Eyeing emergence: modified treatments for terminating dormancy of conifer seeds

Many seeds of coniferous species display a deep primary dormancy at maturity and require several weeks of pretreatment to produce seed populations that germinate in a vigorous and timely manner. Facilitating an efficient transition from dormancy to germination by devising improved protocols for dormancy breakage is not only important to conifer seed research, aiding in the study of the dormancy process itself, but is also of interest and applicability to commercial forest nursery operations. In the forests of British Columbia, Canada, several conifer species are well-adapted to their environment, with seeds needing to experience long durations in the moist state at cool or fluctuating temperatures. These include yellow-cedar (Callitropsis nootkatensis), western white pine (Pinus monticola), and true fir species, such as Pacific silver fir and subalpine fir (Abies amabilis and A. lasiocarpa, respectively). In this chapter, we discuss the development of new dormancy-breaking protocols for the aforementioned species that centre on the balance of several key aspects: (1) reducing the time needed to terminate dormancy in the seed population; (2) synchronicity of germination; (3) ease of use; (4) cost-effectiveness; and (5) repeatability. Where possible, any new or modified protocol should be further tested in relationship to promoting rapid seedling growth in a forest nursery greenhouse setting and after planting at natural stands. Based on the five criteria listed above, very significant improvements compared to traditional dormancy-breaking methods have been achieved for the targeted conifer species. Where tested (e.g. yellow-cedar), the modified dormancy-breaking treatments result in vigorous growth in the greenhouse and after planting at natural stands.