Tree PreservationDesigning, constructing, and maintaining to protect established trees

Tree BiologyAn overview of tree roots, tissue layers, and reactions to damage

RootsMost of a tree’s roots are in the top 12-18” of soil, with the greatest concentration in the top 6”.

Tree roots can extend 2-3 times the width of the canopy.

Trunk LayersBark protects trees from damage from the outside.

Phloem moves sugars the leaves make throughout the tree.

Vascular cambium generates the cells that become the phloem and xylem.

Xylem carries water and nutrients from the roots to the rest of the tree.

Xylem

Active xylem

CODIT: Compartmentalization of Decay in TreesTrees don’t heal, they seal.

When a tree is wounded, it must seal off the wound so that the inevitable decay doesn’t reach the whole tree.

On a clean wound at the right location, a layer of callus tissue covers the location to help seal it from the outside.

Tree Damage6 ways a tree’s roots and shoots can be harmed

Shoot Injury: broken branchesJagged break leaves more disease entry points

Can split or tear down other limbs or the trunk

Leftover stub is vulnerable to decay

Shoot Injury: gouged trunkDamage to phloem disrupts sugar transport

Damage to vascular cambium restricts tree’s ability to grow outward

Cannot be fully fixed, especially if it spans more than 1/3 of the tree’s circumference

Root Injury: cuttingCreates entry points for pests and diseases

Cuts tree off from water and nutrients

Huge amounts of short-term stress because the tree needs extra water to close off the wounds, but it has lost much of its access to water

Root Injury: changing gradeRaising the grade suffocates the roots and reduces access to water

Lowering the grade removes critical surface feeder roots

Changing the grade by as little as 2” can kill a tree

Root Injury: compactionA good soil is 50% pore space

Compacted soil makes it harder for roots to grow, limits air, and limits water

Can be caused by driving over soil (especially when wet) or stockpiling heavy materials

Root Injury: chemical damageMany chemicals common on jobs sites can get into the soil and damage roots

Diluting spills immediately is often enough to mitigate damage

Beware of leaky fuel cans and equipment

Concrete can easily raise pH to dangerously high levels

Questions?