Dust career impacts on Pinus halepensis growth

Aleppo pine (Pinus halepensis Mill.) is a widely distributed species all around the Mediterranean Basin. It extends from Morocco in the west to Palestine and Jordan in the east, and from France in the north to Tunisia and Algeria in the south (Couhert et al., 1993; Vila, 2008). It prefers regions with a high mean annual temperature and is adapted to prolonged summer droughts (Quezel, 1986). Given its plastic behavior towards climate and soil, the Aleppo pine is the most common tree species in Tunisia with a total area of 296 571 28 ha, representing over 35% of forest land in the country (DGF, 1995). The Kroumirie zone (the North West forest in Tunisia) is characterized by decreasing aridity of the climate from East-SouthEast to West-North-West. However, the Aleppo pine constitutes an excellence forest essence in this type of ecosystem. 

Despite the conservation and protection efforts of this species, mainly used essentially for reforestation, we observe for several years a continual degradation of this essence. Among the degrading factors, the installation of careers near pine forests, accentuates the decrease of growth and the low natural regeneration of the species. 

Human activities such as mining, industry, agriculture, waste treatment, and transportation release substantial amounts of trace elements into the environment (Nriagu and Pacyna, 1988; Nriagu, 1990a). Increasing anthropogenic influences on the environment, especially dust careers, have caused negative changes in natural ecosystems; decreased biodiversity, simplified structure, and lowered productivity (Shparyk Y.S., and Parpan V.I., 2004). These degradation processes can be seen especially in forest ecosystems. Deterioration of forest health has been a major concern of the word community for the past 20-30 years (Royal Ministry for Foreign Affairs, 1971; UN/ECE, 1979; Smith, 1981). Dust carriers affect organisms within forest ecosystems, and inhibit decomposition of organic matter on forest floors, which disrupts nutrient cycles (Cotrufo et al., 1995). Anthropogenic elements deposited to forest soils accumulate in the surface layers of the soil ( Corwin et al., 1999; Hou et al., 2005a; Ruan et al., 2008)., and are usually immobilized there for a long time (e.g. Friedland and Johnson, 1985; Hawkins et al., 1995).

 In particular, smelting, incineration, and transportation release pollutants into the atmosphere. Transportation emits trace elements from fuel combustion (Huang et al., 1994; Wang et al., 2003). Thus, the air around career is rich in trace elements (Mizohata et al., 2000). The fine particulate matter like An, As, Sb and Pb is suspende in air for several weeks and is often transported over large distances. The particulate matter is eventually deposited to soil either directly or via deposition onto vegetation (Takamatsu et al., 2000; Sakata et al., 2006). Therefore, pollution of soil and water by trace elements progresses gradually, even in montane forests far from urban areas. 

Although there are no rules or guidelines on montane soil pollution in Tunisia especially in Kroumirie. It is important to analyze current levels of anthropogenic elements in montane forest and to determine potential effects of this pollution. However, such studies have rarely been carried out in Kroumirie and the large-scale impact of dust careers in forest ecosystems is not so evident. The aim of the studies presented here was to identify the impact of dust career emissions on the Aleppo pine forest. Two populations were targeted, the first is located in front of a career and the second has served as a control population.