Mechanical Treatments that can be Used in Combination with Prescribed Burning

Mechanical treatments (bedding, root-raking, use of a disc, roller chopping, web plowing etc.), by whatever means, typically produce a wide variety of changes in plant community structure and composition in dry prairie. The use of bedding to reduce or remove competing shrubs and other vegetation, to prepare dry prairie for planting with pine or Eucalyptus monocultures (Moore and Swindel 1981), produces distinct microsites in the form of beds, flats, and furrows (Abrahamson and Harnett 1990). The native intact ground cover characteristic of dry prairie is significantly affected by these microsite alterations. Practices such as root-raking and use of a disc displace surface organic and litter layers and mineral soil, and may potentially eliminate native species, allow for the establishment of numerous weedy species, and significantly alter the native species composition and vegetation structure of dry prairie.

The most frequently employed mechanical treatment on dry prairie is the use of roller chopping to control woody shrub height, in particular excessive growth in saw palmetto (Yarlett 1965). The use of roller chopping on areas of intact, diverse native groundcover vegetation is not recommended and is strongly discouraged.  Double chopping has been reported to almost eliminate wiregrass and saw palmetto (Hilmon et al. 1963). Frequencies of some herbaceous plants and species richness can increase following some types of roller chopping. However, the resulting increase in species richness (= species diversity), primarly from changes in overall species composition and relative abundance, is from an increase in undesirable ruderal weedy species.

Impacts to vegetation from chopping vary widely and are largely dependent upon the method and type of chopping, and the soil and moisture conditions when the chopping is conducted. Studies conducted by Fitzgerald et al. (1995) on formerly fire suppressed dry prairie (12 to 15 years of fire suppression) at Myakka River State Park found that application of fire regardless of season was not significant in reducing woody cover. However, repeated chopping and follow-up burning aided attempts to restore dry prairie in shrub-dominated dry prairie (Fitzgerald et al. 1995, Tanner 1997). Therefore, roller chopping on former fire-suppressed or previously disturbed dry prairie may be a useful restoration tool when used in conjunction with frequent burning (Tanner 1997, Fitzgerald and Tanner 1992). Fitzgerald and Tanner’s (1992) study on formerly fire-suppressed (35 years of fire suppression), overgrown dry prairie found shrub control treatments (roller chopping) had an acute effect on bird abundance and species composition, as they had postulated. They noted that the first birds observed in the chopped plots were prairie bird species (eastern meadowlark, Melospiza georgiana; loggerhead shrikes, Lanius ludovicianus; and grasshopper sparrow) perhaps an early sign of prairie restoration (Fitzgerald and Tanner 1992). Roller chopping is now accepted by many land managers as an effective means to begin restoration of overgrown former prairies and flatwoods (Tanner et al. 1988, Moore 1974). This is particularly true where fire has not been sufficient to control woody shrubs, where chopping can be effective in reducing the height and dominance of woody shrubs (Tanner 1997, Fitzgerald et al. 1995). However, the destructive nature of this technique, even in disturbed prairie, has the potential to cause unforeseen changes in natural processes. If applied during the spring, summer, or early fall, roller chopping may interfere with nesting activities of many prairie bird species. In addition, Bridges (1997) has postulated that roller chopping may have been the cause of significant long-term vegetation composition changes at some dry prairie sites.