Group: biodiversity_conservation - with tag ontario [16 articles]

Abstract

During 20 years of climatic warming, drought and increased forest fires between 1970 and 1990, DOC concentrations declined by 15-25% in lakes of the Experimental Lakes Area, northwestern Ontario, allowing increased penetration of both UV and photosynthetically-active radiation (PAR), and causing deeper euphotic zones and thermoclines. Decreased input to the lakes of DOC from terrestrial catchments and upstream lakes was the primary reason for the decline, although in-lake removal also increased slightly. Decreased streamflow caused by drought was more important than ...

Abstract

The biomass growth and nutrient cycling model 'ForSVA' (forest-soil- vegetation-atmosphere model) is used to analyze potential changes in nutrient cycling (Ca, Mg, K, N, S) and forest biomass production in response to four climate-change scenarios. The analysis is done for an old growth hardwood stand within the Turkey Lakes watershed north of Lake Superior, Ontario. With ForSVA, any effects due to species interactions, competition, and resulting species shifts are not addressed explicitly. Instead, the calculations are based on functional relationships that ...

Abstract

The development of forests in Pukaskwa National Park, Ontario, Canada, was simulated over 150 years to investigate boreal carbon dynamics and to test the feasibility of simulating large tracts of heterogeneous boreal forest. Pukaskwa National Park, located on the north shore of Lake Superior, encompasses 1835 km(2) of the Superior Section of the boreal forest. We developed a patch model, called BOPAS (BOreal PAtch Simulator), to simulate the development of carbon pools as a function of environmental parameters, Using GIS techniques, ...

Abstract

The region studied includes the Laurentian Great Lakes and a diversity of smaller glacial lakes, streams and wetlands south of permanent permafrost and towards the southern extent of Wisconsin glaciation. We emphasize lakes and quantitative implications. The region is warmer and wetter than it has been over most of the last 12000 years. Since 1911 observed air temperatures have increased by about 0.11 degrees C per decade in spring and 0.06 degrees C in winter; annual precipitation has increased by about ...

Abstract

Acute ecological changes in North American boreal forests in this century are attributed to an array of factors including human activities. In the Quetico-Superior Ecotone of Northwest Ontario and Northern Minnesota warmer, drier climate conditions since mid-century have concurred with extensive manipulation of regional forests by fire suppression and clear-cut logging. Predicted effects of climate changes expected for the next century could compete with transformations in these systems over the past similar to 10 000 yr. The degree of alteration of ...

Abstract

Dissolved organic carbon (DOC) concentrations and DOC export arestudied during storms to examine the relationship between DOC concentration and stream discharge and to assess the importance of storms on DOC export. Storms were monitored in seven subcatchments within two small watersheds (Harp 4-21 and Harp 3A) on the Precambrian Shield in Central Ontario, Canada. Stream DOC concentrations increase during storms by as much as 100% and 410% in Harp 3A and Harp 4-21 respectively. The seasonal regression between DOC and stream ...

Abstract

Predicting the effects of climate change and atmospheric deposition on water quality requires predicting the effects of landscape form on export of substances downstream. In this paper, we present dissolved organic carbon (DOG), total phosphorus (TP), and iron (Fe) export data (1980-1992) for 20 relatively undisturbed, forested catchments draining into seven lakes in central Ontario and develop regression models of chemical export as functions of landscape composition. The extent of wetlands was correlated with export of DOC and TP; the proportion ...

Abstract

A brief cold-warm-cold climate change during the middle Wisconsinan is described for the first time in North America, based on fossil beetle assemblages at Titusville, Pennsylvania. AMS dating of insect chitin and wood suggests the change occurred between 39,000 and 43,500 yr B.P. Basal peats in river terrace deposits contain arctic- subarctic beetle species representing a climate similar to that found at treeline in Canada, where mean July temperatures range from 10 degrees to 13 degrees C. These cold-adapted beetles were ...

Abstract

Temperature data from ten weather stations across Canada were used to model the effects of climate warming on the timing of bud burst and the risk of frost damage to white spruce (Picea glauca (Moench) Voss). There was evidence of increasingly earlier dates of bud break over the course of this century at half of the stations examined (Amos and Brome, Quebec; Cochrane, Ontario; Fort Vermilion, Alberta; and Woodstock, New Brunswick), with the period 1981 to 1988 having the earliest predicted ...

Abstract

Recent predictions that tropospheric aerosols have counterbalanced greenhouse warming assume aerosol emissions were low before AD1850 and then increased dramatically with industrialization of the Northern Hemisphere and biomass burning in the Tropics. We assembled the lake sediment record of emissions across northeastern North America, where temperatures are predicted to have been substantially affected by industrial aerosols. Sediment evidence suggests a systematic shift in source and an overall decline in emissions since the 19th century. The geographical shift results from high presettlement ...

Abstract

Ecologists have long debated whether Indian burning had important impacts on presettlement forests. We obtained stratigraphic evidence for fire using charcoal analysis of southern Ontario lake sediments. The record spans a period of Iroquois occupation when cultivation coincides with pollen evidence for transition from northern hardwoods to white pine/oak forests. Charcoal data reveal that this transition was attended by increased charcoal accumulation, sufficiently high to suggest vegetation fires. Results support the notion that Indian burning is capable of producing dramatic changes ...

Abstract

Clark and Royall (1994) questioned the interpretation, drawn from a simulation model, that climatic cooling was responsible for the demise of typical northern hardwoods taxa and replacement with taxa that require fire or soil disturbance, Pinus and Quercus. Those questions were raised because the model predictions did not well describe the data, the ecology of the taxa is not consistent with the interpretation, the other sites in the region do not show the patterns consistent with climate cooling, and stratigraphic charcoal ...

Abstract

GLOBAL climatic change may alter species' ranges as well as restructuring ecosystems1-3. Models simulating forest growth predict that the area covered by different forest types may be affected2, which may in turn further affect climate3. In the mixed forests of southern Ontario, pollen analyses have demonstrated that after AD 1400, Fagus (beech), the formerly dominant warmth-loving species, was replaced first by oak (Quercus) and subsequently by pine (Pinus strobus). Although these changes had been attributed to aboriginal forest clearance4-6, they have ...

Abstract

A kettle-hole peatland in southern Ontario was examined in a two core, multi-component paleoecological study to determine the relative importance of external and internal factors in its long-term development. Dated sediment stratigraphies, loss-on-ignition, macrofossils and diatom assemblages from two cores were used to infer hydroseral changes within the basin, while pollen assemblages from one core were used to infer surrounding forest succession. A circumneutral to slightly alkaline lake occupied the basin at 11 750 years BP after the melting of an ...

Abstract

We present a simple empirical model that allows an estimation of mortality due to spruce budworm (Choristoneura fumiferana) outbreak in relation to fire frequency and site characteristics. The occurrence of a recent spruce budworm outbreak around Lake Duparquet (48 degrees 30' N, 79 degrees 20' W, ca. 300 m a.s.l.) in northwestern Quebec permit ted a reconstruction of the stand composition before the outbreak, and also of the mortality of Abies balsamea due to the outbreak. The basal area of A. ...

Abstract

In a boreal forest catchment in the Experimental Lakes Area in northwestern Ontario, wildfire caused an increase in the concentrations of strong acid anions and base cations of the stream. In the naturally base-poor Northwest (NW) Subbasin, a 1980 wildfire caused exports of strong acid anions to increase more than export of base cations, causing a 2.5 fold increase in the acidity of the stream. Mean annual stream pH declined from 5.15 prior to fire to 4.76 two years after fire. ...