Article Figures & Data
Figures
- Figure 1.
Failure of Q. agrifolia in San Luis Obispo County, California. The tree had a dbh of 100 cm (40.5 in.). It failed at the roots during heavy spring rains, with soggy soil and gusty winds. The failed tree had been growing in a residential setting that was a native stand prior to human occupancy (visible in the background). Note the soil disturbances: Herbaceous ornamentals were planted around the base of the tree, requiring irrigation on the trunk and root system; and vehicle traffic, parked cars, etc. extended almost to the trunk. Root decay was present. This photo was taken by CTFRP cooperator Ted Elder 1 to 2 months after the failure.
Tables
- Table 1.
Frequency of location of failure (%) by tree group. Failure location percentage also divided into failures occurring at ground level (trunk) plus below (root) and failures occurring above ground (trunk above ground level and branch).
Location of failure Q. agrifolia Hardwoods Eucalyptus Conifers Q. lobata Other oaks Trunk (%) 28.9 30.6 28.1 23.6 33.8 31.3 Branch (%) 26.4 34.2 53.0 55.0 35.1 33.8 Root (%) 44.6 35.2 18.9 21.4 31.1 35.0 Ground level and below (%) 54.0 45.0 24.0 25.0 35.0 45.0 Above ground level (%) 46.0 55.0 76.0 75.0 65.0 55.0 - Table 2.
Location of failure vs. percentage (of group total) associated with decay (all decay types combined).
Decay Q. agrifolia Hardwoods Eucalyptus Conifers Q. lobata Other oaks Trunk (%) 97 65 50 40 71 79 Branch (%) 73 33 28 13 62 80 Root (%) 78 69 51 37 91 96 All locations (%) 83 55 39 24 75 86 - Table 3.
Chi2 probabilities from 32 individual 2 × 2 matrices. Decay (presence or absence) by tree group (pairwise).
Decay Qa × HW Qa × Ql Qa × Q other Qa × euc AllOak × HW HW× con HW× euc Euc × con Trunk <0.001 0.01 0.07 <0.001 <0.001 < 0.001 0.09 NSD Branch <0.001 NSD NSD < 0.001 < 0.001 < 0.001 NSD < 0.001 Root NSD NSD 0.07 0.02 < 0.001 < 0.001 0.06 NSD All locations < 0.001 NSD NSD < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 Qa = Q. agrifolia, Ql = Q. lobata, Q other = Quercus other, euc = eucalyptus, con = conifer, HW = hardwood.
- Table 4.
Structural defects most frequently associated with failure. Percentage is of the total number of failures for each tree group.
Top three Q. agrifolia Hardwoods Eucalyptus Conifers Q. lobata Other oaks 1 Failed portion dead (root) 11.2% Heavy lateral limbs (branch) 9.2% Heavy lateral limbs (branch) 18.5% Heavy lateral limbs (branch) 36.5% Heavy lateral limbs (branch) 9.6% Heavy lateral limbs (branch) 17.7% 2 Multiple trunks/ codominant stems (trunk) 8.6% Multiple trunks/ codominant stems (trunk) 8.7% None (branch) 9.8% Multiple trunks/codominant stems (trunk) 6.3% Failed portion dead (root) 8.2% Failed portion dead (trunk) 11.4% 3 Failed portion dead (trunk) 7.8% Failed portion dead (trunk) 6.5% Multiple branches one point (branch) 8.7% Multiple trunks/ codominant stems (branch) 6.3% Heavy lateral limb (trunk) 5.5% None (root) 8.9% - Table 5.
Percentage of failures associated with precipitation for each location of failure (root, trunk, or branch) and for all locations grouped (all failure locations). Rain, fog, and snow are combined.
Location of failure Q. agrifolia Hardwoods Eucalyptus Conifers Q. lobata Other oaks Trunk (%) 18 37 39 57 9 59 Branch (%) 10 17 43 60 26 48 Root (%) 73 66 73 57 65 69 All locations (%) 40 40 48 59 34 59 - Table 6.
Percentage of failures for each location of failure and for all locations grouped by wind speeds less than or equal to 5 mph (8 kph).
Location of failure Q. agrifolia Hardwoods Eucalyptus Conifers Q. lobata Other oaks Trunk (%) 52 17 28 24 73 59 Branch (%) 63 32 28 28 52 53 Root (%) 36 8 12 17 46 17 All locations (%) 49 19 25 25 57 36 Location of failure Q. agrifolia Hardwoods Eucalyptus Conifers Q. lobata Other oaks Trunk (%) 2 4 4 5 4 4 Branch (%) 1 2 5 11 3 5 Root (%) 27 19 5 7 11 12 All locations (%) 30 25 14 23 18 21 - Table 8.
Grade change—cut or fill versus other choices combined from the report form field “site topography.” Percentage of failures at each location associated with a grade change.
Location of failure Q. agrifolia Hardwoods Eucalyptus Conifers Q. lobata Other oaks Trunk (%) 7.6 1.6 1.8 1.1 5.8 5.5 Branch (%) 7.6 1.0 1.0 2.5 8.7 5.5 Root (%) 14.4 1.6 1.8 2.3 11.6 9.6 All locations (%) 29.6 4.2 4.6 5.9 26.1 20.6
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