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Individual study: The effect of cultivation treatments on the establishment of three native grass species on a roadside verge at the Disney Wilderness Preserve, Florida, USA

Published source details

Jenkins A.M., Gordon D.R. & Renda M.T. (2004) Native Alternatives for non-native turfgrasses in Central Florida: Germination and responses to cultural treatments. Restoration Ecology, 12, 190-199

Summary

Non-native species often dominate buffer areas adjacent to natural and restoration sites to provide soil stabilization and vegetative cover. In the southeastern United States, species commonly used for this purpose include bahiagrass Paspalum notatum and a few other non-natives. In this region, in longleaf pine flatwood habitat, composition of groundcover is dominated by perennial graminoids. Buffer zones however generally comprise sward dominated by non-native grass that can escape into natural areas and reduce establishment and survival of native species. Identification of suitable native species for use in buffer zones is therefore needed. This investigated the potential of five native species (four native to Florida longleaf pine flatwoods and one native to the adjacent wetland communities) for use in buffer zones. Two studies were undertaken, and one conducted on a roadside verge (summarised here) and one in former bahiagrass pasture (see Case 551).

Study site: The grass planting trials were conducted at the Disney Wilderness Preserve, Polk and Osceola Counties, Florida, USA. The 4,797 ha pine flatwoods preserve (with associated wetlands and scrub communities) is owned and managed by The Nature Conservancy. A new roadside within the preserve was used to test the three grass native species that formed the best cover in an earlier pasture experiment (see Case 551): Eragrostis refracta, Eustachys petraea and knotgrass Paspalum distichum. As in the pasture trials, knotgrass sprigs were planted, and seed of the other two species sown.

Seed collection: Seed was hand collected in November 1999. E.refracta seed was rapidly removed from stems using a Viking Hammermill (Horvick Manufacturing, Fargo, ND, U.S.A.) at the USDA Plant Materials Center (Brooksville, Florida). seed was manually removed from the stalks.

Experimental design: Non-native bahiagrass Paspalum notatum, was first removed from a 35 × 4 m area on the road shoulder in August 1999 using two applications of glyphosate herbicide and then multiple disking over a 4-month period. The site was raked and rolled before sowing. Three 11 × 2 m blocks were established parallel to the road. Each contained three 3 × 2 m plots separated by a 1 m buffer. Species were randomly assigned for planting in monoculture into one plot per block.

Planting: Seeded plots were sown on 9 December 1999 to mimic the timing of natural seed fall. Each plot received 20.1 g seed (equivalent of 33.65 kg per hectare). The sowing rate was increased in response to low germination and slow establishment in the pasture experiment. Seed was hand sown and rolled (to improve soil contact, pine straw was spread 2 cm thick over the surface and rolled again to compact it. Thin plastic netting (2.54 cm mesh) was overlain and stapled into the soil to prevent the seed and straw from being blown off. The netting was removed as soon as seedlings began germinating.

Knotgrass sprigs (as seed was unavialable) were cut into 10 cm lengths with at least three nodes, and stored in water for 24–48 hr prior to planting and planted (as in the pasture experiment) ensuring at least half of each was buried horizontally under the soil to increase node-soil contact. These plots were initially irrigated as needed with 77 mm of water every third day for 2 months to supplement rainfall.

Monitoring: The roadside plots were monitored monthly for the first 6 months, then bimonthly until February 2001. Plant cover was estimated using the point intercept method. Points were dropped every 20 cm along two randomly placed nonpermanent transects within each plot. Cover was estimated within three cover categories: sown or planted species, other species, and bare soil or litter.

Knotgrass: Cover of sprigged knotgrass was consistent (around 45%) from May to October 2000 and then decreased steadily in the final winter months of monitoring (around 5%) in February 2001. Other species cover within knotgrass plots increased until June 2000 (to around 55%) and decreased each subsequent month (to around 28% in February 2001).

Sown grasses: Eustachys petraea cover increased each month until August 2000, peaking at approximately 85%, but subsequently decreasing to 40% by February 2001. Weed cover decreased over time in these plots from a high of 41% (in March 2000) to around 14% (February 2001).

Eragrostis refracta showed no germination until August. Its cover increased from 2 to 15% from August to October 2000 and then decreased to around 1% cover by February 2001. Weeds within these plots increased until August 2000 (around 88%) and then decreased to a low in December 2000 (around 28%), before recovering slightly at the end of the study period in February 2001 (around 36%).

Conclusions: Both E.petraea and P.distichum developed more than 45% cover on the roadside and might therefore be considered appropriate species to sow in such newly created roadside sites rather than using non-native grasses. Establishment of the native grasses from seed or sprigs was significantly enhanced when site preparation effectively reduced the seedbank of other species present in the soil.


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