Catherine A Gehring

Northern Arizona University | NAU · Department of Biological Sciences

Our understanding of the mechanisms that maintain forest diversity under changing climate can benefit from knowledge about traits that are closely linked to fitness. We tested whether the link between traits and seed number and seed size is consistent with two hypotheses, termed the leaf economics spectrum and the plant size syndrome, or whether re...

During the United Nation's Decade on Ecosystem Restoration, planting material shortages are constraining restoration, while climate change exacerbates the need for restoration and reduces recruitment. Concurrently, research shows that native mycorrhizal fungi (symbiotic with plant roots) appropriate to plant provenance and site conditions significa...

The type of mycorrhizal associations (i.e. ecto‐ or arbuscular mycorrhizal) formed by trees is of fundamental importance for a range of soil properties and processes in forests, yet their importance for the distribution of other important soil biota such as bacteria is largely unknown. We used an experimental common garden and amplicon sequencing t...

Multispecies interbreeding networks, or syngameons, have been increasingly reported in natural systems. However, the formation, structure, and maintenance of syngameons have received little attention. Through gene flow, syngameons can increase genetic diversity, facilitate the colonization of new environments, and contribute to hybrid speciation. I...

Disturbances alter biodiversity via their specific characteristics, including severity and extent in the landscape, which act at different temporal and spatial scales. Biodiversity response to disturbance also depends on the community characteristics and habitat requirements of species. Untangling the mechanistic interplay of these factors has guid...

Displacement of diverse native plant communities by low-diversity invasive communities is a global problem. In the western United States, the displacement of sagebrush-dominated communities by cheatgrass has increased since the 1920s. Restoration outcomes are poor, potentially due to soil alteration by cheatgrass. We explored the poorly understood...

Abstract Selection on quantitative traits by heterogeneous climatic conditions can lead to substantial trait variation across a species range. In the context of rapidly changing environments, however, it is equally important to understand selection on trait plasticity. To evaluate the role of selection in driving divergences in traits and their ass...

Selection on quantitative traits by divergent climatic conditions can lead to substantial trait variation across a species range. In the context of rapidly changing environments, however, it is equally important to understand selection on trait plasticity. To evaluate the role of selection in driving divergences in traits and their associated plast...

Lack of tree fecundity data across climatic gradients precludes the analysis of how seed supply contributes to global variation in forest regeneration and biotic interactions responsible for biodiversity. A global synthesis of raw seedproduction data shows a 250‐fold increase in seed abundance from cold‐dry to warm‐wet climates, driven primarily by...

The relationships that control seed production in trees are fundamental to understanding the evolution of forest species and their capacity to recover from increasing losses to drought, fire, and harvest. A synthesis of fecundity data from 714 species worldwide allowed us to examine hypotheses that are central to quantifying reproduction, a foundat...

Ecological genomics approaches have informed us about the structure of genetic diversity in natural populations that might underlie patterns in trait variation. However, we still know surprisingly little about the mechanisms that permit organisms to adapt to variable environmental conditions. The salt marsh foundation plant Spartina alterniflora ex...

Leaf carbon gain optimization in hot environments requires balancing leaf thermoregulation with avoiding excessive water loss via transpiration and hydraulic failure. The tradeoffs between leaf thermoregulation and transpirational water loss can determine the ecological consequences of heat waves that are increasing in frequency and intensity. We e...

The roots and rhizospheres of trees harbor diverse microbial communities that can modulate plant competition and facilitation, thereby influencing plant community dynamics. Understanding the factors structuring microbial communities is valuable for predicting how plant communities assemble. In temperate forests, host identity, biotic neighborhood,...

Despite its importance for forest regeneration, food webs, and human economies, changes in tree fecundity with tree size and age remain largely unknown. The allometric increase with tree diameter assumed in ecological models would substantially overestimate seed contributions from large trees if fecundity eventually declines with size. Current esti...

Plant hybridization is common and important in ecological and economic contexts, however little is known about the impact of plant hybridization on ectomycorrhizal fungal (EMF) communities in natural habitats. We used a Populus hybrid system (P. angustifolia x P. fremontii) in a heterogeneous riparian landscape to address the hypothesis that EMF co...

Microgeographic genetic divergence can create fine-scale trait variation. When such divergence occurs within foundation species, then it might impact community structure and ecosystem function and cause other cascading ecological effects. We tested for parallel microgeographic trait and genetic divergence in Spartina alterniflora, a foundation spec...

Efforts to maintain the function of critical ecosystems under climate change often begin with foundation species. In the southwestern US, cottonwood trees support diverse communities in riparian ecosystems that are threatened by rising temperatures. Genetic variation within cottonwoods shapes communities and ecosystems, but these effects may be mod...

Macrosystems ecology is an emerging science that aims to integrate traditionally distinct disciplines to predict how hierarchical interacting processes influence the emergence of complex patterns across local to regional and global scales. Despite increased focus on cross-scale relationships and cross-disciplinary integration, few macroecology stud...

Restoration treatments in Bromus tectorum (cheatgrass)-invaded sagebrush habitat has often produced poor results. This is perhaps due to multifaceted ecological changes associated with cheatgrass invasion like reduced water availability, altered nutrient availability, and shifts in soil microbial communities. We tested whether suppressing cheatgras...

A Correction to this paper has been published: https://doi.org/10.1038/s41467-021-22025-2

Indirect climate effects on tree fecundity that come through variation in size and growth (climate-condition interactions) are not currently part of models used to predict future forests. Trends in species abundances predicted from meta-analyses and species distribution models will be misleading if they depend on the conditions of individuals. Here...

Widespread tree species span large climatic gradients that often lead to high levels of local adaptation and phenotypic divergence across their range. To evaluate the relative roles of selection and drift in driving divergence in phenotypic traits, we compared molecular and quantitative genetic variation in Populus fremontii (Fremont cottonwood), u...

Several recent studies have documented how fire severity affects the density and spatial patterns of tree regeneration in western North American ponderosa pine forests. However, less is known about the effects of fire severity on fine-scale tree regeneration niche attributes such as understory plant composition and cover, surface fuel abundance, an...

Abstract Many plants are becoming increasingly maladapted to their environments due to changing climate and environmental conditions. It is, therefore, important to quantitatively evaluate what species, populations, and genotypes will survive in projected climate change scenarios and the implications this can have for associated biodiversity. We ev...

1.The coordination of traits from individual organs to whole plants is under strong selection because of environmental constraints on resource acquisition and use. However, the tight coordination of traits may provide underlying mechanisms of how locally adapted plant populations can become maladapted because of climate change. 2.To better understa...

Premise: Root-associated fungi provide a wide range of functions for their host plants, including nutrient provisioning, pathogen protection, and stress alleviation. In so doing, they can markedly influence host-plant structural and physiological traits, although the degree to which these effects vary within particular plant host species is not we...

Changing climates can cause shifts in temperature and precipitation, resulting in warming and drought in some regions. Although each of these factors has been shown to detrimentally affect forest ecosystems worldwide, information on the impacts of the combined effects of warming and drought is lacking. Forest trees rely on mutualistic root-associat...

Populus fremontii (Fremont cottonwood) is recognized as one of the most important foundation tree species in the southwestern USA and northern Mexico because of its ability to structure communities across multiple trophic levels, drive ecosystem processes and influence biodiversity via genetic-based functional trait variation. However, the areal ex...

Changes in temperature and moisture as a result of climate forcing can impact performance of planted trees. Tree performance may also be sensitive to new soil conditions, for example, brought about by seeds germinating in soils different from those colonized by ancestral populations. Such “edaphic constraint” may occur with natural migration or hum...

The importance of considering mycorrhizal communities in pinyon pine forest ecosystems.

Zahra S, Hofstetter RW, Waring KM, Gehring C. 2020. Review: The invasion of Acacia nilotica in Baluran National Park, Indonesia, and potential future control strategies. Biodiversitas 21: 104-116. Acacia nilotica, commonly called prickly acacia, is infamous for its ability to invade various ecosystems, especially savannah. The tree was introduced t...

Plant-fungal symbioses can have strong consequences for ecological communities and are sensitive to variation in abiotic factors. While the functions of mycorrhizal fungi are well established, the role of other root-colonizing fungi such as dark septate endophytes (DSE), which lack specialized structures for nutrient transfer, are less clear. DSE a...

Over the past three decades, wildfires in southwestern US ponderosa pine (Pinus ponderosa Lawson & C. Lawson) forests have increased in size and severity. These wildfires can remove large, contiguous patches of mature forests, alter dominant plant communities and increase woody debris, potentially altering fungal community composition. Additionally...

Grazers and the AM symbiosis share a long evolutionary history, grazing effects on arbuscular mycorrhizal (AM) symbioses remain unresolved despite decades of dedicated research. Studies show fungal growth to increase, decrease and remain unchanged in response to grazing pressure. We argue that studies focusing on single fungal traits may fail to de...

Successive droughts have resulted in extensive tree mortality in the southwestern United States. Recovery of these areas is dependent on the survival and recruitment of young trees. For trees that rely on ectomycorrhizal fungi (EMF) for survival and growth, changes in soil fungal communities following tree mortality could negatively affect seedling...

Global climate change is having profound and widespread effects on plant growth and survival. For the southwestern United States, warmer temperatures, more variable precipitation and more extreme droughts are expected. As plant populations experience these changes they may adapt and persist in place or may experience increasing environmental stress...

Observations resulting from an increased scrutiny of seed-borne microbes are challenging our traditional concepts of endophyte transmission, but few of these studies have focused on trees, particularly the conifers that dominate many forested ecosystems. We reviewed the literature on pine seed endophytes and examined two pine species, pinyon (Pinus...

Worldwide, trees are confronting increased temperature and aridity, exacerbating susceptibility to herbivory. Long-term studies comparing patterns of plant performance through drought can help identify variation among and within populations in vulnerability to climate change and herbivory. We use long-term monitoring data to examine our overarching...

Understanding how genetic-based traits of plants interact with climate to affect associated communities will help improve predictions of climate change impacts on biodiversity. However, few community-level studies have addressed such interactions. Pinyon pine (Pinus edulis) in the southwestern U.S. shows genetic-based resistance and susceptibility...

In the original published version of the article, the description of the fixed-effect predictor Inoculum Complexity presented in the Methods was incorrect. The incorrect description given was: “single fungal genus, multiple fungal genera, or whole soil inoculum”. The correct description is: “single fungal species, multiple fungal species, or whole...

Most plants engage in symbioses with mycorrhizal fungi in soils and net consequences for plants vary widely from mutualism to parasitism. However, we lack a synthetic understanding of the evolutionary and ecological forces driving such variation for this or any other nutritional symbiosis. We used meta-analysis across 646 combinations of plants and...

The interactions among climate change, plant genetic variation and fungal mutualists are poorly understood, but probably important to plant survival under drought. We examined these interactions by studying the ectomycorrhizal fungal (EMF) communities of pinyon pine seedlings (Pinus edulis) planted in a wildland ecosystem experiencing two decades o...

Aim At continental scales, abiotic factors such as climate are typically used to explain differences in plant ranges. Although biotic interactions also underlie the biogeography of plants, the importance of plant‐associated microbes is often overlooked when predicting ranges. In particular, symbiotic microbes may influence the distribution of plant...

High temperatures associated with climate change are expected to be detrimental for aspects of plant reproduction, such as pollen viability. We hypothesized that (1) higher peak temperatures predicted with climate change would have a minimal effect on pollen viability, while high temperatures during pollen germination would negatively affect pollen...

Local adaptation, the differential success of genotypes in their native versus foreign environments, can influence ecological and evolutionary processes, yet its importance is difficult to estimate because it has not been widely studied, particularly in the context of interspecific interactions. Interactions between ectomycorrhizal (EM) fungi and t...

This report reviews important advances in mycorrhizal research that occurred during the past 2 years. We highlight major advancements both within and across levels of biological organization and describe areas where greater integration has led to unique insights. Particularly active areas of research include exploration of the mechanisms underpinni...

An increasingly recognized impact of plant invaders is the disruption of positive interactions between native plants and their belowground mutualistic mycorrhizal fungi. We reviewed 112 studies from 61 publications that report invader impacts on mycorrhizal fungi. We describe emerging patterns on the frequency of negative, neutral and positive inva...

Significance Soil microbes influence plant performance and may be critical to the persistence of some plants with climate change. However, microbes are highly diverse, and individuals of the same plant species often associate with different microbes. We examined the importance of soil microbes to the growth and survival of a widespread pine under d...

Although hybridization in plants has been recognized as an important pathway in plant speciation, it may also affect the ecology and evolution of associated communities. Cottonwood species (Populus angustifolia and P. fremontii) and their naturally occurring hybrids are known to support different plant, animal, and microbial communities, but no stu...

Experiments with plant species that can host both arbuscular mycorrhizal fungi (AMF) and ectomycorrhizal fungi (EMF) are important to separating the roles of fungal type and plant species and understanding the influence of the types of symbioses on plant growth and nutrient acquisition. We examined the effects of mycorrhizal fungal type on the grow...

Soil structure, soil salinity, and soil water-holding capacity are tightly interconnected traits, all of which can be influenced by mycorrhizal fungi. This introduction reviews basic information about these three soil properties and their importance in a changing world. It sets the stage for subsequent chapters that consider the interrelationships...

As the Earth's climate changes, droughts are expected to become more intense, with consequences for plants and mycorrhizal fungi. We review recent studies examining the effects of drought on mycorrhizal fungi and the influence of mycorrhizal fungi on host plant–water relationships and drought tolerance. We also examine the consequences of drought-i...

Diversity of complex microbial communities can be rapidly assessed by community amplicon sequencing of marker genes (e.g., 16S), often yielding many thousands of DNA sequences per sample. However, analysis of community amplicon sequencing data requires multiple computational steps which affect the outcome of a final data set. Here we use mock commu...

The diversity of complex microbial communities can be rapidly assessed by high-throughput DNA sequencing of marker gene (e.g., 16S) PCR amplicon pools, often yielding many thousands of DNA sequences per sample. However, analysis of such community amplicon sequencing data requires multiple computational steps which affect the outcome of a final data...

Natural selection as a result of plant-plant interactions can lead to local biotic adaptation. This may occur where species frequently interact and compete intensely for resources limiting growth, survival, and reproduction. Selection is demonstrated by comparing a genotype interacting with con- or hetero-specific sympatric neighbor genotypes with...

Diversity of complex microbial communities can be rapidly assessed by community amplicon sequencing of marker genes (e.g., 16S), often yielding many thousands of DNA sequences per sample. However, analysis of community amplicon sequencing data requires multiple computational steps which affect the outcome of a final data set. Here we use mock commu...

Although the eco-evolutionary dynamics of multicellular organisms are intertwined with the microorganisms that colonize them, there is only a rudimentary understanding of how a host's genotype influences its microbiome. We utilize Populus angustifolia to test whether communities of essential symbionts, ectomycorrhizal fungi (EMF), vary among host g...

Diversity of complex microbial communities can be rapidly assessed by community amplicon sequencing of marker genes (e.g., 16S), often yielding many thousands of DNA sequences per sample. However, analysis of community amplicon sequencing data requires multiple computational steps which affect the outcome of a final data set. Here we use mock commu...

Background: Local adaptation, the differential success of genotypes in their native versus foreign environment, arises from various evolutionary processes, but the importance of concurrent abiotic and biotic factors as drivers of local adaptation has only recently been investigated. Local adaptation to biotic interactions may be particularly impor...

Mycorrhizal associations are recognized as key symbioses in a changing world, yet our understanding of their geographic distribution and temporal dynamics remains limited. We combined data on mycorrhizal associations and historical dominant vegetation to map the pre-European Settlement mycorrhizal associations of the conterminous United States of A...

Forest and woodland ecosystems may be strongly affected by climate change influences on tree population processes such as seed production and seedling recruitment. Yet climate effects on seed production are generally poorly understood, particularly for trees that exhibit masting behavior (i.e. high synchronicity and high inter-annual variability in...

Plants form belowground associations with mycorrhizal fungi in one of the most common symbioses on Earth. However, few large-scale generalizations exist for the structure and function of mycorrhizal symbioses, as the nature of this relationship varies from mutualistic to parasitic and is largely context-dependent. We announce the public release of...