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Semolina Year Stems/acre • All Wedge Pas. PECOCO Pas. 1985 378 NA NA 1987 300 NA NA lggg 314 322 NA 1989 288 476 NA 1gg0 281 408 NA 1991 228 288 NA 1gg2 157 344 NA 1993 253 356 295 1994 234 271 NA 1gg5 364 182 NA 1996 209 239 376 1gg7 184 210 NA 1998 257 547 150 1999 381 227 NA 2000 235 393 NA 2001 483 360 215 2002 474 502 627 From this record, it is apparent that there have been fluctuations in density values over the years that have not constituted consistent trends upward or downward. A comparison of these data with climate records (Figures 7a, 8a, and 9a) and records of cover and production (above) suggests that there is an inverse relation between favorable growing conditions and the prevalence of shrubs. When moisture is adequate to allow grasses and other herbaceous species to grow vigorously, the competitive side effects are devastating to shrub numbers. Conversely, when dry times are intense and of sufficiently long duration, the shrub numbers rise. Species Diversity and Composition Relative cover by lifeform (Table 22) is depicted for the various sampled areas in Figure 5. As can be seen, the heavy dominance of woody species that characterizes the reference areas, especially the Mountain Brush reference area is not matched in the reclaimed areas. Older but grazed reclamation (PECOCO Pasture and Wadge Pasture) show an abundance of introduced perennial fortis that is not seen in the younger 1995 and 1998 reclamation. In the older sites at PECOCO and Wadge Pastures, introduced perennial grasses (intermediate wheatgrass and smooth brome) have asserted overwhelming dominance. Younger reclamation sites were sown with native seed mixes and show more even balance between lifeforms. The uninvited presence of introduced perennial grasses on these younger sites is unexplained. 18