Grazing and the phenology of flowering and fruiting in a montane grassland in Argentina: a niche approach.

DÍAZ, S; ACOSTA, A.; CABIDO ,M.

JOURNAL OF VEGETATION SCIENCE

WILEY-BLACKWELL PUBLISHING, INC

Año: 1994 vol. 70 p. 287 - 295

1100-9233

- We comparedf loweringa nd fruitingp atternso f plantss howingd ifferentp ollination modes,t o assess whetherc onsistentd ifferencese mergedb etweeng razeda ndu ngrazed herbaceoucs ommunitiesW. e also analysedt he relationshipas mongt heirp henologies, pollination modes and growth forms. We analysed a site protected from large herbivores for 12 years and a grazed site. In both of them we recorded flowering and fruitinge ventsf or the 20 mostf requents peciesi n differentc limaticp eriodsd uringo ne year.W e calculatedt heirn icheb readthn, iche overlapa ndt he dispersiono f maximum peaks of flowering and fruiting. Grazing was not associated with significant changes in species composition or with invasion by exotics. All the recorded species were native and most of them were presenti n grazeda nd ungrazeds ites, albeit with differentr elativef requencies.T he pollinations pectrumw as dominatedb y wind-pollinateda nd unspecializedi nsectpollinateds pecies,w itho nly two speciesp ollinatedb y hoveringm oths.B othf lowering andf ruitingw ereh ighlyc oncentrateidn a shortp eriodd uringt he summerI. nterruption of grazingd id not promotes ignificantc hangesi n nicheb readtho r overlap.F lowering and fruitingp eak dispersionsw ithinp ollinationg uilds were indistinguishablfer om a randomd istributionT. herew as no evidencet o suggestt he existenceo f a systematic ecologicalf orce leadingt o divergencei n phenologiesw ithinp ollinationg uilds.G razing influence on times of flowering and fruitingw as inconsequentialT. here were groups of species whose members had similar growth forms, floral syndromes, and temporalp atternso f floweringa nd fruiting,a nd thus were highly overlappinga long those threen iche axes. Climaticc onstraintlse adingt o ecologicalc onvergences eemed to be sufficientlys trongt o preventt he expressiono f segregatedp atternsw ithing uilds of the most frequent species.