Academia.eduAcademia.edu

Figure 4 – uploaded by Kerrie Wilcox

See full PDFdownloadDownload figure
\BLE 4. Results of regression analysis for Phragmites abundance vs. ambient air temperatures. meadow habitat in the Big Creek Marsh. In 1984, much of the area where Phragmites had occurred was dyked to facilitate a cycle of periodic draw- downs followed by reflooding. This probably elimi- nated many previously occuring stands and possibly has suppressed Phragmites growth since that time. Phragmites remained virtually unchanged in Big Creek Marsh in 1995 and 1999, possibly due to water level management and low levels of natural disturbance; of the four wetland complexes studied, Big Creek Marsh receives the most protection from the destructive wave action of Lake Erie and Inner Long Point Bay. DISCUSSION

Table 4 \BLE 4. Results of regression analysis for Phragmites abundance vs. ambient air temperatures. meadow habitat in the Big Creek Marsh. In 1984, much of the area where Phragmites had occurred was dyked to facilitate a cycle of periodic draw- downs followed by reflooding. This probably elimi- nated many previously occuring stands and possibly has suppressed Phragmites growth since that time. Phragmites remained virtually unchanged in Big Creek Marsh in 1995 and 1999, possibly due to water level management and low levels of natural disturbance; of the four wetland complexes studied, Big Creek Marsh receives the most protection from the destructive wave action of Lake Erie and Inner Long Point Bay. DISCUSSION

Related Figures (12)

FIG.1. Study area and geographic location of Long Point, Lake Erie, Ontario. veloped by Snell and Cecile Environmental Re- search (1992). The classes are: open water; submer- gents, emergents, meadow; open bog; and trees and shrubs. Emergents are further divided into three cat- egories: flat wet emergents (e.g., Nuphar, Nymphaea, Lemna, Zizania); tall, dense possibly drier emergents (Typha, grass-sedge hummocks, Phragmites); and a mixture of the former two or conditions between. Wherever possible, single- species communities were identified separately e.g., Phragmites, Typha spp.. Monospecific Phrag- mites stands were distinguished on the aerial photos by their medium gray tone and solid, fine texture as well as their height (also see Rice et al. 2000). Community boundaries and types were outlined on aerial photos using a grease pencil and then field- checked during August and September 1999. Loca- tions of the boundaries were then transferred onto clear plastic overlay sheets registered to Ontario Base Maps (OBM) at a scale of 1:10 000. Each year was overlain on the previous years’ coverage to de- tect real changes in community size and type. This step was also essential to obtain ground control points required for entry into a geographic informa- tion system. Ground control points are features such as road intersections that can be located on
FIG.1. Study area and geographic location of Long Point, Lake Erie, Ontario. veloped by Snell and Cecile Environmental Re- search (1992). The classes are: open water; submer- gents, emergents, meadow; open bog; and trees and shrubs. Emergents are further divided into three cat- egories: flat wet emergents (e.g., Nuphar, Nymphaea, Lemna, Zizania); tall, dense possibly drier emergents (Typha, grass-sedge hummocks, Phragmites); and a mixture of the former two or conditions between. Wherever possible, single- species communities were identified separately e.g., Phragmites, Typha spp.. Monospecific Phrag- mites stands were distinguished on the aerial photos by their medium gray tone and solid, fine texture as well as their height (also see Rice et al. 2000). Community boundaries and types were outlined on aerial photos using a grease pencil and then field- checked during August and September 1999. Loca- tions of the boundaries were then transferred onto clear plastic overlay sheets registered to Ontario Base Maps (OBM) at a scale of 1:10 000. Each year was overlain on the previous years’ coverage to de- tect real changes in community size and type. This step was also essential to obtain ground control points required for entry into a geographic informa- tion system. Ground control points are features such as road intersections that can be located on
+0.0—No stands were evident from aerial photography 2n/a—Intrinsic rate of increase can not be calculated, because Total area at time O (No) =0 which results in a divisor of 0.0. ABLE 1. Historical changes in Phragmites australis distribution and abundance at Long Point, Lake Erie, 1945-1999
+0.0—No stands were evident from aerial photography 2n/a—Intrinsic rate of increase can not be calculated, because Total area at time O (No) =0 which results in a divisor of 0.0. ABLE 1. Historical changes in Phragmites australis distribution and abundance at Long Point, Lake Erie, 1945-1999
FIG.3. Phragmites australis distribution in the Crown Marsh, Long Point, Lake Erie, 1945-99.
FIG.3. Phragmites australis distribution in the Crown Marsh, Long Point, Lake Erie, 1945-99.
FIG. 4. Phragmites australis distribution in the Long Point Company Marsh, Long Point, Lake Erie, 1945-99.
FIG. 4. Phragmites australis distribution in the Long Point Company Marsh, Long Point, Lake Erie, 1945-99.
FIG. 5b. Phragmites australis distribution at the Tip of Long Point, Lake Erie, East Section 1945-99.
FIG. 5b. Phragmites australis distribution at the Tip of Long Point, Lake Erie, East Section 1945-99.
TABLE 2. Types of plant species/communities replaced by Phragmites australis in four wetland com- plexes at Long Point, Lake Erie, Ontario, 1995- 1999.
TABLE 2. Types of plant species/communities replaced by Phragmites australis in four wetland com- plexes at Long Point, Lake Erie, Ontario, 1995- 1999.
TABLE 3. Results of regression analysis for Phragmites abundance vs water levels.
TABLE 3. Results of regression analysis for Phragmites abundance vs water levels.
FIG. 7. Relationship between mean annual ambient air temperature and the abundance of Phragmites australis at Long Point, Ontario, 1945-99. Ambient temperatures for Erie Pennsylvania supplied by the National Oceanic and Atmospheric Administration. Historical Distribution and Abundance of Phragmites at Long Point
FIG. 7. Relationship between mean annual ambient air temperature and the abundance of Phragmites australis at Long Point, Ontario, 1945-99. Ambient temperatures for Erie Pennsylvania supplied by the National Oceanic and Atmospheric Administration. Historical Distribution and Abundance of Phragmites at Long Point
FIG. 8. Geographic location of introduced (n = 28) and native (n = 3) stands of Phragmites australis at Long Point, Lake Erie, Ontario, 2003. Although no Phragmites stands were detected in the Crown Marsh in 1945 or 1955, large stands had developed along the northwest shore by 1964. Prior to the mid-1980s, Phragmites was concen- trated along a raised dyke and areas surrounded by
FIG. 8. Geographic location of introduced (n = 28) and native (n = 3) stands of Phragmites australis at Long Point, Lake Erie, Ontario, 2003. Although no Phragmites stands were detected in the Crown Marsh in 1945 or 1955, large stands had developed along the northwest shore by 1964. Prior to the mid-1980s, Phragmites was concen- trated along a raised dyke and areas surrounded by
Related topics:
Environmental EngineeringInformation ManagementBiodiversityLake ErieCommon ReedENVIRONMENTAL SCIENCE AND MANAGEMENT
580 California St., Suite 400
San Francisco, CA, 94104
© 2025 Academia. All rights reserved