- RESTORING PRAIRIE POTHOLE WETLANDS - 261 Applied Vegetation Science 9: 261-270, 2006 © IAVS; Opulus Press Uppsala. Abstract Question: Do regional species pools, landscape isolation or on-site constraints cause plants from different guilds to vary in their ability to colonize restored wetlands? Location: Iowa, Minnesota, and South Dakota, USA. Methods: Floristic surveys of 41 restored wetlands were made three and 12 years after reflooding to determine changes in local species pools for eight plant guilds. The effect of landscape isolation on colonization efficiency was evaluated for each guild by plotting local species pools against distance to nearby natural wetlands, and the relative importance of dispersal vs. on-site constraints in limiting colonization was explored by comparing the local species pools of restored and natural wetlands within the region. Results: Of the 517 wetland plant taxa occurring in the region, 50% have established within 12 years. The proportion of the regional species pool represented in local species pools dif- fered among guilds, with sedge-meadow perennials, emergent perennials and floating/submersed aquatics least represented (33-36%) and annual guilds most represented (74-94%). Colo- nization-to-extinction ratios suggest that floating/submersed aquatics have already reached a species equilibrium while sedge-meadow and emergent perennials are still accumulating species. Increasing distance to nearest wetlands decreased the proportion of the regional species pool present in local pools for all guilds except native annuals and woody plants. The maximum proportion predicted, assuming no distance con- straint, was comparable to the lowest-diversity natural wetlands for most perennial guilds, and also lower than what was achieved in a planted, weeded restoration. Conclusions: Abiotic constraints seem to limit the coloniza- tion of floating/submersed aquatics into natural or restored wetlands, whereas all other guilds are potentially constrained by dispersal or biotic factors (i.e. competition from invasive species). Using species pools to evaluate restoration progress revealed that immigration potential varies considerably among guilds, that local species richness does not necessarily corre- spond to immigration limitations, and that some guilds (e.g. sedge-meadow perennials) will likely benefit more than others from being planted at restoration sites. Keywords: Invasive plant; Landscape fragmentation; Plant colonization; Plant dispersal; Plant community assembly; Res- toration; Succession; Vegetation management. Nomenclature: Anon. (2004). Restoring prairie pothole wetlands: does the species pool concept offer decision-making guidance for re-vegetation? Galatowitsch, Susan M. Department of Horticultural Science, 305 Alderman Hall, University of Minnesota, St. Paul, MN 55108, USA; Fax +1 6126244941, E-mail galat001@umn.edu Introduction In spite of extensive efforts to restore ecosystems worldwide, reversing land-use degradation is often an uncertain endeavour with variable success. Success is least likely within extensively fragmented landscapes on highly modified sites – the kinds of places where restorations are most crucial for improving environmen- tal quality (e.g. Hobbs 2003). Resilience against restora- tive change may stem from feedbacks that develop between biota and the abiotic environment during deg- radation, such as altered fuel loads, trophic interactions, or propagule pressure favouring spread of invasive spe- cies (Suding et al. 2004). Consequently, effective re- storative change will more likely emerge from imple- menting landscape-level strategies than site-based rem- edies. Developing these strategies requires an under- standing of landscape recovery processes that is gener- ally lacking (Holl et al. 2003). In particular, it is impor- tant to understand why, in many cases, species present in landscapes (i.e. species pools) fail to reassemble in restorations at the rate and to the extent predicted from intact natural communities. Regardless of the nature of land use degradation, all restorations need mechanism(s) to reassemble biota. With increasing fragmentation, fewer propagule sources remain, and those sources have decreased connectivity to restoration sites. In some cases (e.g. tall-grass prai- ries), site-based strategies of planting and/or species reintroduction are adopted to compensate for the pre- sumed lack of dispersal efficiency. In other situations, also typified by high levels of fragmentation (e.g. prairie wetlands), biota are not actively reintroduced because these organisms are presumed likely to return if given enough time (Galatowitsch & van der Valk 1996a, b). Both strategies (planting vs. colonization) have poten- tially deleterious outcomes. Planting or re-introductions can result in arbitrary species composition and unin- tended changes to local gene pools (e.g. Hufford & Mazer 2003); low colonization efficiency in fragmented landscapes potentially skews species composition to favour organisms tolerant of landscape modifications.