Old-growth forests often represent an important natural benchmark for evaluating the effects of management and changing environmental conditions on forest and ecological dynamics. In regions with a history of extensive land use, such as New England, there is limited opportunity to develop such information, given that only a few old-growth forests remain scattered across a finite portion of the landscape. This study takes advantage of a unique historic data set collected across 250 ha of old-growth forest, within a larger area (2,000 ha), in southern New Hampshire in 1929–30, to characterize natural forest composition, live-tree size distributions, recruitment history, and aboveground biomass conditions across six common regional forest types. Forest composition ranged from areas dominated by Pinus strobus L. and Tsuga canadensis (L.) Carrière to mixed hardwood forests composed of Fagus grandifolia Ehrh., Betula lenta L., and Betula papyrifera Marshall, and Acer saccharum Marshall. Across forest types, smaller diameter classes were composed primarily of shade-tolerant species, namely T. canadensis and F. grandifolia, whereas larger size classes consisted of P. strobus and T. canadensis, with the largest size class composed of P. strobus exclusively. Age data collected from these forests reflected largely multicohort conditions, with the largest peaks in recruitment documented between the mid-1600s and mid-1700s. Biomass values were positively correlated with stem density, and stratified forests containing high densities of smaller diameter T. canadensis in both the understory and midstory as well as P. strobus in the overstory tended to have the highest basal area and a greater number of trees within the largest diameter classes (≥ 89 cm). Forests with high basal area densities of large P. strobus (≥ 51 cm) had the greatest biomass values. In these sites, understory T. canadensis stem density was relatively high, likely suggesting that the stratification of both species accounted for the high biomass values; however, the presence of large-diameter P. strobus was most important to generating those high biomass totals. The wide range of composition and structure observed across this landscape likely reflects the historic importance of variability in disturbance processes and site conditions in maintaining a mosaic of forest compositional and structural conditions and may serve as a reference for restoration and conservation activities in areas heavily affected by past land use. Moreover, the disproportionate influence of P. strobus on aboveground biomass conditions in areas in which it historically predominated highlights the unique potential of this species for use in regional mitigation strategies.

During foraging, moose break stems of numerous saplings in order to lower shoot tips to a height they can reach. Both stem-breaking and bedding occur throughout the range of moose and these behaviors together create disturbed patches, which increase habitat heterogeneity forest-wide. Here, we explore this phenomenon in two ways: a case study in which we quantify the size of moose beds and evaluate the physical and taxonomic extent of stem breaking for more than 300 broken trees at seven sites in western Massachusetts and Connecticut, and a literature review on stem-breaking. In our case study, moose broke the stems of 17 deciduous woody species and were twice as likely to snap main stems rather than lateral stems. After breaking a stem, moose browsed shoot tips 96% of the time. Moose snapped primarily shade-intolerant or intermediately tolerant species (92%); the frequency of broken shade-intolerant trees was 2–4 times greater than the frequency of their occurrence in the stand, and the only shade-tolerant species moose broke were shrubs or understory tree species. We measured the 10 moose beds that we encountered; they ranged in size from 1.5–3.4 m² (mean = 2.5 m²). We performed a systematic review of stem breaking by moose throughout their range and found 14 publications that characterized stem-breaking by moose in Europe and North America. These studies typically focused on a few tree species of economic importance, on how stem-breaking increased forage access to the tips of broken trees, or how moose damage in general redirected or delayed succession. The one report of stem-breaking across all species found 1% of all trees were broken, while as many as 60% of individuals of preferred species were broken at sites in both North America and Europe. Stem-breaking contributes to keeping some forest stands in an earlier stage of succession, and bedding may create small patches of crushed vegetation that may enhance local plant diversity at small spatial scales. Thus, our findings and review support previous research that characterize moose as ecosystem engineers, keystone species, or both.

Seed dormancy is a trait that has evolved to maximize germination when environmental conditions are optimal for successful recruitment of new individuals into a population. Physical dormancy is one such trait common in legumes and release from this condition is often associated with disturbance events, such as fire. Changes to the specific conditions (e.g., climate, fire regimes) that release seeds from dormancy can have negative effects on populations, especially of rare species. Therefore, understanding the species-specific requirements needed to release seeds from dormancy and induce germination provides insight into ecological processes, effects of changing environmental conditions, and potential conservation actions. Amorpha georgiana (Fabaceae) is a rare subshrub with indehiscent fruits (pods) found in fire-maintained longleaf pine habitats in the southeastern United States. The germination ecology of this species is largely unknown. The goals of this study were to determine the presence of physically dormant seed in A. georgiana and then, through a series of laboratory-based experiments, resolve the fire related factors that effectively overcome dormancy and promote germination. The seeds of A. georgiana exhibit physical dormancy and show significantly higher germination after brief exposure to hot water (94 °C) compared to all other temperatures and treatments assessed. Regardless of treatment, seeds have low germination when retained in their pods, but the pod is not the cause of physical dormancy. We found enclosure within an indehiscent pod and exposure to pyrogenic temperatures (> 80 °C) both affect dormancy release and germination of A. georgiana. The 3.5-fold increase in germination at pyrogenic temperatures suggests the response is highly fire-adapted and fits the definition of obligate pyrogenic dormancy release. While season of fire exposure was not significant in our study, we did find consistent negative effects on the germination response. Our results suggest pulses of heat from periodic growing season fires are likely necessary to promote recruitment and maintain populations of this rare species.

Taxonomic circumscription is a critical prerequisite for ecological, taxonomic, and systematics research but can be complicated by undetected patterns in morphological variation. Cryptic variation has long confounded the taxonomy of Physocarpus (Cambess.) Raf., with conflicting circumscriptions especially prevalent in the Physocarpus opulifolius (L.) Maxim. complex, which comprises P. opulifolius sensu stricto and Physocarpus intermedius (Rydb.) C.K.Schneid. Here, we assess variation for carpel and follicle pubescence, a key diagnostic character for the P. opulifolius s.l. complex. Data were collected from 748 herbarium accessions obtained from across the range of this complex in North America. We then assessed the statistical and geographic distribution of this variation. As suggested by Rydberg and others, follicle pubescence is bimodally distributed and exhibits a strong geographic signal. An eastern, glabrous (or nearly so) form occurs in temperate forests from the St. Lawrence River valley of Quebec west to the Upper Great Lakes region and south to the southern Appalachians (i.e., P. opulifolius s.s.), while a more western, densely pubescent form occurs from the Interior Highlands north to the Driftless Area, with disjunct populations in the Southeastern Plains of Alabama, Sand Hills of Nebraska, Black Hills of South Dakota, Front Range of Colorado, and Sierra Madre Oriental of northeastern Mexico (i.e., P. intermedius). We conclude that taxonomic recognition is warranted based on variation in follicle pubescence, which also has implications for downstream research (e.g., floristics, phylogenetics, and ecological niche modeling).

Andromonoecy, a sexual system in which all individuals have both bisexual and male flowers, is found in at least four North American genera of Cleomaceae: Cleome L., Cleomella DC., Polanisia Raf., and Tarenaya Raf. This can be easily missed because the terms andromonoecious and andromonoecy are largely absent from the literature on these taxa. We conducted a series of experiments on how fruit set, mineral nutrition, mating, and herbivory affect male flower production in a cultivar of the North American cleomid Polanisia dodecandra (L.) DC. subsp. trachysperma (Torr. & A. Gray) Iltis. When we completely prevented fruit set during bisexual flower production, no male flowers were produced. If we allowed fruit maturation, plants would eventually switch to producing male flowers, then switch back to bisexual, and then continue alternating floral sex types as long as we allowed them to grow. Withholding mineral nutrients and simulating leaf herbivory each hastened the initial switch from bisexual to male flowers, but self-pollination did not delay it. Our results strongly indicate that in P. dodecandra subsp. trachysperma, male flower production is an evolutionary response to the regular occurrence of variation during the flowering season in the availability of photosynthates necessary for fruit maturation. It is likely that male flowers do contribute to male reproductive success through increased pollen export, but do not contribute to female reproductive success through increased deposition of pollen on the stigmas of bisexual flowers. More complete knowledge of the sexual systems and infrageneric relationships among North American cleomids, and in Cleomaceae as a whole, should provide interesting new insights into the evolution of sexual systems in angiosperms.

The New Jersey Pine Barrens (Pinelands) is the primary resource for the identification of many of the Zygnematophyceae described in the United States by Francis Wolle and published in early volumes of the Bulletin of the Torrey Botanical Club. Based on the current study, more than 1,100 algal species and infraspecific taxa exist in the Pinelands, which is more than all the other algal studies for the Pinelands combined. This report lists 545 Zygnematophyceae taxa plus 15 genus species. From this list, there are 316 taxa newly reported from 90 current sites within 17 New Jersey Pinelands watersheds.

The geographical range of the species now known as Houstonia micrantha has been uncertain, in part because of taxonomic confusion with its sister species, Houstonia pusilla. Previously believed to be restricted to two counties in eastern and central Georgia, it is now apparent that this homostylous winter annual is much more widespread. In fact, its recent spread and its enormous potential to multiply and invade disturbed sites suggest that it may spread to many states far to the east and north of its original range. This species has probably been overlooked as it has spread to new areas because it is small and has inconspicuous flowers compared with most species of Houstonia and completes its life cycle in a very short period of time early in the spring.