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 huge stocks of vulnerable carbon. Limited attention has been given to dryland ecosystems despite being often considered to be highly sensitive to environmental change. Thus, there is insufficient research about the spatial patterns of SOC stocks and the interaction between soil depth, ecohydrology, geomorphic processes, and SOC stocks. This study aimed at identifying the relationship between surface characteristics, vegetation coverage, SOC, and SOC stocks in the arid northern 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 compared soil 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 a mean SOC stock of 0.58?kg?C?m^?2 averaged over the entire study area. The spatial variability of the soil coverage represents a strong control on SOC stocks, which varies between zero in uncovered areas and 1.54?kg?C?m^?2 on average in the soil-covered areas. Aspect-driven changes of solar radiation and thus of water availability are the dominant 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 the ecohydrologic 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.