web page by Tristan Moore, 2018
Site selection is a very important factor when it comes to planting a tree. Trees are a very dynamic and resilient organism and can grow virtually anywhere. However, if a tree is planted in good soil, with enough room, and the right environmental characteristics, then it will sustain a very healthy life.
Site Selection or design
Drainage
Soil drainage is how well a given soil can hold its moisture for tree growth (1). Soils water holding capacity is related to the available volume and size of pore space in the soil structure (9). With a loose soil that has great pore space, muck like sandy or loamy soils, it will result in greater water infiltration and allows water to move through the soul more readily (9). However, if the soil is compacted and has little pore space, much like clay soils, this will result in less water infiltration and root growth throughout the soil (9).
Many trees need a well-drained, preferably loamy, soil or landscape to grow into a healthy tree (10). Oxygen and water are important components in a well-drained soil. Oxygen in the pore space allows roots to move through the soil and absorb the available water. However, soil compaction reduces pore space for oxygen, root growth, and water infiltration (9). Too much water can also be a bad soil characteristic by suffocating the root systems.
A loose, well-drained soil allows tree roots to move through open pore spaces and collect the available oxygen and water within the spaces (9). The leading cause of drainage issues is the compaction of soils (9). Compaction of soils can be caused by construction, foot traffic, cars, etc. To reduce compaction, try tilling, aerating, or mixing in some organic materials or sands to help regulate drainage issues within the soil structure (9). Urban landscapes tend to have more runoff and less water infiltration in the soil. This is due to the frequency of impervious structures like buildings and streets. Soil can be a very critical component in tree growth.
Soils
Soil nutrients are also important for proper root development and tree growth (1). A soils ability to hold water and have enough open pore space for roots to grow is ideal. Many soil organisms, such as: earthworms, burrowing mammals, and various forms of fungi and bacteria, work together to for soil aggregates (soil clumps) to increase soil nutrients and pore spaces (9).
Different soil types can be beneficial or detrimental to the type of tree species that one selects to plant. So, planting the appropriate tree for the type of site that is available is very beneficial to the tree (10); refer to figure 1. in the slideshow above. There are many different soil types and characteristics of the structure of soils.
Soil types:
Sandy – A very coarse soil texture (much like table salt) that has great pore space. Does not retain a lot of moisture. Moisture tends to run down quickly (high drainage).
Silty – Less coarse and finer than sandy soil (intermediate size between sand and clay soil particles). Retains water longer but has low drainage, so water hangs around. Easily compacted.
Clay – a very fine soil texture (much like powdered sugar) and retains most of the infiltrating water. Very easily compacted and could loose soil infiltration.
Loam – a mixture of clay, sand, and silt. Best water holding capacity and ideal for tree growth.
Soil depth and space should also be accounted for due to trees needing enough room for their roots to grow (2). It is best to make sure that the tree also has room to grow. As trees grow, they expand in trunk diameter and height, so plan accordingly. Refer to figure 2 and 3 for good and bad site characteristics.
Climate
Climate is the prevailing weather pattern over a period of time. Different parts of the world experience different climate factors, such as: temperatures, weather patterns, and the location of the earth (10). Make sure trees are being planted can withstand the climate type of the region. For example, tropical tree types will not fair well in colder, drier environments as well as temperate trees can (10).
Take into account the hardiness zones associated within each site location. Hardiness zones are zones where certain types of plant life are capable of growing and withstanding the minimum and maximum temperature associated with the site (10). Elevation is another factor that plays a role in tree growth. Due to low temperature, low moisture, and low atmospheric pressure, the elevation can stunt a trees growth and its overall development (10). Generally, more sun and elevated land is preferred for most trees (2). However, shade tolerant trees do not require much sunlight to thrive and usually hide under larger trees or next to infrastructures.
Species Selection
Selecting a certain species is important given certain site locations and characteristics. For example, a bald cypress tree can grow best in moist, swampy environments. They can tolerate drier soils or climates, but this can restrict their growth. It would not grow well if planted in an arid climate, so a different tree species should be selected for this site (1). Trees can be very resilient organisms, but not all trees can grow wherever they wish. Certain tree species have evolved to withstand certain factors, so plan accordingly.
Soil drainage is how well a given soil can hold its moisture for tree growth (1). Soils water holding capacity is related to the available volume and size of pore space in the soil structure (9). With a loose soil that has great pore space, muck like sandy or loamy soils, it will result in greater water infiltration and allows water to move through the soul more readily (9). However, if the soil is compacted and has little pore space, much like clay soils, this will result in less water infiltration and root growth throughout the soil (9).
Many trees need a well-drained, preferably loamy, soil or landscape to grow into a healthy tree (10). Oxygen and water are important components in a well-drained soil. Oxygen in the pore space allows roots to move through the soil and absorb the available water. However, soil compaction reduces pore space for oxygen, root growth, and water infiltration (9). Too much water can also be a bad soil characteristic by suffocating the root systems.
A loose, well-drained soil allows tree roots to move through open pore spaces and collect the available oxygen and water within the spaces (9). The leading cause of drainage issues is the compaction of soils (9). Compaction of soils can be caused by construction, foot traffic, cars, etc. To reduce compaction, try tilling, aerating, or mixing in some organic materials or sands to help regulate drainage issues within the soil structure (9). Urban landscapes tend to have more runoff and less water infiltration in the soil. This is due to the frequency of impervious structures like buildings and streets. Soil can be a very critical component in tree growth.
Soils
Soil nutrients are also important for proper root development and tree growth (1). A soils ability to hold water and have enough open pore space for roots to grow is ideal. Many soil organisms, such as: earthworms, burrowing mammals, and various forms of fungi and bacteria, work together to for soil aggregates (soil clumps) to increase soil nutrients and pore spaces (9).
Different soil types can be beneficial or detrimental to the type of tree species that one selects to plant. So, planting the appropriate tree for the type of site that is available is very beneficial to the tree (10); refer to figure 1. in the slideshow above. There are many different soil types and characteristics of the structure of soils.
Soil types:
Sandy – A very coarse soil texture (much like table salt) that has great pore space. Does not retain a lot of moisture. Moisture tends to run down quickly (high drainage).
Silty – Less coarse and finer than sandy soil (intermediate size between sand and clay soil particles). Retains water longer but has low drainage, so water hangs around. Easily compacted.
Clay – a very fine soil texture (much like powdered sugar) and retains most of the infiltrating water. Very easily compacted and could loose soil infiltration.
Loam – a mixture of clay, sand, and silt. Best water holding capacity and ideal for tree growth.
Soil depth and space should also be accounted for due to trees needing enough room for their roots to grow (2). It is best to make sure that the tree also has room to grow. As trees grow, they expand in trunk diameter and height, so plan accordingly. Refer to figure 2 and 3 for good and bad site characteristics.
Climate
Climate is the prevailing weather pattern over a period of time. Different parts of the world experience different climate factors, such as: temperatures, weather patterns, and the location of the earth (10). Make sure trees are being planted can withstand the climate type of the region. For example, tropical tree types will not fair well in colder, drier environments as well as temperate trees can (10).
Take into account the hardiness zones associated within each site location. Hardiness zones are zones where certain types of plant life are capable of growing and withstanding the minimum and maximum temperature associated with the site (10). Elevation is another factor that plays a role in tree growth. Due to low temperature, low moisture, and low atmospheric pressure, the elevation can stunt a trees growth and its overall development (10). Generally, more sun and elevated land is preferred for most trees (2). However, shade tolerant trees do not require much sunlight to thrive and usually hide under larger trees or next to infrastructures.
Species Selection
Selecting a certain species is important given certain site locations and characteristics. For example, a bald cypress tree can grow best in moist, swampy environments. They can tolerate drier soils or climates, but this can restrict their growth. It would not grow well if planted in an arid climate, so a different tree species should be selected for this site (1). Trees can be very resilient organisms, but not all trees can grow wherever they wish. Certain tree species have evolved to withstand certain factors, so plan accordingly.
Modifications (sites are rarely perfect)Soils
If the selected site is too dry, compacted, or too wet, it will yield poor trees (10). Soil quality can be improved by mixing in certain soil particles and nutrients. Taking a soil test can show the homeowner what the soil contains and what it is lacking. Types of fertilizer can be applied to help fit the soil and trees needs. Aeration of soils may also be beneficial (1). Aeration is the process of creating more pore space in the soil to increase oxygen and water holding capacity; refer to figure 4 (1). The adding of certain minerals into the soil can help adjust the pH of the soil if it is too high or too low. The pH of the soil is a measurement of the acidity or alkalinity of the soil. A pH of 7 is considered neutral between the two. Anything higher than 7 is considered to be alkaline, and anything lower than 7 is considered to be acidic (9). Most trees can tolerate a pH of 6-6.5 (9). A pH of 6 is 10 times more acidic than a pH of 7, and a pH of 5 is 100 times more acidic than a pH of 7; vise versa (9). Some tree species have evolved to tolerate more alkaline or acidic soils as well (1). If the pH is too high, less nutrients will be available to the tree. To lower the soil pH, add organic materials, such as: pine needles, compost, manure, or sulfur (9). If pH is too low, it could need to be raised with the use of limestone or magnesium added to the soil (9). All of these methods may take awhile to take effect and they will not last forever. Drainage If drainage is poor in a site, mixing of the soil or adding certain minerals or organic matter may help improve drainage (2). The adding of organic materials or a coarser soil, like sands, could help increase the drainage of the soil (2). This will not always improve drainage; if the soil is too compacted, the soil will need to be aerated or tilled (9). If there is too much drainage, the came can be applied to the site by mixing of the soil or adding certain minerals or organic matter to the site. Trees Planting the appropriate tree for its corresponding site location is crucial to the trees overall lifespan (1). If there are trees living in a difficult site location, then they might need to be maintained more often or completely removed; refer to figure 5. Always make sure there is enough space for the tree to grow and make sure its free of any obstacles. The space should be able to withstand the tree at its mature height as trees will grow larger over time (10). Every tree species has different mature characteristics, so be away of tree size, form, fruiting structures, and the height associated with the species. If a certain tree is wanting to be planted, but the soil is not suitable for the given species, then soil modification or a more suitable tree species is required. Tree DiversitySelecting an Appropriate Species
There are thousands of different tree species in the world, so make sure to plant the right tree for the specific site. Refer to figure 6 to look at a diverse urban forest located at Oz Park. Most trees have adapted to tolerate different climate characteristics (9). Not just selecting trees for certain site conditions, but also being aware of the tree characteristics, such as: if it has a small/tall stature, regular/irregular form, thorns/fruit, or leaves/needles (1). Selection of tree varieties may have undesirable characteristics (deciduous, cleaning, maintenance, fruiting structures) so make sure the planter knows what to expect in the trees life. Homeowner and Municipal Considerations to Species Selection Consideration of tree species is important when planting in urban areas (1). Make sure the tree is free to grow without any obstacles that might impede the trees growth (10). Trees with a large mature size should be planted a farther distance away from homes and facilities; where as smaller trees are of less concern and can be planted closer (1). Appropriate planting locations and tree species selection are expected for public safety (1). Large growing trees should be planted away from roads, away from any obstacles (power lines, signs, intersections), placement next to sidewalks and parks where more people tend to be (10). Small stature trees can be planted closer to infrastructures, under power lines, and closer to streets (10). However, trees are very dynamic and could pose a threat to public safety. Maintenance of trees are of concern to public safety and must be monitored from time to time. MaintenanceSchedule of Maintenance (Yearly & Seasonally) All trees in an urban environment is going to need to be pruned and maintained every so often; refer to figure 7. Some trees need to be pruned a specific time of year to prevent pests or pathogens of spreading (seasonally) (2). Other trees can be pruned any time of the year, but it is usually best to prune during the growing season; around late spring, summer, early fall. Safety concerns also result in tree maintenance. Broken branches, decay, and dying trees are often needed to be pruned or even removed. Areas of pedestrian use, much like streets and sidewalks, require special attention and need maintenance to meet certain safety standards (1). Trees are Long Lived If a big tree is placed in a narrow soil pit between a road and a sidewalk, then the tree will eventually grow and disrupt the sidewalk or street and will eventually need to be removed for safety (1). Predicting how the tree will grow in each site and planning ahead will help in maintaining control of the tree from the beginning (2). Consider the site as well as the tree, make sure the site will sustain the tree for a long period of time. Infrastructure, Sidewalks, & Utilities Trees near sidewalks, building, roads, and parks require more attention than other trees, due to the trees being more of a public safety concern (1). Almost constant management and pruning of these trees are required. Trees planted under power lines or above ground lines should be prevented (1). If a tree is wanted to be planted under power lines, select a smaller stature tree or one that will not obstruct the power lines. Avoid planting above anything regarding sewage lines, power lines, or pipes. It will prevent any future issues or safety concerns (10). References1. Macie, E., Workman, S., & Campbell, H. (2016). Urban Tree Planting (Part 1): Site Selection. eXtension. Retrieved from: http://articles.extension.org/pages/67466/urban-tree-planting-part-1:-site-selection
2. Crassweller, R. (2017). Orchard Establishment – Site Selection and Preparation. PennState Extension. Retrieved from: https://extension.psu.edu/orchard-establishment-site-selection-and-preparation 3. Agriscape Soils. (2009). Image. Retrieved from: http://www.agriscapesoils.com/ 4. Moore, T. (2018) Image. 5. TheLawnInstitute. (2018). Image. Retrieved from: http://www.thelawninstitute.org/pages/education/for-homeowners/advanced-lawn-care/aeration/ 6. Heneghan, L. (2013). Oz Park urban forest. Image. Retrieved from: http://10thingswrongwithenvironmentalthought.blogspot.com/2013/05/tree-architecture-in-lincoln-park.html 7. Sagdejev, I. (2008) Tree pruning in Durham, North Carolina. Image. Retrieved from: https://en.wikipedia.org/wiki/Urban_forestry#/media/File:2008-04-21_Tree_trimming_on_Gregson_St_1.jpg 8. Stephen. (2015) How to Create Amazing Garden Soil from Clay, Silt or Sand. Image. Retrieved from: http://www.livingoffgridguide.com/gardening/how-to-create-amazing-garden-soil/ 9. Lilly, S. (2010). Arborists’ Certification Study Guide: Chapter 3 Soil Science. International Society of Arboriculture. 3:36-49 10. Cappiella, K., Schueler, T., Tomlinson, J., & Wright, T. (2006). Urban Watershed Forestry Manual Part 3: Urban Tree Planting Guide. United States Department of Agriculture. Retrieved from: https://www.fs.usda.gov/naspf/sites/default/files/urban_watershed_forestry_manual_part3.pdf 11. Jim. (2011). Stressed tree. Image. Retrieved from: http://www.differentlight.org/stress-solutions/ Web page created by: Tristan Moore |
