Original Article

Ecological Research

, Volume 26, Issue 1, pp 201-208

First online:

Plant effects on soil N mineralization are mediated by the composition of multiple soil organic fractions

  • Dario A. FornaraAffiliated withEnvironmental Sciences Research Institute, University of UlsterSoil and Ecosystem Ecology Laboratory, Lancaster Environment Centre, Lancaster University Email author 
  • , Richard BardgettAffiliated withSoil and Ecosystem Ecology Laboratory, Lancaster Environment Centre, Lancaster University
  • , Sibylle SteinbeissAffiliated withInstitute of Groundwater Ecology, Helmholtz Centre Munich
  • , Donald R. ZakAffiliated withSchool of Natural Resources and Environment, University of Michigan
  • , Gerd GleixnerAffiliated withMax-Planck-Institute for Biogeochemistry
  • , David TilmanAffiliated withDepartment of Ecology, Evolution, and Behavior, University of Minnesota

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Abstract

Despite the topic of soil nitrogen (N) mineralization being well-studied, very few studies have addressed the relative contribution of different plant and soil variables in influencing soil N mineralization rates, and thus the supply of inorganic N to plants. Here, we used data from a well-studied N-limited grassland to address the relative effects of six plant and soil variables on net and on gross rates of soil N mineralization. We also addressed whether plant effects on soil N mineralization were mediated by changes in C and N concentrations of multiple soil organic matter (SOM) fractions. Regression analyses show that key plant traits (i.e., plant C:N ratios and total root mass) were more important than total C and N concentrations of bulk soil in influencing N mineralization. This was mainly because plant traits influenced the C and N concentration (and C:N ratios) of different SOM fractions, which in turn were significantly associated with changes in net and gross N mineralization. In particular, C:N ratios of a labile soil fraction were negatively related to net soil N mineralization rates, whereas total soil C and N concentrations of more recalcitrant fractions were positively related to gross N mineralization. Our study suggests that changes in belowground N-cycling can be better predicted by simultaneously addressing how plant C:N ratios and root mass affect the composition and distribution of different SOM pools in N-limited grassland systems.

Keywords

Ecosystem process Nitrogen cycling Soil density fractionation Soil organic matter