Mowing and fertilizer effects on seedling establishment in a successional old field

Aims We used a 10-year field experiment that consisted of mowing and fertilizer treatments to evaluate the role of niche limitation in seedling establishment of species from different functional groups and of varying local abundance in an old field undergoing succession.Methods Seedlings of nine different species were planted into a successional field subjected to mowing and fertilizer treatments for 10 years that resulted in different plant communities and resource availability. Species representative of the factorial combination of three functional groups (C 4 grasses, C₃ grasses and legumes) and three abundance categories (abundant, present, or absent in the old field) were planted in four treatments resulting from the factorial combination of annual spring mowing (mowed and unmowed) and fertilizer application (annually fertilized and unfertilized). Survivorship, relative growth rate (RGR) and biomass were measured to determine the role of niche limitation on recruitment and growth.Important findings Mowing increased the establishment success of seedlings. Fertilization had little influence on seedling performance and survivorship. C₃ grasses had the highest survivorship, while C₄ grasses and legumes had equivalent RGRs, but higher than C₃ grasses. By contrast, survivorship of legumes was unrelated to mowing or fertilizer, suggesting that establishment of this functional group was dependent on other, unmeasured conditions or processes. Species already present, but at low abundance, performed better than locally abundant or absent species. Propagule limitation may restrict the arrival of a species. However, recruitment and establishment was subject to niche limitation, which varied among species, functional groups and whether a species is already resident at the site and its abundance. Thus, species interactions restrict establishment during old-field succession, supporting the niche limitation hypothesis.