ASSESSMENT OF HEAVY METALS POLLUTION IN THE PLANTS OF PETROPAVLOVSK-KAMCHATSKY (KAMCHATKA TERRITORY) IN 2017–2020

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”.

Soil and vegetation characteristics of a peatland near Lake Édouard in Mauricie National Park, Québec, Canada

The majority of plant communities within the peatland near Lake Édouard belongs to the poor fen group. They are containing poor fen species such as <i>Myrica gale</i>, <i>Carex rostrata</i>, <i>Glyceria canadensis</i>, <i>Calamagrostis canadensis</i>, <i>Carex canescens</i>, <i>Carex stricta</i>, <i>Alnus rugosa</i> and <i>Sphagnum subsecundum</i>. Members of these taxa grow in association with a group of marsh species and with <i>Chamaedaphne calyculata</i> and <i>Sphagnum majus</i>, species characteristic of bogs. The soil are of the humisol great group, being well decomposed and relatively rich in nutrient elements but ranging from extremely to strongly acidic. Four new associations are noted: <i>Sphagno-Juncetum brevicaudati</i>, <i>Sphagno-Hypericetum boreale</i>, <i>Sphagno-Glycerietum canadensis</i> and <i>Carici canescenti</i>-<i>Sphagnetum maji</i>. The distribution of vegetation appears dependent on ground relief and, consequently, on the level and quality of water in the peatland.

Late Pleistocene paleoecology of arctic ground squirrel (Urocitellus parryii) caches and nests from Interior Alaska's mammoth steppe ecosystem, USA

Botanical analyses of fossil and modern arctic ground squirrel (Urocitellus parryii) caches and nests have been used to reconstruct the past vegetation from some parts of Beringia, but such archives are understudied in Alaska. Five modern and four fossil samples from arctic ground squirrel caches and nests provide information on late Pleistocene vegetation in Eastern Beringia. Modern arctic ground squirrel caches from Alaska's arctic tundra were dominated by willow and grass leaves and grass seeds and bearberries, which were widespread in the local vegetation as confirmed by vegetation surveys. Late Pleistocene caches from Interior Alaska were primarily composed of steppe and dry tundra graminoid and herb seeds. Graminoid cuticle analysis of fossil leaves identifiedCalamagrostis canadensis,Koeleriasp. andCarex albonigraas being common in the fossil samples. Stable carbon isotopes analysis of these graminoid specimens indicated that plants using the C3photosynthetic pathways were present and functioning with medium to high water-use efficiency. Fossil plant taxa and environments from ground squirrel caches in Alaska are similar to other macrofossil assemblages from the Yukon Territory, which supports the existence of a widespread mammoth steppe ecosystem type in Eastern Beringia that persisted throughout much of the late Pleistocene.

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.

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.

The biomass and nutrient levels of Calamagrostis canadensis and Carex stricta under different hydrologic and fungicide regimes

We examined whether fungicide and the subsequent reduction of soilborne pathogenic fungi would differentially enhance the productivity and foliar nutrient content of two coexisting species, Calamagrostis canadensis (Michx.) Beauv. and Carex stricta Lam. This was tested under hydrologic regimes that simulated those in prairie wetlands and included a 32-d cycle (flooded 16 d, dry 16 d), 6-d cycle (flooded 3 d, dry 3 d), flooded, well-watered, and dry hydroperiods. Calamagrostis canadensis biomass increased 26%–45% in the wet hydroperiods (6-d cycle, well watered, and flooded) when fungicide was applied but remained fairly constant over all hydroperiods in nonfungicide treatments. Calamagrostis canadensis grown in the wet hydroperiods without fungicide produced the same biomass and growth rates as plants treated with fungicide in the dry hydrologic regime, suggesting that pathogenic fungi in wet hydrologic regimes have the same effect as major environmental stresses such as drought. In contrast, the biomass and growth rate of Carex stricta generally did not vary significantly with fungicide treatment. The only exception was in the rapidly alternating hydroperiod (6-d cycle), where Carex stricta treated with fungicide produced 48% more biomass and grew 46% faster than plants not treated with fungicide. Mean concentrations of foliar phosphorus generally were not significantly different between the fungicide and nonfungicide treatments for either plant species, while foliar nitrogen concentrations were higher in both species when treated with fungicide in the 32-d cycle, dry, and well-watered hydroperiods. The effect of fungicide on the biomass and foliar nutrients of these two co-occurring plant species depended on the species and the hydrologic regime, and our results suggest that seasonal and interannual changes in hydrologic regimes may confer a temporary advantage to one species or the other that, over the long term, allow them to coexist.Key words: benomyl fungicide, foliar nitrogen, foliar phosphorus, hydroperiod, marsh reed grass, wetland.

Competition and facilitation in mixtures of aspen seedlings, alfalfa, and marsh reedgrass

Increasing demand for aspen (Populus tremuloides Michx.) and related poplar species is generating interest in their intensive cultivation. Successful establishment of aspen plantations requires minimizing the negative effects of associated plant species. Competitive and facilitative effects were isolated in field plots containing fixed-density mixtures of aspen seedlings, alfalfa (Medicago sativa L.), and marsh reedgrass (Calamagrostis canadensis (Michx.) Beauv.) in central Alberta. Although aspen survival was unaffected in mixtures, damage to aspen leaf area was lower when grown with either herbaceous species than when grown in monoculture, possibly reflecting facilitation through plant defense guilds. Over the first two growing seasons, net competition was expressed as most aspects of aspen growth were reduced. Herbaceous species reduced photosynthetically active radiation, soil moisture, and soil N available to aspen. Moreover, relative yield totals from the species mixtures examined consistently indicated either neutral effects (combined yields equaled monoculture yields) or underyielding. Despite this, evidence of facilitation was also found when aspen was grown with alfalfa, including increases of overall available soil N and transient increases in soil moisture with pulsed precipitation during drought. These results indicate that short-term facilitative aspects of aspen–legume mixtures may be exploited through an agroforestry scheme by appropriately timed harvest of the herbaceous component. Conversely, aspen establishment has limited potential for integrated production with marsh reedgrass.