Uneven-aged stands

Stands are distinguished by lacking a definite beginning or end in time.

• Trees on any given area vary by age as well as size andfrequently can be of several different species.
• The range of difference is usually more than 25% of rotation
• The system favors the tolerant climax species as the new seedlings grow up under the shade of old trees.

Uneven aged stands could be conceptualized as a summation of several different even-aged stands growing on the same parcel of land at the same timeUneven aged stands have considerable differences in the age of the trees present and three or more age classes are represented

Characteristics of uneven-aged forest

Reverse J-shaped for uneven-aged stands

Growth

1. Early stage: Extremely slow while sapling is dominatedby overwood.
2. Middle stage: Tree is growing more rapidly but is stillseverely affected by its larger neighbors.
3. Final stage: Tree is dominant with a large, free, well-developed crown and neighboring trees ofsame size are few and distant.

Yield of Uneven aged forest

Growth & Yield Equations: Moser & Hall (1969) developed equation of Volume-age for uneven aged stands

Y=[(y₀) (8.3348BA₀^-1.3175)] * [0.9348-1.0203BA₀^-0.0125)e^-0.0062t]-105.4

y₀ is the initial volume in cft/acre, BA₀ is initial Basal area/acre, t=time elapsed interval, year from initial conditions, Y= is predicted volume in cft, t yrs after observation of initial conditions y₀ and BA₀ at time

Difficulties

• In modeling uneven aged stands: stands composed of trees that differ markedly in age.
• Age is not usable variable for Growth & Yield prediction purpose
• Site quality assessment by site-index method is questionable