Afforestation alters the composition of functional genes in soil and biogeochemical processes in South American grasslands.

Journal Article (Journal Article)

Soil microbes are highly diverse and control most soil biogeochemical reactions. We examined how microbial functional genes and biogeochemical pools responded to the altered chemical inputs accompanying land use change. We examined paired native grasslands and adjacent Eucalyptus plantations (previously grassland) in Uruguay, a region that lacked forests before European settlement. Along with measurements of soil carbon, nitrogen, and bacterial diversity, we analyzed functional genes using the GeoChip 2.0 microarray, which simultaneously quantified several thousand genes involved in soil carbon and nitrogen cycling. Plantations and grassland differed significantly in functional gene profiles, bacterial diversity, and biogeochemical pool sizes. Most grassland profiles were similar, but plantation profiles generally differed from those of grasslands due to differences in functional gene abundance across diverse taxa. Eucalypts decreased ammonification and N fixation functional genes by 11% and 7.9% (P < 0.01), which correlated with decreased microbial biomass N and more NH(4)(+) in plantation soils. Chitinase abundance decreased 7.8% in plantations compared to levels in grassland (P = 0.017), and C polymer-degrading genes decreased by 1.5% overall (P < 0.05), which likely contributed to 54% (P < 0.05) more C in undecomposed extractable soil pools and 27% less microbial C (P < 0.01) in plantation soils. In general, afforestation altered the abundance of many microbial functional genes, corresponding with changes in soil biogeochemistry, in part through altered abundance of overall functional gene types rather than simply through changes in specific taxa. Such changes in microbial functional genes correspond with altered C and N storage and have implications for long-term productivity in these soils.

Full Text

Duke Authors

Cited Authors

  • Berthrong, ST; Schadt, CW; Piñeiro, G; Jackson, RB

Published Date

  • October 2009

Published In

Volume / Issue

  • 75 / 19

Start / End Page

  • 6240 - 6248

PubMed ID

  • 19700539

Pubmed Central ID

  • PMC2753075

Electronic International Standard Serial Number (EISSN)

  • 1098-5336

International Standard Serial Number (ISSN)

  • 0099-2240

Digital Object Identifier (DOI)

  • 10.1128/aem.01126-09


  • eng