Facilitation between Higher Plant Species in a Semiarid Environment

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. Ecological Society of America is collaborating with JSTOR to digitize, preserve and extend access to Ecology. Abstract. A major role of facilitation between higher plant species, particularly in stressful environments, has recently been reported in several papers that suggest that beneficial interactions could be more important in the dynamics of plant communities than has been recognized to date. In a semiarid region in southeastern Spain we determined the effect of a leguminous shrub, Retama sphaerocarpa, on its environment, testing the hypothesis that facilitation by the shrub of one species of its understory, Marrubium vulgare, is reciprocal and that the shrub benefits from sheltering herbs beneath its canopy.Marrubium plants under Retama had greater specific leaf area, leaf mass, shoot mass, leaf area, more flowers, a higher nitrogen (N) concentration in leaf tissue, and more N per plant than isolated plants, suggesting a facilitative effect of Retama on Marrubium including increased availability of resources. Biomass of 1-yr-old cladodes, total biomass, total nitrogen content of 3-yr-old branches, and shoot water potential at midday were higher for Retama shrubs with Marrubium beneath them than in shrubs without Marrubium.Retama strongly improved its own environment, facilitated the growth of Marrubium and other species underneath its canopy, and at the same time obtained benefits from sheltering herbs underneath. The interaction between these two species was indirect, associated with differences in soil properties and with improved nutrient availability under shrubs compared with plants growing on their own.We propose that the mutual benefit of the association between Retama and Marrubium is best termed a facultative mutualism. Each partner benefits from greater availability of resources in the "island of fertility" that results from their association. If beneficial plantplant interactions as described here are widespread, positive relationships may have a major role in determining the pattern and structure of plant communities.

Local facilitation, bistability and transitions in arid ecosystems

“…In the extreme conditions of arid areas, amelioration of the micro-environment underneath the canopy of a 'nurse plant' (Niering et al, 1963) significantly improves the conditions for establishment and growth of other plants (e.g., Mc Auliffe, 1988;Pugnaire et al, 1996;Aguiar and Sala, 1999;Holzapfel and Mahall, 1999;Armas and Pugnaire, 2005). Vegetation cover plays the role of physical protection that decreases thermal amplitudes, radiation exposures, wind dessication and soil erosion and prevents soil crust formation (Noy-Meir, 1973;Callaway and Walker, 1997;Greene et al, 2001).…”

Differential responses of shrubs and herbs present at the Upper Minjiang River basin (Tibetan Plateau) to several soil variables

“…Most of these studies have either focused on facilitative and competitive interactions between woody and herbaceous plants (Pugnaire et al, 1996;Pugnaire and Lazaro, 2000;Holzapfel and Mahall, 1999;Maestre et al, 2003), or on feedbacks in the dynamics of plant communities. Such feedbacks include the ability of plant species to improve their environments by enhancing nutrient availability or nutrient capture (Hobbie, 1992;Wilson and Agnew, 1992), and differences between species in soil water use efficiency (Ehleringer et al, 1991;Lin et al, 1996;Schwinning et al, 2005a).…”

Spatial vegetation patterns and imminent desertification in Mediterranean arid ecosystems

“…Local facilitation is the biophysical ameliorative effect of sessile organisms, such as plants, on their neighbouring environment. Such local positive interactions induce vegetation patchiness 6,7,10 and determine the response of this patchiness to environmental change 3 .We investigated how the spatial organization of vegetation is influenced by the degree of external stress by combining modelling and field data from three grazed Mediterranean arid ecosystems in Spain, Greece and Morocco. In each of these ecosystems, we collected data on three sites that differed with respect to the livestock grazing pressure (Table 1; Methods).…”

“…Local facilitation is the biophysical ameliorative effect of sessile organisms, such as plants, on their neighbouring environment. Such local positive interactions induce vegetation patchiness 6,7,10 and determine the response of this patchiness to environmental change 3 .…”