Competition effects on wiregrass (Aristida beyrichana) growth and survival

We investigated neighboring plant effects (competition and facilitation) on wiregrass establishment in two frequently encountered restoration situations of former longleaf pine-wiregrass habitats in the Southeastern United States: longleaf pine plantations and previously cultivated fields. In the plantation experiment, we specifically examined canopy removal, neighboring wiregrass density, and aboveground and belowground effects on establishment and growth of wiregrass seedlings at two different ages (3 weeks and 6 months) with 3 competitive exclusion treatments (aboveground exclusion, belowground exclusion, or no exclusion). Competition treatment effects were age-dependent for survivorship and growth. Survival of 6 month old seedlings was unaffected by competition treatment; whereas, three week old seedling survival was greatest where roots were excluded. Seedling size increased with root exclusion for 6 month seedlings, but not for 3 week old seedlings in plots lacking neighboring wiregrass. Where wiregrass was present, both 3 week and 6 month old seedlings increased growth with root exclusion. Furthermore, where neighboring wiregrass plants were absent, increasing canopy density resulted in decreased seedling size, but did not affect survivorship. In old fields, fertilizer treatments and weeding effects were also assessed using 3 week and 6 month old seedlings. Fertilizer application did not benefit seedling survival or growth and reduced survivorship of 3 week old seedlings. Seedlings were smaller where neighboring old field, weedy vegetation was present regardless of wiregrass seedling age; whereas, survival was dependent on seedling age at time of planting. Six month old seedling survivorship remained high regardless of weeding treatment. It is still unclear whether fertilizer application is beneficial to the successful establishment of wiregrass.