Skip to main content
ARS Home » Plains Area » Las Cruces, New Mexico » Range Management Research » Research » Publications at this Location » Publication #141594
Title: EFFECTS OF FIRE SEASON AND INTENSITY ON PROSOPIS GLANDULOSA TORR. VAR. GLANDULOSA

Author
item Drewa, Paul

Submitted to: International Journal of Wildland Fire
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2003
Publication Date: 6/1/2003
Citation: DREWA, P.B. EFFECTS OF FIRE SEASON AND INTENSITY ON PROSOPIS GLANDULOSA TORR. VAR. GLANDULOSA. INTERNATIONAL JOURNAL OF WILDLAND FIRE. 2003. V. 12(2). P. 147-157.

Interpretive Summary: In ecosystems characterized by the occurrence of natural fire, growth of resprouting woody vegetation may depend more on the seasonal timing of fire than intensity. I explored this hypothesis by examining fire season and intensity effects on response of honey mesquite (Prosopis glandulosa), a resprouting shrub in Chihuahuan Desert grasslands of south central New Mexico. Clipping, as well as low and high intensity fires (natural and added fuels, respectively), were applied during the 1999 growing season and the 2000 dormant season. Both fire season and intensity affected shrub responses. Following fire, numbers of stems were 16% greater and shrub heights were 8% taller after dormant season than growing season treatments of fire and clipping combined. Height and resprout number decreased with increased fire intensity. Fire season and intensity effects on canopy area and stem growth were generally not detected. The results do not support the hypothesis. Instead, fire season and intensity use two different mechanisms that influence shrub responses. Honey mesquite has the potential to respond more after dormant season than growing season fires as determined by carbohydrate availability in root systems at the time of fire. However, realization of this potential is contingent on fire intensity as influenced primarily by the amount of nonwoody fuels. In turn, fire intensity will determine the amount and duration of heat penetration into soils and thus the amount of damage to root crowns.

Technical Abstract: In pyrogenic ecosystems, responses of resprouting woody vegetation may depend more on fire season than intensity. I explored this hypothesis by examining fire season and intensity effects on response of Prosopis glandulosa, a resprouting shrub in Chihuahuan Desert grasslands of the southwestern United States. Clipping, as well as low and high intensity fires (natural and added fuels, respectively), was applied during the 1999 growing season and the 2000 dormant season. Both fire season and intensity affected shrub responses. Numbers of resprouts were 16% greater and heights were 8% taller after dormant season than growing season treatments of fire and clipping combined. Height and resprout number decreased with increased fire intensity. Fire season and intensity effects on canopy area and stem growth were generally not detected. My results do not support the hypothesis. Instead, fire season and intensity use two different mechanisms that influence shrub responses. Prosopis glandulosa has the potential to respond more after dormant season than growing season fires as determined by carbohydrate availability in underground organs at the time of fire. However, realization of this potential is contingent on fire intensity as influenced primarily by fuel amount. In turn, fire intensity will determine the amount and duration of heat penetration into soils and thus the amount of damage to growing points of underground organs.