Fire-mediated interactions between shrubs in a South American temperate savannah

• Published in: Oikos Vol. 118; no. 9; pp. 1383 - 1395
• Main Authors: Biganzoli, Fernando, Wiegand, Thorsten, Batista, William B.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.09.2009; Blackwell Publishing Ltd; Blackwell Publishing; Blackwell
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Baccharis; Biological and medical sciences; Community ecology; Eupatorium; Forest & brush fires; Forest and land fires; Fundamental and applied biological sciences. Psychology; General aspects; Grasslands; Modeling; Mortality; National parks; Phytopathology. Animal pests. Plant and forest protection; Plant populations; Plants; Poisson process; Savannas; Seedlings; Shrubs; Terrestrial ecosystems; Topographical elevation; Vegetation; Weather damages. Fires; South America; America; Savannah; Interaction; Mortality; Plot; Shrub; Spatial variation; Recruitment; Hypothesis test; Spatial distribution; Fires; Dominant species; Pattern analysis; Ecological abundance; Anthropogenic factor
• ISSN: 0030-1299; 1600-0706
• DOI: 10.1111/j.1600-0706.2009.17349.x

We examined spatial patterns of fire-caused mortality and after-fire establishment of two dominant shrub species, Baccharis dracunculifolia and Eupatorium buniifolium in a humid temperate South American savannah. Our objective was to determine whether fires mediate in interactions between these two species. After a natural fire burned a large tract of savannah, we established two plots (respectively 550 and 500 m²) within which we mapped all surviving and dead shrubs as well as all individuals of shrub species that recruited in the following year. We used techniques of point-pattern analysis to test specific null hypotheses about spatial associations in the distribution, mortality, and establishment of shrubs. Results support the notions that fire mediates interactions between these two species. Fire-caused death of E. buniifolium tended to occur selectively in the vicinities of Baccharis individuals, and recruitment of B. dracunculifolia tended to be concentrated in the places of dead shrubs. These responses, however, were contingent on local abundances of shrubs which depend in part from the recent fire history. Anthropogenic perturbation of the natural fire regime would have therefore distorted the role of fire mediated interactions as drivers of the dynamics of the vegetation of this temperate savannah.