The San Pedro River in the southwestern United States retains a natural flood regime and has several reaches with perennial stream flow and shallow ground water. However, much of the river flows intermittently. Urbanization-linked declines in regional ground-water levels have raised concerns over the future status of the riverine ecosystem in some parts of the river, while restoration-linked decreases in agricultural ground-water pumping are expected to increase stream flows in other parts. This study describes the response of the streamside herbaceous vegetation to changes in stream flow permanence. During the early summer dry season, streamside herbaceous cover and species richness declined continuously across spatial gradients of flow permanence, and composition shifted from hydric to mesic species at sites with more intermittent flow. Hydrologic threshold values were evident for one plant functional group: Schoenoplectus acutus, Juncus torreyi, and other hydric riparian plants declined sharply in cover with loss of perennial stream flow. In contrast, cover of mesic riparian perennials (including Cynodon dactylon, an introduced species) increased at sites with intermittent flow. Patterns of hydric and mesic riparian annuals varied by season: in the early summer dry season their cover declined continuously as flow became more intermittent, while in the late summer wet season their cover increased as the flow became more intermittent. Periodic drought at the intermittent sites may increase opportunities for establishment of these annuals during the monsoonal flood season. During the late summer flood season, stream flow was present at most sites, and fewer vegetation traits were correlated with flow permanence; cover and richness were correlated with other environmental factors including site elevation and substrate nitrate level and particle size. Although perennial-flow and intermittent-flow sites support different streamside plant communities, all of the plant functional groups are abundant at perennial-flow sites when viewing the ecosystem at broader spatial and temporal scales: mesic riparian perennials are common in the floodplain zone adjacent to the river channel and late-summer hydric and mesic annuals are periodically abundant after large floods.

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Many projects have been undertaken to restore urban rivers in arid regions. At the same time, passive discharge of urban water sources has stimulated redevelopment of wetlands and riparian forests along stretches of dewatered rivers. In Phoenix, Arizona, for example, some segments of the dewatered Salt River have been actively restored by planting and irrigation, whereas others have revegetated in response to runoff from storm drains and effluent drains. Our research documents how biotic communities differ between these actively restored and 'accidentally' restored areas, and between wetter and drier urban reaches. We addressed these objectives with a multi-taxa, multi-season sampling approach along reaches of the Salt River. We quantified plants using cover estimates in quadrats, birds using fixed radius, point-count surveys, and herpetofauna (amphibians and reptiles) using visual-encounter surveys. One notable finding was that wetland plants had greater richness and cover at accidentally restored sites compared with actively restored, dry urban, and non-urban reference sites. Birds and herpetofauna, however, were most species-rich at actively restored and non-urban reference sites, and riparian birds were more abundant at sites with perennial flows compared with ephemeral reaches. From a landscape perspective, the range of management approaches along the river (including laissez-faire) is sustaining a diverse riparian and wetland mosaic. Urban water subsidies are sustaining freshwater forests and marshlands, the latter a regionally declining ecosystem. In urbanized rivers of arid regions, mapping and conserving perennial stream flows arising from stormwater and effluent discharge can be an important complement to active restoration. Figure 2. Species accumulation curves for (A) vascular plants, (B) bird species, and (C) herpetofauna species along the Salt River in central Arizona. Plants were surveyed during the pre-monsoon dry season. Birds and herpetofauna were surveyed during warm seasons (March to September). 798 H. L. BATEMAN et al.Figure 5. Non-metric multidimensional scaling (NMDS) graph showing locations of seven vegetation sampling sites in each of two seasons (July and September). (A) NMDS axis 1 separates plant species (small dots) by flow permanence, and (B) NMDS axes 2 and 3 separate species by degree of urbanization. 802 H. L. BATEMAN et al.Figure 6. Non-metric multidimensional scaling (NMDS and SE ellipses) graphs for bird species (plotted as four-letter codes; Appendix 3) sampled among seven river reaches. (A) NMDS axis 1 separates bird species by season, with most waterfowl and marshland birds being abundant during winter (ellipses: fall is black, winter is grey, spring is grey dotted, and summer is black dotted). (B) NMDS axis 2 separates bird community by amount of flow, with urban dry sites most dissimilar to other reaches. 803 URBAN NOVEL WATER SOURCES

High rates of intercontinental exchange of plant species have caused scientists to ask whether floristic areas with similar environments are undergoing global homogenization. We focused on riparian forests of the urban Salt River (Sonoran Desert, USA) to ask: (1) Is the forest dominated by cosmopolitan or provincial elements? (2) Which trees planted in the irrigated cityscape have established along the river? (3) Which types of restoration interventions have favored provincial species? We surveyed tree abundance, size and vigor in belt transects among five reaches that differed in degree of restoration, and obtained data on tree species composition of the urban landscape and pre-development riparian zone. Our results reveal the urban riparian forest to have many cosmopolitan elements, owing in part to spillover of trees from the cultivated cityscape (e.g., Acacia stenophylla, Vitex agnus-castus). Global spread of some regional (Neotropical) riparian taxa (e.g., Parkinsonia aculeata, Prosopis) also has contributed to the cosmopolitan status. Yet, the forests retain a distinct regional signature. Unintentional restoration of winter floods has allowed for regeneration of Salix gooddingii, a vernally-adapted provincial pioneer, although its long-term survivorship is restricted to limited micro-sites (storm drain outfalls). Urbanization-related changes in stream hydrogeomorphology explain increases in some regional species (e.g., Washingtonia spp.) that historically were excluded from the river.Reaches restored by planting, weeding, watering, and geocountouring had the greatest abundance of provincial species and greatest floristic similarity to historic conditions.

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his classic book, the result of a 9-y research endeavor sponsored by the US Environmental Protection Agency (EPA), was recently returned to print by Blackburn Press. The EPA, newly established in 1970, had a mission to gather information on effects of environmental pollutants. The authors' primary aim was to "enable the identification of ferns and flowering plants that grow naturally in polluted and unpolluted aquatic and wetland habitats." It is an important reference for biologists, ecologists, and management personnel in determining species composition of wetland and riparian habitats within the political boundaries of Arizona, New Mexico, Oklahoma, and Texas. Some ecological information is provided, based on personal observations of the Corrells, supplemented by literature. It does not, however, pretend to be a study of the ecology of wetlands, rather it is a taxonomic treatment of species that comprise them. Nine thousand voucher specimens were collected from fieldwork undertaken in the Southwest. Distribution information is based primarily on field collections, with additional information from herbarium specimens, published monographs, revisions, floras, and other literature. The authors preface the bulky volumes with 4 introductory sections. In "Habitats Associated with Aquatic and Wetland Vascular Plants," artificial lakes, coastal and fresh water marshes, swamps, high elevation bogs, riparian zones, coastal habitats, and other wetland habitats are briefly characterized according to the dominant vegetation, sometimes discussed in a successional context. "Peculiarities and Distribution of

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