Bacterial and fungal saprotrophs are strongly stimulated weeks to months after forest soil profile reconstruction

• Published in: Pedobiologia 2019-03, Vol.73, p.29-41
• Main Authors: Sukdeo, Nicole, Teen, Ewing, Rutherford, P. Michael, Massicotte, Hugues B., Egger, Keith N.
• Format: Article
• Language: English
• Subjects: Bacteria; Community composition; Decomposition; DNA metabarcoding; Forest floor organic material (FFOM); fungi; Hydrolase; Mycelial necromass; Saprotroph; Soil salvage
• ISSN: 0031-4056; 1873-1511
• DOI: 10.1016/j.pedobi.2019.01.001

•Soil rehabilitation treatments increased bacterial saprotroph abundance 14 days after implementation.•Rehabilitation treatments showed strong fungal saprotroph abundance 5 months after implementation.•Ectomycorrhizal mycelia were a major necromass input due to soil manipulation.•Several microbial genera stimulated by rehabilitation treatments are previously described as mycelial decomposers. The replacement of mineral soil and capping with salvaged forest floor organic material (FFOM) is a site rehabilitation method applied over belowground installations such as pipelines. Such installations, when placed in mature forest soils, can be expected to disrupt ectomycorrhizal fungal communities when root-associated mycelia and exploratory hyphae are damaged during excavation. Soil fungal communities, bacterial communities, and soil enzymatic repertoires may be variably impacted by different site preparation schemes after disturbance. We compared effects of three rehabilitation schemes on fungal community composition, bacterial community composition, and potential hydrolase activities (N-acetyl-β-d-glucosaminidase, acid phosphatase, and cellobiohydrolase) at two times (14 days and 5 months post-site preparation) and two sampling depths (FFOM/”upper” versus mineral/”lower” soil). We observed declines in FFOM-associated fungal biomass (ergosterol) and declines in ectomycorrhizal fungi abundance across all site rehabilitation schemes compared to intact control plots. Fungal community composition strongly shifted to saprotroph dominance (i.e. increased Mortierella, and Umbelopsis) in rehabilitated plots at 5 months, while bacterial community composition did not distinguish control plots from rehabilitation plots ones at either sampling time. Bacterial saprotrophs previously associated with mycelial necromass colonization were higher in abundance across multiple site preparation regimens compared to control plots at 14 days. Our results indicate that reductions in ectomycorrhizal fungal abundance were a dominant community property in recently reconstructed soil profiles. Increases in bacteria associated with recently deposited fungal necromass were detectable within days to weeks of implementing site rehabilitation, while fungal necromass colonizers became dominant 5 months post-rehabilitation. Potential hydrolase activities increased in the site preparation regimen where FFOM was mixed into mineral soil, when compared to mineral soil activities in control plots.