Environmental Engineering Reference
In-Depth Information
the basic techniques and attributes described above for emergent and terrestrial
vegetation can be applied, with modification, to aquatic vegetation. If the
submerged vegetation is very shallow, the techniques can be applied directly, but
for deeper water, access to the plants can be a problem. In order to sample deep
water vegetation, there are two solutions: go to the plants or bring the plants to you.
Going to the plants involves SCUBA or snorkeling. Sampling can be accomplished
using open-ended polyvinyl chloride (PVC) frames for plots to surround tall vegeta-
tion (Parsons
2001
). A different method of “going to the plants” involves creating a
“viewing tube” out of PVC and clear plexiglass that can be used from a boat. Unless
this is permanently-attached to the boat, it must be limited in size in order to penetrate
the water. One of the most common methods of sampling aquatic plants is using a
simple garden rake to harvest plants from a point, and then estimating percent cover
on the rake of different aquatic plant species that are brought up to the surface.
If water is very deep, the rake can be attached to a rope instead of the rake handle
(Parsons
2001
). Wide landscaping rakes used to prepare lawns are often preferred,
because they are relatively light and bring up a large quantity of plants. GPS units are
essential for locating plots when using a boat to sample.
5.3.9 Practical Considerations
There are several common practices used in field studies that are worth discussing.
Trampling the vegetation: Although this may seem a petty concern, the results
of trampling are not petty. When establishing plots and transects, it is important
to not trample the vegetation in the area that you will be sampling. Trampled
vegetation is more difficult to identify, and visual percent-cover is far more
difficult to estimate. Trampling vegetation within a permanent plot can also
affect future growth. When walking transect lines, always walk on the side of the
tape opposite the side you will be sampling. Always walk outside the plot that
you are establishing.
Voucher specimens: It is important to collect a sample specimen of each
species in your study. These are pressed in a plant press, identified, and deposited
in a local herbarium, where their identities can be verified. The purpose of a
voucher collection is to increase the quality of the study so that future
researchers can determine the plant species found in the study, even if the
names have changed, decades into the future. In situations where there are
multiple observers over multiple years, vouchers can ensure consistency in
identification. In order to not affect composition and structure of sample plots,
when at all possible, voucher specimens should be obtained outside the plot.
Site map: Site maps allow future researchers to return to your site to replicate
your study or locate important features, such as monitoring wells or access
points. Of course, GIS maps of a site with an aerial photograph for background
are the gold-standard in site maps, but even hand-drawn maps with important
