<?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%">Andreetta, Anna</style></author><author><style face="normal" font="default" size="100%">Dignac, Marie-France</style></author><author><style face="normal" font="default" size="100%">Carnicelli, Stefano</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Biological and physico-chemical processes influence cutin and suberin biomarker distribution in two Mediterranean forest soil profiles</style></title><secondary-title><style face="normal" font="default" size="100%">Biogeochemistry</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">Cutins</style></keyword><keyword><style  face="normal" font="default" size="100%">Forest soils</style></keyword><keyword><style  face="normal" font="default" size="100%">Mediterranean</style></keyword><keyword><style  face="normal" font="default" size="100%">Soil organic matter</style></keyword><keyword><style  face="normal" font="default" size="100%">Suberins</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2011</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2011///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.springerlink.com/index/10.1007/s10533-011-9693-9</style></url></web-urls></urls><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Recent investigations have shown macromolecules, such as cutins, and suberins as effective markers for above and belowground plant tissues. These biopolyesters contain structural units speciﬁc for different litter components and for root biomass. The aim of this work was to understand the fate of plant organic matter (OM) in Mediterranean forest soils by evaluating the incorporation of cutin and suberin by measuring speciﬁc biomarkers. Soil and plant tissue (leaves, woods and roots) samples were collected in two mixed Mediterranean forests of Quercus ilex (holm oak) in costal stands in Tuscany (central Italy), which have different ecological and edaphic features. Ester-bound lipids of mineral and organic horizons and the overlying vegetation were analysed using the saponiﬁcation method in order to depolymerise cutins and suberins and release their speciﬁc structural units. Cutin and suberin speciﬁc aliphatic monomers were identiﬁed and quantiﬁed by gas chromatographic techniques. The distribution of cutin and suberin speciﬁc monomers in plant tissue suggested that mid-chain hydroxy acids can be used as leaf-speciﬁc markers and a,x-alkanedioic acids and xC18:1 as root-speciﬁc markers. Differences in the distributions of biomarkers speciﬁc for above and belowground plant-derived OM was observed in the two types of soils, suggesting contrasted degradation, stabilisation and transport mechanisms that may be related to soil physico-chemical properties. The acidic and dry soil appeared to inhibit microbial activity, favouring stabilization of leaf-derived compounds, while, in the more fertile soil, protection within aggregates appeared to better preserve root-derived compounds.</style></abstract></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%">González-Vila, F L</style></author><author><style face="normal" font="default" size="100%">Almendros, G</style></author><author><style face="normal" font="default" size="100%">Martin, F</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">An evaluation of the differences in the composition of humic acids in soils under oak and pine forest by GC-MS after mild degradation</style></title><secondary-title><style face="normal" font="default" size="100%">Plant and soil</style></secondary-title></titles><keywords><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%">Lipids</style></keyword><keyword><style  face="normal" font="default" size="100%">mild degradation</style></keyword><keyword><style  face="normal" font="default" size="100%">Pinus</style></keyword><keyword><style  face="normal" font="default" size="100%">Quercus</style></keyword><keyword><style  face="normal" font="default" size="100%">resin acids</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1987</style></year></dates><volume><style face="normal" font="default" size="100%">103</style></volume><pages><style face="normal" font="default" size="100%">83-88</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Significant differences were found in the products released after eight samples of humic acids (HA's) isolated from soils under mediterranean pine and oak forests underwent mild degradation. A number of compounds, including typical degradation products of lignins, were found exclusively in the HA's from the soils under pine forests. The aliphatic constituents were more firmly retained in the HA's under oak, which presented mean values for aromatic acids lower than the humic samples from pine forests. Different types of diterpene resin acids were also found amongst the mild degradation products of HA's from the studied areas.</style></abstract></record></records></xml>