Fire and Vegetation in a Temperate Peat Bog: Implications for the Management of Threatened Species

Abstract

Abstract: Fire plays an important role in structuring wetland ecosystems, but previous studies of New Zealand wetlands have lacked adequate experimental controls. We investigated the effects of fire on the vegetation of a New Zealand peat bog through analysis of microclimate patterns, vegetation change, and peat stratigraphy. We focused on the role of fire in sustaining threatened plant species such as the critically endangered orchid Corybas carsei. Experimental fire significantly increased the surface radiation and daytime soil temperature, and these elevated levels of radiation and temperature persisted 53 months after burning. Immediately after fire no living plant material remained in the burn plots, but within 2 months many of the rhizomatous species were resprouting and 50 months later had returned to prefire abundance. Obligate‐seeding species did not recover their former abundance, but several species not observed in the plots prior to the burns established after fire. Species richness, diversity, and evenness increased following fire but declined in the control plots. Species dominance decreased after fire but increased in the control plots. C. carsei, which was killed during the fire, reappeared in the burn plots 1 year later at a higher density than prior to burning and was still present 4 years after fire. C. carsei flowering was also enhanced following the fire. We found evidence of historical fires, which was supported by radiocarbon dates from a much older adjacent wetland. Our results suggest that disturbances such as fire are important for maintaining a diversity of plant communities, including the presence of nationally threatened and declining plant species in peat bogs. Without such disturbances species such as C. carsei are likely to become locally extinct.