Michael F Allen

Michael F Allen
University of California, Riverside | UCR · Microbiology and Plant Pathology

About

208
Publications
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Publications

Publications (208)
Article
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Mycorrhizal fungi enable plants to thrive in the cold, waterlogged, organic soils of boreal peatlands and, with saprotrophic fungi, largely contribute to the sequestration of atmospheric carbon in peat. Hence, fungi support the contribution of peatlands to global climate regulation, on which society depends. Here, we used high‐resolution minirhizot...
Article
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Soil CO2 concentrations and emissions from tropical forests are modulated seasonally by precipitation. However, sub‐seasonal responses to meteorological events (for example, storms, drought) are less well‐known. Here we present the effects of meteorological variability on short‐term (hours to months) dynamics of soil CO2 concentrations and emission...
Article
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Premise: Flexible phenological responses of invasive plants under climate change may increase their ability to establish and persist. A key aspect of plant phenology is the timing of root production, how it coincides with canopy development and subsequent water-use. The timing of these events within species and across communities could influence t...
Article
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A significant challenge for understanding how fungal communities may change in the Anthropocene are the multiple aspects of simultaneous environmental change. To address this challenge, we used a seven-year multi-factorial field experiment in southern California to examine how root-associated fungi respond to aridity, nitrogen deposition, and plant...
Article
The Salton Sea Basin in California suffers from poor air quality, and an expanding dry lakebed (playa) presents a new potential dust source. In 2017-18, depositing dust was collected ~monthly at five sites in the Salton Sea Basin and analyzed for total elemental and soluble anion content. These data were analyzed with Positive Matrix Factorization...
Article
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The strategic engineering of solar energy technologies—from individual rooftop modules to large solar energy power plants—can confer significant synergistic outcomes across industrial and ecological boundaries. Here, we propose techno–ecological synergy (TES), a framework for engineering mutually beneficial relationships between technological and e...
Article
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1. Solar energy could become the largest energy source by 2050. There is a new model for engineering solar energy systems that maximizes both technological and ecological benefits. 2. Scientists call this type of installation a "techno-ecological synergy," and there are over 15 different types of these installations that can be developed, including...
Article
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Global atmospheric methane growth rates have wildly fluctuated over the past three decades, which may be driven by the proportion of tropical land surface saturated by water. The El Niño/Southern Oscillation Event (ENSO) cycle drives large‐scale climatic trends globally, with El Niño events typically bringing drier weather than La Niña. In a lowlan...
Article
1.Leaf‐cutter ants are a prominent feature in Neotropical ecosystems but a comprehensive assessment of their effects on ecosystem functions is lacking. We reviewed the literature and used our own recent findings to identify knowledge gaps and develop a framework to quantify the effects of leaf‐cutter ants on ecosystem processes. 2.Leaf‐cutter ant...
Article
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Fungal community composition in the Anthropocene is driven by rapid changes in environmental conditions caused by human activities. This study examines the relative importance of two global change drivers – atmospheric nitrogen (N) deposition and annual grass invasion – on structuring fungal communities in a California chaparral ecosystem, with emp...
Article
Professor Martha Christensen, an international leader in fungal systematics and ecology, died on 19 March 2017. Martha was a professor of mycology in the Department of Botany at the University of Wyoming in Laramie. A recognized expert on the ecology and systematics of soil-dwelling fungi, Professor Martha Christensen’s 85 years were filled with st...
Article
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Leaf‐cutter ants are dominant herbivores that disturb the soil and create biogeochemical hot spots. We studied how leaf‐cutter ant Atta cephalotes impacts soil CO2 dynamics in a wet Neotropical forest. We measured soil CO2 concentration monthly over 2.5 years at multiple depths in non‐nest and nest soils (some of which were abandoned during the stu...
Article
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Rapid responses of microbial biomass and community composition following a precipitation event have been reported for soil bacteria and fungi, but measurements characterizing ectomycorrhizal fungi remain limited. The response of ectomycorrhizal fungi after a precipitation event is crucial to understanding biogeochemical cycles and plant nutrition....
Preprint
Full-text available
Fungal community composition in the Anthropocene is driven by rapid changes in environmental conditions caused by human activities. This study examines the relative importance of two global change drivers - atmospheric nitrogen (N) deposition and annual grass invasion - on structuring fungal communities in a California chaparral ecosystem, with emp...
Article
The US and Mexico share a common history in many areas, including language and culture. They face ecological changes due to the increased frequency and severity of droughts and rising energy demands; trends that entail economic costs for both nations and major implications for human well being. We describe an ongoing effort by the Environment Worki...
Chapter
Mycorrhizae are symbiotic mutualisms between plants and fungi, in which carbon is exchanged for nutrients. The eruption of Mount St. Helens was a large event that covered a topographically complex land area with disturbances of varying intensity that altered survival of soil organisms. Animals from rodents to elk fed upon and transported mycorrhiza...
Article
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Land-cover change from energy development, including solar energy, presents trade-offs for land used for the production of food and the conservation of ecosystems. Solar energy plays a critical role in contributing to the alternative energy mix to mitigate climate change and meet policy milestones; however, the extent that solar energy development...
Chapter
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Globally, overall demand for agricultural products is expected to grow at 1.1% per year from 2005/2007-2050, down from 2.2% per year in the past four decades (Alexandratos and Bruinsma, 2012). Population growth, increases in per-capita consumption, and changes in diets leading to the consumption of more livestock products are the main drivers of ex...
Article
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Many species have already experienced distributional shifts due to changing environmental conditions, and analyzing past shifts can help us to understand the influence of environmental stressors on a species as well as to analyze the effectiveness of conservation strategies. We aimed to (1) quantify regional habitat associations of the California g...
Chapter
Mycorrhizal fungi consume a large sink of carbon fixed by plants and supply a large fraction of nutrients. But there are a number of complex mechanisms for acquisition and transport that can vary in space and time. Global change is resulting in a general warming process caused by an anthropogenic elevated carbon dioxide (CO2) and increasing deposit...
Article
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Anthropogenic nitrogen (N) deposition represents a significant N input for many terrestrial ecosystems. N deposition can affect plants on scales ranging from photosynthesis to community composition, yet few studies have investigated how changes in N availability affect plant water relations. We tested the effects of N addition on plant water relati...
Chapter
The unique structure and physiology of fungi make them sensitive and resilient in the face of natural disturbance. The impact of disturbance on a fungal community depends on the disturbance type, scale, and frequency. As fungi play key roles in nutrient turnover and plant nutrition, disturbances alter the fungal community feedback to impact ecosyst...
Article
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While highway underpasses and culverts are often identified in conservation planning as wildlife corridors, their success at facilitating connectivity in deserts has rarely been tested. We evaluated wildlife use of seven, pre-existing highway underpass structures and four associated canyon sites over 29 mo to identify spatial and temporal wildlife...
Article
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Decisions determining the use of land for energy are of exigent concern as land scarcity, the need for ecosystem services, and demands for energy generation have concomitantly increased globally. Utility-scale solar energy (USSE) [i.e., ≥1 megawatt (MW)] development requires large quantities of space and land; however, studies quantifying the effec...
Conference Paper
Background/Question/Methods Anthropogenic nitrogen (N) deposition represents a significant N input for many semi-arid ecosystems, including southern California. N deposition can alter plant communities, resulting in species composition shifts and reduced diversity. On a smaller scale, increased N availability can strongly affect photosynthesis. F...
Conference Paper
Background/Question/Methods The evolution of invasiveness hypothesizes that genetic differentiation between introduced and native populations contributes to the success of exotic species. The mechanisms responsible for differentiation are founder effects, adaptation to novel environments, or admixture of previously separated populations. The form...
Conference Paper
Background/Question/Methods Ecological niche modelling is considered a valuable tool for predicting a species shift in geographical range. However, the typical use of this tool has been to predict shifts in species’ distributions based on expected future climatic changes, and the shifts in species’ distributions that have already occurred are ofte...
Conference Paper
Background/Question/Methods Globally, fungi are the second largest terrestrial group of organisms and produce a large fraction of stable organic matter. But, fungal production and turnover are poorly understood, especially in different environments. I used our Soil Observatory System (a robotic automated minirhizotron coupled to a soil sensor net...
Conference Paper
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Background/Question/Methods Soil inorganic carbon (SIC), in the form of CaCO3, is among the largest pools of carbon in the western US and is ubiquitous in arid regions worldwide. Caliche, a secondary carbonate as CaCO3, precipitates when meteoric water, respired CO2, and calcium react. Caliche is assumed to be stable, but the potential effects of...
Article
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Soils contain a large global pool of carbon. Mycorrhizal fungi comprise a large fraction of that pool but are highly dynamic. We utilized an in situ soil observatory to study fungal dynamics of a California mixed-forest ectomycorrhizal fungal (EMF) ecosystem. Across 2011, we observed fungal hyphae daily using an automated minirhizotron. Simultaneou...
Chapter
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Mycorrhizal symbioses are essential components of terrestrial ecosystems. These symbioses are intimate associations between plants and fungi where the plant fixes C, exchanging it for nutrients and water from fungal hyphae that permeate and explore surrounding soil. Perturbations, whether acute (such as disturbance or cutting) or chronic (global ch...
Article
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Nilpenia rossi new genus new species, described here from the Ediacara Member (Rawnsley Quartzite, South Australia), provides evidence of a Precambrian macroscopic sessile sediment-dweller. Nilpenia, ranging up to 30 cm in diameter, consists of two zones, a complex central area surrounded by radiating, dichotomously branching structures that decrea...
Article
[1] Trees and shrubs growing in California's mountains rely on deep roots to survive the hot and dry Mediterranean climate summer. The shallow montane soil cannot hold enough water to support summer transpiration, and plants must access deeper moisture from the weathered bedrock. We used the HYDRUS-1D model to simulate the moisture flux through the...
Article
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Seasonally dry tropical forests are dominated by deciduous and evergreen tree species with a wide range of leaf phenology. We hypothesized that Piscidia piscipula is able to extend leaf senescence until later in the dry season due to deeper and more reliable water sources than Gymnopodium floribundum, which loses leaves earlier in the dry season. P...
Conference Paper
Background/Question/Methods Phenological variation among coexisting species is an often overlooked and yet critically important factor in community assemblage and invasibility. Variation in community diversity can result solely from differences in the order of establishment or onset of growth. In plant communities early phenologies (e.g. the timi...
Data
Fig. S1In situ Soil Ecosystem Observatory images showing morphological differences between fine roots and arbuscular mycorrhizal (AM) fungal hyphae. Fig. S2 A subset of a time series of Soil Ecosystem Observatory images showing changes in arbuscular mycorrhizal (AM) fungal hyphae in one plot within a single day. Fig. S3 A Soil Ecosystem Observatory...
Article
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Arbuscular mycorrhizal (AM) fungi are the most abundant plant symbiont and a major pathway of carbon sequestration in soils. However, their basic biology, including their activity throughout a 24-h day : night cycle, remains unknown. We employed the in situ Soil Ecosystem Observatory to quantify the rates of diurnal growth, dieback and net product...
Article
Understanding the temporal variation of soil and root dynamics is a major step towards determining net carbon in ecosystems. We describe the installation and structure of an in situ soil observatory and sensing network consisting of an automated minirhizotron with associated soil and atmospheric sensors. Ectomycorrhizal hyphae were digitized daily...
Article
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Environmental scientists are increasing their capitalization on advancements in technology, computation, and data management. However, the extent of that capitalization is unknown. We analyzed the survey responses of 434 graduate students to evaluate the understanding and use of such advances in the environmental sciences. Two-thirds of the student...
Conference Paper
Background/Question/Methods Many invasive species exhibit more vigorous growth habits in introduced relative to native ranges. The classic explanation for such divergence in growth habits between ranges is the Enemy Release Hypothesis (ERH), which posits that introduced species benefit from an absence of coevolved enemies. A corollary of the ERH...
Article
Multiple processes are increasingly recognized as being responsible for species’ extinctions. We evaluated population extinctions between 1930 and 1998 for the endangered Quino checkerspot (Euphydryas editha quino) butterfly relative to agricultural history, human population growth, climate variability, topographical diversity, and wildflower abund...
Article
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Background and Aims With limited soil depth in northern Yucatán (<30 cm), roots grow deeper through rock fractures and dissolution karst features (i.e., cavities, including soil-filled ones known as soil pockets). We assessed the importance of limestone bedrock and dissolution karst features on tree root growth. Methods Fieldwork was conducted in...
Article
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Increased available soil nitrogen can increase biomass, lower species richness, alter soil chemistry and modify community structure in herbaceous ecosystems worldwide. Although increased nitrogen availability typically increases aboveground production and decreases species richness in mesic systems, the impacts of nitrogen additions on semiarid eco...
Conference Paper
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Background/Question/Methods Most plants have difficulty growing on shallow soils because rooting depth is insufficient for anchorage and water storage and nutrient pools are limited. Northern Yucatan is a limestone karst environment where shallow (<30 cm deep) stony soils are common. Nevertheless the weathering of bedrock promotes fractures and di...
Conference Paper
Background/Question/Methods Drought plays a major role in structuring communities. Microbes are also impacted. Yet fungal hyphae, especially those forming mycorrhizal associations remain active and respiring in the near surface environment despite extremely dry soils. Previously, we demonstrated that vertical spatial stratification in soil moisture...
Conference Paper
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Background/Question/Methods Expansion of urbanization and alternative energy resource development, along with the transportation and energy transmission infrastructure required to support those changes in land use, are fragmenting desert environments at an increasing rate. Habitat connectivity is a key component for successful conservation strate...
Article
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Despite their prominent role for tree growth, few studies have examined the occurrence of ectomycorrhizal fungi in lowland, seasonally dry tropical forests (SDTF). Although fruiting bodies of boletes have been observed in a dry tropical forest on the Northern Yucatan Peninsula, Mexico, their occurrence is rare and their mycorrhizal status is uncert...
Article
Anthropogenic habitat fragmentation typically precedes conservation planning; maintaining remaining linkages among core habitat areas can thus become a key conservation objective. Identifying linkages for dispersal and ensuring those linkages have long-term protection and management are challenging tasks for wildlife managers. These tasks can be es...
Article
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Soil fungi are important components of terrestrial ecosystems. They function as decomposers, pathogens, parasites, and mutualistic symbionts. Their main mode of dispersal is to liberate spores into the atmosphere. In this study we tested the hypothesis that a higher atmospheric CO2 concentration will induce greater sporulation in common soil fungi,...
Article
Bouteloua gracilis (H.B.K.) Lag ex Steud (blue grama) was grown in a defined medium with and without the vesicular–arbuscular mycorrhizal fungus Glomus fasciculatus for 50 days. Levels of gibberellin-like substances (GA) and a substance like abscisic acid (ABA) of mycorrhizal and nonmycorrhizal plants were measured using the barley half-seed bioass...
Article
Measurement of fine root production and turnover rate, the reciprocal of mean life span of a root population, is crucial to the understanding of the carbon cycle of an ecosystem as fine roots account for up to 30% of global terrestrial net primary production. Our goal was to characterize fine root production, mortality, standing crop, and turnover...
Article
Full-text available
Seasonally dry tropical forests (SDTF) are characterized by pronounced seasonality in rainfall, and as a result trees in these forests must endure seasonal variation in soil water availability. Furthermore, SDTF on the northern Yucatan Peninsula, Mexico, have a legacy of disturbances, thereby creating a patchy mosaic of different seral stages under...
Article
Responses of mature trees to chronic N additions are poorly understood in ecosystems with high seasonal and spatial variability. To determine the effects of increased N deposition on mature conifers, we fertilized a piñon-juniper woodland in New Mexico at a rate equivalent to the urban interface. Fertilization (10 g m−2 y−1) reduced numbers of myco...
Article
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Northern Yucatan is a dry tropical area where limestone karst terrain supports a subdeciduous forest that is critical for sustaining the local economy of Mayan people. The 5- to 10-m-deep vadose zone is characterized by shallow soils (< 30 cm thick) with frequent rock outcrops overlying limestone bedrock, which contains the aquifer. This limestone...
Article
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Soils play a critical role in the global carbon cycle, yet the biophysical factors regulating soil CO2 dynamics remain unclear. We combined high-frequency in situ observations of fine roots and ectomycorrhizal (EM) fungi with data from multiple soil sensor arrays to examine the biophysical interactions influencing soil CO2 production for one year i...
Article
Ecosystem processes are influenced by weather and climatic perturbations at multiple temporal scales with a large range of amplitudes and phases. Technological advances of automated biometeorological measurements provide the opportunity to apply spectral methods on continuous time series to identify differences in amplitudes and phases and relation...
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Monitoring trends in urbanization and land use related to population growth and changing social and economic conditions is an important tool for developing in land use and habitat conservation policy. We analyzed urbanization and agricultural land-use change in Riverside County, California from 1984 to 2002, comparing maps every two years on the ba...
Article
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Understanding and predicting the responses of plant communities to multiple overlapping disturbances remains a challenging task. Hurricane Wilma represents a large, yet infrequent type of disturbance that was superimposed on an existing disturbance gradient of time since fire. We examined disturbance and recovery patterns in response to these overl...
Article
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Plant and microbial use of nitrogen (N) can be simultaneously mutualistic and competitive, particularly in ecosystems dominated by mycorrhizal fungi. Our goal was to quantify plant uptake of organic and inorganic N across a broad latitudinal gradient of forest ecosystems that varied with respect to overstory taxon, edaphic characteristics, and domi...
Article
a b s t r a c t Bioclimatic models aimed assessing a species' sensitivity to climate change incorporate mean shifts in cli-mate variables; however the more acute threat to the persistence of species may result from increased frequency of extreme climatic events, including increased duration and severity of droughts. Here we assess climate-change se...
Article
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To better understand how management and restoration practices influence the response of terrestrial ecosystems to large-scale disturbances, it is critical to study above- and belowground effects. In this study, we examined the immediate effect of a major hurricane on aboveground forest structure, arbuscular mycorrhizae (AM) and belowground carbon p...
Article
Identifying variables that drive population dynamics is a critical component of conservation and guides decisions for maintaining sustainable populations. Our objective was to model spatial and temporal patterns of occurrence of reptiles across an aeolian sand landscape. We used a community framework based on dune geomorphology and wind-precipitati...