Cost-effectiveness of leaf energy and resource investment of invasive Berberis thunbergii and co-occurring native shrubs

Photosynthetic energy gain and biomass energy and resource investment represent trade-offs between potential enhancements and limitations to plant productivity, respectively. We compared these characteristics in the exotic invasive Berberis thunbergii DC. with that of co-occurring natives Kalmia latifolia L. and Vaccinium corymbosum L. in a northeastern United States forest. We hypothesized that invasion by B. thunbergii could be facilitated by a lower leaf construction cost (CC) and reduced leaf nitrogen content (N) relative to photosynthetic rate (A) and maximum photosynthetic capacity (A max ), which would afford it greater energy-use efficiency (EUE) and nitrogen-use efficiency (NUE), and maximums of these variables (EUE max and NUE max ), compared with native shrubs. Although B. thunbergii and K. latifolia exhibited similar peak-season A and A max , EUE, EUE max , and NUE max were greater in B. thunbergii, which exhibited lower leaf CC and density. In contrast, EUE, EUE max , NUE, and NUE max did not differ between B. thunbergii and V. corymbosum given their similar A, A max , and area-based leaf CC and leaf N. Considered with leaf phenology, our results suggest two distinct physiological mechanisms could influence B. thunbergii invasion. Specifically, deciduous B. thunbergii exhibited greater cost-effectiveness than evergreen K. latifolia, while a longer payback time for photosynthetic energy gain could offset instantaneous similarities in cost-effectiveness of earlier leafing B. thunbergii and deciduous V. corymbosum.