Merremia macrocalyx is a vine that grows over other plants or as a low creeper and is considered a weed of important crops. Study of its reproductive biology showed that its flowers comprise the typical features of the melittophilous pollination syndrome. Anthophoridae, Apidae, and Halictidae were its main floral visitors. Merremia macrocalyx showed a mixed mating system with features that promote outcrossing while allowing some autogamy. Floral biomass was allocated mainly to the corolla (attraction) which, together with the presence of herkogamy and protandry, favors out-crossing. Nevertheless, it is self-compatible and partially autogamous due to the position of anthers above the stigma. Foraging behavior of pollinators could also facilitate deposition of self pollen on the stigma. Ovule abortion was the main predispersal loss of potential seed production, closely followed by flower and fruit abortion. Predispersal seed predation and seed abortion were relatively low. Specimens of Megacerus flabelliger (Bruchidae) were found emerging from the seeds as well as some wasps belonging to families recognized as parasitoids. The mixed mating system showed by Merremia macroclayx, together with its pollination by generalist bees, provides advantages for its development as a weed.

Canebrakes were monodominant stands of bamboo once common in bottomlands throughout the southeastern U.S. They were habitat for many wildlife species, and have declined drastically since the 18^th century. Knowledge of the reproduction of canebrake bamboos is sparse and often contradictory. We studied reproduction and the role of disturbance in one canebrake bamboo, Arundinaria gigantea (Walt.) Muhl., at two field sites in Louisiana. We noted flowering with little or no seed-set during each of four years at our primary study site, and a mass-flowering event at a second site from which we collected 2,000 seeds. Of these, 82–95% proved viable in germination trials. We used these seeds in a 2 × 2 factorial design at the Buckhorn Wildlife Management Area in NE Louisiana to test the effects of prior windstorm and fire on seed germination and seedling survival. Results indicate that A. gigantea is capable of reproducing in the leaf litter and partial shade typical of open forest habitat but may have problems reproducing in burned-over areas with bare mineral soil. We identified three potential bottlenecks in the species' regeneration and proposed that successful outcrossing may drive synchronized flowering events in these and other bamboos. We presented implications for canebrake restoration efforts, plus several questions that might be examined by future studies.

We examined relationships involving the abundance of Carex pensylvanica Lam., a native sedge that can form dense mats in northern hardwood understories, and three types of disturbances: forest management, deer herbivory, and exotic earthworm activity. Stands managed using even-aged silvicultural systems in areas with high deer densities (> 20 deer km⁻²) had greater C. pensylvanica cover than stands managed using even-aged silvicultural systems in areas with lower deer densities (10–20 deer km⁻²), or unharvested second-growth communities. Stands managed using uneven-aged silvicultural systems were not significantly different from any other treatment group, regardless of deer density. There was a significant management × deer × earthworm interaction, and earthworm density had a positive relationship with C. pensylvanica cover in most management history × deer density combinations. High levels of disturbance associated with at least two of the three factors considered in this study were associated with high C. pensylvanica cover, but patterns across any single variable were inconsistent. These results elucidate the intricate nature of invasive plant dynamics, and provide a baseline for more detailed studies of the causal mechanisms underlying sedge mat formation in northern hardwood forests.

Despite the recognized importance of root sprout production in northern populations of American beech (Fagus grandifolia Ehrh.), further consideration of the relative role of regeneration from seed in this species appears warranted and timely. A careful examination of the literature revealed that seed- and sprouts-origin individuals co-occurred within all published study sites where the two were differentiated and that presence of a seedling bank may be the rule rather than the exception for American beech. We compared the effects of canopy gaps and root trenching on the growth and survival of a cohort of beech seedlings in Hubbard Brook Experimental Forest (HBEF) in northern New Hampshire, USA. Seedlings in gap plots became larger both above- and belowground. Foliar nitrogen concentrations were affected by both above- and belowground treatments and increased the most for seedlings in trenched gap plots. Seedling height and canopy treatment were important predictors of seedling survivorship with the highest survival in gap locations. The relationship between seedling height and survival was more complex. In the first two years, taller seedlings had a higher probability of dying, while after the second year taller seedlings were more likely to survive to be four-years old. The relatively high survivorship of seedlings at HBEF and their response to gap openings taken together with literature documentation of the long-term presence of seed-origin beech stems in the understory strongly suggest the presence of a beech seedling bank in this forest. This is one of a few manipulative studies on naturally regenerating American beech seedlings, and the first study to relate the likelihood of survival to seedling traits for this important species in the northern hardwood forest.

Recent studies have emphasized the importance of multiple and interacting disturbances in controlling plant community dynamics. However, detailed information on disturbance history and changes in species abundance are unavailable for many forest ecosystems. As a result, it is often difficult to evaluate the influence of disturbance interactions on changes in species composition over time. This study examines the history and dynamics of Fagus grandifolia-dominated forests in coastal New England to evaluate the role of multiple disturbances in the development of Fagus dominance. Detailed historical and dendroecological data were used to reconstruct disturbance history and compositional trends for the past > 300 years. At the time of European settlement, the study area supported mixed forests of Quercus, Fagus, Carya, and Pinus. Intensive harvesting in the early 19^th century resulted in abundant Quercus alba, Q. velutina, and Fagus regeneration. Thereafter, harvesting and fire were limited, but repeated low-moderate intensity hurricanes allowed Fagus but not Quercus species to establish and persist in the forest understory. A severe hurricane in 1944, accompanied by intense herbivory from a high deer population, accelerated the development of Fagus dominance by releasing Fagus saplings, initiating Fagus establishment, and preventing Quercus establishment. The extreme shade tolerance of Fagus, in combination with its flexible regeneration strategy (i.e., the ability to regenerate from seed or from root sprouts), and low palatability to deer, contributed to the increase in abundance of Fagus in response to this complex disturbance history. Thus, long-term changes in forest composition and reduced species richness resulted from species-specific responses to multiple, interacting disturbances.

When Hurricane Isabel reached the Virginia Coastal Plain on September 18, 2003, it was still a Category 2 hurricane, the strongest hurricane to hit Virginia for more than 70 years, and it inflicted much damage on forests. Permanent hardwood forest plots sampled just months before the storm were re-sampled after the event, revealing an overall damage rate of 14.9% of stems ≥ 2.5 cm dbh, with 7.3% of stems uprooted or secondarily crushed. Larger trees suffered more damage than smaller trees, ranging from 9.7% stems damaged for stems below 10 cm dbh (all by secondary damage) to 32.4% of stems over 60 cm dbh. In the larger size classes, red oaks (predominantly Quercus rubra, but including, Q. falcata, Q. coccinea, Q. velutina) suffered more damage than white oak (Quercus alba). Liriodendron tulipifera and Fagus grandifolia suffered even less damage, but both species lost many branches in an ice storm in 1998, and may have had smaller crowns with less wind resistance than the canopy oaks. There was no significant difference among species in amount of (secondary) damage to smaller trees, although Nyssa sylvatica had a particularly low percent damage. Overall 16% of basal area was lost, but damage was patchily distributed. No basal area was lost in nine of 27 plots, but more than 30% of basal area was lost in seven plots. Loss of large trees created numerous canopy gaps that will no doubt change the forest dynamics in years to come.

On September 2, 2004 Hurricane Frances (Category 3) passed directly over San Salvador Island, The Bahamas. This event offered the opportunity to gather baseline data regarding the impact of hurricanes on populations of the invasive Australian pine (Casuarina equisettifolia L.) in the Bahamas. Results of vegetation surveys within both forest stands and beach environments suggest that the overall impact of this hurricane was minimal. Less than 13% of forest individuals and 17% of beach individuals surveyed were damaged, and the majority of damage was restricted to just one location for both the forest and beach study sites. The most common damage type within the forest sites was “snapped” trees (8%) and this primarily occurred within trees ranging in size from 7–12 cm in diameter. Browning of the entire foliage was the most common damage type within the beach sites (9.3%) but this damage type only occurred within tree sizes less than or equal to 90 cm in height. Thus it appears that Hurricane Frances had a negligible effect on Australian pine populations as a whole on San Salvador Island and that this disturbance event will probably not limit future population expansion. It is suggested that more powerful or more frequent hurricanes would be needed to significantly affect Australian pine populations on San Salvador Island. Similar patterns in damage should be expected with comparable hurricane events on other islands in the Bahamas and for other tropical beaches in which this species has invaded.

Small and large-scale perturbations can have important impacts on a wide range of biota. Hurricanes are a dominant perturbation in tropical ecosystems. A 1500 ha seasonally dry tropical forest reserve in Quintana Roo, Mexico, was analyzed for epiphyte composition across different seral stages and forest types, including mature forest, tintal wetland area, and secondary vegetation. One-kilometer belt transects (6000 m²) were sampled in each forest type before and after Hurricane Wilma. The surveys revealed twenty three species of vascular epiphytes, primarily from the Bromeliaceae and Orchidaceae families. Immediately following Wilma, fewer than half of previously recorded individuals were observed, while overall species composition differed little. The wetland area sustained losses of 64%, and the mature forest lost 28% of epiphyte individuals. However, the epiphyte communities in the wetland area contained greater than 50% of all observed individuals both before and after the hurricane, thus representing the largest new source pool. Under a changing climate regime of increasing hurricanes, vascular epiphytes of the Yucatán Peninsula may suffer disproportionate losses compared with understory plants. Ultimately, epiphytes must be studied within the framework of community ecology in order to understand the severity of these losses.

This study describes changes within the Leguminosae plant family along two to 25 years of secondary succession after slash-and-burn agriculture and compares regrowth with mature rain forest legume species composition. Research was conducted on a 21-site (12.9 ha) chronosequence and covered all legume plants > 50 cm height. Legume biomass shares ranged from 4–8% in secondary regrowth and were two to four times higher in mature rain forest (17%, or 78 tons ha⁻¹). Legume taxonomic composition differed strongly between secondary and mature rain forests, and floristic similarity (Jaccard's coefficient) of legumes between both forest types was only 34%. Successional changes in legume vegetation shares and taxonomic composition were weak within secondary regrowth, though repeated slash-and-burn did affect legume vegetation. Legume functional composition changed along succession with high shares of potentially N₂-fixing lianas in young regrowth. We conclude that 1) the composition of legume species in the community differs strongly between secondary and mature rain forest but legume composition along regrowth does not provide an adequate criterion for the definition of optimum fallow periods, and 2) legume lianas assume a key functional role in biological N₂-fixation and ecosystem N-cycling especially early along succession.

In this study, we documented the presence of macroscopic (> 2 mm) charcoal, quantified charcoal mass, and radiocarbon-dated charcoal macrofossils in 10 soil cores to develop a coarse-resolution fire history for a mixed hardwood forest on the Cumberland Plateau in Tennessee. Macroscopic charcoal occurred in all 10 soil cores. Total dry mass of macroscopic charcoal varied by core and by depth layer. Charcoal fragments were most abundant in two non-adjacent cores (separated by ca. 80 m), a finding that may be evidence of a patchy fire regime in the study area. AMS radiocarbon dating of the five deepest charcoal samples indicated that the earliest recorded fire in the study site occurred around 6735 cal yr BP (calibrated years before 1950). Charcoal in surface soils was not dated but one deep sample indicated a fire during the historic period at approximately 174 cal yr BP. No overlap occurred within the 2-sigma calibrated age ranges of the dated charcoal samples, indicating a minimum of five separate fire events have occurred on the site during the last 6700 plus years. This was the first study to use soil charcoal to document past fire events in hardwood forests of the Cumberland Plateau and the first to examine the prehistoric fire regime of Quercus stands in the region at a local-scale. Our results provide a basis for reconstructing long-term fire histories at the stand-scale in Quercus-dominated forests of eastern North America.

In 1924, Bob Marshall and his Harvard University advisor Richard Fisher developed an integrated historical approach for forest reconstruction to address ecological questions and provide insights to forest management. Their approach utilized complementary methods and data: dendrochronology, diverse historical records (e.g., deeds, town and oral histories, and census and lumber mill records), and intensive field mapping and sampling of the site including stumps and uproot mounds, and forest composition and structure. Marshall applied this approach broadly to a 61-ha Tsuga canadensis (eastern hemlock)-Pinus strobus (eastern white pine) forest on sandy dry soils and intensively to a 0.15-ha sub-plot. He sought to test his hypothesis that pine and hemlock displayed compositional resilience to disturbance and to understand the life-history and growth characteristics of the two species that enabled co-dominance. Marshall concluded that, in contrast with the successional tendencies of white pine across New England's mesic uplands, pine and hemlock had dominated on these dry, sandy soils since at least the early 1700s and through multiple episodes of logging. Based on his interpretation of the contrasting growth rates and shade tolerance of these species, he developed a simple model of forest development and silviculture to guide management on dry sites for pine and hemlock timber production. Fisher, Marshall, and Harvard Forest colleagues used these historical insights to plan a suite of harvesting experiments on the site in 1924–25 to perpetuate hemlock and pine. Unfortunately, the hurricane of 1938 and subsequent salvage logging terminated the experiment. In 2007, we tested Marshall's interpretations and prediction of resilience in this forest by examining its long-term response to the series of intense disturbances. We synthesized decades of observations, photographs, and data, and relocated Marshall's plot to measure forest age and size structure, composition, and site features including decaying stumps, pits, mounds, and bent and sprouting individuals. The current hemlock and pine forest is strikingly similar in structure and composition to that of 1924. These results reinforce Marshall's conclusion that hemlock and white pine forests on well-drained sandy soils can be remarkably resilient in composition to intense disturbance. The work highlights the development and application of an integrated approach to forest reconstruction by Marshall and Fisher and underscores the contribution of historical insights to addressing basic ecological questions, designing large long-term field experiments, and guiding forest conservation and management.

Ribes (currants and gooseberries) are alternate hosts for Cronartium ribicola, the invasive fungus that causes blister rust of white pines (Pinus, subgenus Strobus) in the Rocky Mountain region of Colorado and Wyoming. The location, species, and density of Ribes can affect the spread and impact of this potentially serious forest disease. We assessed the distribution and density of Ribes growing near white pine stands for 15 study areas in Colorado and Wyoming with 1258 survey plots of two types, an intensive white pine/Ribes survey and an extensive Ribes survey. Species present, total numbers of stems and bushes, average number of stems per bush, and average stem length were recorded. Various Ribes species were present in all study areas across a range of elevations. The most frequent and common species were R. cereum, R. inerme, R. lacustre, and R. montigenum. Densities and probabilities of occurrence were related to site variables and varied by Ribes species. The most common predictive variables included type of dominant overstory, elevation, and general plot classification such as riparian area. The predictive information provided can be utilized by tree health specialists for risk rating of forests and in planning white pine blister rust mitigation projects. We expect that other areas in Colorado and Wyoming with similar site characteristics will have similar distributions and densities of Ribes and thus have similar risks to white pine blister rust.

Over the past three centuries successive land-use decisions have led to significant changes in the composition and structure of the floristic resources at Evansburg State Park in southeastern Pennsylvania. A recent survey of the park identified 544 vascular plant species from 116 families and 337 genera across 26 distinct, yet extremely fragmented, plant communities. Slightly less than 66% of the recorded species are native to the eastern United States and only two species of concern were discovered. Forty-six species were added to the flora of Montgomery County. In addition, woody vegetation in seven mature forest types of the 16 naturally occurring community associations were sampled. A histogram of species importance across these sites reveals a trend towards increasing compositional homogeneity in forested areas. The remaining ten communities are anthropogenically influenced habitats which comprise 75% of the park's acreage, are scattered widely throughout the park, and contain a high percentage of non-native invasive species. A clear shift in the composition of the forested areas towards Acer saccharum and/or Acer rubrum dominated associations is already apparent and likely to persist given the magnitude of adverse events that continue to alter the landscape and disrupt successional processes.