US EPA

3851222 

Journal Article 

Cross-biome assessment of gross soil nitrogen cycling in California ecosystems 

Yang, WH; Ryals, RA; Cusack, DF; Silver, WL 

2017 

1 

Soil Biology and Biochemistry
ISSN: 0038-0717
EISSN: 1879-3428 

PERGAMON-ELSEVIER SCIENCE LTD 

OXFORD 

107 

144-155 

10.1016/j.soilbio.2017.01.004 

WOS:000395213500017 

is supplemented by 3982560 : Supplementary materials

Microbial transformations of nitrogen (N) largely determine whether N is retained in ecosystems via net primary productivity or lost via gaseous emissions and leaching. The controls on soil N cycling are often studied at single locales, making it difficult to predict N cycling at regional to global scales. We hy-pothesized that contemporary soil properties exhibit consistent relationships with instantaneous gross N cycling rates across diverse biomes that create a continuum in these properties. We measured ex situ gross N cycling rates and soil properties at 33 study sites representing five biome classifications in California including deserts, grasslands, shrublands, forest, and wetlands. Desert soils had significantly lower total N, organic carbon (C), microbial biomass N, and soil moisture as well as higher pH than all other biomes, whereas forests and wetlands had significantly lower soil nitrate (NO3 (-)) concentrations (P < 0.001 for all). Gross mineralization rates were best predicted by the combination of soil moisture and soil C:N ratios (R-2 = 0.46), which exerted positive and negative controls, respectively. Grasslands exhibited marginally higher gross mineralization than all other biomes, whereas deserts had the lowest rates due to low soil moisture (P = 0.09). Gross nitrification rates were positively correlated to soil NO3 concentrations (R-2 = 0.34) and negatively correlated to soil C:N ratios (R2 = 0.31). The negative relationship between gross nitrification and soil C:N ratios was driven by forest soils, which had significantly higher C:N ratios and lower gross nitrification than all other biomes (P < 0.05). Dissimilatory NOy reduction to NH4- (DNRA) occurred in soils from all biomes. The strong positive correlation between DNRA rates and soil NO3- (R-2 = 0.41) suggests NO3- limitation of DNRA. Predictable patterns in gross N cycling across biomes in California suggest that contemporary soil properties are important drivers of instantaneous soil N cycling rates that integrate over differences in vegetation type, atmospheric N deposition rates, and local climate. (C) 2017 Elsevier Ltd. All rights reserved. 

Dissimilatory nitrate reduction to; ammonium; Gross nitrogen cycling; Nitrogen mineralization; Nitrification; Nitrogen; Isotope pool dilution