Abstract
1.
Plant roots and their mycorrhizal symbionts are critical components of forest eco-
systems, being largely responsible for soil resource acquisition by plants and the main-
tenance of soil structure, as well as influencing soil nutrient cycling. Silvicultural
treatments should be guided by knowledge of how these below-ground components
respond to different forest management practices.
2.
We examined the cumulative effects of 20 years of prescribed burning at 2-year inter-
vals. We measured fine root length density and fine root and mycorrhizal root biomass
in the upper 15 cm of mineral soil in a south-western ponderosa pine forest over a com-
plete burn cycle.
3.
Repeated burning reduced fine root length, fine root biomass and mycorrhizal root
biomass, as well as the amount of nitrogen and phosphorus stored in these below-
ground pools.
4.
Estimates of fine root production, fine root decomposition and nutrient dynamics
were similar in burned and control plots.
5.
Synthesis and applications
. Although repeated-prescribed fire may be an effective,
low-cost approach for reducing fuel loads and lessening the chance of a catastrophic
wildfire in ponderosa pine forests, our results suggest that this strategy may negatively
affect below-ground biomass pools and nutrient cycling processes in the long term. We
recommend that mechanical reductions in fuel loads be conducted in these and similar
forests that have not experienced fire for decades, before fire is reintroduced as a man-
agement tool.