The annual grass Japanese brome Bromus japonicus has become invasive in mixed prairie communities of the Northern Great Plains, USA. Reducing seed production by grazing or cutting can be effective. Grazing may also reduce brome by reducing the amount of litter which acts as a mulch which benefits germination and seedling establishment. The objective of this greenhouse study (undertaken near Miles City, Montana), was to determine growth response of Japanese brome to varying intensities and frequencies of clipping, thus leading to a greater understanding of how defoliation affects the brome life cycle and to guide management of brome-infested grasslands.
Japanese brome seedlings were grown from seed in 30 boxes (10.2 x 32.8 x 73.7 cm deep) in 1991 and 1992, and 45 PVC tubes (80 cm tall x 20 cm diameter) in 1997. Clipping treatments were applied for 65-70 days from 20 June-30 August 1991, 4 May-8 July 1992, and 1 May-8 July 1997. Five treatments were applied: unclipped (controls) and brome plants clipped to 75 mm or 150 mm stubble height either weekly or biweekly.
The response of brome plants was measured by recording tiller numbers, leaf height, and above- and below-ground biomass, measured in 1991, 1992 and 1997.
Just before clipping treatments began, leaf heights averaged 30 cm in 1991 and 1992, and 38 cm in 1997. Tiller numbers averaged 32 per container in 1991, 16 in 1992 and 19 in 1997. Flowering began soon after treatment initiation in 1992 and 1997; 66% of plants flowered within two weeks after clipping began in 1992, and in 1997 80%. Flowering in 1991 was reduced due to lower light levels.
Clipping non-flowering plants in 1991 reduced tiller numbers and leaf heights. Clipping plants with inflorescence stems in 1992 and 1997 increased tiller numbers but reduced leaf heights. The shorter (75 mm) stubble height had less above-ground and total biomass. Higher (weekly) clipping frequency did not generally affect total biomass compared to biweekly clipping. Some flowering occurred even under the most severe treatment, i.e. clipped weekly to 75 mm.
If using or referring to this published study, please read and quote the original paper, this can be viewed at: https://www.uair.arizona.edu/holdings/journal/issue?r=http://jrm.library.arizona.edu/Volume52/Number4/