AimsRecreational use on mountain summits has caused severe degradation of soils and vegetation, and climate change is exacerbating these impacts. Best practices for restoration of these important ecosystems are unknown. Here, we examine the effectiveness of different treatments for restoring native vegetation (plant cover and native species richness) in degraded areas on a mountain summit through an experimental restoration approach.LocationCadillac Mountain, Acadia National Park, Maine, USA.MethodsWe tested six restoration-method treatments: control, planting modules, coir erosion control, seed and coir, soil and coir, and soil, seed, and coir. We established four replicates of each restoration-method treatment in 2016 and monitored percent cover and species richness twice per year from 2017 to 2022. In 2017, we established four more plots for each of three soil-depth treatments (2.5 cm soil, seed, and coir, 13 cm soil and coir, and 13 cm soil, seed, and coir) and monitored percent cover.ResultsSix years after restoration began, native vegetation cover was highest in treatments with added soil. Seeding (502 seeds/m2) had no effect on percent cover. Planting seedlings added vegetative cover initially, but did not increase over time. Cover was equally high in treatments with shallow soil (2.5 cm deep) and deep soil (13 cm deep). Treatments with added soil also had the highest native species richness. Adding a small amount of soil (2.5 cm soil depth) with erosion control (i.e., coir matting) successfully restored vegetation to previously degraded areas of the Cadillac Mountain summit.ConclusionsMountain ecosystems will continue to experience degradation from human recreation and climate change. Restoration of degraded areas is critical to maintain these rare ecosystems. Our results suggest that restoring and maintaining soil is key to restoring degraded areas. However, more research is needed to understand the long-term implications and success of mountain summit restoration. Our study provides an example of how this work can be done without delaying restoration using an experimental restoration approach.

The fundamental goal of a rare plant translocation is to create self-sustaining populations with the evolutionary resilience to persist in the long term. Yet, most plant translocation syntheses focus on a few factors influencing short-term benchmarks of success (e.g., survival and reproduction). Short-term benchmarks can be misleading when trying to infer future growth and viability because the factors that promote establishment may differ from those required for long-term persistence. We assembled a large (n = 275) and broadly representative data set of well-documented and monitored (7.9 years on average) at-risk plant translocations to identify the most important site attributes, management techniques, and species' traits for six life-cycle benchmarks and population metrics of translocation success. We used the random forest algorithm to quantify the relative importance of 29 predictor variables for each metric of success. Drivers of translocation outcomes varied across time frames and success metrics. Management techniques had the greatest relative influence on the attainment of life-cycle benchmarks and short-term population trends, whereas site attributes and species' traits were more important for population persistence and long-term trends. Specifically, large founder sizes increased the potential for reproduction and recruitment into the next generation, whereas declining habitat quality and the outplanting of species with low seed production led to increased extinction risks and a reduction in potential reproductive output in the long-term, respectively. We also detected novel interactions between some of the most important drivers, such as an increased probability of next-generation recruitment in species with greater seed production rates, but only when coupled with large founder sizes. Because most significant barriers to plant translocation success can be overcome by improving techniques or resolving site-level issues through early intervention and management, we suggest that by combining long-term monitoring with adaptive management, translocation programs can enhance the prospects of achieving long-term success.

Reintroductions are important components of conservation and recovery programs for rare plant species, but their long-term success rates are poorly understood. Previous reviews of plant reintroductions focused on short-term (e.g., ≤3 years) survival and flowering of founder individuals rather than on benchmarks of intergenerational persistence, such as seedling recruitment. However, short-term metrics may obscure outcomes because the unique demographic properties of reintroductions, including small size and unstable stage structure, could create lags in population growth. We used time-to-event analysis on a database of unusually well-monitored and long-term (4-28 years) reintroductions of 27 rare plant species to test whether life-history traits and population characteristics of reintroductions create time-lagged responses in seedling recruitment (i.e., recruitment time lags [RTLs]), an important benchmark of success and indicator of persistence in reintroduced populations. Recruitment time lags were highly variable among reintroductions, ranging from <1 to 17 years after installation. Recruitment patterns matched predictions from life-history theory with short-lived species (fast species) exhibiting consistently shorter and less variable RTLs than long-lived species (slow species). Long RTLs occurred in long-lived herbs, especially in grasslands, whereas short RTLs occurred in short-lived subtropical woody plants and annual herbs. Across plant life histories, as reproductive adult abundance increased, RTLs decreased. Highly variable RTLs were observed in species with multiple reintroduction events, suggesting local processes are just as important as life-history strategy in determining reintroduction outcomes. Time lags in restoration outcomes highlight the need to scale success benchmarks in reintroduction monitoring programs with plant life-history strategies and the unique demographic properties of restored populations. Drawing conclusions on the long-term success of plant reintroduction programs is premature given that demographic processes in species with slow life-histories take decades to unfold.

The consequences of initial variability in reproductive effort on later pollination and fruit development have frequently been investigated with flower removal experiments. Often, plants produce many fewer fruits than flowers, so flower removal might not be expected to alter subsequent growth or development patterns all that much. Yet, many studies have demonstrated such changes even for species with low average fruit set, which begs for an explanation. Many (at least seven, by our count) such explanations have been reported in the literature, but experimental support for most is limited. In summer 2014, we conducted a field experiment on a lowbush blueberry (Vaccinium angustifolium) farm in Maine. In this experiment, we coupled flower removal with three other treatments, each designed to assess the validity of one of three often-cited hypotheses invoked to explain why growth and development changes occur following flower removal: 1) “Short-term nutrient shortages;” 2) “spatiotemporal limitations;” and 3) “the compound interest effect.” The three respective treatments—foliar nitrogen fertilization, positionally biased flower removal, and defoliation—were designed to either intensify or weaken the apparent effects of flower removal if the corresponding hypothesis had merit. As in a 2013 preliminary experiment, flower removal elicited several statistically significant growth and development changes in blueberry, including increases in final leaf area, ripe fruit weight, fruit ripening rate, and relative fruit production. The additional treatments also elicited several significant plant responses, though not always with concomitant flower removal effects as well. For example, fertilization generally increased fruit cluster mass by harvest, but flower removal itself had no such effect on cluster mass. Most observed interactive effects between flower removal and the additional treatments either ran counter to expectations, were limited in scope, or couldn't be unambiguously interpreted. For at least a few observed changes, none of the additional treatments significantly altered the effects of flower removal. We conclude that current hypotheses for the mechanistic basis for changes induced by flower removal are inadequate, at least for blueberry, a species with frequently low fruit set even when managed commercially. However, strong intellectual and economic imperatives exist to encourage further investigation into this open question.Plants grown in horticulture or occurring as adventives outside their native range can provide insight into species’ fundamental niche requirements that might not be evident from the native range, or realized niche, alone. Such occurrences can also identify conditions that support individual survival, but do not currently sustain positive population growth (i.e., a species’ ‘tolerance niche’). Further, in the context of rapid climate change, horticultural and adventive occurrences beyond current range edges might circumvent natural dispersal limitations and facilitate species range shifts. To explore these concepts in the field, we investigated the history and structure of five newly discovered populations of naturalized Magnolia tripetala near horticultural sites in western Massachusetts, USA. This tree species is native to the southeastern US, but has been grown horticulturally in the Northeast since the 1800s. However, naturalized populations had not been well documented in the region previously, raising the possibility that the species’ escape has been triggered by recent climate change. With tree coring and life stage surveys, we asked whether the naturalized populations exhibited synchronous patterns of establishment and expansion, suggestive of climatic release and a shift from tolerance niche to fundamental niche conditions in the region. Across the five sites, we documented 660 individuals, with populations ranging in size from 46 to 396 individuals, including seedlings, saplings, and reproduct

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.

The New England Plant Conservation Program (NEPCoP) regional rare plant list, Flora Conservanda: New England, identifies higher vascular plant taxa (i.e., trilcolpates) in need of regional conservation. The first list, published in the Summer 1996 issue of Rhodora, identified 574 taxa in five divisions. As with the original publication, the data for this update were provided by the New England state Natural Heritage Programs (or equivalents). This update, completed in 2009-2012 by the New England Flora Committee of NEPCoP, is built on data as up-to-date as possible and is comprised of 593 taxa in five divisions: Division 1-Globally Rare Taxa (62 taxa); Divisions 2 and 2(a)-Regionally Rare Taxa (325); Division 3-Locally Rare Taxa (57); Division 4-Historic Taxa (96); and Division Indeterminate-Presumed Rare, but Confirmation Required (IND.; 53).

Isotria medeoloides (Small Whorled Pogonia) is a globally rare woodland orchid. Observed population declines in this species may be related to decreased light availability resulting from forest maturation. In East Alton, NH, a population of Small Whorled Pogonia was partitioned into two groups, with one left as a control and the other subjected to canopy-reduction management. The removal of all shrubs and 25% of the tree basal area approximately doubled light transmission to the managed group. The number of stems and seed capsules significantly increased in this group relative to tie control group. While this was not a replicated experiment, our observations suggest that canopy thinning may help promote the long-term conservation of this federally threatened species.

Because it is virtually impossible to collect seed or tissue for ex situ conservation banks from every known population of rare plant species, it is important to rank populations systematically in terms of their priority for collection. The New England Wild Flower Society, which maintains a regional seed bank, developed a set of three complementary decision matrices in spreadsheet form by which to prioritize all occurrences of all state-listed rare plant species in New England in terms of their urgency and feasibility for collection. Data on 4333 occurrences, spanning 456 taxa, were collated from six state Natural Heritage Programs. The first decision matrix ranked taxa in terms of their amenability to storage or propagation at ex situ institutions, and determined whether any known New England occurrences were reproductive. The second matrix further ranked taxa in terms of their global and regional rarity and the viability and genetic and geographic representation of collections already present in the bank. The third matrix scored individual occurrences within each taxon in terms of the presence of imminent threat, reproductive status, vigor, protection status, potential genetic distance from other occurrences, availability of landowner permission, and their current status in the bank. Occurrences were then sorted in ascending order by total matrix score; those with low scores were at the top of the list for collection priority. 3743 occurrences were deemed eligible for collection. Scores ranged from 14.5 to 182, and were influenced most strongly by the number of occurrences per taxon. Clear breakpoints were apparent in the distribution of scores, with clusters of uncommon taxa at the low end of the scale and a long tail created by taxa with more numerous occurrences in New England. These breakpoints could potentially be used to prioritize groups of occurrences that should receive the first attention for collection, while postponing collection of higher-scoring groups. Fewer than 1% of occurrences were misclassified, according to post hoc inspection. This simple set of decision matrices can be adapted by a wide range of institutions involved in ex situ conservation.