Majestic trees, abundant wildlife, camping, wildfires, and timber production: all of these terms invoke thoughts of forestlands. Biomass, organic matter available on a renewable basis, is not one of the first things that comes to mind when forests are mentioned. Yet, the forests of the Southern United States provide a large renewable supply of biomass in the form of logging residues, small diameter trees, mill residues, and even short rotation woody crops.

The Southern Forest

While some of the material typically classified as "non-commercial" or not "merchantable" is currently being utilized, a large portion of this renewable natural resource is not utilized. Residues from the forest products manufacturing process are commonly used to create energy for the forest products industry.

Logging residues from commercial harvesting operations are typically left at the harvest site. Small diameter trees from thinning operations have traditionally entered into the pulpwood supply chain, but declining markets have limited this practice. As a result, these trees are either not harvested or necessary silvicultural thinnings are delayed, frequently resulting in overcrowded stands susceptible to fire, insects, and disease.

Why should we care about this excess biomass? Forest biomass can be used for generating electricity, producing biofuels, and producing biochemicals. Rising fuel costs, uneasiness about energy supplies, and dependence on foreign energy sources make renewable natural energy alternatives more attractive. Increased utilization of forest biomass can reduce dependence on non-renewable energy feedstocks while also reducing wildfire potential, slowing climate change, mitigating declining pulpwood markets, and improving forest health and sustainability. Forest biomass resources can also be used to create bio-based products. These are industrial products, other than feed or food, that utilize biological products, forestry materials, or renewable domestic agricultural (marine, plant, and animal) materials (USDA-ARS-BBCC 2003). These products include adhesives, solvents, plastics, inks, and lubricants.

Worldwide summary data from 1997 show that about 85% of global bioenergy consumption is in the form of firewood and charcoal to address heating and cooking needs. Most of the remaining 15% is black liquor, a by-product of the pulp and paper manufacturing process. This black liquor is used by the forest products industry to produce heat, steam, and electricity for a variety of purposes (IEA Bioenergy Task 31 2000). A startling difference exists between developing and developed countries. In Latin America, Africa, and Asia the prevalent use of bioenergy is for firewood and charcoal. In North America, Europe, and Japan bioenergy is primarily used for industrial purposes.

The following sections provide a background and understanding of biomass in the Southern United States. These sections include:

• The Southern United States and Potential for Bioenergy
• The Southern Forest

The Southern US

Stretching from the Atlantic Coast to the deserts of Texas and covering 834,937 square miles, the southern United States is a land of contrast and beauty. Sparkling beaches, majestic mountain ranges, fertile valleys, desert sands, pine forests, and hardwood forests can all be found in the South. The 13 southern states include Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, and Virginia (at right).

In 2003, estimates indicated that over 95 million people resided in the South, of which about one quarter live in rural areas (below left). These rural areas include over 60% of the counties and parishes in the southern states (Economic Research Service 2004).

Socioeconomic Conditions in the
Southern US

The South tends to lag behind the rest of the United States in terms of income and education. According to U. S. Census Bureau data (1999), the median household income in the South was approximately $5000 less than the U. S. average. Unemployment rates and the poverty rate tend to be above the national average. While a large percentage of the population are high school graduates, the average education level is still less than the national average. Approximately 21% of the population has a college degree, again slightly lower than the national average. On a positive note, the rate of home ownership in the South is higher than the national average. Regional and national socioeconomic averages are shown in the graphic below right.

Population Dispersal

The economy of the southern states is as varied as the people. Yet, natural resources serve as the economic base for many of the southern rural communities. These natural resources include the Southern forests. In 1997, the value of the Southern forest industry was calculated at $83 billion in total industry output (Abt and others 2002). The South provides over 60% of the U. S. timber supply and is home to over 1/3 of the wood products jobs in the United States. Wood products jobs make up 6% of the workforce in the South. The graph at right shows the percentage of manufacturing and wood products jobs in the South.

The Southern forest can serve as a source of unutilized woody biomass for the production of bioenergy and other bio-based products. This includes biomass from harvesting and logging residues, thinning, and wood processing residues. The quantities of these biomass sources are summarized in Table 1. This table was constructed by the Southeast SunGrant Center using Forest Inventory Analysis data and state forestry data. State biomass fact sheets are also available at Forest Bioenergy.

Percent of US Wood Products and
Manufacturing Jobs in the South

More information about the SunGrant Initiative and the regional centers can be found by visiting their websites: SunGrant Initiative, Southeast SunGrant Center, and the South Central SunGrant Center

If the trees and sawmill residues in the South now being used to produce wood pulp were instead converted to ethanol, approximately 6.5 billion gallons (162 million green tons [Johnson and Steppleton 2005] x 40 gallons per green ton) of transportation fuel would be added to the nations supply of transportation fuel. If only the difference in the Souths peak harvest rate of about 200 million green tons vs. its current harvesting rate of about 162 million green tons, roughly 1.5 billion gallons per year of ethanol would be available to meet the consumer demand of about 150 million gallons of gasoline per day. When forest residues are added, the volume of transportation fuel becomes even larger. Another incentive for using wood to produce cellulosic ethanol is that jobs are created in rural America, since that is where the wood is located. The countrys balance of payments is improved, since ethanol would replace imported oil, and the supply of ethanol is not affected by pipeline disruptions, since ethanol is not transported through pipelines.

Forest Cover in the United States

According to the Southern Forest Resource Assessment (Wear and Greis 2002), the Southern United States consists of more than 214 million acres of forest land. Approximately 13 million of these acres are classified as "reserved and other forest land," leaving 201 million acres in productive forest land. This number has remained relatively constant since the 1970s. Forest cover is depicted in green in the graphic of the United States, to the left. Timberland, defined as land capable of producing a commercial timber crop, makes up 93% of the Souths forest land. Over the past 20 years, increases in timberland, primarily from conversion of agriculture to timber, have occurred in Alabama, Arkansas, Mississippi, and Kentucky. Southern states losing timberland include Florida and Louisiana.

Change in Timberland

Forested acres for each state in 1982 and 1999 are presented in the graphic to the right.

Landowners controlling timberland in the South include a diverse group of nonindustrial private forest landowners, forest industry, government, and other public agencies. Government lands are classed as national forest and other public lands (Wear and Greis 2002). Other public lands include land administered by Native Americans, other federal agencies, state, county, and municipal agencies. Nonindustrial private forest landowners include corporations (not manufacturing wood products) and private individual owners. A recent addition to the nonindustrial forest landowner class includes timber investment management organizations (TIMOs). These organizations include banks, agribusiness, real estate investment and development firms, and insurance companies. TIMOs typicaly do not own timberland, but rather manage it for private landowners and investors. Forest industry land accounts for the most readily available source of raw material for the forest products industry.

Forest Ownership

According to the Forest Inventory Analysis (FIA) data, nonindustrial private individuals own 69% of the timberland in the South. Twenty percent of forest land is owned by forest industry. Approximately 11% is held as public timberland (at right). The public land is divided between 6% national forest and 5% other public lands. While each state differs in actual percentages, it is evident that most forest land is privately held.

Trends in the number of forest landowners indicate a 12% increase in landowners from 1978 to 1993. In 1993, there were 4.9 million forest landowners and a majority owned tracts smaller than 50 acres. Subsequently, there are more landowners owning smaller parcels of land in the South (Wear and Greis 2002).

The following sections describe the vast renewable resources that comprise the southern forest. Topics include:

• Forest Types
• Geographic Characteristics

The Forest Inventory Analysis (FIA) program of the USDA Forest Service recognizes five broad categories of forest types found in the South. Forest types are based on the species creating the majority of the live-tree stocking. Although the total acreage of timberlands has remained relatively stable, there has been a shift in forest types. The five forest types include planted pine, natural pine, mixed oak-pine, upland hardwood, and lowland hardwood.

Planted Pine

Planted Pine stands, or pine plantations, have been artificially regenerated by planting or direct seeding. These stands have at least 10% stocking and are classed as pine or other softwood forest type. Acreage in planted pine has been increasing steadily since 1950 and now stands at approximately 30 million acres (Wear and Greis 2002).

Natural Pine

Stands classed as pine or other softwood types that have not been artificially regenerated are considered Natural Pine stands. There must be at least a 10% stocking level. Natural pine stands have been decreasing steadily since 1950. These stands now account for approximately 34 million acres and continue to decrease (Wear and Greis 2002).

Mixed Oak-Pine Forest

The majority of the Mixed Oak-Pine stands consists of hardwoods, mainly upland oaks. Pines make up 25-50% of the stand stocking. Stocking will be at least 10%. Mixed oak-pine stands account for approximately 30 million acres in the Southern United States (Wear and Greis 2002).

Upland Hardwood Forest

Upland Hardwood forests are classified as oak-hickory or maple-beech-birch forest types. Stocking is at least 10%. These forests cover over 75 million acres in the South (Wear and Greis 2002).

Lowland Hardwood Forest

Forests classed as oak-gum-cypress, elm-ash-cottonwood, palm, or other tropical types are considered Lowland Hardwood forests. Again, the stocking rate is at least 10%. Approximately 30 million acres of the South are classified as lowland hardwood forests (Wear and Greis 2002).

Within the above timber types, there are approximately two million acres classified as non-stocked.

A Southern Hardwood Forest

The geography of a region can have a great impact on the regions productivity. Rocky mountains, mountain valleys, sandy shores, and dry plains all characterize areas in the Southern United States. Geographic characteristics play a role in the management decisions that are made at different sites. This section will describe three geographic characteristics affecting the management and productivity of the Southern forests. These characteristics include:

• Physiography
• Climate
• Soils

Physiography of the Southern United States

The forests of the South cover a vast range of territory ranging from the northern areas of Virginia and Kentucky to the forests of East Texas and Oklahoma. This area covers several different regions including mountains, coastal plains, and river valleys. The physiographic regions include:

• Coastal Plain
  • East Gulf Coastal Plain
  • West Gulf Coastal Plain
  • Lower Mississippi Alluvial Plain (Delta)
  • Florida Peninsula
  • Atlantic Coastal Plain
• Piedmont Province
• Blue Ridge Province
• Ridge and Valley Province
• Appalachian Plateaus
• Interior Low Plateaus
• Interior Highlands

For physiographic information on a specific state, click one of the following links: Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, and Virginia.

The Coastal Plain stretches from the Piney Woods of East Texas to the Atlantic shore. This area encompasses the West Gulf Coastal Plain, Lower Mississippi Alluvial Plain, East Gulf Coastal Plain, Florida Peninsula, and the Atlantic Coastal Plain (Walker and Oswald 2000).

Coastal Plain

The East Gulf Coastal Plain is characterized by terraces that run almost parallel to the Gulf of Mexico, while the West Gulf Coastal Plain includes low ridges and valleys runing parallel to the current coastline. These plains areas are home to the most productive pine forests in the South (Walker and Oswald 2000).

Interrupting these patterns are the Lower Mississippi Alluvial Plain and the Florida Peninsula. The Lower Mississippi Alluvial Plain, or Delta, runs north to south along the river and contains distinctive lowland hardwood forests. In contrast, the northern area of the Florida Peninsula rises abruptly from the sea floor. This area consists of marine terrace lowlands that are generally less than 100 feet in elevation. The central part of the peninsula, south of Tampa Bay, consists of broad plains less than 20 feet in elevation. At one time, this area was 80-85% swampland. Pines cover the higher areas of this part of the peninsula. The southern area of the peninsula consists mainly of non-forested lands (Walker and Oswald 2000).

The southern Atlantic Coastal Plain begins at the Delaware River and runs south to the Georgia coastline. This area is marked by a series of fluvial step-like and marine terraces that run parallel to the ocean. The northern area of the Atlantic Coastal Plain begins in central North Carolina and covers the northern part of the southern forest. Bays and estuaries divide the area into a series of peninsula-like extensions (Walker and Oswald 2000).

More information about the Coastal Plain can be found at the Wikipedia Free Encylopedia site.

Piedmont Province

The Piedmont Province covers an area from north of the Potomac River south to Alabama. This area consists of the eastern foothills of the Appalachian Mountains. Elevations in this province range from 300 to 1200 feet above sea level. Granite rests underneath approximately 20% of the area creating uplands and rock formations. Rolling hills, isolated rock features, and valleys dot the landscape of the Piedmont Province (Walker and Oswald 2000). More in-depth information about the Piedmont Province can be found in the Southern Appalachian Encyclopedia.

Blue Ridge Province

The Blue Ridge Mountains, a belt 5-80 miles wide, extend from the southern Appalachians in Virginia southward to Georgia. The area ranges in elevation from 1000 to 4000 feet above sea level, making it the most rugged topography east of the Rocky Mountains. The province appears as a single ridge or flanked by lesser ridges in the north, while in the south closely spaced ridges form a rugged landscape with a prominent escarpment overlooking the Piedmont Province. The rugged area has discouraged many settlers but it is home for many craving the isolation provided by the land (Walker and Oswald 2000). More information about the Blue Ridge Province can be found in the Southern Appalachian Encyclopedia.

Ridge and Valley

Lying between the Blue Ridge Mountains and the Appalachian Plateaus, the Ridge and Valley Province is an area 50-75 miles in width. Even crested ridges, separated by narrow valleys, make up this area. The rock base consists of shale, sandstone, and limestone. American chestnut forests once covered much of this area. Because of the high soil fertility, agriculture now dominates the valleys. Power and flood control projects also dot the landscape (Walker and Oswald 2000). The Ridge and Valley Province is covered in more detail in the Southern Appalachian Encyclopedia.

Appalachian Plateaus

Geological uplifts within the Southern Appalachian Mountains are referred to as the Appalachian Plateaus. Eastern boundary elevations range from 500-1000 feet above sea level. The western landscape is cut into buttes and promontories by the many streams running through the area (Walker and Oswald 2000). More in-depth information regarding the Appalachian Plateaus can be found in the Southern Appalachian Encylopedia.

Interior Low Plateaus

To the west of the Appalachian Plateaus, lie the Interior Plateaus. The plateaus form a broad upwarp running parallel to the Appalachain Mountains. Erosion has eaten up much of the original soil to create basins such as those around Nashville and Lexington. These areas are now primarily farmland (Walker and Oswald 2000).

The U. S. Geological Survey website has more information related to the Interior Low Plateaus.

Consisting of the Ozark Plateaus and the Ouachita Province, the Interior Highlands of the southern forest are located in Oklahoma and Arkansas. To the north, the Ozark Plateaus rise 2200 feet above sea level. Regional streams dissect the plateaus creating flatland prairies between the rivers (Walker and Oswald 2000).

Interior Highlands

The Arkansas River separates the Ozark Plateaus from the Ouachita Province in the southern part of the Interior Highlands. The topography of the area is similar to the Ridge and Valley Province. Elevations range from below 1000 feet to 2600 feet near the Oklahoma border in the West (Walker and Oswald 2000).

The U. S. Geological Survey website has more information related to the Interior Highlands.

Climatic Regions of the U. S.

With such a large geographic region, it is only logical that the climate of the Southern forest would vary. Yet, the majority of the Southern forest is characterized as a humid subtropical climate. This climatic region is known for abundant precipitation and high temperatures. The exceptions to this rule are the mountains in the northern regions where the climate and forests can be like that of coastal Maine (Walker and Oswald 2000). Major climate regions of the United States are shown to the right.

Average US Temperatures - 2004

The southern growing season averages 180 days or more. In southern Florida, the season is about 320 days. High temperatures over the course of the growing season provide abundant energy for growth, making the South ideal for timber production.

Average Annual US Precipitation

Average U. S. temperatures are depicted in the figure to the left. Some species in the region may have six flushes of growth, in contrast to three or fewer flushes in other suitable growing regions.

Precipitation in the South is generally consistent throughout the region and annually averages 40-60 inches. Average annual precipitation is shown in the figure to the right. The southerly mountains may receive 80 inches, while the northerly mountainous areas may receive upwards of 120 inches of precipitation. Yet, the South is not immune to "dry spells." It is during these dry times that fire, disease, and pest damage can be extremely harmful to the forest (Walker and Oswald 2000).

Soils are an important component of the forest landscape. Soils perform several different functions in the forest landscape including habitat for soil organisms, recycling systems for nutrients and organic wastes, provisions of water supply and its purification, and as a medium for plant growth (Brady and Weil 1999). Different soil types perform these functions in different ways. Some soils may be better growing mediums while others provide better organism habitat. For example, sandy soil allows water and nutrients to flow through the soil, while clay soil creates an impenetrable soil surface. Clay soil is generally not a good soil for use as an engineering medium because of its tendency to shrink and swell based on the water content of the soil. Yet, chemicals and nutrients are not held by sandy soil in plant-available form as they are by a clay soil.

Soil Development and Weathering

With that in mind, it is important to differentiate between soil types. Soils are classified into six different taxonomic categories including 1) order, 2) suborder, 3) great group, 4) subgroup, 5) family, and 6) series.

We will limit our discussion to the top level classification or soil orders. Soil orders are differentiated by the presence or absence of diagnostic horizons or features that reflect major courses of development. There are twelve different soil orders. Order names provide a characteristic of the soil and end in sols (from the Latin solum, soil). Temperature and moisture are the climatic factors that most frequently affect the soils in the area. It should be noted that since soil orders are the most general level of soil classification, variation of soil characteristics within orders is quite large and, therefore, should be used accordingly. The diagram to the right shows the typical temperature and moisture factors related to each soil order. The table below can serve as a key reference to identifying soil orders. It provides major diagnostic features for each order.

Soil Diagnostic Features

Eight of the twelve soil orders are present in the forests of the Southern United States. Orders in small amounts include Histosols, Entisols, Mollisols, and Spodosols. The prominent soil orders, listed in order of productive capacity, in the South include:

• Alfisols
• Inceptisols
• Ultisols
• Vertisols

Photographs and distribution maps of dominant soil orders can be found on the Natural Resources Conservation website and at the University of Idaho website.

Soil surveys provide soil maps and interpretations needed in giving technical assistance to natural resource managers; in guiding decisions about soil selection, use, and management; and in planning research and disseminating the results of research. The surveys also are used in educational programs about soil use and conservation. County-level soil surveys can be found at the NRCS website. Additional assistance is available from USDA Service Centers. These centers are designed to be a single location where customers can access the services provided by the Farm Service Agency, Natural Resources Conservation Service, and the Rural Development agencies. Service centers for each state are shown on the USDA website. The site will provide the address of a USDA Service Center and other Agency offices serving your area along with information on how to contact them.

The conservation of forest soils is an important component of a sustainable bioenergy and bio-based products industry in the Southern United States. A more detailed discussion of forest soils and their role in the bioenergy and bio-based products value chain is contained in Soil Values in the Environmental Sustainability section.

Alfisol Soils in the United States

Alfisols occur in the western areas of the southern forest. These soils tend to be strongly weathered, well developed, and contain a subsurface horizon in which clays have accumulated. They typically develop under under native deciduous forests. Coloring tends to run from dark brown to a light gray horizon as the soil evolves. The combination of favorable climate and high native fertility allows Alfisols to be very productive soils for both agricultural and silvicultural uses (Brady and Weil 1999).

Inceptisol Soils

Inceptisols are common in the eastern regions of Tennessee, North Carolina, Kentucky, and Virginia and occur under a wide range of ecological settings (Brady and Weil 1999). These soils are considered young and at the beginning of geological weathering and profile development, exhibiting minimal horizon development. They are often found on fairly steep slopes, young geomorphic surfaces, and on resistant parent materials. Productivity of these soils varies greatly. A sizeable percentage of Inceptisols are found in mountainous areas and are used for forestry, recreation, and watershed.

Ultisol Soils

Ultisols are the dominant soil type found in the southern forest. The "red clay" soils of the southeastern United States are examples of Ultisols. These soils are generally formed under forest canopy, explaining why they are the dominant forest soil in the south. Iron and aluminum are constantly being leached from the soil surface into the subsoil below often resulting in the lighter coloring at the soil surface and the strong yellowish or reddish colors at the lower horizons. Subsoils also tend to be stiffer due to the downward movement of iron in the soil (Walker and Oswald 2000). Ultisols are acidic in nature and quite productive under good management (Brady and Weil 1999). However, high acidity and relative low availability of calcium, magnesium, and potassium render these soils poorly suited for continuous agriculture without the use of fertilizer and lime.

Vertisol Soils

Vertisols are most commonly found in eastern Mississippi, western Alabama, and southeast, south, and central Texas. These are clay soils characterized by shrinking and swelling as moisture content varies. The clay content is generally present at 1 meter or more (Brady and Weil 1999). These soils are generally sticky during the wet season and hard in the dry season, so they require special management practices regardless of the type of equipment used. Shrink-swell processes in Vertisols are related to the total clay content, the content of fine clay, and mineralogy. They generally have high clay content (50-70%), with a relatively large proportion in the fine clay fraction.