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1326123 
Journal Article 
Temperature sensitivity of soil enzyme kinetics under N-fertilization in two temperate forests 
Stone, MM; Weiss, MS; Goodale, CL; Adams, MB; Fernandez, IJ; German, DP; Allison, SD 
2012 
Yes 
Global Change Biology
ISSN: 1354-1013
EISSN: 1365-2486 
WILEY 
HOBOKEN 
18 
3 
1173-1184 
WOS:000300671600031 
Soil microbes produce extracellular enzymes that degrade
carbon (C)-containing polymers in soil organic matter. Because extracellular enzyme activities
may be sensitive to both increased nitrogen (N) and temperature change, we measured the effect of
long-term N addition and short-term temperature variation on enzyme kinetics in soils from
hardwood forests at Bear Brook, Maine, and Fernow Forest, West Virginia. We determined the Vmax
and Km parameters for five hydrolytic enzymes: a-glucosidase, beta-glucosidase, beta-xylosidase,
cellobiohydrolase, and N-acetyl-glucosaminidase. Temperature sensitivities of Vmax and Km were
assessed within soil samples subjected to a range of temperatures. We hypothesized that (1) N
additions would cause microbial C limitation, leading to higher enzyme Vmax values and lower Km
values; and (2) both Vmax and Km would increase at higher temperatures. Finally, we tested
whether or not temperature sensitivity of enzyme kinetics is mediated by N addition. Nitrogen
addition significantly or marginally significantly increased Vmax values for all enzymes,
particularly at Fernow. Nitrogen fertilization led to significantly lower Km values for all
enzymes at Bear Brook, but variable Km responses at Fernow Forest. Both Vmax and Km were
temperature sensitive, with Q10 values ranging from 1.642.27 for enzyme Vmax and 1.041.93 for
enzyme Km. No enzyme showed a significant interaction between N and temperature sensitivity for
Vmax, and only beta-xylosidase showed a significant interaction between N and temperature
sensitivity for Km. Our study is the first to experimentally demonstrate a positive relationship
between Km and temperature for soil enzymes. Higher temperature sensitivities for Vmax relative
to Km imply that substrate degradation will increase with temperature. In addition, the Vmax and
Km responses to N indicate greater substrate degradation under N addition. Our results suggest
that increasing temperatures and N availability in forests of the northeastern US will lead to
increased hydrolytic enzyme activity, despite the positive temperature sensitivity of Km. 
carbon cycle; decomposition; enzyme kinetics; extracellular enzyme; microbe; nitrogen fertilization; soil warming