Charles Canham

• Ph.D.
• Senior Researcher at Cary Institute of Ecosystem Studies

Shifting species distributions in response to climate change are leading to community reassembly worldwide. Given the importance of forests to the global carbon cycle, reassembly in forests may have important impacts on ecological functioning. Yet, how climate and disturbance jointly influence reassembly has yet to be reconciled. We combined U.S. F...

Carbon sequestration in the forests of the eastern United States is an important offset to the country's CO 2 emissions. Much of the eastern forestland is the product of reforestation of abandoned agricultural land or recovery following clear‐cutting over a century ago. This has led to concerns that eastern forests are even‐aged and that rates of c...

Unlike trees, shrubs (i.e., multiple-stemmed woody plants) do not need evenly spaced large diameter structural roots and therefore should be more responsive to heterogeneous distributions of soil resources and spread further per unit belowground biomass. We therefore hypothesized that compared to trees, shrubs respond more to asymmetric distributio...

U.S. forests, particularly in the eastern states, provide an important offset to greenhouse gas (GHG) emissions. Some have proposed that forest‐based natural climate solutions can be strengthened via a number of strategies, including increases in the production of forest biomass energy. We used output from a forest dynamics model (SORTIE‐ND) in com...

Unlike trees, shrubs (i.e., multiple-stemmed woody plants) do not need evenly spaced large diameter structural roots and thus can spread further per unit belowground biomass. We therefore hypothesized that compared to trees, shrubs respond more to asymmetric distributions of nutrients and reach nutrient-rich patches of soil faster and with less bel...

In mast-seeding species, strong annual variation in seed production is assumed to drive seed fate and ultimately plant recruitment. However, the effects of temporal variation in seed crops on spatial patterns of seed rain and recruitment are poorly understood , in part because of limited data on fine-scale spatial variation of seed deposition. To i...

A large portion of terrestrial carbon (C) is stored as soil organic matter (SOM) so the balance between C inputs to SOM and soil C loss through respiration has important implications for global climate change. Tree-mycorrhizal association is a promising predictor of SOM dynamics, with the effect of ectomycorrhizal (ECM) trees and associated fungi s...

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...

Many temperate tree species have extraordinarily broad distributions along gradients of temperature and precipitation. But it is not clear in most species whether this reflects very broad tolerance of climate conditions, or a high degree of genetic differentiation or phenotypic acclimation in their responses to local climate. Provenance trials and...

Changes to the community ecology of hosts for zoonotic pathogens, particularly rodents, are likely to influence the emergence and prevalence of zoonotic diseases worldwide. However, the complex interactions between abiotic factors, pathogens, vectors, hosts, and both food resources and predators of hosts are difficult to disentangle. Here we (1) us...

In Canada and elsewhere, logging practices in natural-origin forests have shifted toward retention systems where variable levels of mature trees are retained post-logging to promote a diversity of values. We examine multiple sites that experienced a wide range of prior harvest regimes (0–76% basal area removal) to evaluate how harvest intensity and...

Harvesting is the leading cause of adult tree mortality in forests of the northeastern United States. While current rates of timber harvest are generally sustainable, there is considerable pressure to increase the contribution of forest biomass to meet renewable energy goals. We estimated current harvest regimes for different forest types and regio...

Trees affect soil chemistry and nutrient availability via a broad range of processes. Effects can vary dramatically among species, whose distinctive spatial “footprints” can vary for different nutrients. Potentially overlapping effects of neighboring trees in mixed-species stands make footprint shape and interspecific interactions important: If int...

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 ma...

Traits affecting survival from seedling through adult stages are key elements of tree life histories, and it is widely assumed that variation in survival of adult trees plays an important role in the distribution of species along climate gradients. We use data from plots censused by the U.S. Forest Service Forest Inventory and Analysis program duri...

In terms of adult tree mortality, harvesting is the most prevalent disturbance in northeastern United States forests. Previous studies have demonstrated that stand structure and tree species composition are important predictors of harvest. We extend this work to investigate how social factors further influence harvest regimes. By coupling the Fores...

Despite the clear need to predict the effects of climate change on the distribution and abundance of temperate tree species, there is still only a rudimentary understanding of how climate influences key demographic processes that determine the current distribution and abundance of tree species. We use data from the U.S. Forest Service Forest Invent...

Question Small mammals are important consumers of tree seeds in forests worldwide. Few studies, however, have addressed the impacts of small mammals as consumers of herbaceous species in the forest understorey. Local neighbourhood‐scale variation in canopy tree composition has strong effects on resource availability for understorey plants, but can...

Seedling recruitment and survival are critical bottlenecks in tree population dynamics and are likely to play central roles in shifts in species distributions under climate change. We use data from the Forest Inventory and Analysis program to quantify the relationships between two key climate variables—mean annual temperature and growing season wat...

We review and synthesize information on invasions of nonnative forest insects and diseases in the United States, including their ecological and economic impacts, pathways of arrival, distribution within the United States, and policy options for reducing future invasions. Nonnative insects have accumulated in United States forests at a rate of ∼2.5...

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...

Climate and competition are often presented from two opposing views of the dominant driver of individual tree growth and species distribution in temperate forests, such as those in the eastern United States. Previous studies have provided abundant evidence indicating that both factors influence tree growth, and we argue that these effects are not i...

Studies of population dynamics are continually seeking to develop quantitative approaches that can be easily applied to widely available data in ways that can guide management decisions. We present a method for quantifying demographic trends in size-structured populations that we applied to forest tree species and changes in forest structure associ...

Climate and competition are often presented from two opposing views of the dominant driver of individual tree growth and species distribution in temperate forests, such as those in the eastern United States. Previous studies have provided abundant evidence indicating that both factors influence tree growth, and we argue that these effects are not i...

Northern hardwood forests can exhibit considerable temporal stability in their species composition, which litterfall may help to maintain by modifying the soil environment to create an ecological inheritance. We evaluated the evidence for this niche-construction perspective by carrying out a spatially explicit analysis of redistribution of calcium...

Understanding the long‐term impacts of invasive mammalian browsers and granivores in mixed forests is difficult due to the many processes potentially affecting the demography of long‐lived trees. We constructed individual‐based spatially explicit simulation models of two mixed conifer–angiosperm forests, growing on soils of contrasting phosphorus (...

Species affect the dynamics of litter decay through the intrinsic properties of their litter, but also by influencing the environmental conditions imposed by their canopy, roots, and litter layers. We examined how human-induced changes in the relative abundances of two dominant Mediterranean trees-Pinus halepensis and Quercus calliprinos-impact lea...

The definition of baselines is a major step in determining the greenhouse-gas emissions of bioenergy systems. Accounting frameworks with a planning objective might require different baseline attributes and designs than those with a monitoring objective.

Wild et al. (2014, Journal of Vegetation Science 25: 1327–1340) document persistent effects of the spatial distribution of canopy trees on the distribution of regeneration following stand-replacing disturbance in montane Norway spruce forests. The authors suggest a simple physical process for these legacy effects – the accumulation of winter-disper...

Human alterations of landscapes often lead to colonization of ecosystems by new species, which may alter ecosystem structure and function. Understanding canopy changes is important for management of gradually changing ecosystems. Here, we develop a model that both explains and predicts the rate at which colonizing native Pinus halepensis form an up...

Background/Question/Methods Today there are numerous models of climate change impacts on tree species, but empirical analyses of the effects of climate on the distribution and abundance of tree species continue to lag the models. Recent empirical study of the eastern deciduous forest has found that the frequency of a tree species' occurrence amon...

Spatial and temporal variation in tree seed production is an important driver of the population dynamics of trees and of mammalian and avian seed consumers. Many studies have documented strong synchrony in production of intermittent large tree seed crops (masting), with cascading effects on the food webs of seed consumers and their predators. We us...

Afforestation efforts have resulted in extensive plantations of either native or non-native conifers, which in many regions has led to the spread of those conifers into surrounding natural vegetation. This process of species colonization can trigger profound changes in both community dynamics and ecosystem processes. Our study disentangled the comp...

Forests hold a significant proportion of global biodiversity and terrestrial carbon stocks and are at the forefront of human-induced global change. The dynamics and distribution of forest vegetation determines the habitat for other organisms, and regulates the delivery of ecosystem services, including carbon storage. Presenting recent research acro...

There has been enormous interest in the use of forest biomass as a component of the renewable energy portfolio of the northeastern United States. While often touted as an inherently carbon-neutral energy source, it has become clear that a wide range of factors need to be considered to evaluate the net carbon and climate impact of biomass energy pro...

Background/Question/Methods Biotic effects, such as seed predation by small mammals, have been shown to be an important first filter in short-term patterns of seedling recruitment in temperate deciduous forests. However, few, if any, studies have examined if these patterns persist in the long-term. In 1994 we established 36 1x2m hardware cloth sm...

Plant colonization studies usually address density-dependent processes in the narrow sense of recruitment constraints due to negative density-dependent seed and seedling mortality. However, complex density-dependent effects may be involved in additional stages of the recruitment process. We hypothesized that seed arrival and seedling establishment...

Context There is strong interest in sustainable forest management systems that preserve characteristics of forests close to naturalness. Assessing the effectiveness of these systems is difficult because defining “natural” baselines from which impacts are estimated is challenging and because the influence of harvesting can have complex interactions...

Logging is a larger cause of adult tree mortality in northeastern U.S. forests than all other causes of mortality combined. We used Forest Inventory and Analysis (FIA) data to develop statistical models to quantify three different aspects of aggregate regional forest harvest regimes: (1) the annual probability that a plot is logged, as a function o...

We present a collection of papers derived from the 2012 Forest Inventory and Analysis (FIA) Symposium held on December 4-6, 2012 in Baltimore, MD, USA. The symposium featured 128 oral presentations with nearly 200 attendees from the United States and other countries. A proceedings from the symposium included 75 papers as well as abstracts for all p...

Atmospheric nitrogen (N) deposition is altering biogeochemical cycling in forests and interconnected lakes of the northeastern US, and may shift nutrient limitation from N toward other essential elements, such as phosphorus (P). Whether this shift is occurring relative to N deposition gradients across the northeastern US has not been investigated....

Background/Question/Methods Single-tree selection logging is similar to “background” tree mortality of individuals in unmanaged hardwood forests, and is believed to be suitable for shade-tolerant species in smaller areas of woodland. However, few studies have specifically evaluated this method for improving quality and controlling stocking of the...

Background/Question/Methods Forest management techniques that emulate natural disturbance regimes have become increasingly popular as a tool for increasing forest complexity and diversity, yet still remain largely untested. We lack information about how the spatial pattern of canopy trees will alter resource heterogeneity in the understory and th...

Background/Question/Methods Climate change is taking place in the context of a broad suite of other anthropogenic impacts on forest ecosystems, ranging from invasive species to air pollution. But those impacts are very difficult to predict individually. To address the potential interactions among these processes, I have parameterized a spatially-...

Loading of nutrients from terrestrial ecosystems strongly influences the productivity and biogeochemistry of aquatic ecosystems. Human activities can supplement and even dominate nutrient loading to many lakes, particularly in agricultural and urbanized settings. For lakes in more remote regions such as the Adirondack Mountains of New York, N depos...

In the temperate deciduous forests of the northeastern United States, the majority of the dominant tree species disperse their seeds during the fall, causing a heterogeneous mixture of seeds to be present at a specific location at one time. Be-cause these seeds vary in size and palatability to small mammals, some seed species, such as Quercus acorn...

Selective browsing by Odocoileus virginianus (White-tailed Deer) has shifted plant communities in the Northeast, but the effects of seed dispersal by deer on forest seed banks are unknown. We used data from deer exclosures in hunted and unhunted properties in southeastern New York to determine whether deer browsing and different deer management his...

Background/Question/Methods Closed canopy, “intact” forests (i.e. with low anthropogenic disturbance or fragmentation) are traditionally viewed as highly resistant to invasion, mainly because the evidence of exotic invasions is much lower than other ecosystems. However, patterns of invasion dynamics in intact forests are obscured by the longevity...

Background/Question/Methods Recent studies have shown that frequency of occurrence among stands, rather than relative abundance when present, varies consistently along climate gradients for tree species of eastern North America. These results suggest that recruitment processes play a much more important role in abundance of tree species along cli...

Forests store a large portion of global carbon in tree and soil biomass. However, our understanding of the factors that may reduce rates of forest carbon accumulation is incomplete. This study examines the impact of an exotic insect and fungal pathogen disease on aboveground tree biomass in forests of eastern North America. We determine how beech b...

There have been many attempts to model the impacts of climate change on the distributions of temperate tree species, but empirical analyses of the effects of climate on the distribution and abundance of tree species have lagged far behind the models. Here, we used forest inventory data to characterize variation in adult tree abundance along climate...

Background/Question/Methods Masting – the synchronous, heavy production of seeds in a given year by individuals of a population, typically followed by several years with little or no seed production – is widely observed in tree species. There are many hypotheses to explain the evolution of this phenomenon, and many ecological consequences of the...

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...

Human-impacted forests are increasing in extent due to widespread regrowth of secondary forests on abandoned lands. The degree and speed of recovery from human disturbance in these forests will determine their value in terms of biodiversity conservation and ecosystem function. In areas subject to periodic, severe natural disturbances, such as hurri...

Life-history traits of invasive exotic plants are typically considered to be exceptional vis-a-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 parti...

Historical land use has shaped ecosystem structure and function in much of eastern North America, but the question of how long the legacies of 19th and 20th century agriculture will persist in forested landscapes remains a matter of debate. To evaluate whether the legacies of land use are diminishing over time we resampled permanent vegetation plot...

The belief that canopy gaps are important for the maintenance of tree species diversity appears to be widespread, but there have been no formal theoretical models to assess under what conditions gap phase processes allow coexistence. Much of the empirical research on niche diff erentiation in response to gaps has focused on evidence for an interspe...

One of the most significant challenges in developing a predictive understanding of the long-term effects of hurricanes on tropical forests is the development of quantitative models of the relationships between variation in storm intensity and the resulting severity of tree damage and mortality. There have been many comparative studies of interspeci...

Tree species composition of hardwood forests of the northeastern United States corresponds with soil chemistry, and differential performance along soil calcium (Ca) gradients has been proposed as a mechanism for enforcing this fidelity of species to site. We conducted studies in a southern New England forest to test if surface-soil Ca is more impor...

Human activities have greatly accelerated emissions of both carbon dioxide and biologically reactive nitrogen to the atmosphere. As nitrogen availability often limits forest productivity, it has long been expected that anthropogenic nitrogen deposition could stimulate carbon sequestration in forests. However, spatially extensive evidence for deposi...

1. Many forests experience periodic, large-scale disturbances, such as hurricanes and cyclones, which open the forest canopy, causing dramatic changes in understorey light conditions and seedling densities. Thus, in hurricane-impacted forests, large variations in abiotic and biotic conditions likely shape seedling dynamics, which in turn will contr...

Background/Question/Methods The theory and study of invasiveness typically emphasize exceptional early successional life-history traits in invasive exotic plants, enabling the capture of high resources in recently disturbed environments. A key issue in invasion dynamics is whether these pronounced early succesional behaviors come at the expense of...

Background/Question/Methods Understanding the nature of competitive interactions among co-occurring species is central to our understanding of plant communities. It is also critical to the development of sustainable management of forest ecosystems, which are routinely managed for complex residual structure following harvests. In the past decades,...

Forests are often subject to multiple, compounded disturbances, representing both natural and human-induced processes. Predicting forest dynamics requires that we consider how these disturbances interact to affect species demography. Here we present results of an individual-based, spatially explicit forest simulator that we developed to analyze the...

1. A central concept in forest ecology is that differences in the growth rates and shade tolerances of tree species determine patterns of secondary succession. The most shade-tolerant tree species are the competitive dominants in late-successional forests, while species with fast growth rates persist through rapid establishment after disturbance. T...

1. A trade-off between growth in high-light and survival in low-light of species is often proposed as a key mechanism underpinning the dynamics of trees in forest communities. Yet, growth and survival are known to depend on plant size and few studies have analysed how this trade-off can vary between juvenile life stages and the potential consequenc...

Question: Hurricanes and cyclones cause a wide range of damage to coastal forests worldwide. Most of these storms are not catastrophic in ecological terms, but forest responses to storms of moderate intensities are poorly understood. In regions with a high frequency of moderate hurricanes, how does variation in disturbance intensity affect the magn...

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 typ...

Because of differences among target tree species in the scaling of NCI to neighbour size and distance (α and β), the absolute scale of NCI varies among the different species. Thus, the absolute magnitude of the C parameter cannot be used to assess the relative sensitivity to crowding among the nine species. Rather, we have plotted the predicted red...

1.A trade-off between growth in high-light and survival in low-light of species is often proposed as a key mechanism underpinning the dynamics of trees in forest communities. Yet, growth and survival are known to depend on plant size and few studies have analysed how this trade-off can vary between juvenile life stages and the potential consequence...

Assessments of regional forest carbon (C) balance have long speculated a role for atmospheric nitrogen (N) deposition. To date, however, evidence for an N effect has been restricted to plot-level fertilization and 15N experiments, biogeochemical modeling studies, and recent and controversial correlations between nitrogen deposition and C balance ac...

Background/Question/Methods It can be argued that introduced pests and pathogens of native forest trees have been the most profound agents of change in forests of the northeastern US over the past century. The pace of introductions of novel pests and pathogens has accelerated in recent years, presumably in response to increased globalization of t...

Allelopathic interactions between invasive and native species have been suggested to be an important mechanism for the success of some of the most aggressive plant invaders. However, field experiments that test the effects of natural levels of allelopathic compounds on coexisting native species are exceptionally rare. In this study, we analyzed the...

Changes in the composition of a community due to the invasion by exotic plant species can lead to modi. cation of ecosystem function that, in turn, produces feedbacks that drive further changes in community composition. The development of predictive models of this process requires an understanding of the spatial extent of the impacts of the exotic...

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...

Nitrogen (N) has historically been considered the most important mineral nutrient affecting performance of saplings in transitional northern hardwood forest of eastern North America, but recent attention has focused on the role of exchangeable soil calcium. Relative limitation by these factors may be changing because of enrichment of soil N from at...

House mice Mus musculus and other introduced rodents represent a novel source of predation on tree seeds in New Zealand forests. In the northern temperate forests where these rodents are native, spatial and temporal variation in tree seed production can result in dramatic fluctuations in the distribution and abundance of seed predators, with subseq...

Robust predictions of competitive interactions among canopy trees and variation in tree growth along environmental gradients represent key challenges for the management of mixed-species, uneven-aged forests. We analyzed the effects of competition on tree growth along environmental gradients for eight of the most common tree species in southern New...

Severe winds are the predominant cause of natural disturbance in temperate forests of north‐eastern and north‐central North America. Conceptual models of the effects of wind disturbance have traditionally focused on the impacts of catastrophic disturbances and have painted a simple picture of how disturbance acts to maintain tree species diversity....

We have characterized overstory light transmission, understory light levels, and plant communities in mixedwood boreal forests of northwestern Quebec with the objective of understanding how overstory light transmission interacts with composition and time since disturbance to influence the diversity and composition of understory vegetation, and, in...

Risk of human exposure to vector-borne zoonotic pathogens is a function of the abundance and infection prevalence of vectors. We assessed the determinants of Lyme-disease risk (density and Borrelia burgdorferi-infection prevalence of nymphal Ixodes scapularis ticks) over 13 y on several field plots within eastern deciduous forests in the epicente...

The forests of eastern North America have been subjected to repeated introductions of exotic insect pests and pathogens over the last century, and several new pests are currently invading, or threatening to invade, the region. These pests and pathogens can have major short- and long-term impacts on forest ecosystem processes such as productivity, n...

We use permanent-plot data from the USDA Forest Service's Forest Inventory and Analysis (FIA) program for an analysis of the effects of competition on tree growth along environmental gradients for the 14 most abundant tree species in forests of northern New England, USA. Our analysis estimates actual growth for each individual tree of a given speci...

In this study, we ask if instead of being fundamentally opposed, niche and neutral theories could simply be located at the extremes of a continuum. First, we present a model of recruitment probabilities that combines both niche and neutral processes. From this model, we predict and test whether the relative importance of niche vs. neutral processes...

Advances in computing power in the past 20 years have led to a proliferation of spatially explicit, individual-based models of population and ecosystem dynamics. In forest ecosystems, the individual-based models encapsulate an emerging theory of "neighborhood" dynamics, in which fine-scale spatial interactions regulate the demography of component t...

Terrestrial and aquatic ecosystems are intimately linked by the export of elements from watersheds. Although export is influenced by land cover within watersheds, few models evaluate how the spatial configuration of land cover influences loading. In this Study we examined spatial variation of land cover at a 10 X 10 In resolution by developing a ma...

Rankings of species-specific juvenile tree growth and survivorship define competitive hierarchies that play a central role in forest dynamics and may also vary in response to herbivory. We conducted an experiment to examine species-specific rankings of sapling growth and survival for six common tree species in temperate forests of the northeastern...

Tropical ecosystems house a significant proportion of global biodiversity. To understand how these ecosystems function we need to appreciate not only what plants, animals and microbes they contain, but also how they interact with each other. This volume, first published in 2005, synthesises the state of knowledge in this area, with chapters providi...

In forests of eastern North America, introduced pathogens have caused widespread declines in a number of important tree species, including dominant species such as American beech (Fagus grandifolia Ehrh.). Most studies have focused on changes in forest composition and structure as a direct result of mortality caused by a pathogen. Our field studies...

Angiosperm trees often dominate forests growing in resource‐rich habitats, whereas conifers are generally restricted to less productive habitats. It has been suggested that conifers may be displaced by angiosperms except where competition is less intense, because conifer seedlings are inherently slow growing, and are outpaced by faster‐growing angi...

We used inverse modelling to parameterize spatially‐explicit seedling recruitment functions for nine canopy tree species in the Luquillo Forest Dynamics Plot (LFDP), Puerto Rico. We modelled the observed spatial variation in seedling recruitment following Hurricane Georges as a function of the potential number of seedlings at a given location (base...

We present a likelihood‐based regression method that was developed to analyze the effects of neighborhood competitive interactions and hurricane damage on tree growth and survival. The purpose of the method is to provide robust parameter estimates for a spatially explicit forest simulator and to gain insight into the processes that drive the patter...

We compared three commonly used empirical seed/seedling dispersal functions for trees (lognormal, 2Dt, and two‐parameter Weibull) by analysis of published studies where the location of the source is known, as well as by inverse modelling within an old growth hardwood forest in southern Quebec. Almost all the species were wind‐dispersed. For the dis...

We present a critical review of current trends in research of spatio-temporal development of forests. The paper addresses (1) field methods for the development of spatially-explicit models of forest dynamics and their integration in models of forest dynamics, (2) strengths and limitations of traditional patch models versus spatially-explicit, indiv...