Wednesday, February 22, 2012

Thinning a Kanza block

In a previous post, I talked about making the decision to thin trees in a block of Kanza pecan trees. To help make the decision on which trees to remove, I spent some time plotting out a tree size map using the diameter of every trunk in our Kanza block. Since crown size is proportional to trunk diameter for open grown trees, I can create a visual representation of the orchard using plotting features in Microsoft Excel (plot at right).
Looking over the map, you can see that the orchard has begun to crowd in the northeast corner (upper right). See how the tree circles on the graph are touching each other in that portion of the field.  This is exactly what we see in the field--limbs starting to touch only in a small section of the orchard. You will also note that we have a few small trees scattered through the orchard that seem to be lagging behind the others.

Using this visual information, I decided on the best pattern for thinning the entire orchard. For the first thinning, we will remove trees on the diagonal. The map at left shows the diagonal tree rows that will be removed (red lines). With this thinning plan I will remove all but one of the runty trees.
The entire orchard does not need to be thinned at this time. We will remove trees only in areas where the trees are beginning to crowd. For this first year of thinning, we plan to remove just 7 trees. These trees are marked on the map by black dots.
Thinning this orchard will take several years, but we’ve got a plan in place. As trees in other portions of the orchard start to crowd more trees will be removed until eventually the entire orchard has been thinned.
We cut down the 7 trees marked in our thinning plan today (photo at right). Once the trees are on the ground, we pull the entire tree top out of the orchard using a tractor and log chain. These trees will eventually be cut up for firewood.

Cutting down trees gave me the opportunity to see the growth rate of trees in this block of Kanza trees. In the photo at left, you can see  annual growth rings of 1/4 to 3/8 of an inch per year every year. This tree was growing fast! It no wonder we needed to start the thinning process in this portion of the orchard.