Differences in ectomycorrhizal community assembly between native and exotic pines are reflected in their enzymatic functional capacities

Abstract

Introducing exotic tree species for afforestation out of their natural range may alter the local ectomycorrhizal (ECM) fungal communities. The potential functional consequences shaped by exotic trees with recruited local ECM fungi rather than native trees remain unclear. This study examined (a) whether the composition and extracellular enzyme function of ECM fungal communities differed between native masson pine (Pinus massoniana) and exotic slash pine (Pinus elliottii) during seedling establishment; and (b) how differences in enzyme functioning were linked to the growth pattern of the host plants. Native (masson) and exotic (slash) pine seedlings were planted into soil cores collected from each study site. At three months growth, root tips were collected from seedlings and assayed for ECM fungal community composition using high-throughput sequencing, and functioning using single root tip assays for enzymes associated with N, P and C acquisition. ECM fungi on masson pines showed higher activities of nitrogen- (N-acetylglucosaminidase, 280–300%), phosphorus- (acid phosphatase, 105–152%), and cellulose (β-glucosidase, 204–235%; cellobiohydrolase, 142–255%) compound degrading enzymes compared to those on slash pines. Those differences was attributed to the host-specific performance of certain ECM fungal taxa, such as Rhizopogon spp. Information theory model selection showed that plant nutrient status in masson pines was correlated with the enzymatic contribution of Rhizopogon spp., whereas slash pines depended on a diverse enzyme palette from multiple ECM fungal taxa. Host identity strongly influenced ECM fungal community composition and extracellular enzymatic functions of specific ECM fungal taxa, which could feedback to host establishment and nutrient cycling processes of restored ecosystem. Therefore, the origin of afforestation tree species should be an important factor when selecting tree species for restoration of degraded lands.