No abstract

All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. B lack carbon produced by incomplete combustion of fossil fuels and biomass, is a ubiquitous form of ROM widely distributed in the environment. There is no a unique structure accepted for this complex material. Heidenreich et al. (1968) reported for the fi rst time the "onion-like" concentric microtexture of "carbon black." In general, it is accepted that black carbon consists of complex polyaromatic condensed structures

Natural soil water repellency is a property that has already been observed in forest soils and is characterized by its patchydistribution. Ihere are many factors involved in its development. In this work, we have studied a large numberof chemical and biological factors underthe influence of differentplantspecies (Pinus halepensis, Quercus rotundifolia, Cistus albidus and Rosmarinus officinalis) to leam which has the greatest responsibility for its presence and persistence in the top-soillayer. We obselVed strong and significant correlations between ergosterol, giomalin related soil protein (GRSP), extractable lipids, soil organic matter (SOM) content and water repellency (WR). Our results suggested lipid fraction as the principal factor. Moreover, apart from Pinus, fungal biomass seems to be also related to the SOM content. Soil WR found under Pinus appears to be the most influenced by fungi. Quality of SOM, to be precise, lipid fraction could be responsible for WR and its relationship with fungal activity.

No abstract

The variable effect of different types of forest fires on the quantity and quality of soil organic matter (SOM) was analysed by comparing burnt and unburnt soils from six forest ecosystems in central Spain by organic elemental analysis and solid-state 13 C nuclear magnetic resonance (NMR) spectroscopy. Whole soil samples were collected 1 to 2 years after the fires and included one site affected by two fires within 2 years. The fire-affected soils showed no common pattern with respect to the amount of additional carbon (C add ) but at all sites, the fire enhanced the aromatic-C content. The weakest fire intensity resulted in the greatest aromatic-C enrichment factor, EF I(aromatic C) indicating the greatest local accumulation of char. The respective C add disclosed an EF I(aromatic C) to EF I(alkyl C) ratio, B char , of c.1, which supports a small degree of charring. Extensive combustion and volatilization at stronger fire intensities yielded a decrease of EF I(aromatic C) and an increase in B char . These trends are in good agreement with fire intensity and forest fuel combustibility in the various sites and therefore these indices could be used to elucidate the quality and quantity of char input that occurs during and after forest fires. No 13 C NMR evidence for substantial inputs from non-charred plant necromass was found for any of the single-burn soils. The large carboxyl-C content of C add is evidence of the occurrence of oxidation reactions very shortly after the fire. In comparing the single and double-burn sites, no additional char input was observed for the double-burn site, possibly because of complete combustion of young shrubs and char remains during the second fire. The large O-alkyl-C portion found in C add of the double-burn soil is best explained by decreased litter degradation.