FRC-19 University of Florida School of Forest Resources and Conservation Extension
Managing Your Forest Landscape for Firewood
D. Mitchell Flinchum (District Director and Professor Ph.D.)
The homeowner who is presently heating with wood or who plans to convert at least partially to a wood-burning home heating system may find a portion of the annual wood supply in his own yard. In many areas of Florida even small house lots usually have shade trees. Depending on size, location and age, many shade trees will provide fuel in the form of broken limbs, prunings, or in some cases the entire tree.. In most instances trees are cut because of physical damage, insects, disease, or defect. What ever the reasons, the owner may plan or these removals at a time to coincide with fuel wood needs.
Some homeowners build on preselected lots and have control over house style and location. In this case they may decide which and how many trees will be removed. Most homeowners, however buy from a developer or previous owner and have little or no say in landscaping the lot and little opportunity to manage for a secondary product such as firewood. Since the lot owner will live on the acreage for three or four years, changes will usually take place. Often some additions are made to the house and lot. Fences are built; porches, decks or additional rooms and patios are added; a garden is planned; occasionally a swimming pool is constructed; a tree is located too near the house -these changes will affect the landscape and often require removal of trees.
Additional Benefits
Florida's climate is conducive to growing wood much laster than most other areas in the nation. Because of the fast growth rates of some species, it is possible for an owner of a small partial of land to plant trees or to take advantage of existing vegetation that can be used for firewood production.
To manage land for any objective, certain trade-offs and compromises must be made. Growing trees requires space; therefore, it is essential to convert most of the sodded and manicured lawn area of the lot to "tree space" or natural areas. This conversion alone will accomplish several indirect benefits that contribute to energy conservation. In reducing the lawn area there is a proportional reduction in time and energy spent mowing, in mower maintenance and operating costs, and in water and fertilizer requirements. If planned properly, these natural ''firewood production" areas can create needed shade to reduce the heat load on the house. They also make excellent privacy screens and noise barriers.
Creating natural areas for firewood production is energy efficient and practical, and it does not detract from the beauty and diversity of the landscape. A well planned firewood producing landscape, once established, will require limited maintenance and, depending on the size and composition, produce a portion of your annual firewood needs.
Managing Existing Areas
Similar to the forester who manages large tracts of land, the owner of a small woodlot must establish a management plan. Goals and objectives must be set. If production of firewood is one of the objectives, the manager must decide which trees and how many will be dedicated to this purpose. The objective may be to furnish annually all fuelwood needs. If so, a sufficient number of trees must be available for 2 or 3 cords of stacked wood to be harvested annually without depleting the supply.
Before cutting any firewood, inventory all the trees that are in the boundary of the landscape that is set aside for fuel wood production. The inventory should include the numberand species of trees and two measurements - the total height in feet and the diameter in inches at breast height (dbh). The dbh is generally taken at 4.5 feet above the ground. Both measurements can be taken with a scale stick, available from most forestry supply companies, but there are other ways.
Simple calipers for measuring the diameters of trees can be made from a framing
square and small wooden strips
(Figure 1).
Heights can be estimated by leaning a pole or strip of known length next
to the tree and judging how many pole lengths are in the tree. If height
and diameter is known, it is possible to estimate the number of cords of
firewood that can be cut from each tree by using Table 1. If the measured
tree is 12 inches in diameter and 60 feet tall, locate 12 in the far left
column of the table. Read to the right, along the line, until you find the
column headed with 60. The number located at the intersection of line 12
and column 60 is an estimate of the standard cords of firewood (in this case
.33) which can be cut from that tree. Do this exercise for each tree in the
woodlot to find the total number of standard cords of firewood that is currently
available. Remember, a standard cord is almost twice the amount of wood that
you would purchase as a face cord.
| Table 1. Cords of firewood that can be cut from standing trees. | |||||||||
| Diameter Breast high (inches) |
Total Height (feet) 20 30 40 50 60 70 80 90 100
|
||||||||
| 4 | .02 | .03 | .04 | .05 | .06 | ||||
| 6 | .03 | .05 | .07 | .09 | .11 | ||||
| 8 | .05 | .08 | .11 | .14 | .19 | ||||
| 10 | .12 | .16 | .20 | .24 | .28 | .32 | |||
| 12 | .22 | .27 | .33 | .43 | |||||
| 14 | .28 | .35 | .50 | .57 | .64 | ||||
| 16 | .45 | .54 | .72 | .81 | |||||
| 18 | .55 | .67 | .77 | .88 | 1.0 | 1.1 | |||
| 20 | .67 | .81 | .94 | 1.1 | 1.2 | 1.3 | |||
| 22 | .80 | .96 | 1.1 | 1.3 | 1.4 | 1.6 | |||
| 24 | 1.1 | 1.3 | 1.5 | 1.7 | 1.9 | ||||
| 26 | 1.3 | 1.5 | 1.7 | 1.9 | 2.1 | ||||
| 28 | 1.5 | 1.7 | 2.0 | 2.2 | 2.5 | ||||
| 30 | 1.7 | 2.0 | 2.3 | 2.6 | 2.8 | ||||
| 32 | 2.2 | 2.6 | 2.9 | 3.2 | |||||
| 34 | 2.5 | 2.9 | 3.2 | 3.6 | |||||
| 36 | 2.8 | 3.2 | 3.6 | 4.0 | |||||
Keep records of the initial inventory of trees and wood volume. Record and deduct the trees and volume which you remove and watch for those trees that were previously not countedbut grew large enough to be measured and added to the total volume. As a rule of thumb, an acre of good hardwood land should be capable of producing about 2 cords of wood each year. Hardwood sites with this capacity can produce almost all of your fuel needs on a single acre. On poorer sites, such as the sandhill scrub oak type, several acres may be required to yield the same continuous supply.
The First Firewood Harvest
On a well forested site, the first firewood harvesting effort should be a thinning. Suppressed trees, or those which are tall, slender, and have compressed crowns that were caused by over-crowding, should be removed. Leave for the time being those dominant trees which have expressed a competitive advantage by producing a full widespreading crown. From the skematic stand profile in Figure 2, trees numbered 2, 4, 8, 10, and 15, would be removed in this operation. This method of cutting, often called a "low thinning" or "thinning from below" facilitates the removal of those trees that have not grown as fast as others in the stand. It also reduces unnecessary competition for the fast growers. Additionally, if carefully implemented, this type of operation will result in very little disturbance to the woodlot and will not make it any less attractive (Figure 3). Unless there is a specific reason to keep them, all pine trees in the firewood production areas should be removed during the first harvest While small amounts of pine may be burned in a wood burner or fireplace, avoid it when possible. The high resin content of pines will cause creosote and tar build-up that increases the chances of chimney fires
.Any improvements to the stand, such as taking out the diseased, damaged and defective trees may be conducted at this time. Trees already dead, or decaying snags, such as number 12 in Figure 2, may be left as nesting cavities for birds and animals. These relics are by no means competing with the other trees and the decaying wood is less than satisfactory for fuel. However, they may cause accidents by falling, so watch them closely.
If possible, conduct thinning and cutting operations in the late winter-early spring of the year in which the wood will be used. This schedule gives adequate time for the wood to dry to the desired moisture content for more efficient burning. It is also important in regenerating the stand, a topic discussed in more detail in another section of the paper.
Second Year Harvest
Since most of the suppressed, dead and dying trees were removed during the first year's low thinning and improvement operations, the second year harvest must come from the larger healthier trees in the stand. By comparing Figure 2, "Skematic profile of hardwood stand," and Figure 3, "Stand profile after low thinning and improvement cut," it is obvious that the character of the stand was changed only slightly. The second year's harvest, however, will drastically modify the stand because trees that make up the main canopy will be removed.
Choosing the trees to cut during the second year may be based on a number of factors, but the most important relates to the growth rate of the individual trees. Using the inventory information from the previous year, several trees that were measured should be identified. New measurements should be taken on those trees to find out how much new wood has accrued over the past year. For example, if the estimated standing volume after the first cut (the low thinning and cut) was 10 cords and the estimated standing volume before the second year's harvest is 1 1 cords, harvest only 1 cord during the second year. Make the second year firewood cut from those trees that did not show any growth over the past year. If all the trees that were measured showed some new growth, cut from those that grew the least.Tree number 6 in the stand profile figures would probably be the best candidate for harvesting the second year. Due to its size and apparent age, the growth rate was probably less than any other tree in the profile. This one tree may also contain enough wood for the allowable cut the second year. Figure 4 represents the stand profile after removal of tree number 6.
It is important to remember not to allow the harvest to exceed the amount of wood that the stand is adding through growth each year. This concept, known as "sustained yield management," assures a steady supply of firewood for the future. By eliminating the slow-growing species and reducing competition for sunlight, space, nutrients, and moisture, the best trees may even have higher growth rates. In fact, handled properly, it is possible that the volume of the annual harvest may increase.
Plans for conducting the third year, and subsequent harvests should be carried out in the same manner as the second year's operations.
Regenerating The Stand
During the second year's cutting operations, known as "selective thinning" or "thinning from above," some provision must be made for the regeneration of new trees. Keep in mind during the harvest that several young trees are already present in the general area of the one that is being cut. Identify some of the larger more vigorous seedlings and mark them with a highly visible string, strip of cloth, or flagging. These should be protected during the cutting operation.
Often many species of hardwoods will sprout from living stumps to produce a "coppice" or sprout stand (Figure 5). Some species sprout more than others and in general the younger trees sprout better than older ones. Many of the species that make excellent firewood, such as the oaks, sprout abundantly. Cutting the parent tree in late winter-early spring may also increase the chances for sprouting. Since the stump already has an extensive root system, and it is still alive, the first season sprouts will grow more rapidly than either planted or natural seedlings.
During the first spring each stump may produce numerous sprouts. Select the largest stem on each stump and pull or cut the remaining ones. This concentrates the future growth into one tree rather than several small ones that would be over crowded.
Since the stand will have large gaps left in the canopy many species of grasses, shrubs, nettles, and briars will invade the open area in the spring. This vegetation may not overtop the seedlings and sprouts that were left, but it does compete for nutrients and moisture. Controlling the undesirable vegetation through chopping, raking or chemical treatment should increase the growth rates of the favored seedlings
.Areas that are not in forest may be planted with species that are suitable for firewood. Some of these species are identified in FRC-13, School of Forest Resources and ConservationFact Sheet "Selecting Firewood." Many desirable fuel wood species are available from the Florida Division of Forestry for a small fee. Contact an urban or county forester, or county extension person for order forms. Seedlings of exotic or trees that are not native, such as Eucalyptus, are available for planting south of Orlando. One species, Eucalyptus viminalis , may be planted north of Orlando but there are risks since it is not totally frost-hearty. Most tropical introductions produce dense wood and grow rapidly when planted in the right climate and on suitable sites.
For hardwood plantings the land must be prepared almost as well as a field for agricultural crops. After planting, the seedlings must be protected from grazing animals and vegetative competition until they are well extablished. On suitable sites, trees like Eucalyptus may grow as much as 10 feet in height per year and will soon be out of the vunerable stage; others may need protection for 2 or 3 years.
Once the planted stands are established, they may be managed similar to the management scheme detailed previously for natural stands. The first harvest should be a low thinning to take out those trees that were suppressed. The second, and all future harvest should be based on the amount of wood that grew the previous year.
Management of a small woodlot is not that different from managing large tracts of land. The key to management is knowing how to inventory the initial volume and how to calculate the amount of product, in this case firewood, that is accumulating in the stand. By using the amount of wood that accrues each year as a guide to the amount of wood that is harvested annually, you can be assured of a continuous supply of firewood for years to come.
Other IFAS publications related to this topic that may be of interest:
Wood-Fueled Home Heating Systems -Which is Best? FRC Fact Sheet 10
Safe Home Use of Firewood, FRC Fact Sheet 1 1
Selecting Firewood, FRC Fact Sheet 13
Gathering, Preparing, and Storing Firewood, FRC Fact Sheet 1 6
A Guide to Selecting Existing Vegetation for Low-energy Landscapes, Circular 489
