Rodent mounds facilitate shrubs and shrubs inhibit seedlings in the Mojave Desert, USA

The habitat immediately around long-lived desert shrubs often provides a favorable environment ('fertile island') for annual plants and shrub seedling establishment. However, adult shrubs can also compete with shrub seedlings. Part of the fertile island effect is due to rodent burrowing and seed caching but less is known about the effect of rodent mounds on short- and long-term desert shrub demography. We demonstrate that the indirect influences of rodent mounds on soil fertility and permeability create conditions favorable for adult shrubs, enhancing shrub size, density, and local species diversity in a nearly monospecific community of Coleogyne ramosissima in the Mojave Desert, in the southwestern USA. Shrubs facilitate seedling establishment but shrub canopies and fertile islands are not favorable for seedling survival. Occasional success of seedlings growing in open areas on mounds (where seedling densities are lowest) appear to have the biggest effect on long-term shrub demography of the dominant shrub, C ramosissima, and, by inference, on other species of shrubs that are found only on mounds. (C) 2014 Elsevier Ltd. All rights reserved.