Distribution, species composition and management implications of seed banks in southern New England coastal plain ponds

Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Biological Conservation 142 (2009): 1350-1361, doi:10.1016/j.biocon.2009.01.020.Buried seeds that germinate during periods of low water or water level drawdown can play important roles in shaping plant community composition, community dynamics and species richness in ecosystems with fluctuating water levels. Northeastern US coastal plain ponds have fluctuating water levels and contain a characteristic shoreline flora that contains many rare plants. The objectives of this study were to: (1) test whether geographically distant ponds in Cape Cod and Martha’s Vineyard had distinct seed banks, (2) determine if hydrologic status as permanent and ephemeral ponds led to differences in seed banks, and (3) examine seed diversity and seed abundance across gradients of shoreline elevations and sediment characteristics. Viable seeds of 45 plant species were identified from 9 ponds. Native species dominated pond-shore seed banks and made up 89 to 100% of all species. There was high overlap in seed bank composition across hydrological classes and geographic regions. One hydrological class captured 73-76% of total species and one geographical region captured 69-78% of the total species recovered from the entire suite of seed bank samples. Seeds were relatively evenly distributed along the shorelines of ephemeral ponds but seed diversity and abundance were lower at low elevations in permanent ponds. Results suggest that strategies to protect pond shorelines to capture maximum diversity of coastal plain pond plants contained in pond sediment seed banks should be implemented across pond hydrologic classes and across a wide geographic area. Shoreline seed distributions indicate that ground-water withdrawals or climate changes that lower pond water levels in permanent ponds will reduce the diversity and abundance of plants recovered from seed banks by shifting water levels to a shoreline zone of high sediment organic matter where seed densities are lower. This effect will be much less in ephemeral ponds where seed diversity and abundance on pond bottoms was high.This study was funded by the Massachusetts Environmental Trust and the Barnstable Water Company

SUGARCANE AGRICULTURE AS AN AGENT OF GEOMORPHIC CHANGE AND STREAM DEGRADATION IN BRAZIL

Intensive agriculture profoundly alters the geomorphology, hydrology and nutrient balances of catchments. The result is the degradation of headwater stream ecosystems via inputs of excess sediments, surface runoff, and nutrients. To mitigate the negative effects on streams, watershed managers can implement riparian buffers, which are designed to intercept, process, store, and remove excess material from upslope agricultural source areas. While extensive research on those topics exists for temperate regions of developed countries, little is known in tropical regions of developing countries. To address this knowledge gap, I investigated the effects of sugarcane agriculture on catchment geomorphology and headwater stream ecosystems in Brazil. I studied 11 first and second order catchments spanning a sugarcane-forest gradient near Piracicaba, SP, to answer three main questions. (1) Is sugarcane agriculture an important agent of geomorphological change via gully formation? (2) Does gully formation influence the effectiveness of riparian buffers while increasing the stream response to storm events, and the amount of sediment in high flows? (3) Can land cover history in terms of sugarcane, and forest cover explain the variability in stream nutrient (nitrogen and phosphorus) concentrations? The overall results suggest that sugarcane agriculture is a driver of geomorphic alteration via gully formation in small order catchments in Brazil. Gullies act as effective conduits of surface runoff from upslope source areas to streams, increasing the magnitude of the stream’s response to storms and the amount of sediment transported in high flows. Consequently, gully formation may overwhelm any protective role played by riparian buffers. Sugarcane agriculture also increases stream nutrient concentrations to a point rarely recorded for streams draining intensive cropping in Brazil. However, there is little evidence that forested riparian buffers significantly mitigates the extent to which sugarcane agriculture affects stream nutrient concentrations. Additional policies to the restoration of riparian forests are needed to effectively protect headwater streams in Brazil