Why plants bother: root proliferation results in increased nitrogen capture from an organic patch when two grasses compete

We investigated whether the capacities of Lolium perenne L. and Poa pratens is L. roots to proliferate locally and to alter local nitrogen (N) inflows in a decomposing organic matter patch were important in their capture of N when grown together. In the presence of a patch, plants of both species wer e significantly heavier and contained more N. Root length and weight densit ies increased in the patch, but specific root length was unaltered. Althoug h both species proliferated roots in the patch, L. perenne produced greater root length densities than P. pratensis, and also captured more N from the patch. Indeed, total N uptake from the patch was related to root length de nsity within the patch. N inflows (rate of N uptake per unit root length) i n the patch were no faster than in the whole root system for both species. Under the conditions of this study, root proliferation in an organic patch was more important for N capture from the patch than alterations in N inflo ws. Local proliferation of roots may be a key factor in interspecific compe tition for non-uniformly distributed supplies of N in natural habitats, so resolving the previous uncertainty as to the 'adaptive' nature of root prol iferation.