Relationship between leaf vein traits of three dominant Quercus species and ecological factors in the Qinling Mountains, China

We investigated the inter- and intra-species differences of leaf vein traits of three dominant Quercus species, Q. wutaishanica, Q. aliena var. acutiserrata, and Q. variabilis of Niubeiling (subtropical humid climate) and Taohuagou (warm temperate semi-humid climate), located in the eastern and western Qinling Mountains. The nine examined leaf vein traits included primary leaf vein width, secondary leaf vein width, mean fine vein width, primary vein density, fine vein density, vein areole diameter, areole density, 3D fine vein surface area, and fine vein volume. We further elucidated the influencing mechanisms and regulatory pathways of biotic and abiotic factors on leaf vein traits. The results showed that species identity had significant effects on eight out of nine leaf vein traits except 3D fine vein surface area, while habitat had significant effects on primary leaf vein width, secondary leaf vein width, vein areole diameter, fine vein density, and areole density. Altitude had significant effects on primary vein density, mean fine vein width, vein areole diameter, fine vein density and areole density. Habitat, tree species identity, and altitude had significantly interactive effects on primary leaf vein density, 3D fine vein surface area, and fine vein volume. There were significant differences in primary leaf vein width, mean fine vein width, areole density, 3D fine vein surface area, fine vein volume, primary vein density of Q. wutaishanica between the two studied habitats, but the differences were only found in secondary leaf vein width and areole density of Q. aliena var. acutiserrata and Q. variabilis. The examined leaf vein traits were influenced both by biotic and abiotic factors, with varying effect sizes. Among the biotic factors, petiole length, leaf length and width ratio had strong effect on leaf vein traits. Among the abiotic factors, climatic and soil factors had high effect size on vein traits, with the former being higher than the latter. Leaf vein traits were affected directly by biotic factors, but indirectly by abiotic factors (soil and climatic factors) via regulating biotic factors (leaf stoichiometry and leaf phenotypic traits).

Variation in leaf vein traits of Pinaceae plants on the eastern Qinghai-Tibet Plateau, China

To explore the adaptative strategies of single-veined plants along the environmental gradient, we collec-ted leaves of 57 Pinaceae species (including Abies, Larix, Pinus and Picea) from 48 sites along a latitudinal gradient (26°58'-35°33' N) on the eastern Qinghai-Tibet Plateau. By measuring three traits of leaf vein, including vein length per leaf area, vein diameter, and vein volume per unit leaf volume, we analyzed the trade-off between vein traits and their relationship with environmental changes. The results showed no significant difference in vein length per leaf area among different genera, but significant difference in vein diameter and vein volume per unit leaf volume. There was a positive correlation between vein diameter and vein volume per unit leaf volume for all genera. There was no significant correlation of vein length per leaf area with vein diameter and vein volume per unit leaf volume. With the increases of latitude, vein diameter and vein volume per unit leaf volume significantly decreased. In contrast, vein length per leaf area did not show a latitudinal trend. Mean annual temperature was the main factor driving the variation in vein diameter and vein volume per unit leaf volume. The relationships between vein length per leaf area and environmental factors were relatively weak. These results indicated that the single-veined Pinaceae plants have a special adaptative strategy to environmental changes through adjusting vein diameter and vein volume per unit leaf volume, which is quite different from complex vein structures such as reticular veins.