We assessed whether (1) arbuscular mycorrhizal colonization of roots (RC) and/or plant responses ... more We assessed whether (1) arbuscular mycorrhizal colonization of roots (RC) and/or plant responses to arbuscular mycorrhizae (MR) vary with plant phylogeny and (2) MR and RC can be more accurately predicted with a phylogenetic predictor relative to a null model and models with plant trait and taxonomic predictors. In a previous study, MR and RC of 95 grassland species were measured. We constructed a phylogeny for these species and found it explained variation in MR and RC. Next, we used multiple regressions to identify the models that most accurately predicted plant MR. Models including either phylogenetic or phenotypic and taxonomic information similarly improved our ability to predict MR relative to a null model. Our study illustrates the complex evolutionary associations among species and constraints of using phylogenetic information, relative to plant traits, to predict how a plant species will interact with AMF.
Upland oak forests in the ecotone between the eastern deciduous forest and the southern Great Pla... more Upland oak forests in the ecotone between the eastern deciduous forest and the southern Great Plains are threatened by encroachment of eastern redcedar (Juniperus virginiana) due to fire suppression. The rapid rate of encroachment caused concern about concomitant alterations of site characteristics including nutrient cycling and the soil microbial communities (SMC) that could lead to positive feedbacks reinforcing eastern redcedar encroachment. We studied eight upland oak forests across central and western Oklahoma with stands representing three levels of encroachment: oak-dominated, eastern redcedar-dominated, and an intermediate mixture of both species. We analyzed litter chemistry (carbon, lignin, and nitrogen), soil chemistry (soil organic matter, NH 4 N, NO 3-N, PO 4 , K, and pH), and profiled soil microbial communities using phospholipid fatty acid analysis (PLFA). Eastern redcedar encroachment was accompanied by reduced litter carbon along with higher levels of arbuscular mycorrhizal (AM) fungi while litter N was lower in mixed stands. However, we detected no change in soil chemistry. Our results indicate eastern redcedar encroachment in these upland oak forests reduced litter quality and altered the SMC through increases in AM fungi, a symbiont associated with eastern redcedar. These alterations may create positive soil-microbial feedbacks by reducing the fitness of the dominant oak species and facilitating rapid increase in eastern redcedar in this threatened, oak-dominated ecosystem.
Arbuscular mycorrhizal (AM) fungi can support the establishment of mycotrophic plants in new envi... more Arbuscular mycorrhizal (AM) fungi can support the establishment of mycotrophic plants in new environments. However, the role of mycorrhizal symbiosis in interactions between perennial and weedy annual plants is not well understood. In our current study, we examine how widespread generalist AM fungi and soil disturbance, including disturbance of AM fungal networks (CMNs), affect the performance of two late-successional perennial plants of Central Europe, Senecio jacobaea and Crepis biennis, co-occurring with weedy annual forbs, Conyza canadensis and Erigeron annuus. Although presence of weedy annual E. annuus or C. canadensis did not affect the performance of the paired perennials, AM fungi supported perennial C. biennis in competition with weedy annual E. annuus. However, this AM-aided underpinning was independent of disturbance of CMNs. Conversely, although AM fungi benefited perennial S. jacobaea, this did not affect its competitive abilities when grown with weedy annual C. canadensis. Similarly, soil disturbance, independent of AM fungal presence, improved plant tissue P and biomass production of S. jacobaea, but not its competitive abilities. Our results show AM fungi may be advantageous for perennial plants growing in competition with weedy annual plants. Therefore, maintaining healthy soils containing an abundance of AM fungi, may encourage late successional perennial plants, potentially limiting establishment of weedy annual plant species. The majority (> 60%) of land plants 1,2 , including most annual plant species 3-5 , form mycorrhizal interactions with arbuscular mycorrhizal (AM) fungi (Glomeromycotina; 6). AM fungi supply host plants with nutrients (especially phosphorus (P) 7) from the soil, aid in protecting against plant pathogens 8,9 , and potentially an array of other services in exchange for carbon from the host plant 10,11. For example, the AM fungus Gigaspora margarita, increased P uptake of maize by 55% 12. Further, under P-limiting soil conditions, AM fungi can be responsible for nearly all P uptake by the mycorrhizal host plant 13,14. These strong benefits often result in AM fungi affecting coexistence of plant species, and therefore the composition of plant communities 15-17. Therefore, these symbiotic fungi may enhance or prevent establishment of weedy annuals, or increase the competitive abilities, and thereby persistence, of perennial species. Both annual and perennial plant species generally form an association with AM fungi for competitive success 1-5. Likewise, AM fungal symbionts may be essential for naturalization and spreading of weedy annual plants, yet this has rarely been studied (although see 18-20). Weedy plant species are generally annuals representing the R strategy, and are typically facultative mycorrhizal 21,22. Facultative mycorrhizal plants form weak associations with AM fungi, can complete their life cycle in the absence of the symbiosis, and are generally characterized by low levels of AM fungal root colonization 21,22,24. The annual life history strategy and facultative AM association can be potentially beneficial in disturbed habitats where intact AM fungal communities and competition for resources are low. Perennials, in contrast, develop long-term life history strategies for competition for limited resources, as they survive for extended periods of time. Short-term strategies of annuals may be disadvantageous in established plant communities where hyphal networks connect individual perennial plants and transfer nutrients, mainly N and P, between plants (i.e., common mycorrhizal networks: CMNs 23). Commandeering these networks can increase competitiveness of some plants, allowing disproportionately greater benefits compared to symbiotic carbon costs.
Arbuscular mycorrhizal fungi (AMF) provide crucial support for the establishment of plants in nov... more Arbuscular mycorrhizal fungi (AMF) provide crucial support for the establishment of plants in novel environments. We hypothesized that the OTU/genus richness and diversity of soil‐ and root‐associated AMF associated with alien plant species in their exotic ranges are lower than those in their native ranges. We examined the root‐associated and soil‐dwelling AMF of 11 invasive plant species in their native and exotic ranges in the United States and Europe by DNA sequencing of the ITS2 locus. Examined root‐associated AMF assemblages were simplified, which manifested as the loss of several AMF genera in the exotic ranges of the plants. These fungal assemblages were also characterized by greater dominance and simplification of the fungal assemblages. The dominant fungal genera were present regardless of whether their host plants were in their native or exotic ranges. Interestingly, both the native and invaded soils hosted diverse local AMF assemblages. Therefore, alien plant invasions were not limited to soils with low AMF diversity. Some AMF taxa could be context‐dependent passengers rather than drivers of alien plant invasions. Further studies should identify functions of AMF missing or less abundant in roots of plants growing in exotic ranges.
to vegetative biomass. Cool-season C3 grasses, Koeleria pyramidata and Poa pratensis, accumulated... more to vegetative biomass. Cool-season C3 grasses, Koeleria pyramidata and Poa pratensis, accumulated more biomass and were a significantly greater proportion of total community biomass in mycorrhizal-suppressed microcosms. Forbs showed variable responses to mycorrhizal suppression. The two legumes Amorpha canescens and Dalea purpurea had significantly lower survivorship in the fungicide-treated microcosms, relative to the controls. The results confirm the high mycorrhizal dependency and growth responsiveness of dominant prairie grasses, and indicate that differential growth and demographic responses to mycorrhizal colonization among species may significantly affect plant productivity and species relative abundances in tallgrass prairie.
BackgroundGrasslands are globally imperiled, facing continued threats from anthropogenic disturba... more BackgroundGrasslands are globally imperiled, facing continued threats from anthropogenic disturbances. Seeding remains a common grassland restoration method, and yet, is typically met with limited success, partially because soils of degraded systems inhibit the germination of native species.MethodsWe assessed the germination success of 16 native grassland species sown in soils collected from a degraded grassland converted into a nonnative warm‐season perennial grass, Bothriochloa ischaemum, and areas previously subjected to the eradication of this nonnative species. Our objectives were as follows: (1) determine native seed germination in soils collected from B. ischaemum or eradication control sites, compared to germination in native grassland soil, and (2) assess if native soil inoculation improves germination, compared to germination in degraded soils without inoculation.ResultsGermination of native species was exceedingly low when seeded into soil dominated by B. ischaemum, or in...
Elevated temperatures and drought may exacerbate invasion success of non-native grasses, as non-n... more Elevated temperatures and drought may exacerbate invasion success of non-native grasses, as non-native species often possess traits favored by a warmer, drier world. In our study, we assessed plant traits potentially linked to invasion success under elevated temperature and drought, including biomass production, reproductive allocation, arbuscular mycorrhizal (AM) fungal root colonization, and germination of native grasses and non-native invasive grasses. We selected two caespitose warm-season grasses [native (Schizachyrium scoparium) and non-native (Bothriochloa ischaemum)] and two cool-season grasses [native (Pascopyrum smithii) and non-native (Bromus inermis)]. Plant biomass, reproductive effort, and AM fungal colonization were assessed at two temperatures (ambient or elevated) and four levels of soil water-availability; germination was assessed at two temperatures and three levels of soil water-availability. Non-native warm- and cool-season grasses produced greater vegetative biomass, initiated seed production more frequently, and displayed greater germination when grown under elevated temperature and drought, compared to their paired native counterparts. Percent AM fungal root colonization of the non-native grasses was generally greater than native grasses regardless of soil moisture or elevated temperature. Our results suggest that under warmer and drier conditions non-native grasses will continue to outperform native species, due to greater biomass production, germination capabilities, and colonization by AM fungi.
In a globalized world, plant invasions are common challenges for native ecosystems. Although a co... more In a globalized world, plant invasions are common challenges for native ecosystems. Although a considerable number of invasive plants form arbuscular mycorrhizae, interactions between arbuscular mycorrhizal (AM) fungi and invasive and native plants are not well understood. In this study, we conducted a greenhouse experiment examining how AM fungi affect interactions of co-occurring plant species in the family Asteracea, invasive Echinops sphaerocephalus and native forb of central Europe Inula conyzae. The effects of initial soil disturbance, including the effect of intact or disturbed arbuscular mycorrhizal networks (CMNs), were examined. AM fungi supported the success of invasive E. sphaerocephalus in competition with native I. conyzae, regardless of the initial disturbance of CMNs. The presence of invasive E. sphaerocephalus decreased mycorrhizal colonization in I. conyzae, with a concomitant loss in mycorrhizal benefits. Our results confirm AM fungi represent one important mechan...
The plant microbiome is critical to plant health and is degraded with anthropogenic disturbance. ... more The plant microbiome is critical to plant health and is degraded with anthropogenic disturbance. However, the value of re‐establishing the native microbiome is rarely considered in ecological restoration. Arbuscular mycorrhizal (AM) fungi are particularly important microbiome components, as they associate with most plants, and later successional grassland plants are strongly responsive to native AM fungi. With five separate sites across the United States, we inoculated mid‐ and late successional plant seedlings with one of three types of native microbiome amendments: (a) whole rhizosphere soil collected from local old‐growth, undisturbed grassland communities in Illinois, Kansas or Oklahoma, (b) laboratory cultured AM fungi from these same old‐growth grassland sites or (c) no microbiome amendment. We also seeded each restoration with a diverse native seed mixture. Plant establishment and growth was followed for three growing seasons. The reintroduction of soil microbiome from native...
summaryIn order to determine whether variation in root system architecture can be said to be adap... more summaryIn order to determine whether variation in root system architecture can be said to be adaptive, it is necessary' to be able to define the costs and benefits of particular architectures. A simulation model of root growth is described that allows the development of root systems varying in several important architectural features, including topology, link lengths and radii, and branching angles. The program also estimates the exploitation efficiency of each root system, as the ratio of the volume of soil occupied by depletion zones (allowing for overlaps between competing roots) and the volume of tissue required to construct the system. Output from the model shows that high exploitation efficiency is associated with a herringbone topology (where branching is predominantly on the main axis) and with long interior and exterior links, although all these characteristics are associated with large tissue volumes and hence high construction cost, We predict, therefore, that such ‘e...
Prescribed burning is commonly used in forests to reduce fuel load, prevent encroachment of exoti... more Prescribed burning is commonly used in forests to reduce fuel load, prevent encroachment of exotic species, maintain biological diversity and improve wildlife habitat. The low intensity burns that are conducted at intervals of 1-10 years may have long-term effects on the abiotic and biotic components of the soil. We assessed how prescribed burning altered litter, soil physical and chemical properties, and soil microbial communities in upland oak forests subjected to prescribed burning at frequencies of 0 (unburned), 2.5 and 5 fires per decade (FPD) over a 20 year period. Prescribed burning at 5 FPD reduced soil organic matter by 60% and soil organic carbon by 64% and increased bulk density by 20%. Compared to unburned controls, litter nitrogen was reduced by 20% and 21% and C/N ratio increased by 25% and 28% in sites burned at 2.5 and 5 FPD, respectively. Litter lignin/N ratio was reduced 28% at 2.5 FPD, compared to litter from unburned sites. We found no changes in soil pH, total N, NO 3-N, NH 3-N, plant-available Ps or K due to prescribed burning. Microbial biomass of Gram negative bacteria, as determined by phospholipid fatty acid (PLFA) analyses, decreased from 25% of biomarker abundance at the unburned sites to 20% at the 5 FPD sites. No other microbial functional group was significantly influenced by fire frequency. Our results indicate prescribed burning with low intensity fires in upland oak forests do not have major effects on the soils if these fires occur infrequently, i.e. less frequent than 2.5 FPD. However, frequent burning of these upland oak forests (5 FPD) resulted in important changes in the litter and soil that may adversely affect litter decomposition rates, soil carbon storage, soil water holding capacity, and soil erosion rates. Our findings indicate prescribed burning can be an important management tool, however, at high fire frequencies there may be tradeoffs between vegetation management goals and long-term adverse affects on the soil.
We assessed whether (1) arbuscular mycorrhizal colonization of roots (RC) and/or plant responses ... more We assessed whether (1) arbuscular mycorrhizal colonization of roots (RC) and/or plant responses to arbuscular mycorrhizae (MR) vary with plant phylogeny and (2) MR and RC can be more accurately predicted with a phylogenetic predictor relative to a null model and models with plant trait and taxonomic predictors. In a previous study, MR and RC of 95 grassland species were measured. We constructed a phylogeny for these species and found it explained variation in MR and RC. Next, we used multiple regressions to identify the models that most accurately predicted plant MR. Models including either phylogenetic or phenotypic and taxonomic information similarly improved our ability to predict MR relative to a null model. Our study illustrates the complex evolutionary associations among species and constraints of using phylogenetic information, relative to plant traits, to predict how a plant species will interact with AMF.
Understanding the relative importance of environmental and anthropogenic factors in driving plant... more Understanding the relative importance of environmental and anthropogenic factors in driving plant community structure, including relative dominance of native and non‐native species, helps predict community responses to biological invasions. To assess factors influencing plant communities on San Clemente Island, USA, we conducted an islandwide vegetation survey in which we measured plant species richness and percent cover of native and non‐native plants, as well as physical environmental variables, soil chemical properties, abundance of soil microbial functional groups (e.g., arbuscular mycorrhizal fungi [AMF]), and a human disturbance variable (distance to road). We found that total plant species richness decreased with increasing non‐native plant cover, soil pH, and AMF abundance. Native plant cover increased with increasing distance to a major paved road and decreased with increasing soil moisture and pH. Non‐native plant cover decreased with increasing distance to a major paved r...
AimInvasions of non‐native earthworms into previously earthworm‐free regions are a major conserva... more AimInvasions of non‐native earthworms into previously earthworm‐free regions are a major conservation concern because they alter ecosystems and threaten biological diversity. Little information is available, however, about effects of earthworm invasions outside of temperate and boreal forests, particularly about invasions of islands. For San Clemente Island (SCI), California (USA) – an oceanic island with numerous endemic and endangered plant and vertebrate species – we assessed the spatial extent and drivers of earthworm invasion and examined relationships between earthworms and plant and soil microbial communities.LocationSan Clemente Island, southern California, USA.MethodsUsing a stratified random sampling approach, we sampled earthworms, vegetation, soils and microbial communities across SCI. We examined the relationship between the presence of invasive earthworms and soil and landscape variables using logistic regression models and implemented a spatial representation of the b...
A mounting body of research suggests that invasive non-native earthworms substantially alter micr... more A mounting body of research suggests that invasive non-native earthworms substantially alter microbial communities, including arbuscular mycorrhizal fungi (AMF). These changes to AMF can cascade to affect plant communities and vertebrate populations. Despite these research advances, relatively little is known about: (1) the mechanisms behind earthworms' effects on AMF, and (2) the factors that determine the outcomes of earthworm-AMF interactions (i.e., whether AMF abundance is increased or decreased, and subsequent effects on plants). We predict that AMF-mediated effects of non-native earthworms on ecosystems are nearly universal because: (1) AMF are important components of most terrestrial ecosystems, (2) non-native earthworms have become established in nearly every type of terrestrial ecosystem, and (3) nonnative earthworms, due to their burrowing and feeding behavior, greatly affect AMF with potentially profound concomitant effects on plant communities. We highlight the multiple direct and indirect effects of non-native earthworms on plants and review what is currently known about the interaction between earthworms and AMF. We also illustrate how the effects of nonnative earthworms on plant-AMF mutualisms can alter the structure and stability of aboveground plant communities, as well as the vertebrate communities relying on these habitats. Integrative studies that assess the interactive effects of earthworms and AMF can provide new insights into the role that belowground ecosystem engineers play in altering aboveground ecological processes. Understanding these processes may improve our ability to predict the structure of plant and animal communities in earthworm-invaded regions and to develop management strategies that limit the numerous undesired impacts of earthworms.
Flours from live spelt cultivars grown over three years were evaluated as to their hreadbaking qu... more Flours from live spelt cultivars grown over three years were evaluated as to their hreadbaking quality and isolated starch properties. The starch properties included amylose contents, gelatinization temperatures (differential scanning calorimetry), granule size distributions, and pasting properties. Milled flour showed highly variable protein content and was higher than hard winter wheat, with short dottgh-mix times indicating weak gluten. High protein cultivars gave good crumb scores, some of which surpassed the I-IRW baking control. Loaf volume was correlated to protein and all spelt cultivars were at least 9-51% lower than the I-tRW control. Isolated starch properties revealed an increase in amylose in the spelt starches of 2-21% over the hard red winter wheat (l-IRW) control. Negative correlations were observed for the large A-type granules to bread crumb score. amylose level, and final pasting viscosity for cultivars grown in year 1999 and to pasting temperature in 1998 samples. Positive correlations were found for the small Band C-type granules relative to crumb score, loaf volume. aniylose, and RVA final pasting viscosity for cultivars grown in 1999, and to RVA pasting temperature for samples grown in 1998. The environmental impact on spelt properties seemed to have a greater effect than genetic control. U.S. production of spells peaked in the early 1900's and declined steadily thereafter. The first recorded U.S. production of spell occurred in North and South Dakota, Kansas, Nebraska. and Minnesota. Limited production also occurred in Wisconsin.
Arbuscular mycorrhizal (AM) fungi and rhizobium are likely important drivers of plant coexistence... more Arbuscular mycorrhizal (AM) fungi and rhizobium are likely important drivers of plant coexistence and grassland productivity due to complementary roles in supplying limiting nutrients. However, the interactive effects of mycorrhizal and rhizobial associations on plant community productivity and competitive dynamics remain unclear. To address this, we conducted a greenhouse experiment to determine the influences of these key microbial functional groups on communities comprising three plant species by comparing plant communities grown with or without each symbiont. We also utilized N-fertilization and clipping treatments to explore potential shifts in mycorrhizal and rhizobial benefits across abiotic and biotic conditions. Our research suggests AM fungi and rhizobium co-inoculation was strongly facilitative for plant community productivity and legume ( Medicago sativa ) growth and nodulation. Plant competitiveness shifted in the presence of AM fungi and rhizobium, favoring M. sativa over a neighboring C 4 grass ( Andropogon gerardii ) and C 3 forb ( Ratibida pinnata ). This may be due to rhizobial symbiosis as well as the relatively greater mycorrhizal growth response of M. sativa , compared to the other model plants. Clipping and N-fertilization altered relative costs and benefits of both symbioses, presumably by altering host-plant nitrogen and carbon dynamics, leading to a relative decrease in mycorrhizal responsiveness and proportional biomass of M. sativa relative to the total biomass of the entire plant community, with a concomitant relative increase in A. gerardii and R. pinnata proportional biomass. Our results demonstrate a strong influence of both microbial symbioses on host-plant competitiveness and community dynamics across clipping and N-fertilization treatments, suggesting the symbiotic rhizosphere community is critical for legume establishment in grasslands.
Perennial grasses have been proposed as a source for bioenergy. However, the impact of biomass re... more Perennial grasses have been proposed as a source for bioenergy. However, the impact of biomass removal on long-term soil quality needs to be assessed. Soil C and N storage and soil aggregate stability may be used as indicators of soil quality. Long-term experimental tallgrass prairie plots, located at Konza Prairie Biological Station in the flinthills of Eastern Kansas were used
We assessed whether (1) arbuscular mycorrhizal colonization of roots (RC) and/or plant responses ... more We assessed whether (1) arbuscular mycorrhizal colonization of roots (RC) and/or plant responses to arbuscular mycorrhizae (MR) vary with plant phylogeny and (2) MR and RC can be more accurately predicted with a phylogenetic predictor relative to a null model and models with plant trait and taxonomic predictors. In a previous study, MR and RC of 95 grassland species were measured. We constructed a phylogeny for these species and found it explained variation in MR and RC. Next, we used multiple regressions to identify the models that most accurately predicted plant MR. Models including either phylogenetic or phenotypic and taxonomic information similarly improved our ability to predict MR relative to a null model. Our study illustrates the complex evolutionary associations among species and constraints of using phylogenetic information, relative to plant traits, to predict how a plant species will interact with AMF.
Upland oak forests in the ecotone between the eastern deciduous forest and the southern Great Pla... more Upland oak forests in the ecotone between the eastern deciduous forest and the southern Great Plains are threatened by encroachment of eastern redcedar (Juniperus virginiana) due to fire suppression. The rapid rate of encroachment caused concern about concomitant alterations of site characteristics including nutrient cycling and the soil microbial communities (SMC) that could lead to positive feedbacks reinforcing eastern redcedar encroachment. We studied eight upland oak forests across central and western Oklahoma with stands representing three levels of encroachment: oak-dominated, eastern redcedar-dominated, and an intermediate mixture of both species. We analyzed litter chemistry (carbon, lignin, and nitrogen), soil chemistry (soil organic matter, NH 4 N, NO 3-N, PO 4 , K, and pH), and profiled soil microbial communities using phospholipid fatty acid analysis (PLFA). Eastern redcedar encroachment was accompanied by reduced litter carbon along with higher levels of arbuscular mycorrhizal (AM) fungi while litter N was lower in mixed stands. However, we detected no change in soil chemistry. Our results indicate eastern redcedar encroachment in these upland oak forests reduced litter quality and altered the SMC through increases in AM fungi, a symbiont associated with eastern redcedar. These alterations may create positive soil-microbial feedbacks by reducing the fitness of the dominant oak species and facilitating rapid increase in eastern redcedar in this threatened, oak-dominated ecosystem.
Arbuscular mycorrhizal (AM) fungi can support the establishment of mycotrophic plants in new envi... more Arbuscular mycorrhizal (AM) fungi can support the establishment of mycotrophic plants in new environments. However, the role of mycorrhizal symbiosis in interactions between perennial and weedy annual plants is not well understood. In our current study, we examine how widespread generalist AM fungi and soil disturbance, including disturbance of AM fungal networks (CMNs), affect the performance of two late-successional perennial plants of Central Europe, Senecio jacobaea and Crepis biennis, co-occurring with weedy annual forbs, Conyza canadensis and Erigeron annuus. Although presence of weedy annual E. annuus or C. canadensis did not affect the performance of the paired perennials, AM fungi supported perennial C. biennis in competition with weedy annual E. annuus. However, this AM-aided underpinning was independent of disturbance of CMNs. Conversely, although AM fungi benefited perennial S. jacobaea, this did not affect its competitive abilities when grown with weedy annual C. canadensis. Similarly, soil disturbance, independent of AM fungal presence, improved plant tissue P and biomass production of S. jacobaea, but not its competitive abilities. Our results show AM fungi may be advantageous for perennial plants growing in competition with weedy annual plants. Therefore, maintaining healthy soils containing an abundance of AM fungi, may encourage late successional perennial plants, potentially limiting establishment of weedy annual plant species. The majority (> 60%) of land plants 1,2 , including most annual plant species 3-5 , form mycorrhizal interactions with arbuscular mycorrhizal (AM) fungi (Glomeromycotina; 6). AM fungi supply host plants with nutrients (especially phosphorus (P) 7) from the soil, aid in protecting against plant pathogens 8,9 , and potentially an array of other services in exchange for carbon from the host plant 10,11. For example, the AM fungus Gigaspora margarita, increased P uptake of maize by 55% 12. Further, under P-limiting soil conditions, AM fungi can be responsible for nearly all P uptake by the mycorrhizal host plant 13,14. These strong benefits often result in AM fungi affecting coexistence of plant species, and therefore the composition of plant communities 15-17. Therefore, these symbiotic fungi may enhance or prevent establishment of weedy annuals, or increase the competitive abilities, and thereby persistence, of perennial species. Both annual and perennial plant species generally form an association with AM fungi for competitive success 1-5. Likewise, AM fungal symbionts may be essential for naturalization and spreading of weedy annual plants, yet this has rarely been studied (although see 18-20). Weedy plant species are generally annuals representing the R strategy, and are typically facultative mycorrhizal 21,22. Facultative mycorrhizal plants form weak associations with AM fungi, can complete their life cycle in the absence of the symbiosis, and are generally characterized by low levels of AM fungal root colonization 21,22,24. The annual life history strategy and facultative AM association can be potentially beneficial in disturbed habitats where intact AM fungal communities and competition for resources are low. Perennials, in contrast, develop long-term life history strategies for competition for limited resources, as they survive for extended periods of time. Short-term strategies of annuals may be disadvantageous in established plant communities where hyphal networks connect individual perennial plants and transfer nutrients, mainly N and P, between plants (i.e., common mycorrhizal networks: CMNs 23). Commandeering these networks can increase competitiveness of some plants, allowing disproportionately greater benefits compared to symbiotic carbon costs.
Arbuscular mycorrhizal fungi (AMF) provide crucial support for the establishment of plants in nov... more Arbuscular mycorrhizal fungi (AMF) provide crucial support for the establishment of plants in novel environments. We hypothesized that the OTU/genus richness and diversity of soil‐ and root‐associated AMF associated with alien plant species in their exotic ranges are lower than those in their native ranges. We examined the root‐associated and soil‐dwelling AMF of 11 invasive plant species in their native and exotic ranges in the United States and Europe by DNA sequencing of the ITS2 locus. Examined root‐associated AMF assemblages were simplified, which manifested as the loss of several AMF genera in the exotic ranges of the plants. These fungal assemblages were also characterized by greater dominance and simplification of the fungal assemblages. The dominant fungal genera were present regardless of whether their host plants were in their native or exotic ranges. Interestingly, both the native and invaded soils hosted diverse local AMF assemblages. Therefore, alien plant invasions were not limited to soils with low AMF diversity. Some AMF taxa could be context‐dependent passengers rather than drivers of alien plant invasions. Further studies should identify functions of AMF missing or less abundant in roots of plants growing in exotic ranges.
to vegetative biomass. Cool-season C3 grasses, Koeleria pyramidata and Poa pratensis, accumulated... more to vegetative biomass. Cool-season C3 grasses, Koeleria pyramidata and Poa pratensis, accumulated more biomass and were a significantly greater proportion of total community biomass in mycorrhizal-suppressed microcosms. Forbs showed variable responses to mycorrhizal suppression. The two legumes Amorpha canescens and Dalea purpurea had significantly lower survivorship in the fungicide-treated microcosms, relative to the controls. The results confirm the high mycorrhizal dependency and growth responsiveness of dominant prairie grasses, and indicate that differential growth and demographic responses to mycorrhizal colonization among species may significantly affect plant productivity and species relative abundances in tallgrass prairie.
BackgroundGrasslands are globally imperiled, facing continued threats from anthropogenic disturba... more BackgroundGrasslands are globally imperiled, facing continued threats from anthropogenic disturbances. Seeding remains a common grassland restoration method, and yet, is typically met with limited success, partially because soils of degraded systems inhibit the germination of native species.MethodsWe assessed the germination success of 16 native grassland species sown in soils collected from a degraded grassland converted into a nonnative warm‐season perennial grass, Bothriochloa ischaemum, and areas previously subjected to the eradication of this nonnative species. Our objectives were as follows: (1) determine native seed germination in soils collected from B. ischaemum or eradication control sites, compared to germination in native grassland soil, and (2) assess if native soil inoculation improves germination, compared to germination in degraded soils without inoculation.ResultsGermination of native species was exceedingly low when seeded into soil dominated by B. ischaemum, or in...
Elevated temperatures and drought may exacerbate invasion success of non-native grasses, as non-n... more Elevated temperatures and drought may exacerbate invasion success of non-native grasses, as non-native species often possess traits favored by a warmer, drier world. In our study, we assessed plant traits potentially linked to invasion success under elevated temperature and drought, including biomass production, reproductive allocation, arbuscular mycorrhizal (AM) fungal root colonization, and germination of native grasses and non-native invasive grasses. We selected two caespitose warm-season grasses [native (Schizachyrium scoparium) and non-native (Bothriochloa ischaemum)] and two cool-season grasses [native (Pascopyrum smithii) and non-native (Bromus inermis)]. Plant biomass, reproductive effort, and AM fungal colonization were assessed at two temperatures (ambient or elevated) and four levels of soil water-availability; germination was assessed at two temperatures and three levels of soil water-availability. Non-native warm- and cool-season grasses produced greater vegetative biomass, initiated seed production more frequently, and displayed greater germination when grown under elevated temperature and drought, compared to their paired native counterparts. Percent AM fungal root colonization of the non-native grasses was generally greater than native grasses regardless of soil moisture or elevated temperature. Our results suggest that under warmer and drier conditions non-native grasses will continue to outperform native species, due to greater biomass production, germination capabilities, and colonization by AM fungi.
In a globalized world, plant invasions are common challenges for native ecosystems. Although a co... more In a globalized world, plant invasions are common challenges for native ecosystems. Although a considerable number of invasive plants form arbuscular mycorrhizae, interactions between arbuscular mycorrhizal (AM) fungi and invasive and native plants are not well understood. In this study, we conducted a greenhouse experiment examining how AM fungi affect interactions of co-occurring plant species in the family Asteracea, invasive Echinops sphaerocephalus and native forb of central Europe Inula conyzae. The effects of initial soil disturbance, including the effect of intact or disturbed arbuscular mycorrhizal networks (CMNs), were examined. AM fungi supported the success of invasive E. sphaerocephalus in competition with native I. conyzae, regardless of the initial disturbance of CMNs. The presence of invasive E. sphaerocephalus decreased mycorrhizal colonization in I. conyzae, with a concomitant loss in mycorrhizal benefits. Our results confirm AM fungi represent one important mechan...
The plant microbiome is critical to plant health and is degraded with anthropogenic disturbance. ... more The plant microbiome is critical to plant health and is degraded with anthropogenic disturbance. However, the value of re‐establishing the native microbiome is rarely considered in ecological restoration. Arbuscular mycorrhizal (AM) fungi are particularly important microbiome components, as they associate with most plants, and later successional grassland plants are strongly responsive to native AM fungi. With five separate sites across the United States, we inoculated mid‐ and late successional plant seedlings with one of three types of native microbiome amendments: (a) whole rhizosphere soil collected from local old‐growth, undisturbed grassland communities in Illinois, Kansas or Oklahoma, (b) laboratory cultured AM fungi from these same old‐growth grassland sites or (c) no microbiome amendment. We also seeded each restoration with a diverse native seed mixture. Plant establishment and growth was followed for three growing seasons. The reintroduction of soil microbiome from native...
summaryIn order to determine whether variation in root system architecture can be said to be adap... more summaryIn order to determine whether variation in root system architecture can be said to be adaptive, it is necessary' to be able to define the costs and benefits of particular architectures. A simulation model of root growth is described that allows the development of root systems varying in several important architectural features, including topology, link lengths and radii, and branching angles. The program also estimates the exploitation efficiency of each root system, as the ratio of the volume of soil occupied by depletion zones (allowing for overlaps between competing roots) and the volume of tissue required to construct the system. Output from the model shows that high exploitation efficiency is associated with a herringbone topology (where branching is predominantly on the main axis) and with long interior and exterior links, although all these characteristics are associated with large tissue volumes and hence high construction cost, We predict, therefore, that such ‘e...
Prescribed burning is commonly used in forests to reduce fuel load, prevent encroachment of exoti... more Prescribed burning is commonly used in forests to reduce fuel load, prevent encroachment of exotic species, maintain biological diversity and improve wildlife habitat. The low intensity burns that are conducted at intervals of 1-10 years may have long-term effects on the abiotic and biotic components of the soil. We assessed how prescribed burning altered litter, soil physical and chemical properties, and soil microbial communities in upland oak forests subjected to prescribed burning at frequencies of 0 (unburned), 2.5 and 5 fires per decade (FPD) over a 20 year period. Prescribed burning at 5 FPD reduced soil organic matter by 60% and soil organic carbon by 64% and increased bulk density by 20%. Compared to unburned controls, litter nitrogen was reduced by 20% and 21% and C/N ratio increased by 25% and 28% in sites burned at 2.5 and 5 FPD, respectively. Litter lignin/N ratio was reduced 28% at 2.5 FPD, compared to litter from unburned sites. We found no changes in soil pH, total N, NO 3-N, NH 3-N, plant-available Ps or K due to prescribed burning. Microbial biomass of Gram negative bacteria, as determined by phospholipid fatty acid (PLFA) analyses, decreased from 25% of biomarker abundance at the unburned sites to 20% at the 5 FPD sites. No other microbial functional group was significantly influenced by fire frequency. Our results indicate prescribed burning with low intensity fires in upland oak forests do not have major effects on the soils if these fires occur infrequently, i.e. less frequent than 2.5 FPD. However, frequent burning of these upland oak forests (5 FPD) resulted in important changes in the litter and soil that may adversely affect litter decomposition rates, soil carbon storage, soil water holding capacity, and soil erosion rates. Our findings indicate prescribed burning can be an important management tool, however, at high fire frequencies there may be tradeoffs between vegetation management goals and long-term adverse affects on the soil.
We assessed whether (1) arbuscular mycorrhizal colonization of roots (RC) and/or plant responses ... more We assessed whether (1) arbuscular mycorrhizal colonization of roots (RC) and/or plant responses to arbuscular mycorrhizae (MR) vary with plant phylogeny and (2) MR and RC can be more accurately predicted with a phylogenetic predictor relative to a null model and models with plant trait and taxonomic predictors. In a previous study, MR and RC of 95 grassland species were measured. We constructed a phylogeny for these species and found it explained variation in MR and RC. Next, we used multiple regressions to identify the models that most accurately predicted plant MR. Models including either phylogenetic or phenotypic and taxonomic information similarly improved our ability to predict MR relative to a null model. Our study illustrates the complex evolutionary associations among species and constraints of using phylogenetic information, relative to plant traits, to predict how a plant species will interact with AMF.
Understanding the relative importance of environmental and anthropogenic factors in driving plant... more Understanding the relative importance of environmental and anthropogenic factors in driving plant community structure, including relative dominance of native and non‐native species, helps predict community responses to biological invasions. To assess factors influencing plant communities on San Clemente Island, USA, we conducted an islandwide vegetation survey in which we measured plant species richness and percent cover of native and non‐native plants, as well as physical environmental variables, soil chemical properties, abundance of soil microbial functional groups (e.g., arbuscular mycorrhizal fungi [AMF]), and a human disturbance variable (distance to road). We found that total plant species richness decreased with increasing non‐native plant cover, soil pH, and AMF abundance. Native plant cover increased with increasing distance to a major paved road and decreased with increasing soil moisture and pH. Non‐native plant cover decreased with increasing distance to a major paved r...
AimInvasions of non‐native earthworms into previously earthworm‐free regions are a major conserva... more AimInvasions of non‐native earthworms into previously earthworm‐free regions are a major conservation concern because they alter ecosystems and threaten biological diversity. Little information is available, however, about effects of earthworm invasions outside of temperate and boreal forests, particularly about invasions of islands. For San Clemente Island (SCI), California (USA) – an oceanic island with numerous endemic and endangered plant and vertebrate species – we assessed the spatial extent and drivers of earthworm invasion and examined relationships between earthworms and plant and soil microbial communities.LocationSan Clemente Island, southern California, USA.MethodsUsing a stratified random sampling approach, we sampled earthworms, vegetation, soils and microbial communities across SCI. We examined the relationship between the presence of invasive earthworms and soil and landscape variables using logistic regression models and implemented a spatial representation of the b...
A mounting body of research suggests that invasive non-native earthworms substantially alter micr... more A mounting body of research suggests that invasive non-native earthworms substantially alter microbial communities, including arbuscular mycorrhizal fungi (AMF). These changes to AMF can cascade to affect plant communities and vertebrate populations. Despite these research advances, relatively little is known about: (1) the mechanisms behind earthworms' effects on AMF, and (2) the factors that determine the outcomes of earthworm-AMF interactions (i.e., whether AMF abundance is increased or decreased, and subsequent effects on plants). We predict that AMF-mediated effects of non-native earthworms on ecosystems are nearly universal because: (1) AMF are important components of most terrestrial ecosystems, (2) non-native earthworms have become established in nearly every type of terrestrial ecosystem, and (3) nonnative earthworms, due to their burrowing and feeding behavior, greatly affect AMF with potentially profound concomitant effects on plant communities. We highlight the multiple direct and indirect effects of non-native earthworms on plants and review what is currently known about the interaction between earthworms and AMF. We also illustrate how the effects of nonnative earthworms on plant-AMF mutualisms can alter the structure and stability of aboveground plant communities, as well as the vertebrate communities relying on these habitats. Integrative studies that assess the interactive effects of earthworms and AMF can provide new insights into the role that belowground ecosystem engineers play in altering aboveground ecological processes. Understanding these processes may improve our ability to predict the structure of plant and animal communities in earthworm-invaded regions and to develop management strategies that limit the numerous undesired impacts of earthworms.
Flours from live spelt cultivars grown over three years were evaluated as to their hreadbaking qu... more Flours from live spelt cultivars grown over three years were evaluated as to their hreadbaking quality and isolated starch properties. The starch properties included amylose contents, gelatinization temperatures (differential scanning calorimetry), granule size distributions, and pasting properties. Milled flour showed highly variable protein content and was higher than hard winter wheat, with short dottgh-mix times indicating weak gluten. High protein cultivars gave good crumb scores, some of which surpassed the I-IRW baking control. Loaf volume was correlated to protein and all spelt cultivars were at least 9-51% lower than the I-tRW control. Isolated starch properties revealed an increase in amylose in the spelt starches of 2-21% over the hard red winter wheat (l-IRW) control. Negative correlations were observed for the large A-type granules to bread crumb score. amylose level, and final pasting viscosity for cultivars grown in year 1999 and to pasting temperature in 1998 samples. Positive correlations were found for the small Band C-type granules relative to crumb score, loaf volume. aniylose, and RVA final pasting viscosity for cultivars grown in 1999, and to RVA pasting temperature for samples grown in 1998. The environmental impact on spelt properties seemed to have a greater effect than genetic control. U.S. production of spells peaked in the early 1900's and declined steadily thereafter. The first recorded U.S. production of spell occurred in North and South Dakota, Kansas, Nebraska. and Minnesota. Limited production also occurred in Wisconsin.
Arbuscular mycorrhizal (AM) fungi and rhizobium are likely important drivers of plant coexistence... more Arbuscular mycorrhizal (AM) fungi and rhizobium are likely important drivers of plant coexistence and grassland productivity due to complementary roles in supplying limiting nutrients. However, the interactive effects of mycorrhizal and rhizobial associations on plant community productivity and competitive dynamics remain unclear. To address this, we conducted a greenhouse experiment to determine the influences of these key microbial functional groups on communities comprising three plant species by comparing plant communities grown with or without each symbiont. We also utilized N-fertilization and clipping treatments to explore potential shifts in mycorrhizal and rhizobial benefits across abiotic and biotic conditions. Our research suggests AM fungi and rhizobium co-inoculation was strongly facilitative for plant community productivity and legume ( Medicago sativa ) growth and nodulation. Plant competitiveness shifted in the presence of AM fungi and rhizobium, favoring M. sativa over a neighboring C 4 grass ( Andropogon gerardii ) and C 3 forb ( Ratibida pinnata ). This may be due to rhizobial symbiosis as well as the relatively greater mycorrhizal growth response of M. sativa , compared to the other model plants. Clipping and N-fertilization altered relative costs and benefits of both symbioses, presumably by altering host-plant nitrogen and carbon dynamics, leading to a relative decrease in mycorrhizal responsiveness and proportional biomass of M. sativa relative to the total biomass of the entire plant community, with a concomitant relative increase in A. gerardii and R. pinnata proportional biomass. Our results demonstrate a strong influence of both microbial symbioses on host-plant competitiveness and community dynamics across clipping and N-fertilization treatments, suggesting the symbiotic rhizosphere community is critical for legume establishment in grasslands.
Perennial grasses have been proposed as a source for bioenergy. However, the impact of biomass re... more Perennial grasses have been proposed as a source for bioenergy. However, the impact of biomass removal on long-term soil quality needs to be assessed. Soil C and N storage and soil aggregate stability may be used as indicators of soil quality. Long-term experimental tallgrass prairie plots, located at Konza Prairie Biological Station in the flinthills of Eastern Kansas were used
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