Question: To what extent are species, including native and non-native species, influencing one another's distribution and abundance in the herb layer of a Minnesota oak woodland?Location: Oak woodland succeeding into a more mesic forest, on bluffland of the Mississippi River, east-central Minnesota. Methods:We collected plant composition and species cover data in 182 1.0 9 0.5 m quadrats regularly spaced on a 6-ha study grid in the oak woodland. We also recorded slope, slope position, aspect, elevation and photosynthetically active radiation (PAR) at each quadrat.Results: Presence and abundance of other plant species, topographic variables and light availability explained only a small portion of the variation (5-19%) in the distribution and abundance of individual species. The most common strongest predictor of cover for the ten most common species was species richness, with the association being positive. The non-native species, garlic mustard (Alliaria petiolata) exhibited the strongest positive association with species richness. Only one of the 45 pair-wise comparisons of the ten species resulted in a negative relationship between the species. Abundance and distribution of two species were associated with topographic features, but this accounted for much less of the variation in abundance than did species richness. Conclusion:We found little evidence that competition or any other interactions among common herb layer species, including the non-native Alliaria petiolata, play an important role in determining the abundance and the distribution of herb layer species in this oak woodland. Topographic factors may explain a small amount of the distribution and abundance patterns of a few species. But, for the most part, species are more likely to be present when other species are present, suggesting that they are simply establishing in microsites favourable to plants in general.

spatio-temporal interactions of mule and white-tailed deer in an area of sympatry in NE Washington. Ecosphere 12(11): e03813.

Among freshwater systems, coldwater habitats are among the most threatened by climate change. Examining the impacts of increasing water temperature requires the use of both traditional biomonitoring efforts and measures of ecosystem function and structure. We examined fish and macroinvertebrate communities, leaf decomposition rates, periphyton production, and ecosystem metabolism to compare two branches of a trout stream in Minnesota with differing thermal regimes. The cooler South Branch had more coldwater fish, a higher index of biological integrity for fish but a lower index for macroinvertebrates. There were no differences in leaf decomposition rates between branches, although nonnative buckthorn leaves decomposed faster than native black cherry leaves. Periphyton production was higher in the North Branch than the South Branch. Both branches had high nitrogen but low phosphorus levels. Nutrient enrichment with phosphorus enhanced periphyton production in both branches. Measures of stream metabolism, based on diurnal variation in oxygen levels, showed that both branches were heterotrophic. Despite higher periphyton production in the North Branch, gross primary production was higher in the South Branch. The bioassessment measures used in our study yielded inconsistent results, pointing to the need for multiple methods to examine and better describe potential responses to warming from climate change.

Congeneric species often share ecological niche space resulting in competitive interactions that either limit co-occurrence or lead to niche partitioning. Differences in fundamental nutritional niches mediated through character displacement or isolation during evolution are potential mechanisms that could explain overlapping distribution patterns of congenerics. We directly compared nutritional requirements and tolerances that influence the fundamental niche of mule (Odocoileus hemionus) and white-tailed deer (O. virginianus), which occur in allopatry and sympatry in similar realized ecological niches across their ranges in North America. Digestible energy and protein requirements and tolerances for plant fiber and plant secondary metabolites (PSMs) of both deer species were quantified using in vivo digestion and intake tolerance trials with six diets ranging in content of fiber, protein, and PSMs using tractable deer raised under identical conditions in captivity. We found that compared with white-tailed deer, mule deer required 54% less digestible protein and 21% less digestible energy intake per day to maintain body mass and nitrogen balance. In addition, they had higher fiber, energy, and dry matter digestibility and produced glucuronic acid (a byproduct of PSM detoxification) at a slower rate when consuming the monoterpene α-pinene. The mule deers’ enhanced physiological abilities to cope with low-quality, chemically defended forages relative to white-tailed deer might minimize potential competitive interactions in shared landscapes and provide a modest advantage to mule deer in habitats dominated by low-quality forages.