Fire managers of southern California chaparral often assume that the amount of dead material in chaparral shrubs is closely related to canopy age. Analysis of chamise (Adenostoma fasciculatum), sampled from southern California shrublands, indicates that the ratio of dead to live components is not related reliably to age of shrub canopy. Further statistical description of the data indicates that fractions of dead material greater than 0.40 are rare. The results provide grounds for seriously questioning current assumptions about the strong relationship between age and fraction dead in southern California chaparral fuels. West J. Appl. For. 5(4):00-00, October 1990.
Managers do not currently use prescribed fire in stands of canyon live oak (Quercuschrysolepis Liebm.) because it is highly susceptible to fire injury. A preliminary study investigating the effects of prescribed burning on this species was initiated on the San Bernardino National Forest in southern California. The purpose was to assess the feasibility of using thinning and prescribed burning to develop shaded fuel breaks in these stands. This paper addresses aboveground tree mortality inventoried 2 and 6 years after a prescribed burn. Aboveground tree stems were judged as live or dead (irrespective of root-zone sprouting). Fire caused approximately 50% mortality in DBH classes ≤15 cm and <10% in larger classes. Between the 2nd and 6th years after burning, tree mortality increased by only 3%. Our results suggest that prescribed fire can be used as a management tool in Q. chrysolepis stands and that tree mortality might be evaluated sooner than previously believed. More investigations are required to identify favorable conditions for prescribed burning in this species, as well as applicability for (i) degree of hazard reduction near the urban wildland interface, (ii) stand improvement by thinning small or crowded trees, and (iii) revitalizing wildlife habitat.
In May 1993, electrical resistance measurements were performed on trees in burned and unburned stands of Caribbean pine (Pinus caribaea Mor.) in north-eastern Nicaragua to determine whether tree vigor was affected by fire. An Osmose model OZ-67 Shigometer with digital readout was used to collect the sample electrical resistance data. Computer-simulated randomization techniques were used to evaluate the significance of differences in electrical resistance between living trees of burned and unburned stands of various ages. Electrical resistance was used as an index of the general metabolic activity of the tree – our chosen definition of tree vigor. Results indicate a loss of tree vigor in stands that burned in comparison with those that did not.
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