Soil disturbance alters plant community composition and decreases mycorrhizal carbon allocation in a sandy grassland |
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Authors: | Schnoor Tim Krone Mårtensson Linda-Maria Olsson Pål Axel |
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Institution: | (1) Plant Ecology and Systematics, Department of Biology, Lund University, The Ecology Building, S?lvegatan 47, 223 62 Lund, Sweden |
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Abstract: | We have studied how disturbance by ploughing and rotavation affects the carbon (C) flow to arbuscular mycorrhizal (AM) fungi
in a dry, semi-natural grassland. AM fungal biomass was estimated using the indicator neutral lipid fatty acid (NLFA) 16:1ω5,
and saprotrophic fungal biomass using NLFA 18:2ω6,9. We labeled vegetation plots with 13CO2 and studied the C flow to the signature fatty acids as well as uptake and allocation in plants. We found that AM fungal biomass
in roots and soil decreased with disturbance, while saprotrophic fungal biomass in soil was not influenced by disturbance.
Rotavation decreased the 13C enrichment in NLFA 16:1ω5 in soil, but 13C enrichment in the AM fungal indicator NLFA 16:1ω5 in roots or soil was not influenced by any other disturbance. In roots,
13C enrichment was consistently higher in NLFA 16:1ω5 than in crude root material. Grasses (mainly Festuca brevipila) decreased as a result of disturbance, while non-mycorrhizal annual forbs increased. This decreases the potential for mycorrhizal
C sequestration and may have been the main reason for the reduced mycorrhizal C allocation found in disturbed plots. Disturbance
decreased the soil ammonium content but did not change the pH, nitrate or phosphate availability. The overall effect of disturbance
on C allocation was that more of the C in AM fungal mycelium was directed to the external phase. Furthermore, the functional
identity of the plants seemed to play a minor role in the C cycle as no differences were seen between different groups, although
annuals contained less AM fungi than the other groups. |
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