Abstract
Human activity has resulted in high fire frequency in many moist tropical savannas. To simulate the effects of increased fire frequency on woody plants of the cerrado savannas of Brazil, I constructed matrix population models for five species, including a subshrub, two shrubs, and two trees, using four years of demographic data. The models projected that four of the five species will decline under frequent burning but will increase in abundance under infrequent burning. For these four, fire intervals of 2–9 yr are required for long-term persistence, depending on the species. The fifth species, a shrub, was virtually unaffected by burning. Similar data for three herbaceous species were obtained from literature sources. Among the eight species, there was a negative relationship between population growth under annual burning and population growth under unburned conditions. Woody plant species performed best under low fire frequency, and herbaceous species performed best under high fire frequency. Three of the study species propagate vegetatively by producing root suckers. Fire stimulates vegetative propagation in all three species but reduces sexual reproduction. Elasticity analysis revealed that vegetative propagation is more important than sexual reproduction for population maintenance of these three species, and that vegetative propagation is relatively more important under frequent burning. However, stasis and progression were always much more important than either mode of reproduction, with stasis making the largest contribution to population growth. Analyses of life history response experiments were performed to determine what demographic variables contributed most to the population decline under frequent burning. The effect of fire on sexual reproduction contributed little to the overall effect of fire on population growth, particularly for clonal species. Fire-induced mortality also had little effect on population growth, except for Miconia albicans, which has extremely fire-sensitive seedlings. The negative effect of fire on individual size tended to make the greatest contribution to the overall negative effect of fire on population growth, and this effect was greater for the two trees than for the shrub species. The results indicate that growth form was the primary determinant of fire response, while ability to reproduce vegetatively is important to a lesser extent. Current fire regimes are predicted to reduce woody plant density and to favor smaller life forms and species capable of clonal propagation.
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Claims 20
Claim · model-written summary
Four of five modeled woody species decline with frequent burning.
Verbatim
e0“four of the five species will decline under frequent burning”
t0“Woody Plants”
Claim · model-written summary
Four of five modeled woody species increase with infrequent burning.
Verbatim
e0“will increase in abundance under infrequent burning”
t0“Woody Plants”
Claim · model-written summary
The four fire-sensitive species require fire intervals of 2–9 years for long-term persistence.
Not reportedTaxon
Verbatim
e0“fire intervals of 2–9 yr are required for long-term persistence”
Claim · model-written summary
The fifth shrub species was virtually unaffected by burning.
Verbatim
e0“The fifth species, a shrub, was virtually unaffected by burning.”
Claim · model-written summary
Across eight species, population growth under annual burning was negatively related to growth without burning.
Verbatim
e0“Among the eight species, there was a negative relationship between population growth under annual burning and population growth under unburned conditions.”
Claim · model-written summary
Woody species performed best under low fire frequency.
Verbatim
e0“Woody plant species performed best under low fire frequency”
Claim · model-written summary
Herbaceous species performed best under high fire frequency.
Verbatim
e0“herbaceous species performed best under high fire frequency”
Claim · model-written summary
Fire stimulates vegetative propagation in all three species that produce root suckers.
Verbatim
e0“Fire stimulates vegetative propagation in all three species”
Claim · model-written summary
Fire reduces sexual reproduction in the three root-suckering species.
Verbatim
e0“Fire stimulates vegetative propagation in all three species but reduces sexual reproduction”
t0“Woody Plants”
Claim · model-written summary
Vegetative propagation contributes more than sexual reproduction to population maintenance of the three species.
Verbatim
e0“vegetative propagation is more important than sexual reproduction for population maintenance of these three species”
Claim · model-written summary
Vegetative propagation is relatively more important under frequent burning.
Verbatim
e0“vegetative propagation is relatively more important under frequent burning”
t0“Woody Plants”
Claim · model-written summary
Stasis and progression contributed more to population growth than either reproductive mode.
Verbatim
e0“stasis and progression were always much more important than either mode of reproduction”
t0“Woody Plants”
Claim · model-written summary
Stasis made the largest contribution to population growth.
Verbatim
e0“stasis making the largest contribution to population growth”
t0“Woody Plants”
Claim · model-written summary
The fire effect on sexual reproduction contributed little to the population-growth effect, particularly in clonal species.
Verbatim
e0“The effect of fire on sexual reproduction contributed little to the overall effect of fire on population growth, particularly for clonal species.”
Claim · model-written summary
Fire-induced mortality generally had little effect on population growth.
Verbatim
e0“Fire-induced mortality also had little effect on population growth”
t0“Woody Plants”
Claim · model-written summary
Miconia albicans seedlings were exceptionally sensitive to fire.
- Taxon
- Miconia albicans
Miconia albicanse0 - Organ / stage
- seedlingse0
- Outcome
- extremely fire-sensitive seedlingse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Miconia albicans, which has extremely fire-sensitive seedlings”
Claim · model-written summary
The negative effect of fire on individual size was the greatest contributor to reduced population growth.
Verbatim
e0“The negative effect of fire on individual size tended to make the greatest contribution to the overall negative effect of fire on population growth”
t0“Woody Plants”
Claim · model-written summary
The fire effect on individual size was greater in the two trees than in shrubs.
Verbatim
e0“this effect was greater for the two trees than for the shrub species”
Claim · model-written summary
Growth form was the primary determinant of fire response, while vegetative reproduction mattered less.
Not reportedDirection
Verbatim
e0“growth form was the primary determinant of fire response, while ability to reproduce vegetatively is important to a lesser extent”
t0“Woody Plants”
Claim · model-written summary
Current fire regimes are predicted to reduce woody plant density and favor smaller clonal forms.
Verbatim
e0“Current fire regimes are predicted to reduce woody plant density and to favor smaller life forms and species capable of clonal propagation.”