Meeting Abstract
Boreal Forest Warming at an Ecotone in Danger (B4WarmED) is a manipulative open-air experiment in northern Minnesota, addressing the potential for climate warming to alter tree function and species composition at the boreal-temperate forest ecotone. The goal of this study was to compare plant traits of tree species from three groups (invasive temperate, native temperate, and native boreal) grown under two temperature regimes (ambient and warmed 3.4 °C) to determine whether an aggressive invasive species is differentially sensitive to climate warming than common native species. We present data collected over four years on tree seedling growth, leaf emergence and senescence, leaf gas exchange rates, and leaf nutrients of 11 species. Native boreal species showed a decline in growth under the warming treatment, while native temperate and the invasive temperate (Rhamnus cathartica) species generally responded positively to warming. However, the invasive R. cathartica showed the largest increase in growth. This growth response to warming by the invasive species does not appear to be driven by differences in growing season length, as all species extended their growing season in the warmed plots. Specific leaf area (SLA) of both native groups did not vary among treatments, but SLA of R. cathartica declined significantly in the warming treatment, causing increased area-based leaf nitrogen concentrations. Area-based photosynthetic rates followed a similar pattern, increasing in the warming treatment for R. cathartica, but remaining stable or declining in the two native groups. Our growth and leaf trait results suggest that invasive R. cathartica may outgrow and outcompete the native species in northern Minnesota under climate change.
