Blog #4
Haphazard sampling was best for identifying rare species, and I suspect an ecologist with a keen eye would enjoy even more success than I did. Depending on how it’s done it can also be the fastest. I imagined myself trying to get something from each area at Snyder Millsworth as I walked north. Systemic sampling was fastest for me at the Mohn Mill site since that didn’t have clear areas to choose from so I chose at random. I also stumbled onto more rare species at both sites, though they appeared to more common than they actually were. Haphazard sampling also produced the greatest percentage error for common species.
Random sampling produced very low percentage errors for common species though also ran into the problem of missing rare species and overestimating the rare ones I found. Beyond showing a species is present in some amount, a single lucky quadrat can be misleading. At Mohn Mill a single quadrat was selected that contained the rare striped maple. This created a frequency percentage error of 1566%!
Systemic sampling was quickest if I wasn’t doing “lazy” haphazard sampling. I chose transect using dice and took quadrats on alternate side of the line. At Snyder Millsworth my transect was light on Eastern Hemlock, the most common species, producing a 16.8% error. The cluster of white pine was completely avoided at Mohn Mill since my transect was near the top of the map and didn’t sample the relatively flat terrain the pines are present on.
All three approaches had strengths and weaknesses. Which one is best would depend on the purpose of the sampling, the area being studied and the skill of the ecologist. If I only wanted to identify as many species as possible I’d go with haphazard and keep an eye out for things I haven’t found yet. If I wanted to get a big picture of common things I’d do random sampling. If I had limited resources and wanted lots of samples, or wanted to compare abundance on varying altitudes or slopes I’d do a transect that would take that into account.
Whether 24 quadrats are enough would depend on what one was investigating. It could show that one species such as eastern hemlock is more common than a rarer one, but wouldn’t be nearly enough to weigh on the relative abundance of rare species.