Tom's Blog

Thursday, March 31, 2016

Last burn of season at Pleasant Valley Conservancy

We did savanna/prairie/wetland burns on Tuesday March 29, 2016. These were the last burns of the spring burn season. The other burns were done on March 11 and March 21

This is the earliest we have ever finished our burns. This year they were mostly done on fairly cool days when there was a high pressure air mass over the area. Temperatures never got above 60, RH generally in the 40s, wind moderate. The new burn permitting program established this year by Wisconsin DNR Forestry worked very well.

Today the wind was out of the south or east, gusting to 7-8 mph. RH got down to about 40 in mid afternoon, but there was dew on the grass in morning with a temperature of 31 F.

Burn crew: Amanda and Susan from PVC; Kathie and Tom as volunteers; Craig Annen, Chris Knief, Sean Logenbaugh, and Jared Bland from Integrated Restorations; 8 people in all. Kathie and Tom ran the pumper unit.

Savanna/Prairie/Woodland Burn (15.5 acres)

Long-narrow savanna burn: Because the wind was out of the SE, we started lighting at the west end of Unit 19. This is a long narrow savanna of about 5 acres that is situated between the ridge-top savanna and the north woods. The North Firebreak separates this unit from the big woods. To protect the North woods, lighting began on the NW corner, with one drip torch and several waters along the North Firebreak and a second drip torch doing interior lighting around special trees to be protected. [I will have a discussion of tree-centered burning in an upcoming blog post.] The north line moved first.

Starting the burn at the west end of the long narrow savanna
Note the large bur oaks. This is an area with many venerable trees

A second (south) single drip torch line starting at the same location lighted the whole length of the unit along the gravel road. See photos. Because of the south-easterly wind, this second line was mostly a headfire, although the interior lighting mentioned above created some backfire. (Remember that the extensive savannas across the gravel road were already black from the March 21 burn.)

Bringing the fire line along the savanna. The savanna to the right had been burned 3-21-2016

Because of the long burn line, and the need to protect trees, this burn moved fairly slowly and probably took most of an hour to do.

Close to the end of the narrow savanna. The smoke in the distance is from the line on the North fire break.
The pumper unit was used to put out some burning snags and downed trees, especially in an area where a patch of dead black oaks still remained. (See photos) These trees had been killed by oak wilt about 10 years ago and many of them had been "topped" by a derecho (straight-line tornado) that ran along the top of the ridge about 5 years ago. The downed timber had by now become quite rotted, which meant it caught fire easily. After the burn was completed a three-person crew returned to this site and cut up the burning wood so that it could be sprayed by water from the pumper unit. (See photos) 

[Trees in the black oak group have open woody structure, which means they are very sensitive to decomposition. The white oak group, which includes bur oak, have their pores plugged with tyloses, making them highly resistant to decomposition. Oaks in the white oak group can lay on the ground for many years without decomposing but those in the black oak group decompose rapidly.]

Using the pumper unit to put out the fire on a dead stump next to a living white oak.
Because of the large amount of wood in this savanna, there is often a lot of mop-up.
Note that this whole unit is black, indicating a satisfactory burn.

Prairie/oak-woodland burn: Once this savanna area was secured, we moved on to Toby’s Prairie and the Woodland Extension which extends into the North woods. Lighting began at the NW corner of the Woodland Extension and moved east along the edge of the woods. A second drip torch did interior lighting along the N edge of Toby’s once the Woodland Extension black line was secure. This was done in order to speed up the burn, although the Woodland Extension burn would probably have eventually reached and started Toby’s on fire. 

A second line started at the NW corner and moved up (South) along the Woodland Extension and then along the narrow West side of Toby’s. Eventually, this drip torch moved on Toby's east along the gravel road, creating a headfire along the S side. (Remember that the oak savanna south of the gravel road was already black from the burn of March 21.)

The line running along the N of Woodland Extension moved into Unit 13B and then up (south) along the edge of the Conservancy property. The second drip torch from this line did some interior lighting in north of Toby's Prairie and eventually lighted the Triangle (a savanna remnant), starting at the small ravine between the Triangle and Toby’s Annex.

Unit 13B, which is a fairly young Hill's oak and white oak woodland (around 75 years old), burned well without much interior lighting.

Stepping into the "black" to avoid the high flame height.
Burning is a small prairie remnant adjacent to the Hill's oak/white oak woodland
The prairie in the foreground had been burned 3-21-2016.
The visible kestrel box had been watered to prevent it from burning.

The whole burn finished about 1 PM. We returned to the cabin for lunch and regrouped for the wetland burn.

Wetland Burn (4 acres)

This wetland has some outstanding native vegetation but a firebreak is difficult to create because groundwater is often right at the surface. We try to burn as much as we can. Interesting species that we are trying to encourage include Turk's cap lily, turtlehead, swamp thistle, swamp milkweed, lousewort, stiff gentian, fringed gentian, and Liatris ligulostylis. There are also patches of the sedge Carex trichocarpa and cord grass (Spartina pectinata).

Mowing the wetland firebreak with the Kubota the day before the burn.
Kathie had mowed the firebreak for the wetland burn the day before (see photo). Although the terrain is difficult and often has standing water, she managed to find a path through that was OK. At no place is the area to be burned very wide, but it does widen out in a few places. Also, she managed to carry the firebreak all the way to Cty F. See the map (PDF) for the location of this wetland burn.

The burn was done in two phases, from the Barn/Crane prairie NW to Cty F and from the same point SE toward the end of the Valley Prairie. Due to the predominantly E (and SE) direction of the wind, we started the burn at the kestrel house end of the Crane Prairie and moved N toward Cty F. 

The whole line was wetlined using the pumper unit in the Kawasaki. In addition, there were four waters, two of whom were on the lookout for spots into the vast wetland to the south. It took about an hour to reach Cty F, with lots of wetlining and slow careful lighting.

We then moved the whole crew plus the pumper back to the kestrel house and burned East. See photo below for this part of the burn.

Burning the wetland. The firebreak had already been wetlined.
Most of the crew was busy making sure the fire did not creep across the firebreak.
No spot fires occurred.

What was the fuel for the wetland burn? A lot of it was probably sedge, some of which was Carex trichocarpa. Also grass and forbs. Very little, if any, cattails.

We finished the wetland burn around 4:15 PM. We then did some serious mop-up on the downed black oak log mentioned above. This mop-up needed a chain saw and the pumper  unit. (See photo)

A chain saw is essential for savanna burn mop-ups.
This punky black oak log was a three-person job.
Because it was near the edge of the burn unit, it could not be allowed to smoke.
The pumper unit provided lots of high pressure water.

We have been using this custom-designed pumper unit for about 10 years.
It is essential for mop-up during savanna burns.

The map (PDF download) gives a summary of all our spring burns, 88.5 acres. This does not include our burn of Black Earth Rettenmund Prairie, which will be the topic of another blog post.

Whether its climate change or just luck, this is the earliest we have been able to complete our spring burn program. (Some years our first burn has been March 29. One year we did not do our first  burn until April 4.) Note that we did not burn in really "warm" weather. However, all our fuel was lush and well-cured.


Post a Comment

Subscribe to Post Comments [Atom]

<< Home