oct26 - • What shrubs o Sprouter or non-sprouter o&...

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10/26/09 -Bermuda grass decreases mesquite production with an increase in density -Mesquite is a poor competitor and needs very specific conditions to grow Fire frequency and extent: Fire is a naturally occurring event Lightening is the most common cause of natural fire Probably more frequent historically than today? o Yes! Probably of larger extent historically than today; more and bigger fires historically SW savannahs—fires perhaps every 10 years (no scaring records of grasslands like trees so not totally sure) Fire Frequency in AZ (over 30 yr period 1970-2000) Fires per decade <1 2 4 Mesquite biomass 4.75 0.52 0.078 Mesq:grass ratio 116:1 3:1 1:2 *more frequent fires more equal grass to woody plants more fire = less mesquite less fire = more mesquite -Historic vegetation changes in SW: fire frequency affects woody shrubs Shrubs and Fire: Can fire kill shrubs?
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Unformatted text preview: • What shrubs? o Sprouter or non-sprouter? o & how old/large are they? • Can fire kill a sprouter? o if it is small/young yes (not well developed crown) Mesquite and Fire: • Fire killed 67% of 6-12 month old seedlings • Fire killed 60% of seedlings less than 13 mm dia (1/2 inch) • Fire killed 20% of seedlings 25-51 mm dia (1-2inch) • Fire killed 11% of seedlings greater than 130 mm dia Interaction between fire and grazing: • Fire requires mostly fine fuel • Grazing removes fine fuel • Thus, overgrazing reduced fire frequency • So… o Grazing: less grass, more shrubs o Less grass, less fire, more shrubs o Overgrazed areas help shrubs-Picture of flood plain E. New Mexico, big cotton wood tree dead, no leaves, global warming-Average global temp = 59˚C (might be F) *check*...
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oct26 - • What shrubs o Sprouter or non-sprouter o&...

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