Ancient bur oaks at Pleasant Valley Conservancy

When Kathie and I purchased (in 1980) the property that has now become Pleasant Valley Conservancy, we were not aware of its potential value as a natural area. Even when we started restoration work (in 1995) we had only a glimmer of understanding of its value. As work continued, we began to realize more and more the value of the site. A major reason was because of the appreciation we developed for the large open-grown bur oaks that were the main occupiers of the south-facing slope and the ridge top.

In 1997 a large bur oak on the ridge top came down in a storm. A neighbor cut a slice from the stump, and we found that this tree was 200 years old. Start date 1797.

In years 2010-2012 we marked every tree on the Conservancy over 10" in diameter with a permanent marker, and recorded its GPS coordinates and species. Using GIS software, I have mapped every recorded tree. Some of the data can be seen on the PVC website.

In 2013 researchers from the TREES laboratory at UW-Platteville cored 10 large bur oaks scattered across the ridge top, as part of a major dendrochronological study. The table summarizes the data. The location of each Unit  # can be found on the Management Map available on the PVC website.

Tree #	Start date	Age in 2015	Species	Diameter	Unit #
2365	1735	280	Bur oak	31.2	15
2354	1740	275	Bur oak	23.6	15
765	1747	268	Bur oak	27.9	8
2310	1756	259	Bur oak	27.1	19B
927	1776	239	Bur oak	27.7	11A
485	1777	238	Bur oak	24.8	11B
726	1788	227	Bur oak	27.3	8
914	1806	209	Bur oak	33.7	11A
1225	1830	185	Bur oak	32.3	5
2355	1845	170	Bur oak	25.1	15

Although the researchers attempted to core older trees, they only had time for a short visit. Possibly there are older trees elsewhere on the Conservancy? How many pre-Revolutionary War trees are there at PVC?

The oldest tree (#2365) is shown in the photo below. This tree is very easy to see from the main service road. In fact, a number of photographers have been attracted to this tree because of its interesting shape and large trunk. It is adjacent to the North Firebreak. As the photo shows, it is just at the top of the steep slope that leads into the North Woods. Thus, this tree is at the transition between oak savanna and oak woodland.

It is interesting to imagine what the situation was like when this tree first began in 1735. There must have been bur oaks at that time, providing acorns for the new trees. How many years has an oak forest been present at this site? At least several thousand years? This is a question that  paleoclimatological research can probably answer.