Arbuscular mycorrhiza along forest soil sequences differing in P-availability

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The trade balance model postulates that arbuscular mycorrhizal (AM) plants become increasingly dependent on their fungal symbionts as P availability declines. Consequently, the importance of AM associations may be expected to increase in ecosystems of low P availability. Through the combination of AM community measurements and detailed assessment of soil P pools, we expect to gain a radically new insight into which pools can be accessed by keystone symbionts like AM fungi. Beyond this we expect novel results on the diversity and abundance of this group of organisms in this ‘non-classical’ ecosystem for these symbionts. We hypothesize that AM fungi, as main agents of P acquisition in many plants, will increase in abundance and diversity (in the soil and roots) along the P depletion sequences in the understory, and will hence increasingly contribute to P recycling. For this aim we aim to assess in addition to AMF abundance (hyphal length and root colonization) AMF diversity via pyrosequencing. This may stimulate examination of other such ‘non-traditional’ systems; perhaps they, too, harbor a wealth of unknown AM fungal diversity. An additional greenhouse experiment will allow us to quantify the amount of P uptake by the plant via AMF hyphae, which to our knowledge was never done in this type of ecosystems.