Environmental Engineering Reference
In-Depth Information
functions are ultimately influenced by wetland hydrology; therefore, it is critical for
investigators to fully describe the relative source and fates of water for the study
wetland type. It is not necessary to provide a detailed water budget but a general
depiction of water dynamics assists in understanding the context of wetland studies.
In a similar fashion, one must describe as completely as possible the watershed or
drainage area associated with study wetlands in terms of size, soil types, land use,
anthropogenic features, and any proposed future changes in these characteristics
should it be pertinent to the study.
Once a study question and associated hypotheses have been developed, an
investigator must define several characteristics of the study. The temporal period
for sampling must be appropriate for the question. For example, one would not
attempt to test habitat selection for breeding birds during a nonbreeding season.
Therefore, it is crucial to understand the life cycle of any species of interest and
responses of each species to changing wetland conditions to avoid sampling during
unsuitable periods or environmental conditions. Investigators must carefully list
potential dependent and independent variables that will provide the most parsimo-
nious information relative to the proposed hypotheses and study objectives. Typi-
cally, but not always, dependent variables are defined by the hypotheses and
objectives; however, potential independent variables are not as obvious and require
a great deal of thought prior to finalizing a study design. Concurrently, confounding
and covariate variables must be identified and addressed to avoid any unwanted
influence by nuisance variables on the study results.
Finally, in any study design, the project budget must be known with all of the
associated restrictions and time sensitive requirements. No study is possible without
funding and continuous accounting of project expenses is necessary to avoid
situations that would jeopardize the study. It is usually a benefit to keep all
investigators and observers informed regarding the budget status to assist in future
planning for efforts related to the study. It may be prudent early in the study to
develop a number of contingency study plans in the event of unexpected conditions
such as loss of funding, natural disasters, destruction of equipment, or greater than
anticipated costs. This would allow for the salvage of some information should the
study go awry rather than being a complete loss.
1.13 Summary and Additional Considerations
on the Application of Study Design
Designing a research project requires a thorough understanding of the wetland
system being studied, the question or issue of interest, and those variables that
must be measured to address the biological question of interest and test competing
hypotheses. Following establishment of the study question (i.e., objective[s]) and
associated hypotheses, investigators should then develop the methodology of the
study. It is the methods of a study design that attempts to remove any investigator
