Afforestation alters the composition of functional genes in soil and biogeochemical processes in South American grasslands.
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.
Berthrong
Sean T
ST
Biology Department, Duke University, Durham, North Carolina 27708, USA. sberthrong@gmail.com
Schadt
Christopher W
CW
Piñeiro
Gervasio
G
Jackson
Robert B
RB
D001419:Bacteria / Q000145:classification* / Q000235:genetics; D044822:Biodiversity; D002244:Carbon / Q000032:analysis; D002688:Chitinases / Q000235:genetics; D016000:Cluster Analysis; D004247:DNA / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification*; D005788:Gene Pool; D046228:Microarray Analysis; D009584:Nitrogen / Q000032:analysis; D020411:Oligonucleotide Array Sequence Analysis; D017385:Sequence Homology; D012987:Soil / Q000032:analysis*; D012988:Soil Microbiology; D013020:South America; D014197:Trees
D012987:Soil; D002244:Carbon; D004247:DNA; D002688:Chitinases; D009584:Nitrogen
Appl Environ Microbiol. 2009 May;75(10):3180-6
19304827
Appl Environ Microbiol. 2006 Jul;72(7):4931-41
16820490
Ecol Appl. 2009 Dec;19(8):2228-41
20014590
Appl Environ Microbiol. 2007 Nov;73(21):7059-66
17827313
Microb Ecol. 2006 Aug;52(2):159-75
16897303
Nat Rev Microbiol. 2006 Feb;4(2):102-12
16415926
Appl Environ Microbiol. 2006 Feb;72(2):1688-91
16461729
Appl Environ Microbiol. 2003 Apr;69(4):1928-35
12676666
Appl Environ Microbiol. 2003 Feb;69(2):926-32
12571013
Appl Environ Microbiol. 2001 Dec;67(12):5780-90
11722935
Appl Environ Microbiol. 2005 Jul;71(7):3753-60
16000786
Environ Microbiol. 2009 Jun;11(6):1518-26
19260937
Ecology. 2007 Sep;88(9):2162-73
17918395
ISME J. 2007 May;1(1):67-77
18043615
Nature. 2006 Aug 17;442(7104):806-9
16915287
Proc Natl Acad Sci U S A. 2006 Jan 17;103(3):626-31
16407148
ISME J. 2009 May;3(5):597-605
19148144
Science. 2008 Aug 1;321(5889):684-6
18669860
Science. 2008 May 23;320(5879):1034-9
18497287
Environ Microbiol. 2008 Nov;10(11):3057-69
18973624
Proc Natl Acad Sci U S A. 1998 Dec 8;95(25):14863-8
9843981
Appl Environ Microbiol. 2002 Aug;68(8):3818-29
12147477