FIRE EFFECTS
SPECIES: Pinus cembroides | Mexican Pinyon 



IMMEDIATE FIRE EFFECT ON PLANT : 
Low-severity fires kill Mexican pinyon seedlings and young trees; severe
fires kill even mature trees [17,62].  Fire probably kills seeds unless
they are covered with an insulating layer of soil.


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Mexican pinyon probably establishes from seed cached by birds and small
mammals following fire.  A proposed sere for the pinyon-juniper
woodlands in which Mexican pinyon occurs suggests that tree seedlings
establish within approximately 30 years following fire [25].

In narrow canyons in the highlands between Puebla and Veracruz, Mexico,
Mexican pinyon forests reach crown closure 20 years following fire [80].


DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Although varying with microsite differences or canopy closure, fuel
loads in pinyon pine habitats where Mexican pinyon is the principal tree
are usually discontinuous and light, resulting in low fire frequencies
[57,62,100].  Fuel in uncut stands is mostly on the surface beneath tree
canopies, which limits fire spread between trees.  With open canopies,
the understory can vary from sparse to dense herbaceous and shrubby
vegetation [17,80].  Surface fuel build up is slow in low productivity
pinyon-juniper savannas [62].  Fire effects in this vegetation type are
not well understood [17].

Fire suppression and reduction of surface fuels by grazing have resulted
in the invasion of grasslands and chaparral by pinyon [17,65,82,100].
Prescribed burning can kill invading seedlings and young trees less than
4 feet (1.2 m) tall [9,17].  A single fire can reduce Mexican pinyon
sapling density tenfold.  Mexican pinyon 80 years or older are more
resistant to fire [62].  If fires do not kill mature trees, follow up
with mechanical control methods can be used to eliminate pinyon [17,100].

Low-severity surface fires at 50 or 60 year intervals will thin Mexican
pinyon, preventing development of thickets.  Fire intervals greater than
80 years result in dense stands of Mexican pinyon and a build up of
fuel.  There is also a larger risk of severe fires and crowning [62].

In narrow canyons, Mexican pinyon crowns can overlap both with one
another and with herbaceous vegetation on slopes.  Small fires can
easily become crown fires.  Fire hazard can be reduced by thinning
stands [80].

Dwarf mistletoe infection in Mexican pinyon stands may affect fire
hazard conditions by increasing flammability within crowns and
increasing downed woody fuels [35].

Related categories for Species: Pinus cembroides | Mexican Pinyon