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A Provenzale

Publications and source records attributed to A Provenzale.

6 recordsLinked to original sources
PubMed2006

A mathematical model of plants as ecosystem engineers.

Understanding the structure and dynamics of plant communities in water-limited systems often calls for the identification of ecosystem engineers--key species that modify the landscape, redistribute resources and facilitate the growth of other species. Shrubs are excellent examples; they self-organize to form patterns of mesic patches which provide habitats for herbaceous species. In this paper we present a mathematical model for studying ecosystem engineering by woody plant species in drylands. The model captures various feedbacks between biomass and water including water uptake by plants' roots and increased water infiltration at vegetation patches. Both the uptake and the infiltration feedbacks act as mechanisms for vegetation pattern formation, but have opposite effects on the water resource; the former depletes the soil-water content under a vegetation patch, whereas the latter acts to increase it. Varying the relative strength of the two feedbacks we find a trade-off between the engineering capacity of a plant species and its resilience to disturbances. We further identify two basic soil-water distributions associated with engineering at the single patch level, hump-shaped and ring-shaped, and discuss the niches they form for herbaceous species. Finally, we study how pattern transitions at the landscape level feedback to the single patch level by affecting engineering strength.

Biomass↗
PubMed2004

Ecosystem engineers: from pattern formation to habitat creation.

Habitat and species richness in drylands are affected by the dynamics of a few key species, termed "ecosystem engineers." These species modulate the landscape and redistribute the water resources so as to allow the introduction of other species. A mathematical model is developed for a pair of ecosystem engineers commonly found in drylands: plants forming vegetation patterns and cyanobacteria forming soil crusts. The model highlights conditions for habitat creation and for high habitat richness, and suggests a novel mechanism for species loss events as a result of environmental changes.

Biophysics↗
PubMed2002

Modelling the survival of bacteria in drylands: the advantage of being dormant.

We introduce a simple mathematical model for the description of 'dormancy', a survival strategy used by some bacterial populations that are intermittently exposed to external stress. We focus on the case of the cyanobacterial crust in drylands, exposed to severe water shortage, and compare the fate of ideal populations that are, respectively, capable or incapable of becoming dormant. The results of the simple model introduced here indicate that under a constant, even though low, supply of water the dormant strategy does not provide any benefit and it can, instead, decrease the chances of survival of the population. The situation is reversed for highly intermittent external stress, due to the presence of prolonged periods of dry conditions intermingled with short periods of intense precipitation. In this case, dormancy allows for the survival of the population during the dry periods. In contrast, bacteria that are incapable of turning into a dormant state cannot overcome the difficult times. The model also rationalizes why dormant bacteria, such as those composing the cyanobacterial crust in the desert, are extremely sensitive to other disturbances, such as trampling cattle.

Bacterial Physiological Phenomena↗
PubMed2000

Mesoscale vortices and the paradox of the plankton.

Coexistence of competitive species is severely limited by the availability of resources and the characteristics of the environment. In particular, the so-called 'competitive exclusion principle' states that, at equilibrium, the number of coexisting species cannot be larger than the number of resources for which they compete. However, many in situ observations have revealed prolonged coexistence of a large number of competitive plankton species, a phenomenon known as 'the paradox of the plankton'. Here we investigate this problem and show that ocean mesoscale vortices generate transport barriers and incomplete horizontal mixing, allowing for a prolonged survival of the less-fit species, even for fully homogeneous resource distributions. In such a situation, the temporarily less-fit plankton species are protected from competition by the action of the vortices.

Animals↗