SEASONAL FIRE EFFECTS ON SEED BANKS IN A

SEASONAL FIRE EFFECTS ON SEED BANKS IN A SEMI-ARIDGRASSLAND Sevilleta NWR LTER CJ Jewell

FIRE 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

Seed Bank Belowground plant community Dispersed seeds germinate immediately die remain dormant Transient seeds Persistent seeds Seed bank Benefits of seed dormancy (Fenner & Thompson, 2005)

Why are seed banks important? Species diversity Biodiversity Genetic diversity Food sources Environmental stimuli

How Fire affects Seed Banks Fire triggers seed germination and seedling recruitment by the Removal of vegetation Intense temperatures recorded in the soil

Fire Seasonality Dominant vegetation is perennial grasses grow in the summer dormant in fall and winter Blue Grama More seeds available during spring/summer Abundance decreases in autumn/winter Black Grama

What do we know or not know about fire and seed banks? 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

Overall Questions 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?

Hypotheses 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

Experimental Site: Burn Plots Pictures provided by Laura Calabrese Sevilleta NWR/LTER Mc. Kenzie 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).

Site Layout C 5

Collecting Soil Samples 10 m 40 m 2 m 40 m 60 m 40 m transect with flags every 2 m Collected 20 10 cm (length) x 10 cm (width) x 2 cm (depth) samples per plot Total of 20 samples from 6 plots = 120 soil samples

Methods 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

Growing Seedlings! • 90 26. 7 cm x 53. 3 cm 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

Monocots vs Dicots • Monocots: • Embryo as one cotyledon • Flower parts in 3 s • Parallel Veination • Grasses-no secondary growth • Dicots: • Embryo has two cotyledons • Flower parts in 4 s or 5 s • Reticulated/Branched Veination • Woody species-secondary growth

Comparison of seed bank size between treatments 300 25 Total Seedlings 250 Average Number of Seedlings 20 200 15 150 Total 100 Mean 10 5 50 0 0 Control SAS Summer Fall Wald Chi-Squared=11. 7953 P=0. 0027 DF=2 Control Summer Fall

Comparison of seed bank content between treatments 100 90 80 70 60 50 40 30 20 10 0 Total Number of Monocots and Dicots Total Monocots Total Dicot 6 4 Mean Monocot 3 Mean Dicot 2 1 Summer Fall SAS • Average of Monocots and Dicots 5 Control 7 Monocots Wald Chi-Square=9. 7042 p value=0. 0078 DF=2 Dicots • • • Wald Chi-Square=0. 242 p value=0. 8860 DF=2 0 Control Summer Fall

Burn Plot Seedlings 9 sample areas from each of the 6 plots=54 areas A 30 cm X 30 cm niner was used to count number of naturally germinating seedlings in each sample area Specific species were identified when possible

Seedlings Found Assp- Asclepias speciosa, native, Herb, Perennial Dapu 7 - Dasyochloa pulchella, native, Grass, Perennial Plpa 2 - Plantago patagonica, native, Herb, Annual Gusa 2 - Gutierrezia sarothrae, native, Shrub, Perennial Chsp- Chloracantha spinosa, native, Herb, Perennial

Fire effects on seedling germination in the field 30 Mean # of Seedlings per Sample Area Number of Seedlings 25 20 15 Mean # of Seedlings 10 5 0 Control SAS Summer Wald Chi-Square=11. 6579 P=0. 0029 DF=2 Fall

Fire effects on seedling germination in the field 20 Average Number of Monocots and Dicots 18 Number of Seedlings 16 14 12 Mean Monocots 10 Mean Dicots 8 6 4 2 0 Control Summer • SAS • Monocot • Wald Chi-Squared=12. 1415 • P=0. 0023 • DF=2 Fall • Dicot • Wald Chi-Squared=5. 8969 • P=0. 0524 • DF=2

Conclusions 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

Limitations of Experiment Limited sample size Lath house conditions Time since burns

Future Research 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

Acknowledgements 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!!

Questions? Lath House seedlings at the end of the rainbow!