Foliar phenol concentrations (total and simple phenols) were determined in Aleppo pine (Pinus halepensis Mill.) needles collected in June 2000, from 6 sites affected by various forms of atmospheric pollutants (NO, NO 2 , NO x , O 3 and SO 2 ) monitored during two months. Results show an increase in total phenol content with exposure to sulphur dioxide and a reduction with exposure to nitrogen oxide pollution. p-Coumaric acid, syringic acid and 4-hydroxybenzoic acid concentrations increase with exposure to nitrogen oxide pollution, whereas gallic acid and vanillin decrease in the presence respectively of sulphur dioxide and ozone. This in situ work confirms the major interest of using total and simple phenolic compounds of P. halepensis as biological indicators of air quality.
The aim of the present study is to assess whether certain ecophysiological responses (contents of total phenols, total proanthocyanidins, and total and simple flavonols), in the needles of Aleppo pines (Pinus halepensis Mill.) may be valid bioindicators for the assessment of the air quality. Samples were taken at five natural sites polluted by various pollutants (NO, NO2, other NOx, SO2, and O3). The results show a decrease in total phenol concentrations with levels of nitrogen oxide pollutions (significant negative correlations between the total phenol concentrations and concentrations of NO, NO2, and other NOx). Total flavonoids (total flavonols and proanthocyanidins) are useful bioindicators for ozone pollution (significant negative correlations between total proanthocyanidins and the concentrations of ozone and significant positive correlations between total flavonols and the ozone pollution). Sulfur dioxide pollution is distinguished by low concentrations in quercetin, isorhamnetin, and kaempferol (significant negative correlations between these simple flavonols and the concentrations of SO2). This work confirms the strong interest of using the phenolic compounds of Pinus halepensis as biological indicators of air quality.
(Reçu le 18 janvier 1999 ; accepté le 25 mars 1999)Résumé -Le débroussaillement constitue une perturbation aux effets multiples sur la végétation. Les auteurs étudient les consé-quences sur le sol et sur les nutriments chez le chêne vert et l'arbousier. Au niveau du sol, la perturbation se traduit par une diminution significative du pourcentage de carbone, de la concentration en composés humiques totaux et de la capacité totale d'échange sur calcaire. Sur silice, seuls les composés humiques totaux varient significativement. Les concentrations et la dynamique saisonnière des nutriments sont perturbées différemment chez les deux essences et sur les deux substrats. Chez le chêne vert, seul l'azote diminue significativement sur silice alors que, chez l'arbousier, il y a en plus des variations significatives, sur calcaire, pour le phosphore, le magnésium et le calcium.
Quercus ilex L. / Arbutus unedo L. / débroussaillement / nutrimentsAbstract -Functional reactions of mediterranean sclerophyllous ecosystems to clearing impact. Clearing brings about disturbances with manifold effects on vegetation. The authors analyse the consequences of these disturbances on soil, and on the Quercus ilex and Arbutus unedo nutrients. On calcareous soils, these disturbances cause significant decreases in the carbon ratio, the humic compounds concentration, and the cation exchange capacity. On siliceous soils, only the humic compounds concentration decreases significantly. The nutrients concentrations and seasonal dynamics are disturbed differently according to the species and the substrate. Only a significant decrease of nitrogen is observed in Quercus ilex on siliceous soils, whereas Arbutus unedo shows, in addition, significant variations in phosphorus, magnesium and calcium on calcareous soils.
Quercus ilex L. / Arbutus unedo L. / clearing / nutrients
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