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Forest Mensuration II. Lecture 13 Growth and Yield Models Avery and Burkhart, Chapter 16. A few thoughts. Forest management decisions-making relies on accurate information about both current and future forest resource conditions
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Forest Mensuration II Lecture 13 Growth and Yield Models Avery and Burkhart, Chapter 16
A few thoughts • Forest management decisions-making relies on accurate information about both current and future forest resource conditions • Stand-table projections for future growth based on the past may be most accurate for a limited period of time, but • Not reliable for long periods • Not necessarily useful for evaluate treatment alternatives because … • Therefore, many models for forecasting stand dynamics are developed, ranging from tables, equations, to computer simulation models
Definition of yield • The total amount available at a given point of time • gross volume • merchantable volume • biomass
10 cm: Pj, Sb, Sw, Bf, Ce 16 cm: Pw, Pr, He, Po, Bw 20 cm: other hardwoods A Total biological growth Top D Growth C Growth actually removed and utilized Merchantable 30 cm OMNR (1995) Scaling Manual Definition of yield (cont.) – Merchantability B Potential usable growth under present technology and policy
Merch Merchantability Definition of yield (cont.) Plonski 1974 Gross
Definition of growth • The increase (increment) over a given period of time • Mean annual increment (MAI) • Periodic annual increment (PAI)
Nature Development Simple Application Even-aged Empirical Sophisticated Process Uneven-aged Types of Models Whole stand models Diameter class models Individual tree models
Whole stand models Model type Equations • Density-free models • Normal yield tables • Empirical yield tables for average stands • Variable density models • Predict yield • Predict growth (g12) and yield (V1)
Diameter class models Model type Equations • Empirical stand table projections
Individual tree models Model type Equations • Distance-dependent • Distance-independent
Which type of models is best suited for the following situations? Why? • Depends on purposes of modeling…, but if … • Even-aged, single species stands? • Uneven-aged single species stands? • Even- and uneven-aged, mixed-species stands?
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