Stocktype and Vegetative Competition Influences on Pseudotsuga menziesii and Larix occidentalis Seedling Establishment

Abstract

Douglas fir (Pseudotsuga menziesii var. glauca (Mayr) Franco), and western larch (Larix occidentalis Nutt.) are species of ecological and commercial importance that occur throughout the Western United States. Effective reforestation of these species relies on successful seedling establishment, which is affected by planting stock quality, stocktype size, and site preparation techniques. This study examined the effects of container volume (80, 130, 200, and 250 cm 3) and vegetative competition on seedling survival and physiological and morphological responses for two years, post-outplanting. Glyphosate application (GS) and grass planting (HC) were used to achieve low and high levels of competition. For all measured attributes, the container volume × vegetative competition was not significant. Mortality was strongly influenced by competition, with higher mortality observed for Douglas fir and western larch planted in HC plots one (28% and 98%) and two (61% and 99%) years following outplanting. When competition was controlled, seedlings of both species exhibited greater net photosynthesis (>9 µmol m −2 s −1), greater predawn water potential (>−0.35 MPa), and lower mortality (2-3%) following one year in the field, indicating establishment success. The 80 cm 3 stocktype remained significantly smaller and exhibited lower growth rates for the duration of the study, while all other stocktypes were statistically similar. Our results demonstrate the importance of controlling vegetative competition regardless of stocktype, especially for western larch, and suggest that benefits to post-planting seedling physiology and growth in relation to container size plateau beyond 130 cm 3 among the investigated stocktypes.

Seedling Production and the Field Performance of Seedlings

“…Because seedling quality consists of several features, such as the genetic source, morphological properties, nutritional status, stress resistance and the vitality of the seedlings, the seedling responses to different nursery practices may be variable in different tree species and under variable growth conditions [1,5]. In this Special Issue, Pinchot et al [6] and Pinto et al [7] consider the relationship between the initial size of the seedlings and their growth after outplanting. These studies highlight once more how the responses of the seedlings to different nursery practices are dependent on plant species and stock type.…”

Eight-year survival and growth of Sakhalin fir (Abies sachalinensis) seedlings with one weeding operation: Impact of mechanical site preparation, vegetation release, summer planting, stock type, and forwarder trail

“…6b). This dissimilarity in duration may be attributed to tree seedlings favoring height growth over diameter expansion under competitive conditions (Richardson et al 1996;Collet and Chenost 2006;Pinto et al 2018;Sugai et al 2023). Although soil compaction can directly impede tree seedling growth (Kozlowski 1999;Cambi et al 2015;Mariotti et al 2020), it can indirectly promote growth by inhibiting the growth of competitive vegetation (Figure S4a) (Brais 2001).…”

Eight-year survival and growth of Sakhalin fir (Abies sachalinensis) seedlings with one weeding operation: Impact of mechanical site preparation, vegetation release, summer planting, stock type, and forwarder trail

“…6b). This dissimilarity in duration may be attributed to tree seedlings favoring height growth over diameter expansion under competitive conditions (Richardson et al, 1996;Collet and Chenost, 2006;Pinto et al, 2018;Sugai et al, 2023). Although soil compaction can directly impede tree seedling growth (Kozlowski, 1999;Cambi et al, 2015;Mariotti et al, 2020), it can indirectly promote growth by inhibiting the growth of competitive vegetation (Figure S4a) (Brais, 2001).…”