Research on Rubus occidentalis (black raspberry or blackcap) has recently intensified due to the health benefits of its fruits, its potential as a crop, and its aggressive growth in certain sensitive environments. However, the conditions in the wild in which stands of the species best persist and fruit are currently unknown. I measured light, soil pH, soil organic matter, soil fine particle fraction, and soil nitrogen in 49 R. occidentalis stands in southeastern Michigan and, using generalized linear and general mixed-effects models, examined whether these environmental factors were correlated with measures of reproductive success. Rubus occidentalis stands generally grew in moderate to low incident light and in neutral to mildly acidic (pH ∼5–7.5), coarsely textured soils with average to low levels of organic matter and inorganic nitrogen. Stands had a significantly higher proportion of successfully fruiting canes as light and soil pH increased and as organic matter decreased. Stands also had significantly more fruit receptacles and fruits per cane as light, ammonium, and pH increased. Significantly greater premature cane dieback during the fruiting season was observed as organic matter, nitrate, and soil pH increased and as soil texture became finer. Wild R. occidentalis appears to persist well in low-light environments with coarse, neutral, organic matter-poor soils, but it may achieve higher fruiting success in higher light environments with finer and more ammonium-rich soils. This study is the first to quantitatively assess the degree to which environmental context influences stand persistence and reproductive success for R. occidentalis in the wild.

Variation in fruit characteristics is frequently studied through the lens of frugivore preferences, but it may also be driven by the abiotic environment. Research on the reproductive ecophysiology of Rubus occidentalis (blackcap or black raspberry) is timely because of increasing interest in its antioxidant-rich fruits. Forty-nine R. occidentalis stands in southeastern Michigan were surveyed to 1) quantify variation in fruit characteristics in wild populations and 2) test for correlations between fruit characteristics and light and soil conditions. All fruit characteristics showed variation that strongly correlated with abiotic factors. Yield increased with increasing light, soil pH, and soil ammonium, and fruit fresh mass was positively related to light, soil fine particle fraction, and soil nitrate. Adjusting these factors may improve commercial yield and fruit quality for this species. Fruit water mass and water fraction were also higher in finer, more nitrate-rich soils. On the other hand, fruit dry mass increased with increasing light, implying that increased light availability may lead to better seed filling and better production of fruit solids. Fruit diameter was positively related to soil pH, soil fine particle fraction, and soil nitrate, and fruits had higher mass-to-diameter ratios in environments with higher light and in soils with lower organic matter content and loamier texture. Further study of the reproductive ecophysiology of R. occidentalis is clearly warranted.

Metal-contaminated soils provide numerous stressors to plant life, resulting in unique plant communities worldwide. The current study focuses on the vascular plants of Callahan Mine in Brooksville, ME, USA, a Superfund site contaminated with Cu, Zn, Pb, and other pollutants. One hundred and fifty-five taxa belonging to 50 families were identified, with the Asteraceae (21%), Poaceae (11%), and Rosaceae (9%) as the most species-rich families. Ninety-six species encountered at the Mine were native to North America (62%), including 11 taxa (7%) with rarity status in at least one New England state. Fifty-one species were non-native (33%), including nine taxa (6%) considered invasive in at least one New England state. We characterized how the plant community changed across different habitats at the Mine, from disturbed and exposed (waste rock piles, tailings pond) to inundated and relatively undisturbed (wetland, shore), and documented concurrent shifts in the ionic content of the soils across the habitats. We found substantial differences in both the plant community and soil chemical features among habitats. Habitats separated out along a single axis of an ordination of the plant community, with wetland and shore habitats at one extreme and tailings pond and waste rock-pile habitats at the other. The first principal component axis of the 21 soil variables was significantly predicted by the ordination of the plant community, indicating a gradient of increasing organic matter, Fe, Mg, Mn, total N, Na, and K roughly parallel to the gradient of increasing wetland vegetation. None of the plant species tested accumulated substantial concentrations of metals in their leaf tissue except Salix bebbiana and Populus balsamifera, which accumulated 1070 ppm and 969 ppm Zn in dry leaf tissue, respectively—approximately one-third of the concentration considered as hyperaccumulation for Zn.

Geochemistry and mineralogy of rocks play important roles in the occurrence of individual lichen species and assembly of lichen communities. Whereas lichens of metal-enriched settings have been a focus of study for many decades, only a few such lichen inventories exist for North America. We reexamined the lichen biota of Pine Hill, a serpentine outcrop on Little Deer Isle, Maine and Callahan Mine, a copper- and zinc-enriched Superfund site in Brooksville, Maine, by conducting additional field surveys and reexamining unidentified taxa from previous collections. To better characterize the substrates upon which the lichens were found, we conducted elemental analyses via x-ray fluorescence and inductively coupled plasma-mass spectrometry on rock samples collected at Pine Hill and recorded pH, electrical conductivity, and elemental concentrations via inductively coupled plasma mass spectrometry on soil samples from Callahan Mine. The re-investigation of lichens of the two metal-enriched sites resulted in the addition of 20 taxa to Pine Hill and 10 taxa to Callahan Mine. These include Dermatocarpon leptophyllodes, Placynthiella hyporhoda, Pyrenocarpon thelostomum, and Vezdaea acicularis, all recorded for the first time from New England. In addition, we report the first documented records since the late 19th to early 20th century for New England of Porocyphus coccodes, Sarcosagium campestre, and Steinia geophana, and the first such record for Maine for Coccocarpia palmicola. Stereocaulon condensatum and S. subcoralloides, both considered rare in New England, were also collected from Callahan Mine.