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Redwoods at Big State University
Background and History 2
Limits of the Assignment 4
Purpose and Use of the Report 4
Testing and Analysis 5
Appendix A. 9
Appendix B. 10
Appendix C. 11
Appendix D. 12
Appendix E. 13
Appendix F. 14
I was contacted by Big State University to examine three trees that had been preserved during an extensive construction project. The project consisted of re-grading existing lawn areas, excavating for buried utilities, and re-paving sidewalks and parking areas. The University would like a report on what I think can be done to ensure the long term success of these trees.
Big State University requested a site visit. I observed two trees that appear weak, and stressed; their foliage is pale green, sparse, and the tips of the needles are brown. The third tree, however, I found the foliage to be normal, dark green, and full.
The construction was done during the summer when the trees were actively growing. The destruction of the roots and the limited area the existing roots now occupy has reduced the trees ability to absorb water and nutrients. This condition was further exacerbated by the infrequent irrigation supplied to the trees during construction. There are no nutrient deficiencies or signs or symptoms of insects or disease. In addition, the structural integrity of the trees has been compromised by the root removal.
Below I explain the background and history of the situation, observations and test results from my site visit, and my recommendations for the trees.
Background and History
In Early November Buck O'Neil, (project manager) for Big State University contacted me and requested a site visit and written report on 3 Coast Redwoods. (Sequoia sempervirens)
Two of the trees recently defoliated following a construction project.
Mr. O'Neill informed me he was to be the primary contact, but I would contract the tree consultation job thru ABC Design (landscape architects)
The project team consists of
Big State University (project manager) Buck O’Neill
Big State University (site superintendent) Josh Gibson
Ready Construction (general contractor) Ray Dandridge
ABC Design (landscape architect) Becky Leonard
Cool Papa & Bell (civil engineer) James Bell
On November 3, I visited the site and met with the project team. Buck O'Neil, and Becky Leonard related the history of the site to me. From now on, I will refer to the trees as #83, #84, and #85.
The condition of the trees prior to construction was:
Tree Number and location
Diameter of tree
Health and description
Good health with full but pale green foliage
Excellent health with full dense crown
The trees are located on the north side of the library, at the south edge of the construction zone. The impact to the trees include
Demolishing, re-grading, and replacing a sidewalk between the trees and library.
Demolishing, re- grading, and reconfiguring a large sidewalk and access on the east of the trees.
Installing a catch basin near tree #83.
Reducing the extent of lawn on the north, due to installation of a new utility vault and sidewalk.
Replacing existing irrigation system in the lawn.
A Tree Protection Zone was recommended by ABC Design. The fence was installed at the drip line prior to construction. The tree protection zone was breached once during construction, when an irrigation trench was dug 12 feet from the tree trunks. The tree protection zone also includes ivy and other small shrubs. The trees were to be irrigated weekly with soaker hoses.
My assignment was to
Perform a ground based examination and determine why #83 and #84 defoliated.
Recommend treatments to mitigate the damage.
Summarize my findings and recommendations in a written report.
Limits of the Assignment
My evaluation was limited to photographs of the site during construction. I performed a limited ground based exam.
Purpose and Use of the Report
The purpose of this report is to identify any biotic or abiotic damage to the trees, as well as, provide treatment options. In addition, I will identify any structural problems or hazards that might be associated with this type of damage.
The report is to be used by the project team to implement treatment options. The treatment options may not ensure the survival of the trees.
On November 3, I visited the site and learned the tree protection zone was for the most part, kept intact, during construction. No construction material or debris was stored in the fenced in area. No pesticides were applied near the trees and no wash out of materials occurred near the trees.
The fence was removed to dig an irrigation trench. There were many large roots removed during this procedure. (See Photo Appendix A)
There was major root disturbance on the north side of the trees from excavating for irrigation, the utility vault, and lowering the existing grade to accommodate additional parking. The lawn area would be reduced in size and lowered as much as 3 feet.
On the south side of the trees a new sidewalk was installed. There was major root disturbance there as well. (See photo Appendix B)
The trees were irrigated, but irregularly. The soil in the open irrigation trench was dry, and the plants around the site were very dusty.
I reviewed the landscape plans and found the hardscape and new landscape areas to be consistent with the plans. (See Drawing Appendix C)
Testing and Analysis
I collected composite soil samples from beneath the canopies of #83, and #85. The sampling depth was surface to 15"The results show that chemical analyses are typical for the region and both soils are suitable for a wide range of plants. (See results Appendix D)
I also collected twig and foliage samples from tree #83 and #85. (See Appendix E)
Sample #1 tree #83 the foliage was chlorotic with some necrosis at the tips.
Sample #2 tree#85 the foliage was dark green, dense and normal in appearance.
These samples were sent to an independent lab for testing. There were no signs of insects or plant pathogens on the samples submitted. (See Appendix F)
Coast Redwoods are native from southern Oregon to California. They grow in fog belts, on deep moist soil, often near rivers and streams. When placed in a landscape settings that may include shallower soil profiles as well as limited irrigation the tree can be predisposed to environmental stresses.
Construction around trees can affect the trees health in several ways:
Decrease its ability to absorb water and nutrient by removing the fine absorbing roots and beneficial soil mycorrhizae.
Physical removal of soil and roots can compromise the structural integrity of the tree.
Altering the physical and chemical properties of the soil environment. Which my limit water infiltration, percolation, and absorption.
Construction and root pruning were done in the summer months when the trees were actively growing, and needing the most water. Removing roots and soil, limited the trees ability to absorb water, and nutrients. Insufficient irrigation further compounded this situation.
By removing soil, you can physically damage or destroy the large structural roots. (See Appendix A&B) Removing the large structural roots can make the trees less stable, and more likely to wind-throw during severe storms. Removal of roots on one side is a concern but roots were cut on two sides. (North and south) The trees should be inspected yearly, and or after strong weather events for leans, and cracks. This work should be performed by a licensed arborist with TRAQ certification.
Physically cutting the larger roots can allow wood rot pathogens to enter the tree through the wounds. The trunks, and root crowns should be monitored for signs or symptoms of decay; for example, but not limited to, fungal fruiting bodies, carpenter ants, and nesting birds, for the next ten years.
The soil texture class is silty clay loam and susceptible to compaction resulting in a compacted soil. This physical alteration of the soil particles affects the air spaces in the soil as well the rate water can enter and move through the soil profile. In addition, mycorrhizae and mycorrhizal associations may have been affected which further compromises the trees ability to absorb water and nutrients.
It is my opinion the construction damaged the tree roots, removed necessary soil for adequate moisture and nutrition absorption. In addition, not enough irrigation water was supplied during, and after construction, resulting in the decline of trees number #83 and #84. Tree #85 was in the best health prior to construction. It had the least amount of excavation near it; resulting in less damage to its root system, and was better able to withstand the construction damage.
The ivy and small shrubs in the tree protection zone should be removed so the remaining trees do not have to compete for available water and nutrients.
In addition, a grid drip system be installed on top of the soil in the tree protection zone. The drip irrigation will allow enough water be placed efficiently over the root zone, as well as encourage a fine fibrous root system. Keeping the trees hydrated allows them to absorb water and nutrients essential for photosynthesis and growth.
Mulch the tree protection zone with wood chips. The mulch should be applied 6" deep and do not place directly against the trunks. This will help conserve water, limit weed growth, regulate soil temperatures, and add nutrients, and organic matter as the mulch breaks down. The additional nutrients and organic matter will help restore any mycorrhizal associations that were lost during construction. Over time the organic matter can help to improve the soil structure.
Since the soil samples didn't show any nutrient deficiency I am not recommending any fertilizer be applied. In addition, since there was major root loss to the trees I am not recommending any invasive treatments to the root zone. (air spading or radial trenching)
Next summer, any dead limbs that appear in the crown should be removed. Don’t try to guess what branches will die and do not do preemptive pruning.
The trees should be inspected yearly, and or after strong weather events for leans, and cracks; in addition, for signs and symptoms of decay in the roots, root collar and trunk. This work should be performed by a licensed arborist with TRAQ certification.
Air Spading-----device that directs a jet of highly compressed air to excavate soil.
Compacted Soil ----- Compression of the soil, often as a result of vehicle or heavy equipment traffic, that breaks down soil aggregates and reduces soil volume and total pore space.
Dripline----- Imaginary line defined by branch spread.
Mycorrhizae----- Symbiotic relationship between certain fungi and plant roots.
Pesticides-----A substance or mixture of substances intended for preventing, repelling, or mitigating any pest, or intended for use as a plant growth regulator, defoliant, or desiccant.
Radial Trenching-----A technique for aerating the soil by removing existing soil and replacing with amended soil. Trenches are made in a spoke like pattern radially from the trunk.
Soil Profile-----Vertical section through the soil and all of the soil horizons.
Soil Structure----- Arrangement of soil particles into larger aggregates, the larger units have different physical properties from the individual particles.
Soil Texture Class-----Classification system using the soil triangle determines the percentage of sand silt and clay particles in a soil
TRAQ-----A certification by the International Society of Arboriculture using a systematic process to identify, analyze and evaluate tree risk.
Tree Protection Zone----- A defined area where certain activities are prohibited or restricted, to minimize or prevent damage or potential damage to trees during construction.
September. Looking west. Irrigation trench 12’ from tree trunk; 18” wide & 18: deep. Trench was 18” wide and 18” deep. Note pile of roots near the trunk of tree #83 (red arrow). The new utility vault and turn-around are located in the upper right.
November. Close-up of twigs #83(left) and #85(right)
Lilly, Sharon “Arborists’ Certification Study Guide” International Society of Arboriculture. Champagne, IL 2010
Dunster, Julian A. E. Thomas Smiley, Nelda Matheny, and Sharon Lilly, 2013“Tree Risk Assessment Manual”. Champagne, Illinois: International Society of Arboriculture
Shigo, Alex L. “Modern Arboriculture” A Systems Approach To The Care Of Trees And Their Associates ,1991 Durham, New Hampshire
Beard James B., 1973 “Turfgrass Science and Culture” Prentice –Hall, Englewood, New Jersey
January 15, 2016
Mr. Buck O’Neill
Big State University
Subject. Coast Redwoods (Sequoia sempervirens) Big State University
Dear. Mr. O’Neill,
Enclosed is my report that you requested, on the three Coast Redwoods (Sequoia sempervirens) conserved during the construction project at Big State University. The report summarizes my observations and opinions on the cause of damage, and any future damage that may arise from the injuries. I have several recommendations to help mitigate the damage to these trees. If you have any further questions or concerns, please don’t hesitate to contact me.
Garth Welch Landscape Horticulturist, LLC
January 16, 2016 Redwoods AT Big State University
16tures, and add nutrients, and organic matter as the mulch breaks down. The additional nutrients and organic matter will help restore any mycorrhizal associations that were lost during construction. Over time the organic matter can help to improve the soil structure.
Tree Protection Zone----- A defined area where certain activities are prohibited or restricted, to minimize or prevent damage or po