<?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%">Rovira, P.</style></author><author><style face="normal" font="default" size="100%">Vallejo, V. R.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Organic carbon and nitrogen mineralization under Mediterranean climatic conditions: the effects of incubation depth</style></title><secondary-title><style face="normal" font="default" size="100%">Soil Biology and Biochemistry</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">mineralization</style></keyword><keyword><style  face="normal" font="default" size="100%">organic matter (voyant)</style></keyword><keyword><style  face="normal" font="default" size="100%">Soil depth</style></keyword><keyword><style  face="normal" font="default" size="100%">water content</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1997</style></year><pub-dates><date><style  face="normal" font="default" size="100%">1997///</style></date></pub-dates></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science/article/pii/S0038071797000527</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">29</style></volume><pages><style face="normal" font="default" size="100%">1509 - 1520</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">n a soil profile, temperature and humidity regimes change with depth. Under Mediterra- nean conditions, upper horizons are more affected by water deficits and drying-rewetting cycles than deep horizons. Our aim was to study how carbon and nitrogen mineralization are affected by depth, and special attention is paid to separating the effects of pedoclimate from the effects of other con- straints like amount and quality of organic matter. To this end, mixtures of plant + soil material were exposed by incorporation in the field, at depths of 5, 20 and 40 cm, in nylon mesh bags. Mineralization of C and N was studied for 2 y. For all types of plant material studied (Eucalyptus globulus, Quercus ibex and Pinus halepensis), mineralization of both carbon and nitrogen was lower at 5cm. No differ- ences were between 20 and 40 cm. This result, probably as a result of the higher drying of the upper- most horizons, contrasts with the usual findings on this topic. The amounts of both C and N mineralized were lower than expected, probably because plant materials were finely ground, allowing stabilization in the mineral matrix of soil. With the possible exception of Pinus, depth affected the rate of mineralization, not the relation between C and N. It is concluded that, at least under Mediterranean conditions, the pedoclimate in deep layers is more favourable to microbial activity than in upper layers, in which drought is a strong limiting factor. Reduced oxygen availability in the subsoil layers did not inhibit decomposition and mineralization to the same extent as did desiccation in the surface layer. The higher mineralization of C and N usually found in upper horizons may be attributed to the higher amount and quality of organic matter in these horizons, rather than to pedoclimatic constraints</style></abstract><issue><style face="normal" font="default" size="100%">9110</style></issue></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%">Rovira, P</style></author><author><style face="normal" font="default" size="100%">Vallejo, V R</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Organic carbon and nitrogen mineralization under Mediterranean climatic conditions: the effects of incubation depth</style></title><secondary-title><style face="normal" font="default" size="100%">Soil Biology and Biochemistry</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">mineralization</style></keyword><keyword><style  face="normal" font="default" size="100%">organic matter (voyant)</style></keyword><keyword><style  face="normal" font="default" size="100%">Soil depth</style></keyword><keyword><style  face="normal" font="default" size="100%">water content</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1997</style></year></dates><volume><style face="normal" font="default" size="100%">29</style></volume><pages><style face="normal" font="default" size="100%">1509-1520</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">n a soil profile, temperature and humidity regimes change with depth. Under Mediterra- nean conditions, upper horizons are more affected by water deficits and drying-rewetting cycles than deep horizons. Our aim was to study how carbon and nitrogen mineralization are affected by depth, and special attention is paid to separating the effects of pedoclimate from the effects of other con- straints like amount and quality of organic matter. To this end, mixtures of plant + soil material were exposed by incorporation in the field, at depths of 5, 20 and 40 cm, in nylon mesh bags. Mineralization of C and N was studied for 2 y. For all types of plant material studied (Eucalyptus globulus, Quercus ibex and Pinus halepensis), mineralization of both carbon and nitrogen was lower at 5cm. No differ- ences were between 20 and 40 cm. This result, probably as a result of the higher drying of the upper- most horizons, contrasts with the usual findings on this topic. The amounts of both C and N mineralized were lower than expected, probably because plant materials were finely ground, allowing stabilization in the mineral matrix of soil. With the possible exception of Pinus, depth affected the rate of mineralization, not the relation between C and N. It is concluded that, at least under Mediterranean conditions, the pedoclimate in deep layers is more favourable to microbial activity than in upper layers, in which drought is a strong limiting factor. Reduced oxygen availability in the subsoil layers did not inhibit decomposition and mineralization to the same extent as did desiccation in the surface layer. The higher mineralization of C and N usually found in upper horizons may be attributed to the higher amount and quality of organic matter in these horizons, rather than to pedoclimatic constraints</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%">Avila, Anna</style></author><author><style face="normal" font="default" size="100%">Bonilla, David</style></author><author><style face="normal" font="default" size="100%">Rodà, F</style></author><author><style face="normal" font="default" size="100%">Piñol, J</style></author><author><style face="normal" font="default" size="100%">Neal, C</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Soilwater chemistry in a holm oak ( Quercus ilex) forest: inferences on biogeochemical processes for a montane-Mediterranean area</style></title><secondary-title><style face="normal" font="default" size="100%">Journal of Hydrology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">biogeochemistry</style></keyword><keyword><style  face="normal" font="default" size="100%">chemical composition</style></keyword><keyword><style  face="normal" font="default" size="100%">forest soils (citation)</style></keyword><keyword><style  face="normal" font="default" size="100%">Ions</style></keyword><keyword><style  face="normal" font="default" size="100%">Soil depth</style></keyword><keyword><style  face="normal" font="default" size="100%">soil pH</style></keyword><keyword><style  face="normal" font="default" size="100%">soil water</style></keyword><keyword><style  face="normal" font="default" size="100%">temporal variation</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year></dates><volume><style face="normal" font="default" size="100%">166</style></volume><pages><style face="normal" font="default" size="100%">15-35</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Soil solution and free-flowing soilwater were sampled at various depths for 3 years in a plot of holm oak (Quercus ilex L.) in the Montseny mountains (NE Spain). The soil solution retained at -65M kPa in the mineral soil at depths of 20 and 40 cm had a different chemistry from that of throughflow under the humic layer (H-layer throughflow) and, to a lesser extent, from deep subsurface flow. The dominant mobile anion in the soil solution and the deep flow was SO:-, whereas in the H-layer, SOi- was overridden by alkalinity. H-Layer throughflow chemistry was extremely variable, in consequence of the large number of biogeochemical processes affecting it (e.g. rainfall chemistry, dry deposition, leaching from canopy and litter, decomposition), and of the quantity of water available for transport of solutes. The chemistry of the soil solution was more predictable, as it was governed mainly by nutrient uptake, cation exchange reactions and the seasonal wetting and drying cycles. The chemistry of the deep subsurface flow was often intermediate between that of the soil solution and that of the H-layer throughflow; this suggested a mixture of displaced pre-event soil solution and of H-layer throughflow circulating through preferential flow paths. With humid antecedent conditions, the chemistry of the deep subsurface flow approached that of the soil solution. The cation concentration relationships in the soil solution were strongly linear. In a homogeneous soil, cation exchange theory predicts this to be expected only for cations of the same charge, whereas cations of different charges should follow power relationships. Our results, however, are consistent with a theoretical approach involving cation exchange reactions in a highly heterogeneous environment. Indeed, our study illustrates the heterogeneous nature of the soils, as the power relationship has been obscured completely. Soilwater chemistries were markedly different from those of streamwater, particularly under dry conditions. During baseflow, the stream is fed by groundwater, and the soils are probably disconnected from the stream. During humid periods, the chemistry of the streamwater tends toward that of the deep subsurface flow. Chemical hydrograph separation indicates that, on average, stormflow water comprises an approximately one to one mixture of groundwater and deep subsurface flow.</style></abstract></record></records></xml>