Seasonal Fire Effects on Seed Banks in a Semi-arid Grassland
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Transcript of Seasonal Fire Effects on Seed Banks in a Semi-arid Grassland
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Sevilleta NWR LTERCJ Jewell
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Effects of Fire: release of nutrients breakdown of hydrophobic plant litter breakdown of dormancy removal of inhibiting chemicals
Impact on plant communities varies among seasons and across sites
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Belowground plant community Dispersed seeds
germinate immediately die remain dormant
Transient seeds Persistent seeds
Seed bank Benefits of seed dormancy
(Fenner & Thompson, 2005)
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Species diversity Biodiversity Genetic diversity Food sources Environmental stimuli
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Fire triggers seed germination and seedling recruitment by the Removal of vegetation Intense temperatures recorded in the soil
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Dominant vegetation is perennial grasses grow in the summer dormant in fall and
winter More seeds available
during spring/summer Abundance decreases
in autumn/winter
Blue GramaBlack Grama
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Sevilleta studies: Establishment ecology of Creosote Recruitment studies from seed banks Seedling establishment after removal of
dominant species How fire affects vegetation and insect
diversity
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1) What is the composition and size of the seed banks in the fall, summer, and control burn plots?
2) Does the seasonality of fire affect seed bank size and content?
3) How does fire affect seedling germination in the field?
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Fire will cause an overall decrease in the size and species diversity in the seed bank
The summer burn plots will have a greater amount of viable seeds and species richness compared to the fall burn plots
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Pictures provided by Laura Calabrese
Sevilleta NWR/LTER McKenzie Flats, 2.8
miles south of Black Butte gate
34° 21’ 33.0’ N 106° 41’ 25.9’ W
Vegetation dominated by the grasses blue grama (Bouteloua eriopoda), and black grama (Bouteloua gracilis).
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C5
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10m
10m
40m
60m
2m
40m
40m transect with flags every 2mCollected 20 10cm (length) x 10cm (width) x 2cm (depth) samples per plotTotal of 20 samples from 6 plots = 120 soil samples
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3 Treatments X 2 Plots per Treatment X 20 soil samples per plot = 120 samples
Randomly selected 15 soil samples per plot
90 soil samples used; 30 per treatment Randomly distributed selected samples in
the Sevilleta Lath House
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•90 26.7cm x 53.3cm flats in Sev Lath House •Soil mixture contains half Metromix 360 and half sandbox sand•Spread soil sample over mixture•Watered daily
•Marked and counted new seedlings weekly•Recorded if monocot or dicot
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•Monocots:•Embryo as one cotyledon•Flower parts in 3s•Parallel Veination•Grasses-no secondary growth
•Dicots:•Embryo has two cotyledons•Flower parts in 4s or 5s•Reticulated/Branched Veination•Woody species-secondary growth
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SAS Wald Chi-Squared=11.7953 P=0.0027 DF=2
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SAS Monocots
Wald Chi-Square=9.7042 p value=0.0078 DF=2 • Dicots
• Wald Chi-Square=0.242• p value=0.8860• DF=2
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9 sample areas from each of the 6 plots=54 areas
A 30cm X 30cm niner was used to count number of naturally germinating seedlings in each sample area
Specific species were identified when possible
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Plpa2- Plantago patagonica, native, Herb, Annual
Dapu7 - Dasyochloa pulchella, native, Grass, Perennial
Gusa2- Gutierrezia sarothrae, native, Shrub, Perennial
Chsp- Chloracantha spinosa, native, Herb, Perennial
Assp- Asclepias speciosa, native, Herb, Perennial
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SAS Wald Chi-
Square=11.6579 P=0.0029 DF=2
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•SAS•Monocot
•Wald Chi-Squared=12.1415 •P=0.0023•DF=2
•Dicot•Wald Chi-Squared=5.8969• P=0.0524•DF=2
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Fires negatively affect the seed bank in the short term
Semi-arid grasslands are not adapted to fire Monocots and dicots are equally affected by
seasonal fire After a summer burn, there is more space
available for newly released seeds, so more can germinate right away
Species found in the field are a fair representation of what may be found in the seed bank, but not an absolute reference
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Limited sample size Lath house conditions Time since burns
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Long term effects of fire Flotation method to mechanically find the
seeds in soil samples (30 extra samples) Assess spring seed bank Assess how fire affects the seed bank and
vegetation of shrublands and woodlands on the Sevilleta
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Sevilleta NWR LTER UNM Jennifer Johnson Diane Marshall Tim Lowrey Terri Koontz All Sev 2008 REUs
Especially Damon Lowrey Molly Ladd And everyone who helped me water!!
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Lath House seedlings at the end of
the rainbow!