Evaluating the success of seed sowing in a New England grassland

Grassland habitat is declining in the northeastern United States, leading to a decline in associated native species. Consequently, there is considerable interest by land managers in conserving and restoring grassland habitats in the Northeast. However, unlike the Great Plains and Europe, quantitative monitoring of restoration sites is uncommon, making it difficult to improve new restoration projects. Here we evaluate a grassland restoration in Waterford, Connecticut to determine if mechanical clearing of woody vegetation combined with sowing 23 native grasses and forbs led to successful establishment of these species. We also compared cover, diversity, and colonization by exotic and woody species in planted and unplanted areas over time. In the third and fifth growing seasons after planting in 2006, we sampled the vegetation in the planted site, an unplanted zone within the planted grassland, and an adjacent unplanted grassland. Twenty of the 23 sown species established by 2010, and sown species dominated the planted area (70% of total cover). Despite the successful establishment of most sown species, species richness and diversity were no higher in the sown grassland than in adjacent unseeded areas. However, the sown grassland contained lower cover of non-native and invasive species. Big bluestem (Andropogon gerardii Vitman) established aggressively, potentially reducing both exotic colonization and native diversity. This study shows that sowing native grassland species can lead to the successful development of native-dominated grasslands. Results can inform future grassland restoration efforts in the Northeast and show that seeding with aggressive grass species may greatly impact restored plant communities

Vegetation patch dynamics in freshwater tidal wetlands

This study investigates causes of the mosaic pattern of vegetation occurring in freshwater tidal wetlands of the Connecticut River using the concept of patch dynamics. I examined: (1) the extent of the vegetation mosaic accounted for by floristic composition and geographic site differences; (2) differential site availability for seasonal colonization along complex hydrologic gradients of flood stress and flood disturbance, and suitability of experimental gap conditions to seasonal regeneration; (3) differential species availability for seasonal regeneration from the seed and bud bank; and (4) differential species performance of colonists from the seed and bud bank as alternate modes of regeneration with respect to complex hydrological gradients.^ The vegetation mosaic attributed to plant community structure and geographic sites accounted for 51% and 19%, respectively, of the total floristic variation. Accordingly, the representation of vegetation types was not the same among geographic sites. Differential site availability for colonization into seasonal gaps or bare space varied directly with increasing flood stress and flood disturbance. Differential species availability, based on an inventory of 68 species present in the vegetation of the preceding year, consisted of 72 species emerging from the seed bank and 30 species emerging from the bud bank, of which 21 species were shared. Differential species performance resulted from a trade-off between alternate modes of regeneration. Seasonal regeneration from both buds and seeds diminished with increasing levels of flood stress, yet unlike the bud bank, the seed bank responded positively to flood disturbance. Confirmed experimentally, the trade-off between seeds and buds is most pronounced under more severe gap conditions. However, upon disturbance in sites ordinarily less disturbed, regeneration from buds exceeded seeds.^ In general, hydrologic gradients accounted for the vegetation mosaic by determining which species, mode of regeneration, and range of response are the most appropriate for local persistence. However, under benign conditions of minimal flood stress and flood disturbance, the actual vegetation mosaic consisted of multiple, alternate, asuccessional vegetation types. The implications for conservation suggest re-examining traditional object-oriented practices in favor of preserving the ecological processes of the Connecticut River tidelands ecosystem.

Aquatic vegetation and trophic condition of Cape Cod (Massachusetts, U.S.A.) kettle ponds

The species composition and relative abundance of aquatic macrophytes was evaluated in five Cape Cod, Massachusetts, freshwater kettle ponds, representing a range of trophic conditions from oligotrophic to eutrophic. At each pond, aquatic vegetation and environmental variables (slope, water depth, sediment bulk density, sediment grain size, sediment organic content and porewater inorganic nutrients) were measured along five transects extending perpendicular to the shoreline from the upland border into the pond. Based on a variety of multivariate methods, including Detrended Correspondence Analysis (DCA), an indirect gradient analysis technique, and Canonical Correspondence Analysis (CCA), a direct gradient approach, it was determined that the eutrophic Herring Pond was dominated by floating aquatic vegetation (Brasenia schreberi, Nymphoides cordata, Nymphaea odorata), and the algal stonewort, Nitella. Partial CCA suggested that high porewater PO4-P concentrations and fine-grained sediments strongly influenced the vegetation of this eutrophic pond. In contrast, vegetation of the oligotrophic Duck Pond was sparse, contained no floating aquatics, and was dominated by emergent plants. Low porewater nutrients, low sediment organic content, high water clarity and low pH (4.8) best defined the environmental characteristics of this oligotrophic pond. Gull Pond, with inorganic nitrogen-enriched sediments, also exhibited a flora quite different from the oligotrophic Duck Pond. The species composition and relative abundance of aquatic macrophytes provide good indicators of the trophic status of freshwater ponds and should be incorporated into long-term monitoring programs aimed at detecting responses to anthropogenically-derived nutrient loading