@article{fdi:010055663,
  title = {{A}re {NIR} spectra useful for predicting site indices in sandy soils under {E}ucalyptus stands in {R}epublic of {C}ongo ?},
  author = {{B}ikindou, {F}.{D}.{A}. and {G}omat, {H}.{Y}. and {D}eleporte, {P}. and {B}ouillet, {J}.{P}. and {M}oukini, {R}. and {M}bedi, {Y}. and {N}gouaka, {E}. and {B}runet, {D}idier and {S}ita, {S}. and {D}iazenza, {J}.{B}. and {V}ouidibio, {J}. and {M}areschal, {L}. and {R}anger, {J}. and {S}aint-{A}ndr{\'e}, {L}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he objectives of this study were: (i) to test whether near infrared reflectance spectroscopy ({NIRS}) can be used to assess site fertility in sandy and ferralitic soils of the {C}ongo; (ii) to evaluate the comparative advantages of this methodology with respect to classical regressions with chemical and physical analysis of soils; and (iii) to assess the ability of {NIRS} to predict concentrations of individual nutrients. {S}ixty-two plots were sampled in 20 selected forest stands with varying wood production. {S}ite indices ({H}lim) were estimated from the measured dominant height in the plots. {S}oil samples ({N} = 353) were analysed by {NIRS}, while physical and chemical analyses were carried out on 210 subsamples. {P}artial {L}east {S}quares regression ({PLS}) was used to model the site index from {NIRS}, while {V}ariable {I}mportance in {P}rojection ({VIP}) allowed relating the main explicative frequencies to nutrient availability. {A} validation was performed based on an independent field trial (not used in the calibration set) in which soils were collected and analysed by {NIRS}. {T}he measured dominant height growth was compared with the dominant height growth simulated from the site indices predicted using {NIR} spectra. {M}ultiple regressions between site indices ({H}lim) and soil properties failed to explain the variability in {H}lim ({R}-2 = 0.36). {T}his variability was better predicted by {NIR} spectra, with an {R}-2 = 0.64 and a predicted {R}oot {M}ean {S}quare {E}rror of 7% for the mean value of {H}lim. {B}ased on analysis of {VIP} frequencies, the most important factors determining the site indices were organic matter, phosphorus, {CEC}, clay content, and p{H}. {T}he comparison between measured and simulated dominant height in the validation set gave similar {R}-2 (0.61) than in the calibration set. {T}hese results demonstrate that mapping of site indices could be performed at an affordable cost in this region. {T}he methodology developed here, which links {PLS} and {VIP} to assess the main factors determining soil fertility, is not specific to this study and could be used elsewhere.},
  keywords = {{S}oil fertility ; {I}nfrared spectroscopy ; {S}ite index ; {F}orest productivity ; {CONGO}},
  booktitle = {},
  journal = {{F}orest {E}cology and {M}anagement},
  volume = {266},
  numero = {},
  pages = {126--137},
  ISSN = {0378-1127},
  year = {2012},
  DOI = {10.1016/j.foreco.2011.11.012},
  URL = {https://www.documentation.ird.fr/hor/fdi:010055663},
}