Grass Seedling Demography and Sagebrush Steppe Restoration

Abstract

Seeding is a key management tool for arid rangeland. In these systems, however, seeded species often fail to establish. A recent study in Wyoming big sagebrush steppe suggested that over 90% of seeded native grass individuals die before seedlings emerged. This current study examines the timing and rate of seed germination, seedling emergence, and seedling death related to this demographic bottleneck. We seeded monocultures of two native perennial bunchgrasses, Pseudoroegenaria spicata (Pursh)Á. Löve and Elymus elymoides (Raf.) Swezey, and one introduced bunchgrass, Agropyron desertorum (Fisch. ex Link) Schult., in 2007, 2008, and 2009 and tracked sown seed and seedling fate. Across the study years and species we found that germination was rapid and high, with species obtaining 50% germination by December, less than 2 mo after planting. Emergence of germinated seed did not occur until late February for A. desertorum and March for the two native grasses. In 2007 the majority of emergence and death was constrained to several weeks, whereas in 2008 and 2009 emergence and death was distributed across several months. The timing of seedling emergence did not influence survival probability or midday plant water potential (probability of exceedance , 0.05). Survival probabilities once seedlings emerged were greater for native species (0.71) than A. desertorum (0.51) in 2 of the 3 study yr (probability of exceedance. 0.98). The early germination of grasses following fall seeding, and the long 2-to 3-mo period that germinated grass seed remain in the soil before emerging, support the hypothesis that seedling recruitment might be limited largely by ecological processes and conditions during winter or early spring (such as soil freeze-thaw events, seed pathogens, or physical crusts). Delaying seeding to early winter or spring and other management tools that mitigate these factors driving this bottleneck might greatly improve restoration outcomes in these systems. Resumen Las resiembras son una herramienta clave de manejo para pastizales á ridos. En estos sistemas, sin embargo, las especies sembradas a menudo no se establecen. En un estudio reciente en un pastizal de Artemisia en Wyoming se sugiere que má s del 90% de los individuos sembrados de pastos nativos mueren antes que la plántula germine. Este estudio examina laépoca y tasa de germinación de las semillas, la aparición de la plá ntula, y la muerte de plá ntula relacionadas con el cuello de botella demográ fico. Se sembraron monocultivos de dos especies nativas de pastos amacollados, Pseudoroegenaria spicata (Pursh)Á. Löve y Elymus elymoides (Raf.) Swezey, y también un pasto amacollado introducido, Agropyron desertorum (Fisch. ex Link) Schult., durante 2007, 2008, y 2009 y se le dio seguimiento a las semillas sembradas así como el destino de las plántulas. A través de los años de estudio y especies se vio que la germinación fue rá pida y alta, con la obtención de la germinación del 50% en diciembre, menos de 2 meses después de la siembra de especies. La aparición de sem...

Spicing up restoration: can chili peppers improve restoration seeding by reducing seed predation?

“…Reseeding is a cost‐effective approach to recovering native plant communities when it works; however, its efficacy is unpredictable due to strong abiotic and biotic limitations on seedling establishment (James et al ). Here, we provide evidence that natural plant chemical defenses against seed predators can be applied to native seeds to reduce seed predation and increase success of native plant reseeding efforts, while also reducing restoration costs per established plant.…”

“…Mounting evidence indicates that seed limitation commonly inhibits native plant establishment, a situation that can be exacerbated by disturbances and exotic plant invasions (Seabloom et al ; Clark et al ; Turley et al ). However, reseeding efforts aimed at augmenting natural plant establishment have notoriously low success (James et al ) and can be costly (Taylor et al ). The limited capacity to recover native plants by sowing seeds following disturbances and management activities presents a major gap in restoration technology (Madsen et al ).…”

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

“…For E. ovalifolium (a spring-flowering species), 100% germination was achieved for most source populations and treatments, while in E. microthecum (a summer-flowering species), 100% germination for some source populations was only achieved after a second round of winter conditions (data not shown), suggestive of a bet-hedging strategy (Evans et al 2007). Seed germination is a critical step in restoration establishment (James et al 2011;James et al 2012), yet seed germination requirements are rarely explicitly incorporated in common garden studies geared toward delineating seed transfer zones (but see Erickson et al 2004;Wilson et al 2008;St. Clair et al 2013).…”

Use of auto‐germ to model germination timing in the sagebrush‐steppe

“…Seed germination timing strongly impacts the success of direct seeding efforts in wildland systems by influencing exposure to pathogens, nutrients and soil moisture, temperature, light, herbivory, and other biotic and abiotic factors (Gornish et al., ; James & Carrick, ). For these reasons, several studies have tracked germination timing in the field to better understand and improve seeding outcomes (Abbott & Roundy, ; Boyd & James, ; Gerrit, ; James, Rinella, & Svejcar, ). However, tracking seed germination timing in the field can be challenging, resource intensive, and time‐consuming.…”

“…and improve seeding outcomes (Abbott & Roundy, 2003;Boyd & James, 2013;Gerrit, 1991;James, Rinella, & Svejcar, 2012).…”