Methods of assisted reproduction MUDr.Jitka Řezáčová ÚPMD, Praha 4, Podolí.
CHARACTERISTICS OF REPRODUCTION METHODS - ESF 14...2 Remember this … Now note the reproduction...
Transcript of CHARACTERISTICS OF REPRODUCTION METHODS - ESF 14...2 Remember this … Now note the reproduction...
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CHARACTERISTICS OF REPRODUCTION METHODSCHARACTERISTICS OF REPRODUCTION METHODS
Ralph D. NylandDepartment of Forest and Natural Resources Management
SUNY College of Environmental Scienceand Forestry
Syracuse, NY 13210
Nyland - 2010All rights reserved
Use of all or parts of this permission prohibitedwithout express consent of Ralph D. Nyland
Background reading:
Chapter 9, in Nyland, R.D. 2002. Silviculture: Concepts and Applications.Waveland Press. Long Grove, Il. 2ed.
Sources cited:
Bormann, D.B., and G.E. Lineks. 1979. Pattern and Process in a Forested Ecosystem. Springer-Verlag. NY.
Barlowe, R. 1958. Land Resource Economics. The Political Economy of Rural and Urban Land Resource Use. Prentice-Hall. Englewood Cliffs, NJ.
Kimmins, J.P. 1987. Forest Ecology. MacMillan Publ. NY.
Nyland, R.D., C.C. Larson, and H.L. Shirley. 1983. Forestry and Its Career Opportunities. McGraw-Hill Book Co., NY. 4ed.
Oliver, C.D. 1981. Forest development in North America following disturbances. For. Ecol. & Manage. 3:153-168.
Runkle, J.R. 1982. Patterns of disturbance in some old-grow5th mesic forests of eastern North America. Ecol.63(5):1522-1546.
Ryle, R.J., and W. Beyschlag. 2000. Gap dynamics. Pp. 251-279, in Leaf Development and Canopy Growth. B. Marshall and A.J. Roberts (eds.). Sheffield Acedem. Press. Sheffield, England
Smith, D.M. 1986. The Practice of Silviculture. John Wiley & Sons, Inc. NY. 8ed.
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Remember this …
Now notethe reproduction methods
After Nyland et al. 1983
Some silviculturists argue that successful regeneration is the most important factor leading to sustainable forestry ...
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But always through
a PROCESSPROCESS
Some silviculturists argue that successful regeneration is the most important factor in sustainable forestry ...
... certainly, if you do not regenerate cohorts of an appropriate density and composition
... you will have nothing to tend and eventuallyharvest
So we insure timely regeneration by a group of techniques
that we call the reproduction methodsthe reproduction methods
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… used to sustain the forest and its benefits
… of every kind
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REPRODUCTION METHOD:
- A processprocess for establishing and renewing a forestcommunity or age class
- Includes removing the old trees and establishing a newcohort to replace them
- Also includes any supplemental site preparation andimmediate post-seeding care necessary for success
Like clearcutting (even-aged ) …
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… or with selection system (uneven-aged)
… or two-aged silvicultureD.W. Smith
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It involves ...
- removing the mature trees and establishing anew cohort to replace them
- doing supplemental site preparation and post-establishment care
A PROCESS ... not an event
… using timber harvestingas a means to that end
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By manipulating the overstory (the reproduction method) we …
INCREASE ground surface temperature
CHANGE light quality and intensity at ground level
REDUCE withdrawals of soil moisture
STIMULATE decomposition of surface liter, releasing nutrients
… and the amount or degree depends uponthe type and intensity of cutting used
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After Smith 1986
Increasing degree of overstory removal
Full shade Full sunlight
Som
e en
viro
nmen
tal f
acto
rs
Consider this model Consider this model ……
So always ask ....
What conditions will best serve the purpose?
How to create those effects?
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Make the reproduction method into
A PROCESSPROCESS
… that may pass quickly in some cases
... like an event
... or it may take years or decades to complete
… done deliberately
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Some essential questions to consider in selecting an appropriate reproduction method:
What does the owner seek?What species will satisfy those goals?What species characteristics make one or more techniques
more useful than others ?What kind of stand does the owner want or need, given the
species sought or the uses intended?What biologic or economic limitations do I face in
producing these results?What constraints does the physical environment impose?What will it cost, and will the owner willingly pay to get it?
And timber sales give us a way to
implement the treatment
while also generating revenues …
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Ecologically appropriate …… economically advantageous
… and financially attractive
… and linked to a regulation scheme as well
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So how do we control / regulate these reproduction methods?
... in stands AND across a forest
THE REPRODUCTION METHODSAfter Nyland et al. 1983
We have four methods of control …
Treat equal areaeach time
Yields depend upon what standscut each time
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Like using an even-aged reproduction method …… to regenerate a fixed area of forest each year
May cut different number of acreseach time
Consistent yields determine theamount of area cut each time
Not all standshave the samevolume to remove ...
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Like regenerating as much area as needed …… recover the requisite volume from a forest annually
Not all standshave the samevolume to remove ...
May cut different number of acreseach time
ALSO, regulate intensityof cutting by a a basalarea or volume controlin the stand
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Like using a basal area control to regulate the intensity of a thinning …… and thinning sufficient stands to produce the required volume from a forest
Treat equal areaeach time
ALSO, regulate intensityof cutting by a a basalarea or volume controlin the stand
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Like using a basal area and structural control to regulate stand density and the diameter distribution with selection system …
… across a fixed area of forest
XXXXXX
The components of growth in a stand:
G = A + I – M
G = Net growthA = AccretionI = Ingrowth
M = Mortality
Also think about growth ...
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We want to optimize (A + I)
Accretion
-- by maintaining appropriate
stocking for full site utilization
-- by promoting rapid diameter
growth of residual trees
Ingrowth
-- by insuring good results from a
reproduction method
-- by taking measures to insure both
survival and development of each cohort
-- by controlling stand density to keep trees in
a vigorous condition
-- by timely regeneration of an age class to
minimize losses
We devote much thought to controlling
MORTALITY
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Consider how these affectstand growth and development ...
... starting with even-aged
Look at the
production function
After Barlowe 1958
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… with a clear pattern of development through time… within a single stand
Aging
Recall how even-aged stands develop through time …
… and in each stand across a forest
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All trees in a stand regenerated at the same time …… all developing to maturity together
… all coming of age at the same time
So …
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Var
iabl
e ou
tput
uni
ts
Variable input units
Marginal difference due toeach successive additional input
Average up to somespecific level of inputs
“Marginal” means added
And we can convert the total physical productcurve to measures of marginal and average outputs …
Peak levelof outputs
Put all together like this …
After Barlowe 1958
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Applied to even-aged stands ...
... substituting volume and age
Physiologicalmaturity
After Barlowe 1958
Vol
ume
Stand age
Mean annual increment-- m.a.i.
Periodic annual increment-- p.a.i.
Physiological maturity
… when p.a.I. = 0
And this biologic event …
Look at the average and marginal physical product curves ...
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After physiological maturity the mortality exceeds (Accretion + Ingrowth) …
... delineating the maximum logical rotation for commodity productionobjectives
Vol
ume
Stand age
Mean annual increment-- m.a.i.
Periodic annual increment-- p.a.i.
The peak ofm.a.i.
So what associated with the peak of m.a.i. …
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Vol
ume
Stand age
Mean annual increment-- m.a.i.
Periodic annual increment-- p.a.i.
Optimum rotationOptimum rotationfor fiber cropsfor fiber crops
… the culmination of m.a.i. delineates the optimal rotation
for FIBER PRODUCTIONFIBER PRODUCTION
Stand age
Vol
ume
Physiological maturity
Optimum rotationfor fiber crops
The zone of rational actionfor sawtimber production
The range of rotation lengths for commodity production …
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And how long we grow a stand betweenculmination of m.a.i. and physiologicalmaturity …
… depends on the financial objectives
… grown to financial maturityfinancial maturity
Giving us this model ...
… portraying even-aged stand development
After Barlowe 1958
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Depicted in ecologic terms ...
After Bormann and Likens 1979Physiological
maturity
Ecologic stages of even-aged stand development:
1. REORGANIZATION or stand initiation phase
2. AGGRADATION or stem exclusion phase
3. TRANSITION or understory re-initiation phase
4. STEADY-STATE or old-growth phase
Borman and Likens 1979; Oliver 1981
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After Kimmins 1987
Visualized like this …
(Uneven-aged)
Past
A transition from even- to uneven-aged occursdue to gap-phase replacement …
After Runkle 1982, Ryel and Beyschlag 2000
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Like this …
Old-growth orsteady state
Transition stage
Physiologicalmaturity
Changing the production function like this …
(Uneven-aged)
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But with commodity objectives we “NEVERNEVER”
let stands pass beyond the AGGRADATION PHASEAGGRADATION PHASE
SO ...
… how much of this applies touneven-aged communities
... if at all
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Uneven-aged stands have several age classes ...... each developing “of itself”
… but only one reaching maturity at a time
… multiple age classes… all growing together in the same stand
Recall the nature of uneven-aged stands …
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… with ages and sizes interspersed across a stand
… and in stands across a forest
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Parts regenerated at different times …… young, middle-aged, and old all present
… each comes of age at a different time
So …
… a separate production function for each cohort
Suggesting …
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... multiple age classes ...
... each at a differentstage of development
At any point in time ...
With uneven-aged silvicultural system we:
1. Remove the mature age class to regenerate a replacement cohort
2. Simultaneously tend the immature age classes to enhance their development
... dual functions using harvesting as a TOOL
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… periodic regeneration and tending to maintainmultiple age classes
Regulating stocking so it fluctuates between predetermined levels ...
... increasing with growth
... drawn down by harvesting
... within pre-set levels
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The production function for uneven-agedcommunities under selection system
To look like this through time ...
Always searching for answers …
After Nissen 2010