Changes in rainfall amount and frequency do not affect the outcome of the interaction between the shrubRetama sphaerocarpaand its neighbouring grasses in two semiarid communities.
We evaluated the net outcome of the interaction between the shrubRetama sphaerocarpa, our target plant, and different herbaceous neighbours in response to changes in the magnitude and frequency of rainfall events during three years. The experiment was conducted in natural and anthropogenic grasslands dominated by a perennial stress-tolerator and ruderal annual species, respectively. In spite of the neutral or positive effects of neighbours on water availability, neighbouring plants reduced the performance ofRetamajuveniles, suggesting competition for resources other than water. The negative effects of grasses on the photochemical efficiency ofRetamajuveniles decreased with higher water availabilities or heavier irrigation pulses, depending on the grassland studied; however, these effects did not extent to the survival and growth ofRetamajuveniles. Our findings show the prevalence of competitive interactions among the studied plants, regardless of the water availability and its temporal pattern. These results suggest that positive interactions may not prevail under harsher conditions when shade-intolerant species are involved. This study could be used to further refine our predictions of how plant-plant interactions will respond to changes in rainfall, either natural or increased by the ongoing climatic change, in ecosystems where grass-shrubs interactions are prevalent.
Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, 28933 Móstoles, Spain.
Santiago
S
Soliveres
Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, 28933 Móstoles, Spain ; Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523, USA ; Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
Pablo
P
García-Palacios
Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, 28933 Móstoles, Spain.
Fernando T
FT
Maestre
Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, 28933 Móstoles, Spain.
Adrián
A
Escudero
Área de Biodiversidad y Conservación, Departamento de Biología y Geología, Escuela Superior de Ciencias Experimentales y Tecnología, Universidad Rey Juan Carlos, 28933 Móstoles, Spain ; Museo Nacional de Ciencias Naturales, MNCN, CSIC, Serrano 115 dpdo., E-28006 Madrid, Spain.
Fernando
F
Valladares
Stipa tenacissima L.; competition; pulse-driven ecosystems; roadside slope; shrub encroachment