FAQs Help On-line Documentation Contacts Workshops/Training Publications and References

FAQs

Are TASS predictions realistic?

• Jim Goudie (1998) reported on the results of testing TASS yield tables against a portion of the plots and installations addressing various thinning strategies that have been analyzed to date. He concluded that: "While growth and yield models cannot be proven valid, models must be evaluated or tested against available data to identify potential biases. The system generally performs very well but may moderately overestimate the response to thinning in some cases".
• Jim Goudie (1996) also reported a comparison of lodgepole pine managed-stand yields tables generated by TASS in BC against plot data and a yield model used in Sweden. He concluded that:
  • The range in site productivity, and particularly the upper limit is very similar between the two countries;
  • The amount of standing cubic volume at a particular stage of development is also very similar between BC and Sweden;
  • Yields produced for one similar silvicultural regime by two very different computer models (TASS in BC and the model of Elfving, 1990 for Sweden) are quite similar for standing volume, culmination of mean annual increment, and, especially, total production. TASS predicts about 2 cm greater average diameter even though mortality rates of the Swedish model were higher before and after thinning.

Where do you turn when TASS can't generate the yield table you need?

If TASS does not have the species that you need you can select a closely related regime which gives reasonable results. These recommendations for species substitution will, at the very least, ensure consistency among users.

TASS can accommodate a large variety of runs. You can contact us to make customized TASS runs for treatments such us: custom spatial distributions, pruning, fertilization, pre-commercial and commercial thinning, root rot and spruce weevil infestation treatments. Response time varies from a day to several weeks depending upon the complexity of the task.

What other models can generate the information that you need?

Other models might generate the information you need. In the public domain, consider:

• Prognosis BC (Stage, 1973), Wykoff et al., 1982, Wykoff, 1986),
• DFSIM the Douglas-fir simulator (Curtis et al. 1981),
• STIM the Stand and Tree Integrating Model developed by the Canadian Forest Service (Bonnor, 1992), and

Proprietary models include the Stand Projection System (SPS; Arney, 1985) and XENO (Northway, 1989).

Help

Contacts

For additional information about TASS, please contact:  Ken Mitchell, Stand Modelling Research Leader.

For TASS custom runs, please contact:   Mario Di Lucca, Growth and Yield Applications Specialist.

Workshops/Training

TASS training and concepts are covered in Module III of the Silviculture Institute of British Columbia, in workshops offered at regional headquarters, and in association with other courses and meetings. In many cases, TASS concepts are introduced in TIPSY training courses. These are offered through the Forestry Continuing Studies Network.

An Introduction to Growth and Yield Computer Based Training (CBT) is a computer based training program for learning some basic growth and yield concepts and assumptions included in TASS.

Fred’s Forest is a Windows/MacOS forestry game generated with TASS that deals with timing of silvicultural treatments and harvesting to maximize profits.

Publications and References

Alfaro, R. I., G. Brown, K. J. Mitchell, K. R. Polsson and R. N. Macdonald. 1996. SWAT: A decision support system for spruce weevil management. pp. 31-44. In: T L. Shore and D. L. MacLean (Eds.). Decision support systems for forest pest management. FRDA No. 260.

Arney, J. D. 1985. A modeling strategy for the growth projection of managed stands. Can. J. For. Res. 15:511-518.

Bonnor, G. M. 1992. Developing a stand growth model for use in managed forests of British Columbia. In Proc. IUFRO Conf. on Integrating Forest Information Over Space and Time, Wood, J. and B. Turner (eds.). Anutech Pty Ltd., GPO Box 4 Canberra, Aust. p. 63-70

Bloomberg, W. J. 1990. Modeling control strategies for laminated root rot in managed Douglas-fir stands: model development. Phytopathology, Vol. 78, pp. 4903-4909.

British Columbia Ministry of Forests, 1999. Guidelines for Developing Stand Density Management Regimes. BC Ministry of Forests, Victoria, ISBN 07726-3746-6. 94 pp.

Brunner, A. 1988. A light model for spatially explicit forest stand models. For. Ecol. Manage. 107:29-46.

Curtis, R. O., G. W. Clendenen and D. J. Demars. 1981. A new stand simulator for coastal Douglas-fir: DFSIM, user's guide. USDA Forest Serv. Gen. Tech. Rep. PNW-128, Pac. Northwest For. and Range Exp. Sta., Portland, Oregon. 79 p.

Di Lucca, C. M. 1999. TASS/SYLVER/TIPSY: systems for predicting the impact of silvicultural practices on yield, lumber value, economic return and other benefits. In: Stand Density Management Conference: Using the Planning Tools. November 23-24, 1998, Colin R. Bamsey [Ed.] Clear Lake Ltd., Edmonton, AB. pp. 7-16.

Elfving, B. 1990. Nya produktionsdata och prognosfunktioner förcontortatall. (New yield data and functions for contorta pine) Sveriges Lantbruksuniversitet Institutionen för kogsskötsel Arbetsrapporter Nr 34. (Swedish Royal College of Forestry Department of Silviculture Working Report No. 34). 19 pp + Appendix.

Goudie, J. W. 1980. Yield tables for managed stands of lodgepole pine in northern Idaho and southeastern British Columbia. University of Idaho, Moscow, Idaho. 111 pp.

Goudie, J. W. 1996. A comparison between managed-stand yields of lodgepole pine in British Columbia and Sweden. p. 51-63. January 24 and,25, 1996, Smithers, BC, Tollestrup, P. (ed.). Northern Interior Vegetation Management Association, Prince George, BC.

Goudie, J. W. 1998. Model validation: A search for the magic grove or the magic model. In Stand density management conference: Planning and implementation, November 6-7, 1997, Edmonton, AB, Bamsey, C. pp. 45-58.

Greenough, J. A. and W. A. Kurz, 1996. Stand tending impacts on environmental indicators. B.C. Min. For. Silviculture Practices Branch. FRDA II- ISBN 0-7726-2943-9. 58 pp.

 McWilliams, E.G. and R.E.Carter, 1998. Silviculture investment opportunities: A Methodology for identifying key decision variables. Forest Renewal BC, No. HQ96463-RE. 102 pp.

Mitchell, K. J. 1969. Simulation of the growth of even-aged stands of white spruce. In Yale Univ. School of Forestry Bull. No 75, Yale University, New Haven, CN. 48 pp.

Mitchell, K. J. 1975. Dynamics and simulated yield of Douglas-fir. For. Sci. Monogr. 17, 39 pp.

Mitchell, K.J. 1978. Impact of planting density and juvenile spacing on the yield of Douglas-fir. pp. 143-158. In Joran Fries, Harold E. Burkhart and Timothy A. Max (editors). Proceedings of the Conference on Growth Models for Long Term Forecasting of Timber Yields and Forest Resources Management; Mensurations, Growth and Yield Section of IUFRO, Virginia Polytech. Inst and SU, Blacksburg, Virg.

Mitchell, K.J. 1986. Comparison of Mcardle, DFSIM, and TASS growth and yield models. pp. 350-359. In Proc. Symp. Douglas-fir: Stand management for the future, June 18-20, 1985, Seattle, Wash., C.D Oliver, D.P. Hanley, and J.A. Johnson (Editors). Inst. For. Res., Univ. Wash., Contrib. No. 55, Seattle, Wash.

Mitchell, K.J. 1987. Predicting the impact of silvicultural treatments on yield, products and value. pp. 44-60. In H.N. Chappell and Douglas A. Maguire (Eitors). Predicting Forest Growth and Yield: Current Issues, Future Prospects. College of Forest Resources, Univ. Wash., Seattle, Wash. Inst. For. Resources Contribution No. 58.

Mitchell, K.J. 1988. SYLVER: modelling the impact of Silviculture on Yield, Lumber Value and Economic Return. For. Chron. 64(2):127-131.

Mitchell, K.J. 1995. Simulate the Treatment Before Pruning the Stand. In D.P. Hanley, C.D. Oliver, D.A. Maguire, D.G. Briggs, and R.D. Fight (Editors). Forest Prunninf and Wood Quality of Western North American Conifers. Coll. For. Res., Univ. Wash., Seattle, Wash.

Mitchell, K. J. and I. R. Cameron. 1985. Managed stand yield tables for coastal Douglas-fir: initial density and precommercial thinning. B. C. Min. For., Res. Branch, Victoria, B. C. Land Manage. Rep. 31

Mitchell, K. J. and W. J. Bloomberg. 1986. Expanding concepts of growth and yield modelling to disease impacts and forest products. In Second Can. For. Serv. Modelling Workshop, 1986, Can. For. Serv., Victoria, B.C.

Mitchell, K.J., R.M. Kellogg, and K.R. Polsson. 1989. Silvicultural treatments and end-product value. pp. 130-167. In Second growth Douglas-fir: Its management and conversion for value. A report of the Douglas-fir Task Force, Kellogg, R. M. (editors). Forintek Canada Corp. Spec. Publ. No. SP-32, Vancouver, B.C. 173 p.odel. B.C. Min. For., Res. Branch, Unpubl. Rep. 31 pp.

Northway, S. M. 1989. XENO technical report. Internal Paper, Macmillan Bloedel Ltd., Nanaimo, B.C. 28 pp.

Stage, A. R. 1973. Prognosis model for stand development. USDA Forest Serv. Res. Pap. INT-137, Int. Northwest For. and Range Exp. Sta., Ogden, Utah. 32 pp.

Stone, M.S. 1993. An economic evaluation of commercial thinning Douglas-fir in the coastal region of British Columbia. FRDA Working Paper WP-6-002. Canadian Forest Service/BC Ministry of Forests, Pacific Forestry Centre, Victoria, B.C. 146 p.

Stone, M.S. 1996. Commercial thinning lodgepole pine: An economic analysis. FRDA Working Paper WP-6-017. Canadian Forest Service/BC Ministry of Forests, Pacific Forestry Centre, Victoria, B.C. 153 p.

Stone, M.S. 1998. Economics of Pre-commercial and Commercial Thinning. In Stand density management conference: Planning and implementation, November 6-7, 1997, Edmonton, AB, Bamsey, C. pp. 61-71.

Wykoff, W. R., C. L. Crookston and A. R. Stage. 1982. User's guide to the stand prognosis model. USDA Forest Serv. Gen. Tech. Rep. INT-133, Int. Northwest For. and Range Exp. Sta., Ogden, Utah. 122 pp.

Wykoff, W. R. 1986. Supplement to the User's guide to the stand prognosis model - version 5.0. USDA Forest Serv. Gen. Tech. Rep. INT-208, Int. Northwest For. and Range Exp. Sta., Ogden, Utah. 36 pp.