Mycorrhizal fungi involved in C transfer among pines and Oaks

Although gaining much attention in recent years, it is unclear whether mycorrhizal fungi distribute meaningful amounts of resources among trees in ways that increase the fitness of the receiving trees. Hence, we used shaded and sunlit pairs of inter- and intra-species Pinus halepensis and Quercus calliprinos saplings growing outdoors in forest soil. Carbon transfer was measured using pulse labeling with 13CO2 and the mycorrhizal community of each tree was identified by DNA barcoding. Although we did not observe any growth benefits, shaded recipient oaks received carbon from their sunlit pine neighbors and exhibited higher levels of root Non-Structural Carbohydrates (NSC) compared to their control counterparts, which were not connected belowground. Furthermore, sunlit pines connected to shaded oaks were depleted of their starch pools. Conjointly, our results link specific mycorrhizal species to belowground C transfer and suggest C-driven fitness costs and benefits to the trees.