Exotic earthworms alter soil microbial community composition and function

• Published in: Soil biology & biochemistry Vol. 67; pp. 263 - 270
• Main Authors: Dempsey, Mark A., Fisk, Melany C., Yavitt, Joseph B., Fahey, Timothy J., Balser, Teri C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01.12.2013; Elsevier
• Subjects: Agronomy. Soil science and plant productions; bacteria; Biochemistry and biology; Biological and medical sciences; carbon; carbon nitrogen ratio; Chemical, physicochemical, biochemical and biological properties; community structure; earthworms; enzyme activity; enzymes; Exotic earthworms; Fundamental and applied biological sciences. Psychology; hardwood forests; metabolism; Microbiology; mineral soils; mycorrhizal fungi; nitrogen; Northern hardwood forest; organic horizons; organic matter; Phospholipid fatty acids; Physics, chemistry, biochemistry and biology of agricultural and forest soils; saprotrophs; Soil C:N; Soil carbon; Soil enzyme activity; Soil microbial community; Soil science; temperate forests; Zoology (interactions between soil fauna and agricultural or forest soils); New York; ANW, USA, New York; Soil microbial community; Soil enzyme activity; Phospholipid fatty acids; Soil C:N; Northern hardwood forest; Exotic earthworms; Soil carbon; Community structure; Microbial activity; Deciduous forest; Fauna; Phospholipid; Fatty acids; Carbon; Annelida; Oligochaeta; Earthworm; Soils; Enzymatic activity; Macrofauna; Soil science; Invertebrata; Microbial community
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2013.09.009

Exotic earthworms can profoundly alter soil carbon (C) and nitrogen (N) dynamics in northern temperate forests, but the mechanisms explaining these responses are not well understood. We compared the soil microbial community (SMC) composition (measured as PLFAs) and enzyme activity between paired earthworm-invaded and earthworm-free plots in northern hardwood forests of New York, USA. We hypothesized that differences in SMCs and enzyme activity between plots would correspond with differences in soil C content and C:N ratios. Relative abundance of several bacterial (mostly gram-positive) PLFAs was higher and that of two fungal PLFAs was lower in earthworm compared to reference plots, largely because of earthworm incorporation of the organic horizon into mineral soil. In surface mineral soil earthworms increased arbuscular mycorrhizal fungi (AMF) and gram-positive bacterial PLFAs, and decreased fungal (mostly saprotrophic) and several bacterial (gram-negative and non-specific) PLFAs. Earthworms also increased the activities of cellulolytic relative to lignolytic enzymes in surface mineral soil, and the relationships between enzyme activities and components of the SMC suggest a substrate-mediated effect on the SMC and its metabolism of C. A highly significant relationship between components of the SMC and soil C:N also suggests that earthworms reduce soil C:N through functional and compositional shifts in the SMC. Finally, changes in AMF abundances were linked to phosphatase activity, suggesting that earthworms do not necessarily inhibit P-acquisition by AMF-associated plants in our study system. We conclude that the combined influence of earthworm-related changes in physical structure, accessibility and chemistry of organic matter, and relative abundance of certain groups of fungi and bacteria promote C metabolism, in particular by increasing the activities of cellulolytic vs. lignolytic enzymes. •Earthworms increased abundance of many bacterial relative to most fungal indicators.•Abundance of arbuscular mycorrhizal fungi increased by earthworms.•Earthworms increased activities of cellulolytic compared to lignolytic enzymes.•Changes in enzyme activities contribute to more complete carbon metabolism.•Soil microbial community composition correlated with enzyme activity and soil C:N.