Non‐linear Shift from Grassland to Shrubland in Temperate Barrier Islands

Huang, Heng; Zinnert, Julie C.; Wood, Lauren K.; Young, Donald R.; D’Odorico, Paolo

doi:10.1002/bes2.1421

Cited by 6 publications

(17 citation statements)

References 49 publications

(76 reference statements)

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“…Warming temperatures, especially in winter, have been identified as a driver of woody expansion on the VCR in recent decades (Huang et al. ). However, endogenic processes, such as seed dispersal, have not been studied in this system.…”

Section: Methodsmentioning

confidence: 99%

“…, Huang et al. ). In coastal ecosystems, encroaching shrubs may reduce wind effects including sea spray, provide perches to facilitate bird dispersal of seeds, and moderate local microclimate including temperatures, humidity, and light (Thompson et al.…”

Section: Introductionmentioning

confidence: 99%

“…, Huang et al. ), and may affect sediment mobility as islands respond to sea level (J. C. Zinnert, et al. unpublished manuscript ; Zinnert et al.…”

Section: Introductionmentioning

confidence: 99%

“…1). This abrupt shift in species composition has been attributed to climate warming and sustained microenvironmental modification by the expanding species, Morella cerifera L. (Myricaceae; Zinnert et al 2011, D'Odorico et al 2012, Thompson et al 2017, Huang et al 2018, and may affect sediment mobility as islands respond to sea level (J. C. Zinnert, et al unpublished manuscript;Zinnert et al 2017). Understanding dispersal and post-dispersal establishment is essential for predicting future encroachment in this rapidly changing landscape where islands are disconnected from the mainland and one another.…”

Section: Introductionmentioning

confidence: 99%

“…Established plants may ameliorate microenvironmental conditions (e.g., reduced soil temperature, increased soil moisture and nutrients; Stinca et al 2015, Barron-Gafford et al 2017. Thus, encroaching species may have a favorable impact on their own establishment through these microenvironmental modifications (D'Odorico et al 2012, Huang et al 2018. In coastal ecosystems, encroaching shrubs may reduce wind effects including sea spray, provide perches to facilitate bird dispersal of seeds, and moderate local microclimate including temperatures, humidity, and light (Thompson et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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Interaction of seed dispersal and environmental filtering affects woody encroachment patterns in coastal grassland

et al. 2019

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Encroachment of woody plants into grasslands has occurred worldwide and includes coastal ecosystems. This conversion process is mediated by seed dispersal patterns, environmental filtering, and biotic interactions. As spatiotemporally heterogeneous, harsh environments, barrier islands present a unique set of challenges for dispersal and establishment. Environmental conditions act as filters on dispersed seeds, thereby influencing encroachment and distribution patterns. Seldom have patterns of propagule dispersal been considered in the context of woody encroachment. We quantified dispersal and post‐dispersal processes of an encroaching woody population of Morella cerifera relative to directional rate of encroachment and observed distribution patterns on an Atlantic coastal barrier island with strong environmental filtering. We analyzed historic foredune elevation as a proxy for reduced interior environmental stress. The dispersal kernel was leptokurtic, a common characteristic of expanding populations, but rate of encroachment has slowed since 2005. Expansion pattern was related to foredune elevation, which limits encroachment below a threshold elevation. This difference between dispersal kernel behavior and encroachment rate is due to limited availability of suitable habitat for Morella and temporal variability in chlorides during the time of germination. Our results demonstrate that processes mediating seeds and seedling success must be accounted for to better understand establishment patterns of encroaching woody plants.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…, Huang et al. ), and may affect sediment mobility as islands respond to sea level (J. C. Zinnert, et al. unpublished manuscript ; Zinnert et al.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Interaction of seed dispersal and environmental filtering affects woody encroachment patterns in coastal grassland

et al. 2019

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Seasonal facilitative and competitive trade‐offs between shrub seedlings and coastal grasses

2020

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Citation: Sinclair, M. N., N. N. Woods, and J. C. Zinnert. 2020. Seasonal facilitative and competitive trade-offs between shrub seedlings and coastal grasses. Ecosphere 11(1):Abstract. Shrub expansion is occurring in grasslands globally and may be impacted by the balance of competition and facilitation with existing grasses. Along the mid-Atlantic and Gulf coasts, the native shrub Morella cerifera (wax myrtle) is rapidly expanding and displacing other native coastal species. Recent research suggests that much of this expansion is due to warming winter temperatures, as temperatures below À15°C kill M. cerifera. The objective of this project was to understand the importance of species interactions with grasses on the growth and physiology of M. cerifera at the seedling life stage through both field and laboratory experiments. In the field, grasses were removed around seedlings and microclimate and shrub physiology and growth were measured. Seeds and seedlings were experimentally frozen to measure the freeze tolerance at both life stages. We found that grasses provided~1.3°C insulation to shrubs during winter. A freezing threshold for M. cerifera seedlings was experimentally found between À6°C and À11°C, but seeds remained viable after being frozen to the coldest ecologically relevant temperatures. Seedlings competed for light with grasses during warm months and grew more where grasses were clipped, revealing a trade-off between winter insulation and summer light competition. Morella cerifera exhibits ecosystem engineering at the seedling stage by significantly reducing summer maximum temperatures. When seedlings are very young (less than one year), grasses appear to improve germination and seedling survival. These phenomena enable rapid expansion of M. cerifera across the landscape and likely inform shrub expansion mechanisms in other systems. Although seedlings are small and relatively vulnerable, this life stage appears to have significant implications for ecosystem trajectory in grasslands undergoing shrub encroachment.

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Exploring the Impacts of Shrub‐Overwash Feedbacks in Coastal Barrier Systems With an Ecological‐Morphological Model

et al. 2022

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Shrubs are common – and presently expanding – across coastal barrier interiors (the land between the foredune system and back‐barrier bay), and have the potential to influence barrier morphodynamics by obstructing cross‐shore overwash flow. The ecological and geomorphological consequences of ecomorphodynamic couplings of the barrier interior, however, remain largely unexplored. In this contribution, we add an ecological module of shrub expansion and mortality to a spatially‐explicit exploratory model of barrier evolution (Barrier3D) to explore the effects of shrub‐barrier feedbacks. In our model simulations, we find that the presence of shrubs significantly alters barrier morphology and behavior. Over timescales of decades to centuries, barriers with shrubs (relative to those without) tend to be narrower, migrate landward more slowly, and have a greater proportion of subaerial volume distributed toward the ocean‐side of the barrier. Shrubs also tend to increase the likelihood of discontinuous barrier retreat, a behavior in which a barrier oscillates between periods of transgression and relative immobility, because shrubs induce prolonged periods of barrier immobility by obstructing overwash flow. However, shrubs can increase barrier vulnerability to drowning by preventing periods of transgression needed to maintain barrier elevation relative to rising sea levels. Additionally, physical barrier processes influence shrub expansion in our simulations; we find that greater dune erosion and overwash disturbance tends to slow the rate of shrub expansion across the barrier interior. Complementing recent observational studies of barrier islands in Virginia, USA, our results suggest that interior ecology can be a key component of barrier evolution on annual to centurial timescales.

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Non‐linear Shift from Grassland to Shrubland in Temperate Barrier Islands

Cited by 6 publications

References 49 publications

Interaction of seed dispersal and environmental filtering affects woody encroachment patterns in coastal grassland

Interaction of seed dispersal and environmental filtering affects woody encroachment patterns in coastal grassland

Seasonal facilitative and competitive trade‐offs between shrub seedlings and coastal grasses

Exploring the Impacts of Shrub‐Overwash Feedbacks in Coastal Barrier Systems With an Ecological‐Morphological Model

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