Pacific Northwest Forest Tree Seed Zones: A Template for Native Plants?

Abstract

Seed movement guidelines for restoration activities are lacking for most native grasses, forbs, and shrubs. The forestry community has decades of experience in establishing seed zones and seed movement guidelines that may be of value to restoration managers. We review the history of seed zone development in forest trees, with emphasis on the Pacific Northwest, and make some suggestions concerning seed transfer guidelines for other native plants. K E Y W O R D Sseed movement, genetic variation, adaptation ITIS (2002)he forestry community has been restoring, replanting, and reforesting lands with native tree species for decades in North America and for centuries in Europe. This work and early provenance tests show large amounts of source-related genetic variation within species for traits that are associated with adaptation, such as growth traits, cold hardiness, and phenology. As a consequence, the forestry community in the US Pacific Northwest (Oregon and Washington) initiated forest tree seed certification and a system of seed zones in the 1960s. These seed zones have been modified over time to incorporate new research information. Although adaptive variation in forest trees is usually continuous across the landscape, zones with distinct boundaries generally have been used to control seed use for administrative reasons. A seed zone is a mapped area with fixed boundaries in which seeds or plant materials can be transferred with minimal risk of maladaptation and, this is important in forestry, with minimal risk of a loss in productivity. Continuous zones, or seed transfer guidelines, are similar in that they recommend how far seeds can be transferred from point of origin, and describe the relative risk associated with that transfer.

Assessing Potential Seed Transfer Zones for Five Forb Species from the Great Basin Floristic Region, USA

“…Using differences identified within these studies, it is possible to delineate seed transfer zones, which are geographic regions where seed can be moved with minimal risk of being poorly adapted (Johnson et al 2004). The primary goal of seed transfer zones is to help land managers maximize the potential that sown seed will germinate, establish, persist, and reproduce at a restoration site without negatively impacting the genetic composition of remnant native plant populations (e.g., outbreeding depression) (McKay et al 2005).…”

“…The primary goal of seed transfer zones is to help land managers maximize the potential that sown seed will germinate, establish, persist, and reproduce at a restoration site without negatively impacting the genetic composition of remnant native plant populations (e.g., outbreeding depression) (McKay et al 2005). Seed transfer zones were first developed in the 1960s for timber species after unexpected losses and declines in productivity associated with the use of nonlocal material were seen in reforestation efforts years or sometimes even decades after establishment (Millar and Libby 1989;Johnson et al 2004). …”

“…This means that seed transfer zones are not universal but must be developed on a species-by-species basis (Hufford and Mazer 2003;Johnson et al 2004). For example, common garden studies carried out by the US Forest Service led to the delineation of very different seed transfer zones for two wind-pollinated timber species with overlapping distributions: western redcedar (Thuja plicata Donn ex D. Don) has 4 large seed transfer zones in Oregon, while the more narrowly adapted Douglas-fir (Pseudotsuga menziesii (Mirb.)…”

“…For example, common garden studies carried out by the US Forest Service led to the delineation of very different seed transfer zones for two wind-pollinated timber species with overlapping distributions: western redcedar (Thuja plicata Donn ex D. Don) has 4 large seed transfer zones in Oregon, while the more narrowly adapted Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) has 16 much smaller seed transfer zones covering the same area (Johnson et al 2004). This difference in seed transfer zone size has implications for the costs and challenges associated with developing, producing, and using plant material for restoration (Ying and Yanchuk 2006).…”

“…This difference in seed transfer zone size has implications for the costs and challenges associated with developing, producing, and using plant material for restoration (Ying and Yanchuk 2006). For example, sourcing species like Douglas-fir is more complicated and expensive than species like western redcedar (Johnson et al 2004;G. R. Johnson et al 2010).…”