Root-microbial population dynamics in a soil profile under the canopy of the desert shrub Zygophyllum dumosum

In the Negev Highlands, Israel, Z. dumosum root area was greater in the lower soil profile (20-30 cm) during the rainy season, except when the soil was drying out after a period of minimal rainfall. Root production was enhanced in the surface layer (0-10 cm) as the soil dried in the wet season, and throughout the soil profile as the soil dried preceding the dry summer period. This suggests 2 functional root types exist for Z. dumosum, one which exploits a relatively stable water supply, and another which captures less available, and reliable sources. Soil bacteria populations were relatively stable throughout the study period, whereas fungi and actinomycetes appeared to have an inverse relationship, with fungi increasing after the early rains, while actinomycetes declined. Actinomycetes may be a more important component of the microflora during drought periods, since their numbers were relatively high following 2 yr of below-normal rainfall, but never recovered after a year of normal rainfall. -from Authors