Production System Influences the Survival and Morphology of Rooted Stem Cuttings of Loblolly Pine (Pinus taeda L.) and Sweetgum (Liquidambar styraciflua L.)

Abstract

Forest planting stock must be capable of high rates of survival and good field performance to justify the expense of reforestation efforts. Seedling grading standards have improved the quality of forest planting stock and have increased expectations for survival and field growth of out-planted forest seedlings. For many tree species, rooting stem cuttings provides an alternative means of producing planting stock to that of conventional seedling propagation. Use of rooted stem cuttings (rooted cuttings) in forestry has many potential advantages for both research and operational applications. However, to realize these benefits, it is important that high quality rooted cuttings are produced to enable field performance on par with seedlings of the same species and similar provenance. Developing specific grading standards for rooted cutting planting stock, therefore, is critical for successful field performance, and, is a topic of increasing interest for clonal forestry of particular species. Grading standards for rooted cuttings may differ from those of seedlings, because of potential biological differences and increased production costs for rooted cuttings. Furthermore, various production systems exist capable of producing high quality rooted cutting planting stock and may require individual grading standards. Loblolly pine and sweetgum, to a lesser degree, are two commonly out-planted forest tree species in the southeastern United States. Seedling grading standards exist for both species in this region. Increased interest in clonal propagation of loblolly pine and sweetgum requires development of rooted cutting grading standards to ensure high rates of survival and good field performance. Two studies conducted in 2000 and 2001 investigating rooted cutting production systems for loblolly pine and sweetgum are described in the following two chapters. The effects of a transplant, a containerized, and a direct-stick production system on morphological characteristics of loblolly pine rooted cuttings were evaluated in the first chapter. Morphological comparisons were made among the various stock types tested. In the second chapter, feasibility and morphological effect of a transplant, a containerized, and a direct-stick rooted cutting production system were evaluated for sweetgum. Semi-hardwood (SH) stem cuttings of sweetgum were tested in all three production systems with special emphasis placed on the presence of new shoot growth following rooting. Hardwood (H) stem cuttings of sweetgum were also rooted in a direct-stick system in an outdoor nursery bed to test the reported ability of this cutting type to produce new shoot growth in the same season as rooting. Rooted cutting morphology varied among clone and production system for both loblolly pine experiments. By the second loblolly pine experiment, over 90% of the rooted cuttings produced in the systems tested met acceptable seedling grading standards, including the second cycle (May sticking). Results of this study demonstrated that all three production systems evaluated were capable of producing high quality planting stock and that two full production cycles can be obtained in one growing season in the containerized and transplant systems. All four production systems evaluated in the sweetgum study produced rooted cuttings. Morphological measurements varied among these same rooted cuttings according to production system. The transplant and containerized systems produced a large number of rooted cuttings with high rates of survival and large root systems. The SH direct-stick system produced rooted cuttings with sizeable root systems, but proved more sensitive than the other systems tested. A SH direct-stick system requires a back up irrigation system and a secondary power source to be effective. The H direct-stick production system was the only system to produce rooted cuttings exhibiting substantial shoot growth during the first growing season. Some of these rooted cuttings also developed extensive root systems, but survival was low.

Description

Keywords

containerized stock, bare-root stock, transplant stock, root collar diameter, adventitious root formation

Citation

Degree

MS

Discipline

Forestry

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