The collection of physiological response data from trees can be a challenging and time-consuming task particularly in ecosystems with high species diversity. Leaf stomatal properties are more easily obtained and may inform forest water use and productivity models if they exhibit enough correlation with physiological functioning. The goals of this research were to compare stomatal properties across various tree species from three plant families (Fagaceae, Ulmaceae and Juglandaceae) growing in a bottomland forest and determine if stomatal properties correlate with physiological functioning specifically seasonal water use and its relationships with environmental drivers. Sapflow was measured in seven hardwood species (American elm, winged elm, shagbark hickory, willow oak, water oak, cherrybark oak and swamp chestnut oak) using heat dissipation sensors. Vapor pressure deficit (VPD), soil moisture, and photosynthetically active radiation (PAR) were monitored simultaneously. Seasonal water use per unit leaf area and relationships between daily water use and environmental parameters were estimated to determine the response (slope term) of sapflow to environmental drivers. Leaves were collected from tree canopies at the end of the growing season using a slingshot or shotgun. Epidermal peels were made and analyzed under a microscope to quantify stomatal density and length.
Results/Conclusions
Among species, stomatal density varied significantly, with American elm having a significantly lower density than all the oaks. Shagbark hickory also had a significantly lower stomatal density than all oak species except water oak. Stomatal lengths among species were generally similar except for American elm which had significantly longer stomata than two of the oaks and shagbark hickory. Across all tree species, stomatal density had a significantly negative correlation with seasonal water use per unit leaf area and daily sapflow responses to VPD and PAR. Stomatal lengths were not significantly correlated with any physiological variables except the response of sapflow to soil moisture which exhibited a significant positive correlation. These results show that in an area of rich tree species diversity, stomatal lengths of leaves were generally not significantly different among tree species whereas density measurements tended to be similar within tree families but significantly different across families. Based on these findings, stomatal parameters may be used to predict seasonal water use per unit leaf area and responses of water use to environmental parameters across tree species within a bottomland forest to better inform forest water use models and increase understanding of relationships between leaf structure and physiological functioning.