<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Duarte, Regina M. B. O.</style></author><author><style face="normal" font="default" size="100%">Fernández-Getino, Ana P.</style></author><author><style face="normal" font="default" size="100%">Duarte, Armando C.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Humic acids as proxies for assessing different Mediterranean forest soils signatures using solid-state CPMAS 13C NMR spectroscopy</style></title><secondary-title><style face="normal" font="default" size="100%">Chemosphere</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">CPMAS 13C NMR spectroscopy</style></keyword><keyword><style  face="normal" font="default" size="100%">Forest soils</style></keyword><keyword><style  face="normal" font="default" size="100%">humic acids</style></keyword><keyword><style  face="normal" font="default" size="100%">Soils signature</style></keyword><keyword><style  face="normal" font="default" size="100%">Structural characterization</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2013</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2013///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science/article/pii/S0045653512015445http://www.ncbi.nlm.nih.gov/pubmed/23332874</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">91</style></volume><pages><style face="normal" font="default" size="100%">1556 - 1565</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Humic acids (HAs) of four representative forest soils profiles from Central Spain (two with different vegetation – pine and oak – but same parent material – granitie, and two with same vegetation – holm oak – but different parent material – granite and limestone) were investigated by solid-state cross polarization with magic angle spinning 13C nuclear magnetic resonance (NMR) spectroscopy. The objectives included the investigation of the impact of different forest properties on HA composition, assessing how the structural characteristics of the HA vary with soil depth, and evaluating the role of HA as surrogates for mapping the different forest soils signatures using structural data derived from 13C NMR spectroscopy. On average, alkyl C is the dominant C constituent (38–48% of the total NMR peak area) in all HA samples, followed by aromatic (12–22%) and O-alkyl C (12–19%), and finally carboxyl C (7.0–10%). The NMR data also indicated that HA composition is likely to be differently affected by the soil physico-chemical properties and type of forest vegetation. The structural characteristics of the HA from soil under oak did not differ broadly downward in the profile, whereas soil HA under pine forest exhibits a somewhat higher recalcitrant nature as a consequence of a higher degree of decomposition. The soil HA from holm oak forests differed from the other two forest soils, exhibiting a progressive decomposition of the alkyl C structures with increasing depth, while the carbohydrate-like indicator (O-alkyl C) is apparently being protected from mineralization in the horizons below the ground level. Overall, these differences in soil HA NMR signatures are an important diagnostic tool for understanding the role of different soil environmental factors on the structural composition of HA from Mediterranean forest soils.</style></abstract><issue><style face="normal" font="default" size="100%">11</style></issue><notes><style face="normal" font="default" size="100%">The following values have no corresponding Zotero field:&lt;br/&gt;publisher: Elsevier Ltd&lt;br/&gt;accession-num: 23332874</style></notes></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Aranda, V.</style></author><author><style face="normal" font="default" size="100%">Oyonarte, C.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Characteristics of organic matter in soil surface horizons derived from calcareous and metamorphic rocks and different vegetation types from the Mediterranean high-mountains in SE Spain</style></title><secondary-title><style face="normal" font="default" size="100%">European Journal of Soil Biology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">humic acids</style></keyword><keyword><style  face="normal" font="default" size="100%">Mediterranean environments</style></keyword><keyword><style  face="normal" font="default" size="100%">pine trees reforestations</style></keyword><keyword><style  face="normal" font="default" size="100%">soil organic matter quality</style></keyword><keyword><style  face="normal" font="default" size="100%">surface horizon</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2006</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2006///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://linkinghub.elsevier.com/retrieve/pii/S1164556306000185</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">42</style></volume><pages><style face="normal" font="default" size="100%">247 - 258</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A study was carried out on some basic characteristics of the organic matter in the surface horizons of soils from the two different geological (calcareous and acid metamorphic rocks) and ecological systems under a Mediterranean climate in Southeast Spain. The results show some noticeable differences in soil organic matter composition. This is likely due to typical Mediterranean climate and well adapted vegetation. There is a tendency towards a greater stability for the soil humus formed under slightly alkaline soil in comparison to the slightly acidic environment. The samples taken from the latter environment have a higher content in free organic matter, a lower content in total extractable humin and a greater relative proportion of aliphatic chains and lignin in the humic acids. The results also suggest some differences caused by the type of vegetation (forest and scrubland ecosystems) in the soil humus chemistry, with a more obvious negative effect under reforestations with species of Pinus in an acidic soil environment (a higher content in free organic matter, lesser presence of fungal-derived perylenequinonic pigments in the humic acids, and a higher content in little evolved forms of nitrogen and lignin in the humic acids). In general the organic matter under scrubland and Quercus vegetation is more decomposed and the humus is more evolved than under Pinus vegetation.</style></abstract><issue><style face="normal" font="default" size="100%">4</style></issue></record></records></xml>