Nathan Swenson

Nathan Swenson
University of Notre Dame | ND · Department of Biological Sciences

PhD

About

265
Publications
121,412
Reads
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22,875
Citations
Introduction
The primary research focus of the laboratory is to discover the mechanisms underlying the origins of plant biodiversity and its distribution through space and time. We believe that a general long-term goal for those studying biodiversity should be to link the evolutionary processes underlying diversification to ecological patterns and interactions across scales. Although we are interested in all ecosystem types, the majority of our research takes place the tropics.
Additional affiliations
June 2018 - present
University of Maryland, College Park
Position
  • Professor
July 2015 - June 2018
University of Maryland, College Park
Position
  • Professor (Associate)
August 2009 - July 2015
Michigan State University
Position
  • Professor (Associate)
Education
August 2004 - May 2008
The University of Arizona
Field of study
  • Ecology and Evolutionary Biology

Publications

Publications (265)
Article
The study of community spatial structure is central to understanding diversity patterns over space and species co‐occurrence at local scales. While most analytical approaches consider horizontal and vertical dimensions separately, in this study we introduce a three‐dimensional spatial analysis that simultaneously includes horizontal and vertical sp...
Article
Maples (the genus Acer) represent important and beloved forest, urban, and ornamental trees distributed throughout the Northern hemisphere. They exist in a diverse array of native ranges and distributions, across spectrums of tolerance or decline, and have varying levels of susceptibility to biotic and abiotic stress. Among Acer species, several st...
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Tropical dry forests (TDFs) have experienced pronounced droughts and increased temperatures for the last century. To assess whether these climatic shifts have influenced dry forest vegetation and ecosystem functioning, we integrated ground observations from a Costa Rican long‐term forest dynamics monitoring plot with remotely sensed measures of for...
Article
1.Unraveling the drivers of forests dynamics is one of the main challenges in tree community ecology. These drivers include niche differentiation, dispersal limitation and stochasticity. Previous work has demonstrated that these mechanisms likely interact such that no one process is responsible for forest dynamics. 2. One possibility is that the f...
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Predicting species abundance is one of the most fundamental pursuits of ecology. Combining the information encoded in functional traits and metacommunities provides a new perspective to predict the abundance of species in communities. We applied a community assembly via trait selection model to predict quadrat-scale species abundances using functio...
Article
Despite important progress in understanding the impacts of forest clearing and logging on aboveground communities, how these disturbances affect soil microbial β‐diversity and the ecological processes driving microbial assemblages are poorly understood. Further, whether and how the microbial shifts affect vegetation composition and diversity during...
Preprint
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Lianas, climbing woody plants, influence the structure and function of tropical forests. Climbing traits have evolved multiple times, including ancestral groups such as gymnosperms and pteridophytes, but the genetic basis of the liana strategy is largely unknown. Here, we use a comparative transcriptomic approach for 47 tropical plant species, incl...
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Large scale disturbances are known to impact the alpha and beta diversity of communities. However, whether these disturbances increase or decrease diversity is often debated. The goal of this study was to quantify how the diversity of the seedling community was impacted within and across elevation in the El Yunque forest of Puerto Rico following a...
Article
Aim Here we examine the functional profile of regional tree species pools across the latitudinal distribution of Neotropical moist forests, and test trait–climate relationships among local communities. We expected opportunistic strategies (acquisitive traits, small seeds) to be overrepresented in species pools further from the equator, but also in...
Article
Trait-based approaches have been extensively used in community ecology to provide a mechanistic understanding of the drivers of community assembly. However, a foundational assumption of the trait framework - traits relate to performance - has been mainly examined through univariate relationships that simplify the complex phenotypic integration of o...
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Quantifying the functional trait space of natural assemblages could help ecologists understand the underlying mechanisms that sustain species richness. In this study, we investigated the functional trait space patterns of six forest passerine bird assemblages, with species richness increasing to lower latitudes. Further, we examined the underlying...
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Predicting drought responses of individual trees in tropical forests remains challenging, in part because trees experience drought differently depending on their position in spatially heterogeneous environments. Specifically, topography and the competitive environment can influence the severity of water stress experienced by individual trees, leadi...
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ForestGEO is a network of scientists and long-term forest dynamics plots (FDPs) spanning the Earth's major forest types. ForestGEO's mission is to advance understanding of the diversity and dynamics of forests and to strengthen global capacity for forest science research. ForestGEO is unique among forest plot networks in its large-scale plot dimens...
Article
Plants allocate biomass to different organs in response to resource variation for maximizing performance, yet we lack a framework that adequately integrates plant responses to the simultaneous variation in above‐ and below‐ground resources. Although traditionally, the optimal partition theory (OPT) has explained patterns of biomass allocation in re...
Article
1. Individual-level demographic outcomes should be predictable upon the basis of traits. However, linking traits to tree performance has proven challenging likely due to a failure to consider physiological traits (i.e. hard-traits) and the failure to integrate organ-level and whole plant-level trait information. 2. Here, we modelled the survival ra...
Article
At local scales, it has been suggested that high levels of resources lead to increased tree growth via trait optimization (highly peaked trait distribution). However, this contrasts with (i) theories that suggest that trait optimization and high growth occur in the most common resource level and (ii) empirical evidence showing that high trait optim...
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One of the important goals in plant ecology is to form a mechanistic link between the underlying processes driving the dynamics and structure of communities and the observed demography (i.e., growth, survival, and recruitment) and assembly (i.e., distribution of species) in a community via traits. Although the importance of traits to performance is...
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1. Understanding tree species responses to biotic and abiotic factors is fundamental for stronger predictions of community assembly and dynamics. However, several challenges remain. These include a failure to investigate whether there is evidence for key hypothesized life‐history tradeoffs and to link these tradeoffs to functional traits. 2. In thi...
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Despite several decades of study in community ecology, the relative importance of the ecological processes that determine species co‐occurrence across spatial scales remains uncertain. Some of this uncertainty may be reduced by studying the scale dependency of community assembly in the light of environmental variation. Phylogenetic information and...
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1. Functional traits are expected to provide insights into the abiotic and biotic drivers of plant demography. However, successfully linking traits to plant demographic performance likely requires the consideration of important contextual and individual‐level information that is often ignored in trait‐based ecology. 2. Here, we modeled 8 years of g...
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Background and aims: The composition and dynamics of plant communities arises from individual-level demographic outcomes, which are driven by interactions between phenotypes and the environment. Functional traits that can be measured across plants are frequently used to model plant growth and survival. Perhaps surprisingly, species average trait v...
Article
Questions We asked: (a) whether the strength of conspecific and heterospecific neighborhood crowding effects on focal tree survival and growth vary with neighborhood radii; and (b) if the relative strength of the effect of neighborhood interactions on tree growth and survival varies with neighborhood scale. Location Luquillo Forest Dynamics Plot,...
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Many studies have tried to assess the role of both deterministic and stochastic processes in community assembly, yet a lack of consensus exists on which processes are more prevalent and at which spatial scales they operate. To shed light on this issue, we tested two non‐mutually exclusive, scale‐dependent hypotheses: 1) that competitive exclusion d...
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Over the past three decades there has been a concerted effort to study the long‐term dynamics of tropical forests throughout the world. Data regarding temporal trends in species diversity, species composition and species‐specific demographic rates have now been amassed. Such data can be utilized to test predictions regarding the roles the environme...
Article
The functional trait values that constitute a whole‐plant phenotype interact with the environment to determine demographic rates. Current approaches often fail to explicitly consider trait‐trait and trait‐environment interactions, which may lead to missed information that is valuable for understanding and predicting the drivers of demographic rates...
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The geographic distribution of plant form and function has been studied for over a century for purposes ranging from vegetation classification to global vegetation modeling. Despite this attention we have surprisingly few studies that have actually mapped the distribution and diversity of quantitative plant traits on continental scales and quantifi...
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Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research sp...
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Forest community composition is the outcome of multiple forces, including those that increase taxonomic and functional divergence and those that promote convergence in traits. The mechanisms underlying these forces may not operate homogenously within communities; individuals of different species are never perfectly mixed, and thus, species tend to...
Article
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Disentangling the processes that drive population, community and whole forest structure and dynamics is a challenge. It becomes a grand challenge in the tropics where there are a large number of species, small population sizes, less research infrastructure, and a relatively smaller number of researchers compared to the temperate zone. Tackling this...
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Transpiration in humid tropical forests modulates the global water cycle and is a key driver of climate regulation. Yet, our understanding of how tropical trees regulate sap flux in response to climate variability remain elusive. With a progressively warming climate, atmospheric evaporative demand (i.e., vapor pressure deficit, VPD) will be increas...
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The mechanisms underlying interspecific variation in conspecific negative density dependence (CNDD) are poorly understood. Using a multilevel modeling approach, we combined long-term seedling demographic data from a subtropical forest plot with soil fungal community data by means of DNA sequencing to address the feedback of various guilds of soil f...
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The relationship between plant functional traits and demographic performance forms the foundation of trait-based ecology. It also serves as the natural linkage between trait-based ecology and much of evolutionary biology. Despite these important aspects, plant trait–demographic performance relationships reported in the literature are typically weak...
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A conspicuous feature of natural communities is that individuals within species exhibit broad variation in their phenotype. While the phenotypic differences among species are prominent and have received considerable attention in earlier studies, recent findings suggest that about 40% of the trait variation is found within species. How this intraspe...
Article
Acer (the maple genus) is one of the diverse tree genera in the Northern Hemisphere with about152 species, most of which are in eastern Asia. There are roughly a dozen of species in Europe/western Asia and a dozen in North America. Several phylogenetic studies of Acer have been conducted since 1998, but none have provided a satisfactory resolution...
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Although populations are phenotypically diverse, the majority of trait‐based studies have focused on examining differences among species. The justification for this broadly applied approach is based on the assumption that differences among species are always greater than within species. This is likely true for local communities, but species are oft...
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Much ecological research aims to explain how climate impacts biodiversity and ecosystem-level processes through functional traits that link environment with individual performance. However, the specific climatic drivers of functional diversity across space and time remain unclear due largely to limitations in the availability of paired trait and cl...
Article
Species composition and community structure in neotropical forests have been severely affected by increases in climate change and disturbance. Among the most conspicuous changes is the proliferation of lianas. These increases have affected not only the carbon storage capacity of forests but also tree dynamics by reducing tree growth and increasing...
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Disturbance plays a key role in shaping forest composition and diversity. We used a community phylogeny and long-term forest dynamics data to investigate biotic and abiotic factors shaping tropical forest regeneration following both human and natural disturbance. Specifically, we examined shifts in seedling phylogenetic and functional (i.e., seed m...
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Survival rates of large trees determine forest biomass dynamics. Survival rates of small trees have been linked to mechanisms that maintain biodiversity across tropical forests. How species survival rates change with size offers insight into the links between biodiversity and ecosystem function across tropical forests. We tested patterns of size-de...
Chapter
Over the past two decades, biodiversity assessments have moved beyond simply measuring species diversity and toward the utilization of phylogenetic information. Despite these major advances toward holistically estimating the similarity of species, challenges remain. Specifically, the large phylogenies utilized for such analyses often contain multip...
Article
1.Investigations of forest community structure and dynamics have been facilitated by the use of neighborhood models that examine the interactions between a focal tree and its neighbors using a fixed radius. However, different studies have chosen different radii without clear reasons, hampering understanding of mechanisms structuring tree communitie...
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As cyclonic wind storms (hurricanes and typhoons) increase in frequency and intensity with climate change, it is important to understand their effects on the populations and communities of tropical trees they impact. Using tree demographic data from four large, tropical forest dynamics plots that differ in cyclonic storm frequency, we compare tree...
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The nutrient demands of regrowing tropical forests are partly satisfied by nitrogen-fixing legume trees, but our understanding of the abundance of those species is biased towards wet tropical regions. Here we show how the abundance of Leguminosae is affected by both recovery from disturbance and large-scale rainfall gradients through a synthesis of...
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Aim A key hypothesis in macroecology is that the relative importance of factors driving ecological phenomena changes with spatial scale. However, studies on ecosystem services usually ignore this. Here, we test how the importance of factors related to climate regulation services varies with spatial extent (i.e., area of assessment) and how covariat...
Article
Individual‐level interactions with neighbours and their surrounding environments are key factors influencing performance that ultimately shape and maintain diversity in tropical plant communities. Theory predicts that the strength of these interactions depends on the similarity among neighbours, the turnover in composition caused by individuals tha...
Article
Foundational to trait-based community ecology is the expectation that functional traits determine demographic outcomes. However, trait-demographic rate relationships are frequently weak, particularly in tree communities. The foundation of trait-based tree community ecology may, therefore, appear to be unstable. Here we argue that there are three co...
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Community structure is the emergent outcome of individual-level interactions. Recent work has shown that disaggregating trait information from the species- to the individual-level elucidates ecological processes. We aim to integrate trait dispersion analyses across different aggregation levels including a broad range of traits that allow assessing...
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Arbuscular mycorrhizal (AM) fungi in the soil may influence tropical tree dynamics and forest succession. The mechanisms are poorly understood, because the functional characteristics and abundances of tree species and AM fungi are likely to be codependent. We used generalized joint attribute modeling to evaluate if AM fungi are associated with thre...
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The distribution and co-occurrence of species are partly the outcome of their interactions with environmental drivers. Drought is a key driver related to the distribution of plant species. Drought events continue to increase in frequency and severity and identifying those aspects of plant function that are related to drought is critical. Here, we p...
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Tropical forests account for a quarter of the global carbon storage and a third of the terrestrial productivity. Few studies have teased apart the relative importance of environmental factors and forest attributes for ecosystem functioning, especially for the tropics. This study aims to relate aboveground biomass (AGB) and biomass dynamics (i.e., n...
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Intra‐specific negative density dependence promotes species coexistence by regulating population sizes. Patterns consistent with such density dependence are frequently reported in diverse tropical tree communities. Empirical evidence demonstrating whether intra‐specific variation is related to these patterns, however, is lacking. The present study...
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Aim: To test the latitudinal gradient in plant species diversity for self-similarity across taxonomic scales and amongst taxa. Location: North America. Methods: We used species richness data from 245 local vascular plant floras to quantify the slope and shape of the latitudinal gradients in species diversity (LGSD) across all plant species as well...
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Interactions among neighbors influence the structure of communities of sessile organisms. Closely related species tend to share habitat and resource requirements and to interact with the same mutualists and natural enemies so that the strength of interspecific interactions tends to decrease with evolutionary divergence time. Nevertheless, the degre...
Article
Multiple anthropogenic drivers affect every natural community, and there is broad interest in using functional traits to understand and predict the consequences for future biodiversity. There is, however, no consensus regarding the choice of analytical methods. We contrast species- and community-level analyses of change in the functional compositio...