• FIRE ECOLOGY OR ADAPTATIONS
• POSTFIRE REGENERATION STRATEGY

FIRE ECOLOGY OR ADAPTATIONS:

Galleta is a rhizomatous perennial [39,43,47,92] which can resprout after top-kill by fire [56].

Desert grassland fire regime: Knowledge of fire frequency and ecological role in desert grasslands is uncertain. Grassland fires leave no direct evidence of historical frequency, such as tree scars [99]. Our general understanding comes from studies of plant community ecology and physiology of individual plant species along with historical accounts. Scientific research has provided indirect evidence generating several arguments to support and contradict occurrence of fire as a common component of desert grasslands.

Fires in desert grasslands were stand replacing and probably frequent. Several researchers suggest a fire frequency of 7 to 10 years for desert grasslands [13,99]. Fires in desert grasslands of the Chihuahuan Desert were probably less frequent than those of the Sonoran Desert [1]. Many researchers view fire as a necessary component to maintain desert grasslands, mainly due to the current level of invasion by woody species in the absence of fire. It is hypothesized that shrubs in desert grasslands would not have achieved the current level of coverage if stand-replacement fires had occurred at regular intervals [99]. Although fires may kill some grass plants and weaken others, establishment of shrub seedlings requires several more years than establishment of grasses [9]. Grassland fires in deserts are usually low-severity and rapid. With perennial grasses, fires generally remove only a single year's growth without burning deep into root crowns, enabling grasses to sprout [51]. Most desert shrubs with perennating buds on the root crown cannot sprout until a 0.4-inch (1 cm) diameter is achieved, and most shrubs require several growing seasons before fruiting [38].

The desert grassland ecosystem provides all the cues necessary for fire. Annual dry lightning storms mark the beginning of the southwestern rains, which take place late June or early July [99]. Lightning and the dry fine fuels generated by the hot dry periods of desert grasslands provide all the components for ignition and spread. When cured and dried, desert grassland vegetation provides adequate fuels for ignition. Once ignited, plant density is the limiting factor for fire spread in the desert grasslands. The amount of fuel varies between desert grassland sites. Annual productivity can vary from almost nothing to 1,000 lbs/acre. If sparse fuels are present, light winds may carry desert grassland fires [9,13]. Grazing may reduce fuels to the point where fire will no longer carry [9]. The Appleton-Whittell research sanctuary, a 7,800-acre (3,160 ha) semiarid grassland preserve in southeastern Arizona, experiences frequent wildfires associated with fuel accumulations resulting from domestic livestock exclusion [37].

The following table provides some fire regime intervals for communities in which galleta occurs:

Community or Ecosystem	Dominant Species	Fire Return Interval Range (years)
bluestem prairie	Andropogon gerardii var. gerardii-Schizachyrium scoparium	< 10
bluestem-Sacahuista prairie	Andropogon littoralis-Spartina spartinae	< 10
sagebrush steppe	Artemisia tridentata/Pseudoroegneria spicata	20-70 [13]
basin big sagebrush	Artemisia tridentata var. tridentata	12-43 [77]
mountain big sagebrush	Artemisia tridentata var. vaseyana	20-60 [4,14]
Wyoming big sagebrush	Artemisia tridentata var. wyomingensis	10-70 (40)** [89,102]
saltbush-greasewood	Atriplex confertifolia-Sarcobatus vermiculatus	< 35 to < 100
desert grasslands	Bouteloua eriopoda and/or Pleuraphis mutica	5-100
plains grasslands	Bouteloua spp.	< 35
blue grama-needle-and-thread grass-western wheatgrass	Bouteloua gracilis-Hesperostipa comata-Pascopyrum smithii	< 35
grama-galleta steppe	Bouteloua gracilis-Pleuraphis jamesii	< 35 to < 100
blue grama-tobosa prairie	Bouteloua gracilis-Pleuraphis mutica	< 35 to < 100
blackbrush	Coleogyne ramosissima	< 35 to < 100
galleta-threeawn shrubsteppe	Pleuraphis jamesii-Aristida purpurea	< 35 to < 100
little bluestem-grama prairie	Schizachyrium scoparium-Bouteloua spp.	< 35 [13]

*fire return interval varies widely; trends in variation are noted in the species summary
**(mean)

POSTFIRE REGENERATION STRATEGY [83]:

Rhizomatous, rhizome in soil

Related categories for SPECIES: Pleuraphis jamesii | Galleta