Shifts in species dominance at a biome transition zone: Importance of asymmetric competition to long-term trends

Title	Shifts in species dominance at a biome transition zone: Importance of asymmetric competition to long-term trends
Publication Type	Conference Paper
Year of Publication	2009
Authors	Peters DC, Yao J
Conference Name	2009 LTER All Scientist Meeting
ARIS Log Number	243394
Keywords	asymmetric, B. gracilis, black grama, Bouteloua eriopoda, creosotebush, LTER, Sevilleta
Abstract	Landscapes at the Sevilleta LTER site are dominated or codominated by two perennial grasses from different biomes, Bouteloua eriopoda (black grama) from the Chihuahuan Desert and B. gracilis (blue grama) from the shortgrass steppe, and the Chihuahuan Desert shrub Larrea tridentata (creosotebush). We used a long-term removal study to examine inter-specific interactions between these dominant species, and to determine which species would eventually dominate following the removal of the others. Plants of the dominant species were removed from 5 3m x 4m plots in 1995 at five sites that were either dominated by one of the three species (blue grama grasslands, black grama grasslands, cresootebush shrublands) or at ecotones codominated by two species (blue grama/black grama; black grama/creosotebush). Plant cover is estimated annually, and removals have been conducted annually since that time. Results show that removal of black grama has little effect on cover of blue grama whereas removal of blue grama or creosotebush results in marked increases in cover of black grama. Our results show that competition between black grama and either blue grama or creosotebush is asymmetric. These interactions suggest that black grama dominance may be reduced in the future under climate conditions that favor growth of either blue grama or creosotebush since these species can outcompete black grama. Landscape patterns associated with soil texture can also be explained by these interspecific interactions for soil water in this semiarid environment.