Chemical and biological characterization of dissolved organic matter from silver fir and beech forest soils D. Pizzeghello a , A. Zanella b , P. Carletti c , S. Nardi a, * a Dipartimento di Biotecnologie Agrarie, Universita ` di Padova, Agripolis, Viale dell’Universita ` 16, 35020 Legnaro, Padova, Italy b Dipartimento Territorio e Sistemi Agro-Forestali, Universita ` di Padova, Agripolis, Viale dell’Universita ` 16, 35020 Legnaro, Padova, Italy c Centro di Ecologia Alpina, 38040 Viote del Monte Bondone, Trento, Italy Received 17 October 2005; received in revised form 28 February 2006; accepted 1 March 2006 Available online 18 April 2006 Abstract Despite a growing attention to the dissolved organic matter (DOM) in terrestrial ecosystems and evidence of the fact that vegetation affects the quality of both undissolved and dissolved organic matter in soil, the role of DOM as a biological indicator is still poorly under- stood. In this work, the fertility of 59 sites, divided into eight key alliances of the order Fagetalia sylvaticae Pawl., was studied considering chemical and biological parameters such as soil DOM, hormone-like activity, low-molecular-weight (LMW) aliphatic and phenolic acids, and floristic data. Both non-parametric tests and principal component analysis (PCA) revealed differences between silver fir and beech forests and within each type of forest. There were also differences between neutrophilous and acidophilous types. What’s more, PCA reveals the dominance of the auxin (IAA)-like activity, and of some phenolic acids in distinguishing the acidophilous beeches (ACI) form the other types, whereas the gibberellin (GA)-like activity is more relevant in neutrophilous conditions such as thermophilous (THE) and mesophilous (MESO) beeches and montane (MO), high montane (HMA), high montane (HMC) silver fir forests. The GA-like activity is also related to the succinic, fumaric, malonic, and L-malic acids in the MO, HMA and HMC silver fir forests. Moreover, the role of LMW aliphatic acids in mobilizing the hormone-like activity, which improves forest growth, is stressed. The growth of seedlings of Picea abies was influenced by the phenolic acid content. At concentrations between 1 and 100 lM, phen- ylacetic and protocatechuic acids inhibited root growth to the same extent as indoleacetic acid, while p-hydroxybenzoic acid had a stim- ulating effect comparable to that of gibberellic acid. The aliphatic and phenolic acids appear to be related to plant strategies that influence soil fertility affecting plant growth through rhizodeposition. The role of LMW aliphatic and phenolic acids as molecular markers of ecosystem function is noted. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Silver fir; Beech; Low-molecular-weight aliphatic and phenolic acids; Hormone-like activity; Bioassay on Norway spruce seedlings 1. Introduction Dissolved organic matter (DOM) is probably the most bio- available fraction of soil organic matter (Marschner and Kalbitz, 2003), which contributes significantly to nutrient cycles (Qualls, 2000) and is important in the following contexts: 1. it is a major mode of nitrogen and phosphorus export in many ecosystems; 0045-6535/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2006.03.001 Abbreviations: DOM, dissolved organic matter; LMW, low-molecular- weight; MO, montane; HMA, high montane with Adenostylo; HMC, high montane caricetosum; AC, acidophilous with Pyrola; A, acidophilous with Carici; THE, thermophilous; MESO, mesophilous; ACI, acidophilous beech forests; IAA, auxin-like activity; GA, gibberellin-like activity; oxa, oxalic acid; tar, tartaric acid; L-mal, L-malic acid; mal, malonic acid; suc, succinic acid; fum, fumaric acid; total AA, total aliphatic acids; proto, protocatechuic acid; proto al, protocatechuic aldehyde; p-hydro, p-hydr- oxybenzoic acid; van, vanillic acid; val, vanilline; phen, phenylacetic acid; ben, benzoic acid; total PA, total phenolic acids. * Corresponding author. Tel.: +39 049 8272911; fax: +39 049 8272929. E-mail address: serenella.nardi@unipd.it (S. Nardi). www.elsevier.com/locate/chemosphere Chemosphere 65 (2006) 190–200