Phenological Variation in Bluebunch Wheatgrass (Pseudoroegneria spicata): Implications for Seed Sourcing, Harvest, and Restoration

Kathryn Prive,Holly R Prendeville,Ronald J Reuter,Matthew R Orr,Francis F Kilkenny

doi:10.3390/land10101064

Abstract

To reduce maladaptation in cultivated seed lots, seed transfer zones (STZs) have been developed for grasslands and other habitats using morphological traits and phenological measurements that only capture the first day of events such as flowering and seed ripening. Phenology is closely linked to plant fitness and may affect genetic loss during harvests of seed raised for ecological restoration. Here, we measured the detailed phenologies of 27 populations from six STZs of bluebunch wheatgrass (Pseudoroegneria spicata) (Pursh) Á. Löve (Poaceae) raised in a common garden to test whether existing STZs created using a combination of plant morphology and “first-day” phenological measurements adequately capture population-level variation in season-long, detailed phenologies. We also used detailed phenologies to test whether genetic losses may occur during single-pass harvests of commercial seed. Mixed and random effect models revealed differences in detailed reproductive phenology among populations within two of six STZs. The number of individual plants within an STZ not producing harvestable seed during peak harvest levels indicated that 10–27% of individuals from a seed lot could be excluded from a single-pass harvest. Although our findings generally support current STZ delineations for P. spicata, they point to the possible precautionary importance of sourcing from multiple populations and harvesting with multiple passes when resources permit.

Highlights

Ecological restoration is needed over large areas of the Intermountain West in grasslands disturbed by wildfire, over-grazing, and invasive species [1,2]
We focus on bluebunch wheatgrass (Pseudoroegneria spicata), a bunchgrass commonly used for ecological restoration in the Intermountain West [33,34], that has high phenotypic variance among individuals and populations [23], and which enters flowering, ripening, and dispersal in recurring flushes
We found that a hypothetical single-pass harvest at peak ripeness could reduce seed collection by 10%–27% of individual plants, depending on the seed transfer zones (STZs) (Table 3, Table 4, and Table S3a–e)

Summary

Introduction

Ecological restoration is needed over large areas of the Intermountain West in grasslands disturbed by wildfire, over-grazing, and invasive species [1,2]. Native local seed sources adapted to project site conditions are in need of restoration because their use may improve population establishment and persistence [3,4,5,6]. While genetic diversity has been successfully conserved in some propagated lines of Intermountain West plants [7], commercially available sources often represent a fraction of the genetic diversity that exists across the areas in which they are planted [8,9]. Genetic variation plays a fundamental role in determining whether species can adapt to variable environmental conditions and requires consideration in restoration [10,11,12]. Meeting commercial demands for native seed requires knowledge of adaptation and genetic variation across landscapes

Methods

Results

Conclusion