Environmental Engineering Reference
In-Depth Information
formalizes the question that is being addressed. Popper (
1959
) and Platt (
1964
)
indicated that science progresses best when hypotheses of natural systems are
evaluated empirically by comparing to predicted results to reject hypotheses that
are inconsistent with predictions. Further, Anderson (
2008
) advocated that all
plausible alternative hypotheses should be translatable into mathematical models
that are subjected to empirical methods to test the relative strength of the evidence
for each hypothesis. Chamberlain (
1890
) urged scientists to conduct studies using
the strategy of “multiple working hypotheses”. That is, study design should be
capable of simultaneously testing multiple plausible hypotheses, eliminating poor
hypotheses, and quantifying the relative strength of one hypothesis over the
alternatives (Royall
1997
). Ultimately, conclusive evidence for a hypothesis (i.e.,
science answer) can only be possible after all other hypotheses are rejected through
study design or additional studies (Williams
1997
). Development of hypotheses is a
time-consuming, challenging process that is critical to overall rigor of a study.
Sound hypotheses are based on (1) familiarity of the system being studied,
(2) detailed formulation of the question or observation being studied, and (3) work-
ing knowledge of the established literature related to the subject being studied.
In wetland science, development of hypotheses is usually study specific.
Hypotheses can range among general statements that explain an observation,
specific measureable predictions should a hypothesis be true, directionality of a
treatment effect, or support for an ecological theory. Turner (
1997
) proposed four
hypotheses to explain the observation of a high rate of coastal wetland loss in the
northern Gulf of Mexico (
0.86 %/year): (1) an extensive dredge canal and spoil
bank network; (2) decline in sediments in the Mississippi River during the 1950s;
(3) Mississippi River navigation and flood protection levees; and (4) salinity
changes. The hypotheses were developed following extensive consideration of all
potential factors influencing wetland loss and familiarity with the wetland system
being studied. A study was designed to address predictions from each hypothesis.
Turner (
1997
) concluded that, based on his study, dredging man-made channels and
forming dredge spoil banks had the greatest impact on wetland hydrology and had
the most influence in explaining wetland loss.
Testing ecological theory among ecosystems requires testable predictions for
each competing hypotheses. Megonigal et al. (
1997
) tested two competing
hypotheses under the subsidy-stress hypothesis for rate of aboveground net primary
production in southeastern floodplain forest. Under the subsidy-stress hypothesis,
they hypothesized that periodically flooded forests have higher rates of net primary
productivity than upland or continuously flooded forests. As a competing hypothe-
sis, they proposed that effects of periodic inputs of nutrients and water on net
primary productivity are diminished or offset by stresses associated with anaerobic
soils or drought. Using an experimental field study design, they measured above-
ground net primary productivity under three categories of mean growing-season
water depth. Megonigal et al. (
1997
) concluded that extensive flooding caused
significant stress on forest productivity, but there was insufficient support for the
subsidy-stress hypothesis in the description of patterns of net primary productivity
