The importance of transplant size and gap width in the botanical enrichment of species-poor grasslands in Britain

A series of five grasslands of differing agricultural productivity and spec ies diversity was chosen for this study. Four of these areas were divided i nto three sub-plots, each under a different management regime (either mown, sheep, or cattle grazed). Each sub-plot was inoculated with 180 transplant s comprised of 12 individuals of 15 perennial species. These species were c hosen to provide a spectrum of 'phytometers' to evaluate the receptivity of the grasslands to species introduction. Half of the plants were 9-cm pot-g rown transplants, the other half, 2-cm plug plants. One-third of each of th e transplant sizes was inserted into either 0-cm, 15-cm, or 30-cm-diameter gaps. Evaluation of species enrichment success was made by monitoring the s urvivorship of the transplants over a three-year study period. The fifth gr assland was already species-rich and, therefore, left untreated and used as a reference community. The species could be classified into three main gro ups on the basis of their survivorship: (a) species with higher survivorshi p for pot than plug transplants; (b) species that established significantly better as plug than as pot transplants; and (c) species that suffered equa lly high mortalities as either pot: or plug transplants. For three out of t he four grasslands, the size of competition-free gaps was not significant i n enhancing survivorship for either pot or plug transplants. Gap creation o nly aided survivorship for the set of plug plants inserted into the most pr oductive grassland. Transplant survival was strongly negatively correlated with soil P and K concentrations, and peak biomass. In this, the establishm ent phase, the three management treatment regimes did not have a significan t differential effect on transplant survival. The results are discussed in relation to practical techniques for restoring species-poor grasslands usin g transplants.