No Slide Title

Report
Crop Tree
Management
for
Forest Stand
Improvement
Tom Ward
Forester, ENTSC
Greensboro, NC
With slides from: Jeff
Stringer, U of KY, Jeff Ward,
U of CT and Arlen Perkey,
USFS, WV
What is a “Crop Tree” ?
– Any tree that has been identified as
desirable and worth retaining
– All trees are not equal, its OK to
discriminate, in favor of crop trees and
against competing trees
– Depending on producer objectives
(wildlife, timber, water quality,
aesthetics, etc.) different criteria apply
to the selection of crop trees
Crop Tree Management
Definitions
Crop Tree Release: targeting and managing a
limited number of trees for crown touching
release.
Crown Touching Release: providing free
growing space for crown expansion by
removing trees whose crowns are touching
crop tree crown.
LIGHT is the most limiting resource: for
forest grown trees, competing trees are those
whose crowns touch the crown of the Crop
Tree and reduce the amount of light received
by the Crop Tree
Sunlight
+ CO2
sugar
(sucrose)
wood (xylem)
sugar+sugar...
root reserves (starch)
Density Must Be Controlled
Growing Trees Fast
Means
 reduce density
 expand crown
 producing more leaves
 increasing diameter
growth and seed/fruit
production
Identify
problems &
opportunities
•Wildlife Habitat
•Forest Health
•Timber/Income
•Water Quality
•Visual Quality
Establish
Stand-Specific
EXAMPLES
of OBJECTIVES
Objectives &
• Increase mast
production.
Crop Tree
• Provide shelter
for squirrels.
Selection
• Accelerate
growth of highvalue timber spp.
Criteria
Crop Tree Selection Criteria
• A diversity of species
is beneficial for all
objectives
• Water quality: differing
rooting depths and
nutrient uptake rates
• Wildlife: more food and
habitat choices
• Visual Quality: variety is
more pleasing to the eye
• Timber: more options,
a “diversified portfolio”
• Forest Health &
Biodiversity: a more pest
resistant, resilient forest
Crop Tree Selection Criteria
Wildlife habitat
• Favor hard mast (oak, hickory, walnut) and
soft mast (cherry, persimmon, hackberry) spp
• Expected longevity > 20 years (based on size
& condition, esp. evidence of injury or decay)
• Den trees: existing or potential cavities,
longevity > 10 years, need not be released
Crop Tree Selection Criteria
Timber
• No forks or large branches in lower stem
• High value commercial spp. (walnut, oak,
cherry, sugar maple, tulip-poplar)
• Expected longevity > 20 years
Crop Tree Selection Criteria
Water quality
• Tolerant of flooding/suited to the site
• High growth/nutrient accumulation
potential (walnut, basswood, tulip-poplar,
sugar maple)
• Expected longevity > 20 years
Crop Tree Selection Criteria
Visual Quality
• Attractive flowers, foliage color, bark
• Unusual species and/or tree form
• Visible from house, road, or trail
• Expected longevity > 20 years
Divide crown into 4 sides
1 2
4 3
Apply a crown touching release
crown touching release
free
growing
space
1 2
4 3
1 side
release
4 side
release
2 side
release
3 side
release
Oak Response to Crown
Touching Release
Data from G. Miller, USFS-NE
CHO
Increase in dbh growth
inches
( 5 yrs)
NRO
0.4
0.5
0.35
0.4
0.3
0.3
0.25
0.2
0.2
0.15
0.1
0.1
0.05
0
0
1
2
3
4
1
Number of sides released
2
3
4
Yellow-Poplar Response to
Crown Touching Release
Increase in dbh growth
inches
( 5 yrs)
Data from G. Miller, USFS-NE
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
YP
1
2
3
4
Number of sides released
Increase free growing space.
crop
tree
Biggest problem forest owners have: keeping
focused on free growing space of crown.
Increase free growing space.
crop
tree
Timber Objective
crop
tree
•potential grade 1
or better
•crown form
indicates vigor
•Good Live Crown
Ratio, > 35%,
intermediate or
LCR
prefer 45-50%
< 35% suppressed trees
flat topped (oaks)
spindly topped
Crop tree management is appropriate…
When you can alter species
composition – early in stand
development.
When you need to save species from
competition.
When you can add substantial value
through growth.
Potential Benefits
Increase dbh growth
10-15 % increase in volume (value)
Improve stand quality
5-10 % increase in value
Improve species composition
15-60 % increase in value
How many trees per acre?
proper 3 and 4 side release
improper release
target fewer crop trees
1 0-Y ear Diameter Growth Rate (inches) on
Average Appalachian Sites per Species*
Species
Red Oak
Yellow Poplar
Black Cherry
Sugar Maple
White Oak
Scarlet Oak
Black Oak
Chestnut Oak
Average
* Adapted from Perkey 2001.
Unreleased
Released
%Increased
Growth Rate Growth Rate Growth Rate
2.0 10 rpi
3.4 6 rpi
70% *
2.5 8 rpi
3.8 5 rpi
52%
2.4
3.0
25%
1.4
2.0
50%
1.2 16 rpi
2.0 10 rpi
67% *
1.7
1.8
1.6
1.8
11 rpi
2.3
2.7
2.3
2.7
7 rpi
35%
50%
44%
50%
Crop Tree Inventory
• Use crop tree inventory
tally sheet
• Set up 1/5 ac. Plot, 53’
radius circle
• Flag plot boundary at
cardinal directions
• Using different colored
flagging, flag crop trees
and cut trees
• Record species and dbh,
using woodland stick
Crop
Tree
Plots
Crop Tree (CT) Inventory
• Establish 1-3 1/5 acre
plots per forest stand
depending on size and
uniformity of stand
• Flagging will help
producer or contractor
visualize treatment
• Ave. # of CTs & cut
trees/acre = workload
• Productive stands may
have 10-15 CTs per 1/5
ac. plot, or 50-75 CTs/ac,
approximately 25 feet
between CTs
• Stand quality & producer
objectives may call for as
little as 1-5 CTs/plot & 525 CTs/ac
Rules for Applying Crop Tree
Management
• use crown touching release on 3 or 4 sides –
focus dollars on technique that will achieve
growth/vigor increase and on trees that will produce
results
• Number of crop trees to release - rule of thumb: 50
to 70 crop trees in young well stocked stands, 10-35
in older, degraded, or under-stocked stands
• remove only trees interfering with horizontal
crown expansion
Rules for Applying Crop Tree
Approach
• crop tree criteria can be based on any landower
objectives: timber, wildlife, visual quality, water
quality, sensitive or t&e species, etc.
• using herbicides: root systems of competing trees
do not have to be killed unless it furthers long-term
objectives - if herbicides are used make sure crop
tree and competing tree are not the same species in
close proximity to one another
• when to apply: can be used as soon as tree crowns
begin to close in young stands and in older stands as
long as trees can be expected to respond to release
and are not nearing the end of their normal life span.
Rules for Applying Crop Tree
Approach
• Initial early walk through in regenerating stands
prior to entry for crop tree release can be
beneficial for removing harmful sprout clumps,
poorly formed stems, and exotics.
• crop tree release can be used to save species in
peril, to increase growth, and adjust species
composition.

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