Factors at Multiple Scales Influence Recruitment from Herbaceous Wetland Seed Banks in the Lower Mississippi Alluvial Valley

摘要

In early successional stages, seedlings serve as a link between past and future wetland plant assemblages. Our objectives were to 1) enumerate seedling density in soil exposed to various hydrologic treatments 2) determine similarities between standing vegetation, germinated seedlings, and early successional stage assemblages, and 3) better understand effects of landscape-level factors on overall wetland seedling density. Soil samples were collected and standing vegetation characterized from 12 restored and three non-managed wetlands in the Mississippi River Alluvial Valley (MAV). Seedling germination was observed in a greenhouse experiment, while early-stage plant assembly was followed in outdoor mesocosms. Hydrology significantly affected seedling density, with constantly moist treatments increasing seedling germination above that observed in fluctuating or continually inundated treatments. Standing vegetation in MAV wetlands differed from germinated seedlings; however, germinated seedlings were similar in terms of structure and identity to early successional mesocosm assemblages, indicating close linkages of these two vegetation stages. When landscape-level factors were examined, we found that wetland size was positively correlated, and surrounding land use and watershed nitrogen (N) loading negatively correlated with seedling numbers. Thus, seedling dynamics were affected by factors internal and external to wetlands, necessitating landscape-scale perspectives when making management decisions, even for individual wetlands.