2002-07-08_GENERAL DOCUMENTS - M2002004 (2)

Home Browse Search

1 KUI'1 HHG 1 1 H 1 IiHNHUtM N 1, 1 NL. rHUNt NU. : Dui rt.d J r1 r ,: u 1 . U.■ '200 02: 30PM PE /9 but it does not act as a barrier to root penetration or to water movement as do the original sedimentary rocks. As far as the plants are concerned, they're growing in deep soil. Parent material. will dictate many soil properties, e.g., the Fort Union formation ensures that reclaimed soils will be highly calcareous and largely free of soluble salt or soditun limitations. Sod textures will be mainly toxins, sandy loairls, and clay loarns with some heavier textures. None of these factors can be changed by reclamation strategy. • Lastly, we cannot change the erosional enviranment. Native landscapes in the unglaciated plains of southeastern Montana were formed over tens of thousands of years by relentless erosional forces in a semiarid eavironment_ Those same forte are at work in reclaimed fields today. Reclaimed Landscapes are unstable. They will change with time; we can only hope to control the rate. Some of the environmental variables responsible for diverse habitats in presnine landscapes are held constant by the very process of reclamation; others are prohibited by regulation. At least to some degree, reclamators can control these factors: landform, slope, and soil replacement depths -- both topsoil and total soil (topsoil + subsoil). This limited set of variables can be increased Only through expending prohibitive amounts of tune and money. To make the most of these factors -- to turn them into opportunities -- the reclamator needs flexibility. Plant Concerns: Habitat, Niche. Diversity, and Organization When we examine a species list for an area where we are familiar with the flora many of the perennial species bring to mind some habitat factor(s), such as a special soil, topographic position, or microliabitat. These simple associations belie the complex array of factors that, in spun, define a species habitat. By habitat we mean primarily physical environment. Many habitat factors can be conceived as linear gradients, and each species or ecotype has ranges of tolerance as well as optima for each factor. In a given landscape, we can sometimes conceptually order habitats in a way that makes sense as a gradient, and plot a species' abundance along this gradient. Temporal changes may obscure important envirorunental factors as they relate to plant phonology. By the principles of Gause, coexisting species evolve toward different habitats, which has the effect of limiting competition. In successful reclamation, planted species soon fill the habitats; cover and.production exceed premine conditions. For new species to become established, habitat must be partitioned in the process of habitat selection -- a slow process due to the life spans of many perennials and what appears to be community resistance to invasion. Competition may compress a realized niche considerably, or it may barely affect it (Bazzaz and Sultan 1987). Removal of some limiting factor can allow arriving species to colonize within the community, at least temporarily At Colstrip, for example, Sindelar and Platereburg (1980) observed that an especially moist year resulted in the appearance of many new species at most study sites. The following year was droughty and species numbers declined. The trend is for the actual range of habitats occupied by a species in a community to narrow through tune, which brings us to the realized ruche of a species population. On a gevest site, in a given community, the actual niche or position of a species population is determined by processes such as predation and competition in conjunction with plant strategies In Whittake's (1972) view and ours, the community may be conceived as 'a system of variously interacting, niche-differentiated species populations." Diversity is greater where realized niches are narrow. Our goal should be creating diverse habitats, providing propagules of specialized species, and limiting competitive dominance, all of which should promote niche differentiation. So far, useful relationships between revegetation diversity and some reclamation practices and field attributes remain elusive. (See Prodgers, these proceedings.) For reasons soon explained, we urge the greatest caution in extrapolating diversity relationships from seminatural vegetation (sensrs Kuchler 1967, p. 24) to revegetated communities_ 148