Hallo,
I thank everybody who took the pain to answer my quite
hugh pile of question concerning forest simulation models
and their applicability.
Here is a short summary:
******* Original question *******
I am currently involved in the task of developing a model of mixed
species, mixed ages, distance dependent, process based tree growth
model mainly for use for planted forests under not to dry and not to
cold conditions. Basis will be a modified single species, single age,
distance independent, process based stand growth model (TREEDYN,
develped by Prof. Bossel and co-workers, University of Kassel,
Germany).
We want to get answers to questions like: is yield of mixed forests
(e.g. beech and spruce) higher as in mono cultures under different
climatic and soil conditions? what kind of cutting strategy is
working best? and especially: with climate change what will be the
results to forests concerning yield and sustainability and the like
(EC sponsored project LTEEF: long term effects of CO2 and climate
change to european forests)? in short: we want a generic model only
with parameters that have biological meaning and are easily derived
for different plant species and site and meteorological conditions.
As this will be the greater part of my Ph.D. thesis (in physics) I am
wondering why there seems to be no model of this generic type to be
on the "market" (so I was told. If you know of such a model please
feel free to correct me.). There has to be a reason for this and I
don't want to bear a dead child:
- is this task to formidable, are there to many processes involved on
to many levels to get any meaningful simulation results?
- are there no data to validate such a mixed species model?
- do researchers feel that processes like photosynthesis, allocation
and soil processes are to poorly understood to make a model based on
assumptions about these processes scientiffically justifiable?
- are there other types of models (e.g. gap models or whole stand
models) that can answer questions of impact of environmental
conditions more easily than a process based single tree model?
- is there any experience with this kind of model that suggest that
there is some fundamental error to believe an endeveour of the kind I
want to undertake to be not fruitfull?
I would be greatful for any first hand hints and suggestions
concerning my task.
Michael Sonntag
*************************************************************
- Nearly everybody seem to think that gap models of every
couleur are the right type of model.
So favores Don Catanzaro the JABOWA model of Botkin, Chri-
stian Hoffmann FORECAST by J.P.Kimmins, Guy Larocque
and Lou Gross (also ECOPHYS and TREGRO) consider
FORET by H.H.Shugart and Jochen Schenk is thinking
of FORSKA2 by I.C.Prentince et al. to be the winner.
Michael A. Lefsky considers HYBRID by A. Friend.
- Some think our/my task as impossible (Jochen Schenk) or
at least very ambitious (Margaret Penner).
Others are very interested like Louis Schmittroth, Frits Mohren
, Pekka Kaitaniemi and especially Guy Larocque.
David J. Stewart thinks that mine/our kind of model is the
'crucial next step to understanding the processes that are
only partially observable'. But 'process-based models are
still in their infancy' as Guy Laroque remarks.
hannd@ccmail.orst.edu (name?) observed that '"process"
models has not improved (and has often reduced) the ability
to accurately and precisely predict stand development' in
comparison to 'empirical' models.
- Problems of scale are adressed by Jochen Schenk: he states
a 'general rule of ecological models' that says 'you should always
operate the model at one level lower than the level for which
reponses are required'. So if one is interested in stand dy-
namics the logical scale down is the tree level and problems
should be stated on this level and not as I/we want to do it
on a process-level (photosynthesis, respiration ...).
Also Tom Gross thinks that 'modelling on first principles is nearly
impossible just because of the computational requirements'.
Laurin Wheeler states the importance of making 'something
complex simple', reduce and generalize and thinking of the
time scale as important.
David J. Stewart says that as 'every tree is unique' one should
be very cautious to model single trees. On a stand level
differences might disappear.
- Data requirements to validate this kind of model are rather
high. David J. Stewart thinks that there is not enough data
available to test and validate. Jochen Schenk states that
there is 'surprisingly little information on the autecology of
tree species'.
- A lot of literature is recommended. Here a summary:
+ "Growth Models for Tree and Stand Simulation," edited by
Joran Fries. 1974. Department of Forest Yield Research,
Royal College of Forestry, Stockholm, Sweden. Research Note
Nr 30. 379p.
+ "Forest Modeling and Inventory: Selected Papers form the
1973 and 1974 Meetings of Midwest Mensurationists," Edited
by Alan R. Ek, James W. Balsiger and Lawrence C. Promnitz.
1975. Department of Forestry, School of Natural Resources,
University of Wisconsin, Madison, Wisconsin. 122p.
+ "Growth Models for Long Term Forecasting of Timber Yields,"
Edited by Joran Fries, Harold E. Burkhart and Timothy A.
Max. 1978. School of Forestry and Wildlife Resources,
Virginia Polytechnic Institute and State University,
Blacksburg, Virginia. Publication FWS-1-78. 249p.
+ "Forecasting Forest Stand Dynamics," Edited by Kenneth M.
Brown and F. Richard Clarke. 1980. School of Forestry,
Lakehead University, Thunder Bay, Ontario, Canada. 261p.
+ "Proceedings-Growth and Yield and Other Mensurational
Tricks: A Regional Techincal Conference,"Edited by Dwane D.
Van Hooser and Nicholas Van Pelt. 1985. USDA Forest
Service, Intermountain Research Station, Ogden, Utah.
General Technical Report INT-193. 98p.
+ "Forest Growth Modeling and Prediction ,"Edited Alan R. Ek,
Stephen R. Shifley and Thomas E. Burk. 1985. USDA Forest
Service, North Central Forest Experiment Station, St. Paul,
Minnesota. General Technical Report NC-12. 1149p.
+ "Forest Growth Models and Their Uses," Edited by Chhun-Huor
Ung. 1993. Natural Resources Canada, Canadian Forest
Service Modeling Working Group, Laurentian Forestry Centre,
Sainte-Foy, Quebec, Canada. 298p.
+ Alig, R.J., P.J. Parks, R.M. Farrar, and J.M. Vasievich.
1984. Regional timber yield and cost information for the
South: Modeling techniques. USDA Forest Service, Rocky
Mountain Forest and Range Experiment Station, Fort Collins,
Colorado. General Technical Report RM-112. 28p.
+ Hann, D.W. and K. Ritters. 1982. A key to the literature
on forest growth and yield in the Pacific Northwest:
1910-1981. Oregon State University, Forest Research Lab.,
Corvallis, Oregon. Research Bulletin 39. 77p.
+ McQuillan, A.G. and H.R. Zuuring. 1983. Predicting growth
and yield for managed timber stands in Montana. University
of Montana, Montana Forest and Conservation Experiment
Station, Missoula, Montana. 25p.
+ The PhD work of G.M.J. Mohren, 1987, "Simulation of
Forest Growth, Applied to Douglas fir Stands in the
Netherlands." This model is classified as a
"single-tree/distance-independent model". Dr. Mohren was
located at the Research Institute for Forestry and Landscape
Planning "De Dorschkamp," Bosrandweg 20, P.O. Box 23, 6700
AA Wageningen, THE NETHERLANDS
+ The ongoing work of Dr. Kelsey Milner, School of
Forestry, University of Montana, Missoula, MT 59812. Dr.
Milner is currently working on the Ground Surface Vegetation
(GVS) Model for mixed species stands. GVS is a climate
driven carbon and water balance model in which
photosynthesis, transpiration, respiration, and carbon
allocation are modelled for all vegetation on a site. GVS
is also classified as a "single-tree/distance-independent
+ Dixon, R.K.; Meldahl, R.S.; Ruark, G.A. and Warren, W.G.:
Process modelling of forest growth responses to
environmental stress. Timber Press Inc., Portland,
Oregon 1990
+ DeAngelis and Gross 1992: Individual-based models and
approaches in ecology. Chapman and Hall
+ Sorrensen-Cothern et al. 1993: A model of competition
incorporating plasticity through modular foliage and
crown development. Ecological Monographs 63: 277-304
+ Kelty, M.J. 1992: The ecology and silviculture of mixed-
species forests. Kluwer Academic publishers Dordrecht,
Netherlands.
+ Prentice, I.C.; Sykes ; Cramer, W. 1993: A simulation model
for the transient effects of climate change on forest
landscapes. Ecological Modelling 65: 51-70.
+ Botkin, D.B. 1993: Forest Dynamics: An ecological model.
Oxford University Press, Oxford.
+ Kimmins, J.P. 1993: Scientific foundations for the simulation of
ecosystem function and mangement in FORCYTE-11,
Information Report NOR-X-328, Forestry Canada, Ottawa.
+ Kimmins, J.P. 1990: FORCYTE-11 users manual for the bench-
mark version, ENFOR, Forestry Canada, Ottawa.
Yours
Michael Sonntag
Forschungsgruppe Umweltsystemanalyse
University of Kassel
Moenchebergstr. 11
34109 Kassel
Germany
Tel.: 0561 804 31 75
Fax: 0561 804 31 76
Mail: michael@usys.informatik.uni-kassel.de
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