Showing papers in "American Midland Naturalist in 1995"
TL;DR: Analysis of species representation in the midwestern BBS data revealed significant biases in species representation based on habitat associations, whereas urban and shrubland/early successional bird species are overrepresented relative to other groups of bird species.
Abstract: -Life-history traits associated with midwestern breeding bird population trends were assessed using data from the North American Breeding Bird Survey (BBS). Analyses of BBS population trends by bird-habitat association, nest location and migratory strategy groups showed that grassland bird species had exhibited more extensive population declines between 1966 and 1993 than other groups of midwestern breeding bird species. Analysis of species representation in the midwestern BBS data, however, revealed significant biases in species representation based on habitat associations. Wetland bird species are significantly underrepresented on midwestern BBS routes, whereas urban and shrubland/early successional bird species are overrepresented relative to other groups of bird species. Because of these differences in species representation, additional surveys and monitoring programs are needed in order to compile a comprehensive pattern of population trends of midwestern
170Â citations
TL;DR: In this article, existing information on bird species composition, abundance and nesting sta- tus during the breeding season (May through July) was compiled for habitats characteristic of the agricultural landscapes of Iowa.
Abstract: Existing information on bird species composition, abundance and nesting sta- tus during the breeding season (May through July) was compiled for habitats characteristic of the agricultural landscapes of Iowa. Data were derived from 60 sources for 144 bird species in 20 habitats. Total numbers of breeding bird species were highest in floodplain forest (107 species) and upland forest (85), and lowest in small grains (31) and herbaceous fencerows (27). Species abundances were standardized and categorized on a scale from 0 (absent) through 5 (very abundant with >250 individual birds/census count/100 ha). Bird species abundances are lowest in some agricultural habitats (e.g., tilled row crops and small grains) and highest in narrow, strip-cover habitats (e.g., railroad rights-of-way, wooded fencerows and farmstead shelterbelts). Species abundance patterns in natural habitats (forest, marsh and prairie) are intermediate between those in agricultural and strip-cover habitats. Twenty-five species occurred only in forest habitats and 14 only in marshes. Other species selectively (through not exclusively) use tilled row crop, grassland or wooded habitats. Principal com- ponents analysis was used to assess the relative similarities in use of the 20 habitats by the assemblage of breeding birds in Iowa. Predicted numbers of nesting species increased from 18 to 93 over four landscape scenarios representing a progression from an intensively farmed row-crop monoculture to a diverse mosaic of crop and noncrop habitats. Although laborious, the approach developed in our study has been useful for standardizing and synthesizing a diverse literature in efforts to conduct ecological risk assessments for farmland birds. It can also provide valuable baseline data for landscape-level research.
165Â citations
TL;DR: Year-round foraging of white-tailed deer on the Southern Appalachian mountains in Georgia, North Carolina and Tenessee was determined by analysis of rumen samples from 581 deer taken over 5 years and by sampling forage availability and evidence of browsing in selected habitat types.
Abstract: Year-round foraging of white-tailed deer (Odocoileus virginianus) on the na- tional forests of the Southern Appalachian mountains in Georgia, North Carolina and Ten- nessee was determined by analysis of rumen samples from 581 deer taken over 5 years and by sampling forage availability and evidence of browsing in selected habitat types. Spring and summer diets consisted mainly of green leaves and succulent twig tips of deciduous woody plants (58% in spring, 54% in summer). These forages were more abundant and used more intensively by deer in and around clearcuts than in adjacent older forests. Most other im- portant foods in these seasons (i.e., fruits, forbs and fungi) also were much more abundant in the clearcuts. Flowers of yellow-poplar (Liriodendron tulipifera), which dominated the diet in late May and earlyJune, and squawroot (Conopholis americana), a parasitic herb associated with red oaks ( Quercus spp.) and an important secondary food throughout most of the spring and summer, were more available in older forests. Fall and winter diets were influenced greatly by the availability of mast, especially acorns. When mast was abundant, it dominated the diet. When mast was scarce, deer fed mainly on the leaves of broadleaf evergreen woody plants, especially rosebay rhododendron (Rhododendron maximum). Twig ends were used little by deer during fall and winter. Older forests generally provided best foraging conditions for deer in fall and winter, being the primary source of mast and also producing about the same quantity of broadleaf evergreen foliage as clearcuts. Clearcuts and older forests provide complementary benefits to deer. Forests of intermediate age (after crown closure reduces browse availability and before onset of significant mast production) contribute much less to the deer forage resource than either clearcuts or older forests. Specific contributions of different forest age classes to the forage base vary with site characteristics. Implications of changing forest management policy are discussed.
112Â citations
TL;DR: Two adult coyotes could successfully kill calf and adult elk when there was deep snowcover and the prey was in poor nutritional condition and the predator led the attack in eight of nine observations.
Abstract: -Direct observations of coyote (Canis latrans) predation on large wild prey are rare. We observed nine predation attempts by coyotes on deer (Odocoileus virginianus) and elk (Cervus elaphus) during winter in Yellowstone National Park, Wyoming. Coyotes were successful in five attempts. The alpha male coyote led the attack in eight of nine observations. Snow depth was significantly deeper during successful kills compared to unsuccessful attempts. Two adult coyotes could successfully kill calf and adult elk when there was deep snowcover and the prey was in poor nutritional condition.
112Â citations
107Â citations
TL;DR: This research suggested that most seeds are dispersed in a nondormant condition, and this invasive shrub can establish seedlings throughout a wide range of light environments in eastern deciduous forests.
Abstract: -Successful invasion of eastern deciduous forests by the exotic shrub Lonicera maackii (Rupr.) Maxim. is well-documented, but little is known about seed germination or seedling establishment in this species. Our research suggested that most seeds are dispersed in a nondormant condition. After 88 days, mean cumulative germination percentages of untreated seeds ranged from 54-81% in light and from 31-55% in dark. Seedling density and light availability declined in parallel along transects extending from forest edges to forest interiors. Mean seedling densities ranged from 5-328 seedlings/mi2. Gap formation in forest interiors was not as conducive to seedling establishment as was the presence of edges. Still, this invasive shrub can establish seedlings throughout a wide range of light environments in
105Â citations
76Â citations
TL;DR: Leaf processing rates were among the highest observed for any North American stream, which may be related to high microbial activity at summer water temperatures, good nutritional status of fresh leaves, and abundant macroinvertebrates.
Abstract: -Processing of leaves of five riparian plant species [sugar maple (Acer saccharum), speckled alder (Alnus rugosa), eastern hemlock (Tsuga canadensis), red-stem dogwood (Cornus sericea) and sweet gale (Myrica gale)] was studied during the summer in a northern Michigan stream. In June 1992, dried green leaves (-5 g) of each species were placed into coarse-mesh bags and tethered in a riffle. Mass loss and macroinvertebrate colonization were measured after 2, 14, 28 and 42 days. In general, decay rates were fast (k = 0.017 0.134), with most species losing >80% of mass within 28 days. The order of decomposition (in declining rate) was: maple = dogwood > alder > sweet gale = hemlock. Macroinvertebrate numbers in the leaf packs were highest at 14 days, but densities per unit remaining mass increased steadily during the experiment. Midge larvae (Diptera: Chironomidae) and netspinning caddisflies (Trichoptera: Hydropsychidae) comprised 54% and 44%, respectively, of the macroinvertebrates, which generally lacked typical shredder taxa. Of several measurements of leaf chemistry, toughness and morphology, leaf surface area per unit mass was the best predictor of processing rate. Hemlock and sweet gale may contain secondary compounds that inhibit decomposition. Leaf processing rates were among the highest observed for any North American stream, which may be related to high microbial activity at summer water temperatures, good nutritional status of fresh leaves, and abundant macroinvertebrates. Summer inputs of leaves to woodland streams are transient but possibly important energy resources for some stream organisms.
73Â citations
TL;DR: The amount of open sand habitat at a site is identified as the only variable having a significant positive relationship with both plant density and seed production, suggesting that the lack of interspecific competition in open sand gaps helps define P basiramia microhabitat.
Abstract: -Density and reproductive output in relation to fire, open sand, and other site factors were determined for Polygonella basiramia. This federally endangered species is endemic to only three ridges in central Florida and found primarily in rosemary (Ceratiola ericoides) dominated sand pine (Pinus clausa) scrub. Twenty-two sites ranging from 5 to >26 yr postfire were sampled. Site factors of openness, time since last fire, dominant species, ground cover, elevation and soil type were examined. Multivariate analyses identified the amount of open sand habitat at a site as the only variable having a significant positive relationship with both plant density and seed production. Seed production actually increased with conspecific density, suggesting that the lack of interspecific competition in open sand gaps helps define P basiramia microhabitat. Open sand habitat is critical in the life history strategy of this obligate-seeding, perennial herb in a community where it must compete with larger, resprouting shrubs and herbs both immediately after fire and during fire-free inter-
69Â citations
TL;DR: The spread of Alliaria officinalis and Glecoma hederacea, the most frequent exotic species, was inhibited by forest fragmentation, and species richness of exotics followed a similar pattern.
Abstract: -The objective of this study was to investigate specific effects of disturbance on exotic species in floodplain environments and to provide baseline data on the abundance of exotic herbs in the Potomac River floodplain. Frequency of exotics generally increased with man-made disturbance (forest fragmentation and recreational use of land) and decreased with increasing flooding frequency. Species richness of exotics followed a similar pattern. Some variation was found in individual species' responses to disturbance. The spread of Alliaria officinalis and Glecoma hederacea, the most frequent exotic species, was inhibited by forest fragmentation.
61Â citations
TL;DR: Host fishes for all four mussel species were fast-water species occupying the same riffle habitats as the mussels, and all four species exhibited high degrees of host specificity in laboratory tests.
Abstract: -Fish hosts were identified for glochidia of four freshwater unionid mussel species, Epioblasma brevidens, E. capsaeformis, E. triquetra and the endangered mussel, Quadrula intermedia, from the Powell River of the upper Tennessee River drainage. All four species exhibited high degrees of host specificity in laboratory tests. Host fish for Epioblasma spp. were restricted to a cottid, the banded sculpin (Cottus carolinae) and several percids: the greenside darter (Etheostoma blennioides), wounded darter (E. vulneratum), redline darter (E. rufilineatum), snubnose darter (E. simoterum), logperch (Percina caprodes) and dusky darter (P sciera). Fish hosts identified for Q intermedia were two cyprinids, the streamline chub (Erimystax dissimilis) and blotched chub (E. insignis). Host fishes for all four mussel species were fast-water species occupying the same riffle habitats as the mussels.
TL;DR: Results suggest that many scrub species responded similarly to aboveground biomass removal and the consequent structural and microclimatic conditions across these disturbance types, and Mechanical biomass removal may be a suitable ecosystem management practice where burning is impractical.
Abstract: We hypothesized that clear-cutting mimics natural high-intensity disturbance by wildfire followed by salvage logging in sand pine scrub, and tested whether vegetation adapted to recovery from fire would respond similarly to another type of biomass removal. We measured plant community composition and structural characteristics in three replicated disturbance treatments and in mature sand pine forest (MF). Treatments were: (1) high- intensity burn, salvage logged and naturally regenerated (HIBS); (2) clear-cut, roller- chopped, and broadcast-seeded (RC); and (3) clear-cut and bracke-seeded (BK). All treat- ments were sampled 5-7 yr postdisturbance. Nonwoody plant species richness and diversity were significantly lower in MF than in disturbance treatments. Ruderal species were more abundant in HIBS and RC, but not to the exclusion of the characteristic suite of native scrub species. Shrub richness and diversity did not differ, but some species responded differently among treatments. Differences may be due to season of disturbance or rhizome depth (e.g., Serenoa repens (Bartr.) Small vs. Sabal etonia Swingle ex Nash.). Oak stem density was signif- icantly lower in HIBS and RC. Most structural characteristics were similar in HIBS, RC and BK but differed from MF. Results suggest that many scrub species responded similarly to aboveground biomass removal and the consequent structural and microclimatic conditions across these disturbance types. We suggest that plant resiliency traits, which evolved in re- sponse to the selective pressures of high-intensity disturbance and harsh environmental con- ditions, confer resiliency to human-caused disturbance as well. Mechanical biomass removal may be a suitable ecosystem management practice where burning is impractical. Due to the absence of a "virgin" (unsalvaged) burn treatment or pretreatment data and the short-term scope of this study, interpretation of results should be made with caution.
TL;DR: Most incoming spiders were apparently unable to reproduce on the Pumice Plain, which thus became a reproductive sink for their taxa, and aerial dispersal is of prime importance in recolonization of devastated terrain, and its extent in other situations has been underestimated.
Abstract: -The 1980 eruption of Mount St. Helens created a large area (the Pumice Plain) which initially lacked any resident arthropods. From 1981-1986, ballooning spiders made up over 23% of windblown arthropod fallout and contributed 105 individuals per m2 (91 mg dry biomass) over 1 summer. The family Lycosidae included 49% of all specimens but only 9% of all species; Linyphiidae included 34% of specimens and 50% of species. The 125 spider species taken varied widely in ballooning phenology. By 1986, six species (the lycosids Pardosa wyuta and P lowriei and the linyphiids Erigone dentosa, E. aletris, E. capra and Walckenaeria pellax) had established reproducing populations on the Pumice Plain, almost entirely at sites already colonized by vegetation. Successful colonists showed distinct phenological patterns (compared to subpopulations composed entirely of immigrants) and, in Pardosa, direct evidence of reproduction (egg sacs and progeny). Most incoming spiders were apparently unable to reproduce on the Pumice Plain, which thus became a reproductive sink for their taxa. Aerial dispersal is of prime importance in recolonization of devastated terrain, and its extent in other situations has been underestimated.
TL;DR: Prescribed burning can be used to expand population sizes of Silene regia by increasing fecundity and recruitment, and burning had the greatest positive effects on reproductive output.
Abstract: -The prairie forb Silene regia is restricted to small isolated populations in the eastern part of its range. I examined factors that limit fecundity and germination in these small populations. Although S. regia flowers rarely self due to dichogamy, geitonogamous crosses demonstrated self-compatibility. Substantial fruit production required pollination by ruby-throated hummingbirds (Archilochus colubris). Exclusion of hummingbirds (but not most insects) sharply reduced fruit production and seed numbers. Resource competition within individual inflorescences limited percent fruit set in some populations in certain years. Clipping of neighboring vegetation and watering S. regia did not increase reproductive output significantly. Silene regia seedings emerged at low rates (<5%) in field experiments, but field emergence increased twoto three-fold with soil disturbance and burning. Natural recruitment of seedlings occurred only in burned sites. Of all factors examined, burning had the greatest positive effects on reproductive output. In addition, controlling for the effects of burning, reproductive output was greater for plants in larger than smaller populations. By increasing fecundity and recruitment, prescribed burning can be used to expand population sizes of Silene regia.
TL;DR: Road construction modified the hydrology of a permanently flooded southeastern backwater swamp and resulted in significantly higher water levels upstream of the road, resulting in growth of trees in the upstream area was accelerated for several years followed by a long-term decline.
Abstract: -Altering the hydrologic regime of a wetland forest may result in changes in tree growth, as hydrology is a primary factor influencing the growth of wetland trees. Road construction, a common cause of altered hydrologic regimes, modified the hydrology of a permanently flooded southeastern backwater swamp and resulted in significantly higher water levels upstream of the road. Following construction, upstream water levels averaged 85 cm, whereas downstream water levels were believed to be relatively unchanged at 22 cm. Study areas were selected upstream and downstream of the road. Increment cores were taken from canopy baldcypress trees Taxodium distichum (L.) Rich., to determine if the change in hydrologic regime was reflected in the annual growth rings. Before road construction, annual growth patterns were similar at the two sites. Following construction, annual growth patterns in trees below the road were unchanged; however, growth of trees in the upstream area was accelerated for several years followed by a long-term decline.
TL;DR: Multiple regression analysis showed significant positive correlation between understory diversity and tree seedling diversity and soil subgroup, and slope aspect, soil rooting depth and number of standing dead trees were significantly negatively correlated with understory Diversity.
Abstract: The purpose of this study was to determine the most important nonanthropogenic factors affecting understory (herbs, shrubs and low-growing vines) diversity in forested landscapes of southern Indiana. Fourteen environmental variables were measured for 46 sites. Multiple regression analysis showed significant positive correlation between understory diversity and tree seedling diversity and soil subgroup. Slope aspect, soil rooting depth and number of standing dead trees were significantly negatively correlated with understory diversity. Mesic sites were more diverse in common understory species than xeric sites but had lower total cover and different species.
TL;DR: Monitoring of adult brown trout in two streams found habitat and cover influenced by beaver activity were used in excess of their abundance, whereas in South French Creek, sites with coarse woody debris were used disproportionately.
Abstract: -Positions of 51 adult brown trout in two streams were monitored to evaluate habitat use from mid-June to early December 1991 using radio telemetry. Nearly all brown trout occupied more-than one location during the study. Brown trout tended to occupy habitats in deep water near the bank and close to cover. In Douglas Creek, habitat and cover influenced by beaver activity were used in excess of their abundance, whereas in South French Creek, sites with coarse woody debris were used disproportionately. Measures of water velocity did not consistently distinguish used from available habitats, and the importance of water velocity may have been overshadowed by selection for overhead cover.
TL;DR: The fitness cost of a chloroplast gene encoding triazine resistance was estimated in jimsonweed by growing resistant and susceptible plants from germination to maturity in the field, with and without a neighbor planting of maize, suggesting that crop interference may be a useful tool for selecting against triazine-resistant weeds.
Abstract: -Fitness costs of herbicide resistance are incompletely known, but may be exploited to prevent or manage evolution of herbicide-resistant weeds. The fitness cost of a chloroplast gene encoding triazine resistance was estimated in jimsonweed (Datura stramonium L.) by growing resistant and susceptible plants from germination to maturity in the field, with and without a neighbor planting of maize (Zea mays L.). Resistant types produced 57% of total aboveground biomass production and 42% of reproductive biomass production of susceptible types. The cost of resistance was distinctly increased by the presence of maize, suggesting that crop interference may be a useful tool for selecting against triazine-resistant weeds.
TL;DR: Estimation of the abundance of birds at three landfills in northern Ohio from May 1991-July 1992 recording 699,350 individuals of 42 species found gulls (Larus spp.) comprised 94.5% of the birds recorded followed by European starlings and turkey vultures.
Abstract: -^^ estimated the abundance of birds at three landfills in northern Ohio from May 1991-July 1992 recording 699,350 individuals of 42 species. Gulls (Larus spp.) comprised 94.5% of the birds recorded followed by European starlings (Sturnus vulgaris, 5.0%) and turkey vultures (Cathartes aura, 0.3%). Gulls were primarily of two species, ring-billed (L. delawarensis, 74.49%) and herring ( L . argentatus, 25.50%). The mean number of gulls per observation during July-January was at least five times the mean number observed during other months. The combined monthly mean number of gulls at the three landfills peaked in August (>4000 birds), with gulls virtually absent in February. Total numbers, species composition and age composition of gulls varied seasonally in response to breeding, foraging and migratory behavior of local and regional populations. More than 98% of gulls observed were recorded on or within 30 m of the ground. A mean of one ? 17 (SD) gulls per observation were observed soaring at >300 m elevation over the landfills. Species composition and seasonal abundance of birds varied considerably among the three landfills, even though they were operated similarly and were in close proximity to each other. To adequately assess the use of landfills by gulls and other birds, studies lasting 2 1 year are required. Furthermore, the results from one landfill cannot necessarily be extrapolated to other landfills in
TL;DR: A demographic study of 544 genets on currently climbed, previously climbed and unclimbed dolomitic cliffs in NW Illinois indicated that position on the cliff face was the most significant factor affecting growth, and climbing appeared to skew the population structure.
Abstract: -Solidago sciaphila is an endemic goldenrod, restricted to dolomite or sandstone cliffs in and near the driftless region of the upper Midwest. A demographic study of 544 genets on currently climbed, previously climbed and unclimbed dolomitic cliffs in NW Illinois indicated that position on the cliff face was the most significant factor affecting growth. Seventy percent of all plants grew within 3 m of the cliff top, an area that comprised only 18% of the cliff face. Within the upper cliff zone, rock climbing significantly reduced Solidago density. Cliffs that were actively climbed had few genets in the upper 3 m, averaging 3.2/M2, while unclimbed cliffs and cliffs not climbed for 2 yr supported 14.2/M2 and 12.0/ i2, respectively. Basal area/M2 and flowering ramet production/m2 were significantly lower, and inflorescence length nonsignificantly lower, on currently climbed cliffs, due to the lower genet density. In the lower cliff zone (>3 m from the top) genet density was low (0.2-2.1/ m2) on all cliffs, regardless of climbing intensity. On climbed cliffs > 50% of flowering ramets were broken, significantly more than the 15% broken on unclimbed cliffs. Broken flowering ramets produced 22% of total inflorescence length on the currently climbed cliffs (compared to <5% on unclimbed and previously climbed cliffs), resulting in total inflorescence production statistically similar to, but lower than, that on unclimbed and previously climbed cliffs. Two years after cessation of climbing, Solidago in the upper zone of the previously climbed cliffs had similarly high density, basal area, ramet production and inflorescence production as on unclimbed cliffs. Climbing appeared to skew the population structure, favoring survival of large flowering genets and inhibiting survival of smaller nonflowering genets. This difference largely disappeared on cliffs unclimbed for 2 yr. To protect Solidago sciaphila, it is necessary to protect the entire cliff face, with highest priority given to the upper 3 m.
TL;DR: The seedling emergence method was used to evaluate the influence of the dominant vegetation (herbaceous, shrubby, forested) and the surrounding landscape on seed bank composition in seven Carolina bays to illustrate the potential contributions from surrounding landscape units to bay seed banks.
Abstract: -We used the seedling emergence method to evaluate the influence of the dominant vegetation (herbaceous, shrubby, forested) and the surrounding landscape on seed bank composition in seven Carolina bays. Landscape influence was evaluated indirectly by determining whether seed banks in wetlands close to clearcuts had more upland weedy species than those farther from clearcuts. Seed bank species composition and richness differed among forested, shrubby and herbaceous bays. DECORANA ordination identified a gradient of species composition from herbaceous bays, to shrubby bays, to forested bays. Bays near clearcuts had significantly more upland weedy species in their seed banks, with bays 20 m from clearcuts containing 79% more weedy species on average than bays 100 m from clearcuts. Within a bay, drier vegetation zones had 2.4 times more weedy species than did deep water zones. These results illustrate the potential contributions from surrounding landscape units to bay seed banks and highlight the need for further studies directly assessing the impact of adjacent clearcuts on bay vegetation dynamics.
TL;DR: Small home range size and high home range overlap suggest that the Cincinnati population may have switched from territorial behavior to a hierarchical dominance system, possibly in response to unique pressures (high lizard densities, high predation pressures and low availability of preferred habitat) in the Cincinnati area.
Abstract: -A 2-yr field study of introduced wall lizards, Podarcis muralis, revealed a resident population which remained remarkably stable (n = 37 lizards for each year). Slightly more than half of the 167 wall lizards originally captured and marked disappeared from the study sites and were classified as nonresidents. Males occupied significantly larger home ranges than females and, in 1991, had higher instances of intersexual home range overlap than did females. Instances of female-female home range overlaps in 1991 were more numerous than corresponding overlap between males. There was no difference between the sexes with respect to mean percentage of home range overlap in 1990, but females exhibited greater percent overlap in 1991. Small home range size and high home range overlap suggest that the Cincinnati population may have switched from territorial behavior (reported for European populations) to a hierarchical dominance system, possibly in response to unique pressures (high lizard densities, high predation pressures and low availability of preferred habitat) in the Cincinnati area. We interpret our results in light of recent findings regarding lizard spacing patterns, optimality theory and predictions concerning introduced lizard populations. We also compare our data on one of the only successfully introduced lacertid lizards in North America to data from native European populations.
TL;DR: A study of resident lizards on a 150 X 150 m grid revealed that one lizard species (Holbrookia maculata) has essentially been eliminated in 15 yr (from a maximum of 74 residents in 1979 to three residents in 1993), and a second lizard population (Sceloporus undulatus) has declined from 56 residents in1979 to less than 30 residents in1993.
Abstract: -Since removal of cattle from Arapaho Prairie in 1977, secondary succession has resulted in increased vegetation cover. Studies of resident lizards on a 150 X 150 m grid revealed: (1) one lizard species (Holbrookia maculata) has essentially been eliminated in 15 yr (from a maximum of 74 residents in 1979 to three residents in 1993); (2) a second lizard population (Sceloporus undulatus) has declined from 56 residents in 1979 to less than 30 residents in 1993; and (3) preferred microhabitats occupied by lizards have not changed, but their microgeographic distributions have shifted to areas of blowouts, and home ranges have decreased.
TL;DR: Cluster analysis indicated that the most common vegetative community supporting Platanthera praeclara was dominated by Poa pratensis L. and Juncus balticus Willd.
Abstract: I n 1987, 160 individual Platanthera praeclara Sheviak and Bowles were permanently marked on 16 transects on the Sheyenne National Grassland, in southeastern North Dakota. They were located on five sites that represented five management regimes: (1) grazed-rotational; (2) grazed-season long (5.5 mo); (3) ungrazed; (4) ungrazed and burned, and (5) grazed and burned. By 1994, only 4% of the originally marked Platanthera praeclara individuals were observed; however, numbers did not differ (P = 0.13) among sites. Beginning in 1990, all Platanthera praeclara individuals in belt transects on each site were marked and counted, and demographic data were recorded. Total orchid density differed (P = 0.04) among sites, but not with a consistent pattern among years (P = 0.001). In some years, Platanthera praeclara density was positively correlated with surface soil moisture. Preliminary demographic analyses indicate that Platanthera praeclara may be short-lived and that absent plants rarely reappear. Cluster analysis indicated that the most common vegetative community supporting Platanthera praeclara was dominated by Poa pratensis L. and Juncus balticus Willd., although Platanthera praeclara density on the Sheyenne National Grassland was most highly correlated with cover of Calamagrostis stricta (Timm.) Koel.
TL;DR: Low light levels and allelopathic effects may interact and contribute to the persistence of Myrica thickets limiting root growth of invading P taeda seedlings, thereby reducing competition for space, soil moisture and nutrients.
Abstract: -Pinus taeda naturally invades Myrica cerifera thickets as the shrub community succeeds to a maritime forest on southeastern USA barrier islands. Potential mechanisms supporting the persistence of M. cerifera thickets on barrier islands were examined in an environmental chamber. The inhibitory effects of allelochemicals from M. cerifera leaf litter and the soil in which it grows, and the interaction between allelochemicals and light intensity were quantified for seed germination and seedling growth of P taeda. Germination of P taeda seeds was significantly reduced by treatment with leachate from dead M. cerifera leaves, but light level had no significant effect. In contrast, root, shoot and total seedling growth were significantly lower under low light (44 Rmol m-2 sec-1). Root growth under high light (300 Rmol m-2 sec-1) was significantly lower for P taeda seedlings grown in soil collected from beneath Myrica thickets. Both root and shoot growth of P taeda in Myrica soil were significantly higher in the presence of Myrica leaf litter in high light. Thus, litter accumulation may assist P taeda in invading Myrica thicket gaps, possibly by counteracting allelopathic effects of Myrica root exudate. Low light levels and allelopathic effects may interact and contribute to the persistence of Myrica thickets limiting root growth of invading P taeda seedlings, thereby reducing competition for space, soil moisture and nutrients.
TL;DR: In this article, the authors used a geographic information system (GIS) to determine county-wide witness tree distributions and autecological relationships among 14 major tree species and soil wetness and texture, in this geologically and edaphically diverse region of northern Michigan.
Abstract: -Soils data and data on the presettlement forests of Baraga County, taken from the General Land Office (GLO) Survey, were stored and analyzed in a geographic information system (GIS). The purpose of the research was to determine county-wide witness tree distributions and autecological relationships among 14 major tree species and soil wetness and texture, in this geologically and edaphically diverse region of northern Michigan. In all, 12,760 trees were coded by species, location and diameter from the GLO data, which were recorded between 1846 and 1853. Tree data were overlain on soil mapping units which were coded by natural drainage class and particle-size family. All trees located in mapping unit complexes (two or more soil types) or within 25 m of certain soil boundaries were eliminated from further consideration through a selection/buffering procedure leaving 6210 trees of 14 species for use in the analysis. Contingency tables were calculated to assess the strength and direction of the relationships between each tree species and soil texture, soil wetness and texture/wetness combinations. County-wide distributions of species were strongly related to soil patterns, with a prominent forest ecotone occurring near the boundary between two distinct till provinces. Most upland forests were dominated by sugar maple and yellow birch; prevalent lowland species included balsam fir, black spruce and white cedar. Hemlock was common only near Lake Superior on sandy tills that lacked a silt cap. Especially notable was the association between a nearly pure stand of jack pine and the dry sandy soils of the Baraga (glacial outwash) Plains. Evidence for widespread disturbance by wildfires on the level plains contrasts with the relatively long period of only small gap-scale disturbances that existed on more rolling, mesic and wet sites.
TL;DR: No significant interactions between flooding and maternal hydrologic conditions were found that would indicate genetic differences in flood response between wet and dry site seedlings, which strongly suggests that young Acer rubrum seedlings do not exhibit ecotypic differences in Flood tolerance.
Abstract: -Six-wk-old Acer rubrum L. (red maple) seedlings, grown from fruits collected on paired wet and dry sites on the Coastal Plain, Piedmont, and Ridge and Valley physiographic regions of Virginia, were flooded to determine whether there are ecotypic differences in growth and physiology between seedlings from wet and dry sites. Periodic harvests were conducted over 3 mo to measure growth of flooded and unflooded seedlings derived from three trees per site. Shoot water potential and gas exchange were measured for 2 wk to determine if the physiology of seedlings from wet and dry sites were affected differently by flooding. Flooding adversely affected seedling growth and physiology resulting in shorter (18%) and lighter (30% less leaf mass, 14% less stem mass and 68% less root mass) seedlings that had higher water potentials (20%) and reduced photosynthetic rates (50%). Significant differences developed between seedlings from wet and dry sites with the wet site seedlings having lower water potentials and taller, heavier shoots. However, no significant interactions between flooding and maternal hydrologic conditions were found that would indicate genetic differences in flood response between wet and dry site seedlings. This lack of a differential growth or physiological response to waterlogging by the distinct populations strongly suggests that young Acer rubrum seedlings do not exhibit ecotypic differences in flood tolerance.
TL;DR: The recorded soil environments and community compositions provided valuable information about the natural habitats of these species and the canonical correspondence analysis identified correlations between abiotic variables, associated vegetation and the presence of these Vitis species.
Abstract: -This study investigated the environmental conditions and vegetation associated with Vitis riparia, V rupestris and V berlandieri (V cinerea var. helleri) and reports on their distribution and habitats as well as the general topography of their sites. Differences in the chemical and physical soil composition and amount of available water were detected among sites occupied by these species. Canonical correspondence analysis correlated community composition with abiotic gradients (P < 0.001). The first axis in this gradient analysis was positively correlated with increasing site moisture and negatively correlated with increasing soil carbonates. Vitis berlandieri sites were clustered at the dry end of the gradient, had a higher percentage of soil carbonates, higher soil pH and higher percentage of clay. Celtis laevigata, Juniperus ashei and Quercus stellata were associated with Vitis berlandieri. Vitis riparia sites were more mesic and were associated with Juglans nigra and Ulmus americana. Vitis rupestris sites had high percentages of soil gravel and were associated with Salix caroliniana and Platanus occidentalis. The recorded soil environments and community compositions provided valuable information about the natural habitats of these species and the canonical correspondence analysis identified correlations between abiotic variables, associated vegetation and the presence of these Vitis species.