Actual and projected growth and yields of Populus 'Tristis #1' under intensive culture

Abstract

Yields and related stand characteristics of Populus 'Tristis #1' cuttings based on 4 years of growth under intensive culture (fertilization and irrigation) at square spacings of 0.75, 1, and 2 ft (0.23, 0.30 and 0.61 m) in northern Wisconsin are reported. Stem and branch wood yields were 40 390, 45 132, and 27 567 lb/acre (45 272, 50 586, and 30 899 kg/ha) for these spacings, and current annual increment peaked at age 3 for the 0.75- and 1-ft spacings. Tree growth and competition information from these plots was then used to calibrate a stand growth simulation model to develop yield projections to the 10- to 25-year range for the above plus 4-, 8-, and 12.7-ft (1.22-, 2.44-, and 3.87-m) spacings. Mean annual increment in terms of stem and branch wood dry weight for the projections peaked at about 8–15 years for all six spacings with values in the range of 13 881 – 16 584 lb/acre (15 559 – 18 588 kg/ha), respectively. The maximum mean annual increment was obtained at age 15 with a 4-ft spacing. Results further indicate substantial product-oriented flexibility in the choice of spacings and rotation ages since curves of mean annual increment are both similar and relatively flat in the 10- to 20-year range, except for the two widest spacings. A discussion of stand model projection methodology, reliability, and limitations is presented along with suggestions for more refined projections.