Slope and Aspect Effects on Seedbed Microclimate and Germination Timing of Fall-Planted Seeds

Boehm, Alex R.; Hardegree, Stuart P.; Glenn, Nancy F.; Reeves, Patrick A.; Moffet, Corey A.; Flerchinger, G. N.

doi:10.1016/j.rama.2020.12.003

Cited by 14 publications

(8 citation statements)

References 56 publications

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“…Mountainous regions provide a strong environmental filter, but are also topographically complex at a local scale (e.g. slope angle and aspect), which alters climate and growing conditions (Geiger et al 2009;Ackerly et al 2010;Graae et al 2012;Lenoir et al 2013) and can increase germination and shape species distributions (Rew et al 2005;Blumenthal et al 2012;Boehm et al 2021). Micro-topography can provide footholds, or refugia, for non-native species above their ideal climate conditions, thereby facilitating plant invasions into higher elevations (Lembrechts et al 2018).…”

Section: Micro-topography: Slope Angle and Aspectmentioning

confidence: 99%

Climate change and micro-topography are facilitating the mountain invasion by a non-native perennial plant species

Larson¹,

Pollnac²,

Schmitz³

et al. 2021

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Mountainous areas and their endemic plant diversity are threatened by global climate change and invasive species. Mountain plant invasions have historically been minimal, however, climate change and increased anthropogenic activity (e.g. roads and vehicles) are amplifying invasion pressure. We assessed plant performance (stem density and fruit production) of the invasive non-native forb Linaria dalmatica along three mountain roads, over an eight-year period (2008–2015) in the Greater Yellowstone Ecosystem (GYE), USA. We evaluated how L. dalmatica performed in response to elevation, changed over time, responded to climate and how the climate of our sites has changed, and compared elevation, climate, micro-topography (slope aspect and angle), and fruit production among sites with differing temporal trends. Linaria dalmatica stem density and fruit production increased with elevation and demonstrated two temporal groups, those populations where stem densities shrank and those that remained stable or grew over time. Stem density demonstrated a hump-shaped response to summer mean temperature, while fruit production decreased with summer mean maximum temperature and showed a hump-shaped response to winter precipitation. Analysis of both short and long-term climate data from our sites, demonstrated that summer temperatures have been increasing and winters getting wetter. The shrinking population group had a lower mean elevation, hotter summer temperatures, drier winters, had plots that differed in slope aspect and angle from the stable/growing group, and produced less fruit. Regional climate projections predict that the observed climate trends will continue, which will likely benefit L. dalmatica populations at higher elevations. We conclude that L. dalmatica may persist at lower elevations where it poses little invasive threat, and its invasion into the mountains will continue along roadways, expanding into higher elevations of the GYE.

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Section: Micro-topography: Slope Angle and Aspectmentioning

confidence: 99%

Climate change and micro-topography are facilitating the mountain invasion by a non-native perennial plant species

Larson¹,

Pollnac²,

Schmitz³

et al. 2021

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“…For example, restoration success varies with elevation (Knutson et al 2014; Germino et al 2018), topography (e.g. slope and aspect, Boehm et al 2021), and soil properties (Barnard et al 2019; Davidson et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Management and environmental factors associated with simulated restoration seeding barriers in sagebrush steppe

Copeland

Bradford

Hardegree

et al. 2022

Restoration Ecology

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Adverse weather conditions, particularly freezing or drought, are often associated with poor seedling establishment following restoration seeding in drylands like the Great Basin sagebrush steppe (U.S.A.). Management decisions such as planting date or seed source could improve restoration outcomes by reducing seedling exposure to weather barriers. We simulated the effects of management and environmental factors on seedling exposure to post‐germination barriers for bottlebrush squirreltail (Elymus elymoides), Sandberg bluegrass (Poa secunda), and bluebunch wheatgrass (Pseudoroegneria spicata). We combined germination timing models with daily soil moisture and temperature estimates to calculate yearly germination favorability and post‐germination freezing and drought barriers for three planting dates (15 October, 15 November, and 15 March) and three seed sources or cultivars per species for 5,000 sites in each of 40 years (water years 1980–2019). We tested the effects of site environmental variables (elevation, mean annual precipitation, heat load, and clay content) and management choices (seed source and planting date) on germination favorability and barrier occurrence (mean) and variability (coefficient of variation). Seedling exposure to barriers was strongly linked to management decisions in addition to site mean precipitation and elevation. Later fall plantings and seed sources with slower germination (lower mean germination favorability) were less likely to encounter freezing and drought barriers. These results suggest that management actions can play a role comparable to site environmental variables in reducing exposure of vulnerable seedlings to adverse weather conditions and subsequent effects on restoration outcomes.

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“…If over‐winter barriers to germinated seed are among the primary drivers of restoration failure, postponing seed delivery so that seeds do not germinate until early spring will avoid such barriers. Delay of seed delivery can translate into reduced probability of pre‐winter germination and reduced exposure to winter‐related barriers (Richardson et al 2018; Hardegree et al 2020; Boehm et al 2021), but practitioners targeting a late fall or early winter planting risk disruption by incompatible weather (Monsen & Stevens 2004) and most large post‐wildfire seedings are already constrained by contractor schedules and seed availability (Eiswerth & Shonkwiler 2006; Hardegree et al 2016). Delaying implementation into spring is often not possible until frozen or wet soils have dried, and wet spring soils are critical for germination and emergence.…”

Section: Introductionmentioning

confidence: 99%

“…Deliberately altering seed germination timing using seed coatings is precedented in agriculture (Archer & Gesch 2003; Johnson et al 2004; Stendahl 2005; Pedrini et al 2017) but is a relatively new concept for use in the restoration of semiarid wildlands, with strong theoretical support in our system (Hardegree et al 2020; Boehm et al 2021), but only a few studies to date, globally (Richardson et al 2019; Pedrini et al 2020; Keefer et al 2021). Altering germination timing via treatments or coatings is more appropriate for maintaining genetic diversity in restoration seed than other more permanent means to modify germination timing, such as selection or breeding (Erickson et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Can delaying germination reduce barriers to successful emergence for early‐germinating, fall‐sown native bunchgrass seeds in cold deserts?

Baughman

Kerby²,

Boyd

et al. 2022

Restoration Ecology

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Efforts to restore semiarid wildlands in the western United States predominantly use fall seeding. Fall conditions are more amenable to seeding, and successfully over-wintered seeds or plants are poised to take full advantage of spring moisture. However, over-winter mortality can be a barrier to seeding success. One solution to avoid winter mortality without sacrificing the benefits of fall seeding is to delay germination of fall-sown seeds. At six northern Great Basin field sites over three planting years (18 trials), we tested whether a hydrophobic seed coating reliably delayed germination and increased seedling establishment of a native bunchgrass. Despite considerable variation among sites and years, seed treatment successfully reduced prewinter germination by 84% compared to untreated, but also consistently reduced final germination by 23%. Still, treatment resulted in an average of 2.1-fold higher emerged seedling density in seven trials, six of which were among the eight trials where more than 50% of untreated seeds germinated pre-winter. Emergence was greater for untreated seed in five trials, all of them in the same year, and all but one of them with below-average total germination. Our treatment consistently reduced pre-winter germination, but only improved emergence when pre-winter germination of untreated seeds was high. Continued research is merited with germination-delaying treatments and to experimentally define-and develop models that predict-winter-related mortality barriers. We also suggest future exploration of bet-hedging strategies that mix treated and untreated seeds where fall seeding is required and significant but variable risk of over-winter seedling mortality exists.

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Slope and Aspect Effects on Seedbed Microclimate and Germination Timing of Fall-Planted Seeds

Cited by 14 publications

References 56 publications

Climate change and micro-topography are facilitating the mountain invasion by a non-native perennial plant species

Climate change and micro-topography are facilitating the mountain invasion by a non-native perennial plant species

Management and environmental factors associated with simulated restoration seeding barriers in sagebrush steppe

Can delaying germination reduce barriers to successful emergence for early‐germinating, fall‐sown native bunchgrass seeds in cold deserts?

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