Arbuscular mycorrhizal fungi on developing islands within a dynamic river floodplain: an investigation across successional gradients and soil depth |
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Authors: | Mary J Harner Nora Opitz Keith Geluso Klement Tockner Matthias C Rillig |
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Institution: | 1.Department of Biology,University of Nebraska-Kearney,Kearney,USA;2.Freie Universit?t Berlin, Institut für Biologie,Berlin,Germany;3.Leibniz-Institute of Freshwater Ecology and Inland Fisheries,Berlin,Germany |
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Abstract: | Most vascular plants form symbioses with mycorrhizal fungi that associate with roots and provide nutrients to hosts in exchange
for carbohydrates, as well as serve a range of other functions. Mycorrhizal fungi have been studied extensively in upland
ecosystems, but we know less about their ecology at aquatic-terrestrial interfaces, especially their distributions at depth.
Our objectives were to determine whether abundances of arbuscular mycorrhizal fungi (AMF) change as floodplain islands develop
and to describe vertical distributions of AMF from the forest floor to the water table along the freely flowing Tagliamento
River in northeastern Italy. We sampled surface sediments (0–10 cm) from three stages of island development on the floodplain—fresh
deposits, pioneer islands, and established islands. We also sampled sediments vertically (0–150 cm) from the ground surface
to the water table on an established island. We characterized abundance of AMF propagules (colonized roots, spores, and hyphae)
within sediments. Roots available to host fungi were absent on fresh deposits; however, some viable spores and hyphae were
available at these sites. Pioneer and established islands each had similar hyphal lengths (~860 cm cm−3) and colonized root lengths (~3 cm cm−3). Abundance of spores increased from depositional (3.5 ± 0.9 (±SE) cm−3) to pioneer (17 ± 6.1 cm−3) to established (32 ± 6.3 cm−3) islands. On an established island, AMF propagules were present at all depths sampled, including at the water table, providing
first documentation of these symbionts to such depths in a riparian setting. Mycorrhizal fungi likely link aquatic and terrestrial
habitats by connecting plants, soil, and ground water and may influence nutrient transfers among these subsystems. |
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