Cattle Grazing Effects on Phragmites australis in Nebraska

摘要

Phragmites australis (common reed) is one of the most widely distributed flowering plants in North America. The introduced lineage occurs in wetland and riparian areas covering a range of climatic types. In Nebraska, an abundance of livestock could help to reduce P. australis with proper timing and grazing intensities. In 2011, a 3-yr study was initiated to evaluate targeted cattle grazing and herbicide effects and the nutritive value of this species. Treatments included a single application of imazapyr (Habitat (R), BASF Corporation, Research Triangle Park, NC) herbicide applied in the first year, grazing, and a control. Grazing was applied for up to five consecutive days in June and August 2011 and 2012 and in June 2013. Stem density, height, and biomass of P. australis were determined before each grazing period and in 2014. Diet samples were collected from rumenally fistulated steers each grazing period. Imazapyr provided 100% control of P. australis; however, re-establishment began 2 yr posttreatment. Grazing significantly reduced pregrazing P. australis biomass in the second and third growing season (P < 0.05). Stem density and height in the grazed treatment was similar to the control through 2012; however, in 2013 and 2014, control stem density was 1.5 times greater and height was 1.4 times that of the grazed treatment. Crude protein content of diet samples was greater in 2011 (16.8%) compared with 2012 (14.3%, P < 0.05). In vitro dry matter digestibility (IVDMD) of diet samples (45.4%) was not affected by year or month (P > 0.05). The relatively low IVDMD suggests that some form of energy supplementation would be needed to create a better nutritional balance. The cumulative effect of grazing does have the potential to reduce P. australis populations, but other methods would have to be used for greater control and site restoration.