Shelterwood Method
SHELTERWOOD AND SEED-TREE METHODS
Ralph D. Nyland Department of Forest and Natural Resources Management SUNY College of Environmental Science and Forestry
Syracuse, NY 13210
With animations by Nyland – 2010 R.L. Nissen, Jr.
All rights reserved Use of all or parts of this permission prohibited without express consent of Ralph D. Nyland
Background reading:
Chapter 14, in Nyland, R.D. 2002. Silviculture: Concepts and Applications. Waveland Press. Long Grove, IL. 2ed.
Sources cited:
Leak, W.B., D.S. Solomon, and S.M. Filip. 1969. A silvicultural guide for northern hardwoods the Northeast. US For. Serv. Res. Pap. NE-143.
Noble, D.L., and F. Ronco. 1978. Seedfall and establishment of Engelmann spruce and subalpine fir in clearcut openings in Colorado. US For, Serv. Res. Pap. RM-200.
Schlich, W. 1910. Schlich’s Manual of Forestry. Vol. II Silviculture. Bradbury, Agnew, and Co. LD. London
Smith, D.M. 1986. The Practice of Silviculture. John Wiley & Sons, Inc. NY. 8ed.
1 REMEMBER, clearcutting allocates total ecologic space to the new age class ...
- suddenly changes the environmental conditions - removes the seed trees - configuration may affect the environment and seed dispersion - begins a new period of long-term development - reduces some disease and insect threats - transforms the stand structure - abruptly alters the visual qualities
Increasing degree of overstory removal
Opening the ground to full sunlight …
EXTREME Some environmental factors environmental Some
Full shade Full sunlight
After Smith 1986
2 And removing all seed trees from the stand …
… relying on seed in the duff, on logging slash, and blown in from adjacent stands
Noble and Ronco 1978
In many forest community types ...
… absence of abundant and well-developed advance regeneration
... makes clearcutting RISKY
So how to get the needed advance regeneration ...
3 … even better developed than this
In some forest community types ...
... thinning LATE in a rotation will trigger an understory response
... establishing advance regeneration and promoting its development
4 … after crown thinning, abundant sugar maple advance regeneration developed beneath this 100-year-old stand
… allowing a smooth transition to complete overstory removal
5 If not ...
... use the shelterwood method
Increasing degree of overstory removal Some environmental factors environmental Some
Full shade Full sunlight
After Smith 1986 Leaving well-distributed seed trees of good phenotypes …
… to temper the environment … … and maintain a seed source
6 Like this ...
Seed cutting
The response
... so seed cutting leaves a protective cover ... creates a favorable environment for regeneration ... leaves a well-distributed source of seed
An example with eastern white pine ...
... after the seed cutting
7 Regeneration developed beneath the overwood …
... ready for overstory removal
8 … the shelterwood method
… when an even-aged stand matures
Mature by some standard …
9 … after seed cutting … leaving the best at uniform spacing
… to promote a new cohort beneath the old trees
10 … and then remove the overwood, releasing the new trees
Three possible treatments with the shelterwood method …
Preparatory cut ... if needed
... in stands where trees lack sufficient vigor for good levels of seed production
... simply to enhance the seed-production potential of selected overstory trees
Seed or seeding cut ... always
... to initiate a new age class
Removal cut ... always
... to uncover the new cohort
11 … normally seed cutting starts the process
… at least in managed stands
Shelterwood seed cutting
- leaves various amounts of overhead shelter - retains the shelter as oing as needed - the shelter mitigates changes in the environment - the shelter serves as a seed source - the seed trees get bigger while they remain - the seed trees add vertical structure while in place
… but you must remove or reduce the shelter before it stunts the new cohort
12 Ready for a removal cutting …
… part of a process to replace the mature stand
An appropriate stocking for the overwood depends on factors like:
- seed dispersal patterns and distances - light levels needed to support regeneration - minimum canopy cover for adequate protection … to temper conditions at the ground ... to inhibit interfering plants ... to protect the seed trees - rates that seed tree crowns expand and close - volume added to seed trees before the removal cutting - minimum volume for an operational removal cutting
13 Probably cut to this level or less (≤ 50% relative density)
Leak et al. 1969
We can use an appropriate relative density guide to plan the seed cutting intensity ... … e.g., down to 50% or less (even to 35%)
But think about the constraints of later harvesting for the removal cut ...
... what minimum volume must you have available at that time
… noting that
The larger and more valuable the seed trees …
... the fewer needed for a commercial removal
14 And the minimum volume depends upon the harvesting system and the operating conditions ...
... here using cable yarding
But note this as well ...
Some species regenerate well in full sunlight ...
... but seed distribution may pose a problem … due to inadequate dispersion … due to an insufficient seed bank
Then seed-tree method may serve the need ....
15 Increasing degree of overstory removal
Opening the ground to full sunlight … Some environmental factors environmental Some
Full shade Full sunlight
After Smith 1986 … with an environment like clearcutting
Mature by some standard …
16 … after seed cutting … leaving the best at uniform and wide spacing … to serve as a seed source
… to promote a new cohort beneath the old trees
17 … and then remove the overwood, releasing the new trees
Seed-tree method …
... the seed cutting
18 Nissen 2008
… like this to insure a black cherry seed supply
Nyland 2008
Characteristics of seed-tree method:
- leave a few residuals for a seed supply - residuals too few to act as a shelter - spacing depends on seeding characteristics of the species - remove the seed trees when regeneration adequate in amount and distribution - seed trees change for good or bad
The environment at and below the ground surface changes
JUST LIKE WITH CLEARCUTTING
19 ... with openness like clearcutting
After Smith 1986
An example of seed-tree method …
…in eastern white pine
... the seed cutting
20 ... the result
… a new cohort
21 … deliberately replacing the mature one
... a new even-aged community
22 Back to shelterwood method ...
... in western conifers
Back to shelterwood method ...
... in western conifers
... before treatment
23 ... the seed cutting
… reducing stocking to create an ecologic void in the system
24 …increasing light levels near the ground
... even done in long and narrow blocks to facilitate yarding
25 … yarded up the corridors using this machine
... the tongs
26 ... roads for setup of the yarder
… engineered to accommodate logging trucks
27 … reducing overstory cover within the inter- corridor strips
... a yarding corridor
28 ...... the result
... or something like this
29 But ...
… you can retain some low-density and widely spaced reserve trees
.... for LOOOOONG periods
Making the scheme in to the
RESERVE SHELTERWOOD METHOD
... keeping some old ... starting some new
30 So what is ...
… reserve shelterwood method
So what is ... … reserve shelterwood method
Cut to low density overwood
Leave to older age class indefinitely
Leading to a 2-aged stand
Cut again at half- rotation age
` ... and repeated through time
31 Mature by some standard …
… after seed cutting … leaving the best at uniform and extra wide spacing
32 … to promote a new cohort beneath the old trees
… but both age classes left to grow many years into the futue
33 ... creating a two-aged stand
Or use a variation of it ...
... reducing the old age class in two cuts
... with the same end result
34 Either approach gives the same end result ...
We can also approach shelterwood method in alternate ways ....
... GROUP SHELTERWOOD METHOD
... STRIP SHELTERWOOD METHOD
35 Group shelterwood method …
Schlich 1910
… cut scattered circular patches to initiate the regeneration process
36 … to promote regeneration in the opening … AND beneath the adjacent area
Promoting advance regeneration
Schlich 1910 … then expand the openings to uncover advance regeneration beneath the surrounding tall trees … repeating the process in response to progressive understory development
37 … periodically expanding the openings to release the recently-developed advance regeneration
... or use strip shelterwood method
38 ... to promote natural regeneration
... cutting additional strips as advance regeneration develops adjacent to the first-cut strips
39 … with eventual overstory removal across the entire stand
Lets look at an example where shelterwood method seemed like the only alternative ...
40 … in northern hardwoods lacking desirable advance regeneration
... and having a dense beech understory
41 Uncut Stand With Interfering Understory
Animation by Roger L. Nissen, Jr.
Spraying the Interfering Understory
42 ... as the site preparation
… understory mist-blowing using an appropriate herbicide
43 … blowing the mist up for about 15-20 feet
… the effect
44 … even taking out any advance seedlings of desirable species
Uncut Stand With Mistblown Understory
45 Uncut Stand After Site Preparation
... deer density control also needed in some cases
46 ... too many deer and the beech keep good regeneration from developing
Uncut Stand After Site Preparation and Deer Density Control
47 Selected Trees for Shelterwood Seed Cutting
After Shelterwood Seed Cutting
48 ... the seed cutting
… reduced stocking of excellent phenotypes at uniform spacing
49 ... and perhaps some single-stem cleanup work
… completing the site preparation
50 ... keeping trees of good phenotypes
Selecting residuals for seed trees:
- good phenotype of the sought-after species - sturdy and windfirm - able to survive exposure - must flower and produce viable seed - prolific seeder -the VERY BEST you have - your hope for the future
51 After the seed cutting ...
... note this emptiness
... but soon new seedlings appear
52 … though still small after one growing season
... normally dense Rubus develops by 3 years
53 ... tree seedlings continue to develop among and under the Rubus
… with sugar maple developing more slowly than the less shade-tolerant species
54 ... by 6-7 years trees of low to mid shade tolerance emerge above the Rubus
... reaching a free-to- grow status
55 … and then the shade-intolerant Rubus declines in vigor and begins to die out
... now ready for removal cutting
56 ... by 10 years
… a new closed tree canopy has formed
57 ... but do the overwood removal before these get more than 1 inch in diameter
Prior to Shelterwood Removal Cutting
58 Selected Trees for a Shelterwood Removal Cut
… releasing the new cohort from any shading by the seed trees
59 Overwood removed Overwood still in place
… removal cutting completed
60 After Shelterwood Removal Cut (Seedling Stage)
… the new even-aged tree community at ~ 15 years
61 Followed by Continued Stand Development (Early Pole Stage)
With this result 29 years later …
62 ... success
... but consider the visual qualities
63 ... distinct edges draw attention
After removal cutting …
... to circumvent this image
64 Check this effect …
… and extend it all along the edge
… softened edges
After removal cutting …
65 The usual …
… with feathered edges
A reproduction method …
… softening the edges
66 Certainly more than one option possible …
After Nissen 2010 … but how to decide
67