Fire Effects on Vegetation September 13, 2006

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.

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

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

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

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

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

Vegetative: Another Perspective Classification based on the position of the perennating buds relative to the soil surface What organ is missing? Geophytes B Basal Meristems

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

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

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

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

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

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

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

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

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

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