Acid hydrolysis to partition plant material into decomposable and resistant fractions for use in the Rothamsted carbon model

Abstract Using various plant materials, we identified two conceptual pools of plant litter, decomposable plant material (DPM) and resistant plant material (RPM), in the Rothamsted Carbon Model (RothC) by comparing the default proportions of DPM and RPM in the RothC and proportions in plant material fractions as determined by two-step acid hydrolysis with H 2 SO 4 . We collected 37 plant samples from 15 species at six sites on arable land, grassland, or forest in Japan. Carbon in the plant materials was divided into three pools by acid hydrolysis: (a) Labile Pool I (LP I), obtained by hydrolysis with 5 N H 2 SO 4 at 105 °C for 30 min; (b) Labile Pool II (LP II), obtained by hydrolysis with 26 N H 2 SO 4 at room temperature overnight, and then with 2 N H 2 SO 4 at 105 °C for 3 h; and (c) Recalcitrant Pool (RP), the unhydrolyzed residue. The average proportion of LP I in crops and grasses was 59%, which was the same as the proportion of DPM defined in the RothC as the default value for crops and grasses. The remaining 41% (23% LP II+18% RP) was consequently the same as the RPM proportion defined in the RothC. Similarly, the average proportion of LP I in all tree leaves (19%) was very close to the proportion of DPM in the RothC (20%) for trees. These results indicate that DPM in the RothC can be identified as LP I from the acid hydrolysis analysis and RPM as LP II+RP. We conclude that, at least theoretically, the use of an independent DPM:RPM ratio, as determined by acid hydrolysis analysis for each plant material, should enable more reliable modeling of SOM dynamics than the use of default DPM:RPM values provided by the model, even though the practical advantages of this method require further evaluation.

[1]  W. McGill.  Review and Classification of Ten Soil Organic Matter (SOM) Models , 1996 .

[2]  H. Flessa,et al.  Stabilization of carbon from maize in a sandy soil in a long‐term experiment , 2003 .

[3]  J. Balesdent,et al.  The significance of organic separates to carbon dynamics and its modelling in some cultivated soils , 1996 .

[4]  M. Bernoux,et al.  Modeling Soil Carbon from Forest and Pasture Ecosystems of Amazon, Brazil , 2003 .

[5]  S. Waksman,et al.  A CRITICAL STUDY OF THE METHODS FOR DETERMINING THE NATURE AND ABUNDANCE OF SOIL ORGANIC MATTER , 1930 .

[6]  V. Vallejo,et al.  Examination of thermal and acid hydrolysis procedures in characterization of soil organic matter , 2000 .

[7]  A. Mamolos,et al.  Decomposition of dominant plant species litter in a semi-arid grassland , 2003 .

[8]  David S. Powlson,et al.  Evaluation of Soil Organic Matter Models using Existing, Long-Term Datasets , 1996 .

[9]  B. Christensen.  Matching Measurable Soil Organic Matter Fractions with Conceptual Pools in Simulation Models of Carbon Turnover: Revision of Model Structure , 1996 .

[10]  E. Vance,et al.  Calculating net primary production and annual input of organic matter to soil from the amount and radiocarbon content of soil organic matter , 1992 .

[11]  D. Jenkinson,et al.  RothC-26.3 - A Model for the turnover of carbon in soil , 1996 .

[12]  P. Grootes,et al.  Quantification of lignite- and vegetation-derived soil carbon using 14C activity measurements in a forested chronosequence , 2003 .

[13]  J. Skjemstad,et al.  Calibration of the Rothamsted organic carbon turnover model (RothC ver. 26.3), using measurable soil organic carbon pools , 2004 .

[14]  V. Vallejo,et al.  Labile and recalcitrant pools of carbon and nitrogen in organic matter decomposing at different depths in soil: an acid hydrolysis approach , 2002 .

[15]  J. Anderson,et al.  Decomposition in Terrestrial Ecosystems , 1979 .

[16]  D. Jenkinson,et al.  Model estimates of CO2 emissions from soil in response to global warming , 1991, Nature.

[17]  R. Bol,et al.  ESTIMATING NET PRIMARY PRODUCTION FROM MEASUREMENTS MADE ON SOIL ORGANIC MATTER , 1999 .

[18]  K. Paustian,et al.  Modeling the Measurable or Measuring the Modelable: A Hierarchical Approach to Isolating Meaningful Soil Organic Matter Fractionations , 1996 .

[19]  P. Brookes,et al.  AN EXTRACTION METHOD FOR MEASURING SOIL MICROBIAL BIOMASS C , 1987 .