FIRE CASE STUDIES
SPECIES: Scirpus acutus | Hardstem Bulrush 



CASE NAME : 
Fire effects on wetland vegetation/Malheur NWR, Oregon


REFERENCE : 
Young, R. P. 1986 [88]


SEASON/SEVERITY CLASSIFICATION : 
late fall/moderate-high severity
early spring/moderate-high severity


STUDY LOCATION : 
The study was located in Harney Basin in the Malheur National Wildlife
Refuge (NWR), Oregon.  


PREFIRE VEGETATIVE COMMUNITY : 
A monotypic, palustrine hardstem bulrush (Scirpus acutus) wetland
community type occurs throughout the Malheur NWR.  Standing dead fuel
was assessed 2 to 10 days preceding a fire.  A series of quadrats were
located throughout the cover type; on the quadrats, vegetation was
harvested to ground level and collected for oven drying and weighing.


TARGET SPECIES PHENOLOGICAL STATE : 
All prescribed fires were conducted during periods of vegetative
dormancy.  


SITE DESCRIPTION : 
The study site was located on a flat to gently rolling landscape at
4,015 to 4,225 feet (1,250-1,280 m) elevation.  Harney Basin is
characterized by a semiarid climate and moderate to cold temperatures.
Annual precipitation averages 10 to 12 inches (250-300 mm), but extremes
of 4 inches (100 mm) and 20 inches (500 mm) have been recorded.  The
bulk of precipitation occurs in winter and spring, whereas summers are
typically dry.  The riverine and palustrine systems occupy the
bottomlands draining into Malheur and Harney lakes.  These are typically
long, narrow wetland zones composed of a continuum of ponds, sloughs,
marshes, and wet meadows.
   


FIRE DESCRIPTION : 
Hardstem bulrush prescribed burn sites were at least 5 acres (2 ha) and
were located in areas that would facilitate safe and efficient
controlled burning.  Prefire fuels and fire weather conditions at the
Malheur NWR were as follows:

fire dates                      9 December 1980          7 April 1981
prefire fuel load (g/sq m)
  mean                            1,817                    1,707
  range                           1,062-2,402              887-2,208   
fuel height (cm)                  184                      122
litter depth (cm)                 74                       66
fuel moisture (%)                 4.6                      5.8
temperature (C)                   3-5                      4-9
relative humidity (%)             27-34                    31-35
wind speed (km/h)                 2-16                     6-10

Fire behavior and effects on fuels were as follows:

fire dates                          9 Dec 1980           7 April 1981
rate of spread (m/min) 
  headfire                            5-30                 20-25
  backfire                            1-1.5                1-2
flame length (m)
  headfire                            3-10                 3-4
  backfire                            1-2                  1-2
postfire residual fuels (g/sq m)
  mean                                309                  154
  range                               27-568               12-328
reduction (%)                         83                   91

Rate of spread was strongly influenced by wind speed.  


FIRE EFFECTS ON TARGET SPECIES : 
Regenerative tissues arising form rhizomes were protected from heat
injury under conditions of dormant season, surface fires.  Winter and
spring burning of hardstem bulrush increased reproduction for at least 1
year.  Inflorescence production increased by 25 percent for at least 1
year.  Burning increased aboveground standing crop and shoot densities
for 2 years.  Mean shoot weight decreased slightly.  


FIRE MANAGEMENT IMPLICATIONS : 
Prescribed fires reduce the amount of litter in hardstem bulrush stands,
which may increase hardstem bulrush productivity.  

Related categories for Species: Scirpus acutus | Hardstem Bulrush