Fires Following Bark Beetles: Factors Controlling Severity and Disturbance Interactions in Ponderosa Pine

Fire Ecology

Table 1 Stand and fuel characteristics in Southwestern mixed-species stands dominated by ponderosa pine (host species) used for the design of fire simulation input. Mortality was attributed to both Ips and Dendroctonus bark beetles. Simulation mortality levels are based on the low, average, and high levels observed in 60 field plots (Hoffman et al. 2012 a). DBH = diameter at breast height, HGT = tree height, and CBH = canopy base height.

	No mortality	20 % mortality	58 % mortality (mean)	100 % mortality
Total density (trees ha⁻¹)	467	400 (live) 67 (dead) 467 (total)	273 (live) 194 (dead) 467 (total)	134 (live) 333 (dead) 467 (total)
Density Pinus ponderosa (trees ha⁻¹)	333	266 (live) 67 (dead) 333 (total)	139 (live) 194 (dead) 333 (total)	0 (live) 333 (dead) 333 (total)
Host density (%)	71.3	66.5	50.9	0
Density non-host species^a (trees ha⁻¹)	134	134	134	134
Mean DBH (cm)	23.5	23.5	23.7	24.2
Mean HGT (m)	9.6	9.6	9.7	9.9
Mean CBH (m)	3.2	3.2	3.2	3.2
Crown width (m)	3.3	3.3	3.4	3.4
Foliar fuel load (kg m⁻²)	1.11 (live) 0.00 (dead) 1.11 (total)	0.96 (live) 0.15 (dead) 1.11 (total)	0.66 (live) 0.45 (dead) 1.11 (total)	0.34 (live) 0.76 (dead) 1.11 (total)
Canopy bulk density (kg m⁻³)^b	0.171 (live) 0.000 (dead) 0.171 (total)	0.147 (live) 0.024 (dead) 0.171 (total)	0.101 (live) 0.07 (dead) 0.171 (total)	0.051 (live) 0.120 (dead) 0.171 (total)
Foliar live fuel moisture (%)	100	100	100	100
Foliar dead fuel moisture (%)	15	15	15	15
Canopy fuel moisture content (%)	100	88	66	41
Surface herbaceous fine fuel (kg m⁻²)	0.005	0.005	0.005	0.005
Herbaceous fuel moisture (%)	30	30	30	30
Dead fine fuel load (kg m⁻²)	0.91	0.91^c	0.91^c	0.91^c
Litter depth (cm)	6.8	6.8^c	6.8^c	6.8^c
Litter moisture (%)	3	3	3	3

^a Non-host species included pinyon pine, Gambel oak, Douglas-fir, Rocky Mountain juniper (Juniperus scopulorum Sarg.), Utah juniper (J. osteosperma [Torr.] Little), oneseed juniper (J. monosperma [Engelm.] Sarg.), and alligator juniper (J. deppeana Steud.).
^b Canopy bulk density was estimated using load over depth method. The depth of the canopy layer was the difference between mean tree height and mean canopy base height.
^c In gray phase-mortality domains, the mass of dead foliage was added to the surface fuel load, and the litter depth was increased to account for the addition of the dead foliage.