relative density and its use in thinning
TRANSCRIPT
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RELATIVE DENSITYRELATIVE DENSITYAND ITS USE IN THINNINGAND ITS USE IN THINNING
Ralph D. NylandDepartment of Forest and Natural Resources Management
SUNY College of Environmental Scienceand Forestry
Syracuse, NY 13210
Nyland - 2010
All rights reservedUse of all or parts of this permission prohibited
without express consent of Ralph D. Nyland
Background reading:
Chapter 17, in Nyland, R.D. 2002. Silviculture: Concepts and Applications.Waveland Press. Long Grove, IL. 2ed.
Sources cited:
Dale, M.E. 1968. Growth response from thinning young even-aged white oak stands. US For. Serv. Res. Rpt. NE-112
Daniel, T.W. J.A. Helms, and F.S. Baker. 1979. Principles of Silviculture. McGraw—Hill Book. Co. NY. 2ed.
Mar:Moller, C. 1954. The influence of thinning on volume increment. 1. Results of investigations. Pp. 5-32, in Thinning Problems and Practices in Denmark. SUNY Coll. For. at Syracuse, World For. Ser. Bull. No. 1, Tech. Publ. No. 76.
Marquis. D.A. 1986. Thinning Allegheny hardwood pole and small sawtimber stands. Pp. 68-84, in Guidelines for Managing Immature Appalachian Hardwood Stands. H.C. Smith and M. Eyes (Ed.). W. Va. Univ./, Morgantown. Soc. Am. For. Publ. 86-02.
Marquis, D.A., R.L. Ernst, and S.L. Stout. 1984. Prescribing silvicultural treatments in hardwood sands of the Alleghanies.US For. Serv. Gen. Tech. Rpt. NE-96.
Nyland,. R.D. 2002. Silviculture: Concepts and Applications. McGraw-Hill Book Co. NY. 2ed.
Roach, B.A. and S.F. Gingrich. 1968. Even-aged silviculture for upland central hardwoods. US Dept. Agric., Agric Handbk. No.355.
Roach, B.A. 1977. A stocking guide for Allegheny hardwoods and its use in controlling intermediate cuttings. US For. Serv. Res.Rpt. NE-373.
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Reukema, D.L., and D. Bruce. 1977. Effects of thinning on yield of Douglas-fir: Concepts and some estimates obtained by simulation. US For. Serv. Gen. Tech. Rpt. PNW-58.
Steneker, G.A., and J.M. Jarvis. 1966. Thinning in trembling aspen stands in Manitoba and Saskatchewan. Can. Dept. For. Publ. No. 1140.
Stout, S.L. and R.D. Nyland. 1986. Role of species composition in relative density measurement in Allegheny hardwoods. Can. J. For. Res. 16:574-579.
Stout, S.L. 1990. Progress report for relative stand density in northern hardwoods throughout the Northeast. USFor. Serv. Northeast. For. Expt. Stn. 4110-FS-NE-1152-119.
Stout, S.L. and R.D. Nyland. 1986. Role of species composition in relative density measurement in Allegheny hardwoods. Can. J. For. Res. 16:574-579.
WHY THIN …- Improve sawtimber production
... get larger trees in less time
... increase board-foot yields
... enhance stand-wide quality and value
... influence species composition
- Promote stand development... enhance habitat for plants and animals... alter visual qualities... facilitate other non-market uses... move toward “old-growth” conditions
- Influence hydrologic characteristics (water quality and yields)
- Promote tree vigor and stand health (growth and resiliency)
- Stimulate seed production (like preparatory cutting)
- Promote litter decomposition (release nutrients)
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To influence stand development in favor of a landowner’s objectives ...
How to measure success ...
- volume and value realized- tree growth rates and sizes- tree vigor and health- stand structural features- diameter and height distributions
- number and sizes of understory plants- amount of coarse woody debris- homogeneity of structural features (orderliness or
“neatness”)- thickness and composition of soil organic layers
- light levels near the ground- ease of movement through a stand- degree and distance of visibility (fewer stems and brighter
understory)
Socialinterests
Timbervalues
Ecologicfactors
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… depending on the objectives for management
AMaximumstocking
Expected development of unthinned oak stands
... the curve shows the maximum basal areafor stands with a specified number/acre
Remember this critical concept …Developed primarily for timber objectives …
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Mar:Möller 1954 … with full net production at about 60% relative density
ALSO, we need some minimum stocking for full site utilization …
A
B For FULL site utilization
Suggesting a minimum stocking AFTER thinning ...
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MortalityHIGH>80%
But with mortality increasing with REL DEN >80% ...
Giving us a zone for rational action ...
Nyland 2002
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B-level relative density gives you ...
- full net cubic-foot production
... per acre per year
- enhanced individual tree growth
... commensurate with full net cubic volumeproduction per acre per year
Keep stands in the GREEN zone
To realize full net production ...
… with the associated ecologicconditions that follow
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… altering stand conditions to serve the objectives
Roach and Gingrich 1968
So we can use the stocking guideas an aid in planning thinning ...
FOR OAK STANDS
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But Roach tried it with Allegheny hardwoods ...
... with poor results
After Roach 1977
Until he accounted for species composition ...
... separating
CAPS (bc, wa, and tulip-poplar)
OTHERS (all other species)
… demonstrating that species composition made a difference
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With a separate line for each species group ...
... each A line to representa different proportionof basal area in CAPs
Roach 1977
And then adding a family of B lines ...
... one for each species group(set at 60% of each A line)
B
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So Stout asked ...
… WHAT IF I add additional species groups
But experience suggested that this guide needed enhancement ...
... particularly to account for stands with lots of red maple
She approached it using the tree-area ratio (TAR) …
TREE-AREA RATIO (TAR)
- a mathematical device for apportioning
ground area using stem diameters
- where the area of a stand is expressed as
a function of ΣD & ΣD2
- Σ (TAR) of all trees present = 1.00
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RELATIVE DENSITY = Σ (TAR)
- expressed in CENTACRES
- the TAR’S for different species can be compared to
determine how to best account for species composition
in assessing competition within forest stands
- TAR differed between CAPS & two other species groups
See Stout and Nyland 1986
Stand relative density = ∑ (Tree relative density)
Tree relative density = ƒ (Tree diameter and species)
Individual tree
relativ
e density
... in ce
ntacres
Stout and Nyland 1986
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So three groups for Allegheny hardwoods ...
CAPS – bc, wa, & tulip-poplar
HM-BE – hm, be, stm, oaks except ro
OTHER – all other species
… we use these for other northern hardwoods as well
... the hm-be group
This defines the contribution of individual trees to stand relative density (by species) …
... e.g., for 16-inch treeStout and Nyland 1986
... the CAPS
... the red maple group
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Stout, USFS, 1990
The number, shape, and position of the lines depends uponthe species mix and regional conditions ...
But Stout found that even this improvement needed refinement …
So we use this set for hardwood stands in NYS …
Stout, USFS, 1990
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SO HOW TO USE IT ...
... in practical applications
Tim Davis 2001
SO COMPLICATED ...
Marquis et al. 1984
RD factorsincluded
Try this field tally sheet ...
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An example ...
... a typical field tally
Here we calculate relative density rather than getting it from a chart...
See instruction sheetfor guidance in makingthese calculations …
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And based on the findings, we canprepare a marking guide to controlthe thinning …
NOTE: Remove up to 35% RD …
… butbut don’t reduce the standbelow 60%
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From the distribution of cut chart …
And how much to cut from each size class ….
… taking a trial distributionof cut from this chart
… in this case forDM = 14 inches
Marquis et al. 1984
For a crown thinning …
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From the distribution of cut chart …
32.16 * 0.63 = 20.26
And how much to cut from each size class ….
… to see how a cut of this kind wouldmatch actual conditions in the stand
BUT check the UGS …
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The proposed cutwould NOT reduce the ST UGS adequately
… so we make an adjustment tofit the real situation
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100% of potentialgross growth
% of maximum possible basal area
% o
f max
imum
cur
rent
gro
ss g
row
th
After Mar:Möller 1954
... at about 60% relative density we getfull gross cubic-foot volume growth
Insuring full site utilization …… and a full level of production
Mortality
And control of mortality as well ...
The B line on stocking charts set at the best estimate of a stand density where
net P.A.I. peaksfor stands at different ages
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Helms, Daniel, and Baker 1979
60%
30-35%
... for a stand
... for a tree
Examine some real responses from thinning trials ...
Stand
Tree
Marquis 1986
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Steneker and Jarvis 1966
Dale 1968
Stand-level cubic-foot volume production like this ...
In older managed stands bd ft production seems topeak at a somewhat higherresidual relative density ...
… but this still needs betterdefinition
Marquis 1986
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Marquis 1986
... mostly the smallertrees of poor crownpositions die
80%
With stocking below 80% ...
Marquis 1986
60%
… FEW epicormics instands with at least60% relative density
With stocking above 60% ...
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Giving us a model for management ...
... keep stands in the green zoneNyland 2002
Keep stands in the GREEN zone
Primarily ...
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Reukema and Bruce 1977
The same basic idea ...
... for Douglas-fir
And note this for northern hardwoods ...
ResidualBASAL AREAincreased witheach thinning ...
For the stages of developmentportrayed, the optimum residualbasal area should be increasedfrom about 62 to 80 ft2/ac …
… if periodically thinned to 60% RD
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To give you this ...
Additional volume ralizedwith regular thinning
Excess trees removedduring thinning
Post-thinningBA/ac higher each time
Full site utilization ...