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Demographic variability in tiller populations of two perennial pampa grasses
Author(s) -
Laterra Pedro,
Deregibus V. Alejandro,
Maceira Néstor O.
Publication year - 1997
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 - 10.2307/3237326
Subject(s) - tiller (botany) , perennial plant , biology , population , growing season , agronomy , ecology , demography , sociology
. The general objectives of this study were: (1) to investigate the importance of internal influences in regulating the tiller dynamics in natural populations of the warm‐season perennial grasses Paspalum dilatatum and Sporobolus indicus , coexisting in Argentine flooded pampa, in as much as they act independently of the underlying external environment, and (2) to evaluate the extent to which interactions between internal and external factors affect the variation in tiller dynamics within such populations. Within‐population variation in seasonal development of plants and tillers with different neighbour composition was studied for an annual growth cycle. Tiller survival and tillering were significantly influenced by tiller size. Tiller age influenced tiller fate, as suggested by the additive effects of age and size of tillers. These relationships varied with season and with species. Size and age of tillers showed additive effects with their neighbouring species on the tiller fate of P. dilatatum , but the effects of age and size of S. indicus changed according their neighbourhood. Tiller survival of S. indicus during the early growth season was more size‐dependent when the cold‐season species Poa lanigera , was the principal neighbour. Flowering and tillering probabilities were positively related through their common positive responses to tiller size. Tiller survival and recruitment between different seasons were strongly related. Independently of neighbour composition, tiller survival was generally inversely related to tiller recruitment in previous seasons. Therefore, significant density‐dependent mortality of tillers was found for both species during the early summer when tiller density was expressed by basal area units.