81 research outputs found
Spatial Heterogeneity in Soil Microbes Alters Outcomes of Plant Competition
Plant species vary greatly in their responsiveness to nutritional soil mutualists, such as mycorrhizal fungi and rhizobia, and this responsiveness is associated with a trade-off in allocation to root structures for resource uptake. As a result, the outcome of plant competition can change with the density of mutualists, with microbe-responsive plant species having high competitive ability when mutualists are abundant and non-responsive plants having high competitive ability with low densities of mutualists. When responsive plant species also allow mutualists to grow to greater densities, changes in mutualist density can generate a positive feedback, reinforcing an initial advantage to either plant type. We study a model of mutualist-mediated competition to understand outcomes of plant-plant interactions within a patchy environment. We find that a microbe-responsive plant can exclude a non-responsive plant from some initial conditions, but it must do so across the landscape including in the microbe-free areas where it is a poorer competitor. Otherwise, the non-responsive plant will persist in both mutualist-free and mutualist-rich regions. We apply our general findings to two different biological scenarios: invasion of a non-responsive plant into an established microbe-responsive native population, and successional replacement of non-responders by microbe-responsive species. We find that resistance to invasion is greatest when seed dispersal by the native plant is modest and dispersal by the invader is greater. Nonetheless, a native plant that relies on microbial mutualists for competitive dominance may be particularly vulnerable to invasion because any disturbance that temporarily reduces its density or that of the mutualist creates a window for a non-responsive invader to establish dominance. We further find that the positive feedbacks from associations with beneficial soil microbes create resistance to successional turnover. Our theoretical results constitute an important first step toward developing a general understanding of the interplay between mutualism and competition in patchy landscapes, and generate qualitative predictions that may be tested in future empirical studies
Decline of an Ecotone Forest: 50 Years of Demography in the Southern Boreal Forest
Variation in tree recruitment, mortality, and growth can alter forest community composition and structure. Because tree recruitment and mortality events are generally infrequent, longâtime scales are needed to confirm trends in forests. We performed a 50âyr demographic census of a forest plot located on the southern edge of the Canadian boreal forest, a region currently experiencing forest dieâback in response to direct and indirect effects of recent severe droughts. Here, we show that over the last 30 yr biomass, basal area, growth, and recruitment have decreased along with a precipitous rise in mortality across the dominant tree species. The stand experienced periods of drought in combination with multiple outbreaks of forest tent caterpillar (Malacosoma disstria) and bark beetles. These insect disturbances interacted to increase mortality rates within the stand and decrease stand density. The interaction of endogenous and exogenous factors may shift forests in this region onto novel successional trajectories with the possibility of changes in regional vegetation type
Beyond the black box: promoting mathematical collaborations for elucidating interactions in soil ecology
This work is licensed under a Creative Commons Attribution 4.0 International License.Understanding soil systems is critical because they form the structural and nutritional foundation for plants and thus every terrestrial habitat and agricultural system. In this paper, we encourage increased use of mathematical models to drive forward understanding of interactions in soil ecological systems. We discuss several distinctive features of soil ecosystems and empirical studies of them. We explore some perceptions that have previously deterred more extensive use of models in soil ecology and some advances that have already been made using models to elucidate soil ecological interactions. We provide examples where mathematical models have been used to test the plausibility of hypothesized mechanisms, to explore systems where experimental manipulations are currently impossible, or to determine the most important variables to measure in experimental and natural systems. To aid in the development of theory in this field, we present a table describing major soil ecology topics, the theory previously used, and providing key terms for theoretical approaches that could potentially address them. We then provide examples from the table that may either contribute to important incremental developments in soil science or potentially revolutionize our understanding of plantâsoil systems. We challenge scientists and mathematicians to push theoretical explorations in soil systems further and highlight three major areas for the development of mathematical models in soil ecology: theory spanning scales and ecological hierarchies, processes, and evolution
Beyond the black box: Promoting mathematical collaborations for elucidating interactions in soil ecology
© 2019 The Authors. Understanding soil systems is critical because they form the structural and nutritional foundation for plants and thus every terrestrial habitat and agricultural system. In this paper, we encourage increased use of mathematical models to drive forward understanding of interactions in soil ecological systems. We discuss several distinctive features of soil ecosystems and empirical studies of them. We explore some perceptions that have previously deterred more extensive use of models in soil ecology and some advances that have already been made using models to elucidate soil ecological interactions. We provide examples where mathematical models have been used to test the plausibility of hypothesized mechanisms, to explore systems where experimental manipulations are currently impossible, or to determine the most important variables to measure in experimental and natural systems. To aid in the development of theory in this field, we present a table describing major soil ecology topics, the theory previously used, and providing key terms for theoretical approaches that could potentially address them. We then provide examples from the table that may either contribute to important incremental developments in soil science or potentially revolutionize our understanding of plant-soil systems. We challenge scientists and mathematicians to push theoretical explorations in soil systems further and highlight three major areas for the development of mathematical models in soil ecology: Theory spanning scales and ecological hierarchies, processes, and evolution
LSST: from Science Drivers to Reference Design and Anticipated Data Products
(Abridged) We describe here the most ambitious survey currently planned in
the optical, the Large Synoptic Survey Telescope (LSST). A vast array of
science will be enabled by a single wide-deep-fast sky survey, and LSST will
have unique survey capability in the faint time domain. The LSST design is
driven by four main science themes: probing dark energy and dark matter, taking
an inventory of the Solar System, exploring the transient optical sky, and
mapping the Milky Way. LSST will be a wide-field ground-based system sited at
Cerro Pach\'{o}n in northern Chile. The telescope will have an 8.4 m (6.5 m
effective) primary mirror, a 9.6 deg field of view, and a 3.2 Gigapixel
camera. The standard observing sequence will consist of pairs of 15-second
exposures in a given field, with two such visits in each pointing in a given
night. With these repeats, the LSST system is capable of imaging about 10,000
square degrees of sky in a single filter in three nights. The typical 5
point-source depth in a single visit in will be (AB). The
project is in the construction phase and will begin regular survey operations
by 2022. The survey area will be contained within 30,000 deg with
, and will be imaged multiple times in six bands, ,
covering the wavelength range 320--1050 nm. About 90\% of the observing time
will be devoted to a deep-wide-fast survey mode which will uniformly observe a
18,000 deg region about 800 times (summed over all six bands) during the
anticipated 10 years of operations, and yield a coadded map to . The
remaining 10\% of the observing time will be allocated to projects such as a
Very Deep and Fast time domain survey. The goal is to make LSST data products,
including a relational database of about 32 trillion observations of 40 billion
objects, available to the public and scientists around the world.Comment: 57 pages, 32 color figures, version with high-resolution figures
available from https://www.lsst.org/overvie
Home-field advantage? evidence of local adaptation among plants, soil, and arbuscular mycorrhizal fungi through meta-analysis
Ecological separation among fern species in an old-growth forest
The validity of niche-assembly rules in explaining community structure is revisited by testing for ecological separation among ferns. An intensive, fine-scale survey of fern abundance and environmental variation was done in 1-ha of old-growth forest. Three methods of detecting niche segregation (canonical correspondence analysis, detrended correspondence analysis and GIS mapping) suggested that most fern species at the site are distributed according to distinct environmental preferences. The most important gradients separating fern species are first, the amount of soil moisture and second, soil nitrate concentration. Contrary to other findings, pH had little influence on controlling fern distribution. Spatial autocorrelation, detected by partialled ordinations, obscured the presence of niche partitioning. As well, sampling grain changed the apparent location of some species on environmental gradients and their ecological similarity to other species. Finer-scaled environmental heterogeneity or dispersal-mediated processes may account for the unexplained variation in fern species abundance of this site
Sensitivity in growth responses of tree seedlings to variation in identity and abundance of ectomycorrhizal fungi
Interdependent organisms such as trees and ectomycorrhizal fungi are described as coevolved. Partner species in coevolved interactions are expected to be sensitive to intraspecific variation of each partner due to the intimate and interdependent nature of their interactions. In this thesis, I considered specific aspects of variation in each of the ectomycorrhizal partners and how this variation influenced the other partner. In particular, I used experimental and meta-analytical approaches to evaluate (1) how colonization levels, regardless of ectomycorrhizal fungal taxon, correlated to host growth; (2) how ectomycorrhizal fungi differentially influenced growth of different genera of plant hosts, and (3) how variation in growth of a single host species was correlated to the composition of ectomycorrhizal fungal communities in various soil environments. Because controlling for and manipulating ectomycorrhizal fungi on host plants is integral to these questions, I also tested the efficacy of two methods to control colonization by ectomycorrhizal fungi on host plants and found that fungicides and mesh can be effective barriers to colonization. Results from the meta-analysis and experiments indicated that colonization levels did not consistently scale with host growth response, however, suggesting that colonization levels may not be an ecologically useful factor to gauge the growth responses of host plants to ectomycorrhizal fungi. In addition, there was little sensitivity in growth responses of host plants to variation in the identity of ectomycorrhizal fungi. Seedlings across multiple host genera increased in biomass and shoot height when inoculated with ectomycorrhizal fungi regardless of the identity of the fungal associate. When ectomycorrhizas were considered in a multi-specific context (i.e. one host species associated with a community of ectomycorrhizal fungi), variation in host shoot properties was not correlated with species composition of the community of ectomycorrhizal fungi on their roots but rather appeared to be coupled to edaphic conditions. These results indicate that the variation in ectomycorrhizal fungi perceived and selected for by the host plant may be of a discrete (presence/absence of ectomycorrhizal fungi) rather than continuous nature (variation in identity or abundance of ectomycorrhizal fungi).Science, Faculty ofBotany, Department ofGraduat
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