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@article{Cenini:2015:10.1007/s10533-015-0157-5,
author = {Cenini, VL and Fornara, DA and McMullan, G and Ternan, N and Lajtha, K and Crawley, MJ},
doi = {10.1007/s10533-015-0157-5},
journal = {Biogeochemistry},
pages = {301--313},
title = {Chronic nitrogen fertilization and carbon sequestration in grassland soils: evidence of a microbial enzyme link},
url = {http://dx.doi.org/10.1007/s10533-015-0157-5},
volume = {126},
year = {2015}
}

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TY  - JOUR
AB  - Chronic nitrogen (N) fertilization can greatly affect soil carbon (C) sequestration by altering biochemical interactions between plant detritus and soil microbes. In lignin-rich forest soils, chronic N additions tend to increase soil C content partly by decreasing the activity of lignin-degrading enzymes. In cellulose-rich grassland soils it is not clear whether cellulose-degrading enzymes are also inhibited by N additions and what consequences this might have on changes in soil C content. Here we address whether chronic N fertilization has affected (1) the C content of light versus heavier soil fractions, and (2) the activity of four extracellular enzymes including the C-acquiring enzyme β-1,4-glucosidase (BG; necessary for cellulose hydrolysis). We found that 19 years of chronic N-only addition to permanent grassland have significantly increased soil C sequestration in heavy but not in light soil density fractions, and this C accrual was associated with a significant increase (and not decrease) of BG activity. Chronic N fertilization may increase BG activity because greater N availability reduces root C:N ratios thus increasing microbial demand for C, which is met by C inputs from enhanced root C pools in N-only fertilized soils. However, BG activity and total root mass strongly decreased in high pH soils under the application of lime (i.e. CaCO3), which reduced the ability of these organo-mineral soils to gain more C per units of N added. Our study is the first to show a potential ‘enzyme link’ between (1) long-term additions of inorganic N to grassland soils, and (2) the greater C content of organo-mineral soil fractions. Our new hypothesis is that the ‘enzyme link’ occurs because (a) BG activity is stimulated by increased microbial C demand relative to N under chronic fertilization, and (b) increased BG activity causes more C from roots and from microbial metabolites to accumulate and stabilize into organo-mineral C fractions. We su
AU  - Cenini,VL
AU  - Fornara,DA
AU  - McMullan,G
AU  - Ternan,N
AU  - Lajtha,K
AU  - Crawley,MJ
DO  - 10.1007/s10533-015-0157-5
EP  - 313
PY  - 2015///
SN  - 1573-515X
SP  - 301
TI  - Chronic nitrogen fertilization and carbon sequestration in grassland soils: evidence of a microbial enzyme link
T2  - Biogeochemistry
UR  - http://dx.doi.org/10.1007/s10533-015-0157-5
UR  - http://hdl.handle.net/10044/1/40739
VL  - 126
ER  -

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