Abstract
Research Highlights: Bottomland oaks receive less attention than upland species, however their adaptations to flooding and summer water stress will extend our understanding of the oak genus and links between physiology and leaf anatomy. Background and objectives: Determining links between leaf anatomy and physiology can aid in parameterizing dynamic global vegetation models for oak systems, therefore we sought to (1) compare leaf anatomic, nutrient, and physiological parameters for bottomland oaks differing in flood tolerance, (2) determine correlations across parameters and determine which anatomic and nutrient parameters best predict photosynthetic capacity metrics, and (3) compare these data with reported literature values for oaks across the globe. Materials and Methods: We measured CO2 response curves (A/Ci) on leaves from Nuttall, Shumard, swamp chestnut, water and white oak seedlings planted in the Southeastern United States (US) and estimated stomatal size and density, epidermal cell size, vein density, leaf mass per area (LMA) and nitrogen (N) concentrations. Principal component analysis among these leaf anatomic and nutrient parameters was used to determine the best predictors of photosynthetic parameters including Rubisco-limited carboxylation rate (VCmax) and electron transport limited carboxylation rate (Jmax). Results: We found that although physiological parameters were similar, flood-tolerant oaks had lower leaf N concentrations and larger, more infrequent stomata than less flood-tolerant species. Leaf epidermal properties were correlated with N concentrations and a principal component capturing this correlation as well as principal components correlated with mesophyll conductance and leaf carbon concentrations were found to best explain variation in VCmax and Jmax. These Southeastern US oaks exhibited similar leaf physiological parameters and LMA as oaks reported in the literature but differed in leaf epidermal and stomatal properties as well as leaf N concentrations increasing the reported range of these parameters within the oak genus. Conclusions: Therefore, leaf anatomy and nutrient parameters as opposed to physiology differed across flood tolerance and between bottomland oaks and broader literature values.
Highlights
The oak genus is widespread throughout much of North America providing benefits such as timber production and wildlife resources
In terms of species comparisons, we found that physiological parameters (VCmax, Jmax, Ball–Berry parameter, photosynthetic nitrogen use efficiency (PNUE)) and whole leaf anatomical parameters (LMA, vein density) did not vary in relation to flood tolerance of these measured southern bottomland oak species
This research highlights the importance of leaf structural parameters in discerning significant differences across species as well as the explanatory power of variables including epidermal cell size and density and leaf C concentrations in explaining physiological functioning in terms of
Summary
The oak genus is widespread throughout much of North America providing benefits such as timber production and wildlife resources. Oaks have been described as having a stress tolerant physiological strategy and compete well under conditions of drought stress [1], increased fire frequency [2] and low nutrient availability [3]. Bottomland floodplain forests tend to be found in the South Central and Southeastern United States (US) on the Gulf and Atlantic Coastal Plains [9]. These sites are characterized by the extent and duration of seasonal flooding with differing species assemblages occurring along a gradient in elevation and flooding. Differences in flooding tolerance exist with overcup oak (Quercus lyrata Walter) and Nuttall oak (Q. texana Buckley) occurring at the swamp edge, water oak (Q. nigra L.)
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