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Stem demography of Prosopis glandulosa var. torreyana in vegetation arcs and associated bare areas
Author(s) -
LópezPortillo J.,
Montaña C.,
Ezcurra E.
Publication year - 1996
Publication title -
journal of vegetation science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 115
eISSN - 1654-1103
pISSN - 1100-9233
DOI - 10.2307/3236465
Subject(s) - prosopis glandulosa , arid , vegetation (pathology) , prosopis , limiting , ecology , plant cover , environmental science , larrea , woody plant , physical geography , hydrology (agriculture) , agronomy , biology , geography , geology , species richness , shrub , medicine , mechanical engineering , geotechnical engineering , pathology , engineering
. Vegetation arcs are characterized by dense patches of up to 100% plant cover surrounded by bare areas where cover is around 5%. These patterns of contracted vegetation have been reported mainly in alluvial fans of arid and semiarid zones (known as bajadas ) with gentle slopes (0.2–2%), summer rainfall, and heavy showers that run as sheet‐flow. It has been suggested that run‐off water from bare areas is stopped at the front of the arcs and, depending on the amount of rainfall, may advance superficially into the arc, reaching the downslope limit less often. These dynamics would imply a gradient of water availability inside the arc, higher at the upper edge. We termed this the moisture gradient hypothesis. We indirectly tested this hypothesis by following the demography of a cohort of stems of the honey mesquite Prosopis glandulosa var. torreyana in three vegetation arcs and their corresponding bare areas during a yearly cycle at the Bolsón de Mapimí in the Chihuahuan Desert. We selectively removed different plant life‐forms (trees, shrubs and herbs) in three positions within the arcs; no manipulation was possible in the bare areas due to low plant cover. The results suggested that removal of other plant life‐forms, mainly grasses, affected growth and survival of mesquite low (but not high) stems, making them accessible to medium‐sized mammal browsers (jackrabbits and packrats). These results suggest that, at least for the honey mesquite, water availability in vegetation arcs was not the most strongly limiting factor for shoot performance and demography, and that browsing damage, a biotic constraint, took precedence over resource limitation.