Introduction
Temperate forests in Mexico, mainly composed by Pine and Pine-Oak communities occupy the 9.8% of its territory (SEMARNAT, 2002). Pine forests are considered early succesional communities maintained by fire (Little, 1998), and although fire has been recognized as a detrimental factor of pine forests in México, it also contributes to their maintenance eliminating less resistant species (Rzedowski, 1988; Agee, 1998).
Successful recolonization after a fire will mostly depend on the resistance of seeds to heat (Despain et al., 1996) and the establishment on post-fire environments (Keeley and Fotheringham, 2000). The factors directly affecting seeds during a fire are: temperatures reached, time of exposure (Habrouck et al., 1999; Reyes and Casal, 2001; Nuñez et al., 2003), smoke (Keeley and Fotheringham, 2000) and protection by a cone (Habrouck et al., 1999).
The cone is an efficient barrier towards heat, especially if it is a serotinous cone (Goubitz et al., 2003) or a cone from a serotinous species compared to non-serotinous species (Habrouck et al., 1999)
The cone is an efficient barrier towards heat, especially if it is a serotinous cone (Goubitz et al., 2003) or a cone from a serotinous species compared to non-serotinous species (Habrouck et al., 1999)
Scenarios during a forest fire
A model developed by Habrouck et al. (1999) indicates that during a forest fire, seeds in the surface and the canopy experience higher temperatures (200-250ºC) than seeds in the soil bank (100ºC). The main difference between the canopy and surface scenarios lies in the time of fire residence; surface fires last more (10-20 min) than canopy fires (5 min). Surface fires also can show lower temperatures depending on the amount and quality of fuel.
OBJECTIVE
-Predict cone opening during a forest fire.
-Determine the relative importance of temperature and time of exposure.
-Is the variation in cone opening due to random variation or to treatments applied?
-Determine the relative importance of temperature and time of exposure.
-Is the variation in cone opening due to random variation or to treatments applied?
Hyphotesis
-I expect both of the factors tested contribute to cone opening in a similar way
-In general the opening will increase at higher temperatures and times.
-In general the opening will increase at higher temperatures and times.