Contrary to what many may think, the hardwood timber supply in the United States has been improving over the last sixty years, and it looks to continue that trend although some new challenges are starting to take shape. Overall, this is good news for those in the forest products industry as well as consumers and others concerned about the potential of hardwood forest loss.
A historical analysis is important to understand what is going on across the nation’s hardwood forests. The U.S. Forest Service Inventory and Analysis (FIA) unit conducted the first comprehensive national assessment of U.S. timber resources back in 1953. At that time, eastern hardwood sawtimber volume was slightly above 400 billion board feet. While this appears to be a large number, it was likely significantly smaller than sawtimber volume in the years prior to 1850. After the Civil War, the U.S. economy grew and timberland was cut over to produce lumber, crossties, fuel wood and charcoal. Much of the cutover land would transition to agricultural uses such as food crop to feed an expanding population or hay to feed horses, the major form of personal transportation. The advent of the Great Depression, the transition from horses to automobiles, and higher yielding agricultural practices caused marginal agricultural land to revert back to forests in the 1930s to the 1950s. These changes set the stage for what I call the miraculous recovery.
Since 1953 hardwood sawtimber on timberland (land that can be harvested an capable of growing timber) has been steadily increasing (Fig. 1) and reached over 1.4 trillion board feet in 2011. In the 1950s, 60s and 70s much of this increase was the result of smaller diameter pole timber growing to sawtimber size trees of at least 11 inches in diameter (in growth). Much of the increase in recent years is sawtimber size trees adding volume (accretion). What is most notable in Figure 1 is the steep rise in the growth of sawtimber volume since the late 1990s.
One potential cause of this rise might be changes in FIA procedures and methods, but it is more likely the result of the declining demand for hardwood products that began in the current century and the continued growth of sawtimber size material. The volume would even be higher if acreage had not been transferred from the timberland category into reserve status such as wilderness areas. In 2011 over 11% of the hardwood sawtimber on forested land in the Eastern United States was in reserve.
The 1953 assessment provided a bench mark for sawtimber volume information but information on the volume of specific species groups was limited to six species groups. In 1963 a second forest assessment was conducted and sawtimber volume information was provided for 16 species groups (Table 1).
Between 1963 and 2011 all species groups had increases in sawtimber volume, and yellow poplar, red maple and cottonwood/aspen had the largest increases. While these three species groups contain relatively fast growing species, there are other factors that have caused these large increases.
Much of the increase in yellow poplar volume was the result of regeneration on abandoned farmland and the loss of the competitive American chestnut due to a fungus native to China. The most predominant soft maple is red maple. Red maple is very competitive on Appalachian and northern sites after a diameter limited cut or other partial cutting practices. The two most common species in the cottonwood/aspen species group are quaking aspen and eastern cottonwood. Quaking aspen is very competitive on bare soils in the northern region but is short lived without disturbance and is considered a successional species. Eastern cottonwood is found in wet areas and grows very quickly.
Yellow birch, tupelo/blackgum, and beech had relatively small increases in sawtimber inventory between 1963 and 2011. Nearly 30% of the yellow birch sawtimber volume has been placed in reserve but exactly when this happened is unknown. This figure is nearly 50% higher than hard maple and beech, the next two species with large volumes of reserve. Major species in the tupelo/blackgum groups are swamp tupelo, water tupelo, and blackgum (also known as black tupelo). All these species have a relatively low rate of growth. Swamp and water tupelo grows on bottom lands which in some cases have been converted to soybeans. Blackgum grows on upland site but is somewhat uncompetitive and can die before reaching sawtimber size. Beech sawtimber volume has been affected by fungus induced mortality and a relatively high volume being placed in reserve.
While the growth in hardwood sawtimber on timberland has been substantial, there are several factors that could affect future growth including non-native disease and insect mortality, land conversion, and adversely high deer populations. Various non-native fungi have changed the eastern forest over the last 150 years with chestnut blight and Dutch elm disease causing the greatest damage. Gypsy moth which is a non-native insect periodically decimates portions of eastern hardwood resources and has contributed to widespread change in forest composition in areas including portions of Pennsylvania. Currently the emerald ash borer has killed large numbers of green ash trees in Michigan and is now moving to many other states primarily through infected firewood.
From the colonial times to the early 20th century large portions of land were converted from forest land to agricultural land. This trend was reversed during the Great Depression as marginal farm land reverted back to forest. Since 1953 forested land has increased by around 10% , however there are emerging issues that could cause a reduction in timberland.
Continued high prices for agriculture commodities may cause forest land to be made into farm land, but the most probable factor is land converting from forest land to residential land, especially in the Northeast. This conversion of forest land to residential property has caused some land owners to voluntarily give their lands to preservation organizations and other NGO’s so it will not be developed by their offspring to pay inheritance tax.
Over the last 30 years white tail deer populations have expanded and this expansion is affecting forest regeneration and the species composition of future forests. In the Allegany region of Pennsylvania deer have been eating cherry sprouts and saplings to the point that some areas become covered in ferns that the deer do not eat.
By all indications more sawtimber size hardwood trees could be harvested form the eastern forest at sustainable levels. Still the methods used in harvesting have and will continue to have an impact on the species that will regenerate and also could affect future timber quality. Diameter limit or other selective harvesting methods result in more shade tolerant species such as red maple to regenerate and hinders the regeneration of species such as yellow birch.
Northern red oak has not been regenerating on many of the better sites for several decades without silvicultural intervention such as a prescribed burn to kill off competing species. Damage to roots, limbs and stems during the harvesting process may cause damage induced heartwood such as the dark wood in hard maple or the purple and black wood in yellow poplar.
Selective cutting also may result in adventitious budding causing pin knots and inconsistent ring count (fewer rings per inch after partial canopy removal). However, it is up to the individual land owners to make the final decision on the harvesting of their trees.
