Ehud Meron

Transverse instabilities of vegetation fronts separating domains of uniform vegetation and bare soil are investigated using a vegetation model that incorporates two robust water–vegetation feedbacks. The first is the uptake–diffusion feedback, involving soil-water diffusion toward root zones where water content is reduced by root uptake. The second is the infiltration feedback, involving overland water flow toward vegetation patches where the infiltration rate exceeds that of bare soil. Using a semi-analytical approach, we extend front stability analysis beyond the singular-perturbation limit previously addressed in simpler models and study the impact of biotic and abiotic factors on the stability range. We find that faster soil-water diffusion can destabilize fronts when the uptake–diffusion feedback dominates, but can stabilize them when the infiltration feedback is dominant. Moreover, we show that transverse front instabilities can result in either modulated fronts propagating at constant speeds or fingering dynamics that evolve into extended patterns. Near the instability threshold, fingering remains confined to slowly advancing fronts, but the range of fingering increases as the strength of both feedbacks grows. These findings offer new insights into the potential for fingering-induced desertification reversal in natural ecosystems and highlight the possible role of plant adaptability failure to drier climates in enhancing this potential.