Controlled grazing studies on Molinia grassland: effects of different seasonal patterns and levels of defoliation on Molinia growth and responses of swards to controlled grazing by cattle

Maintain upland heath/moorland

A replicated, controlled study of two hill pastures in Scotland (Grant et al. 1996a) found that repeated cutting within a growing season over three successive years resulted in decreased purple moor grass Molinia caerulea leaf production, tussock size and productivity. Frequency and severity of defoliation were more important than timing in their effects. Weights of purple moor grass clippings from cut tussocks declined each year in treatments that involved repeated within-season cutting. Three years of repeated light cutting (33% leaf blade length removed each June, July and August), compared with uncut controls, reduced leaf production (numbers and size) in the fourth uncut growing season by 40%. Repeated heavy cutting (66% leaf blade removal) reduced production by 78%. Single annual cuts only reduced leaf production at 66% leaf blade removal when the cut took place late in the season (rather than in June or July). There were 4-6 replicates of each treatment at each site. Clipped vegetation at each cut was dried and weighed. Harvested tussocks were dissected to determine numbers of live vegetative, flowering and dead tillers.