Increasingly, environmental quality is becoming recognized as a critical factor that should constrain land use planning. One important measure of a landscape's quality is its capacity to support viable populations of wildlife species. But the ability of land managers to balance conservation with other competing objectives is limited by a shortage of methodologies for assessing landscape quality. In response to this shortage, the research community has begun developing a variety of multispecies, landscape‐level, assessment models. Useful models must strike a balance between parsimony and biological realism and must be designed to make the most of limited life history data. This paper applies two such assessments to an examination of wildlife responses to scenarios of landscape change within Oregon's Willamette River Basin. The study uses GIS maps of pre‐European settlement and circa 1990 habitat conditions, and three possible realizations of how the Basin might appear in the year 2050. Our simpler assessment generated statistics of landscape change from the GIS imagery and species–habitat relationships for all 279 amphibian, reptile, bird, and mammal species in the basin. Our more complex assessment used an individual‐based life history simulator to estimate population sizes for a small subset of this fauna. These two assessments offer complementary kinds of information about wildlife responses to landscape change: estimates of habitat changes for a large number of species representing a region's biodiversity, and estimates of changes in the persistence of populations of key species. We found both good and poor correlations between our two assessments, depending upon the species and landscape. Both assessments agreed in their overall ranking of the landscapes' quality for wildlife. In most cases, the percentage change in habitat quality underestimated the percentage change in population size. In a few cases, small gains in habitat quality were accompanied by very large increases in wildlife populations. We attribute discrepancies in our two assessments to the influence habitat fragmentation had on our individual‐based model. As such, our study provides a methodology for separating the influences of habitat quality and quantity from those of habitat pattern.

Abstract:We evaluated the floristic condition of freshwater palustrine wetlands dominated by wet meadow, emergent marsh, aquatic vegetation, or open water within the rapidly urbanizing area of Portland, Oregon. USA by (1~ characterizing plant species richness (presence/absencel and composition of naturally occurring wetlands (NOWs) and mitigation wetlands (MWs) and (2) identifying relationships between floristic characteristics and variables describing land-use, site conditions, and mitigation activities. Data were collected on 45 NOWs and 51 MWs. Overall species richness was high (365 plant taxa), but more than 50% of the species present on both NOWs and MWs were introduced. Only 14 species occurred on more than half the sites, and nine of them were invasive introduced species. The mean number of native species per site did not differ between land-use categories (ANOVA, F = 0.62 at 3 and 88 df, p = 0.6031); however, wetlands surrounded by agricultural and commercial/industrial/transportation corridor uses had more introduced species per site than wetlands surrounded by undeveloped land (Fishers Protected LSD at 88 df, p -< 0.05). Although overlapping in floristic composition, NOWs and MWs had significantly different (MRPP. p < 0.01301) species assemblages that were identified using TWlNSPAN. MRPP analyses for all sites showed that watershed, land-use, HGM class, percent cover of water, and MW age were significantly related to the floristic composition of thc study wetlands. Canonical correspondence analyses further revealed that the primary gradient tor species distribution in NOWs was related to moisture; the secondary gradient was related to land-use. The primary gradient also described a strong relationship between percent cover of water and HGM class. For MWs, the primary gradient was related to watershed location and surrounding landuse; the secondary gradient was related to percent cover of water and MW age. Most MWs (44 out or 51 sites) were depressions in various settings, so while HGM class separates NOWs from MWs, it does little to distinguish MW assemblages. Our results show that wetlands in the urbanizing study area are floristically degraded. Further, current wetland management practices are replacing natural marsh and wet meadow systems with ponds, resulting in changes in the composition of plant species assemblages.

Abstract:We measured soil organic matter (SOM) concentrations in a large sample ~n = 95) of freshwater emergent and open water weltands in the Portland, Oregon, USA, ,area as part of a study of the ecological development of mitigation wetlands. Mean SOM concentrations were higher in naturally occurring wetlands (NOWs) than in mitigation wetlands (MWs) at 0-5 cm (SOM = 9.75 and 5.83%, respectively, p = 0.0001) and at 15-20 cm (SOM = 6.85, 4.68%, p = 0.0551). If temporal accumulation of SOM is occurring, it is slow; we found no significant relationship between SOM and wetland age (p = 0.6003) and no signilicant change in SOM concentration in soils in MWs sampled in 1987 and 1993, Concentrations of SOM were not significantly related to land use but were related to soil series, texture class, and association, and to hydrogcomorphic class. For a subset of wetlands monitorcd for hydrology, we also found a significant negative relationship between SOM and the extent of inundation by standing water. Mitigation may be leading to direct loss of SOM, probably resulting from soil management practices during project construction. We also show that hydrologic regime significantly affects SOM. Because most projects in our study were built in pre-existing wetlands and have extensive areas of open water, our results suggest that low concentrations of SOM are likely to persist. For SOM and probably for SOM-supported wetland functions, fundament~d goals of mitigation and wetland management (in-kind wetland replacement, no-net-loss of structure and function) are not being achieved, at least in the short term. The success of mitigation, in terms of SOM, could be improved by better project design and better management of soils during project construction.

Alien plant species are stressors to ecosystems and indicators of reduced ecosystem integrity. The magnitude of the stress reflects not only the quantity of aliens present, but also the quality of their interactions with native ecosystems. We develop an Index of Alien Impact (IAI) to estimate the collective ecological impact of in situ alien species. IAI summarizes the frequency of occurrence and potential ecological impact (Invasiveness-Impact Score (I ( i ))) of individual alien species for all aliens present in a particular location or community type. A component metric, I (i), is based on ecological species traits (life history, ecological amplitude, and ability to alter ecosystem processes) that reflect mechanisms, which can increase impact to ecosystem structure and function. While I (i) is less complex than some other multi-metric rankings of alien impact, it compares well to these metrics and to qualitative judgments. IAI can be adapted for different ecological settings by modifying the set of species traits incorporated in I (i) to reflect properties likely to breach biotic and abiotic barriers or alter ecosystem function in a particular region or community type of interest. To demonstrate our approach, we created versions of IAI and I (i), applicable to the diverse streamside vegetation of a river basin (19,631 km(2)) spanning low-elevation arid to mesic montane habitats in eastern Oregon, USA. In this demonstration effort, we (1) evaluate relationships of IAI to metrics describing invasion level, and (2) illustrate the potential utility of IAI for prioritizing alien species management activities and informing restoration goals.

Sediment has long been recognized as a leading cause of impairment of biological condition in rivers and streams of the United States. Recently, federal and state agencies have shown increased interest in developing sediment criteria to maintain or improve habitat quality for the protection of aquatic species. To develop biologically based sediment criteria, sediment amounts must be linked with aquatic vertebrate response. For our analysis, we related an aquatic vertebrate index of biotic integrity (IBI) with a measure of the areal percentage of streambed surficial fines (≤0.06 mm). The association suggested that fine sediment limits the biological potential of mountain streams. We used quantile regression to model the upper limit of IBI response; the regression equation predicted a 4.7% decline in IBI for each 10% increase in areal surficial fines. However, the limiting relationship itself did not suggest a specific sediment level above which impairment was evident. To develop more specific evidence regarding sediment impairment and to describe possible impairment thresholds along the continuous relationship, we sought additional information from (1) the range of areal percent fines at the 169 least disturbed reference sites in our sample, (2) sediment tolerance values calculated for sediment‐sensitive salmonids in the Mountains ecoregion, (3) a review of studies that describe IBI scores representing very good to excellent condition in coldwater (trout) streams of the United States, and (4) a second literature review of laboratory and field research relating the effects of sediment on the survival of salmonid eggs. Placing our initial results in the context of this additional information, we concluded that streambed areal surficial fine sediment (particle size ≤ 0.06 mm) levels of 5% or less retain habitat potential for sediment‐sensitive aquatic vertebrates in mountain streams. We offer these results as scientific guidance for the process of establishing sediment criteria.