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In order to evaluate the state of groundwater salination by seawater intrusion on the Lebanese coast, the region of Choueifat-Rmeyle, situated in the south of Mount-Lebanon, was chosen as a study zone. Overall, six wells were chosen and water sampling was done for three years starting from 1999 till 2002. Sampling was done on a monthly basis for ten months per year, from July till April. A complete physico-chemical analysis was done for all the water samples taken. Seawater intrusion in the Choueifat-Rmeyle region was studied through the interrelations between the chemical and physical constituents of groundwater. Results showed that the regions of Choueifat, Jiye and Rmeyle were subject to seawater intrusion. This intrusion was directly and simultaneously related to the pumping period and intensity but weakly linked to the quantity of rainfall. It was also related to the geologic nature of the study area. Furthermore, the actual intrusion in the study zone increases the already existing salinity problems. The salinity rates of wells water oscillated between 0.7 dS/m and 5.5 dS/m with the majority above 2 dS/m. This is leading to intolerable levels of water and soil salinity, inadequate for the cultivation of many crops, thus threatening their growth and production and reducing the agrodiversity in the region.

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Abstract. The Near East North Africa (NENA) region spans over 14 % of the total surface of the Earth and hosts 10 % of its population. Soils of the NENA region are mostly highly vulnerable to degradation, and future food security will much depend on sustainable agricultural measures. Weather variability, drought and depleting vegetation are dominant causes of the decline in soil organic carbon (SOC). In this work the status of SOC was studied, using a land capability model and soil mapping. The land capability model showed that most NENA countries and territories (17 out of 20) suffer from low productive lands (> 80 %). Stocks of SOC were mapped (1:5 000 000) in topsoils (0–0.30 m) and subsoils (0.30–1 m). The maps showed that 69 % of soil resources are shown to have a stock of SOC below the threshold of 30 tons ha−1. The stocks varied between ≈10 tons ha−1 in shrublands and 60 tons ha−1 for evergreen forests. Highest stocks were found in forests, irrigated crops, mixed orchards and saline flooded vegetation. The stocks of soil inorganic carbon (SIC) were higher than those of SOC. In subsoils, the SIC ranged between 25 and 450 tons ha−1, against 20 to 45 tons ha−1 for SOC. Results highlight the contribution of the NENA region to global SOC stock in the topsoil (4.1 %). The paper also discusses agricultural practices that are favorable to carbon sequestration such as organic amendment, no till or minimum tillage, crop rotation and mulching and the constraints caused by geomorphological and climatic conditions. The effects of crop rotations on SOC are related to the amounts of above and belowground biomass produced and retained in the system. Some knowledge gaps exist, especially in aspects related to the impact of climate change and effect of irrigation on SOC, and on SIC at the level of the soil profile and soil landscape. Still, major constraints facing soil carbon sequestration are policy-relevant and socioeconomic in nature, rather than scientific.

As a result of rural exodus, terraced orchards are the first abandoned lands in Mediterranean Lebanon. The aim of the present study was to develop knowledge of the status of soil organic carbon (SOC) in abandoned olive orchards. Thirty pairs of abandoned–actively managed fields were sampled at two soil depths (0–0.1 and 0.1–0.3 m) and two positions (crown area and between trees). Mean SOC ranged between 20.9 and 29.1 g kg–1 soil, with the smallest values between trees in the 0.1–0.3 m depth. Abandoned plots showed a surface build up of SOC (SOC0–0.1 m > SOC0.1–0.3 m) and a significantly higher SOC0–0.1 m content than the control. As a result of abandonment, 80% of plots showed increased C stocks (+18.6 Mg C ha–1). Recently abandoned plots (6–12 years) had a C0–0.1 m stock of 6.2 Mg C ha–1, compared with 9.5 Mg C ha–1 for those abandoned for over two decades. Two chronosequences showed that when the initial C was high, one decade was sufficient to reach stock stability. The relative C stock increase reached 38% after two decades of abandonment. Particle size separation showed that 30% of C0–0.1 m in the abandoned fields occurred as particulate organic matter (>50 μm) compared with 20% in the actively managed plots.