Bluejoint Grass Research Articles

Ecotoxicity of 2,4-dinitrotoluene to cold tolerant plant species in a sub-Arctic soil

Decades of live-fire training exercises have left millions of acres of military training lands contaminated with various munitions constituents such as dinitrotoluene. Those that pose a threat to higher organisms due to their toxicity and mobility in the soil are of particular concern. Plants aid in the biodegradation and phytoextraction of contaminants, and site-specific ecotoxicity determinations are critical to inform effective remediation strategy. These ecotoxicity determinations are lacking in cold-adapted plants and would be very informative for contaminated training lands in cold regions. Therefore, we conducted a phytotoxicity study to determine the median effective concentration (EC50) of 2,4-dinitrotoluene (2,4-DNT) to four native Alaskan plant species in a sub-Arctic soil at two different temperatures. Plant species investigated were white spruce (Picea glauca), field locoweed (Oxytropis campestris), bluejoint grass (Calamagrostis canadensis), and Jacob’s ladder (Polemonium pulcherrimum). Seedling emergence, fresh plant mass, and dry plant mass were used to model plant response to 2,4-DNT contamination. White spruce was most tolerant to 2,4-DNT contamination (EC50 = 130.8 mg kg−1) and field locoweed was least tolerant (EC50 = 0.38 mg kg−1). In general, Arctic plant species were more vulnerable to 2,4-DNT when compared to plant types native to temperate or tropical regions.

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.

White spruce foliar δ13C and δ15N indicate changed soil N availability by understory removal and N fertilization in a 13-year-old boreal plantation

Background and aims Canada bluejoint grass is a strong competitor for water and N against young white spruce trees in regenerating boreal forests in moist habitats. We investigated foliar δ13C and δ15N responses of white spruce to understory removal and N fertilization to infer treatment effects on soil water and N dynamics.

Allochthonous inputs from grass-dominated wetlands support juvenile salmonids in headwater streams: evidence from stable isotopes of carbon, hydrogen, and nitrogen

We used dual-isotope mixing models (δ13C/δ15N and δ2H/δ15N) in a Bayesian framework to partition allochthonous and autochthonous energy sources for salmonids in 2 headwater streams in the Kenai Lowlands, Alaska (USA). Our 1st objective was to estimate the production base for juvenile coho salmon (Oncorhynchus kisutch) and Dolly Varden (Salvelinus malma). We hypothesized that consumers would be reliant on both autochthonous (filamentous algae and periphyton) and allochthonous sources, but that autochthonous sources would dominate because of the open canopy and lower-quality litter inputs provided by the riparian wetland vegetation, primarily bluejoint grass (Calamagrostis canadensis). Our 2nd objective was to evaluate the utility of stable H isotopes for tracing energy pathways in a northern-latitude ecosystem. We hypothesized that δ2H-based models would provide more precise estimates of source partitioning than δ13C-based models because of greater source separation. Allochthonous source contributions consistently exceeded autochthonous sources for all fish species and size classes at both study sites. However, diet shifted during ontogeny, and larger Dolly Varden relied more on autochthonous sources than did smaller individuals of both species. Last, we found good correspondence and similar levels of precision between the δ13C- and δ2H-based models despite greater source separation by δ2H. Our results highlight the importance of allochthonous sources in headwater streams, and we suggest that litter inputs from grasses may be an under-appreciated subsidy to salmon production. Stable H isotopes can be an effective foodweb tracer in northern-latitude streams, but source partitioning results were not sufficiently different from stable C isotope models for us to recommend unequivocally using them to replace or enhance δ13C in similar studies.

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.

Breakdown rates, nutrient concentrations, and macroinvertebrate colonization of bluejoint grass litter in headwater streams of the Kenai Peninsula, Alaska

Grass litter can be a dominant detritus type in many streams. However, use of this C source in stream food webs often is viewed as insignificant because of its relatively slow breakdown rates and low nutritional quality. We deployed leaf packs containing senesced bluejoint grass (Calamagrostis canadensis) across a natural nutrient gradient of 6 salmon-rearing headwater streams on the lower Kenai Peninsula, Alaska. We hypothesized that litter-colonizing microbes would use dissolved stream nutrients and enhance breakdown rates, litter nutrient concentrations, and densities of macroinvertebrates across streams. Leaf-pack mass and nutrient concentrations were measured on the material at 0 (predeployment), 2, 4, 6, and 8 wk in all streams. Breakdown rates were calculated from the mass measurements with an exponential decay model. Macroinvertebrate composition and abundance were measured at 8 wk in all streams and every 2 wk in 1 stream. Breakdown rates of bluejoint litter were relatively low (20–30% mass loss over 2 mo), but similar to rates found in previous studies of senesced grass litter. Weighted regressions showed that bluejoint breakdown rates in the 6 streams were significantly (p < 0.05) related to dissolved stream nutrient concentrations (r2 = 0.94 and 0.67 for dissolved inorganic N and PO4-P, respectively), litter nutrient concentration (r2 = 0.72 and 0.96 for leaf % N and % P, respectively), total macroinvertebrates/g (r2 = 0.73), and nonmetric multidimensional scaling-axis-1 scores of macroinvertebrate community structure (r2 = 0.80). Litter nutrients changed after just 2 wk and were increasingly and significantly related to stream nutrient concentrations over time. NMS ordination showed that succession of macroinvertebrates on leaf packs from one stream followed a distinct direction over time, and a large shift in macroinvertebrate community structure occurred between weeks 6 and 8, a result potentially indicating a consumer response to microbial conditioning. The abundance and diversity of macroinvertebrate taxa using bluejoint litter provide evidence that it is an important habitat and energy pathway for consumers in headwater streams of the Kenai Peninsula. In addition, climate change has the potential to change terrestrial vegetation assemblages, which drive differences in stream nutrient concentrations in this region. If N-fixing shrubs become more abundant in the future, litter-decomposition rates will be positively affected by increases in both stream and leaf-litter nutrient concentrations.

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.

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.

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.

Use of an Aspen Overstory to Control Understory Herbaceous Species, Bluejoint Grass (Calamagrostis canadensis), and Fireweed (Epilobium angustifolium)

Abstract To enhance white spruce [Picea glauca (Moench) Voss] regeneration and growth, the potential for using an aspen (Populus tremuloides Michx.) overstory to suppress bluejoint grass [Calamagrostis canadensis (Michx.)] and fireweed (Epilobium angustifolium L) was investigated. Response to canopy opening was assessed on 10 treatments where the canopy had been incrementally opened. At the summer solstice, measurements of attenuated light were taken at 1.3 meters (breast height). Bluejoint grass and fireweed both responded with greater ground cover as the photosynthetic photon flux density increased (R2 = 0.84, P = 0.0002; R2 = 0.90, P = 0.0001; respectively). Where aspen has developed an overstory canopy, it may be possible to control competing vegetation to create favorable environmental conditions for spruce re-establishment, growth, and release while encouraging a sustainable mixedwood stand.

Effects of nitrogen on the growth of jack pine competing with Canada blue-joint grass and large-leaved aster

Biomass, leaf area, canopy photosynthesis, photosynthetic nitrogen-use efficiency (PNUE), nitrogen-partitioning ratio (NPR: ratio of nitrogen taken up by jack pine relative to two different competitor species), and nitrogen uptake (NU) of jack pine ( Pinus banksiana Lamb.) competing with large-leaved aster ( Aster macrophyllus L.) and Canada blue-joint grass ( Calamagrostis canadensis (Michx.) Beauv.) were examined at three nitrogen levels in a controlled-environment growth chamber. When grown with large-leaved aster, jack pine biomass, photosynthesis and PNUE ( p<0.001) increased as nitrogen level increased. Jack pine biomass, photosynthesis and NPR ( p<0.001) decreased as nitrogen level increased when grown with Canada blue-joint grass. At the lowest nitrogen supply level, jack pine photosynthesis decreased as competitor PNUE increased ( r 2=0.84, p<0.001). Jack pine photosynthesis decreased as NU of large-leaved aster (37.5 mg N l −1: r 2=0.75, p<0.001; 100 mg N l −1: r 2=0.86, p<0.001) and Canada blue-joint grass (37.5 mg N l −1: r 2=0.96, p<0.001; 100 mg N l −1: r 2=0.84, p<0.001) increased. NU and PNUE may play an important role in the outcome of interactions between jack pine seedlings and competing forest vegetation in newly planted stands.

Photosynthesis, nitrogen-use efficiency, and water-use efficiency of jack pine seedlings in competition with four boreal forest plant species

The objective of this study was to understand the mechanism underlying nitrogen (N) and water competition between jack pine (Pinus banksiana Lamb.) and four boreal forest species. Large-leaved aster (Aster macrophyllus L.), Canada blue-joint grass (Calamagrostis canadensis (Michx.) Beauv.), trembling aspen (Populus tremuloides (Michx.), and red raspberry (Rubus idaeus L.) were planted at a range of densities (0-8 plants/m2) with jack pine seedlings. Net photosynthesis (Pn), nitrogen-use efficiency (NUE), water-use efficiency (WUE) of each species were monitored over three consecutive growing seasons. Changes in available soil N and water were also measured. Jack pine Pn, NUE, and WUE decreased as competitor density increased, but these effects varied among species (p &lt; 0.001) and over time (p &lt; 0.001). The influence of density on jack pine Pn decreased over time for aster and blue-joint grass and increased over time for aspen and raspberry (p &lt; 0.001). At most sample times, jack pine Pn correlated with available soil N. In contrast, the correlation between jack pine Pn and soil water was rarely significant.

Light attenuation by early successional plants of the boreal forest

The influence of eight early successional plant species from the boreal forest on photosynthetically active radiation (PAR) were compared using a controlled plant competition study. Four woody (green alder, Alnus crispa (Ait.) Pursh; upland willow, Salix humilis Marsh.; white birch, Betula papyrifera Marsh.; wild red raspberry, Rubus idaeus L.) and four herbaceous (eastern bracken fern, Pteridium aquilinum L.; bluejoint grass, Calamagrostis canadensis Michx.; large-leaved aster, Aster macrophyllus L.; fireweed, Epilobium angustifolium L.) plant species were studied using an additive density experiment with jack pine (Pinus banksiana Lamb.) seedlings. The transmission of PAR through the plant canopies was measured using a line quantum sensor under six plant density treatments at the time of maximum canopy development each year. Four measures of plant abundance (planting density, actual density, projected leaf area index, and crown cover) were evaluated for their ability to predict PAR transmission through the plant canopies. Visual estimates of crown cover provided the best models each year. Vertical profiles of PAR transmission were used to compare the canopy structure among plant species and were used to refine the models. During the second growing season, increasing crown cover of bluejoint grass and large-leaved aster had the largest influence on PAR. In the third season, green alder, upland willow, and white birch (along with bluejoint grass and fireweed at the jack pine crown level) had the greatest influence on PAR. PAR measurements taken from a nearby forest for several of the plant species indicate that the models developed from our controlled experiment are reasonably applicable to naturally occurring plant populations.

Seasonal Susceptibility of Boreal Plants to Glyphosate I. Blue-Joint Grass and Black Spruce

Abstract Seasonal susceptibility and posttreatment recovery of blue-joint grass (Calamagrostis canadensis [Michx.] Beauv.) to glyphosate (N-[phosphonomethyl] glycine) were examined in a young black spruce (Picea mariana [Mill.] B.S.P.) plantation. In 1990, two rates of the herbicide (1.1 and 1.7 kg ae/ha) were applied on July 19, August 1, 15, and 29, and September 10 and 29 using a backpack sprayer. Although differences between rates were marginal, time of application strongly influenced post-treatment cover of blue-joint grass. Compared to the untreated control, glyphosate applied between August 1 and September 10 significantly reduced cover of blue-joint grass for 3 yr after treatment and increased growth of black spruce for at least 5 yr. The optimum period of glyphosate efficacy corresponded to the end of blue-joint grass's full flowering and beginning of aboveground senescence. North. J. Appl. For. 17(4):141–148.

Growth Response of Picea mariana Seedlings to Competition for Radiation

The growth response of 4-year-old black spruce seedlings (Picea mariana (Mill.) B.S.P.) to reduced radiation availability (DIFN) caused by herbaceous and woody competitors was investigated on a clay and on a loam site on a research plot in Ontario, Canada. Variability in black spruce growth was less explicable by reduced radiation availability caused by woody competitors than growth variability caused by herbaceous competitors. On the clay site, competition from fireweed (Epilobium angustifolium L.), Canada bluejoint grass (Calamagrostis canadensis (Michx.) Nutt.) and red raspberry (Rubus idaeus L. var. strigosus (Michx.) Maxim.) decreased black spruce diameter by more than 40% compared to seedlings without competition. Canada bluejoint grass and fireweed also distinctly reduced black spruce diameter performance on loam (>30%). These results are discussed in relation to the need of vegetation control.

Persistence of Toxic Activity and Recycling of Bacillus thuringiensis var. israelensis in Cold Water: Field Experiments Using Diffusion Chambers in a Pond

The persistence of the larvicidal activity of Bacillus thuringiensis var. israelensis (Bti) was tested over a five-month period in a low-temperature aquatic environment. Diffusion chambers filled with a suspension of Bti (100 mg l - 1) and different experimental substrates (pond water, periphyton, sediments and vegetation), but without mosquito larvae, were placed near the bottom of a large pond and removed at various intervals to measure residual toxic activity to mosquito larvae, spore concentration and proteolytic activity. Within the pond water substrate, 50% of the initial toxicity was still present after one month in cold water, while with the periphyton substrate, 30% remained in the liquid fraction after the same period of exposure. Within the vegetation substrate (blue-joint grass, Calamagrostis canadensis), an average of 30% of the initial toxicity was still present in the liquid fraction between day 84 to day 154. Solid fractions of vegetation became toxic very early and remained toxic for five months. At the end (day 154), there was still 54% of the original toxic activity put in the chambers associated with the vegetation samples. In the absence of mosquito larvae, spore recycling was observed in the chambers especially with sediments and vegetation. But spore recycling did not appear to play a major role in the observed persistence, but rather rapid absorption onto vegetation substrates was responsible for the persistence of Bti in a cold climate.

Influence of excess nitrogen deposition on a white spruce (Picea glauca) stand in southern Alaska

Excess N delivered to forest ecosystems has been shown to alterinternal ecosystem biogeochemical cycles, contribute to forestdecline, and negatively affect the health of receiving waters.In the vicinity of the Nikiski Industrial Complex, Kenai Peninsula,Alaska, there has been recent concern about the influence ofNH3 emissions that have occurred for over twodecades on local soils and vegetation. The study site representedan opportunity to examine the influence of elevated N depositionon a northern coniferous ecosystem in an area with a low backgroundof N deposition. Overstory vegetation in the area is dominated bywhite spruce (Picea glauca Moench. Voss) and paper birch (Betulapapyrifera Marsh.). Mortality of both species has occurred adjacent(<2 km) to the industrial complex. Average annual Ndeposition rates ranged from 0.7 to 21.0 kg ha-1 y-1in the area, with the highest rates closest to the complex. Sulfatedeposition at the site was low. Due to the high NH3deposition, precipitation near the complex was less acidic thanprecipitation in general; bulk precipitation pH ranged from 5.51to 7.06. Within 1.80 km of the facility there was an increase inKCl- and resin- extractable soil NH4+ andNO3- in the O horizon, and a decrease in soil pHcompared to soils further from the facility. Spruce near thefacility had chlorotic foliage and thinning crowns, higherconcentrations of N, but lower foliar Ca and Mg. Foliar Mglevels approached deficiency levels, but foliar Ca was wellabove reported deficiency levels at all sites. Both Mg:N andCa:N ratios, however, suggest nutrient imbalances in the highN deposition zone. Canopy death and fertilization by N appearto have encouraged growth of the native bluejoint grass. Thepresence of elevated NO3- in O horizon soilextracts, elevated NO3- in resin bags placed betweenthe O and E horizons, and nutritional imbalances in the foliagesuggest that N saturation may be occurring in soils adjacent to thefacility.

Effects of a Spruce Beetle (Coleoptera: Scolytidae) Outbreak and Fire on Lutz Spruce in Alaska

The spruce beetle, Dendroctonus rufipennis (Kirby), has had a major effect on the spruce forests of southcentral Alaska. In one area of the Chugach National Forest, 51% of the Lutz spruce, Picea glauca x lutzii Little, or nearly 90% of the commercial stand volume was killed by spruce beetles during a 16–yr period. The majority of the tree losses occurred during the first 10 yr of the outbreak. Tree species composition remained essentially the same after the outbreak. Forest structure changed with decreased tree density, and species richness declined significantly on the unburned, spruce beetle–effected plots. This reduction in plant diversity was probably a result of the significant increase, and competitive advantage, of bluejoint grass, Calamagrostis canadensis (Michaux) Beauvois, and fireweed, Epilobium angustifolium L., in the heavily beetle–effected plots. Although species richness did not change 7 yr after a prescribed fire, species composition did change. Specifically, the occurrence and percentage of blue joint and fireweed cover significantly increased.

Influence of N, P, and K Fertilization on Yield and Mineral Composition of Native Bluejoint Grass on the Lower Kenai Peninsula, Alaska1

AbstractDomestic grasses are difficult to establish and maintain in the Caribou Hills of the lower Kenai Peninsula in Alaska. Thus this 8‐year study sought to determine native bluejoint [Calamagrostis canadensis(Michx.) Beauv.] response to varying N, P, and K fertilization rates applied annually and stand persistence when two cuttings were made each growing season. A 4 × 22factorial experiment with four N rates (67,134,201, and 268 kg N/ha) and two P and K rates (84 and 168 kg P/hq 93 and 186 kg K/ha) was established on Kachemak silt loam (thixotropic over loamy, mixed Typic Cryandept) at 366 m elevation. Concentrations of NO3−N, total N, P, K, S, Ca, Mg, and Si in the plants were determined and uptake of these constituents calculated, During this 8 years with two annual harvests and with fertilization the bluejoint stand became more dense. Each increasing N rate through 134 kg/ha generally increased the annual yield. Concentrations of N03−N and total N in both cuttings and annual N uptake were increased by each increasing N increment while the Si concentration of each cutting was depressed. Significant yield interaction between N and K occurred with greater response to N or K at the higher rates of the other. Application of P increased forage yield, P, Ca, and Mg concentrations, and P, K, S, Ca, and Mg uptake. Doubling the P rate further increased these values. Potassium application increased yield, K concentration, and P, K, and S uptake. Doubling the K rate increased the yield at higher N rates and decreased Ca, Mg, and Si concentrations and uptake. Ranchers in the lower Kenai Peninsula area of Alaska can now be assured native bluejoint can be the most important forage grass to provide supplemental winter livestock feed. Persistent high yields can be maintained with less cost than with any other presently known forage.