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Temperature sensitivity of soil enzyme kinetics under N ‐fertilization in two temperate forests

2011; Wiley; Volume: 18; Issue: 3 Linguagem: Inglês

10.1111/j.1365-2486.2011.02545.x

1365-2486

Madeleine M. Stone, Marissa S. Weiss, Christine L. Goodale, Mary Beth Adams, Ivan J. Fernandez, Donovan P. German, Steven Allison,

Phytase and its Applications

Abstract 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 B ear B rook, M aine, and F ernow F orest, W est V irginia. We determined the V max and K m parameters for five hydrolytic enzymes: α ‐glucosidase, β ‐glucosidase, β ‐xylosidase, cellobiohydrolase, and N ‐ acetyl‐glucosaminidase. Temperature sensitivities of V max and K m 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 V max values and lower K m values; and (2) both V max and K m 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 V max values for all enzymes, particularly at F ernow. Nitrogen fertilization led to significantly lower K m values for all enzymes at B ear B rook, but variable K m responses at F ernow F orest. Both V max and K m were temperature sensitive, with Q 10 values ranging from 1.64–2.27 for enzyme V max and 1.04–1.93 for enzyme K m . No enzyme showed a significant interaction between N and temperature sensitivity for V max , and only β ‐xylosidase showed a significant interaction between N and temperature sensitivity for K m . Our study is the first to experimentally demonstrate a positive relationship between K m and temperature for soil enzymes. Higher temperature sensitivities for V max relative to K m imply that substrate degradation will increase with temperature. In addition, the V max and K m 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 K m .