New Phytologist
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Diversity and forest productivity in a changing climate Contents Summary 50 I. Introduction 50 II. Drivers of the diversity–productivity relationship 51 III. Patterns of the diversity–productivity relationship 55 IV. Responses of mixed stands to climate change 57 V. Conclusions 60 Acknowledgements 61 References 61 Summary Although the relationship between species diversity and biomass productivity has been extensively studied in grasslands, the impact of tree species diversity on forest productivity, as well as the main drivers of this relationship, are still under discussion. It is widely accepted that the magnitude of the relationship between tree diversity and forest stand productivity is context specific and depends on environmental conditions, but the underlying mechanisms of this relationship are still not fully understood. Competition reduction and facilitation have been identified as key mechanisms driving the diversity–productivity relationship. However, contrasting results have been reported with respect to the extent to which competition reduction and facilitation determine the diversity–productivity relationship. They appear to depend on regional climate, soil fertility, functional diversity of the tree species involved, and developmental stage of the forest. The purpose of this review is to summarize current knowledge and to suggest a conceptual framework to explain the various processes leading to higher productivity of species‐rich forests compared with average yields of their respective monocultures. This framework provides three pathways for possible development of the diversity–productivity relationship under a changing climate.
New Phytologist - Tập 221 Số 1 - Trang 50-66 - 2019
Dynamics of arbuscular mycorrhizal fungal community structure and functioning along a nitrogen enrichment gradient in an alpine meadow ecosystem Summary
Nitrogen (N) availability is increasing dramatically in many ecosystems, but the influence of elevated N on the functioning of arbuscular mycorrhizal (AM ) fungi in natural ecosystems is not well understood. We measured AM fungal community structure and mycorrhizal function simultaneously across an experimental N addition gradient in an alpine meadow that is limited by N but not by phosphorus (P). AM fungal communities at both whole‐plant‐community (mixed roots) and single‐plant‐species (Elymus nutans roots) scales were described using pyro‐sequencing, and the mycorrhizal functioning was quantified using a mycorrhizal‐suppression treatment in the field (whole‐plant‐community scale) and a glasshouse inoculation experiment (single‐plant‐species scale). Nitrogen enrichment progressively reduced AM fungal abundance, changed AM fungal community composition, and shifted mycorrhizal functioning towards parasitism at both whole‐plant‐community and E. nutans scales. N‐induced shifts in AM fungal community composition were tightly linked to soil N availability and/or plant species richness, whereas the shifts in mycorrhizal function were associated with the communities of specific AM fungal lineages. The observed changes in both AM fungal community structure and functioning across an N enrichment gradient highlight that N enrichment of ecosystems that are not P‐limited can induce parasitic mycorrhizal functioning and influence plant community structure and ecosystem sustainability.
New Phytologist - Tập 220 Số 4 - Trang 1222-1235 - 2018
Appropriate controls for vesicular–arbuscular mycorrhiza research SUMMARY Sunflower (Helianthus animus L.) and mustard (Brassica hirta Moench.) plants were grown in autoclaved soil to which was added various components of soil inoculum. Use of inocula containing mycorrhizal propagules ultimately resulted in growth promotions which were related to improved phosphorus nutrition. Inoculation with soil containing mycorrhizal propagules caused an initial growth depression in comparison with plants receiving no inoculation, but inoculation with washed spores did not. For several reasons, the growth depression caused by inoculation with soil was not attributable to mycorrhizal infection. First, the growth depression was evident before mycorrhizal infections had become established. Second, the growth depression was also evident when either soil or soil sievings, both lacking mycorrhizal propagules, were used. Third, similar growth depressions were observed in mustard. The results suggest that careful selection of appropriate controls for mycorrhizal plants must be made, particularly if the emphasis is on early phases of plant growth. Use of non‐sterile soil reduced the extent of mycorrhizal infection.
New Phytologist - Tập 111 Số 1 - Trang 35-44 - 1989
Perennial, but not annual legumes synergistically benefit from infection with arbuscular mycorrhizal fungi and rhizobia: a meta‐analysis Summary
Many plant species simultaneously interact with multiple symbionts, which can, but do not always, generate synergistic benefits for their host. We ask if plant life history (i.e. annual vs perennial) can play an important role in the outcomes of the tripartite symbiosis of legumes, arbuscular mycorrhizal fungi (AMF), and rhizobia. We performed a meta‐analysis of 88 studies examining outcomes of legume–AMF–rhizobia interactions on plant and microbial growth. Perennial legumes associating with AMF and rhizobia grew larger than expected based on their response to either symbiont alone (i.e. their response to co‐inoculation was synergistic). By contrast, annual legume growth with co‐inoculation did not differ from additive expectations. AMF and rhizobia differentially increased phosphorus (P) and nitrogen (N) tissue concentration. Rhizobium nodulation increased with mycorrhizal fungi inoculation, but mycorrhizal fungi colonization did not increase with rhizobium inoculation. Microbial responses to co‐infection were significantly correlated with synergisms in plant growth. Our work supports a balanced plant stoichiometry mechanism for synergistic benefits. We find that synergisms are in part driven by reinvestment in complementary symbionts, and that time‐lags in realizing benefits of reinvestment may limit synergisms in annuals. Optimization of microbiome composition to maximize synergisms may be critical to productivity, particularly for perennial legumes.
New Phytologist - Tập 233 Số 1 - Trang 505-514 - 2022
Size classes of root diameter and mycorrhizal fungal colonization in two temperate grassland communities SUMMARY This study addresses the hypothesis that the amount of fibrous roots (i.e., roots > 1.0 mm diameter) colonized by vesicular‐arbuscular mycorrhizal (VAM) fungi in grasslands is dependent upon root morphology. Two grassland communities with contrasting root system morphologies, a restored tallgrass prairie and an ungrazed pasture, were studied over a growing season. Although there was no difference in fibrous root biomass between the two communities, fibrous roots accounted for 99 % of the total root biomass in the pasture; but only 70 % of the total root biomass in the prairie. The length of fibrous roots was greater (P < 0.0001) in the pasture than in the prairie. Correspondingly, the mean diameter of roots in the pasture was 018 mm, but that in the prairie averaged 0.23 mm. Although the total length of fibrous roots colonized by mycorrhizal fungi did not differ between the two communities (P > 0.34), when the colonized lengths of roots within each of three size classes were compared, significant differences between the two communities were found. The ratio of the fraction of the root length colonized within a given diameter size class to the fraction of the total length of root with cortex occurring within that size class was used to compare the degree of association between roots and mycorrhizal colonization among the three diameter size classes. Changes in this ratio, termed the colonization index (CI), indicate that as the diameter size class of roots in a community increases, a greater proportion of the cortical root length within that size class is colonized by mycorrhizal fungi. Furthermore, despite community differences in the cortical and colonized root lengths within each diameter size class, the CI value for each root size class did not differ between communities. These findings suggest that in grasslands the degree of colonization by mycorrhizal fungi is more dependent upon the diameter size class distribution of the fibrous root systems than upon the species composition of the community.
New Phytologist - Tập 116 Số 1 - Trang 129-136 - 1990
Resource stoichiometry elucidates the structure and function of arbuscular mycorrhizas across scales Summary Despite the fact that arbuscular mycorrhizal (AM) associations are among the most ancient, abundant and important symbioses in terrestrial ecosystems, there are currently few unifying theories that can be used to help understand the factors that control their structure and function. This review explores how a stoichiometric perspective facilitates integration of three complementary ecological and evolutionary models of mycorrhizal structure and function. AM symbiotic function should be governed by the relative availability of carbon, nitrogen and phosphorus (trade balance model) and allocation to plant and fungal structures should depend on the availabilities of these resources (functional equilibrium model). Moreover, in an evolutionary framework, communities of plants and AM fungi are predicted to adapt to each other and their local soil environment (co‐adaptation model). Anthropogenic enrichment of essential resources in the environment is known to impact AM symbioses. A more predictive theory of AM structure and function will help us to better understand how these impacts may influence plant communities and ecosystem properties.
Contents
Summary
631
I.
Introduction 632
II.
Overview of ecological and evolutionary models from a stoichiometric perspective 632
III.
Carbon, nitrogen and phosphorus in AM symbioses 634
IV.
Trade balance and thresholds in the AM marketplace 635
V.
Optimal foraging and functional equilibrium in AM symbioses 638
VI.
Fungal life histories and resource utilization 640
VII.
Community feedbacks, co‐adaptation and ecosystem consequences 641
VIII.
The scaling‐up challenge 643
Acknowledgements 643
References 643
New Phytologist - Tập 185 Số 3 - Trang 631-647 - 2010
Fungal community analysis by high‐throughput sequencing of amplified markers – a user's guide Summary
Novel high‐throughput sequencing methods outperform earlier approaches in terms of resolution and magnitude. They enable identification and relative quantification of community members and offer new insights into fungal community ecology. These methods are currently taking over as the primary tool to assess fungal communities of plant‐associated endophytes, pathogens, and mycorrhizal symbionts, as well as free‐living saprotrophs. Taking advantage of the collective experience of six research groups, we here review the different stages involved in fungal community analysis, from field sampling via laboratory procedures to bioinformatics and data interpretation. We discuss potential pitfalls, alternatives, and solutions. Highlighted topics are challenges involved in: obtaining representative DNA /RNA samples and replicates that encompass the targeted variation in community composition, selection of marker regions and primers, options for amplification and multiplexing, handling of sequencing errors, and taxonomic identification. Without awareness of methodological biases, limitations of markers, and bioinformatics challenges, large‐scale sequencing projects risk yielding artificial results and misleading conclusions.
New Phytologist - Tập 199 Số 1 - Trang 288-299 - 2013
The UNITE database for molecular identification of fungi – recent updates and future perspectives
New Phytologist - Tập 186 Số 2 - Trang 281-285 - 2010
454 Pyrosequencing and Sanger sequencing of tropical mycorrhizal fungi provide similar results but reveal substantial methodological biases
New Phytologist - Tập 188 Số 1 - Trang 291-301 - 2010
Effects of NO (+ NO<sub>2</sub>) pollution on growth, nitrate reductase activities and associated protein contents in glasshouse lettuce grown hydroponically in winter with CO<sub>2</sub> enrichment summary Winter hydroponic growth of several lettuce cultivars under glass showed considerable inhibition (up to 47%) of growth after 6 wk exposure to concentrations of NO (+ NO2 450 nl −1 in total) typical of emissions from propane burners used for direct heating and CO2 enrichment. After a further 4 wk under similar conditions, however, these growth depressions were replaced by a swing into benefit so that, by harvest, pollutant‐exposed lettuces were bigger and had faster assimilation rates than those growing in clean CO2 ‐enriched air. This adaptation may partly be explained by enhanced use of NO2 ‐derived N by lettuce leaves, a consequence of increased nitrate reductase (NaR) activities and amounts of associated NaR proteins, despite adequate nitrate also being available in the hydroponic fluid. Rates of NaR activity in the roots, by contrast, were depressed by NO (+ NO2 ) pollution. NaR activities were highest in early afternoon in clean or polluted air but these daily patterns did not coincide with the content of NaR‐associated proteins determined by ELISA. Other mechanisms of modulating NaR activity must therefore be responsible.
New Phytologist - Tập 133 Số 3 - Trang 495-501 - 1996
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