Classics
The following article has been selected because it is deemed very important to the arboricultural profession and deserves special recognition.  It has appeared in a previous Seminar and because of this it is not eligible for earning certification credits; there is no test at the end of this article.


                                                  Benefits from a Tree
                                                     (formerly titled Tree Stats)
                                                              By Len Phillips

The following is a compilation of many items that illustrate the statistics of a tree.  If you have others, please send them to me.

Tree leaves provide the following benefits and products:

• tea,
• juice,
• medicines such as aspirin,
• shampoo, 
• cellulose fiber,
• food for cattle,
• seasonal color,
• fragrance,
• mulberry leaves and silk worms produce silk thread,
• various shapes identify species,
• dust and pollutant filtration,
• cool air currents in hot weather,
• reduction to the formation of ozone,
• photosynthesis produces energy that is used by the tree and all other forms of life, 
• a large elm tree will make about 6 million leaves a year,
• 1000 cubic yards of leaves will eventually become about 200 yards of composted leaf mold.

Tree flowers provide the following:

• beauty,
• fragrance,
• herbal tinctures,
• pollen for butterflies and bees.

Tree fruits can produce:

• fruits and juices such as apples, pears, apricots, oranges, grapefruits, peaches, bananas, persimmons, plums, and apricots,
• edible nuts such as walnuts, pecans, hickories, almonds, pistachios, etc.
• seeds that can be used for coffee and other drinks,
• products from nuts such as cocoa and olive oil,
• fruits provide food for wildlife,
• berries such as quinine from the cinchona tree, wine from the serviceberry (Amelanchier) and gin from the juniper.

Tree bark offers many products and aesthetic values:

• spices such as cinnamon and nutmeg,
• rubber,
• taxol and other medicines,
• maple syrup,
• turpentine,
• thorns, furrows, exfoliation, textures, and colors,
• branches that are fun to climb.

Tree roots are useful for the obvious benefit to the tree and they also:

• enrich the soil,
• reduce erosion,
• fix nitrogen in the soil, 
• store carbon taken from the air,
• grow up to 15 feet (4.5 m.) a year,
• grow an average of 38" (100 cm) of root growth per 1" (2.5 cm) of trunk diameter,
• hold the soil to prevent landslides,
• intercept rainwater runoff by an average size tree of up to 12% of all the rainwater during a storm,
• total 15 to 20 cubic feet (4.2 – 5.5 cubic meters) of roots per square foot of root growth surface area,
• will absorb about 50 gallons (190 liters) of dissolved nutrients and convert it with sunlight to about 100 pounds (45 kg) of food and about 60 cubic feet (1.7 cubic meters) of oxygen on an average 40 feet (12 m) tall tree.

Tree wood will provide:

• fire wood,
• paper,
• food,
• wildlife food, shelter, and habitat,
• lumber products,
• a sturdy material, that pound for pound is stronger than steel.

Trees exchange oxygen and carbon dioxide at the following approximate rates:

• one average tree takes in 13 to 26 pounds (6 – 12kg) of carbon dioxide in a year and gives off enough oxygen to keep 4 people breathing in a year,
• one acre of forest absorbs about six tons of CO2 and puts out about four tons of oxygen a year. This is enough to support the annual needs of about 18 people.
• there are 422 trees for every one person in the world.
• a mature urban tree is 10 to 20 times more beneficial to the environment than a mature forest tree. 
• a single mature tree absorbs carbon dioxide (CO2) at a rate of up to 47.5 lbs (21.6 kg) per year and sequesters up to 1 ton of carbon by age 40.
• 2 average trees transpire about 3,000 gallons (12,000 liters) of water a day,
• one average tree can lift and transpire about one ton of water every summer day,
• this same average tree can lift water up its trunk at a rate of about 150 feet (46m) per hour,
• a 1,000 square feet (94 square meters) plot of trees absorbs about 1.2 million calories of heat energy that equates to air conditioning for 2 average houses,
• about 20 trees offset the pollution of driving a car for 60 miles (100K),
• a 30-inch (0.75 m) dbh tree provides about 70 times the ecological benefits of a 3-inch (7.5 cm) dbh tree,
• trees improve air quality and provide a fresh smell, 
• particulate levels on tree lined streets can be up to 60% lower than those streets without trees. The lower particulate level saves lives every year.

Trees can live for an average of:

• 100 – 200 years in a forest,
• 25 – 50 years in the suburbs,
• 7 – 10 years in an urban planting site,
• the oldest living tree in England is the Forthingall yew (Taxus baccata) in Scotland, aged about 3,000 years old,
• the root system of a Norway Spruce (Picea abies) in Sweden has been sending up new shoots for 9,550 years,
• the oldest individual tree in the world is a bristlecone pine (Pinus longaeva) aged 5,062 years old.  It is located in California's White Mountains.

A tree’s location beside a house will provide the following benefits:

• reduce air conditioning needs by 15% to 50%,
• reduce winter heating needs by 4% – 22%,
• lower the urban heat island by 3° – 5°F (1° – 2.6°C),
• cool the rooms of a house by 15 - 20°F (8 - 11°C),
• cool bare ground beneath a tree by 25 - 35°F (14 - 20°C),
• increase the value of living space by about US$4 per square foot,
• increase a home’s value by 6% – 10% and land value by about 7%,
• reduce the light intensity in winter by 20% – 75%, depending on the species,
• reduce fog 6 – 10 times more effectively than grass,
• absorb 30 - 50 pounds (14 - 22 kg) of airborne particulates per year,
• street trees absorb about 4 times more airborne particulates than on streets without trees,

City trees grow best with:

• no - mulch, string trimmers, mowers, or plants within 6 – 8 inches (20 cm.) of the trunk,
• mulch applied 2 – 3 inches (5-7 cm) thick and 1 – 2 inches (2.5–5 cm.) of new mulch each year,
• understory companion plants and other trees,
• The tallest tree in the world is a coast redwood (Sequoia sempervirens), named Hyperion.  It was last measured at 379.3 ft (115.61 m) and is growing in moist soil and damp air, among many other coast redwoods in northern California.

Trees in groups affect wind because:

• trees in a row forming a windbreak or shelter break will slow wind speed by as much as 50%,
• windbreaks will increase snow accumulation just beyond the windbreak,
• windbreaks will cause heavy air particles to drop out of the air flow,
• trees in groups will hide and diffuse noise by 6 – 8 decibels for every 100 feet (30 m) of buffer,

Trees provide the following aesthetic values:

• color, form, texture, and pattern,
• softer architecture and road appearance,
• vistas and focal points,
• define spaces,
• screen views,
• direct pedestrians and traffic,
• reduce glare and lights,
• provide shade, fragrance, and a quiet setting,
• provide psithurism, the sound of wind blowing through a forest,
• emphasize the seasons.

Trees provide the following psychological values:

• cleaner air,
• faster healing,
• improved morale,
• sentimental trees,
• living memorials,
• human well-being,
• increased productivity,
• a sense of community, pride, and responsibility.

Negative affects of trees:

• susceptible to storm damage,
• potential source for grounding lightning strikes,
• potential obstacle for vehicle damage,
• roots clog broken pipes carrying a water product, lift cracked sidewalks, and damage wet foundations,
• require pruning for utility service, viewing signage, and safety clearance,
• pollen from wind pollinated male flowers may cause an allergic reaction in people,
• leaves, fruit, and flowers may require clean up,
• suckers and dead branches may require constant removal,
• maintenance costs for pruning, watering, pest control, etc.
• for every 4 trees that are cut down in the United States, one tree is planted.

 
Watering newly installed trees require:

• daily watering for the first one to two weeks, applying approximately 1.5 gallons per caliper inch (1.5 liters per caliper centimeter) per watering;
• after two weeks, water the trees every two to three days for the next two or three months, with approximately 1.5 gallons per caliper inch;
• after 2-3 months, weekly watering is necessary for the remainder of the season or until the tree is established;
• after the first year, if watering is necessary, it should be 1 gallon of water per inch of caliper (1 liter per caliper cm).

The above amount of watering equates to 1 inch of rainfall per week.

Trees need:

• about 5 square feet (0.45 s. meters) of soil area for each square inch (6.5 s.cm.) of trunk at breast height,
• suitable soil at least 30 inches (0.75 m.) deep,
• about 1,000 cubic feet (30 c. meters) of soil to thrive in a parking lot,
• a minimum of  2 cubic feet (0.06 cm) of soil for every square foot (0.1 sm) of the future crown projection or 4 square feet (0.38 sm) of surface area for every inch (2.5 cm) of trunk diameter the tree is expected to attain,
• fungi in the soil to promote tree root growth,
• the guy wires or stakes usually removed after one season, 
• the wire basket usually removed at planting time,
• an ideal soil has 50% pore space, divided between air-filled and water-filled pores, 45% is composed of mineral materials, and 5% organic material,
• one inch of rainfall or irrigation every week during the growing season to maintain optimum growth.

Sources

• Daley, Richard, ‘Tree-mendous Facts”, Greenstreets, City of Chicago, 1998.
• Harris, Richard W., “Arboriculture – Care of Trees, Shrubs, and Vines in the Landscape”, Prentice-Hall, Inc. Englewood Cliffs, NJ.
• Perry, Thomas, “Typical Tree Roots and How to Examine Them”, City Trees, January, February, 1994.
• Phillips, Leonard, “The Value of a Tree”, City Trees, July/August 1992.