PATTERNS OF SOIL CHEMISTRY AND MICROBIAL COMMUNITIES ACROSS TEMPERATE DECIDUOUS FORESTS: SPECIES INVASION AND SITE CHARACTERISTICS
Date
2024-05
Authors
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Publisher
University of Delaware
Abstract
Forest soils are highly heterogeneous, complex environments. Within urban
forests, soils are subjected to a wide range of biotic and abiotic stressors that could
potentially alter soil chemical and microbial compositions. To understand the patterns
of soil chemistry and microbial community composition in urban forest soils with
respect to site identity and invasion by multiflora rose (Rosa multiflora), bulk
rhizosphere samples were collected from beneath R. multiflora, native spice bush
(Lindera benzoin), and uncovered soils in three proximate temperate deciduous forests
in Newark, Delaware, that exhibit similar overlying plant communities. Using
Illumina MiSeq next generation sequencing of extracted and amplified 16S rRNA
amplicons, soil bacterial communities were analyzed along with their corresponding
soil chemical properties with respect to forest site and shrub cover. Soil chemical
properties separated primarily by forest site, and they did not separate by shrub cover.
The most abundant bacterial phyla across all samples were the Proteobacteria,
Acidobacteria, Actinobacteria, Verrucomicrobiota, and Planctomycetota. Microbial
communities varied between sites at the genus taxonomic level but not the phylum
level. Additionally, one forest site had consistently higher microbial community
diversity indices than the other forests. In contrast, microbial communities differed
between shrub cover versus no cover at the phylum, but not genus, level. The most
notable difference in phylum relative abundance across shrub cover types was that the
Firmicutes were more abundant in uncovered soils than either shrub covers across all
three sites. Analysis of linear correlations between the relative abundances of bacterial
phyla and soil chemical properties revealed emergent trends that were only visible
across sites as well as trends that only existed within each site. Altogether, these
results suggest that the relationships between soil bacterial community composition
and soil chemical properties vary between spatial scales. It is likely that the scales of
forest composition from the whole site to local sampling locations act as filters to
microbial communities, which ultimately direct which bacteria can colonize a given
soil environment. Additionally, these data suggest that R. multiflora is not likely to
exert substantial modifications to soil chemical and microbiological properties in the
early stages of invasion where it is yet to dominate forest understories. Future studies
should be mindful of the baseline heterogeneity of soil chemical and microbial
compositions between forests, creating study designs that investigate the responses of
several forests to a specific stressor to ensure the validity of their generalizations and
conclusions across a forest macrosystem.