Data from: Xylem vessel traits predict the leaf phenology of native and non-native understory species of temperate deciduous forests

Non-native understorey woody species have been shown to extend leaf
display and inhabit vacant phenological niches in early spring and late
autumn when growing with native counterparts in temperate deciduous
forests across the world. Despite the potential competitive advantages,
extended leaf duration also subjects non-native species to possible
hydraulic risks associated with maintaining leaves during periods of
increased frost probability. It remains unclear how non-native species are
able to maintain xylem function within this context. Leaf phenology in
temperate deciduous trees has been shown to be a function of xylem
anatomy, with earlier bud break associated with smaller xylem vessels due
to the presumed resistance of smaller vessels to freezing-induced
cavitation. We examined relationships between leaf phenology and xylem
vessel traits across 82 native and non-native understorey deciduous woody
species common to eastern U.S. deciduous forests. We hypothesized that
non-native species possess xylem vessel traits associated with maximum
hydraulic safety during frost-prone spring and autumn leaf display without
compromising rapid growth rate. Larger metaxylem vessels in non-native
species were associated with both faster spring growth and delayed autumn
leaf fall compared to native species. Non-native species also had smaller
latewood vessel diameter, latewood vessel area percentage and a higher
proportion of solitary vessels in the entire secondary xylem cross section
compared to natives, potentially increasing their resistance to freezing-
and/or drought-induced cavitation in autumn, thus allowing for delayed
autumn leaf fall. Native and non-native species exhibited similar dates of
spring bud break and leaf emergence, consistent with similar xylem vessel
size and vessel area percentage within metaxylem and earlywood. Within
both groups, species with earlier bud and leaf emergence had a higher
total percentage of vessel area within metaxylem and earlywood. This
suggests understorey species need sufficient water to support their early
spring growth at the risk of freezing-induced cavitation. Our study
suggests xylem vessel properties, along with cross-sectional spatial xylem
vessel distribution, reflect the capacity of non-native plants to thrive
in a new environment and deepen our understanding of the physiological
mechanisms of successful invasions of non-native understorey woody plant
species.