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Copyright of Journal of Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Although closed‐canopy forests are characterized by low‐light availability and slow population dynamics, many are under threat from non‐native, invasive woody species that combine high colonization ability and fast growth potential with high low‐light survival. This 'superinvader' phenotype contravenes expected trade‐offs predicted by successional niche theory, posing a challenge to both invasion and forest succession theory.We propose a parsimonious conceptual model based on the whole‐plant light compensation point (WPLCP) that, across a variety of plant strategies and growth forms, can explain greater competitive abilities of forest invaders in the context of both high‐light growth rate and shade tolerance. The model requires only that non‐native species experience relatively fewer carbon costs than native species, enabling resource‐acquisitive species to establish in low‐light conditions.We review evidence for lower carbon costs in invasive species resulting from (1) enemy release, (2) recent environmental changes that favour less stress‐tolerant phenotypes and (3) phylogenetically constrained native floras. We also discuss implications of invader shade tolerance in the context of other life‐history strategies that, combined with canopy disturbances, facilitate their rapid numerical dominance.Synthesis. An invasion framework driven by carbon dynamics suggests renewed focus on whole‐plant carbon costs, including below‐ground respiration and tissue turnover, which are rarely measured in functional studies of forest invaders. [ABSTRACT FROM AUTHOR]

Copyright of Biotropica is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Functional Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recent observational studies report weak or flat temperature − growth relationships for many tree species in temperate forests. In contrast, distribution limits of trees are strongly shaped by temperature, and studies show marked short‐term temperature effects on leaf‐level ecophysiology. To better determine the effects of warming on trees, we planted one‐year‐old seedlings of one lower montane (ponderosa pine), two upper montane (quaking aspen and lodgepole pine), and one subalpine tree species (subalpine fir) in in situ experimental gardens on an elevation gradient in the Rocky Mountains (USA) which span a 6°C range in temperature but have approximately uniform precipitation. Seedlings were lightly watered the first three growing seasons to facilitate establishment, and growth and survivorship were followed for four years. We expected a trade‐off between growth and survivorship, as seedlings in high temperatures grow faster (e.g., with a longer growing season), but have higher mortality from heat stress. Compared to the coldest site, aspen (+256% wider, +337% taller), ponderosa pine (+234% wider, 270% taller), and lodgepole pine (+235% wider, 283% taller) all had strikingly higher cumulative diameter and height growth in the warmest site by the end of the study. Linear models of cumulative and annual growth in the montane species showed strong, positive relationships with growing‐season temperature, but no significant relationships with growing‐season precipitation. In contrast, growth of subalpine fir did not vary significantly with temperature, but increased slightly with higher growing‐season precipitation. Accelerated growth did not come at the expense of survivorship in the montane species: cumulative four‐year survivorship of the montane species remained robust (71.4–94.4%) in high temperatures, but caused complete mortality of subalpine fir. As long as precipitation remains adequate, these results indicate that warming is likely to strongly increase growth in seedlings of montane species with only modest decreases in survivorship despite higher evapotranspiration, especially in cooler and wetter portions of their current distributions where hydric stress is low. In contrast, warming may negatively affect seedling growth and survival in hotter and drier areas of the Rockies, and warming of +3–6°C may endanger the persistence of subalpine fir over much of its current distribution. [ABSTRACT FROM AUTHOR]

Over the course of 16 d in the fall of 1998, Hurricane Georges made landfall on five Caribbean Island nations, two U.S. states, and two territories. Along its path, it impacted nearly every type of built environment and terrestrial and marine ecosystem found in the Caribbean and the southeastern United States. We reviewed ecological and sociological research related to Georges in order to demonstrate the potential power of regional synoptic networks despite notable gaps that existed at the time. Most studies examined various effects and responses within four years of the storm, though a few reported longer‐term results. Reduction in forest stem density was the most reported ecological effect and ranged from 7% to 51% among sites in different forest types. Forests previously impacted by Hurricane Hugo in 1989 showed lower mortality from Georges than forests with longer hurricane‐free intervals. Rivers in the storm's path exported heavy loads of sediment to marine systems. For example, 5–10 million tons of sediment was transported to marine systems from Puerto Rico, and suspended sediments increased tenfold in coastal Louisiana. Economic costs directly related to Hurricane Georges ranged from 5% to 200% of annual GDP in the year after the storm. Sociological research indicated that children and college students exposed to Hurricane Georges experienced elevated effects on mental health such as anxiety and depression for up to 2.5 yr. Established research areas and longitudinal studies were valuable in understanding hurricane effects in the context of long‐term trends but fragmented research capacity reduced both local and regional synthetic efforts. Georges provides a template of how future integrated research programs could provide a deeper understanding of how nature, urbanization, human culture, and societal norms interact, respond, and recover from a major hurricane. However, future studies should avoid using the Saffir‐Simpson scale as a shorthand indicator or predictor of storm effects because topographic, historical, ecological, political, infrastructural, and societal factors interact to alter storm effects. The breadth of topics addressed in the research produced after Georges shows the potential for transformative, regionally synthetic research that spans whole watersheds and nearshore areas while integrating ecological and social sciences. [ABSTRACT FROM AUTHOR]

The abundant-center hypothesis posits species are most abundant in the center of their climatic range and forms a key assumption in many species distribution models. However, this hypothesis has not been rigorously evaluated in plant communities, in part because abundance as a fraction of dominance is rarely incorporated. Here, we ask whether tree species frequency and abundance peak in the center of their distributions on continental-scale climate gradients across the Rocky Mountains and Interior West, USA. We used forest inventory data to model frequency (percentage of plots in a given climate a species occurred in) and relative abundance (percentage of basal area in plots) as a flexible function of climate for the 20 most common tree species on temperature and precipitation gradients. Frequency patterns were pre-dominately “bell-shaped”and centered for species in the middle of both gradients and monotonic toward the extremes. Relative abundance patterns were primarily monotonic, especially with precipitation. In the middle of the temperature gradient, however, it is notable that six dominant and widespread species had peaks in both frequency and abundance that were centered and symmetric. Only one species had this pat-tern with precipitation. When frequency is considered, evidence for the abundant-center hypothesis is robust, especially in the middle portion of each gradient, and indicates patch occupancy probability generally declines away from a species' climatic optimum. For relative abundance, the hypothesis is largely refuted, particularly on the precipitation gradient. Together, these results suggest that climate's influence on patch colonization and occupancy dynamics is a fundamental filter on distribution patterns in Rocky Mountain forests, but that climate gradients are only weakly related to relative abundance and hence provide limited insight into the ecological processes that determine local dominance once a species is present in a site. [ABSTRACT FROM AUTHOR]

Aim: The rate and magnitude of climate‐induced tree range shifts may be influenced by range‐wide variation in recruitment, which acts as a bottleneck in tree range dynamics. Here, we compare range predictions made using standard species distribution models (SDMs) and an integrated metamodelling approach that assimilates data on adult occurrence, seedling recruitment dynamics, and seedling survival under both current and future climate, and evaluate the degree to which information provided by seedling data can improve predictions of range dynamics. Location: The interior west region of the United States. Time period: 1990–2015. Major taxa studied: Five widespread conifer tree species. Methods: We used a previously published metamodelling framework to combine information from SDMs of adult tree occurrence and sub‐models describing seedling recruitment dynamics and seedling survival into a single set of predictions for the probability of occurrence for each species. The integrated framework links sub‐models to a SDM to generate cohesive predictions that consider information and uncertainty contained in all datasets. We then compared predictions from the integrated model to SDM predictions. Results: Integration of seedling information served primarily to improve characterization of model uncertainty, particularly in regions where recruitment may be limited by temperatures that exceed seedling tolerance. Integration constrained response curves very slightly across most climate gradients, particularly across temperature gradients. These differences were primarily attributable to the isolated effects of temperature on seedling survival and not to recruitment dynamics. Main conclusions: Our results indicate that range‐wide variation in recruitment both now and in the future is most uncertain along the edges of occupied regions, which increases uncertainty in projections of future species occurrence along range margins. Overall, the broad‐scale climatic dependence of the regeneration niche appears weaker than that of the adult climatic niche, and this enhances uncertainty in predicting range‐wide responses of these species to climate change. [ABSTRACT FROM AUTHOR]

Climate is widely assumed to influence physiological and demographic processes in trees, and hence forest composition, biomass and range limits. Growth in trees is an important barometer of climate change impacts on forests as growth is highly correlated with other demographic processes including tree mortality and fecundity., We investigated the main drivers of diameter growth for five common tree species occurring in the Rocky Mountains of the western United States using nonlinear regression methods. We quantified growth at the individual tree level from tree core samples collected across broad environmental gradients. We estimated the effects of both climate variation and biotic interactions on growth processes and tested for evidence that disjunct populations of a species respond differentially to climate., Relationships between tree growth and climate varied by species and location. Growth in all species responded positively to increases in annual moisture up to a threshold level. Modest linear responses to temperature, both positive and negative, were observed at many sites. However, model results also revealed evidence for differentiated responses to local site conditions in all species. In severe environments in particular, growth responses varied nonlinearly with temperature. For example, in northerly cold locations pronounced positive growth responses to increasing temperatures were observed. In warmer southerly climates, growth responses were unimodal, declining markedly above a threshold temperature level., Net effects from biotic interactions on diameter growth were negative for all study species. Evidence for facilitative effects was not detected. For some species, competitive effects more strongly influenced growth performance than climate. Competitive interactions also modified growth responses to climate to some degree., Synthesis. These analyses suggest that climate change will have complex, species-specific effects on tree growth in the Rocky Mountains due to nonlinear responses to climate, differentiated growth processes that vary by location and complex species interactions that impact growth and potentially modify responses to climate. Thus, robust model simulations of future growth responses to climate trends may need to integrate realistic scenarios of neighbourhood effects as well as variability in tree performance attributed to differentiated populations. [ABSTRACT FROM AUTHOR]

Seed production by Picea engelmannii was monitored at 13 sites distributed across a ˜670 m elevation gradient for 40 years. Time series of annual seed output was investigated for evidence of masting behaviour and trends in seed abundance over time., We used regression models in a likelihood framework to examine climate effects on seed production for critical periods in the species' reproductive cycle., We rigorously evaluated the performance of two gridded climate data sets, PRISM and TopoWx, before using associated variables as predictors in the seed models., Seed production at these sites does not strictly conform to the classic masting concept. Seed abundance was highly variable over time and strongly synchronized among sites, but mast years could not be objectively identified due to intermediate levels of seed output., Model results indicate that climate conditions across multiple years cumulatively determine reproductive output. High seed rain is associated with elevated summer temperatures in the year that seeds are dispersed, low spring snowfall in the year preceding seed dispersal when buds are initiated, and reduced spring snowfall in a so-called priming year two years prior to seed dispersal. Low spring precipitation putatively increases growing season length and resource accumulation in seed trees., Linear models identified significant positive trends in seed output over time. Anomalous aridity and summer warmth in the latter half of the study period were highly favourable for seed production and were associated with increases in seed abundance., Synthesis. The increases in seed output observed in this study may promote population fitness of P. engelmannii in the face of changing climate regimes and increasing frequencies of fire- and insect-related tree mortality in the Rocky Mountains. Since this species lacks a persistent seed bank, re-colonization of disturbed areas or dispersal to shifting habitats depends on adequate production of seed by surviving trees, which according to these analyses may be moderately enhanced by current climate trends. However, some evidence also indicates that increases in seed output will ultimately be constrained by threshold high temperatures in the seed maturation year. [ABSTRACT FROM AUTHOR]

Tropical montane forests house unusual and diverse biota and are considered highly vulnerable to climate change, particularly near the trade wind inversion ( TWI) - the upper end of the cloud belt that defines tropical montane cloud forest ( TMCF). The upper cloud belt has two possible futures: one hypothesis postulates a 'lifting cloud base', raising both the upper and lower ends of the cloud belt; the other expects the upper end of the cloud belt will change independently, with a 'shifting TWI'., We used a ˜5900-year-long palaeorecord of vegetation and fire from a small forest hollow at 2455 m in the Cordillera Central, Dominican Republic. The site sits near the upper limit of TMCF taxa and the TWI and allows us to evaluate the relationship between vegetation dynamics and two potential drivers of TWI elevation - the Intertropical Convergence Zone ( ITCZ) and the El Niño/ Southern Oscillation ( ENSO)., Vegetation changed from cloud forest (˜5900-5500 cal. years BP) to alpine grassland (˜4300-1300 cal. years BP), to pine savanna (˜1300-600 cal. years BP) and finally to closed pine forest (after ˜600 cal. years BP). Habitat distribution models for TMCF and pine forest taxa show that these state changes were strongly associated with position of the ITCZ (cloud forest x R2 = 0.63; pine forest x R2 = 0.53), providing support for the shifting TWI hypothesis., We find a negative relationship between fire and TMCF and a hump-shaped relationship between fire activity and pine., Synthesis. Shifts up- and downslope of the upper limit of the cloud belt over the last 5900 years produced major vegetation changes. Fire also played a significant role, in particular when pine occupied the site after ˜1300 years ago and from 1965 AD when fire suppression led to a rapid return of cloud forest taxa. Our results strongly suggest that latitudinal shifts in the ITCZ position have controlled the upper limit of cloud forest in the Caribbean and understanding how the ITCZ will respond to climate change will be critical for tropical montane conservation strategies. [ABSTRACT FROM AUTHOR]

Copyright of Biotropica is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

1. The study of invasiveness typically emphasizes early successional life-history traits in exotic plants, which enable the capture of high resources in disturbed environments and rapid growth. A key issue in invasion dynamics is whether such behaviours come at the expense of traits such as low-light survivorship, which allow species to become more dominant later in succession. 2. We used maximum-likelihood analysis to compare the growth and survivorship of two exotic trees, Ailanthus altissima and Acer platanoides, with nine dominant native tree species in closed-canopy forests in Connecticut, USA. Growth was modelled as a function of light and survivorship as a function of recent growth; combining models yielded estimates of light-dependent mortality. 3. The exotic species had strikingly high growth rates, exceeding all native species at light levels ≥ 10% full sun, and growing 2.6 times faster than the fastest-growing native species at 80% full sun. At low-light levels (< 3% full sun), however, growth rates of five native species exceeded both exotics. Exotic species survivorship (as a function of light-driven growth) was strongly dependent on the degree of shading: at 1% full sun, the annual mortality rate of A. platanoides was 10% and A. altissima was 17%; only two native species had higher mortalities. However, at 5% full sun, A. platanoides’ mortality was < 1%, superior to all but three native species. Mortality of all species dropped to < 1% by 10% full sun, except A. altissima whose mortality remained high at c. 10%. 4. A life-history trade-off analysis (based on radial growth, height allometry and low-light survivorship) shows a nearly linear trade-off for most species. The native species and Ailanthus follow the common life-history trade-off of low-light survivorship vs. high-light growth. However, A. platanoides diverges from this trade-off pattern by combining very high growth rates with moderately high shade tolerance. 5. Simulations with SORTIE-ND (a forest dynamics model) indicate that poor survivorship of A. altissima will limit it to disturbed sites, whereas A. platanoides’ unusual combination of traits makes it invasive in both disturbed and undisturbed forests. Overall, native shade-tolerant trees and slow stand dynamics make undisturbed forests highly resistant to invasion by exotic trees that are intolerant of shade. 6. Synthesis. This study showcases the importance of rapid growth in invasive plants, holding even for exotic tree species known to invade established forests. For A. altissima, high growth rates were accompanied by poor low-light survivorship. A. platanoides departs from the general trade-off pattern that exists among native species and A. altissima, and consequently it can be highly invasive in closed-canopy forests. [ABSTRACT FROM AUTHOR]

Life-history traits of invasive exotic plants are typically considered to be exceptional vis-à-vis native species. In particular, hyper-fecundity and long range dispersal are regarded as invasive traits, but direct comparisons with native species are needed to identify the life-history stages behind invasiveness. Until recently, this task was particularly problematic in forests as tree fecundity and dispersal were difficult to characterize in closed stands. We used inverse modelling to parameterize fecundity, seed dispersal and seedling dispersion functions for two exotic and eight native tree species in closed-canopy forests in Connecticut, USA. Interannual variation in seed production was dramatic for all species, with complete seed crop failures in at least one year for six native species. However, the average per capita seed production of the exotic Ailanthus altissima was extraordinary: > 40 times higher than the next highest species. Seed production of the shade tolerant exotic Acer platanoides was average, but much higher than the native shade tolerant species, and the density of its established seedlings (≥ 3 years) was higher than any other species. Overall, the data supported a model in which adults of native and exotic species must reach a minimum size before seed production occurred. Once reached, the relationship between tree diameter and seed production was fairly flat for seven species, including both exotics. Seed dispersal was highly localized and usually showed a steep decline with increasing distance from parent trees: only Ailanthus altissima and Fraxinus americana had mean dispersal distances > 10 m. Janzen-Connell patterns were clearly evident for both native and exotic species, as the mode and mean dispersion distance of seedlings were further from potential parent trees than seeds. The comparable intensity of Janzen-Connell effects between native and exotic species suggests that the enemy escape hypothesis alone cannot explain the invasiveness of these exotics. Our study confirms the general importance of colonization processes in invasions, yet demonstrates how invasiveness can occur via divergent colonization strategies. Dispersal limitation of Acer platanoides and recruitment limitation of Ailanthus altissima will likely constitute some limit on their invasiveness in closed-canopy forests. [ABSTRACT FROM AUTHOR]

Invasion ecology has traditionally focused on exotic plant species with early successional life-history traits, adapted to colonize areas following disturbance. However, the ecological importance of these traits may be overstated, in part because most invasive plants originate from intentional introductions. Furthermore, this focus neglects the types of plants most likely to invade established communities, particularly forests -- namely shade-tolerant, late-successional species. In invasion ecology, it is generally assumed that undisturbed forests are highly resistant to plant invasions. Our review reveals that this assumption is not justified: in temperate and tropical regions around the world, at least 139 exotic plant species are known to have invaded deeply shaded forest understories that have not undergone substantial disturbance. These exotics present a particular management challenge, as they often increase in abundance during succession. While forest invasions may develop comparatively slowly under natural disturbance regimes, anthropogenic processes, including the spread of exotic pests and pathogens, can be expected to accelerate the rate of invasion. [ABSTRACT FROM AUTHOR]

1. Effects of invasive species on ecosystem processes are often thought to underlie the effects of invaders on community dynamics. Specifically, positive feedbacks in which invasive species alter ecosystem function in ways that favour their own growth have been suggested as an important mechanism contributing to the success of invasion. 2. In this study, we analysed the impacts of the invasive exotic tree Acer platanoides on survival and growth of conspecific and native tree seedlings, and explored whether these impacts can be explained by the ecosystem effects of the invader. Seedlings of Acer platanoides, Acer saccharum, Fraxinus americana and Prunus serotina were monitored in quadrats in three forest stands in north-western Connecticut. Soil resources and light levels were quantified in the same quadrats. 3. Maximum-likelihood methods were used to predict seedling survival and growth as a function of the size and spatial configuration of A. platanoides trees in the immediate neighbourhood (0–25 m). 4. The abundance of A. platanoides in the neighbourhood had moderate negative effects on survival of first-year conspecific seedlings, but did not affect survival of older conspecific or native seedlings. These negative effects on conspecifics were not correlated with soil nutrients or light levels, but were presumably related to Janzen-Connell effects. In contrast, A. platanoides had strong positive effects on the growth of seedlings of all four species. These positive effects appear to be related to the positive impacts of the invader on soil fertility. 5. Our results support the importance of canopy-seedling feedbacks as a mechanism regulating the rate of invasion in forests. However, they also indicate that the net consequences of feedbacks on the process of invasion are probably determined by the balance of positive and negative feedbacks acting at the same time on different aspects of regeneration (i.e. survival vs. growth). 6. Synthesis. Because the species with the highest inherent growth rates were the most responsive to the ‘fertilizing’ effect of A. platanoides, we conclude that the invasion of north-eastern forests by this exotic tree may facilitate canopy dominance by fast-growing native and exotic species associated with fertile soils. [ABSTRACT FROM AUTHOR]

Aim We examined relationships between climate–disturbance gradients and patterns of vegetation zonation and ecotones on a subtropical mountain range. Location The study was conducted on the windward slopes of the Cordillera Central, Dominican Republic, where cloud forest appears to shift in a narrow ecotone to monodominant forest of Pinus occidentalis. Methods Climate, disturbance and vegetation data were collected over the elevation range 1100–3100 m and in 50 paired plots along the ecotone. Aerial photographs were georeferenced to a high-resolution digital elevation model in order to enable the analysis of landscape-scale patterns of the ecotone. Results A Shipley–Keddy test detected discrete compositional ecotones at 2200 and 2500 m; the distributions of tree species at lower elevations were continuous. The elevation of the ecotone determined with aerial photographs was fairly consistent, namely ± 164 m (SD) over its 124-km length, but it exhibited significant landscape variation, occurring at a lower elevation in a partially leeward, western zone. The ecotone also occurred significantly lower on ridges than it did in drainage gullies. Ecotone forest structure and composition differed markedly between paired plots. In pine paired plots, the canopy height was 1.7 times higher and the basal area of non-pine species was 6 times lower than in the cloud forest directly below. Fire evidence was ubiquitous in the pine forest but rare in the abutting cloud forest. Mesoclimate changed discontinuously around the elevation of the ecotone: humidity and cloud formation decreased markedly, and frost frequency increased exponentially. Main conclusions The discreteness of the ecotone was produced primarily by fire. The elevational consistency of the ecotone, however, resulted from the overarching influence of mesoclimate on the elevational patterns of fire occurrence. Declining temperature and precipitation combine with the trade-wind inversion to create a narrow zone where high-elevation fires extinguish, enabling fire-sensitive and fire-tolerant taxa to abut. Once established, mesotopography and contrasting vegetation physiognomy probably reinforce this boundary through feedbacks on microenvironment and fire likelihood. The prominence of the pine in this study – and of temperate and fire-tolerant taxa in subtropical montane forests in general – highlights the importance of climate-disturbance–biogeography interactions in ecotone formation, particularly where fire mediates a dynamic between climate and vegetation. [ABSTRACT FROM AUTHOR]

1 Intact, closed canopied forests appear highly resistant to exotic plant invasions, but there are few experimental studies of this observation. To test this issue and explore the conditions that foster resistance, we experimentally added Norway maple ( Acer platanoides L.) seeds to intact forests for 3 years and monitored emergence, survivorship and height growth for 5 years. 2 Seed additions (250 seeds−1 m2) were replicated in situ in combinations of light (deep shade vs. small gaps), soil fertility (NO3 and pH), and variation in soil moisture as influenced by topography (hill slopes vs. flat areas at slope bases) in five eastern deciduous forests in central New York and southern Connecticut. We then parameterized a model with this data to project long-term rates of sapling recruitment. 3 Seedlings had high survival and low growth rates in the deep shade, suggesting that this species readily forms a seedling bank in intact forests. By age 5, annual survivorship reached 93% in deep shade and 98% in small gaps. Median seedling heights were ≤ 10 cm in all treatments after 5 years, though the largest seedlings were markedly taller in gaps. Mean year 5 densities of all experimental seedlings (ages 3–5 years) were 14 seedlings−1 m2 (± 2.4 SE) in the shade and 19 seedlings−1 m2 (± 3.5 SE) in small gaps. 4 While seedlings colonized in all conditions, resistance to invasion varied markedly; resistance was highest in deeply shaded, acidic conditions (pH < 4.5). Small gaps initially promoted invasion, but by age 4 shade survivorship rates were equivalent to gaps. Higher soil pH (especially > 6) also significantly increased survivorship, particularly in deep shade. Shading's main effect was to suppress height growth. Overall, the model predicted impressive sapling recruitment; even in deeply shaded, acidic conditions, approximately 1% of seeds emerge and survive to become saplings. 5 Intact forests only weakly resisted A. platanoides colonization, but strongly suppressed its rate of invasion. As such, the frequency of disturbance, though ultimately unnecessary for A. platanoides invasions, will strongly influence its near-term invasiveness. Dispersal limitation and slow stand dynamics appear to be the primary constraints on its current distribution. [ABSTRACT FROM AUTHOR]