The appearance and disappearance of major vegetational assemblages: Long-term vegetational dynamics in eastern North America

Vegetatio ◽  
1987 ◽  
Vol 69 (1-3) ◽  
pp. 177-187 ◽  
Author(s):  
Thompson Webb
Keyword(s):  
North America ◽  
Eastern North America ◽  
Vegetational Dynamics

Aggregation of Selected Three-Day Periods to Estimate Annual and Seasonal Wet Deposition Totals for Sulfate, Nitrate, and Acidity. Part I: A Synoptic and Chemical Climatology for Eastern North America

1995 ◽  
Vol 34 (2) ◽  
pp. 297-325 ◽  
Author(s):  
Jeffrey R. Brook ◽  
Perry J. Samson ◽  
Sanford Sillman
Keyword(s):  
North America ◽  
Wet Deposition ◽  
Atmospheric Transport ◽  
Precipitation Amount ◽  
Statistical Correlation ◽  
Eastern North America ◽  
Time Of Year ◽  
Transport Patterns

Abstract Running 3-day periods from 1979 to 1985 were categorised into one of 20 meteorological categories. These categories were developed through the cluster analysis of 3-day progressions of 85-kPa wind flow over eastern North America. The purpose for developing the categories was to identify recurring atmospheric transport patterns that were associated with differing amounts of wet sulfate (SO2−4) and nitrate (NO−3) deposition at a variety of locations in eastern North America. Identification of these patterns was necessary to facilitate the selection of time periods for simulation by the Regional Acid Deposition Model and in the development of a method for estimating long-term acidic deposition over eastern North America from a limited number of model runs. The effectiveness of this method (referred to as the aggregation method) was expected to be dependent on the ability of the categories to separate structure in wet deposition patterns. This paper describes the determination of the 20 meteorological categories and demonstrates that there were differences in their meteorological and chemical behavior and in their frequency of occurrence. Observations of precipitation and wet SO2−4 and NO−3 deposition from 22 sites in eastern North America and multiple regression models were used to demonstrate that there were statistically significant differences in deposition among categories and that knowledge of meteorological category explained some of the variation in wet deposition. The best statistical correlation, which was based upon precipitation amount, time of year, and meteorological category, explained 35%–83% (28%– 76%) of the observed variation in wet SO2−4 (NO−3) deposition depending on location. On average, across all sites and for both SO2−4 and NO−3, knowledge of category accounted for about 4% of the variation. The minimum amount explained by category was 1% and the maximum was 13%.

scholarly journals The Biology of Canadian Weeds. 153. Stachys palustris L.

2014 ◽  
Vol 94 (4) ◽  
pp. 709-722
Author(s):  
Stephen J. Darbyshire ◽  
Ardath Francis ◽  
Gerald A. Mulligan ◽  
Gavin L. Graham
Keyword(s):  
North America ◽  
New Brunswick ◽  
Prince Edward Island ◽  
Species Complex ◽  
Eastern North America ◽  
Agricultural Systems ◽  
Wetland Plant ◽  
Root Crops ◽  
Arable Fields

Darbyshire, S. J., Francis, A., Mulligan, G. A. and Graham, G. 2014. The Biology of Canadian Weeds. 153. Stachys palustris L. Can. J. Plant Sci. 94: 709–722. Marsh hedge-nettle, Stachys palustris, is a perennial Eurasian member of the mint family, which has become naturalized and weedy in some parts of eastern North America. It is a hexaploid member of a holarctic species complex, which differs morphologically from the primarily tetraploid North American forms. The production of fleshy tuberous rhizomes is the most significant distinctive feature. In Canada, it has been a weed of potato and root crops in Nova Scotia, New Brunswick and Prince Edward Island, although other crops and areas, such as soybean in Ontario, are also affected. Usually considered a wetland plant, it readily spreads into drier arable fields from adjacent ditches and wetlands. Several herbicides available for use in Canada have been found to provide limited long-term suppression in agricultural systems, with the best results obtained using combined pre-emergent and post-emergent applications.

Aggregation of Selected Three-Day Periods to Estimate Annual and Seasonal Wet Deposition Totals for Sulfate, Nitrate, and Acidity. Part II: Selection of Events, Deposition Totals, and Source–Receptor Relationships

1995 ◽  
Vol 34 (2) ◽  
pp. 326-339 ◽  
Author(s):  
Jeffrey R. Brook ◽  
Perry J. Samson ◽  
Sanford Sillman
Keyword(s):  
New York ◽  
North America ◽  
Model Simulation ◽  
Eastern North America ◽  
So2 Emissions ◽  
Study Program ◽  
Area Of Interest ◽  
Main Components ◽  
Selection Of

Abstract A method for deriving estimates of long-term acidic deposition over eastern North America based on a limited number of Regional Acid Deposition Model runs has been developed. The main components of this method are the identification of a representative sample of events for model simulation and the aggregation of the deposition totals associated with the events. Meteorological categories, defined according to 3-day progressions of 850-mb wind flow over eastern North America, were used to guide the selection of events. This paper describes how events were selected from the categories and how they were combined (aggregated) to estimate long-term deposition. The effectiveness of the category-based approach was compared against alternate aggregation approaches and it was found to provide the best sample-based estimates of long-term wet sulfate deposition across eastern North America. Thirty events from the 1982–85 time period were selected using a set of predetermined criteria and aggregated to estimate seasonal and annual SO2−4, NO−3, and H+ deposition at 20 Utility Acid Precipitation Study Program sites. The accuracy of the estimates varied geographically and depending upon whether they were for the annual or seasonal time periods. Over the main area of interest (a smaller 13-site region), the mean rms errors for annual deposition were 10%, 15%, and 12% for sulfate, nitrate, and acidity, respectively. Source–receptor relationships associated with the 30 events were examined for three sites located in Michigan, North Carolina, and upstate New York. It was found that the amount of time that transport was to these areas from the U.S. Midwest (an area of high SO2 emissions) was represented to within 20%.

Sign in / Sign up

Export Citation Format

Share Document