01949nas a2200181 4500008004100000245005400041210005400095300001500149490000800164520142600172653001801598100001801616700001701634700001701651700001701668700001501685856006701700 2015 eng d00aMycorrhizal phenotypes and the law of the minimum0 aMycorrhizal phenotypes and the law of the minimum a1473 -14840 v2053 a

Mycorrhizal phenotypes arise from interactions among plant and fungal genotypes and the environment. Differences in the stoichiometry and uptake capacity of fungi and plants make arbuscular mycorrhizal (AM) fungi inherently more nitrogen (N) limited and less phosphorus (P) limited than their host plants. Mutualistic phenotypes are most likely in P-limited systems and commensal or parasitic phenotypes in N-limited systems. Carbon (C) limitation is expected to cause phenotypes to shift from mutualism to commensalism and even parasitism. Two experiments compared the influence of fertilizer and shade on mycorrhizas in Andropogon gerardii across three naturally N-limited or P-limited grasslands. A third experiment examined the interactive effects of N and P enrichment and shade on A. gerardii mycorrhizas. Our experiments generated the full spectrum of mycorrhizal phenotypes. These findings support the hypothesis that mutualism is likely in P-limited systems and commensalism or parasitism is likely in N-limited systems. Furthermore, shade decreased C-assimilation and generated less mutualistic mycorrhizal phenotypes with reduced plant and fungal biomass. Soil fertility is a key controller of mycorrhizal costs and benefits and the Law of the Minimum is a useful predictor of mycorrhizal phenotype. In our experimental grasslands arbuscular mycorrhizas can ameliorate P-limitation but not N-limitation.

10astoichiometry1 aJohnson, N.C.1 aWilson, G.T.1 aWilson, J.A.1 aMiller, R.M.1 aBowker, M. uhttps://nph.onlinelibrary.wiley.com/doi/full/10.1111/nph.1317202272nas a2200181 4500008004100000245008800041210006900129300001500198490000700213520170300220100001101923700001801934700001701952700001701969700002401986700001802010856006202028 2013 eng d00aPatterns of diversity and adaptation in Glomeromycota from three prairie grasslands0 aPatterns of diversity and adaptation in Glomeromycota from three a2573 -25870 v223 a

Arbuscular mycorrhizal (AM) fungi are widespread root symbionts that often improve the fitness of their plant hosts. We tested whether local adaptation in mycorrhizal symbioses would shape the community structure of these root symbionts in a way that maximizes their symbiotic functioning. We grew a native prairie grass (Andropogon gerardii) with all possible combinations of soils and AM fungal inocula from three different prairies that varied in soil characteristics and disturbance history (two native prairie remnants and one recently restored). We identified the AM fungi colonizing A. gerardii roots using PCR amplification and cloning of the small subunit rRNA gene. We observed 13 operational taxonomic units (OTUs) belonging to six genera in three families. Taxonomic richness was higher in the restored than the native prairies with one member of the Gigaspora dominating the roots of plants grown with inocula from native prairies. Inoculum source and the soil environment influenced the composition of AM fungi that colonized plant roots. Correspondingly, host plants and AM fungi responded significantly to the soil–inoculum combinations such that home fungi often had the highest fitness and provided the greatest benefit to A. gerardii. Similar patterns were observed within the soil–inoculum combinations originating from two native prairies, where five sequence types of a single Gigaspora OTU were virtually the only root colonizers. Our results indicate that indigenous assemblages of AM fungi were adapted to the local soil environment and that this process occurred both at a community scale and at the scale of fungal sequence types within a dominant OTU.

1 aJi, B.1 aGehring, C.A.1 aWilson, G.T.1 aMiller, R.M.1 aFlores-Renteria, L.1 aJohnson, N.C. uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/mec.1226800474nas a2200145 4500008004100000245005200041210005200093260003200145300001100177100001700188700001700205700001800222700001800240856007000258 2012 eng d00aArbuscular Mycorrhizae and Grassland Ecosystems0 aArbuscular Mycorrhizae and Grassland Ecosystems aOxford, UKbWiley-Blackwell a59 -851 aMiller, R.M.1 aWilson, G.T.1 aJohnson, N.C.1 aSouthwood, D. uhttps://onlinelibrary.wiley.com/doi/abs/10.1002/9781118314364.ch302196nas a2200217 4500008004100000245008100041210006900122300001500191490000800206520156800214653001601782653002301798653001401821653001501835100001801850700001701868700001501885700001701900700001701917856004401934 2010 eng d00aResource limitation is a driver of local adaptation in mycorrhizal symbioses0 aResource limitation is a driver of local adaptation in mycorrhiz a2093 -20980 v1073 a

Symbioses may be important mechanisms of plant adaptation to their environment. We conducted a reciprocal inoculation experiment to test the hypothesis that soil fertility is a key driver of local adaptation in arbuscular mycorrhizal (AM) symbioses. Ecotypes of Andropogon gerardii from phosphorus-limited and nitrogen-limited grasslands were grown with all possible “home and away” combinations of soils and AM fungal communities. Our results indicate that Andropogon ecotypes adapt to their local soil and indigenous AM fungal communities such that mycorrhizal exchange of the most limiting resource is maximized. Grasses grown in home soil and inoculated with home AM fungi produced more arbuscules (symbiotic exchange structures) in their roots than those grown in away combinations. Also, regardless of the host ecotype, AM fungi produced more extraradical hyphae in their home soil, and locally adapted AM fungi were, therefore, able to sequester more carbon compared with nonlocal fungi. Locally adapted mycorrhizal associations were more mutualistic in the two phosphorus-limited sites and less parasitic at the nitrogen-limited site compared with novel combinations of plants, fungi, and soils. To our knowledge, these findings provide the strongest evidence to date that resource availability generates evolved geographic structure in symbioses among plants and soil organisms. Thus, edaphic origin of AM fungi should be considered when managing for their benefits in agriculture, ecosystem restoration, and soil-carbon sequestration.

10acoevolution10ageographic mosaics10amutualism10aparasitism1 aJohnson, N.C.1 aWilson, G.T.1 aBowker, M.1 aWilson, J.A.1 aMiller, R.M. uhttps://www.pnas.org/content/107/5/209300646nas a2200181 4500008004100000245012500041210006900166300001300235490000700248100001800255700002000273700001900293700001600312700001600328700002100344700001700365856008200382 2009 eng d00aMysterious mycorrhizae? A field trip and classroom experiment to demystify the symbioses formed between plants and fungi0 aMysterious mycorrhizae A field trip and classroom experiment to  a424 -4290 v711 aJohnson, N.C.1 aChaudhary, V.B.1 aHoeksema, J.D.1 aMoore, J.M.1 aPringle, A.1 aUmbanhowar, J.A.1 aWilson, G.T. uhttps://ecommons.luc.edu/cgi/viewcontent.cgi?article=1002&context=ies_facpubs02661nas a2200157 4500008004100000245010800041210006900149300001500218490000700233520212100240100001802361700001802379700001602397700001602413856007402429 2008 eng d00aPlant winners and losers during grassland N eutrophication differ in biomass allocation and mycorrhizas0 aPlant winners and losers during grassland N eutrophication diffe a2868 -28780 v893 a

Human activities release tremendous amounts of nitrogenous compounds into the atmosphere. Wet and dry deposition distributes this airborne nitrogen (N) on otherwise pristine ecosystems. This eutrophication process significantly alters the species composition of native grasslands; generally a few nitrophilic plant species become dominant while many other species disappear. The functional equilibrium model predicts that, compared to species that decline in response to N enrichment, nitrophilic grass species should respond to N enrichment with greater biomass allocation aboveground and reduced allocation to roots and mycorrhizas. The mycorrhizal feedback hypothesis states that the composition of mycorrhizal fungal communities may influence the composition of plant communities, and it predicts that N enrichment may generate reciprocal shifts in the species composition of mycorrhizal fungi and plants. We tested these hypotheses with experiments that compared biomass allocation and mycorrhizal function of four grass ecotypes (three species), two that gained and two that lost biomass and cover in response to long-term N enrichment experiments at Cedar Creek and Konza Long-Term Ecological Research grasslands. Local grass ecotypes were grown in soil from their respective sites and inoculated with whole-soil inoculum collected from either fertilized (FERT) or unfertilized (UNFERT) plots. Our results strongly support the functional equilibrium model. In both grassland systems the nitrophilic grass species grew taller, allocated more biomass to shoots than to roots, and formed fewer mycorrhizas compared to the grass species that it replaced. Our results did not fully support the hypothesis that N-induced changes in the mycorrhizal fungal community were drivers of the plant community shifts that accompany N eutrophication. The FERT and UNFERT soil inoculum influenced the growth of the grasses differently, but this varied with site and grass ecotype in both expected and unexpected ways suggesting that ambient soil fertility or other factors may be interacting with mycorrhizal feedbacks.

1 aJohnson, N.C.1 aRowland, D.L.1 aCorkidi, L.1 aAllen, E.B. uhttps://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/07-1394.102886nas a2200145 4500008004100000245010600041210006900147300001300216490000700229520231900236100002802555700001802583700001602601856012302617 2007 eng d00aMycorrhizal community dynamics following nitrogen fertilization: A cross site test in five grasslands0 aMycorrhizal community dynamics following nitrogen fertilization  a524 -5440 v773 aArbuscular mycorrhizal fungi (AMF) are considered both ecologically and physiologically important to many plant communities. As a result, any alteration in AMF community structure following soil nitrogen (N) enrichment may impact plant community function and contribute to widespread changes in grassland productivity. We evaluated the responses of AMF communities to N fertilization (≥100 kg N·ha−1·yr−1) in five perennial grasslands within the Long-Term Ecological Research network to generate a broader understanding of the drivers contributing to AMF species richness and diversity with increasing soil N fertility, and subsequent effects to host-plant communities. AMF spore and hyphal community data at three mesic sites (Cedar Creek, Kellogg Biological Station, Konza Prairie) and two semiarid sites (Sevilleta, Shortgrass Steppe) were collected over two consecutive years and used to test four hypotheses about AMF responses to N fertilization. Under ambient soil N, plant annual net primary productivity and soil phosphorus (P) were strongly related to climatic differences in AMF communities (semiarid vs. mesic). Following N fertilization, the drivers of AMF community structure were soil N availability, N:P supply ratio, and host-plant photosynthetic strategy (C3 vs. C4) but not climate. In P-rich soils (low N:P), N fertilization reduced AMF productivity, species richness, and diversity and intensified AMF community convergence due to the loss of rare AMF species and the increased abundance of Glomus species. In P-limited soils (high N:P), AMF productivity, species richness, and diversity increased with N fertilization; the most responsive AMF taxa were Acaulospora, Scutellospora, and Gigaspora. Soil N or N:P × host-plant (C3, C4) interactions further modified these responses: AMF hyphae (primarily Gigasporaceae) associated with C3 plants increased in abundance with N fertilization, whereas C4 plants hosted nitrophilous Glomus species. Such responses were independent of the duration or quantity of N fertilization, or the time since cessation of N fertilization. This synthesis provides a new understanding of AMF community patterns and processes, and it identifies three key drivers (soil N, N:P, host plant) of AMF community structure that may be tested in other communities.1 aEgerton-Warburton, L.M.1 aJohnson, N.C.1 aAllen, E.B. uhttp://lter.konza.ksu.edu/content/mycorrhizal-community-dynamics-following-nitrogen-fertilization-cross-site-test-five02929nas a2200169 4500008004100000245009100041210006900132300001500201490000700216520232100223100001802544700001802562700001602580700002802596700001602624856011902640 2003 eng d00aNitrogen enrichment alters mycorrhizal allocation at five mesic to semiarid grasslands0 aNitrogen enrichment alters mycorrhizal allocation at five mesic  a1895 -19080 v843 aArbuscular mycorrhizal (AM) fungi are integral components of grasslands because most plants are associated with interconnected networks of AM hyphae. Mycorrhizae generally facilitate plant uptake of nutrients from the soil. However, mycorrhizal associations are known to vary in their mutualistic function, and there is currently no metric that links AM functioning with fungal colonization of roots. Mycorrhizal structures differ in their physiological and ecological functioning, so changes in AM allocation to intraradical (inside roots) and extraradical (in soil) structures may signal shifts in mycorrhizal function. We hypothesize that the functional equilibrium model applies to AM fungi and that fertilization should reduce allocation to arbuscules, coils, and extraradical hyphae, the fungal structures that are directly involved in nutrient acquisition and transfer to plants. This study compared AM responses to experimental N enrichment at five grasslands distributed across North America. Samples were collected from replicated N-enriched (and some P-enriched) and control plots throughout the growing season for three years. Intraradical AM structures were measured in over 1400 root samples, extraradical hyphal density was measured in over 590 soil samples, and spore biovolume was analyzed in over 400 soil samples. There were significant site × N interactions for spore biovolume, extraradical hyphae, intraradical hyphae, and vesicles. Nitrogen enrichment strongly decreased AM structures at Cedar Creek, the site with the lowest soil N:P, and it increased AM structures at Konza Prairie, the site with the highest soil N:P. As predicted by the functional equilibrium model, in soils with sufficient P, relative allocation to arbuscules, coils, and extraradical hyphae was generally reduced by N enrichment. Allocation to spores and hyphae was most sensitive to fertilization. At the mesic sites, this response was associated with a shift in the relative abundance of Gigasporaceae within AM fungal communities. This study demonstrates that N enrichment impacts mycorrhizal allocation across a wide range of grassland ecosystems. Such changes are important because they suggest an alteration in mycorrhizal functioning that, in turn, may impact plant community composition and ecosystem function.1 aJohnson, N.C.1 aRowland, D.L.1 aCorkidi, L.1 aEgerton-Warburton, L.M.1 aAllen, E.B. uhttp://lter.konza.ksu.edu/content/nitrogen-enrichment-alters-mycorrhizal-allocation-five-mesic-semiarid-grasslands