Environmental Engineering Reference
In-Depth Information
Fig. 5.2 Spatial heterogeneity created by multiple scales of environmental gradients in wetlands.
(a) Large-scale zonation corresponding to large-scale elevation gradients. (b) Small-scale
microtopographic heterogeneity corresponding to features like hummocks, pools, and coarse
woody debris (Published with kind permission of
©
M. Kuchta 2014. All Rights Reserved)
photography can be obtained from multiple sources, including the National
Wetlands Inventory (aerial imagery viewer), United States Department of Agricul-
ture (USDA) Natural Resources Conservation Service (NRCS) Gateway (
http://
datagateway.nrcs.usda.gov
), and the United States Geological Survey (USGS)
EarthExplorer (
http://earthexplorer.usgs.gov
). Important information to gather
from photos includes: wetland size and dimensions, type of strata (aquatic, under-
story, shrub, and/or tree), access points, and any obstacles to travel within the
wetland (e.g. ponds, rivers). After locating and investigating the photography, a
preliminary site visit can help identify microtopographic patterns to take into
consideration, further obstacles to travel within the wetland, and unknown plant
species to identify prior to intensive sampling.
Questions to ask yourself before choosing where to sample within the wetland:
1. Is it important to quantitatively describe the complete vegetation of the wetland
or is a description of the vegetation in each community type sufficient?
2. Are communities easily recognizable and discrete, or do they grade into each
other so that it is difficult to detect changes without quantitative data?
3. Is pseudoreplication an important consideration? That is, is it important to
collect samples only from within one zone or microsite, or across many?
