Soil organic carbon in the rocky desert of northern Negev (Israel)

Purpose So far, the soil organic carbon (SOC) literature is dominated by studies in the humid environments with hugestocks of vulnerable carbon. Limited attention has been given to dryland ecosystems despite being often consideredto be highly sensitive to environmental change. Thus, there is insufficient research about the spatial patterns of SOCstocks and the interaction between soil depth, ecohydrology, geomorphic processes, and SOC stocks. This study aimed atidentifying the relationship between surface characteristics, vegetation coverage, SOC, and SOC stocks in the aridnorthern Negev in Israel.Materials and methods The study site Sede Boker is ideally suited because of well-researched but variable ecohydrology.For this purpose, we sampled five slope sections with different ecohydrologic characteristics (e.g., soil and vegetation)and calculate SOC stocks. To identify controlling factors of SOC stocks on rocky desert slopes, we comparedsoil properties, vegetation coverage, SOC concentration, and stocks between the five ecohydrologic units.Results and discussion The results show that in Sede Boker, rocky desert slopes represent a significant SOC pool with amean SOC stock of 0.58 kg C m−2 averaged over the entire study area. The spatial variability of the soil coverage representsa strong control on SOC stocks, which varies between zero in uncovered areas and 1.54 kg C m−2 onaverage in the soil-covered areas. Aspect-driven changes of solar radiation and thus of water availability are thedominant control of vegetation coverage and SOC stock in the study area.Conclusions The data indicate that dryland soils contain a significant amount of SOC. The SOC varies between theecohydrologic units, which reflect (1) aspect-driven differences, (2) microscale topography, (3) soil formation, and (4)vegetation coverage, which are of greatest importance for estimating SOC stocks in drylands.