Abstract
Plant and fungal interactions drive successional trajectories within reforestation offering both mutualisms (ectomycorrhizal fungi [ECM]) and fungal pathogens. Appalachian forest and mine reclamation projects re-introducing American chestnut and chestnut hybrids will inevitably document the return of chestnut blight, resulting in cankers causing branch dieback and loss of photosynthetic tissue. Similar to herbivory, the loss of photosynthetic tissue may reduce ECM root colonization and cause changes in fungal species composition. To test this, 75 six-year-old established chestnut trees were selected to represent the following: (1) Healthy trees free of chestnut blight; (2) trees with cankers and 50% branch dieback; (3) trees that died prior to the fifth growing season. Each tree had a chestnut seed planted 24 cm from the base. ECM colonization of both the established parent trees (n = 50) and five-month-old seedlings (n = 64) were quantified and genera determined by fungal DNA sequencing of the internal transcribed (ITS) region. Healthier seven-year-old chestnuts trees had significantly more ECM roots than those trees infected with chestnut blight cankers. However, disease die-back on chestnut did not have an influence on community composition among the parent trees or the neighboring five month seedlings. Results also demonstrated that five-month-old seedlings neighboring healthy parent trees had greater ECM on roots (P = 0.002), were larger in size (P = 0.04), and had greater survival (P = 0.01). ECM genera such as Cortinarius, Russula and Scleroderma provided tree to seedling inoculation. ECM colonization by Cortinarius spp. resulted in larger chestnut plants and increased nitrogen foliar concentrations on the five month seedlings. It can be hypothesized that blight will aid in diversifying forest stand composition and these early ECM networks will help facilitate the survival of other native hardwoods that recruit into these sites over time.
Highlights
Plant and fungal interactions drive successional trajectories and community assembly within reforestation
A two-way permutational ANOVA on the ECM community matrices showed that differences in ECM communities existed between the two chestnut types (parent trees verses five-month seedlings; F(1,10) = 2.33, P = 0.03)
Early successional habitats are dynamic; ECM colonization is influenced by tree development and may facilitate the survival of other native hardwoods like oak, that associate with chestnut mycorrhiza as this stand develops [32,79]
Summary
Plant and fungal interactions drive successional trajectories and community assembly within reforestation. Mycorrhizal fungi create symbiotic relationships with tree roots and facilitate the transfer of water and nutrients in exchange for photosynthates [1]. Plant co-existence may be facilitated by various mycorrhizal associations, with specific symbionts providing access to limiting resources as succession progresses [2,3]. The development of common mycorrhizal networks (CMN) can facilitate seedling recruitment by shared nutrient transfer from plant to plant via source to sink, aiding in co-existence within guilds [2,4,5]. Fungal pathogens contribute to structuring plant communities by driving species above- and belowground turnover as plant succession progresses [6,7]. Root and wood rots maintain gap dynamics in forests contributing to resource availability, productivity and forest structure [11,12]
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