FIRE EFFECTS
SPECIES: Scirpus acutus | Hardstem Bulrush 



IMMEDIATE FIRE EFFECT ON PLANT : 
Hardstem bulrush is top-killed or killed by most fires [7,65,88].  


DISCUSSION AND QUALIFICATION OF FIRE EFFECT : 
NO-ENTRY


PLANT RESPONSE TO FIRE : 
Hardstem bulrush sprouts from rhizomes following fire [65,66], and
probably sprouts from the root crown as well.  It establishes from
buried seed or seed dispersed onto burned sites [29,34,55,65].
Inflorescence production may increase for at least 1 postfire year [88].
Fire increases protein content in sprouting hardstem bulrush [67].

At the Bear River Migratory Bird Refuge, Utah, herons and egrets nest
almost exclusively in dead hardstem bulrush stands.  Green and dead stem
densities (mean +/- SE) were studied on a March 1981 prescribed burn
site and on unburned nesting colony sites. The results are as follows
[7]:

site                              green stems/sq m      dead stems/sq m

Burn, postfire month 4              38.3 +/- 3.2              0              
Burn, postfire month 16             52.6 +/- 2.5         34.7 +/- 2.7
Great blue heron colony             43.5 +/- 4.1         59.0 +/- 6.5
Black-crowned night heron colony    41.7 +/- 3.2         65.2 +/- 4.9
Snowy egret colonies                59.4 +/- 5.          80.2 +/- 7.2



DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : 
NO-ENTRY


FIRE MANAGEMENT CONSIDERATIONS : 
Burning dead hardstem bulrush stands may have a negative effect on
breeding herons and egrets [7].  Herons and egrets use dead hardstem
bulrush stems as nesting material.  On the Bear River Migratory Bird
Refuge, fire eliminated all dead hardstem bulrush stems.  Live stems may
be utilized later in the nesting season.  Herons and egrets have been
reported to abandon traditional colonial nest sites that have been
burned [91]; thus, burning dead stands may have a negative effect on
breeding herons and egrets [7].

Wetland vertebrates may select certain marsh plant species due to
protein increases following fire [66].  

The effects of fire and grazing on wetland plants after drawdowns in
Utah's Great Salt Lake Marsh were studied [65,66,68].  Five acres (2 ha)
were prescribed burned on September 2, 1981, then reflooded 1 week
later.  Data were recorded in areas grazed by waterfowl and muskrats,
and in exclosures protected from grazing.  Mean annual production (g/sq
m/yr) +/- SD of hardstem bulrush (S. acutus and S. validus were both
referred to as S. lacustris) under grazed and burned treatments was
measured from May to August 1982.  Results were as follows [66]:

                    burned             unburned

grazed            915 +/- 366        1084 +/- 495
ungrazed         1559 +/- 811        1556 +/- 684

The effect of prescribed burning on hardstem bulrush standing crop was
minimal.  The total annual production of the hardstem bulrush vegetation
type after fire was not significantly different (P >.10) than the
production of these types in unburned areas.  Grazing, however, had a
significant impact (P <.05) on production in hardstem bulrush stands.
Grazing significantly reduced the total annual production of the
hardstem bulrush type within the burned sites [66,68].  Roots and
rhizome numbers were lower on the burned than unburned units, but
mortality was not great enough to significantly reduce total
productivity [68].

Related categories for Species: Scirpus acutus | Hardstem Bulrush