A5014026730- Ecology and Vegetation Dynamics Studies
- Botany and Plant Ecology Studies
- Plant and animal studies
- Rangeland and Wildlife Management
- Botany, Ecology, and Taxonomy Studies
- Peatlands and Wetlands Ecology
- Mycorrhizal Fungi and Plant Interactions
- Plant Parasitism and Resistance
- Forest ecology and management
- Forest Ecology and Biodiversity Studies
- Fire effects on ecosystems
- Weed Control and Herbicide Applications
- Fungal Biology and Applications
- Seedling growth and survival studies
- Plant Physiology and Cultivation Studies
- Greenhouse Technology and Climate Control
- Coastal wetland ecosystem dynamics
- Plant and fungal interactions
- Ruminant Nutrition and Digestive Physiology
- Diverse Academic Research Areas
- Ecology and Conservation Studies
- Ecology and biodiversity studies
- Soil Carbon and Nitrogen Dynamics
- Wildlife Ecology and Conservation
- Biological Control of Invasive Species
University of Guelph
1992-2005
Warwick Hospital
2005
Research International (United States)
1999-2001
University of Warwick
1993-2000
University of North Carolina at Chapel Hill
1974
Summary Arbuscular mycorrhizal fungi (AMF) are important components of terrestrial communities but the basic ecology individual AMF, including their colonization strategy, remains unclear. The colonizing behaviours 21 AMF isolates from three families (Acaulosporaceae, Gigasporaceae and Glomaceae) were compared to test for a relationship between taxonomy strategy. Both rate extent considered by measuring percentage root colonization, fungal biomass, soil hyphal length biomass over 12 wk. Most...
A field experiment was conducted to test whether control of seedling emergence by ground cover and seed predation depended on size. Sown seeds 12 oldfield species with masses ranging from 0.06 12.2 mg were used for the test. Species response experimental removal (or) addition a cage reduce recorded. Results determine relationship between mass effects emergence. Adding did not increase significantly each four smallest (<0.14 mg). In contrast, increased eight larger (...)
Two functional attributes of an ecosystem, net primary production and subsequent dry matter accumulation, were examined in four peatland types (lagg, bog, muskeg bog forest) located southeastern Manitoba. A preliminary peat accumulation budget was constructed by relating the amount litter present after a single year decomposition to initial income annual production. Annual “income” vegetation zones ranged from 489 gm/m 2 , which represented 69% 90% calculated Decomposition losses following...
We investigated the mechanism by which grass litter (dead Poa pratensis L. shoots) suppressed emergence of seedlings four old-field forbs (Centaurea nigra L., Dipsacus sylvestris Huds., Hypericum perfioratum Verbascum thapsus L.) determining effect on their seed germination and shoot extension. When seeds were placed beneath (715 g m -2 ) that had been collected from an old-field, all species except was reduced significantly 26% to 41% compared a no-litter control. in plastic dishes...
Arbuscular mycorrhizal fungi (AMF) are integral components of terrestrial ecosystems. Currently, it is difficult to predict the dynamics AMF communities, mainly because little known about life-history strategies. This review provides a theoretical context for community on successional time scale, based differences in While some studies have examined colonization and persistence behaviors among AMF, these traits not been strategies AMF. We propose model whereby colonizing responsible...
A standardized neighbor removal experiment was conducted in 12 plant communities located on three continents to test the null hypothesis that competition intensity (CI) independent of amount biomass present. Six plots were chosen each community cover range local variation biomass. In plot relative growth rate (RGR) transplanted Poa pratensis (Poaceae) seedlings compared presence and absence neighbors. Neighbors removed experimentally using herbicide. Removing neighbors increased RGR...
We tested whether effects of competition and herbivory on plant growth depend the aboveground biomass vegetation. Our objective was to test theoretical predictions about site—dependence biotic mechanisms population regulation. Biomass ranged from a mean 64 776 g/m 2 at eight study sites, which included six old fields two herbaceous communities near water. To measure competition, 4—5 wk plants perennial grass (Poa compressa) were transplanted into plots where neighboring either left intact or...
The germination characteristics of Stellaria media (common chickweed) were investigated over a range constant temperatures and degrees moisture stress in order to assess the suitability hydrothermal time as basis for modelling under field conditions. Maximum percentage occurred much narrower temperature around optimum than previously seen cultivated crop seed. entire final response water was well described by two probit curves, this model extended describe data at all potentials close...
A study was conducted at two peatland sites in southern Ontario to test the hypothesis that flowering-time diversification among ericaceous plants has resulted from interspecific competition for pollinators. Exclusion of pollinators indicated insect visitation important seed set all species tested. The composition insects visiting five overlapped considerably, which suggested could be responsible observed differences peak flowering times. While previous experimentation demonstrated is...
Maximum depth of vertical root penetration into the soil (i.e. rooting depth) and shoot growth were measured for seedlings 42 species vascular plants in both unwatered watered columns. The ratio to was calculated quantify plasticity depth. objectives determine whether all show equal measure extent which seedling influences ability sustain drying soil. Seedlings allowed initiate continuously moist sand during a 21-day pretreatment. Two watering treatments (unwatered vs. daily) then applied an...
(1) To judge if plant survival, recruitment and population growth were affected by competition equally at opposite ends of a complex environmental gradient (i.e. low nutrient, high light, standing crop to higher lower crop), the response Hieraciumfloribundum removal interspecific some intraspecific neighbours was recorded in an abandoned pasture. determine soil moisture availability intensity competition, precipitation excluded for first part experiment plants watered either frequently or...
Individual leaves of three bog ericads, leatherleaf (Chamaedaphne calyculata), laurel (Kalmia polifolia), and Labrador tea (Ledum groenlandicum), were retained for a maximum two growing seasons in peat southern Ontario. The premature loss mature leaves, resulting from artificial defoliation, significantly reduced the growth new shoots L. groenlandicum K. polifolia but not C. calyculata. Defoliation effects directly proportional to normal retention time overwintering leaves. Mature probably...
Arbuscular mycorrhizal fungi (AMF) are integral components of terrestrial ecosystems. Currently, it is difficult to predict the dynamics AMF communities, mainly because little known about life-history strategies. This review provides a theoretical context for community on successional time scale, based differences in While some studies have examined colonization and persistence behaviors among AMF, these traits not been strategies AMF. We propose model whereby colonizing responsible...
The presence of ground cover (i.e., plant biomass and litter) could restrict seedling emergence by providing a habitat for seed predators. To test this hypothesis, field experiment was conducted with three old-field forbs (Daucus carota, Centaurea nigra, Taraxacum officinale). Ground either removed or left in place sown seeds the were protected from predators unprotected. Where predators, did not improve when removed. significantly all species Apparently, more unprotected where present than...
The seed set of eight bog plants in the Ericaceae family was reduced by excluding insect flower visitors even though hand-pollination tests showed that all species were self-compatible. Floral morphology evidently minimizes possibility pollen will be transferred from anther to stigma absence visitation. Bees most important visitors, collecting nectar and (or) pollen. attractiveness (nectar extractable per minute) ericad flowers varied considerably. This variability would promote forager...
-Forest canopy was partly removed [33% or 66% removal of tree basal area (BA)] from patches three sizes (0.015, 0.053, 0.196 ha) to determine whether the frequency five deciduous forest herbs affected by patch size. Herb frequency, irradiance and woody stem density were recorded after 2 yr later. Irradiance both increased more in large (0.196 than smaller (0.015 0.053 with 33% BA removed. In contrast, where removed, four fifth herb unaffected Where also for one about same amount all another...
(1) The perennial herb Hieracium floribundum was found less often at the bottoms of small depressions (1-4 m diameter and 0-5-1 deep) than tops in an abandoned pasture Ontario, Canada. This study to determine whether this variation due differential seed dispersal, seedling establishment, plant survival or reproduction. (2) More wind-dispersed seeds landed top (9300 m-2) bottom (4100 m-2). (3) Topographic position had little effect on establishment within a particular habitat type (i.e....
Effects of herbivory and competition on plant mortality reproduction were compared a hollow to ridge topographic gradient in an abandoned pasture. Plots with herbivores excluded (or) vegetation removed set up along control plots hollows ridges. Plants three perennial forbs (Medicago lupulina L., Centaurea nigra Taraxacum officinale Weber.) that occurred naturally less often than ridges transplanted into plots. Transplant recorded over sixteen month period