Restoring for Old Growth Characteristics

Aging a Forest to Create Old Growth Characteristics

Southern Ontario

Most southern Ontario old growth was removed by logging, fire and settlement between mid-1700’s and early 1900’s.

New forests cover much of s. Ontario.

New forest less diverse than old mixed hardwood.

Now provides habitat for fewer species.

Forest will become old-growth on its own

100 y for deciduous trees, longer for conifer

Trees will die and fall

Create habitat

Return energy and nutrients to soil

OM will build

Will retain moisture

Will create a moist old growth environment

For faster results


Cut holes in canopy

Rebuild rich layer of decaying OM

Protect wildlife trees

Old-growth characteristics

Complex, multi-layered structure

Trees of all ages and sizes

Several canopy layers


Trees like pines that poke through canopy

Management tools

Cutting holes

Periodically, make clearings in ½ to 2% of parcel

> 50 m from edge and from other clearings

Small gaps (6-10 m) (remove 2-3 mature trees)

Encourages growth of shade-tolerant spp.

Larger gaps (10-50 m)

Encourage mid-tolerant spp. like oaks, white ash, white pine

Large openings (>50 m)

Favor intolerant spp. like poplar, birch, black cherry

Only makes sense in large parcels

To regenerate shade tolerant spp., choose sites where saplings of shade-tolerant spp. are present.

If you have unplanned treefall, create a gap by cutting several neighbor trees.

Protect uncommon trees from harvest

Such as long-lived conifers.

Pits and mounds

In natural forests

Provide range of moisture conditions

Expose mineral soil needed by some seeds

Decaying root masses create rich habitat

To restore

Dig depressions and mound up the spoil

Import rootwads

Let declining trees fall naturally

Decaying wood

In natural forests

Provides habitat

Absorbs moisture

Adds OM and nutrients to soil

Provides germination sites for some spp.

To restore

Leave 10 fallen logs per ha

>2 m long, >60 cm diam.

Cut sequentially to get age classes

Allow brush and leaves to decompose

Ground cover

Protect litter and herbaceous plants from livestock

When logging, localize activity on few skid trails

Log in winter and skid on snow trails

Wildlife trees (mast trees, cavity trees)

Leave 6 living cavity trees per ha

> 25 cm dbh

At least one > 50 cm dbh

Choose some of softer wood

Choose some that live longer, some that die early


Leave as many as possible

At least 5 per ha, some > 50 cm dbh

Create snags by girdling

Dead conifers stand longer

Aim for diversity of snag ages

Also leave

Mast trees

Nut, fruit trees

7 per ha

Large trees

> 50 cm dbh

3 per ha

Super-canopy trees

Leave one cluster of three per 4 ha (pines, hemlocks, spruce)

Protect as seed source

Good habitat


Pacific Northwest

U.S. Forest Service recommends variable-density thinning for conifer plantations

Thin to different densities in ¼ to 1 acre patches

Leave ¼ to ½ acre unthinned areas

Create small gaps < ¼ acres

Small gaps allow in light but do not increase windthrow

In young plantations, small gaps will encourage the growth of herbs, shrubs and understory trees, and, large open-grown trees

In un-thinned or lightly-thinned areas, shade tolerant trees like hemlocks will grow.

Natural disturbances will continue to occur, adding to landscape diversity


New England

Passive management

Allowing natural disturbances to create old-growth features


Standing dead

Pits and mounds

Downed logs

No harvest

Will take over a century in New England

Active management

Legacy tree protection

Never harvested; perhaps 25-50% of canopy trees

Reduced harvest of other trees continues

Produces large trees, canopy, snags, big logs



USFS Southern Region completed a report in 1997:

“Guidance for Conserving and Restoring Old-Growth Forest Communities in National Forests in the Southern Region”

Old growth characterized by:

Large trees

Variation in tree size and spacing

Accumulations of dead fallen and standing trees

Decadence (broken or deformed tops and root decay)

Multiple canopy layers

Canopy gaps and understory patchiness

Three levels of old growth recognition

Existing old growth

Criteria: age, disturbance, basal area, tree size

Future old growth

Allocations of wilderness or backcountry which will be managed to become old growth

Possible old growth

Stands meeting one or more minimum old growth criteria



Southwestern forests are characterized as “frequent fire” systems.

Large trees and a modest amount of large dead material (standing or down) are one characteristic.

High density of trees is not a characteristic of uneven-aged old growth stands adapted to frequent, low-intensity fires.

Stands are usually composed of shade-intolerant pines that need the creation of openings every decade or so to produce uneven-age stands.

One approach is to achieve a target basal area (10-18 m2/ha)

Most large, old trees are retained

Some trees retained in all diameter classes

Ponderosa pine dominates

ome Pseudotsuga, Abies


Some dead; historical fires kept it at low levels


Natural and prescribed fire

Intermediate treatments


Improvement cutting (removal of Doug fir)

Sanitation cutting (removal of diseased trees)

Regeneration treatments

Cutting to allow new age classes

Staged treatments

Carry out restoration over long periods of time