Design, Establishment and Management of a Black Alder (Alnus glutinosa L. Gaertn.) Seed Orchard

Improved selections are being developed for use in the intensive culture of biomass for energy, nitrogen-fixing nurse crop plantings, and for soil reclamation plantings. As a complement to this selection work, we have been studying seed-orchard alternatives for the species by establishing and managing an experimental orchard. Five-year-old selected trees were moved by tree spade to establish the orchard. It has been expanded through the use of rooted cuttings. Our initial design of this orchard takes into account the existence of a self-incompatibility system in Alnus and tries to balance current uncertainties as to whether inter- or intra-provenance crosses should be favored. This design will be modified in place as our knowledge improves. Seed collections made from seven typical seed orchard trees in the fall of 1985 and 1986 gave a total seed yield of 3.6-7.4 million seeds (5630-11,693 g) with germination rates of 23-74%. Because of delayed fertilization in alder, it is likely to be important to be able to irrigate an orchard during early summer droughts to protect seed viability. Pollen dispersion from our plantings indicate that an isolation strip 710 m wide is needed to exclude 91% of the pollen from nonselected trees. Early fall is the best time for seed collection. A systemic insecticide has been used to control a defoliating insect in the orchard. We have begun studies to determine the feasibility of periodic coppicing of the seed orchard trees to facilitate seed collection and maintain smaller trees.

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Author(s): Richard B. Hall, R. N. Nyong'o

Publication: Tree Improvement and Genetics - Southern Forest Tree Improvement Conference - 1987