دانلود کتاب The Effects Of Fire On The Life History Traits Of Tallgrass Prairie Forbs

The effect o f fire frequency, fire season, and fire temperature on tallgrass prairie
plants were studied in three separate but related studies. First, I examined the effect of
fire on the life history traits of five species o f tallgrass prairie forbs ( Baptisia bracteata ,
Oenothera speciosa, Vemonia baldwinii, Salvia azurea, and Solidago missouriensis).
The forbs studied here did not exhibit a positive response to any one particular bum
frequency, while four o f the five did respond positively to summer burning. There were
only two underlying similarities among these five species o f forbs, a lack o f a relationship
between percent cover data and sexual reproductive effort and all five forbs behave like
satellite species, becoming temporarily locally absent at least once during the last 18 years.
Neither fire frequency or fire season produced an overriding influence on plant growth
and reproduction.
In the second study, I examined what role fire frequency and fire temperature play
in altering rhizome development and depth distribution. Rhizome depth was found to be
greatest on infrequently burned watersheds. The best predictor o f maximum soil
temperature generated by fire was initial soil temperature. Fire frequency did influence
rhizome depth, but the differences in rhizome depth were not directly due to lethal fire
temperatures. Rhizome and tiller density was highest on frequently burned watersheds,
though the probability of tillering was greatest on infrequently burned watersheds.
Finally, I study examined the effects o f fire on the tallgrass prairie forb Solidago
canadensis. S. canadensis showed increases in percent cover, genet size, aboveground
biomass, reproductive biomass, flower number and sexual reproductive effort (SRE) in
response to infrequent burning. Mean rhizome number, length, depth, and mass were all
significantly greater in sites with low fire frequency. Data indicate that this species is
negatively affected by frequent fire, however, sexual reproductive effort was significantly
higher in infrequently burned sites, providing no support for the hypothesis that clonally
herbs in unfavorable sites “escape” poor conditions though increased SRE