Enlargement of tree-mortality centers surrounding pine stumps infected by Hetetobasidionannosum in northeastern California

Enlargement of 53 tree-mortality centers surrounding pine stumps infected for about 35 years by Heterobasidionannosum (Fr.) Bref, was studied in northeastern California. At the end of the study period (1992), mean area for all centers was 209 m2 (range 16–701 m2), and the mean rate of radial enlargement was 0.22 m/year (0.7 ft/year). Rates decreased over time and center enlargement essentially ceased at most centers 20–30 years after stump infection. However, 7 centers (13%) continued to enlarge into surrounding stands at a mean rate of radial enlargement of 0.39 m/year (1.3 ft/year), and averaged 557 m2 (0.14 acre) by 1992. Continued enlargement of centers and extension of mortality beyond center stump root zones were associated with adjacent dead trees larger than 20 cm DBH. Many individual centers had different rates of enlargement at different points along their boundaries, ranging from 0 to 0.78 m/year (2.5 ft/year).