title: Rapid prediction of particulate, humus and resistant fractions of soil organic carbon in reforested lands using infrared spectroscopy.
abstract: Reforestation of agricultural lands with mixed-species environmental plantings can effectively sequester C. While accurate and efficient methods for predicting soil organic C content and composition have recently been developed for soils under agricultural land uses, such methods under forested land uses are currently lacking. This study aimed to develop a method using infrared spectroscopy for accurately predicting total organic C (TOC) and its fractions (particulate, POC; humus, HOC; and resistant, ROC organic C) in soils under environmental plantings. Soils were collected from 117 paired agricultural-reforestation sites across Australia. TOC fractions were determined in a subset of 38 reforested soils using physical fractionation by automated wet-sieving and13C nuclear magnetic resonance (NMR) spectroscopy. Mid- and near-infrared spectra (MNIRS, 6000-450 cm-1) were acquired from finely-ground soils from environmental plantings and agricultural land. Satisfactory prediction models based on MNIRS and partial least squares regression (PLSR) were developed for TOC and its fractions. Leave-one-out cross-validations of MNIRS-PLSR models indicated accurate predictions (R2> 0.90, negligible bias, ratio of performance to deviation > 3) and fraction-specific functional group contributions to beta coefficients in the models. TOC and its fractions were predicted using the cross-validated models and soil spectra for 3109 reforested and agricultural soils. The reliability of predictions determined using k-nearest neighbour score distance indicated that >80% of predictions were within the satisfactory inlier limit. The study demonstrated the utility of infrared spectroscopy (MNIRS-PLSR) to rapidly and economically determine TOC and its fractions and thereby accurately describe the effects of land use change such as reforestation on agricultural soils.
authors.affiliation: School of Ecosystem and Forest Sciences, The University of Melbourne, Richmond, VIC 3121, Australia. Electronic address: dineshbm@unimelb.edu.au.
authors.forename: Dinesh B
authors.initials: DB
authors.lastname: Madhavan
authors.affiliation: CSIRO Agriculture, Glen Osmond, SA 5064, Australia.
authors.forename: Jeff A
authors.initials: JA
authors.lastname: Baldock
authors.affiliation: Fenner School of Environment and Society, Australian National University, Acton, ACT 2601, Australia.
authors.forename: Zoe J
authors.initials: ZJ
authors.lastname: Read
authors.affiliation: School of Ecosystem and Forest Sciences, The University of Melbourne, Richmond, VIC 3121, Australia.
authors.forename: Simon C
authors.initials: SC
authors.lastname: Murphy
authors.affiliation: School of Life and Environmental Sciences, Deakin University, Burwood, VIC 3125, Australia; Institute for Applied Ecology, University of Canberra, Bruce, ACT 2617, Australia.
authors.forename: Shaun C
authors.initials: SC
authors.lastname: Cunningham
authors.affiliation: School of Biological Sciences, The University of Western Australia, Crawley, WA 6009, Australia; Forest & Nature Laboratory, Ghent University, BE-9090, Gontrode-Melle, Belgium.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Perring
authors.affiliation: Department of Environment, Water and Natural Resources, Adelaide, SA 5001, Australia.
authors.forename: Tim
authors.initials: T
authors.lastname: Herrmann
authors.affiliation: Agri-Science Queensland, Department of Agriculture and Fisheries, Sippy Downs, QLD 4556, Australia.
authors.forename: Tom
authors.initials: T
authors.lastname: Lewis
authors.affiliation: School of Agriculture, Food and Wine, University of Adelaide, Waite Campus, PMB 1, Glen Osmond, SA 5064, Australia.
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Cavagnaro
authors.affiliation: CSIRO Agriculture and CSIRO Land and Water, Clayton South, VIC 3169, Australia.
authors.forename: Jacqueline R
authors.initials: JR
authors.lastname: England
authors.affiliation: CSIRO Agriculture and CSIRO Land and Water, Canberra, ACT 2601, Australia.
authors.forename: Keryn I
authors.initials: KI
authors.lastname: Paul
authors.affiliation: School of Ecosystem and Forest Sciences, The University of Melbourne, Creswick, VIC 3363, Australia.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Weston
authors.affiliation: School of Ecosystem and Forest Sciences, The University of Melbourne, Richmond, VIC 3121, Australia.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Baker
mesh_terms: D000383:Agriculture; D002244:Carbon / Q000737:chemistry; D015203:Reproducibility of Results; D012987:Soil / Q000737:chemistry*; D013055:Spectrophotometry, Infrared
chemical_list: D012987:Soil; D002244:Carbon
keywords: Biodiverse environmental plantings; C sequestration; Mid-infrared spectroscopy; NMR spectroscopy; Near-infrared spectroscopy; Partial least squares regression