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Woody plant encroachment is infuenced by interactions between the physical environment and vegetation, which create heterogenous microenvironments some of which favor shrub recruitment through mitigation of the abiotic environment. Encroachment of native shrub, Morella cerifera into grasslands on Hog Island, Virginia has been attributed to warmer winter temperature; however, recruitment of seedlings in grasslands may be impacted by multiple factors at the level of the microhabitat. Our study focuses on a critical gap in understanding factors specifcally infuencing M. cerifera seedling recruitment and survival. By experimentally planting M. cerifera seedlings at varying dune elevations and grass densities, we tested hypotheses that dune elevation infuences the microclimate, soil characteristics and vegetation cover and that grass cover/density is related to shrub establishment. We tested these hypotheses through gathering data from temperature data loggers, conducting soil water content and chloride analyses, and determining percent cover of grasses relative to dune elevation. Results indicate that dune elevation was positively related to moderated temperatures with reduced temperature extremes and vegetation cover/composition that led to favorable locations for M. cerifera establishment and growth. Where dune elevation is>2 m, we document an upper limit of grass cover on natural seedling establishment, suggesting a switch from facilitative to competitive efects with grass density. Overall, our work demonstrates interactions between dune elevation and medium grass density has a facilitative infuence on M. cerifera establishment and can be used for future predictions of shrub growth with rising sea-levels.
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Elevation, canopy cover and grass cover structure patterns of seedling establishment in a subtropical post‐fire restoration
Abstract Ecological restoration is beneficial to ecological communities in this era of large‐scale landscape change and ecological disruption. However, restoration outcomes are notoriously variable, which makes fine‐scale decision‐making challenging. This is true for restoration efforts that follow large fires, which are increasingly common as the climate changes.Post‐fire restoration efforts, like tree planting and seeding have shown mixed success, though the causes of the variation in restoration outcomes remain unclear. Abiotic factors such as elevation and fire severity, as well as biotic factors, such as residual canopy cover and abundance of competitive understorey grasses, can vary across a burned area and may all influence the success of restoration efforts to re‐establish trees following forest fires.We examined the effect of these factors on the early seedling establishment of a tree species—māmane (Sophora chrysophylla)—in a subtropical montane woodland in Hawaiʻi. Following a human‐caused wildfire, we sowed seeds of māmane as part of a restoration effort. We co‐designed a project to examine māmane seedling establishment.We found that elevation was of overriding importance, structuring total levels of plant establishment, with fewer seedlings establishing at higher elevations. Residual canopy cover was positively correlated with seedling establishment, while cover by invasive, competitive understorey grasses very weakly positively correlated with increased seedling establishment.Our results point to specific factors structuring plant establishment following a large fire and suggest additional targeted restoration actions within this subtropical system. For example, if greater native woody recruitment is a management goal, then actions could include targeted seed placement at lower elevations where establishment is more likely, increased seeding densities at high elevation where recruitment rates are lower, and/or invasive grass removal prior to seeding. Such actions may result in faster native ecosystem recovery, which is a goal of local land managers.
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- PAR ID:
- 10470553
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecological Solutions and Evidence
- Volume:
- 4
- Issue:
- 4
- ISSN:
- 2688-8319
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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