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

Jeremiah Pinto,Olga Kildisheva,Bridget Mcnassar,Anthony Davis

doi:10.3390/f9050228

Jeremiah Pinto, Olga Kildisheva + Show 2 more

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https://doi.org/10.3390/f9050228

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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 cm3) 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 cm3 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 cm3 among the investigated stocktypes.

Highlights

IntroductionIn order to ensure success, reforestation efforts must meet diverse objectives, which can involve myriad species, fit within a variety of economic models, and account for different site characteristics
In order to ensure success, reforestation efforts must meet diverse objectives, which can involve myriad species, fit within a variety of economic models, and account for different site characteristics.tree seedlings used in these efforts should be produced with specific parameters in mind [1,2,3]
Our study aims to examine the role of container size on seedling performance, while reducing confounding commonly associated with nursery culture, and create distinct drought differences between vegetative competition treatments at the site level

Summary

Introduction

In order to ensure success, reforestation efforts must meet diverse objectives, which can involve myriad species, fit within a variety of economic models, and account for different site characteristics. Tree seedlings used in these efforts should be produced with specific parameters in mind (genetics, morphology, and physiology, for example) [1,2,3]. Successful seedling stocking on a site within the required planting window may have economic, ecological, and legal implications—calling for high-quality, -cultured plant material. Science-based information to justify on-the-ground decision-making; determining which traits lead to optimal seedling performance for a specific site and reforestation objectives continues to be a challenge. Seedling phenotypic traits are a result of genetics and the environment. Nurseries have the capacity to alter these traits through modifications in nursery culture, including container size

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