FIRE EFFECTS
SPECIES: Cupressus forbesii | Tecate Cypress 



IMMEDIATE FIRE EFFECT ON PLANT : 
Most fires probably kill Tecate cypress.  Some large trees could
probably survive surface fires; however, most large trees in burned
areas are located on bare or rocky sites that may have been left
unburned [39].  Cypress thickets in California are conducive to crown
fires, which kill most trees.  Some trees survive when fires are patchy
[39].  At the Rancho Santa Ana Botanic Garden in southern California on
October 8, 1943, a severe fire killed one lot of Tecate cypress trees.
Several other lots were partially lost to the fire [40].  

Cones of the California cypress species open as the resin melts and
boils.  Rapid charring of the thick cone scales extinguishes the flames,
leaving seeds unburned [1].  Five months after an October 1965 fire on
Tecate Peak, charred cones retained only 50 percent of seed [39].


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Tecate cypress trees release large quantities of seed after fire [40].
Seedling establishment occurs primarily in the first growing season
following fire [15,43].  A large number of Tecate cypress seedlings were
found growing on Sierra Peak 5 months after a November 1948 fire.
Seedlings were observed on Tecate Peak 3 months after an October 1965
fire.  Five months after the fire the following densities (per acre)
were recorded [1,39]:

                             burned site             unburned site

Tecate cypress trees         10,048 (dead)           15,232 (live) 
Tecate cypress seedlings     576 (live)              0

Investigations made on Tecate Peak since the October 1965 fire indicate
that this grove may be diminishing in size.  Prefire density as
determined from fire-killed trees was 3,872 mature trees per hectare.
The 1970 density of cypress seedlings on burned sites was 384 per
hectare, with adjacent unburned thickets having an average density of
6,093 trees per hectare [39].

On a 1976 burn in a 34-year-old Tecate cypress stand on Otay Mountain,
seedling density decreased from a prefire level of 2.88 per square
foot (32/sq m) to 1.6 per square foot (18/sq m) [41].





DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Although fire is important for releasing seed and preparing seedbeds for
Tecate cypress establishment, fires occurring too frequently in Tecate
cypress groves may destroy them by eliminating reproduction.  Up to a
point, reproductive success increases with an increase in the fire-free
interval [42], but fire must occur before tree senesce or the trees fail
to reproduce.  

Cone production begins at an early age and cones accumulate on trees;
because of greater productivity and accumulated cone crops, postfire
seedling establishment is greater in stands over 50 years of age at the
time of burning than in stands less than 50 years [42].  Data from three
studies were combined to estimate the rate of Tecate cypress first-year
seedling density as a percentage of prefire stem density.  By about 36
years of age, Tecate cypress reproduction density, if the stand is
burned, can equal or exceed that of the original stand [7]:

       Stand age (yrs.)       Reproductive rate (%)       Source

             10                    negligible              [41]
             19                           0.1               [1]
             20                           2.9              [41]
             20                          26.5               [1]
             30                          15.7              [41]
             36                        1206.5               [7]
             39                        1387.3               [7]
             63                        1400.0              [41]

Fires at intervals of less than 35 to 40 years would be likely to reduce
stand density [7].    

Zedler [41] suggested that Tecate cypress populations on Tecate Peak and
Otay Mountain have declined because of increased numbers of human-caused
fires.  Stands burned after 21 and 28 years have marked declines in
density [41].  Stands 28 and 34 years old did not reestablish vigorously
enough to maintain prefire densities.  Zedler [41] stated that the
necessary fire-free interval is greater than 40 years, and therefore
longer than the current 25-year fire interval reported by Armstrong [1].
On north-facing slopes of Tecate Peak, two stands burned in 1880, 1944,
and 1975 [41].  One stand (Smuggler's Canyon) also burned in 1965.
Estimated Tecate cypress densities are shown below:

             Smuggler's Canyon                    Bigrock Stand

Year     Time since        cypress          Time since        cypress
         last fire (yrs.)  trees/sq m*      last fire (yrs.)  trees/sq m*

1943       no data           no data               63             (1.0)      
1945           0.5             (1.5)              0.5           (>14.0)
1965            11             > 1.4          no data           no data
1966           0.5            (0.04)          no data           no data
1972             7              0.03               28               8.9
1976             1              0.02                1               1.4

* Figures in parentheses are estimates based on extrapolation from other
stands of similar age; estimates of density are conservative.  

In the past 67 years the fire frequency on Tecate Peak has gone from
one fire every 40+ years to one fire every 15 years in some areas.  In
the same period, the average extent of Tecate cypress has dropped from
260 acres (105 ha) to 74 acres (31 ha) [42].  On the Smuggler's Canyon
site, Tecate cypress has been reduced in less than 35 years from a
dominant to a minor vegetational component [41].  The decline in density
has not been as drastic in the Bigrock Stand because of one less fire in
1965 [41].

Dunn [7] has proposed the following fire frequency categories and
subsequent responses by Tecate cypress:

high (1-25 years)- elimination of Tecate cypress from plant community
moderate (26-39 years)- unlikely to maintain present range of Tecate cypress
low (40+ years)- maintenance of Tecate cypress population 

Related categories for Species: Cupressus forbesii | Tecate Cypress