HYDRO20750 - Laserfiche WebLink

Home Browse Search

Research, monitoring reports, and interview com- ments all suggest that "successful" grass establish- ment displaces some native plant regeneration. This was the goal of past range "reseeding" projects- producinguseful livestock and wildlife forage on land that would not contain harveetable timber for decades and would otherwise produce nothing but "weedy"- and aggressive, persistent grass species were deliber- ately chosen for seeding (Christ 1934, Evanko 1955, Friedrich 1947, McClure 1956, Stewart 1973). Sup- preaeion ofnativeplant regeneration could potentially reduce browse species for wildlife, reduce watershed protection in chaparral, and limit the seed bank con- tributions of annual and short-lived perennial "fire- followers" in chaparral and Southwestern ecosys- tems (Conard and others 1995, Keeler-Wolf 1995, Keeley and others 1981, Loftin and others 1998). There ie no published research that quantifies the long-term impacts of poatfire seeding on native plants, but one monitoring observed that weeping lovegrasa (Eragrostis curwia) in the Southwest can effectively suppress native vegetation for years (Loftin and oth- ers 1998). In our interviews, forest silviculturiats expressed major concerns about the impacts of grass seeding on conifer regeneration. The dilemma between erosion reduction and conifergrowth is well recognized: "Since granitica are inherently good tree-growing sites, as well as being extremely erodible when burned, the choice between immediate reforestation and long- termproductivity can be a difficult one" (Van de Water 1998, p. 28). Better understanding of the impacts of fire and erosion on soil productivity would help ad- dresathis problem. Current USDA Forest Service guidelines promote the use of native species for revegetation projects wherever practical. Interviewees commented that native grasses are expensive and not widely available inthe quantitiesnecessaryfor postfire seeding projects, and developing seed sources that can provide a range oflocally adapted genotypes is difficult (Van de Water 1998). In addition, well-adapted native perennial grasses could provide as much or more competition with conifers as the non-native species currently in use. For example, the native Southwestern grass Ari- zona fescue (Festuca arizonica) greatly reduced the growth of conifer seedlings (Pearson 1942, Rietveld 1975). One BAER team included the coat of using herbicide for seeded grass control in BAER calcula- tions and, as a result, decided against using awell- adapted native grass and chose to seed cereal barley (Hordeum wlgare) instead (Griffith 1998). The barley died out after 1 year except where disturbed by salvage logging (Griffith 1993; tables 14, 15). Seeded grasses can benefit conifer seedlings if they exclude more competitive vegetation, such as shrubs (Amaranthue and others 1993, McDonald 1986). Once conifer seedlings are well established, grass cover is less detrimental to their growth than shrub competition (McDonald and Oliver 1984, McDonald 1986). If grass cover is not too thick, it can potentially benefit tree seedlings. Green (1990) observed over 90 percent survival of Douglaa fir seedlings on a site seeded after fire with cereal rye (Secale cereals). The rye, at a density of 9 plants ft_2 (100 plants m 2), provided shade to the seedlings during the first year after fire. The rye decreased to leas than 3 plants ft-2 (33 plants m 2) the second year and essentially disap- peared in the third. Cereal grains such as barley, cereal rye, oats (Avena sativa), and winter wheat {Tritium aestiwm) appear to show great promise for producing cover that does not persist. Annual ryegrass was expected to behave this way, but it proved persistent beyond a wuple of years in some ecosystems (Barro and Conard 1987, Griffith 1998) and often produces maximum cover the second year after fire, ratherthan the first (Beyera and others 1998; compare Janicki 1989 with Conard and others 1991). A few reports cited initial concerns over the impacts of cereal grains on native regeneration that disappeared after further monitoring (e.g., Callahan and Baker 1997, Hanes and Callahan 1995, 1996, VanZuuk 1997). Somecereal grains mayexhibit allelopathy, inlubitingcompetingplant growth chemi- cally (Went and others 1952), but this has not been investigated under Seld conditions. Clearly more re- search on and monitoring of poatfire cereal grain seeding is needed, especially regarding the impacts on native herbaceous plants and conifer seedlings. In many cases natural regeneration provided as much cover as seeded species during the first years after fire, but good methods for assessing native seed bankviability are lacking (Isle 1998, Loftin and others 1998). One standard teat for seed bank viability only identifies large-seeded species (by sieving them from poatfire soil samples) or those that germinate quickly (7 to 10 daygreenhouae germination test) (Dyer 1995). Species that will proride cover later in the winter or in the aecondgrowingaeason-the same time that seeded grasses provide most of their cover-are not detected by this method if they have tiny seeds or cold require- ments for germination. Better understanding of the natural range of vegetation response to fire would increase our ability to predict whether seeding is really necessary (Loftin and others 1998, Tyrre11981). Several interviewees suggested that more flexibil- ityinchooeing eeedmixeabeallowed inBAERprojecta, including the use of quick-growing annuals for ero- aioncontrol and slower growing native perennials For long-term ecosystem restoration, particularly native range. At present, BAER guidelines stress the use of only proven erosion-control species for emergency USDA Forest Service Gen. Tech. Rep. RMRS-GTR~3. 2000 51