Fire Effects on Vegetation

1. Fire Effects on Vegetation September 13, 2006

2. Tallgrass Prairie: TTYP • First, think to yourself. Write down any causes, effects, and mechanisms that explain this landscape. • Then, discuss with a partner and be prepared to share with the class.

4. Fire in Tallgrass Prairie • Primary role in maintenance and development • Alteration in physical environment, particularly the litter layer • Changes in resource availability, rapid regrowth • Plant level mechanisms • Human management and the importance of timing

5. Fires Effects on Vegetation • Fire alters the physical environment through removal of live and dead plants from the community • Selectively eliminates part of the plant community • Other plant species are unchanged or have adaptions for regrowth • Thick bark and self pruning of lower branches (Jack pine, Ponderosa pine) • Any plant can be killed by a fire of sufficient severity

6. Understanding the Plant Response • Temporarily reduces resource competition • Moisture, nutrients, and light • Plant adaptations based on strategies of resource allocation

7. Mechanisms of Re-vegetating • Vegetative re-establishment • Seed Survival • Soil stored • Canopy stored • Seedling persistence • Seed dispersal

8. Vegetative: Plant Resource Allocation Comes in Many Forms • Part of an individual plant survives and fire stimulates resprouting • Aboveground and belowground resources • Dormant buds insulated by bark • Root collar sprouts i.e. oaks • Lignotubers; swellings at the base/root collar of shoots of shrub species i.e. manzanita • Root suckering from adventitious roots; roots are formed from stem tissues i.e. aspen

10. Vegetative: Another Perspective Basal Meristems B • Classification based on the position of the perennating buds relative to the soil surface • What organ is missing? Geophytes http://www.nccpg.com

11. Example: Fire Effects in Tallgrass Prairie • Decrease in woody species • Exposed apical meristems • Basal meristems in grass • Protected vegetative growth • Large mass of perennating organs belowground; high root to shoot ratio

12. Seed Survival What advantages does a post-fire environment present for seed germination and seedling survival?

13. Mechanisms for Seed Survival • Seed protection from fire • Enclosure within fruits in the plant canopy • Seed bank survival • Seed coat (scarification), i.e. tallgrass legumes • Seed burial • Seed dispersal • Species killed by fire and seeds don’t survive • Seeds from outside sources

14. Seed Protection: enclosure within fruits • Serotiny - Cone scales are held closed by resinous material and it melts out by the heat of fire and cause to release seeds • Jack pine, Lodge pole pine

15. Seed Protection: soil seed bank Tradeoff between survival of seeds from fire and germination of seeds in different depths (Whelan 1995)

16. Seedling Persistence • Early belowground resource allocation, fast growth post-fire • Longleaf pine grass stage

17. Fire Regimes and Vegetation • Timing • Resistance to fire is low during reproductive stage of plants and high with greater carbohydrate reserves • Severity • Duration and Extent • Dispersal limitations

18. Community Response • Mortality and response of plants to fire is differential among plant species and plants of different age/developmental stage • Fire can shift plant community structure and composition • Example: Tallgrass prairie • Spring burn has differential influence on cool and warm season grasses

19. Studying Fire Effects • Burned vs. Unburned • Pre vs. post-burn

20. Studying Fire Effects Assumptions: • Burned vs. Unburned • the only difference between the two areas is the treatment i.e. soils, successional stage, disturbance history • treatment is uniform, no within burn variation • Pre-burn vs postburn, • treatment is uniform