Species composition in the seedbank of abandoned cranberry farms: From a restoration perspective

Background/Question/Methods The long history of cranberry (Vaccinium macrocarpon) cultivation has left numerous abandoned cranberry farms in the Pine Barrens of New Jersey. The 3,600 acres of currently active cranberry farms are also under a constant state of flux (farm construction and abandonment). Restoration of some abandoned areas into suitable habitat for the Pine Barrens’ flora and fauna is now being planned. My research aimed to explore the seed availability in abandoned cranberry farms and the impact of environmental conditions on their germination.
In May-October 2007, I collected soil from different depths in abandoned bogs and measured seedbank germination under various greenhouse conditions. Soil cores were collected from 8 cranberry bogs with high (wet bog) or low (dry bog) water table. In one wet bog, cores were taken from along the edge and in the center. Each core was divided into three segments: the bottom was the original wetland soil formed before the farm construction; the middle was formed during cultivation when cranberry farmers routinely added sand onto the bog surface; and the top layer represents the most recent surface with recent propagule inputs from the surrounding habitat. In the greenhouse, two of the cores from each bog were germinated under “non-flooding treatment” (trays were watered regularly by mist bench), while the other two were under “flooding treatment” (trays were completely inundated every other week in addition to regular watering). The results were examined by two three way ANOVAs: location (edge/middle) * treatment (wet/dry) * layer (top/middle/bottom) and hydrology (dry/wet)* treatment * layer.

Results/Conclusions Eighteen species were identified after 4 months. The total number of species (p=0.0047) and individuals (p=0.0482) are both significantly higher on the bog edge than the center. The non-flooding treatment resulted in a slightly higher (p=0.051) number of individuals than the flooding treatment. Bog hydrology had significant interaction with the soil layer (p=0.0133): the top layer in dry bog had the highest species diversity, while the bottom layer of dry bogs had very few species. Some typical upland species germinated dominantly from the top layer (Viola lanceolata, Hypericum gentianoides, and Rhexia virginica), while some wetland species (Cyperus retrosus, Eleocharis flavescens, and Hypericum spp.) had much higher germination from the middle or bottom layer. The result demonstrated soil from the deeper layers of the farm has the potential to provide seed sources for restoration, but different bog conditions and location will result in different species composition.