Herbaceous Vegetation Sampling
Plot Sampling: Because much herbaceous vegetation is low, the plot
shape used is generally circular, being lain out with a string from a central
stake. As many grasses are very dense, and reproduce asexually, it is hard
or impossible to count individual plants. Instead, percent coverage is used
as an estimate of the plant's importance.
- Determine the correct plot size by use of the species area curve.
- Locate two plots at random, one in the short mowed area, and one in
the bush hogged area. Obtain the percent coverage, the frequency, and the
index of similarity for the two plots. Percent coverage is estimated by
looking directly down on the plot and determining the percent of the plot's
area covered by a species. Remember that because we are working with one
layer, the percent cover must total 100% so consider bare areas within the
plot. Consider only the part of a clone located within the plot
.Compare the two plot samples by way of a pie chart. What species seem to
prefer one or the other mowing methods? What might this be due to (normal
size of the plant, reduced competition, etc.)?
Another method of sampling herbaceous vegetation is by the line intercept
method. A tape measure or rope is placed at random directly on the vegetation,
and the length of each species along the line is measured.
- Locate two transects 100 feet in length from random points, one in
the short mowed area, and one in the bush hogged area. Determine intercept
length for each plant located on the transect as a percent of the total transect
length. Look directly down on the plant and measure the area it covers
along the transect. Again, consider bare areas, so that the total will be
100 feet.
- Determine frequency and the index of similarity for the two transects.
Compare the two transects by way of a pie chart. What species seem to prefer
one or the other mowing methods? What might this be due to (normal size
of the plant, reduced competition, etc.)?
- Compare the two methods; plot sampling and line intercept sampling.
Which one seems to give a better picture of the vegetation? What are some
possible problems with the methods?
