Nice little commentary on how to model life at the edge (facilitation on extreme gradients).

Michalet, R., Le Bagousse-Pinguet, Y., Maalouf, J.-P. and Lortie, C. J. 2014. Two alternatives to the stress-gradient hypothesis at the edge of life: the collapse of facilitation and the switch from facilitation to competition. – Journal of Vegetation Science 25: 609-613.