Plant Competition in Relation to Neighbor Biomass: An Intercontinental Study with POA Pratensis

Abstract

A standardized neighbor removal experiment was conducted in 12 plant communities located on three continents to test the null hypothesis that competition intensity (CI) was independent of the amount of plant biomass present. Six plots were chosen in each community to cover the range oflocal variation in plant biomass. In each plot the relative growth rate (RGR) of transplanted Poapratensis (Poaceae) seedlings was compared in the presence and absence of neighbors. Neighbors were removed experimentally using R. J. READER ET AL. Ecology, Vol. 75, No. 6 herbicide. Removing neighbors increased RGR of transplants significantly in most plots. CI increased with an increase in the amount of neighbor biomass present in one community where the range of neighbor biomass was greater than in any other community. In contrast, CI did not change significantly with an increase in neighbor biomass in other communities where the range of neighbor biomass was smaller. For the communities combined, CI was not related to neighbor biomass in a consistent fashion. These results indicate that competition may reduce growth over a wide range of habitat productivity, but the relationship between CI and neighbor biomass may differ among communities.

Don't Diss Integration: A Comment on Ricklefs's Disintegrating Communities

“…These are excellent examples of how, in current community ecology, regional (historical) and local processes have been combined to provide complete "interdependent" perspectives as never before. Other examples of ecologists integrating regional-and local-scale spatial processes and geological-scale temporal processes include synthesis of phylogenies and contemporary evolution by exotic invaders (e.g., Maron et al 2004), the linking of evolutionary phylogenies of insect speciation and specialization to hosts (e.g., Farrell and Mitter 1990;Farrell 1998), exploration of latitudinal gradients in plantinsect and plant-plant interactions (e.g., Bertness and Ewanchuk 2002;Siska et al 2002), integration of geomorphology with long-term community development (e.g., McAuliffe 1994), biogeographic comparisons of plant-plant interactions (e.g., Reader et al 1994;Callaway et al 2002;Brooker et al 2005;Kikvidze et al 2005;Tirado and Pugnaire 2005), and biogeographic studies of invasions (e.g., Reinhart et al 2003;). Furthermore, recent empirical studies show that the local patterns of genetics-based community structure can scale up to the regional level.…”

Plant interactions are unimportant in a subarctic–alpine plant community

“…For example, strong plant interactions are often presumed to equate to high importance with respect to species abundances and a range of plant community characteristics (Reader et al 1994, Brooker et al 2005. Intensity is defined as the absolute decrease or increase in plant performance (e.g., growth, metabolism, fecundity) caused by an interaction, while importance is the change in plant performance from an interaction relative to all other factors (e.g., herbivory, stress, and so on).…”

Scales of variation in the effects of limpets on rocky shores in the northwest Mediterranean

“…Although multiscale analyses on the spatial and temporal patterns of distribution of natural populations are increasing both in terrestrial and aquatic systems (Schneider 1994), and the need for large-scale experiments has been emphasized (Paine et al 1985, Reader et al 1994, Carpenter et al 1995, Berlow & Navarrete 1997, few experimental investigations have examined multiple scales of variation in ecological processes. Studies of this sort are important for a number of reasons.…”