Post from Minister Stephen's Blog:
Reclaiming Surface-Mined Land with Paulownia Trees
| By Minister Stephen - Apr 27, 2008 2:46:53 PM ET |
| Also listed in: Certified Green Partners | Earth Healers | National Tree planting effort | Peace Portal | The Anaheim Climate Syndicate. | Tree Huggers |
Guidelines for Reclaiming Surface-Mined Land using PAulownia
The purpose of this paper is to detail the practical, cost-effective guidelines used by the Paulownia Reforestation Project (PRP,) Farr Better Trees, and Plan-it, Plant-it, Planet for reclaiming surface-mined land to forestland. Successful reforestation is primarily a function of selection, placement and grading of the surface-mine soil material, hydroseeding with tree-compatible grass and legume covers, tree species selection, and seedling handling and planting techniques. The following guidelines were developed from research and practical experience.
Principles of Reforestation
The eastern deciduous hardwood forest with its hundreds of species of plants and animals is one of the most complex plant systems in North America. After mining and land reclamation, this complex forest, given enough time, will be restored to its original function and structure through a process called forest succession.
Forest succession is a natural process whereby, following disturbance, the forest regains its original composition through a slow process of species replacement and site amelioration. When land is surface mined, the entire forest including shrub layer, tree canopy, root stocks, seed pools, animals, and micro organisms, is removed. It is not possible to instantaneously restore the original forest of red oak, sugar maple, Fraser magnolia, cucumber tree and other mid to late-successional species. Mined land cannot be artificially prepared for these species. Instead, pioneer species such as leguminous trees and shrubs (black locust, autumn olive, and bicolor lespedeza) and Paulownia species that can tolerate a wide range of acidity, fertility, moisture, and temperature should be established first. The pioneer species will eventually yield to the more site-sensitive hardwoods. In the meantime, the mine soil is being conditioned, nitrogen and organic matter are being incorporated, populations of macro and micro plants and animals are increasing, a more diverse wildlife habitat is being created, and valuable wood products are being produced. The rate at which natural forest succession proceeds depends on the nature of the reclaimed site and adjoining undisturbed sites. In any case, it would require one to two hundred years for the oaks and other mid to late successional hardwoods to dominate if forest restoration were left entirely to nature.
PRP reforestation procedures are designed to accelerate forest succession while providing for the immediate concerns of land stabilization, erosion control, bond release, and economic considerations of land owners. A combination of grasses, legumes, nurse shrubs and trees, and crop trees are established more or less simultaneously. Each plant type serves a specific reclamation function then yields to another plant type. Hydroseeded grasses emerge first to quickly stabilize the minesoil surface. Grasses will then yield to legumes when applied nitrogen is minimized. The slow-starting, ground-sprawling legumes allow trees to become established and free to grow before totally covering the site. The legumes enrich the site and eventually give way to the tree cover. Nurse trees and shrubs condition the site for the crop trees and yield to the crop trees as they close canopy. If pines are established at recommended densities, hardwood species will invade and will be poised for growth when the pines are removed for their economic value. This process of matching plant species to site conditions, matching plant species for their compatibility with each other, and managing tree stands to accomplish certain objectives as they develop over time, is called reforestation silviculture.
Forest Land Postmining Land Uses
Since about 1985, almost all reclaimed land planted with trees has been designated as "unmanaged forest land" (or non-commercial forestland) in reclamation operations permits. Although seldom used, there is another forestland post-mining land-use option referred to as "commercial forest land." Although bond release requirements specified by state regulations are similar for commercial and non-commercial forest land, there are some subtle differences. Typically, unmanaged forestland is planted with white pine and various nitrogen-fixing shrub and tree species. This species composition provides for good forestry, wildlife, and environmental benefits with little or no management input after establishment. The "commercial forest land" option provides the opportunity to use alternative tree species or reclamation practices to achieve a specific management objective. Landowners who want to establish Christmas tree farms, Paulownia plantations, or some timber species other than white pine should designate commercial forestland as the post-mining land use. As with any land-use designation, the coal company must submit a simple management plan which explains how the proposed post-mining land use is to be achieved. Additionally, a copy of the comments by the landowner concerning the proposed use must be submitted. These documents are required to verify that the landowner is committed to the proposed commercial forestland, and that it can be reasonably achieved.
Bond Release Requirements
The guidelines offered in this paper were developed to increase the probability of timely bond release for the coal operator as well as to ensure the establishment of productive forest land. Of particular importance are requirements relative to final surface grading, ground cover, and number of trees per acre required.
Final surface grading
Through the years, the establishment of smoothly-graded slopes with lush vegetation during the first year has become the standard goal for reclamationists. Unfortunately, land reclaimed in this way is often compacted by excessive grading, and the ground cover vegetation is too dense for tree establishment. Most natural forested landscapes in, for example, Southwest Virginia are uneven and many are strewn with rocks and boulders. These surface conditions are consistent with forests and forest management. Natural forest soils are rough and loose which allow deeply-rooted woody species to become established and grow unimpeded. After groundcover and tree establishment, small to medium gullies need not be filled unless they are associated with sedimentation problems. Small to medium gullies may interfere with hayland/pasture uses, but do not interfere with forestry and wildlife habitat. Mine-soil compaction resulting from gully repair is counterproductive.
Ground cover establishment
When trees are planted for "wildlife management, recreation, shelterbelts or forest uses other than commercial forest land," the success standard is 90 percent. This means that coal companies must achieve 81 percent cover for bond release, which is 90 percent of the standard. Ground cover for commercial forestland must only be adequate to control erosion and achieve the specified land use.
Number of trees per acre
The number of trees per acre and species selection differs between commercial forestland and non-commercial forestland. For commercial forestland, there must be at least 400 commercial trees/acre plus 40 wildlife trees or shrubs (a minimum of 440 trees/acre). In Virginia, white pine is the most common commercial species. Other species could be considered commercial as long as the landowner submits a letter of intent to manage alternative species for a commercial purpose, such as Paulownia. For non-commercial forest land, there must be at least 400 trees/acre of which at least 40 must be wildlife trees or shrubs. Native invading hardwoods count toward bond release as long as they are 1-ft tall.
Selection, Placement, and Grading of Mine Soil Material
Carefully-constructed mine soils can be deeper and more fertile than some of the natural soils found in mountainous terrain. Natural soil in many steeply sloping areas of the Appalachians is thin and difficult to recover, store, and replace during reclamation. "Topsoil substitutes" containing large amounts of blasted overburden materials are allowed by law and can be used successfully as plant-growth media. But in order to be as productive as natural soils, the spoil materials must have desirable physical and chemical properties conducive for good growth of deeply-rooted trees. The surface four feet of mine soil material should be easily weatherable so that most rocks and boulders decompose to fine soil materials within a few years. The soil texture of the fine-earth fraction should be loamy to sandy, and the mine-soil should be low in total salts and moderately acid. Most important, the mine-soil must also be left uncompacted to a depth of four feet.
Research studies and many observations of reclaimed sites in Virginia, West Virginia, and Kentucky show that tree survival and long-term growth is excellent on oxidized, moderately-acid, sandstone-derived mine soils. In general, siltstone and shale that occur directly above or below coal seams should be avoided. These rock types usually have high levels of soluble salts, a high pH, and compact to greater densities w hen trafficked. Some of the blue-gray sandstones that occur further below the surface are acceptable for forest land. However, some of these spoils weather very slowly and should only be selected when brown sandstone is not available.
Reclaimed mine soils must be left loose and uncompacted to ensure successful establishment and long-term growth of trees. Prior to seeding ground covers, reclaimed sites are often cleared of large boulders, gullies are filled, and the surface is graded smooth and "tracked in" with bulldozers to create a seedbed for ground covers. This treatment may be conducive to hayland/pasture establishment, but it is very undesirable for tree establishment and long-term forest growth. Powell River Project research shows that mine soil compaction is the greatest single factor limiting the success of reforestation. When soils are excessively graded and tracked in, trees cannot be planted deeply enough. This results in poor survival rates and permanently reduces the mine soil quality. {mosimage} Compacted mine soils reduce water infiltration, reduce plant available water, increase sheet erosion, and restrict root growth.
When forest land is the post-mining land use, final grading should be limited to the extent needed to ensure the stability of slopes. On level and gently sloping areas, the spoil placement process should be planned so that once a pile is dumped in place, no more equipment passes over it except for a final, light grading. Mine soil compaction due to grading can be minimized by using small dozers with low ground pressures and grading only when mine soil materials are dry. Natural forest land in the Appalachians is usually rougher than pastureland. Reclaimed forestland with boulders and uneven surfaces will not adversely affect forest management activities.
Importance of Mine Soil Quality for Forests
The federal Surface Mine Reclamation and Control Act (PL 95-87) requires that mined land be restored to its original level of productivity. For example, in the Interior Coal Region of the Midwest, land capable of producing 100 bu/acre corn prior to mining must be able to produce 100 bu/acre after mining and reclamation. In the Appalachian coalfields, in a similar manner, mined forestland should be restored so that mine soils are capable of producing the same amount of wood after mining as before.
Studies on the Powell River Project show that mine soils covering a wide spectrum of quality are being constructed. This productivity spectrum is represented by sites on which trees are unable to survive, to sites on which trees are growing at rates faster than on natural, undisturbed soils.
Importance of Compatibility of Ground Covers with Trees
Unlike standard hayland and pasture forages that are lush during the first year and gradually decline without additional fertilizer, tree-compatible covers are designed to be relatively sparse during the first year and become increasingly lush by the second and third years. This allows tree seedlings to emerge above the ground cover and ensures their survival. Despite relatively-low recommended seeding rates, 90 percent ground cover can be achieved for partial bond reduction during the first year. Most of the first-year cover results from the annual grasses, while the legumes dominate after several years. Birdsfoot trefoil and Appalow lespedeza emerge slowly by producing only a few plants per square foot, and these plants are generally less than six inches tall after the first season. By the third season, however, they develop into a complete cover replacing the grass and filling in under emerging trees. These legumes persist beneath the trees, increasing organic matter and nitrogen levels for several years until trees eventually shade them out.
Another purpose of low ground cover seeding rates is to allow the invasion of native plant species such as yellow poplar, red maple, birch and other light-seeded trees. Dense ground covers prevent the establishment of native plants. An additional benefit of a tree-compatible cover is that some tree and shrub species can be established by direct seeding. When conventional ground covers are used, direct-seeded trees will not emerge and survive due to dense shading.
Tree Species Selection
A sufficient number of desirable trees must be established during reclamation in order to achieve multiple uses from a developing and mature forest. Two categories of tree species are recommended: 1) crop trees and 2) N-fixing nurse trees such as Paulownia (or shrubs). Crop trees are long-lived species that offer value to landowners as saleable forest products. Nurse trees are planted to assist the crop trees by enhancing the organic matter and nitrogen status of the soil and improving soil physical properties. Nurse trees will die or can be cut out after 15 to 20 years when crop trees need additional growing space. Nurse trees help achieve the minimum number of stems and ground cover required for bond release, and they provide food and cover for wildlife.
Nurse-tree Selection
The nurse tree and nurse shrub species recommended for reclamation planting are N-fixing plants that benefit crop trees and provide food and cover for wildlife. Nurse trees contribute to ground cover requirements and help stabilize the site.
Hydroseeding Trees
To reduce the expense of handplanting, nurse species can be hydroseeded with the ground cover. Most nurse species can be established by direct seeding provided an appropriate ground cover mix is used. Many direct-seeding efforts have failed in the past because the accompanying ground cover was too tall and dense for tree germinants to become established. A disadvantage of hydroseeding nurse trees is the loss of control with respect to their number and spacing. Too many nurse trees can reduce the amount of growing space for crop trees. Seed for many species requires cold storage treatment (stratification) to break seed dormancy before spring seeding. This pretreatment is necessary to mimic the effect cold winter temperatures would have on the seed. Different tree species have slightly different stratification requirements; however, all species recommended can be stratified by following these steps: soak in water for 24 hours, drain the water, mix the seed in a plastic bag with moist sand or peat, then store the bag in a refrigerator (40o F) for 30 to 60 days. Stratified tree seed should be sown in spring through early summer (March 15-June 30). Fall and winter sowing could result in mortality of the germinating seed due to cold temperatures. For late summer and fall applications, unstratified seed should be used. Unstratified seed will receive its cold treatment during the winter and then germinate in the spring{
Tree Seedling Handling and Planting Techniques
The successful establishment of trees is highly dependent on selecting good nursery stock, proper handling before planting, and proper planting techniques. Poor survival and poor early growth are usually the result of improper handling or planting. Seedlings should not be planted if the roots are dry . Air-dried roots have less growth potential than roots that have stayed moist. Stressed seedlings may survive if planted, but growth will be reduced. Seedlings should be graded prior to planting so that only healthy seedlings are used. Healthy pine seedlings should have a root collar diameter of 4/32 to 9/32 inches. Very small pine seedlings (under 4/32 inches diameter) and very large seedlings (over 10/32 inches in diameter) do not survive well. Very large seedlings are difficult to plant correctly. Root pruning of pine seedlings is not recommended; there is a tendency to chop off too much of the root system. With root pruning now being done in the nursery beds, none is needed at the planting site. Overall survival is better when no root pruning is done by tree planters.
Proper seedling storage and handling before planting is critical to ensure good survival and growth. Seedlings must not be allowed to get hot or dry. If planting is delayed, the bags of seedlings should be wetted and roots dipped in a moisture-retaining gel specifically designed to keep roots from drying. The seedlings should then be rebundled and placed in cold storage (32-36o F) for no more than four weeks. If cold storage is not possible, they should be stored in a cool damp basement for no more than a week. At temperatures over 40o F, mold develops and seedlings are killed. Without cold storage, it becomes more important to dampen the roots as soon as they are delivered.
Seedlings should be planted as soon as possible in late winter or early spring (February-April) after the ground has thawed. Early planting is preferred because the soil is usually wetter and more conducive to root growth. Root growth decreases during periods of rapid shoot elongation; therefore, it is important that the seedlings be planted early in the season so roots can become established before the weather turns warm enough for shoot growth to begin. During planting, crew leaders need to make certain that planters do not expose roots to the air by carrying seedlings in their hand. Seedlings should be carried in a planting bag and not removed until the planting hole is opened. Planting holes must be opened deeply enough so that the roots can be evenly spread in the hole. Seedlings should be planted about one inch deeper than grown in the nursery. Finally, the planting hole must be completely closed since any air spaces around the roots will cause those roots to die.
Planting crews should be given instructions on proper planting techniques prior to planting, and crew leaders should start quality checks immediately so that needed corrections can be made before much of the area is planted. This involves careful lifting of planted seedlings on random plots to check on seedling health, tightness, depth of planting, straightness, spacing, and density. Seedlings are carefully replaced after each one is inspected.
Establishing Trees in Dense Ground Cover
Sometimes it is necessary to establish trees in an existing cover of dense grasses or legumes such as K-31 tall fescue or Serecia lespedeza. In order to ensure survival and good growth, herbicides and slow-release fertilizer pellets are recommended. Chemical weed control (herbicides applied via backpack sprayer) helps maintain the seedlings free of overtopping competition. By controlling dense vegetation with non-chemical solutions, seedlings will receive adequate sunlight and more soil water to ensure their survival. In conjunction with weed control, slow-release fertilizer pellets can speed growth during the first few years to help the trees grow above surrounding grasses. Fertilizer pellets should be placed in the planting bar closing hole (never in the planting hole) about two inches from the roots during planting. Fertilizer pellets slowly decompose and release nutrients needed by the trees. By using pellets it is possible to selectively fertilize seedlings without fertilizing surrounding grasses. In many cases, dense ground covers of fescue and clover will decline after two or three years, after which time trees can be more easily established.
NOTE: The greater content of this document has been excerpted and adapted from:
Publication Number 460-123, January 1997 Dept. of Forestry, Virginia Tech
Authors: James A. Burger and John L. Torbert
The purpose of this paper is to detail the practical, cost-effective guidelines used by the Paulownia Reforestation Project (PRP,) Farr Better Trees, and Plan-it, Plant-it, Planet for reclaiming surface-mined land to forestland. Successful reforestation is primarily a function of selection, placement and grading of the surface-mine soil material, hydroseeding with tree-compatible grass and legume covers, tree species selection, and seedling handling and planting techniques. The following guidelines were developed from research and practical experience.
Principles of Reforestation
The eastern deciduous hardwood forest with its hundreds of species of plants and animals is one of the most complex plant systems in North America. After mining and land reclamation, this complex forest, given enough time, will be restored to its original function and structure through a process called forest succession.
Forest succession is a natural process whereby, following disturbance, the forest regains its original composition through a slow process of species replacement and site amelioration. When land is surface mined, the entire forest including shrub layer, tree canopy, root stocks, seed pools, animals, and micro organisms, is removed. It is not possible to instantaneously restore the original forest of red oak, sugar maple, Fraser magnolia, cucumber tree and other mid to late-successional species. Mined land cannot be artificially prepared for these species. Instead, pioneer species such as leguminous trees and shrubs (black locust, autumn olive, and bicolor lespedeza) and Paulownia species that can tolerate a wide range of acidity, fertility, moisture, and temperature should be established first. The pioneer species will eventually yield to the more site-sensitive hardwoods. In the meantime, the mine soil is being conditioned, nitrogen and organic matter are being incorporated, populations of macro and micro plants and animals are increasing, a more diverse wildlife habitat is being created, and valuable wood products are being produced. The rate at which natural forest succession proceeds depends on the nature of the reclaimed site and adjoining undisturbed sites. In any case, it would require one to two hundred years for the oaks and other mid to late successional hardwoods to dominate if forest restoration were left entirely to nature.
PRP reforestation procedures are designed to accelerate forest succession while providing for the immediate concerns of land stabilization, erosion control, bond release, and economic considerations of land owners. A combination of grasses, legumes, nurse shrubs and trees, and crop trees are established more or less simultaneously. Each plant type serves a specific reclamation function then yields to another plant type. Hydroseeded grasses emerge first to quickly stabilize the minesoil surface. Grasses will then yield to legumes when applied nitrogen is minimized. The slow-starting, ground-sprawling legumes allow trees to become established and free to grow before totally covering the site. The legumes enrich the site and eventually give way to the tree cover. Nurse trees and shrubs condition the site for the crop trees and yield to the crop trees as they close canopy. If pines are established at recommended densities, hardwood species will invade and will be poised for growth when the pines are removed for their economic value. This process of matching plant species to site conditions, matching plant species for their compatibility with each other, and managing tree stands to accomplish certain objectives as they develop over time, is called reforestation silviculture.
Forest Land Postmining Land Uses
Since about 1985, almost all reclaimed land planted with trees has been designated as "unmanaged forest land" (or non-commercial forestland) in reclamation operations permits. Although seldom used, there is another forestland post-mining land-use option referred to as "commercial forest land." Although bond release requirements specified by state regulations are similar for commercial and non-commercial forest land, there are some subtle differences. Typically, unmanaged forestland is planted with white pine and various nitrogen-fixing shrub and tree species. This species composition provides for good forestry, wildlife, and environmental benefits with little or no management input after establishment. The "commercial forest land" option provides the opportunity to use alternative tree species or reclamation practices to achieve a specific management objective. Landowners who want to establish Christmas tree farms, Paulownia plantations, or some timber species other than white pine should designate commercial forestland as the post-mining land use. As with any land-use designation, the coal company must submit a simple management plan which explains how the proposed post-mining land use is to be achieved. Additionally, a copy of the comments by the landowner concerning the proposed use must be submitted. These documents are required to verify that the landowner is committed to the proposed commercial forestland, and that it can be reasonably achieved.
Bond Release Requirements
The guidelines offered in this paper were developed to increase the probability of timely bond release for the coal operator as well as to ensure the establishment of productive forest land. Of particular importance are requirements relative to final surface grading, ground cover, and number of trees per acre required.
Final surface grading
Through the years, the establishment of smoothly-graded slopes with lush vegetation during the first year has become the standard goal for reclamationists. Unfortunately, land reclaimed in this way is often compacted by excessive grading, and the ground cover vegetation is too dense for tree establishment. Most natural forested landscapes in, for example, Southwest Virginia are uneven and many are strewn with rocks and boulders. These surface conditions are consistent with forests and forest management. Natural forest soils are rough and loose which allow deeply-rooted woody species to become established and grow unimpeded. After groundcover and tree establishment, small to medium gullies need not be filled unless they are associated with sedimentation problems. Small to medium gullies may interfere with hayland/pasture uses, but do not interfere with forestry and wildlife habitat. Mine-soil compaction resulting from gully repair is counterproductive.
Ground cover establishment
When trees are planted for "wildlife management, recreation, shelterbelts or forest uses other than commercial forest land," the success standard is 90 percent. This means that coal companies must achieve 81 percent cover for bond release, which is 90 percent of the standard. Ground cover for commercial forestland must only be adequate to control erosion and achieve the specified land use.
Number of trees per acre
The number of trees per acre and species selection differs between commercial forestland and non-commercial forestland. For commercial forestland, there must be at least 400 commercial trees/acre plus 40 wildlife trees or shrubs (a minimum of 440 trees/acre). In Virginia, white pine is the most common commercial species. Other species could be considered commercial as long as the landowner submits a letter of intent to manage alternative species for a commercial purpose, such as Paulownia. For non-commercial forest land, there must be at least 400 trees/acre of which at least 40 must be wildlife trees or shrubs. Native invading hardwoods count toward bond release as long as they are 1-ft tall.
Selection, Placement, and Grading of Mine Soil Material
Carefully-constructed mine soils can be deeper and more fertile than some of the natural soils found in mountainous terrain. Natural soil in many steeply sloping areas of the Appalachians is thin and difficult to recover, store, and replace during reclamation. "Topsoil substitutes" containing large amounts of blasted overburden materials are allowed by law and can be used successfully as plant-growth media. But in order to be as productive as natural soils, the spoil materials must have desirable physical and chemical properties conducive for good growth of deeply-rooted trees. The surface four feet of mine soil material should be easily weatherable so that most rocks and boulders decompose to fine soil materials within a few years. The soil texture of the fine-earth fraction should be loamy to sandy, and the mine-soil should be low in total salts and moderately acid. Most important, the mine-soil must also be left uncompacted to a depth of four feet.
Research studies and many observations of reclaimed sites in Virginia, West Virginia, and Kentucky show that tree survival and long-term growth is excellent on oxidized, moderately-acid, sandstone-derived mine soils. In general, siltstone and shale that occur directly above or below coal seams should be avoided. These rock types usually have high levels of soluble salts, a high pH, and compact to greater densities w hen trafficked. Some of the blue-gray sandstones that occur further below the surface are acceptable for forest land. However, some of these spoils weather very slowly and should only be selected when brown sandstone is not available.
Reclaimed mine soils must be left loose and uncompacted to ensure successful establishment and long-term growth of trees. Prior to seeding ground covers, reclaimed sites are often cleared of large boulders, gullies are filled, and the surface is graded smooth and "tracked in" with bulldozers to create a seedbed for ground covers. This treatment may be conducive to hayland/pasture establishment, but it is very undesirable for tree establishment and long-term forest growth. Powell River Project research shows that mine soil compaction is the greatest single factor limiting the success of reforestation. When soils are excessively graded and tracked in, trees cannot be planted deeply enough. This results in poor survival rates and permanently reduces the mine soil quality. {mosimage} Compacted mine soils reduce water infiltration, reduce plant available water, increase sheet erosion, and restrict root growth.
When forest land is the post-mining land use, final grading should be limited to the extent needed to ensure the stability of slopes. On level and gently sloping areas, the spoil placement process should be planned so that once a pile is dumped in place, no more equipment passes over it except for a final, light grading. Mine soil compaction due to grading can be minimized by using small dozers with low ground pressures and grading only when mine soil materials are dry. Natural forest land in the Appalachians is usually rougher than pastureland. Reclaimed forestland with boulders and uneven surfaces will not adversely affect forest management activities.
Importance of Mine Soil Quality for Forests
The federal Surface Mine Reclamation and Control Act (PL 95-87) requires that mined land be restored to its original level of productivity. For example, in the Interior Coal Region of the Midwest, land capable of producing 100 bu/acre corn prior to mining must be able to produce 100 bu/acre after mining and reclamation. In the Appalachian coalfields, in a similar manner, mined forestland should be restored so that mine soils are capable of producing the same amount of wood after mining as before.
Studies on the Powell River Project show that mine soils covering a wide spectrum of quality are being constructed. This productivity spectrum is represented by sites on which trees are unable to survive, to sites on which trees are growing at rates faster than on natural, undisturbed soils.
Importance of Compatibility of Ground Covers with Trees
Unlike standard hayland and pasture forages that are lush during the first year and gradually decline without additional fertilizer, tree-compatible covers are designed to be relatively sparse during the first year and become increasingly lush by the second and third years. This allows tree seedlings to emerge above the ground cover and ensures their survival. Despite relatively-low recommended seeding rates, 90 percent ground cover can be achieved for partial bond reduction during the first year. Most of the first-year cover results from the annual grasses, while the legumes dominate after several years. Birdsfoot trefoil and Appalow lespedeza emerge slowly by producing only a few plants per square foot, and these plants are generally less than six inches tall after the first season. By the third season, however, they develop into a complete cover replacing the grass and filling in under emerging trees. These legumes persist beneath the trees, increasing organic matter and nitrogen levels for several years until trees eventually shade them out.
Another purpose of low ground cover seeding rates is to allow the invasion of native plant species such as yellow poplar, red maple, birch and other light-seeded trees. Dense ground covers prevent the establishment of native plants. An additional benefit of a tree-compatible cover is that some tree and shrub species can be established by direct seeding. When conventional ground covers are used, direct-seeded trees will not emerge and survive due to dense shading.
Tree Species Selection
A sufficient number of desirable trees must be established during reclamation in order to achieve multiple uses from a developing and mature forest. Two categories of tree species are recommended: 1) crop trees and 2) N-fixing nurse trees such as Paulownia (or shrubs). Crop trees are long-lived species that offer value to landowners as saleable forest products. Nurse trees are planted to assist the crop trees by enhancing the organic matter and nitrogen status of the soil and improving soil physical properties. Nurse trees will die or can be cut out after 15 to 20 years when crop trees need additional growing space. Nurse trees help achieve the minimum number of stems and ground cover required for bond release, and they provide food and cover for wildlife.
Nurse-tree Selection
The nurse tree and nurse shrub species recommended for reclamation planting are N-fixing plants that benefit crop trees and provide food and cover for wildlife. Nurse trees contribute to ground cover requirements and help stabilize the site.
Hydroseeding Trees
To reduce the expense of handplanting, nurse species can be hydroseeded with the ground cover. Most nurse species can be established by direct seeding provided an appropriate ground cover mix is used. Many direct-seeding efforts have failed in the past because the accompanying ground cover was too tall and dense for tree germinants to become established. A disadvantage of hydroseeding nurse trees is the loss of control with respect to their number and spacing. Too many nurse trees can reduce the amount of growing space for crop trees. Seed for many species requires cold storage treatment (stratification) to break seed dormancy before spring seeding. This pretreatment is necessary to mimic the effect cold winter temperatures would have on the seed. Different tree species have slightly different stratification requirements; however, all species recommended can be stratified by following these steps: soak in water for 24 hours, drain the water, mix the seed in a plastic bag with moist sand or peat, then store the bag in a refrigerator (40o F) for 30 to 60 days. Stratified tree seed should be sown in spring through early summer (March 15-June 30). Fall and winter sowing could result in mortality of the germinating seed due to cold temperatures. For late summer and fall applications, unstratified seed should be used. Unstratified seed will receive its cold treatment during the winter and then germinate in the spring{
Tree Seedling Handling and Planting Techniques
The successful establishment of trees is highly dependent on selecting good nursery stock, proper handling before planting, and proper planting techniques. Poor survival and poor early growth are usually the result of improper handling or planting. Seedlings should not be planted if the roots are dry . Air-dried roots have less growth potential than roots that have stayed moist. Stressed seedlings may survive if planted, but growth will be reduced. Seedlings should be graded prior to planting so that only healthy seedlings are used. Healthy pine seedlings should have a root collar diameter of 4/32 to 9/32 inches. Very small pine seedlings (under 4/32 inches diameter) and very large seedlings (over 10/32 inches in diameter) do not survive well. Very large seedlings are difficult to plant correctly. Root pruning of pine seedlings is not recommended; there is a tendency to chop off too much of the root system. With root pruning now being done in the nursery beds, none is needed at the planting site. Overall survival is better when no root pruning is done by tree planters.
Proper seedling storage and handling before planting is critical to ensure good survival and growth. Seedlings must not be allowed to get hot or dry. If planting is delayed, the bags of seedlings should be wetted and roots dipped in a moisture-retaining gel specifically designed to keep roots from drying. The seedlings should then be rebundled and placed in cold storage (32-36o F) for no more than four weeks. If cold storage is not possible, they should be stored in a cool damp basement for no more than a week. At temperatures over 40o F, mold develops and seedlings are killed. Without cold storage, it becomes more important to dampen the roots as soon as they are delivered.
Seedlings should be planted as soon as possible in late winter or early spring (February-April) after the ground has thawed. Early planting is preferred because the soil is usually wetter and more conducive to root growth. Root growth decreases during periods of rapid shoot elongation; therefore, it is important that the seedlings be planted early in the season so roots can become established before the weather turns warm enough for shoot growth to begin. During planting, crew leaders need to make certain that planters do not expose roots to the air by carrying seedlings in their hand. Seedlings should be carried in a planting bag and not removed until the planting hole is opened. Planting holes must be opened deeply enough so that the roots can be evenly spread in the hole. Seedlings should be planted about one inch deeper than grown in the nursery. Finally, the planting hole must be completely closed since any air spaces around the roots will cause those roots to die.
Planting crews should be given instructions on proper planting techniques prior to planting, and crew leaders should start quality checks immediately so that needed corrections can be made before much of the area is planted. This involves careful lifting of planted seedlings on random plots to check on seedling health, tightness, depth of planting, straightness, spacing, and density. Seedlings are carefully replaced after each one is inspected.
Establishing Trees in Dense Ground Cover
Sometimes it is necessary to establish trees in an existing cover of dense grasses or legumes such as K-31 tall fescue or Serecia lespedeza. In order to ensure survival and good growth, herbicides and slow-release fertilizer pellets are recommended. Chemical weed control (herbicides applied via backpack sprayer) helps maintain the seedlings free of overtopping competition. By controlling dense vegetation with non-chemical solutions, seedlings will receive adequate sunlight and more soil water to ensure their survival. In conjunction with weed control, slow-release fertilizer pellets can speed growth during the first few years to help the trees grow above surrounding grasses. Fertilizer pellets should be placed in the planting bar closing hole (never in the planting hole) about two inches from the roots during planting. Fertilizer pellets slowly decompose and release nutrients needed by the trees. By using pellets it is possible to selectively fertilize seedlings without fertilizing surrounding grasses. In many cases, dense ground covers of fescue and clover will decline after two or three years, after which time trees can be more easily established.
NOTE: The greater content of this document has been excerpted and adapted from:
Publication Number 460-123, January 1997 Dept. of Forestry, Virginia Tech
Authors: James A. Burger and John L. Torbert
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