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.