Guidance for our Forest
Should I Thin The Trees?
High Sierra Ranger District
Huntington Lake Recreation Residence
Fire hazard reduction thinning guidelines
These guidelines will give cabin owners the basic tools for deciding which trees need thinning and which trees should remain. Cabin owners should only thin within 30 feet of their cabin. Thinning provides space. Greater space between the boles and crowns of trees will allow space for growth, increase tree vigor and reduce the potential for the spread of crown fire.
These thinning guidelines are based on meeting the objectives of improving the health of the forest, reducing the fire hazard around cabins and maintaining the beauty of the Huntington lake area.
The guide below is designed to give a cabin owner (or individual hired by a cabin owner) the tools necessary to answer the question "Should I thin this tree?" The guidelines provide answers to basic questions: Are there excess trees around my cabin? Which trees should I remove? Are the trees around my cabin a fire hazard? How do I choose between trees?
Cabin owners will be thinning trees less than 10 inches in diameter at 4.5 feet from the ground (also called diameter at breast height) or 14 inches at the stump. Do not remove trees larger than these two measurements.
Determine first if trees are in need of thinning. Look at the space between the boles of all trees big and small. If the distance between boles is less than 12 feet apart for areas dominated by fir (more than 50% fir) then thinning is likely necessary. If the distance between boles is less than 16 feet apart for areas dominated by pine then thinning is likely necessary. Look at the tree crowns. If the crowns of neighboring trees are touching, then this is also an indicator that crowns should be thinned. If the crowns of small trees are touching the lower crowns of bigger trees this is an indication that trees should be thinned.
Tree removal occurs to provide growing space for the remaining trees. Trees that remain are selected on their ability to make use of increased site resources, and reduce the fire hazard. The criteria below are in order of priority. It is more important to leave a healthy sugar pine at the wrong spacing then it is to leave a fir at the right spacing. It is more important to leave a tree that has good crown characteristics than one that might provide regeneration. Thus these criteria should be used in a step-wise process. Criteria used in determining trees to remove and trees to leave are listed below:
Healthy Sugar pine is the first priority. Leaving healthy young sugar pine will provide the needed genetic material to keep this tree species hi the woods. Sugar pine across the Sierras are being killed by the white pine blister rust, keeping healthy sugar pine will insure species survival. Jeffrey Pine is given third priority. Pine species in general are being crowded out by the fir. Pine trees love light. Fir loves shade. So if you are choosing between a healthy fir and a healthy pine, please choose the Jeffrey pine. Give the pine lots of space and light. Lodgepole pine is given last priority. This species loves the cold and the sun. When it finds these conditions it will grow in dense thickets. Fir trees are often found growing underneath the lodgepole pine. Remember fir loves shade. Choose the fir tree over the lodgepole pine.
Leave healthy trees. Leaving deceased trees treepromotes sickness. If you have a choice between a sick tree at the right spacing and a healthy tree at the wrong spacing, then leave the healthy tree. Prune mistletoe off of trees when possible. Pruning of mistletoe should only be done in the lower third of the crown. The illustration at the right shows proper pruning. If mistletoe is found in the upper two thirds of the crown the tree should be removed. Remove trees that have mechanical damage. Mechanical damage could be caused from snow, vehicles or past logging. Healthy vigorous trees have the best chance of taking advantage of more space.
Crown Position and Crowns
Big crowns are better than small crowns. Crowns higher than the neighboring tree are better than crowns stuck down below the canopy of similar size and aged trees. Crowns are a good indicator of a trees over all health. The crown position or where a trees crown is relative to other trees of similar age is also an indicator of tree vigor. Typically trees with less than 35 percent of the bole occupied by green foliage are not likely to respond to thinning. Thinning can actually result in the death of these poor crown trees. Trees in the lower crown layers are removed to provide space for trees in the upper crown layers. Crown position is a strong indicator of a trees ability to make use of site resources.
Leave trees of all sizes. This will insure that enough young saplings and seedlings are left to replace the older trees that will die. Remember that fir loves shade and pine loves the sun. This fact of life has a great impact on how new young trees come into the forest. Since fir loves the shade, fir saplings can survive in the shade for decades. Since fir can get started under the shade of older trees, this results in fir stands with many ages represented. When a big old fir dies the younger fir in the understory will get sun and begin to grow. In areas dominated by fir try to leave a mix of size or age classes. Pine loves the sun. Unless a pine gets lots of sun all its life it will wither and eventually die. This has been happening a lot around Huntington Lake. If you have young pine encourage their growth by leaving the trees that have their crowns well above the others. A pine with its crown buried amongst its neighbors won't do well.
Trees that provide fuel ladders to larger trees or to structures should be removed to create conditions that reduce the ability of wildfire to jump from crown to crown. Protecting larger trees from fire maintains these trees in the forest. Removing trees that touch buildings or structures provides defensible space. Defensible space is what a fire fighter needs to save your cabin from fire.
Trees are spaced apart to provide room for crowns and root expansion, meet objectives to reduce tree stress, and reduce the potential fire crowning. Space trees at a minimum one-crown width from its neighbors. Space trees at least 10 feet from structures (more defensible space). In areas dominated by fir space tree boles 16 feet apart. In areas dominated by pine space tree boles 18 feet apart. Thin within 30 feet of your cabin.
Once you have made the choice to thin trees from your cabin, you will need to dispose of the thinned material and any other ground fuels. Large material can be burned in your fireplace or campfire ring. Small limbs or brush should be piled or chipped. Piles should be burned in the fall. Please follow all the normal burning requirements for air quality and fire safety. Chips can be spread out across your permit lot. Do not make piles of chips.
Prepared by Ramiro Rojas, District Silviculturist