We used historical documents, stand mapping, and new methods of dendrochronological analysis to reconstruct 250 y of land-use history of the Simes Tract in Petersham, MA. These data were then used to interpret the origin of the current forest's stand structure within the experimental plots of the Harvard Forest Hemlock Removal Experiment within the Simes Tract, an experiment that examines the effects of the ongoing decline of Tsuga canadensis on forest ecology. Data from tree cores revealed that the trees in the experimental plots were < 150 y old. These trees have established continually since the 1870s, with recruitment pulses following successive episodes of land division and re-aggregation, logging, irruptions of nonnative insects and pathogens, two moderate droughts, and the 1938 “Great Hurricane”. Our new method of dendrochronological analysis used generalized additive models and focused on year-to-year dynamics to highlight associations between fine-scale changes in tree growth, and both episodic (pulse) and longer-term environmental and biotic drivers. Tsuga canadensis, hypothesized to be a foundation species in this system, achieved its current dominance at the Simes Tract by responding rapidly, both positively and uniformly across age classes, in the 1920s to three concomitant environmental changes that had occurred in the preceding two decades: loss of Castanea dentata to the chestnut blight; selective logging; and a ∼ 7 y drought. In contrast, Betula lenta, Quercus rubra, Acer rubrum, and Pinus strobus have declined in importance since the early 1900s in stands otherwise dominated by T. canadensis. Acer rubrum and P. strobus were selectively harvested or severely damaged by the 1938 hurricane, the peak of B. lenta establishment followed the 1938 hurricane, and Q. rubra growth was impacted by the severe 1981 gypsy moth outbreak. Together, the data illustrate the contingent nature of the establishment dynamics of a foundation species in a New England forest and suggest a more nuanced approach to the role of T. canadensis as a foundation species.

Flora Conservanda is a list of native plant taxa considered to be most rare in New England. Originally published in 1996, the list was updated in 2012. The updated list includes 593 taxa in five divisions: 62 in Division 1 (Globally Rare), 325 in Divisions 2 and 2(a) (Regionally Rare), 57 in Division 3 (Locally Rare), 96 in Division 4 (Regionally Historic), and 53 in Division IND. (Presumed Rare, but confirmation required). Since the first publication of the list, substantial changes have occurred both in the landscape and in our understanding of the taxa. Here, we compare the 2012 update to the original list, noting changes in the species assigned to each division and recording the reported number of extant populations (Element Occurences) in each state. We assessed trends in rarity during the intervening 15 years among 676 taxa in one or both lists, and identified further data collection that would be beneficial. One hundred and thirty-seven taxa were new to the list in 2012. The numbers of reported extant occurrences increased for 118 taxa and declined for 40 taxa since the 1996 publication; 10 taxa declined in one or more states and increased in others. Little net change in occurrence numbers was seen for 213 taxa, and trend data were insufficient to assess population trends for 295 taxa. Massachusetts (55 or 18.4% of MA listed taxa), Connecticut (55 or 18.4%), and Maine (46 or 16.9%) had the most taxa with increased numbers of occurrences, and Massachusetts (22 or 7.7%), Maine (20 or 8.3%), and New Hampshire (17 or 8.4%) had the most taxa with decreased occurrence numbers. Increased occurrence numbers were more common among those taxa characteristic of shores and banks, wetlands, and forests, whereas higher proportions of declining species were characteristic of coastal, alpine, and exposed rocky areas. A significantly higher proportion of entomophilous species showed occurrence declines than increases. Overall, the magnitude and distribution of noted changes may be due to the success of concerted efforts to seek out previously overlooked populations, range expansions of certain taxa, or validation of older records. Trends apparent in the Flora Conservanda data can be used to prioritize regional conservation actions and data collection.