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Seeding significantly increased total plant cover 47 percent of the time by the end of the first growing season after fire (table 19). Forty-two percent of seeded sites had at least 30 percent cover, compared to 26 percent of unaeeded. Only 26 percent of seeded sites had at least 60 percent cover versus 10.5 percent of unaeeded. Using vegetation cover as an indicator, therefore, the probability of seeding providing effec- tive watershed protection by the end of the first growing season was just 26 percent, but that was more than twice the probability that an untreated site would be stable. Erosion waa decreased by seeding in only one out of eight first-year studies (12.5 percent). Erosion mea- surements have high variability, and several of the studies showed a trend toward lower sediment move- ment onseeded plots that was not statistically signifi- cant (e.g., Amaranthua 1989, Wohlgemuth and others 1998). The low occurrence of erosion effects is not surprising, however, considering that much of the sediment movement occurs before plant cover is eatab- liahed. Krammea (1960), in southern California, found thetas much ae 90 percent offirsbyear poatfire hillalope sediment movement can occur as dry ravel before the first germination-stimulating rains even occur. Amaranthua (1989) measured moat first-year sedi- ment movement on his Oregon study site during sev- eral storms in December, before the seeded ryegrasa had produced much cover. In the second year after fire, seeded sites had greater total cover (plant and litter) than unaeeded 42 percent of the time (table 19). Half of the studies measured erosion, which was significantly lower on seeded sites 22 percent of the time. Greater cover, therefore, did not always produce leas erosion. The proportion of sites with at least 30 percent cover was 78 percent and 67 percent of seeded and unaeeded plots, respectively. More than half (56 percent) of all seeded sites were essentially stabilized (at least 60 percent cover), com- pared to only 17 percent of unaeeded sites. Thus seeded slopes were three times more likely to be stable after 2 years than unaeeded elopes, though seeding still had only a 56 percent probability of "success" if success means "effective° (60 percent) cover. Published reports from chaparral and conifer sites differed somewhat in response to seeding (table 19). Seeding was less likely to increase cover the first year on chaparral sites than conifer sites. Half of both seeded and unaeeded chaparral sites had at least partially effective cover after 1 year, compared to only 33 percent of seeded conifer sites and none of the unaeeded. However, the only study reporting less erosion on seeded plots the first year after fire was from a chaparral site seeded with annual ryegrass (Gautier 1983). The same trend was evident in studies reporting second-year results (table 19). The study sites in these publications varied widely in soil type, percent slope (table 6, 7), annual precipi- tation, rainfall pattern, and prefire plant commu- nity, as well as seeding mix, so that lumping them together masks important factors affecting cover development and erosion. The total cover value tal- lied in the published studies sometimes included litter, sometimes not; thus, the number of partially and effectively stabilized sites in the second year could be underestimated. We made several generalizations from this tabula- tion. First, plant cover developed relatively rapidly on the chaparral sites examined, so that seeding was less likely to make a difference in total cover in chaparral than on conifer sites. Second, most of the studied chaparral sites were seeded with annual ryegrasa, while the conifer sites tended to be treated with a mixture of perennial pasture grasses, and increased cover due to seeding was more likely to show up in the first year on chaparral sites and in the second year on conifer sites. Third, even if treatment "success" is defined as at least 60 percent total cover at the end of the growing season, rather than as an actual mea- auredreduction in aedimentmovement, seeding had a low probability of success during the first year after fire, when most of the erosion occurs (Robichaud and Brown 1999, Wells 1981), and continued to have a low probability of success on conifer sites in the second year. On the basis of these published results, Burned Area Reports that project 60 to 80 percent first-year success for seeding operations are greatly exaggerat- ing the potential benefits of treatment. A similar tabulation was made from quantitative monitoring reports, although moat of them did not directly compare seeded and unaeeded plots (table 20). Where they were directly compared, seeded plots had greater cover than unaeeded plots 64 percent of the time at the end of the first growing season after fire, though the differences were not tented for statistical significance (table 14). A higher proportion of first- year monitoring studies, compared to published stud- ies, showed apparent reductions in erosion (43 per- cent) aswell, although, again, differences in sediment production were not analyzed statistically. Some of the comparisons involved only one or two monitoring points per treatment. Seeded plots were more likely to have at least 30 percent cover after one growing season in the monitoring studies than in the published studies (74 percent vs 42 percent), possibly because more of them reported on sites seeded with quick- growing cereal grains or annual ryegrass rather than perennial pasture grasses. The probability of finding "effective" (at least 60 percent) cover at the end of the first growing season waa only slightly greater (35 per- cent) than in the published studies. USDA Forest Service Gen. Tech. Rep. RMRS-GTRE3. 2000 49