AoB Plants最新文献

[This corrects the article DOI: 10.1093/aobpla/plae034.].

Abstract. Using herbarium specimens spanning 133 years and field-collected measurements, we assessed intraspecific trait (leaf structural and stomatal) variability from grass species in the Great Plains of North America. We focused on two widespread, closely related grasses from the tribe Paniceae: Dichanthelium oligosanthes subsp. scribnerianum (C₃) and Panicum virgatum (C₄). Thirty-one specimens per taxon were sampled from local herbaria from the years 1887 to 2013 to assess trait responses across time to changes in atmospheric [CO₂] and growing season precipitation and temperature. In 2021 and 2022, the species were measured from eight grasslands sites to explore how traits vary spatially across natural continental precipitation and temperature gradients. Δ¹³C increased with atmospheric [CO₂] for D. oligosanthes but decreased for P. virgatum, likely linked to increases in precipitation in the study region over the past century. Notably, this is the first record of decreasing Δ¹³C over time for a C₄ species illustrating ¹³C linkages to climate. As atmospheric [CO₂] increased, C:N increased and δ¹⁵N decreased for both species and %N decreased for D. oligosanthes. Across a large precipitation gradient, D. oligosanthes leaf traits were more responsive to changes in precipitation than those of P. virgatum. In contrast, only two traits of P. virgatum responded to increases in temperature across a gradient: specific leaf area (increase) and leaf dry matter content (decrease). The only shared significant trend between species was increased C:N with precipitation. Our work demonstrates that these closely related grass species with different photosynthetic pathways exhibited various trait responses across temporal and spatial scales, illustrating the key role of scale of inquiry for forecasting leaf trait responses to future environmental change.

Cotyledons play an important role in early seedling establishment. However, relative to primary leaves, cotyledons tend to have a different investment-on-return strategy. To detect the potential differences in the mass (M) versus area (A) scaling relationships between cotyledons and primary leaves in different light environments, a total of 75 Acer platanoides seedlings were sampled at an open site (n = 52; light availability: 74 ± 5 %) and a shaded site (n = 23; light availability: 4.2 ± 1.2 %). Reduced major axis regression protocols were used to fit the M versus A scaling relationships of primary leaves and cotyledons. The bootstrap percentile method was used to test the significance of the differences in the scaling exponents of M versus A between the two light environments. The scaling exponents of cotyledons at both two sites, as well as the primary leaves at the shade site, were greater than unity indicating 'diminishing returns', while the scaling exponent of primary leaves at the open site was smaller than unity indicating 'increasing returns'. The data collectively indicated light-dependent shifts in support investments and differences in the function of cotyledons and primary leaves. Average leaf structural traits displayed significant differences between the two light environments in accordance with the premium in enhancing photosynthetic capacity in high light and light interception in low light. Although the trait responses to light availability were similar for primary leaves and cotyledons, primary leaves were more responsive to light availability, indicating lower plasticity of cotyledons in response to light levels. These results advance our understanding of the roles of cotyledons and primary leaves in the life history of seedlings in different forest light environments.