Relationships between Prosopis flexuosa (Fabaceae) and cattle in the Monte desert: Seeds, seedlings and saplings on cattle-use site classes.

CAMPOS M. CLAUDIA; VALERIA E. CAMPOS; ARNALDO MANGEAUD; CARLOS E. BORGHI; CLAUDIA DE LOS RÍOS; STELLA M. GIANNONI

REVISTA CHILENA DE HISTORIA NATURAL

SOC BIOLGIA CHILE

Año: 2011 vol. 84 p. 289 - 299

0716-078X

The fate of Prosopis flexuosa seeds dispersed by cattle is dependant on the spatial pattern of dung deposition and foraging movements. We hypothesised that cattle-use site classes explain the response variables related to seed input and fate of seeds, seedlings and saplings (small plants more than one year old). We defined sites with heavy cattle traffic (?trails? and ?periphery of trails?), sites used for resting and foraging (?under Prosopis?), and sites where isolated individuals only walk (?under shrubs? and ?bare soil?). Considering the established cattle-use site classes, our specific goals were to quantify and compare: (1) seeds transported in cattle dung; (2) seedlings 10 months after dung deposition; (3) established saplings; and (4) germinated and remaining seeds, and seedling survival in dung immediately after dung deposition. In a grazed field at Ñacuñán (Mendoza, Argentina) we worked in four similar areas, each consisting of 25-ha plots 2 km apart. Space use by cattle caused differential seed input: ?under Prosopis? and in the ?periphery of rails? animals deposited the largest amounts of dung and seeds. Ten months after dung deposition, the highest number of seedlings occurred on ?trails?, ?under Prosopis? and in the ?periphery of trails?. In the long term, the highest number of established saplings occurred only in the periphery of trails?. The number of seeds germinated immediately after fruit production and dung deposition was very low. Survival of seedlings sprouting from dung-germinated seeds did not exceed one week. On ?trails? and in the ?periphery of trails? the persistence of seeds in dung was low because of dung disintegration by the action of cattle trampling. The seeds that did not remain in dung were probably the source of seeds that will germinate in the next wet season (i.e. 10 months after dung deposition). With different effects depending on cattle site activity and on the stage of the P. flexuosa plant (seed, seedling, or sapling), defecation and trampling appear to be important processes in the seed dispersal cycle. In this sense, cattle could benefit the establishment of P. flexuosa.