Aims

Spatial heterogeneity of resources and soil biota distribution in drylands is hypothesized to control perennial patterns of vegetation patchiness. The buildup of labile nutrient pools in soils under annual plants may indirectly facilitate succession by other plants, thus aiding the establishment of vegetation patches in deserts. Nutrient accumulation under annual plants can lead to faster nitrogen (N) cycling and increased resource availability.

Methods

To understand how the establishment of annual plants affects soil nutrient dynamics, we planted patches of a widespread local summer annual plant, unarmed saltwort (Salsola inermis Forssk.) and assessed how these patches influence the soil N cycle and soil N₂O emissions. We hypothesized that annual plant establishment would enhance resource accumulation and accelerate soil N cycle rates in the soil beneath the plant patch.

Results

Our results supported our hypothesis; we measured the highest soil N cycle rates and soil N₂O emissions under the plant patch, while they decreased across the patch-to-bare-soil gradient, suggesting an accelerated N cycle within the planted areas. Water extractable organic carbon (WEOC) and ammonia accumulation in the surface soil beneath the plants was associated with a large burst in soil N₂O emissions within the patch, following dry soil wetting by the first winter rains.

Conclusions

Our results suggest that the establishment of annual summer-flourishing plants affects soil nutrient dynamics and accumulation, thus creating nutrient-rich microsites for potential succession by other annuals and perennials, processes that may lead to fertility island establishment in the Negev Desert ecosystem.