MANAGEMENT GUIDELINES AND RECOMMENDATIONS FOR FERN RIDGE RESERVOIR

Transcription

1 MANAGEMENT GUIDELINES AND RECOMMENDATIONS FOR FERN RIDGE RESERVOIR A Component of the Project to Develop Management Guidelines for Native Wetland Communities Submitted to Waterways Experiment Station Army Corps of Engineers Vicksburg, Mississippi Soil Conservation Service Portland, Oregon Submitted by Dr. Mark V. Wilson Dr. Cheryl A. Ingersoll Restoration Ecology and Plant Conservation Biology Cooperative Project, Department of Botany and Plant Pathology Oregon State University December 7, 1993

2 MANAGEMENT GUIDELINES AND RECOMMENDATIONS FOR FERN RIDGE RESERVOIR SUMMARY... 1 INTRODUCTION... 2 METHODS... 3 Meeting... 4 Research review... 4 GOALS, SCOPE, OBJECTIVES, AND CONSTRAINTS... 5 REVIEW OF THE LITERATURE... 7 Description of habitats... 7 Wetland prairie... 7 Upland prairie... 9 Special-status plant species... 9 Information from the literature... 9 Data from field studies Major threats to habitats and species Threats to habitats Threats to species of special concern Information on major pest species Gaps in knowledge BENEFITS OF ADAPTIVE MANAGEMENT EVALUATING MANAGEMENT OPTIONS Management objectives Application of ecological knowledge Evaluation of options RECOMMENDATIONS Recommendation: Seed farming Recommendation: Management of high-quality wetland prairies Manipulations Monitoring Design Recommendation: Management of degraded wetland prairies Manipulations Monitoring Design Recommendation: Management of upland prairie habitats with special-status species.. 31 Manipulations Monitoring Recommendation: Management of upland prairie habitats without special-status species 33 Manipulations Monitoring Design PRIORITIES FOR RECOMMENDATIONS Rare-plant monitoring... 36

3 Habitat management Priorities for investigating the effects of management manipulations OTHER RECOMMENDED ACTIVITIES CONCLUSIONS ACKNOWLEDGEMENTS REFERENCES APPENDIX Erigeron decumbens var. decumbens Lupinus sulphureus ssp. kincaidii... 49

4 SUMMARY This report presents specific guidelines and recommendations for managing the biologically important habitats and plant species of Fern Ridge, a Corps of Engineers Project in western Oregon. These habitats and species are threatened by woody-plant encroachment and competition from non-native pest plants. Our goal in developing these recommendations was to balance the short-term need for immediate restoration and protection and the long-term benefits of building scientific understanding for improved future management. We first summarize the relevant literature on Fern Ridge habitats and plant species. We then evaluate the wide range of management options available and recommend a small number of effective and feasible manipulations for field application. Recommended manipulations include prescribed burning, annual mowing, manual removals, and sowing seeds of native species. Separate recommendations are made for high-quality wetland prairies, degraded wetland prairies, and upland prairies. We further describe how to apply these manipulations using valid but efficient statistical designs and measuring effects with a streamlined monitoring program. This will allow the evaluation of the effectiveness of management activities in achieving their objectives. Wilson and Ingersoll Fern Ridge

5 INTRODUCTION The Army Corps of Engineers Fern Ridge Project, near Eugene, Oregon, contains two of the rarest habitats in western Oregon, native wetland prairie and native upland prairie. These natural areas support several plant and animal species listed under Federal and State Endangered Species Acts. The current management program implemented by personnel at Fern Ridge aims to maintain and improve these habitats and to sustain the species they contain. Recent biological research provides new insights that should be useful for future management programs (summarized by Wilson, Connelly, and Lantz 1993). The purpose of this report is to use these findings to make specific recommendations for managing these habitats and species. These recommendations seek to balance the short-term needs for immediate management with the longterm benefits of building scientific understanding for improved future management. The Willamette Valley of western Oregon stretches about 220 km, from the Portland area in the north, to Cottage Grove, where the Cascade and Coast Ranges converge. The valley is characterized by broad alluvial flats separated by low hills. Much of the valley floor is covered by poorly drained alluvial deposits. Wet winters and poor drainage contribute to seasonal inundation of bottomlands. Nineteenth century immigrants to the valley encountered a landscape dominated by prairie and oak savanna, with riparian forests along permanent waterways. The open, grassy nature of the valley was maintained by frequent fires set by the Kalapuya tribe to facilitate hunting and gathering (Boag 1992). Climax vegetation of the valley bottomlands in the absence of fire is probably Fraxinus latifolia woodland; that of the uplands, Pseudotsuga menziesii forest (Johannessen et al. 1971). Beginning with Euro-American settlement, fires were suppressed in the Valley and widespread agricultural and urban development initiated. Most of the few unplowed, ungrazed, and unurbanized prairie remnants are now threatened by succession to shrublands and forest and by invasion of aggressive non-native species. Wilson and Ingersoll Fern Ridge

6 The original valley grasslands can be separated into two broad types: wetland prairie and upland prairie. Wetland prairies occur on bottomlands with poorly drained soils, and generally experience winter flooding or ponding. Upland prairies occur on better drained soils and often intergrade with oak savanna. The area around Fern Ridge Reservoir contains remnants of both prairie types. Both wetland prairies and upland prairies once supported a wide variety of native grasses and forbs. Many rare plant species, several of them endemic to the Willamette Valley, are native to these prairies. Loss of habitat through agricultural and urban development and succession has led to the near extirpation of several of these species. Thirteen rare species are currently known to occur in prairie remnants at Fern Ridge. METHODS The management recommendations in this report were developed using the methodology presented in "Management guideline methodology: Integrating scientific information into the management process," a report to the Corps of Engineers Waterways Experiment Station Wilson and Ingersoll Fern Ridge

7 (Wilson and Lantz 1992). Steps 1 through 5 of this methodology (Table 1) were followed in this project. We hope that the subsequent three steps implementing management activities, Table 1. Steps that build an effective project with the cooperation of managers and scientists (Wilson and Lantz, 1992). 1. Set goals 2. Set project scope 3. Set specific objectives 4. Gather information prior to main project 5. Design active adaptive management procedures 6. Implement management activities 7. Monitor project progress 8. Evaluate and report results monitoring project progress, and evaluating and reporting results will follow acceptance of the recommendations in this report. Meeting We conducted a meeting at Fern Ridge administrative headquarters on November 22, 1993, to review the project's goals, scope, and objectives; to review progress on this project; and to discuss management options at Fern Ridge (Table 2). Wilson and Ingersoll Fern Ridge

8 Goals, scope, and objectives should normally be discussed by project personnel very early in the project history. The development of the formal methodology (Wilson and Lantz 1992) Table 2. Participants in and others invited to the meeting at Fern Ridge administrative headquarters, November 22, Participants: Kathy Connelly Richard Hayes Cheryl Ingersoll Mark Wilson Bureau of Land Management COE, Fern Ridge Oregon State University Oregon State University Invited but did not participate: James Beal Susan Strehl COE, Fern Ridge COE, Fern Ridge concurrently with the conduct of this project at Fern Ridge, however, prevented formal earlier discussion. Research review The report "Plant species, habitat, and site information for Fern Ridge Reservoir," presented to the Corps of Engineers Waterways Experiment Station (Wilson, Connelly, and Lantz 1993) compiled and interpreted information on (a) upland prairie and wetland prairie habitats, (b) special-status species found at Fern Ridge, and (c) fire ecology research conducted at Fern Ridge. These results are summarized in a later section of this report. GOALS, SCOPE, OBJECTIVES, AND CONSTRAINTS The participants at the Fern Ridge meeting agreed on the following goal, scope, and objectives statements for this project: Wilson and Ingersoll Fern Ridge

9 Goal: To protect and restore the native biological resources at Fern Ridge. Scope: The biological resources that are the focus of this project are (a) the wetland prairie and upland prairie habitats with substantial native species components (marked in Figure 1 of Wilson, Connelly, and Lantz (1993)) and (b) the plant species with special legal status. The resources should be managed to produce meaningful results upon implementation and sustainable systems for the foreseeable future. General objective: To develop specific guidelines for maintaining and improving the habitats and special-status plant species at Fern Ridge. Fern Ridge personnel have additional and immediate management needs not completely met by these goal, scope, and objective statements. Their needs include management guidelines for restoring poorer-quality habitats and halting encroachment of reed canary-grass into wetland prairies. Fern Ridge personnel also must account for non-biological considerations, like recreation. We agree that these additional concerns are very important to the overall management of Fern Ridge. We try to address this expanded focus as best we can in this report. We suggest that future projects address these concerns directly and develop appropriate and specific management recommendations. A constraint to this project is the relatively narrow focus of previous research at Fern Ridge. The bulk of site-specific information about restoration and management is limited to Rose Prairie and Fisher Butte, both high-quality habitats, and to special-status plant species. It would be dangerous to extrapolate the conclusions from these studies to degraded, lower-quality habitats. Fern Ridge personnel also emphasized certain constraints to the implementation of management recommendations. Budgetary cutbacks have left the current staff without spare botanical and ecological expertise and inadequate funding for contracting botanical and ecological work. Therefore, they advised that any recommendations we make should be within the range of time and expertise of Fern Ridge staff. We kept these constraints in mind in designing manipulations and monitoring programs. But the protection and restoration of the biological resources at Fern Ridge require a commitment to adequate evaluation of field Wilson and Ingersoll Fern Ridge

10 manipulations and the monitoring of rare species. These essential activities can be achieved by a long-term partnership between the Corps of Engineers and the local scientific community. REVIEW OF THE LITERATURE This section briefly summarizes the information presented by Wilson, Connelly, and Lantz (1993) on the important habitats and special-status plant species at Fern Ridge. We supplement this information with a discussion of the major pest species of the wetland prairie and upland prairie habitats. Description of habitats Wetland prairie. This habitat occurs primarily along the east and south shores of the reservoir. The highest quality remnants are located in Rose Prairie and Fisher Butte. Other wetland prairies are in the Royal Amazon Management Unit south of the Amazon Canal and in the area just south of Royal Avenue. These wetland prairies are characterized by a high water table, seasonal ponding and/or inundation, and deep, poorly drained soils. Pedestal microtopography is common. Two plant communities (Rosa nutkana / Deschampsia cespitosa - Juncus nevadensis, and Deschampsia cespitosa / Danthonia californica) have been differentiated at Fisher Butte. In both communities, a variety of grasses and forbs, mostly native, dominate the vegetation. Important natives include Deschampsia cespitosa, Rosa nutkana, Juncus nevadensis, Danthonia californica, Madia glomerata, and Grindelia integrifolia; Holcus lanatus, Mentha pulegium, Agrostis spp., Centaurium umbellatum, and Hypericum perforatum are among the conspicuous non-natives. Rare species include Lomatium bradshawii, Erigeron decumbens var. decumbens, Calochortus uniflorus, Horkelia congesta ssp. congesta, Cicendia (= Microcala) quadrangularis, and Sagittaria latifolia. Three plant communities (Rosa nutkana / Anthoxanthum odoratum, Deschampsia cespitosa / Danthonia californica, and Vaccinium Wilson and Ingersoll Fern Ridge

11 caespitosum) have been distinguished at Rose Prairie. Important native species include Deschampsia cespitosa, Grindelia integrifolia, Danthonia californica, Eriophyllum lanatum, Vaccinium caespitosum, and Aster curtus; non-natives include Anthoxanthum odoratum, Hypericum perforatum, Holcus lanatus, Agrostis tenuis, Rumex acetosella, and Briza minor. The Vaccinium caespitosum community contains many species in common with the Deschampsia cespitosa / Danthonia californica, but is distinguished by the presence of V. caespitosum, other native species, and high lichen cover. Rare species at Rose Prairie include Lomatium bradshawii, Aster curtus, Cicendia quadrangularis, Calochortus uniflorus, and Horkelia congesta spp. congesta. Prescribed burns have been conducted at both Fisher Butte and Rose Prairie to enhance native vegetation and to inhibit the invasion of woody species. The effects of these burns on the vegetation are inconclusive. Burning generally increased the cover and richness of native species, but often increased non-natives as well. Burning reduced woody-plant cover at Rose Prairie but increased it at Fisher Butte. At nearby Willow Creek preserve, The Nature Conservancy has conducted prescribed burns to control Fraxinus latifolia invasion into wetland prairie. These efforts also have been only partially successful, because many trees resprouted vigorously. Upland prairie. This habitat occurs on scattered parcels around the reservoir, especially on the northeast shore, where the rare Fender's blue butterfly (Icaricia icarioides fenderi), a candidate for federal listing, is found. Additional upland prairies are found near the southwest and south shores, and on Gibson Island. Very little information is available concerning the upland prairies of the Willamette Valley. These upland sites are characterized by moderately deep, poor to well-drained loams of alluvial origin. Unlike those of the wetland prairies, soils are not seasonally flooded. The vegetation of remnant upland prairies has been altered by widespread invasion of exotic species, Wilson and Ingersoll Fern Ridge

12 particularly grasses. Important native species of higher-quality upland prairies include Festuca rubra, Elymus glaucus, and Ranunculus occidentalis. The vegetation of upland prairie sites at Fern Ridge has not been studied carefully, but visual assessment of Fender's blue butterfly habitat shows that these sites have many exotic grasses and forbs, and that exotic woody species, especially Cytisus scoparius and Rubus discolor, are encroaching upon the grassland. A few areas dominated by native grasses (especially Festuca rubra) and native forbs, including Lupinus sulphureus ssp. kincaidii, still occur on these sites, and indicate the value of management actions to restore habitat quality and native species abundance. Special-status plant species Information from the literature. Thirteen special-status species have been found at Fern Ridge (Table 3). Lomatium bradshawii, Erigeron decumbens var. decumbens, Horkelia congesta ssp. congesta, Sidalcea cusickii, Sidalcea campestris, Lupinus sulphureus ssp. kincaidii, and Lathyrus holochlorus are endemic to the Willamette Valley or western Oregon. Aster curtus, Montia howellii, Cicendia (=Microcala) quadrangularis), and Calochortus uniflorus are limited to the West Coast states, while Cyperus rivularis var. rivularis and Sagittaria latifolia are rare in Oregon but widespread elsewhere. Lomatium bradshawii is listed as Endangered under the federal Endangered Species Act. Erigeron decumbens var. decumbens, Aster curtus, Montia howellii, and Lupinus sulphureus ssp. kincaidii are federal candidates for listing. Clark, Finley, and Ingersoll (in review) have recommended that Erigeron decumbens var. decumbens be federally listed as Endangered. Kuykendall and Kaye (in review) have recommended upgrading the federal status of Lupinus sulphureus ssp. kincaidii to C1, meaning that enough information exists to list the species as Threatened or Endangered. Of the species having formal federal or state status, Lomatium bradshawii, Aster curtus, and Horkelia congesta spp. congesta are fairly widespread at Fern Ridge, while the distributions of Erigeron decumbens var. decumbens, Montia howellii, and Lupinus sulphureus ssp. kincaidii are more restricted. Wilson and Ingersoll Fern Ridge

13 TABLE 3. Legal status, habitat affinities, and presence within management units of special status plant species. Species codes: Lom bra = Lomatium bradshawii, Eri dec = Erigeron decumbens var. decumbens, Ast cur = Aster curtus, Mon how = Montia howellii, Hor con = Horkelia congesta ssp. congesta, Cic qua = Cicendia (= Microcala) quadrangularis, Cyp riv = Cyperus rivularis var. rivularis, Sid cus = Sidalcea cusickii, Cal uni = Calochortus uniflorus, Sag lat = Sagittaria latifolia, Lup sul = Lupinus sulphureus ssp. kincaidii, Sid cam = Sidalcea campestris, Lat hol = Lathyrus holochlorus. Status codes: E = endangered, C = candidate, C1 = category 1 candidate, C2 = category 2 candidate. Plant Status Habitat Management Unit Species Fed State Wet Upland Amazon Apple- East Fisher Jean's Kirk Royal Shore South West West Prairie Prairie Dike #2 gate Coyote Butte Penin. Pond Amazon Lane Marsh Coyote Shore Lom bra E E T T T T T T T Eri dec C1 E T T T Ast cur C2 C T T T T T T T T Mon how C2 C T T T Hor con C T T T T T Cic qua T T Cyp riv T T Sid cus T T T Cal uni T T Sag lat T T T T T T Lup sul C2 C T T T Sid cam T T Lat hol T T Wilson and Ingersoll Fern Ridge

14 Very little is known beyond the basic biology of most of these special-status species. All of the 13 species (except Montia howellii and Cicendia quadrangularis) are perennial. Several species (Lomatium bradshawii, Montia howellii, Horkelia congesta spp. congesta, Cyperus rivularis var. rivularis, Cicendia quadrangularis, and, possibly, Erigeron decumbens var. decumbens) rely exclusively on reproduction by seeds. Many require special insect pollinators to set seed. Lomatium bradshawii disperse seeds in May or June, Erigeron decumbens var. decumbens in July, Lupinus sulphureus ssp. kincaidii in July, Aster curtus in August or September; reliable seed dispersal information is not available for the other species. Probably all of the 13 species are easily suppressed by competition from other herbaceous vegetation, and none appears to occur under high shrub or tree cover. Appendix I presents an update for the information on Erigeron decumbens var. decumbens and Lupinus sulphureus ssp. kincaidii given by Wilson, Connelly, and Lantz (1993). Data from field studies. Multi-year population monitoring studies exist for Lomatium bradshawii, Erigeron decumbens var. decumbens, and Aster curtus. Results are inconclusive, with no consistent trends. The only other rare-plant monitoring at Fern Ridge has apparently been one-time surveys of Cicendia (= Microcala) quadrangularis and Lupinus sulphureus ssp. kincaidii. The effects of prescribed burns on populations of Lomatium bradshawii (at Rose Prairie and Fisher Butte) and Erigeron decumbens (at Fisher Butte) have been monitored since At both sites, flowering and seed production of L. bradshawii showed dramatic increases in response to burning, but vegetative responses varied. Burning had few clear effects on E. decumbens var. decumbens. An intensive demographic monitoring program for Erigeron decumbens was established at Fisher Butte in 1993 (Ingersoll, Finley, and Clark 1993); results are not yet available. Wilson and Ingersoll Fern Ridge

15 Major threats to habitats and species Threats to habitats. Several factors pose immediate and major threats to prairie habitats at Fern Ridge. A threat to wetland prairie sites is the continued invasion of Phalaris arundinacea, an aggressive grass that has formed extensive monocultures in emergent wetlands, especially along the east shore of the reservoir, and that appears to be expanding into wetland prairies. Prolonged flooding from the alteration of reservoir pool levels may increase its rate of spread. Another major threat is succession in wetland prairies to vegetation dominated by trees (e.g., Fraxinus latifolia) and shrubs (e.g., Rosa nutkana). Encroachment by the woody exotics Rubus discolor and Cytisus scoparius poses an immediate threat to upland prairies. The exotic grass Arrhenatherum elatius threatens to form monocultures in some areas. All these problem plants have the similar ability to spread vegetatively, which increases the damage they do to native habitats. Their ability to regenerate from stems or rootstocks makes their control particularly difficult. Threats to species of special concern. The threats to habitats also threaten the survival of special-status species. For example, succession to forest would eliminate the open habitat conditions apparently required by these rare plants. Other gross habitat modifications are caused by the invasion of exotics such as Phalaris arundinacea, Cytisus scoparius, Rubus discolor, and Arrhenatherum elatius. Changing ecological interactions may also pose threats to individual species. Heightened herbivory, disease, predation, and competition may harm populations. Reduced pollinator abundances resulting from habitat loss and pesticide use may reduce reproduction in primarily or obligately cross-pollinated species such as Lomatium bradshawii, Aster curtus, and Lupinus sulphureus ssp. kincaidii. The accumulation of litter produced by vigorous exotic grasses might inhibit the establishment of native species. The extent to which such interactions may threaten any of the special-status species remains unknown. Wilson and Ingersoll Fern Ridge

16 Information on major pest species Some prairies, especially those previously subjected to agricultural use, are dominated by non-native grasses such as Anthoxanthum odoratum, Agrostis tenuis, Dactylis glomerata, and Panicum capillare. While reduction of these exotic species is an aim of prairie restoration, these species probably do not constitute a primary, immediate threat, because they do not appear to rapidly modify their habitat or completely eliminate most native species. Several other species, however, are particularly aggressive invaders and drastically modify prairie habitats by suppressing native vegetation and reducing species diversity. The primary pest plant in the wettest portions of the wetland prairies is Phalaris arundinacea. In the upland prairies, the primary pest species are Cytisus scoparius, Rubus discolor, and Arrhenatherum elatius. Phalaris arundinacea (reed canary-grass) is a widespread and aggressive weed in North America. It is a strongly rhizomatous perennial and may grow more than a meter in height. It has been widely introduced for forage and hay. P. arundinacea occurs in moist areas at low elevations, especially along streams and ditches. At Fern Ridge, it is particularly abundant in the transition between reservoir and wetland prairie. It forms dense, persistent monocultures which have spread considerably at Fern Ridge over the last decade or more (Richard Hayes, pers. comm.). P. arundinacea monocultures threaten both high-quality and degraded wetland prairies sites. Control of Phalaris arundinacea has proved extremely difficult (Apfelbaum and Sams 1987). Late spring burning might reduce P. arundinacea abundance, but also harms many native species; early spring burning may accelerate the spread of the grass (Henderson 1990). Selective hand-pulling has been effective when done several times a year for several years (Henderson 1990). However, Gillespie and Murn (1992) found the results of mechanical removal of root masses and replanting with native species inconclusive. Glyphosate applications or solarization with plastic were effective when done over three years and followed with seeding of natives; Wilson and Ingersoll Fern Ridge

17 without seeding, Phalaris reinvaded (Henderson 1990). Mowing has met with some success. Gillespie and Murn (1992) report a study where Phalaris abundance was reduced in areas mown in late spring (before seed maturation) and again in autumn over four years and were replaced by native species. Apfelbaum and Sams (1987) suggest that application of boron (as a pesticide) or chopping of culms at anthesis may be effective control measures. If culms are chopped, all plant material should be removed, because P. arundinacea resprout readily even from short segments (Roslansky et al. 1975). At Horkelia Prairie (Fern Ridge), preliminary results indicate that burning did not control Phalaris, but solarization with clear plastic was remarkably effective. During the year following solarization, Phalaris was completely eliminated, replaced by a dense stand of Eleocharis palustris and other native species (Ingersoll and Wilson, unpublished data). While Phalaris arundinacea invades primarily through rhizomatous spread, establishment from seed may also be of concern. Henderson (1991) suggests that Phalaris invasion of oak savanna occurred by seed dispersal from an adjacent wetland. Some populations of Phalaris produce dormant seeds (Berg 1982), enabling propagules to accumulate in a soil seed bank that may persist after initial control measures. Rubus discolor (also known as R. procerus, Himalayan blackberry) is a Eurasian native. It has established in disturbed areas, particularly along fencerows and roadsides and in old fields, from California to British Columbia, as well as other parts of the world. It forms dense thickets that exclude virtually all other species. It reproduces by seeds, by rooting at cane tips, by adventitious shoots from roots, and by growth of severed pieces of canes and roots (Amor 1974, Richardson 1975). Removal of topgrowth of established thickets does not kill the plant, and older plants are resistant to herbicides (Amor 1974). Repeated mowing or hand removal may be the most satisfactory means of control for this species. Arrhenatherum elatius, native to Eurasia, but widely introduced as a forage grass and soil stabilizer, has established throughout western North America. Two forms of A. elatius occur in the Willamette Valley, tall oatgrass and onion couch (var. bulbosum) (Taniphiphat and Appleby Wilson and Ingersoll Fern Ridge

18 1990a). Both are perennial grasses that spread vegetatively and reproduce by seed. A. elatius var. bulbosum produces a corm from which rhizomes elongate, making control particularly difficult. In one case (Hewett 1985), 5 years of mowing was necessary to control A. elatius var. bulbosum. Pfitzenmeyer (1962) recommends mowing close to the ground. Since A. elatius appears to shed seeds later in the season than some of the native prairie species, late mowing might check A. elatius while permitting many native species to complete their life cycle. In contrast, patterns of seasonal corm and rhizome depletion in A. elatius var. bulbosum (Taniphiphat and Appleby 1990b) point to a late May mowing as most effective for controlling vegetative growth. Cytisus scoparius (Scot's broom), native to Europe and north Africa, is widely established west of the Cascades. This green-stemmed shrub can live up to 17 years (Bossard 1993). It can resprout from rootstocks and its seeds can sometimes survive at least 5 years in the soil (Bossard 1993). Since its seeds require scarification (Bossard 1993), fire can stimulate germination from the soil seed bank and lead to increased shoot density. Gaps in knowledge Large gaps exist in the understanding of the composition and dynamics of Willamette Valley prairies and their species. These gaps limit our ability to effectively maintain and restore these systems. We lack baseline information on competitive interactions, long-term trends in composition, and the effects of encroachment by woody species. The careful studies on the effects of fire on Rose Prairie and Fisher Butte are indispensable, but we do not know how broadly applicable their conclusions are to other types of habitats. Other information about the effects of vegetation management techniques such as burning and mowing is anecdotal. For individual species of special concern, most of the biological data needed to develop appropriate management strategies are still lacking. For instance, we know little about population trends, reproductive biology, or interactions with other species. We lack basic Wilson and Ingersoll Fern Ridge

19 understanding of the potential effects of various management techniques on species viability, except for fire effects on Lomatium bradshawii and Erigeron decumbens var. decumbens. Management without this knowledge, based instead on common sense, can sometimes be useful. But such manipulations are also likely to be inefficient or have undesired side effects. For example, burning degraded prairies or mowing Cytisus scoparius can actually increase the abundance of pest plants. An alternative approach is to design manipulations to and monitor their effects to produce the kind of information needed for improved, second generation management strategies. This is the adaptive management approach. BENEFITS OF ADAPTIVE MANAGEMENT Scientists are often cautious, wanting to conduct extensive studies before making management recommendations. This approach can be unacceptably slow, since action must await study. An alternative approach is to conduct scientific studies in conjunction with management activities. This approach, known as adaptive management (Walters and Holling 1990), can provide several benefits. Collecting data and analyzing results from management activities provides the only convincing way to assess the effectiveness of manipulations. This assessment is most powerful and scientifically valuable when comparing different types of manipulations. Carefully designed management and monitoring activities could also efficiently fill gaps in our knowledge about how the valuable habitats and species at Fern Ridge respond to management manipulations. Adaptive management is most effective when management actions are treated as planned experiments designed to generate data that will quickly improve both management and scientific understanding. For these reasons, we advocate an adaptive management approach at Fern Ridge, and recommend a long-term commitment between managers and scientists to fulfill its promise. Wilson and Ingersoll Fern Ridge

20 EVALUATING MANAGEMENT OPTIONS Managers have several types of manipulations available at Fern Ridge, including prescribed burning, mowing, manual removal of plants, herbicide application, and sowing seeds of native species. Several options are possible for the application of each manipulation. This section outlines the options and evaluates them against specific management objectives, using the scientific knowledge and field experience currently available. Management objectives The management of biological resources at Fern Ridge follows several specific objectives that derive naturally from the goals, scope, and general objective described in a previous section. Although we present a single set of management objectives, their application will differ somewhat from site to site. Management objective 1: Maintain viable populations of special-status plant species. Viable populations are those that maintain their abundance indefinitely; viability can be measured either by repeated censuses or by demographic models. Management objective 2: Restore the structure, vegetative cover, and species diversity of wetland prairies and upland prairies to their historical levels. The historical character of these prairies is determined by early accounts and from inspecting high-quality remnant prairies. Management objective 3: Reduce the abundance of pest plant species. Management objective 4: Establish monitoring that will allow the evaluation of the relative success of manipulations in achieving objectives 1-3. More than one of these objectives can sometimes be addressed at a time (Wilson, Hammond, and Kauffman 1992). For example, one effect of habitat restoration (objective 2) is the improvement of growing conditions for populations of rare plants and animals, increasing their viability (objective 1). Management recommendations carry little practical value if they cannot be implemented. Therefore, an important adjunct to these objectives is the necessity to factor relative expense and feasibility of manipulations into our recommendations. Wilson and Ingersoll Fern Ridge

21 Application of ecological knowledge Ecological knowledge provides a basis for predicting the effects of possible management actions. This section discusses how the competitive abilities, growth rates, and reproduction biology of species at Fern Ridge would affect their response to manipulations. The low foliage of many of the native species at Fern Ridge makes them susceptible to crowding by pest plants. This is true of special-status species like Lomatium bradshawii as well as dominants like Deschampsia cespitosa and Festuca rubra. Management manipulations that kill pest plants or reduce their vigor and stature would reduce this crowding pressure. Pest plants generally grow more rapidly and produce more seeds than native plants under high-fertility soil conditions. This ability to use extra resources matches their behavior as weedy and invasive species. Management manipulations like low-intensity prescribed burning that convert biomass into soil nutrients might actually favor pest plants. In the case of mowing, cuttings should be removed from the site to prevent the increase in soil fertility. Several of the special-status and pest plant species at Fern Ridge depend on seed production for their population recruitment. The ideal management approach would be to decrease seed production by pest plants while increasing seed production by native species. Likewise, seedling establishment by native species should be improved while hindering seedling establishment by pest plants. Four methods might be feasible to obtain these objectives. First, manipulations like burning or mowing can be conducted before seed production by most pest plants but after seed production by most native species. More information on the timing of seed production is needed to refine this technique for all habitats at Fern Ridge. Second, the height of mowing can be set to remove taller pest plants while leaving native species. More information on plant heights is also needed to refine this technique for all habitats at Fern Ridge. Third, litter removal often improves seedling establishment rates. Litter removal might be one of the beneficial effects of prescribed burning. We know of no way, however, that litter removal can Wilson and Ingersoll Fern Ridge

22 benefit seedling establishment by native species without also benefitting pest plant species. Fourth, seed production and seedling establishment by native species can be enhanced by sowing seeds produced by Fern Ridge farm operations. This enhanced seedling establishment by native species has the added benefit of taking away establishment sites from pest plant species. Evaluation of options Since fire has played a historical role in the wetland prairie and upland prairie habitats at Fern Ridge, prescribed burning is a leading candidate as a tool for habitat restoration (management objective 2), controlling pest plants (management objective 3), and improving the growing conditions for rare plants (management objective 1). Recent field tests also show that prescribed burning has promise for managing high-quality wetland prairies (Kauffman and Connelly 1988, Connelly and Kauffman 1991, Wilson, Connelly, and Lantz 1993), with clear evidence of enhancing Lomatium bradshawii populations. Other effects on these sites are still unclear, however. The effects of prescribed burning are also unclear for sites dominated by nonnative species. Preliminary data from Horkelia Prairie (a partially degraded habitat adjacent to Rose Prairie) show that burning might promote dominant non-native grasses and inhibit native grasses (Wilson et al., unpublished data). Therefore, the effect of burning on sites differing in quality warrants closer attention. Prescribed burning can be conducted at different frequencies (annual to every five years or more) and at different seasons (summer or fall). Prescribed fires after several years of fuel build up will also be more intense than more frequent fires, leading to higher plant mortality. The timing of prescribed burning can produce dramatically different results, depending on the phenological stage of plants. For example, a low-intensity fire in the fall will burn biomass but probably leave unharmed many of the seeds dispersed during the summer. If these seeds are from pest plants, the fire will be less effective at habitat improvement. An early summer fire will prevent seed dispersal and probably kill more plants. An open question (see Other Wilson and Ingersoll Fern Ridge

23 Recommended Activities) is whether native species differ from pest plant species in their timing of seed dispersal. Mowing is another widespread tool for habitat restoration (management objective 2), controlling pest plants (management objective 3), and improving the growing conditions for rare plants (management objective 1). Mowing can be conducted at different frequencies, different seasons, and different heights. As with fire, mowing in the fall will remove biomass but leave unharmed the seeds dispersed during the summer. A spring or early summer mowing will prevent seed dispersal. Early mowing would also probably kill more plants, since plants would have depleted belowground energy stores. Mowing height can be an important management option. Many pest grass species (like Arrhenatherum elatius) and shrub species (like Rosa nutkana) grow taller than the preferred native species. A mower blade set above the native canopy but below the leaves and seed heads of pest plants would simultaneously harm the pest plants and boost the unharmed native plants by removing competitors. Frequent mowing is often necessary to control many pest plant species. Manual removal is often an effective and efficient form of pest plant control (management objective 3). When pest plants inhibit rare plants, pest plant control also addresses management objective 1. Manual removal of both stems and rhizomes is especially effective for killing plants that resprout from belowground structures. As with prescribed burning and mowing, effective pest plant control by manual removal can require application at different seasons or at high frequencies. Although manual removal is labor intensive, it can target certain species for acute attention while leaving other species unaffected. And successful pest plant control from manual removal is more efficient that unsuccessful pest plant control with another method. The application of herbicides is a widespread and effective pest plant control method. When pest plants inhibit rare plants, pest plant control also addresses management objective 1. Care must be taken to use herbicides with application techniques that harm pest plants but do not Wilson and Ingersoll Fern Ridge

24 harm preferred native species. Current regulations governing Fern Ridge prevent the use of herbicides in the prairie habitats investigated in this project (Richard Hayes, pers. comm.). Ecological restoration (management objective 2) is often more effective when pest plant control is accompanied by sowing seeds of native plants. This boost provided to native species increases their ability to dominate a site against the pressures of aggressive weeds. A sowing program must use seeds with a genetic structure appropriate for the local conditions (Millar and Libby 1989). Few commercial sources for seeds of native species are available, and the sources of the seeds that are available are almost always poorly documented. Therefore, a program at Fern Ridge to sow seeds of native species should start with an on-site farming operation. This operation would propagate native species in nurseries or farm fields from seeds collected from Fern Ridge sources. The harvest of seeds would then provide the seed stock for subsequent habitat restoration. The implementation of seed sowing also requires decisions about site preparation before sowing and about the frequency of sowing. For example, sowing is most effective if manipulations like burning or mowing first produce bare soil sites for seedling establishment. Monitoring is an essential component in an adaptive management strategy, because it is the only way to assess the effectiveness of different types of manipulations (management objective 4). Monitoring at Fern Ridge should measure the response of special-status species, dominant native species, important pest plant species, and community structure (like the abundance of woody species). This combination of measurements allows the overall assessment of success in achieving management objectives 1, 2, and 3. Wilson and Ingersoll Fern Ridge

25 Table 4. Criteria of an effective monitoring program. The objectives of the monitoring program are stated explicitly The sampling scheme is statistically valid and completely described The field measurement procedures are described and applied uniformly The data analysis procedures are statistically valid and described before field measurements are begun Guidelines are developed for interpreting monitoring data (for example, for recognizing declines in populations of special-status species) Procedures are in place for reassessing the monitoring programs objectives and methods Effective monitoring must fulfill several criteria (Table 4). Many of these criteria (such as making objectives and procedures explicit) discourage three pitfalls of monitoring programs: programs without purpose, programs that collect data that are never put to use, and programs that collect data that cannot be interpreted because of invalid procedures. RECOMMENDATIONS The purpose of this section is to present specific recommendations for managing the different habitats at Fern Ridge. Recommendation: Seed farming We recommend that the Fern Ridge Project initiate a program of growing native plant species in nurseries or farm plots to provide seeds for habitat restoration. These seeds will be instrumental in increasing the overall of native species and controlling the abundance of nonnative pest species. Since suitable seed stocks of these species are unavailable, their production should be conducted at Fern Ridge. We recommend that the first plants grown be Deschampsia cespitosa and Festuca rubra, the dominant native species in the wetland prairies and upland prairies, respectively. Nurseries Wilson and Ingersoll Fern Ridge

26 or farm plots for this program should be at Fern Ridge under conditions similar to the site requirements for the two species being grown. The Center for Plant Conservation (1991) guidelines for sampling rare plants also provide guidance for sampling the more widespread Deschampsia cespitosa and Festuca rubra. Seeds should be collected from 3-5 sites at or near Fern Ridge with abundant Deschampsia cespitosa and Festuca rubra. Collecting local seeds improves the chances that collected genotypes will be suited to the habitats being restored. Seeds from different sources should be kept separate to allow future comparisons. Within each site, seeds should be collected from at least individuals scattered over the site. This scheme increases the chance of collecting most of the genetic diversity present within populations. No population should be depleted of its seeds. The seeds produced from the farming operation will be used for habitat restoration. Since we recommend in other sections that seed sowing be an experimental treatment, seeds from different sources should be mixed just before field application. Recommendation: Management of high-quality wetland prairies The best examples of wetland prairie habitats at Fern Ridge are Rose Prairie, Fisher Butte, and portions of the Royal Amazon Management Unit. This section describes the recommended manipulations and monitoring for these habitats. Manipulations. An unresolved issue about prescribed burning of high-quality wetland prairies is the best interval between prescribed fires. In order to combine immediate management objectives with answering questions about proper fire interval, we recommend that these high-quality prairies be burned at one of two intervals. The best intervals to examine are every 2-3 years and every 5-6 years. We also recommend that prescribed burning be shifted to summer, to take advantage of any gaps between seed dispersal by key native species and dispersal by major pest plants. If outside constraints prohibit summer burning, fall burning should still be effective. Any trees unkilled by burning should be cut and removed before they Wilson and Ingersoll Fern Ridge

27 reach 1.5 m in height. Efforts should also continue to protect the Vaccinium caespitosum community from burning. Monitoring. Monitoring programs are essential for allowing Fern Ridge personnel to assess and adjust manipulation schedules. We therefore recommend that manipulations of the high-quality wetland prairies be accompanied by a well-designed monitoring program. Moreover, monitoring will provide information on the possible stimulation of seed production by non-native plant species because of prescribed fire. We recommend that Fern Ridge personnel continue to census special-status species present at Rose Prairie and Fisher Butte. (The section on Priorities for Recommendations describes which species to monitor.) In addition, permanent plots should be established for monitoring changes in abundance of the key native species (Deschampsia cespitosa) and the key pest plant species (Anthoxanthum odoratum, Phalaris arundinacea, and Holcus lanatus) and changes in woody plant cover. Several of these permanent plots should be located across each habitat. The monitoring plots should be measured annually for these valuable sites. The series of permanent plots set up by Kathy Connelly at Rose Prairie and Fisher Butte can be used in this monitoring program. The monitoring procedures should fit the criteria presented in Table 4. Setting the details of these monitoring procedures is beyond the scope of this project and report. Therefore, we recommend that the Corps of Engineers seek professional advice for developing monitoring programs and training Fern Ridge personnel (see Other Recommended Activities). Wilson and Ingersoll Fern Ridge

28 Table 5. Treatments assigned to different areas within high-quality wetland prairie sites. Burn every 2-3 years Burn every 5-6 years Rose Prairie North T Rose Prairie South Royal Amazon North T T Royal Amazon South Fisher Butte West T T Fisher Butte East T Design. We recommend that the two burning-interval treatments be assigned to habitats in a randomized complete block design (Table 5). In this design, treatments are assigned at random to sections of each block, which in this case are the different habitat units. Using this design, results can be tested statistically. Recommendation: Management of degraded wetland prairies Manipulations. Where special-status species are absent or of low abundance, degraded areas offer the opportunity for greater experimentation. We recommend that subareas within these habitats be treated with a variety of manipulations, including burning at one of two intervals, mowing annually, and sowing seeds of Deschampsia cespitosa after burning. Mowing should be conducted annually in approximately mid-summer, when major pest plant species are in flower. Cuttings from the mowing should be removed from the sites. For the sowing treatments, seeds of Deschampsia cespitosa should be sown in the fall after each biennial prescribed burn at rates of about 2.5 kg/ha (. 400 seeds/m 2 ). Wilson and Ingersoll Fern Ridge

29 Monitoring. Little information exists about the response of wetland prairies to mowing or of poor quality wetland prairies to any kind of manipulations. Therefore, we recommend that manipulations of these habitats be carefully monitored. Monitoring programs will allow Fern Ridge personnel to asses and adjust manipulation schedules. Without adequate monitoring, continued manipulations could produce suboptimal, even counter-productive results. We recommend that Fern Ridge personnel continue to census special-status species present at each unit. (The section on Priorities for Recommendations describes which species to monitor.) In addition, permanent plots should be established for monitoring changes in abundance of the key native species (Deschampsia cespitosa) and the key pest plant species (Anthoxanthum odoratum, Phalaris arundinacea, and Holcus lanatus), and changes in woody plant cover. Several of these permanent plots should be located across each treatment area. The monitoring plots should be measured every two years for these more degraded sites. The monitoring procedures should fit the criteria presented in Table 4. Setting the details of these monitoring procedures is beyond the scope of this project and report. Therefore, we recommend that the Corps of Engineers seek professional advice for developing monitoring programs and training Fern Ridge personnel (see Other Recommended Activities). Wilson and Ingersoll Fern Ridge