spruce foliar δ13C and δ15N by 1.2 and 1.2‰, respectively, even under adequate water supply, indicating that N deficiency caused by bluejoint competition had a dominant effect (increasing 13C discrimination during photosynthesis) compared with the potential effect of drought stress on foliar δ13C, and that strong NH4 uptake by bluejoint may have prevented significant soil N losses and 15N enrichment through nitrification and subsequent denitrification.

The effect of roots and litter of Calamagrostis canadensis on root sucker regeneration of Populus tremuloides

Summary Marsh reed grass ( Calamagrostis canadensis (Michx.) Beauv.) is a common, highly competitive grass native to the boreal mixedwood forest. This grass increases in abundance after clear-cut logging but little is known about its effects on trembling aspen ( Populus tremuloides Michx.) sucker regeneration. The effects of Calamagrostis sod and its litter on aspen regeneration were studied in two separate greenhouse studies. Calamagrostis sod did not affect the initiation of suckers, but resulted in 30 per cent fewer suckers emerging above the soil that were smaller and had 40 per cent less leaf area. Calamagrostis litter had little effect on the initiation and number of emerged suckers; however, it delayed emergence by 10 days. The physical barrier by roots and litter of Calamagrostis reduced or delayed the expansion of suckers and therefore prolonged their dependence on root reserves. By the time the suckers reached the surface, they had to compete for light with Calamagrostis shoots that had emerged a week earlier. This, coupled with low soil temperatures associated with Calamagrostis in other experiments, will signifi cantly reduce the number and growth of suckers. Any reduction and delay in sucker emergence will decrease aspen regeneration and productivity since the growing season in the boreal forest region is short.

Effects of understory removal, N fertilization, and litter layer removal on soil N cycling in a 13-year-old white spruce plantation infested with Canada bluejoint grass

Canada bluejoint grass [Calamagrostis canadensis (Michx.) Beauv., referred to as bluejoint below] is a competitive understory species widely distributed in the boreal region in North America and builds up a thick litter layer that alters the soil surface microclimate in heavily infested sites. This study examined the effects of understory removal, N fertilization, and litter layer removal on litter decomposition, soil microbial biomass N (MBN), and net N mineralization and nitrification rates in LFH (the sum of organic horizons of litter, partially decomposed litter and humus on the soil surface) and mineral soil (0–10 cm) in a 13-year-old white spruce [Picea glauca (Moench.) Voss] plantation infested with bluejoint in Alberta, Canada. Removal of the understory vegetation and the litter layer together significantly increased soil temperature at 10 cm below the mineral soil surface by 1.7 and 1.3°C in summer 2003 and 2004, respectively, resulting in increased net N mineralization (by 1.09 and 0.14 mg N kg−1 day−1 in LFH and mineral soil, respectively, in 2004) and net nitrification rates (by 0.10 and 0.20 mg N kg−1 day−1 in LFH and mineral soil, respectively, in 2004). When the understory vegetation was intact, nitrification might have been limited by NH4+ availability due to competition for N from bluejoint and other understory species. Litter layer removal increased litter decomposition rate (percentage mass loss per month) from 2.6 to 3.0% after 15 months of incubation. Nitrogen fertilization did not show consistent effects on soil MBN, but increased net N mineralization and nitrification rates as well as available N concentrations in the soil. Clearly, understory removal combined with N fertilization was most effective in increasing rates of litter decomposition, net N mineralization and nitrification, and soil N availability. The management of understory vegetation dominated by bluejoint in the boreal region should consider the strong effects of understory competition and the accumulated litter layer on soil N cycling and the implications for forest management.

Vector analysis of understory competition, N fertilization, and litter layer removal effects on white spruce growth and nutrition in a 13-year-old plantation

Canada bluejoint grass ( Calamagrostis canadensis (Michx.) Beauv.) is a very competitive understory species and can create a thick litter layer that may decrease tree growth in white spruce ( Picea glauca (Moench.) Voss) stands in the boreal region. We examined the effects of Canada bluejoint grass dominated understory competition, N fertilization, and litter layer removal on the nutrition and growth of white spruce, in relation to soil N availability in a 13-year-old plantation near Whitecourt, Alberta, Canada, in 2003 and 2004. We hypothesized that: (1) understory competition reduces white spruce growth as a result of competition for available N; (2) litter layer removal increases white spruce growth by increasing soil temperature and N availability; (3) N fertilization improves white spruce growth by increasing N availability. Soil gravimetric moisture content in LFH was reduced by understory competition and litter layer removal in 2003, which had a very dry summer. Understory removal increased white spruce diameter growth, 100-needle biomass, and needle N concentration and content. In 2003, N fertilization consistently increased 100-needle weight and needle N content when litter layer was removed, but decreased or did not affect those values without litter layer removal. Nitrogen fertilization increased needle N concentration in 2004. The inconsistent effects of N fertilization may be due to the short-term nature of fertilization effects and immobilization of N by organic matter. Rates of white spruce diameter growth and soil mineral N supply in 2004 were related ( R 2 = 0.65, P < 0.001). Vector analysis showed that N fertilization or litter layer removal with intact understory vegetation either increased or did not affect needle N concentration but decreased tree biomass. We conclude that understory control will benefit tree growth in young white spruce stands in the boreal region that have passed the free-to-grow stage. However, N fertilization or litter layer removal alone in bluejoint infested sites may not benefit the trees.

Dynamics of regeneration gaps following harvest of aspen stands

This study assessed the dynamics of gap development in postharvest regeneration in five stands in northwestern Alberta dominated by trembling aspen (Populus tremuloides Michx.). The pattern of gap development over time was determined from analysis of air photographs taken preharvest and 1, 4, 10, and 12 years postharvest. The area of each stand covered by gaps increased after harvest because of the addition of harvest-related gaps over and above those that had been present prior to harvest. The blocks we studied had a combined gap area of up to 29% of stand area 12 years postharvest. We measured regeneration characteristics, microsite, soil, light, and browse conditions in 30 aspen regeneration gaps (gaps in regeneration that were not gaps preharvest and were not due to obvious harvest-related disturbance) 14 years following harvest. Although deciduous trees within postharvest regeneration gaps were the same age as those outside (i.e., in a fully stocked matrix of newly established even-aged aspen stems), they were often suppressed, with significantly lower density and growth. Within the 14-year-old postharvest regenerating aspen stands, aspen height varied from 1 to 11 m; this substantial variability appeared to be largely due to the influence of browsing. There was little evidence of ongoing regeneration within postharvest regeneration gaps, indicating that these gaps will probably persist over time. This may impact future deciduous stocking and volume. It is unknown what may have initiated the formation of these gaps, although results suggest that they are not due to edaphic conditions or disease in the preharvest stands. There is evidence that bluejoint (Calamagrostis canadensis (Michx.) Beauv.) cover and browsing are important factors in the maintenance of postharvest regeneration gaps. The spatial heterogeneity resulting from gaps could be advantageous, however, either as part of ecosystem-based management emulating natural disturbance or as a template for mixedwood management, where white spruce (Picea glauca (Moench) Voss) are established in gaps.

Establishment of a Vegetation Cover on Tundra Kimberlite Mine Tailings: 2. A Field Study

Abstract High erosion potential of dewatered kimberlite mine tailings after diamond extraction has prompted research at the Ekati Diamond Mine in the Canadian subarctic heath tundra ecosystem. Greenhouse and field studies aimed at establishing a permanent vegetation cover on these dewatered tailings began in spring 2000. Coarse texture, no organic component, lack of available macronutrients, and a serpentine chemistry are the principal limitations of kimberlite tailings to plant colonization. Structure‐improving (peat moss, lake sediment, and sewage sludge) and nutrient‐providing (fertilizer, rock phosphate, calcium carbonate, and gypsum) amendments were tested to ameliorate these conditions, facilitating the establishment of a permanent vegetation cover, which stabilizes surface materials and promotes natural colonization by the surrounding tundra vegetation. Seven native grass species (Arctagrostis latifolia, Calamagrostis canadensis, Poa glauca, Poa alpina, Deschampsia beringensis, Deschampsia caespitosa, and Festuca rubra) were used to measure amendment success. With the addition of structure‐improving and nutrient‐providing amendments, plant growth on these kimberlite tailings under field conditions was significantly improved over unamended tailings material. Tailings properties, including cation exchange capacity, organic carbon, and macronutrient availability, were also improved with amendment addition.

Establishment of a Vegetation Cover on Tundra Kimberlite Mine Tailings: 1. A Greenhouse Study

Abstract High erosion potential of dewatered kimberlite mine tailings after diamond extraction has prompted research at the Ekati Diamond Mine in the Canadian subarctic heath tundra ecosystem. Coarse texture, no organic component, lack of available macronutrients, and a serpentine chemistry are the principal limitations of these kimberlite tailings to plant colonization. Structure‐improving (peat moss, lake sediment, sewage sludge, Agri‐Boost, and composted papermill sludge) and nutrient‐providing (fertilizer, calcium carbonate, gypsum, and rock phosphate) amendments were tested in the greenhouse to ameliorate these limitations, thereby facilitating the field establishment of a permanent vegetation cover, which would stabilize the surface materials and promote natural colonization by the surrounding tundra vegetation. Seven native grass species (Arctagrostis latifolia, Calamagrostis canadensis, Poa glauca, Poa alpina, Deschampsia beringensis, Deschampsia caespitosa, and Festuca rubra) were used to measure amendment success. With the addition of structure‐improving and nutrient‐providing amendments, plant growth on kimberlite tailings was significantly enhanced. Tailings properties, including cation exchange capacity, percentage of organic carbon, and macronutrient availability, were also improved by amendment addition.