Time since fire and prior fire interval shape woody debris dynamics in obligate‐seeder woodlands

Woody debris plays an important role in many ecosystem functions, including nutrient and carbon cycling, providing substrates for plant recruitment and habitat for fauna. Fires can affect woody debris stocks, through generating new pieces by killing or severing plant parts and consuming pre‐existing woody debris. We develop a model of woody debris dynamics with variation in time since fire and prior fire interval applicable to obligate‐seeder forests and woodlands, considering down woody debris and standing dead trees as discrete components. We then test predictions of change in woody debris derived from this model in Eucalyptus salubris woodlands in South‐Western Australia, using a multi‐century chronosequence with recent fires varying between having short (<50 yr since the previous fire) or long (>50 yr, but often much longer) prior intervals. As per our woody debris dynamics model, most attributes measured were affected by time since fire, prior fire interval, or their interaction. Woody debris biomass was greatest shortly after fire, reflecting high quantities of standing dead trees resulting from stand‐replacement disturbance. Standing dead tree density and biomass then declined with increasing time since fire, but individual dead tree size was high beyond 200 yr since fire. Down woody debris biomass remained relatively stable with time since fire, but piece size increased. Dimensions of woody debris were strongly influenced by prior fire interval, with long prior intervals resulting in pieces at least twice the size than those occurring after short prior intervals. Fire management to maximize the availability of large woody debris pieces for fauna should aim to minimize short fire intervals, while from a carbon management perspective, all fires in obligate‐seeder forests and woodlands set in train large and prolonged emissions of carbon. Woody debris, comprising both standing dead trees and pieces of trunks, branches, and roots lying on the ground surface (down woody debris; DWD), has a role in many important ecosystem functions (Harmon et al. 1986). Woody debris harbors carbon and nutrients, and influences surrounding soil properties and plant recruitment (Goldin and Hutchinson 2013, Goldin and Brookhouse 2015). Woody debris also provide shelter, basking, and foraging habitat for a range of animals, and energy and nutrients for decomposer organisms (Harmon et al. 1986, Lindenmayer et al. 2002, Luck 2002). For many animals, the habitat value of woody debris is determined by the size and condition of pieces (Lindenmayer et al. 2002). For example,