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Inundation and precipitation effects on growth and flowering of the high marsh species Juncus gerardii
Citation:
Watson, Elizabeth B., C. Wigand, M. Cencer, AND K. Blount. Inundation and precipitation effects on growth and flowering of the high marsh species Juncus gerardii. AQUATIC BOTANY. Elsevier Science Ltd, New York, NY, 121:52-56, (2015).
Impact/Purpose:
Multiple anthropogenic impacts threaten marsh survival, including coastal development, high nutrient loads, altered precipitation patterns associated with climate change and increased inundation associated with accelerated sea level rise. In this study, we examined effects of inundation and precipitation on growth of the high marsh species, Juncus gerardii.
Description:
Juncus gerardii Loisel., black needle rush, is a high latitude cosmopolitan plant species and, within salt marshes of the mid-Atlantic and New England coasts, occupies a narrow belt along the marsh-upland border. Examination of historic aerial photography, vegetation resurveys, and peat composition analysis for Northeastern marshes have shown vegetation change patterns indicative of increased inundation, including decline of J. gerardii. To help interpret loss patterns for J. gerardii in southern New England, we conducted an experiment to establish its sensitivity to varying inundation levels using laboratory mesocosms. Precipitation was also varied to determine sensitivity to drought, a stressor associated with short-term salt marsh die-off events. A strong relationship was found between inundation and productivity for J. gerardii, which together with marsh elevation and water level data, suggest that growth is reduced by current flooding patterns. Examination of J. gerardii flowering patterns also indicate that floret and inflorescence density vary with inundation, suggesting that negative impacts of sea level rise on Juncus may extend to seed production. Late spring and summer drought impacted neither J. gerardii growth nor its flowering, implying that J. gerardii is insensitive to precipitation during this season. We conclude that current inundation patterns are incompatible with robust growth for J. gerardii, and that conservation of Juncus habitat should include opportunities for upslope migration.
