The effects of fire frequency and fire intensity on am fungal spore abundance, species variety and percent root colonization at Schenck Forest and James Goodwin Forest

by Rabe Ranjanivo, Mialy-Tiana

MIALY-TIANA, RABE RANJANIVO. The effects of fire frequency and fire intensity on AM fungal spore abundance, species variety and percent root colonization at Schenck Forest and James Goodwin Forest. (Under the direction of Arthur G. Wollum). Two greenhouse studies were undertaken: (1) To assess the effects of prescribed fire frequency on AM spore abundance, species variety, and AM percent root colonization of Sudan grass Sorghum sudanese L., between an annually burned site, and a seven-year burned site on a loblolly pine, Pinus taeda L. stand, at Schenck Forest, Wake County, NC., (2) To determine the effects of two levels of fire intensity of pile burning (343oC- 371oC and >470oC), at two depths (0-2cm and 3-6cm), by year and season, on AM fungal spore abundance, AM species variety, and AM percent root colonization of Sudan grass Sorghum sudaneseL. at James Goodwin Forest, Moore County, NC. All soil samples were air-dried at room temperature (23oC), stored at 4oC prior to use as inoculum in a greenhouse trap culture. At Schenck Forest, repeated fire was found to impact AM spore abundance though less affecting the species variety. The seven-year burned site had higher number of spores overall. The percent root colonization study revealed non-significant effects of repeated fire between the annually burned and the seven-year burned sites. The percent AM fungal root colonization in spring was always significantly higher than in summer at the annually burned site, but always higher in summer than in spring at the seven-year burned site. Summer had significantly more spores than spring. At James Goodwin Forest, fire disturbance coupled with mild soil surface erosion induced a highly significant difference in AM percent colonization between the control and the disturbed sites pre-burn and burn. Fire disturbance significantly affected AM root colonization by depth compared with unburned. The response of AM root colonization to disturbance is very significantly site specific. The effect of fire intensity is significantly affected by vertical distribution of the propagules. Species variety at both Schenk Forest and James Goodwin Forest non-significantly decreased, propagules survived from high intensity fire but spore numbers were significantly reduced.