Wood decay and the persistence of resprouting species in pyrophilic ecosystems

Key message Along a fire frequency gradient, we found a savanna tree species had the greatest below ground decay compartmentalization after coppicing as compared to other resprouting species located at mesic gradient positions. In pyrophilic ecosystems, woody plants are repeatedly injured or topkilled (i.e. aboveground tissue is killed) by frequent fires, and many woody species persist in these systems through resprouting. Yet, many vigorously resprouting plants appear unable to persist in frequently burned landscapes. The success of resprouters has generally been attributed to the ability of these plants to store and remobilize carbohydrate reserves. For resprouting species, persistence might not be determined by resource reserves, but rather by their ability to prevent spread of wood decay after injury, there by maintaining the integrity of belowground organs. We hypothesized that species that persist in frequently burned areas are most capable of containing the extent of wood decay. To this end, we measured variables previously identified to limit the extent of decay in woody plants, including plant size, wood density, and lignin and extractable phenolic concentrations, on five woody species that occur along a fire frequency gradient in the Sandhills physiographic region of North Carolina, USA. We induced topkill by coppicing 19–20 individuals of each species. At 9 and 19 months after coppicing, we harvested the root crowns of half of the individuals per species. We found that the most fire-tolerant species ( Quercus laevis ) had the least amount of wood decay overall and the greatest wood density and lignin and phenolic concentrations. Q. laevis also had the least decay at both the 9- and 19-month post-coppicing harvest dates. We suggest that wood decay compartmentalization is a potentially overlooked aspect of resprouting success.