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Arundo donax L., commonly known as giant reed, is promising biomass feedstock that is also a notorious invasive plant in freshwater ecosystems around the world. Heretofore, the salt tolerance of A. donax had not been quantified even though anecdotal evidence suggests halophytic qualities. To test whole-plant and leaf level responses, we established a pot experiment on 80 scions propagated from an A. donax population that has naturalized on the shore of the San Francisco Bay Estuary. To quantify growth and physiological responses to salinity (NaCl), A. donax scions were divided into eight treatments and grown for 60 days across a range of salinities (0-42 dS m À1). Classic growth analysis showed >80% reduction in overall growth at the highest salinities. Yet, there was zero mortality indicating that A. donax is able to tolerate high levels of salt. Declining photosynthesis rates were strongly correlated (R 2 > 0.97) with decreasing stomatal conductance, which was in turn closely related to increasing salinity. Leaf gas exchange revealed that stomata and leaf limitations of carbon dioxide were three times greater at high salinities. Nonetheless, even when salinities were 38-42 dS m À1 A. donax was able to maintain assimilation rates 7-12 lmol m À2 s À1 . Further, by maintaining 50% relative growth at salinities 12 dS m À1 A. donax can now be classified as 'moderately salt tolerant'. A. donax leaf gas exchange and wholeplant salt tolerance are greater than many important food crops (i.e. maize, rice), the bioenergy feedstock Miscanthus 9 giganteus, as well as some uncultivated plant species (i.e. Populus and Salix) that are indigenous in regions A. donax currently invades. The results of this study have implications for both agronomists wishing to expand A. donax to fields dominated by saline soils, and for others who are concerned about the spread of A. donax with altered stream hydrology or sea-level rise.

Across landscapes, riparian plant communities assemble under varying levels of disturbance, environmental stress, and resource availability, leading to the development of distinct riparian life‐history guilds over evolutionary timescales. Identifying the environmental filters that exert selective pressures on specific riparian vegetation guilds is a critical step in setting baseline expectations for how riparian vegetation may respond to environmental conditions anticipated under future global change scenarios. In this study, we ask: (1) What riparian plant guilds exist across the interior Columbia and upper Missouri River basins? (2) What environmental filters shape riparian guild distributions? (3) How does resource partitioning among guilds influence guild distributions and co‐occurrence? Woody species composition was measured at 703 stream reaches and each species' morphological and functional attributes were extracted from a database in four categories: (1) life form, (2) persistence and growth, (3) reproduction, and (4) resource use. We clustered species into guilds by morphological characteristics and attributes related to environmental tolerances, modeling these guilds' distributions as a function of environmental filters—regional climate, watershed hydrogeomorphic characteristics, and stream channel form—and guild co‐existence. We identified five guilds: (1) a tall, deeply rooted, long‐lived, evergreen tree guild, (2) a xeric, disturbance tolerant shrub guild, (3) a hydrophytic, thicket‐forming shrub guild, (4) a low‐statured, shade‐tolerant, understory shrub guild, and (5) a flood tolerant, mesoriparian shrub guild. Guilds were most strongly discriminated by species' rooting depth, canopy height and potential to resprout and grow following biomass‐removing disturbance (e.g., flooding, fire). Hydro‐climatic variables, including precipitation, watershed area, water table depth, and channel form attributes reflective of hydrologic regime, were predictors of guilds whose life history strategies had affinity or aversion to flooding, drought, and fluvial disturbance. Biotic interactions excluded guilds with divergent life history strategies and/or allowed for the co‐occurrence of guilds that partition resources differently in the same environment. We conclude that the riparian guild framework provides insight into how disturbance and bioclimatic gradients shape riparian functional plant diversity across heterogeneous landscapes. Multiple environmental filters should be considered when the riparian response guild framework is to be used as a decision‐support tool framework across large spatial extents.

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Bioenergy development can offer beneficial ecological and economic synergies through the expansion of ecological restoration projects. Such synergies are demonstrated by means of a case study conducted in central Washington State, where a 52.4-ha ecological restoration site on the Yakama Reservation generated 34 megagrams (Mg) of invasive tree biomass per hectare, costing $988 ha -1 . A geospatial model of transportation costs estimated that extracted invasive tree biomass can generate revenues throughout 1103 803 ha when delivered to a proposed bioenergy facility in White Swan, Washington, providing 53 000-180 000 Mg of biomass per year for several decades. Thermochemical analyses revealed that the elevated nitrogen, sulfur, and ash content in two prolific invasive trees -Russian olive (Elaeagnus angustifolia) and salt cedar (Tamarix spp) -will limit demand for either of these invasive species. We compare our regional data to national estimates, and show the broader potential for expanding ecological restoration activities and biomass supplies through the revenues generated by the sale of invasive tree wood-waste into bioenergy markets. Ecological restoration and bioenergy technologies LL Nackley et al. 536 www.frontiersinecology.org

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Expanding populations, the impacts of climate change, availability of arable land, and availability of water for irrigation collectively strain the agricultural system. To keep pace and adapt to these challenges, food producers may adopt unsustainable practices that may ultimately intensify the strain. What is a course of technological evolution and adoption that can break this cycle? In this paper we explore a set of technologies and food production scenarios with a new, reduced-order model. First the model is developed. The model combines limitations in the sustainable water supply, agricultural productivity as a function of intensification, and rising food demands. Model inputs are derived from the literature and historical records. Monte Carlo simulation runs of the model are used to explore the potential of existing and future technologies to bring us ever closer to a more sustainable future instead of ever farther. This is the concept of a moving sustainability horizon (the year in the future where sustainability can be achieved with current technological progress if demand remains constant). The sustainability gap is the number of years between the present and the sustainability horizon. As demand increases, the sustainability horizon moves farther into the future. As technology improves and productivity increases, the sustainability horizon is closer to the present. Sustainability, therefore, is achieved when the sustainability horizon collides with the present, closing the sustainability gap to zero. We find one pathway for water management technology adoption and innovation that closes the sustainability gap within the reduced-order model’s outputs. In this scenario, micro-irrigation adoption, minimal climate change impacts, reduced food waste, and additional transformative innovations such as smart greenhouses and agrivoltaic systems are collectively needed. The model shows that, in the absence of these changes, and continuing along our current course, the productivity of the agricultural system would become insufficient in the decade following 2050.