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

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kuf I: HHtt 1 I H 1 MHNH ENtN I, 1N&. F'HUNt Nu. . .50 .5 ryd `:+ r 1 r Jul. UJ 20 0:2: 2E1PM F4/9 strategy, but after 50 years, unneeded spoils in southeastern Montana equaled native rangeland in species richness (Sindelar 1978). Where the previous plant community was nonweedy, we suggest that the upper lift of direct - hauled soil should ccntain adequate propagules. Portions of fields need not be seeded, or seeded only with weak competitors. Possibly this could Lead to serious erosion problems in the early phase of stand establishment. 'Therefore, such a strategy should be restricted to small patches or gentle slopes,. Productivity and Diversity Many species are associated with particular microhabitats, and others seem to be found, for whatever reason, where plant abundance is low. In their quest for models that would predict changes in diversity resulting from man's activities, Pert and others (1983) summarized: "The pattern that emerges is one of an optimum fertility for high species density that is well below optimum fertility for pp roduction." In the semiarid West, high productivtty•results in litter accumulation, which can further hirider diversity. Building on the works of Crrime (1973), AI -Mufti and others (1977) investigated species density as it relates to peak standing crop plus litter. They related highest species density to the range where stress is not overwhelming, but at the same time productive potential does not favor a few competitive species at the expense of a rich flora. Although th, scale probably is relative to the area and climate under consideration, the range from 350 -750 g/m was associated with highest diversity. We investigated this relationship using data from an unpublished preaiine vegetation inventory at the Spring Creek Mine and revegetation monitoring at the Rosebud Mule, both in southeastern Montana, In Figure I, seminatural vegetation types are positioned along a productivity gradient_ The trend we see is that diversity decreases with increasing productivity. (Species density is law at 500 kg/ha because plant occurrence is so limited) Alas, measurements from revegetated pastures at Colstrip revealed a more complex and weaker relationship (Figure 1). While species richness generally declines with increasing productivity, species density and Sharman value show no particular relationship. This is just one more example of lack of organization in revegetation. We are curious whether diversity is higher at mines where soils and climate limit productivity to the premine level. Since the habitats of reclaimed fields are not very different, species composition is largely implicated in the differences in productivity revealed in Figure 1, right column. We are convinced that there is a tradeoff between diversity and productivity. hi general, increasing habitat diversity will require reducing the productive capacity of portions of the landscape. These less productive or "stressed" landscape components will be more vulnerable to erosion and more affected by disturbance than more productive portions. Only when the competitive advantage of aggressive cool- season grasses is nullified by creating habitats to which they are ill - suited can the more difficult to establish species situate and perpetuate. Among this group of difficult to establish species are.shrubs and trees that will add greatly to physiognomic and local landscape diversity_ Productivity is rightly a requirement of revegetation. It is one of the few functional attributes of plant communities commonly measured and may be thought of as an index of resource availability (site quality) and how efficiently plants use those resources. At the same time, enhanced productivity can lead to competitive dominance. We suggest a level of productivity not much higher than the reference area or technical standards based on a mosaic of hi and low- productivity sites if diversity is an important goal. 3.52