Ecology of Chrysopogon aucheri and Cymbopogon jwarancusa III. Morphology and Defoliation Response
Ecology of Chrysopogon aucheri and Cymbopogon jwarancusa III. Morphology and Defoliation Response
Mohammad Saleem and C. A. Call
ABSTRACT
Little is known about the defoliation responses of the palatable grass Chrysopogon aucheri (Boiss.) Stapf. and the co-occurring unpalatable grass. Chymbopogon jwarancusa (Jones) Schult., under managed and unmanaged conditions on Baluchistan rangelands. Both species were grown in monoculture and in a 50:50 mixture in an 11-month (44-week) greenhouse study. Defoliation treatments were implemented when plants were 32 weeks old; and consisted of: equally clipping (3-cm stubble height) plants in monoculture and mixture zero, one, two or three times at 4-week intervals (32, 36. and 40 weeks after emergence), and clipping (3-cm stubble height) one species in mixture zero, one, two or three times at 4-week intervals (32, 36 and 40 weeks after emergence) without clipping the associated species. The final harvest of all plants in every defoliation treatment occurred at 44 weeks after emergence. Response to defoliation was measured in terms off leaf and tiller development and shoot and root biomass production. Plants of both species had similar patterns of leaf and tiller development until defoliation treatments .were implemented. Cymbopogon jwarancusa produced more tillers per plant than Chrysopogon aucheri when both species were equally defoliated one two, or three times in monoculture and equally defoliated three times in mixture. Most Chrysopogon aucheri plants developed inflorescences by 32 weeks after emergence, whereas all Cymbopogon jwarancusa plants remained vegetative throughout the experiment. Chrysopogon aucheri had greater shoot and root biomass than Cymbopogon jwarancusa in mixture when plants were equally defoliated zero, one or two times, whereas shoot and root biomass were comparable under the same defoliation regimes in monoculture, and when equally defoliated three times in monoculture or mixture. When one species was defoliated zero, one two, or three times and the associated species was not defoliated, shoot biomass was comparable for both species while Chrysopogon aucheri had greater root biomass than Cymbopogon jwarancusa. Chrysopogon aucheri had similar or higher crude protein content and % in vitro digestible dry matter when compared to Cymbopogon jwarancusa. Chrysopogon aucheri may not decrease in mixed Chrysopogon - Cymbopogon communities if the frequency and intensity of defoliation are controlled more closely as in this experiment.
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June 1993
Vol. 43, Iss. 2
