The effects of gap creation on competitive interactions: separating changes in overall intensity from relative rankings

A central assumption of disturbance ecology equates gap creation with the reduction of overall competitive intensity. I develop the idea that gap creation, due to changes in addition to biomass removal, could also alter the relative competitive rankings among species. I present a quantitative review using meta-analysis in which I separate the effect of gap creation from the effect of competition for species characteristic of different disturbance regimes. Twenty-one studies (with a total of 136 comparisons) directly examined species competitive abilities under cap (disturbed) and matrix (undisturbed) conditions. Overall competitive intensity generally declined in gap conditions, although species characteristic of gap areas responded more strongly to gap creation than did species characteristic of undisturbed matrix areas. Under matrix conditions, matrix species were less affected by competition than gap species, supporting one widespread assumption. However, under gap conditions, matrix and cap species were inhibited to a similar degree by neighbor biomass. These results suggest that gap creation, in addition to decreasing overall competitive intensity, may affect species competitive rankings, possibly due to changes in the environment where the interactions occur.