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Lake-edge Density

Lake-edge density is a measure of the density of terrestrial/aquatic edge and represents the abundance of habitat along large waterbodies (lakes and wide rivers). This dataset is used, along with other ecological criteria, to rank ecological benchmarks.

Fig 1. Lake-edge Density

LED is based on the Lakes and Islands coverage from the National Scale Framework HYDROLOGY, Version 6.0 Drainage Network (NRCAN 2009). The lakes and islands coverage contains two types of waterbodies; lakes and wide rivers as well as 38 island polygons contained within lakes and wide rivers. All these elements were maintained in the lake-edge density calculation. To calculate LED, a 1-km2 grid was generated for Canada. In ArcGIS 10, a moving window was used to calculate the length per unit area of lake and island edges that fall within a 5.6 km radius (100-km2 circle) around each grid cell. The units are km/km2.

Lake-edge density is an indicator of hydrologic connectivity and vegetation structure. The density of lakes and permanent water bodies varies markedly across the boreal and is a result of the cumulative effect of large-scale ecological processes such as glaciation, soil formation, and photosynthesis. Along the riparian zone, the gradient between waterbodies and terrestrial systems, there are significant differences between the species composition, age structure, and growth potential of forested patches, and one would thus expect directional changes in community structure of forest and non-forest flora and fauna along this gradient (Hannon et al. 2002; Macdonald et al. 2004). Also, studies have demonstrated that cross-system flows between water bodies and riparian forests can be a stabilizing mechanism in both systems (Nakano and Murakami 2001, Takimoto et al. 2002). Thus, a region of high lake-edge density would not be expected to serve as a useful ecosystem benchmark for a region of low lake-edge density. In an exploratory analysis, we found that lake-edge density was not significantly correlated with other criteria used in the delineation of system benchmarks (i.e., land cover).

References

NRCAN. 2009. Atlas of Canada 1,000,000 National Frameworks Data, Hydrology Version 6.0. Ottawa, ON.

Hannon, S. J., C. A. Paszkowski, S. Boutin, J. DeGroot, S. Ellen Macdonald, M. Wheatley, and B. R. Eaton. 2002. Abundance and species composition of amphibians, small mammals, and songbirds in riparian forest buffer strips of varying widths in the boreal mixedwood of Alberta. Canadian Journal of Forest Reseach 32:1784-1800.

Macdonald, S. E., C. J. Burgess, G. J. Scrimgeour, S. Boutin, S. Reedyk, and B. Kotak. 2004. Should riparian buffers be part of forest management based on emulation of natural disturbance. Forest Ecology and Management 187:185-196.

Nakano, S. and M. Murakami. 2001. Reciprocal subsidies: dynamic interdependence between terrestrial and aquatic food webs. Proceedsing of the National Academy of Science 98:166-170.

Takimoto G., T. Iwata, and M. Murakami. 2002. Seasonal subsidy stabilizes food web dynamics: Balance in a heterogeneous landscape. Ecological Research 17:433-439.

 

 
 
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