July 19, The Exclosure Experiment Options

[Leslie_Pierce]

July 19, 2005

Our last day of sampling, and I could tell that it was a lot colder today. I hung out in my warm tent putting off the inevitable blast of cold wind. Checking my thermometer confirmed my suspicions, yep, it was 37 F - our coldest day yet. So, putting on my down coat under my shell parka and an extra pair of socks, I headed out for a day of science on the Ikpikpuk!

After warming up with coffee, we set out to sample the plots in Brian’s exclosure experiment that was set up on our island last summer. Brian’s hypothesis is that the vegetated and intermediately grubbed habitat will be turned to mud within 3-5 years and that plants won’t reestablish themselves in the grubbed mud habitat within the next decade. He set up 48 plots, or 24 pairs of plots, in three different conditions of the habitat. All of the plots were set up in dry graminoid habitat types, or higher and drier ground, because that was the habitat that was exposed when the snow geese first arrived to the delta for nesting.

There were eight replicates of three different habitat conditions:
1) Vegetated habitat (V)
2) Intermediate vegetated, moderately grazed habitat (I)
3) Muddy, heavily grazed habitat (M).
Each habitat condition included two plots, one open (the control plot or O) and one exclosed with fencing material (the experimental exclosure plot or X). So, we had eight different sets (or replicates) of three conditions to sample, with two plots for each condition. (8 x 3 x 2 = 48!) Samples were labeled according to the replicate number, the habitat condition, and the plot type; for example, the first replicate in the vegetated condition with a fenced exclosure would be labeled R1VX. Making sure all of the samples were labeled correctly would be very important. Science requires precision and accuracy in data collection, otherwise the data is useless!

We collected the same types of samples for each plot in this experiment as we did on the transects. At each plot, we noted the number of goose feces in the open plots, took a soil core sample and clipped the vegetation in the 10-cm quadrat in both open and exclosed.

Here are some pictures of examples of each plot type:

VO – Vegetated Open plot

VX – Vegetated Exclosure plot

IO – Intermediate Vegetated Open plot

IX – Intermediate Vegeatated Exclosure plot

MO – Muddy Open plot

MX – Muddy Exclosure plot


Brian was not expecting to see much difference in one year’s time, but on some of the replicates we did seem to notice a difference between the open and exclosed pairs. After the data are analyzed it will be interesting to see if there are indeed differences. This type of experiment is a long-term study, and Brian hopes to determine the rate at which the dry graminoid community is devegetated by grubbing as well as to determine if plants can re-vegetate areas that had been grubbed to mud.

The chilly temperatures of today and the wind had sapped our energy. We decided to worry about moving the kayak up to our campsite tomorrow – maybe the wind would die down at least! After a wonderful dinner of Brian’s Tom Yum Soup with kipper snacks, we called it a day. The helicopter was scheduled to pick us up around 3:00 pm tomorrow (we were finished with our sampling and were heading back a little earlier than was planned), so there will be lots to do in the morning!

Yea, we are done with all of the sampling!