Retention of forested buffers around streams following forest cutting operations is a common managementtechnique used to protect aquatic resources and conserve the surrounding ecosystem services. Species richness,or α-diversity, is commonly used as an indicator of the effects of forestry management although it provides verylittle information about those effects on ecosystem processes and function. Functional diversity links speciestraits and ecosystem function incorporating species diversity, community composition, and functional guild andis more suitable to investigate the direct and indirect effects of forestry on ecosystem function. We sampledspiders and vascular plants in buffered and unbuffered stream-forest systems in southern Sweden and used atrait-based approach to assess the effects of buffer size and environmental variables on functional diversity. Weused structural equation modeling (SEM) to explore the effects of buffer size and condition on spider and vascularplant diversity. We found no effect of buffer size on the functional richness or functional redundancy for spidersor vascular plants. Buffer size had a slight effect on the α-diversity of spiders within small buffers and fullyforested sites but the effect was small. Other buffer variables including canopy closure, buffer density, bareground coverage, and soil fertility had direct effects on spider and vascular plant functional diversity. The maindriver of functional richness was α-diversity, but our SEM analysis illustrated other environmental variablesworking jointly to drive functional diversity. Using a trait-based approach, we showed that forested buffers havea minimal overall impact on spider and vascular plant functional diversity. However, it is important to maintainhigh levels of α-diversity to preserve and promote both spider and plant functional richness in production forestsand we suggest that forest management conserves and encourages high levels of α-diversity to increase overallfunctional diversity.

Stream ecosystems are reliant on the reciprocal exchange of terrestrial and aquatic energy subsides to maintain a productive and stable food web. Land use around streams can have strong effects on the size and availability of resource subsidies for stream and riparian predators such as fish and spiders. A common forestry technique around streams is the establishment of forested buffers to protect aquatic and riparian ecosystems from upland disturbances. Buffer size may determine prey abundance, richness, and spatial extent of prey reach into both the aquatic and terrestrial systems. To test the effects of forested buffers subsidy direction, we explored the carbon and nitrogen stable isotope signatures of brown trout (Salmo trutta), Tetragnathidae and Lycosidae spiders, and their aquatic and terrestrial prey sources around twelve streams in southern Sweden. For both predator groups, buffer presence showed no effect on resource subsidy source. We found that both brown trout and spiders are significantly reliant on terrestrial sources of prey for their diets in the fall. To support the terrestrial subsidy into small streams it is vital to maintain ecologically functional riparian zones by conserving complex surrounding habitats that optimize habitat and both terrestrial and aquatic prey diversity.

As top consumers and generalist predators, spiders are ideal organisms to study food webs and complex ecological functions using stable isotopes. Most researchers use whole-body samples to analyze stable isotope ratios in spiders. Spiders can regrow lost legs and produce multiple molts during a life cycle, and nonlethal sampling utilizing legs and molts may provide a useful alternative to whole-body sampling especially in larger bodied or threatened species. Furthermore, removing spider abdomens and thus leftover prey in the gut contents may provide a more accurate isotopic value. We tested the hypothesis that the delta N-15, delta C-13, or delta H-2 isotopic values in spider legs are reliable proxies for spider prosomas, abdomens, or whole bodies. We used laboratory-reared large-bodied spiders (Pterinochilus murinus) and field-collected Lycosidae to compare lethal and nonlethal tissue isotopic values. We found that nonlethal samples of spider legs and molts are acceptable alternatives to lethal whole-body samples to determine delta C-13 and delta N-15 stable isotope signatures. Nonlethal samples are not suitable proxies for whole-body samples to determine delta H-2 isotopic values. Using nonlethal leg or molts samples in stable isotope investigations of spiders will allow researchers to promote conservation efforts and study threatened species while ensuring accurate and repeatable results.