Yields of Minirotation Closely Spaced Hardwoods in Temperate Regions: Review and Appraisal

Published data are reviewed on the yields of ovendry stems and branches (S and B) with bark, and the mean annual increments (denoted MAISB) obtained fro 1 to 5-year old closely planted Platanus occidentalis, Populus spp., Ulmus parvifolia, and Alnus rubra, growing in north temperate regions. Data were discounted when the heights of sample trees inside experimental plots exceeded four times their distance from the edges of the plots. With the exception of 4 year yields of intensively cultured poplars in Wisconsin, all published yield data fell close to, or below, the response surface described empirically by the equation the square root of t/ha equals 1.19 plus 1.46 (age in years) plus 0.328 (log 1,000 tree/hectare). The ''working maximum'' MAISB of 4 to 5 year old minirotations forests in much of the temperate zone seems to be 10-12 ton/hectare/year, no greater than the MAISB of some Populus plantations grown over rotations of 11-26 years. However, 10-30 percent greater yields have been recorded at ages 1-5 following coppicing, and MAISB values probably continue to increase after age 5.