Arbuscular mycorrhizal fungal communities change among three stages of primary sand dune succession but do not alter plant growth

Plant interactions with soil biota could have a significant impact on plant successional trajectory by benefiting plants in a particular successional stage over others. The influence of soil mutualists such as mycorrhizal fungi is thought to be an important feedback component, yet they have shown benefits to both early and late successional plants that could either retard or accelerate succession. Here we first determine if arbuscular mycorrhizal (AM) fungi differ among three stages of primary sand dune succession and then if they alter growth of plants from particular successional stages. We isolated AM fungal inoculum from early, intermediate or late stages of a primary dune succession and compared them using cloning and sequencing. We then grew eight plant species that dominate within each of these successional stages with each AM fungal inoculum. We measured fungal growth to assess potential AM functional differences and plant growth to determine if AM fungi positively or negatively affect plants. AM fungi isolated from early succession were more phylogenetically diverse relative to intermediate and late succession while late successional fungi consistently produced more soil hyphae and arbuscules. Despite these differences, inocula from different successional stages had similar effects on the growth of all plant species. Host plant biomass was not affected by mycorrhizal inoculation relative to un-inoculated controls. Although mycorrhizal communities differ among primary dune successional stages and formed different fungal structures, these differences did not directly affect the growth of plants from different dune successional stages in our experiment and therefore may be less likely to directly contribute to plant succession in sand dunes

Determining a minimum detection threshold in terminal restriction fragment length polymorphism analysis

Terminal restriction fragment length polymorphism (T-RFLP) analysis is a common technique used to characterize soil microbial diversity. The fidelity of this technique in accurately reporting diversity has not been thoroughly evaluated. Here we determine if rare fungal species can be reliably detected by T-RFLP analysis. Spores from three arbuscular mycorrhizal fungal species were each mixed at a range of concentrations (1%, 10%, 50%, and 100%) with Glomus irregulare to establish a minimum detection threshold. T-RFLP analysis was capable of detecting diagnostic peaks of rare taxa at concentrations as low as 1%. The relative proportion of the target taxa in the sample and DNA concentration influenced peak detection reliability. However, low concentrations produced small, inconsistent electropherogram peaks contributing to difficulty in differentiating true peaks from signal noise. The results of this experiment suggest T-RFLP is a reproducible and high fidelity procedure, which requires careful data interpretation in order to accurately characterize sample diversity

Weak tradeoff between xylem safety and xylem-specific hydraulic efficiency across the world\u27s woody plant species.

The evolution of lignified xylem allowed for the efficient transport of water under tension, but also exposed the vascular network to the risk of gas emboli and the spread of gas between xylem conduits, thus impeding sap transport to the leaves. A well-known hypothesis proposes that the safety of xylem (its ability to resist embolism formation and spread) should trade off against xylem efficiency (its capacity to transport water). We tested this safety-efficiency hypothesis in branch xylem across 335 angiosperm and 89 gymnosperm species. Safety was considered at three levels: the xylem water potentials where 12%, 50% and 88% of maximal conductivity are lost. Although correlations between safety and efficiency were weak (r(2) \u3c 0.086), no species had high efficiency and high safety, supporting the idea for a safety-efficiency tradeoff. However, many species had low efficiency and low safety. Species with low efficiency and low safety were weakly associated (r(2) \u3c 0.02 in most cases) with higher wood density, lower leaf- to sapwood-area and shorter stature. There appears to be no persuasive explanation for the considerable number of species with both low efficiency and low safety. These species represent a real challenge for understanding the evolution of xylem

Water Relations of Ponderosa Pine in Contrasting Environments: Implications for Global Climate Change

146 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1999.The rise in atmospheric CO2 is expected to force a rise in temperature and atmospheric vapor pressure deficit (VPD) by the end of the 21st century. For trees, the most relevant allometric component controlling water transport is the ratio of biomass allocated to leaves versus sapwood (AL/AS). Within Pinus, trees decrease ALAS in response to rising VPD. Thus, rises in air temperature and VPD may profoundly alter the water relations of trees and forests. I used stands of ponderosa pine growing along a climate gradient (desert v. montane) in the western United States as a model system to determine the effects these climate-related shifts in biomass allocation on the water relations of mature trees. I found that desert trees, because of larger diameter tracheids in the sapwood, had 37% higher rates of water transport per unit sapwood area than montane trees. The combination of low ALAS and higher sapwood conducting efficiency led to two-fold higher hydraulic conductivity (KL), and thus higher transpiration in desert trees. Desert and montane trees had similar vulnerability to xylem embolism and soil-to-leaf water potential gradients during the growing season. Despite higher allocation to sapwood, desert and montane trees did not differ in their reliance on stored water reserves. Paradoxically, any gain in sapwood water storage capacity through high allocation to sapwood in desert trees was offset by a loss in foliage storage capacity. The primary advantage of high allocation to sapwood in a warm and dry environment is to increase KL in order to prevent xylem embolism induction. A growth chamber study revealed that there were no interactions between elevated CO2 and temperature on water transport. Similar to their adult counterparts in the field, ponderosa pine seedlings reduced AL/AS and had higher KL in response to elevated temperatures and VPD. These results suggest that rising temperatures and VPD may exert stronger influence on tree water relations than elevated CO2 in a future climate. A common garden study showed that although desert and montane populations differed genetically, none of this variation was associated with ecotypic divergence. Thus, differences in the water relations of desert and montane trees may be related to phenotypic plasticity.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Data from: Mycorrhizal feedback is not associated with the outcome of competition in old-field perennial plants

The symbiosis between plants and arbuscular mycorrhizal (AM) fungi is hypothesized to be an important contributor to plant–soil feedbacks, which can influence the outcome of inter-specific competition. Mycorrhizal feedbacks can be conspecific, which affects individuals of the same species, or heterospecific, which affects individuals of a different species. When heterospecific feedbacks are more positive than conspecific feedbacks, heterospecific individuals are expected to outcompete conspecific individuals. To test this hypothesis, we quantified conspecific mycorrhizal feedback for Plantago lanceolata as a focal species, and heterospecific mycorrhizal feedbacks for 21 competitor old-field species using mycorrhizae cultured with P. lanceolata. We quantified inter-specific competition against the focal species by growing the 21 old-field species with and without P. lanceolata in the presence of mycorrhizae cultured with P. lanceolata. Heterospecific and conspecific feedbacks were both positive, and average heterospecific feedbacks exceeded conspecific feedback by 75%. Competition suppressed P. lanceolata biomass by 14% and average competitor biomass was reduced by 44% in the presence of P. lanceolata, and these effects varied with competitor species identity. Contrary to predictions, the magnitude of heterospecific feedbacks did not predict the ability of competitor species to either suppress or resist suppression by P. lanceolata. Instead, the outcome of competition was significantly and positively correlated with intrinsic growth rate, measured as biomass of competitor species five weeks after germination in non-inoculated conditions. Our findings suggest that species experiencing more positive mycorrhizal feedbacks than a competitor do not necessarily have a competitive advantage. Mycorrhizal mediated soil feedbacks may be less important than intrinsic differences in growth rate in determining competitive outcomes

Locations of individual plants collected in July 2016 at Long-Term Mycorrhiza Research Site

The locations of individual plants were recorded on the coordinate plane of the grid (45 m X 50 m ) where permanent plots were placed for plant community survey at the Long-Term Mycorrhiza Research Site in the University of Guelph Nature Reserve, Guelph, Canada . The origin (0, 0) is located on a north corner of the grid, and X and Y axes are oriented toward southwest and southeast from the origin, respectively

Data from: Plant geographic origin and phylogeny as potential drivers of community structure in root-inhabiting fungi

1. Root-inhabiting fungal communities, including mutualists and antagonists, influence host plant performance, and can potentially shape plant community composition. However, there is uncertainty about how root-inhabiting fungal communities are structured, and if fungal community characteristics are significant predictors of host plant abundance. 2. In this study, we first assessed how root-inhabiting fungal communities were structured in relation to the phylogeny and geographic origins (native vs exotic) of their host plants in an old-field community. In addition, we took into consideration the spatial arrangements (i.e. physical locations) of the individual host plants. We then tested if the relative abundances of pathogenic and beneficial arbuscular mycorrhizal (AM) fungi could predict host plant abundances. 3. We found that host plant phylogeny was an important factor in structuring the whole fungal community, irrespective of host plant origin. Furthermore, the spatial arrangements of individual host plants were a strong predictor of AM fungal community structure. Host plant phylogeny and spatial arrangements appeared to similarly affect the structure of pathogenic fungal communities. No distinct differences were observed between native and exotic plant species in fungal community characteristics. The relative abundances of AM and pathogenic fungi were not significant predictors for observed abundances of their host plants. 4. Synthesis. Host plant phylogeny and spatial arrangements can structure naturally occurring root-inhabiting fungal communities. The absence of distinct differences in fungal community composition, including pathogens, in exotic and native plants suggests long residence times and the consequent naturalization of exotic species in the region, allowing for the establishment of similar plant-microbial interactions between native and exotic species

Plant species relative abundances at Long-Term Mycorrhiza Research Site in Jun 2016

Relative abundances of vascular plants were quantified between June 13 and June 20, 2016, at Long-Term Mycorrhiza Research Site in the University of Guelph Nature Reserve, Guelph, Canada. The method is described in the article