VALUE AND USE
SPECIES: Aristida purpurea | Purple Threeawn 



WOOD PRODUCTS VALUE : 
NO-ENTRY


IMPORTANCE TO LIVESTOCK AND WILDLIFE : 
Livestock:  In most regions, forage value of purple threeawn is only
poor to fair [11,40,56].  The long awns irritate and cause abscesses in
the mouths and nostrils of grazing animals.  Livestock generally avoid
purple threeawn for most of the year when other forage is available.  In
areas where purple threeawn is abundant, livestock may make moderate use
of it in spring before awns develop and in fall and winter after seed
shatter [56].  In some areas of the southern Great Plains, cattle prefer
purple threeawn in winter because it is one of few plants that remain
green all season [15].

Small mammals:  In a Colorado study, purple threeawn was one of a
variety of grass species grazed by white-tailed jackrabbit [12].

Black-tailed prairie dog graze purple threeawn lightly [18] but do not
prefer it [7,15].  Purple threeawn is often one of the few grasses
remaining in areas severely disturbed by prairie dogs [15].


PALATABILITY : 
Purple threeawn is generally unpalatable due to its spike-like awns,
which can injure grazing animals.  It may be grazed to some extent
before seedheads are produced and after seed shatter [15,25].  Livestock
may graze new purple threeawn growth after fire [15].  Dyksterhuis [13]
reported that on post oak-blackjack oak (Quercus stellata-Q.
marilandica)/buffalograss communities in the Cross Timbers region of
Texas, cattle grazed purple threeawn only in December and January.
However, cattle on desert grassland of the Jornada Experimental Range,
New Mexico, grazed Fendler threeawn in all months of the year except
January and February [42].

Wildlife:  Bison on blue grama-buffalograss prairie in northeastern
Colorado commonly grazed Fendler threeawn in March and August.  In June,
Fendler threeawn was a preferred grass [44].  

The degree of use shown by livestock and wildlife species for
purple threeawn is rated as follows [11]:

                       CO        MT         ND      UT        WY
 
Cattle                poor    poor/fair    ----    fair    poor/fair
Sheep                 poor    poor/fair    ----    fair      fair
Horses                poor      poor       ----    fair    poor/fair
Pronghorn             ----      ----       poor    fair      ----
Elk                   ----      fair       ----    poor      ----
Mule deer             ----      fair       poor    poor      ----
White-tailed deer     ----      fair       poor    ----      ----   
Small mammals         ----      ----       ----    fair      ----
Small nongame birds   ----      ----       ----    fair      ----
Upland game birds     ----      ----       ----    fair      ----
Waterfowl             ----      ----       ----    poor      ----


NUTRITIONAL VALUE : 
Purple threeawn is rated poor to fair in energy content and poor in
protein value [11].  Percent digestible protein of fresh purple threeawn
(Aristida purpurea var. purpurea) and Fendler's threeawn collected at
several locations throughout the western United States was as follows
[41]:
______________________________________________________________________
|                  Cattle     Goats     Horses     Rabbits     Sheep |   |                  ------     -----     ------     -------     ------|  
|purple threeawn    3.7        2.9        3.3        3.9        3.3  |
|Fendler threeawn   2.7        1.8        2.3        3.0        2.2  |
|____________________________________________________________________|


Nutritional content of Fendler threeawn collected in on the Jornada
Experimental Range, New Mexico, was [42]:
___________________________________________________________________________
|                        Dry Matter Composition (%)                       |
|_________________________________________________________________________|
|                                       Ether     A-D     A-D             |
|Stage of Maturity   Month    Protein  extract   fiber  lignin  ash    Ca | 
|_________________________________________________________________________|
|early leaf          April      8.2      1.1     48.7    6.5   14.0   0.56|
|mature               May       ---      2.4     53.7    6.4   12.8   ----|
|mature            June-July    7.0      1.1     53.1    6.6    8.0   0.26|
|mature            Aug.-Sept.  10.4      2.8     42.4    5.5    8.8   0.49| 
|overripe             Oct.      6.9      2.1     48.0    6.5   15.4   0.51|
|dormant              Nov.      5.0      1.4     53.7    7.6   10.6   0.36|
|dormant              Dec.      3.7      1.4     53.1    7.0   12.4   0.48|
|_________________________________________________________________________|
A-D = acid-detergent

Nutritional content of Wright's threeawn from the Edwards Plateau of
Texas was as follows [29]:
_____________________________________________________________________________
|               |               |_______________Composition (%)_____________|
|               |Collection Date|Water   Ash   Cell wall   P   Protein   DOM|
|_______________|_______________|___________________________________________|
|leaves              4/13/73       32     11       71     0.08    7       36|
|old and new growth  5/24/73       35      9       74     0.08    7       42|
|leaves and stems    6/28/73       45      6       77     0.10    8       48|
|total               7/27/73       42      7       74     0.09    7       46|
|leaves              8/30/73       23      7       74     0.05    5       39|
|leaves and stems   10/03/73       38      5       79     0.07    6       43|
|___________________________________________________________________________|
P = phosphorus; DOM = digestible organic matter


COVER VALUE : 
The value of purple threeawn cover for wildlife was been rated as
follows [9]:

                        CO       ND       UT

Pronghorn              ----     fair     poor
Elk                    ----     ----     poor
Mule deer              ----     fair     poor
White-tailed deer      ----     poor     ----
Small mammals          poor     ----     fair
Small nongame birds    poor     ----     fair
Upland game birds      poor     ----     fair
Waterfowl              ----     ----     poor


VALUE FOR REHABILITATION OF DISTURBED SITES : 
NO-ENTRY


OTHER USES AND VALUES : 
NO-ENTRY


MANAGEMENT CONSIDERATIONS : 
Purple threeawn tends to increase with grazing.  In east-central Texas,
mean (+/- SE) purple threeawn percent cover on long-term protected sites
(39 years of cattle exclusion) and long-term grazed sites (30 years of
continuous heavy cattle grazing) was as follows [2]:
                  ______________________________________
                  |Long-term protected|Long-term grazed|
                  |___________________|________________|
                  |    0 (+/- 0.0)    |  17 (+/- 1.6)  |
                  |___________________|________________|

Threeawns (Aristida spp.) may remain important constituents of some
rangelands even after grazing is stopped or reduced.  On grama
(Bouteloua spp.) grassland on dry mesas of the Santa Rita Experimental
Range, southern Arizona, cover of blue threeawn and spidergrass (A.
ternipes var. hamulosa) on sites ungrazed for 25 years was about half
that of blue threeawn and spidergrass cover on sites in various stages
of grazing recovery.  Grama spp. cover was 36 percent on sites protected
for 25 years, and threeawn cover was 14 percent.  Canfield [4] suggested
that on dry mesas of Arizona, a grama-threeawn mixture may be indicative
of rangeland in good condition.

Awns of purple threeawn often catch in the fleece or hair of livestock,
causing injury and lowering the value of the fleece or hide [50,56].

Related categories for Species: Aristida purpurea | Purple Threeawn