Abstract
The distribution limits of many plants are dictated by environmental conditions and species’ functional traits. While many studies have evaluated how plant distribution is driven by environmental conditions, there are not many studies investigating xylem vessel properties with altitude, and whether these traits correlate with altitudinal distribution of tree. Here, we investigated the upper limits of distribution for ten deciduous broadleaf tree species from three temperate montane forest communities along a large elevational gradient on the north-facing slope of Changbai Mountain in Northeast China. We measured stem xylem traits associated with a species’ ability to transport water and resist freezing-induced cavitation that theoretically represent important adaptations to changes in climatic conditions along the elevational gradient. Hydraulically weighted vessel diameter (Dh) was negatively correlated with with the upper limit across the ten studied tree species; however, the correlation seems to be driven by the large differences between ring- and diffuse-porous tree species groups. The ring-porous tree species (e.g., Fraxinus mandshurica Rupr., Maackia amurensis Rupr. et Maxim., and Phellodendron amurense Rupr.) had considerably wider vessels than the diffuse-porous species and were all limited to low-elevation communities. The coefficient of variation (CV) for Dh was 0.53 among the 10 studied species, while the intraspecific analysis showed that the highest CV was only 0.22 among the 10 species. We found no evidence of a relationship between Dh and the upper limits across the seven diffuse-porous species. In contrast to elevation, hydraulic-related xylem traits had no clear patterns of change with precipitation, indicating that hydraulic functionality was largely decoupled from the influences of precipitation in the study area. This finding suggests that xylem traits are associated with altitudinal limits of species distribution, which is mostly evidenced by the contrasts between ring- and diffuse-porous species in xylem anatomy and their altitudinal distributions.
Highlights
An understanding of what drives patterns of species distributions has long been a primary goal in ecology, including the ecophysiological mechanisms involved [1,2,3]
This finding suggests that xylem traits are associated with altitudinal limits of species distribution, which is mostly evidenced by the contrasts between ring- and diffuse-porous species in xylem anatomy and their altitudinal distributions
We examined the relationships between three relevant xylem traits and upper limits of the distribution of ten native temperate deciduous broadleaf tree species along the north-facing slope of Changbai Mountain in Northeast China (Table 1)
Summary
An understanding of what drives patterns of species distributions has long been a primary goal in ecology, including the ecophysiological mechanisms involved [1,2,3]. Tolerance to abiotic stresses is a major determinant of species distributions, especially at extremes of temperature, water, and light availability [4,5,6]. Climate has been recognized as an important factor determining species’ geographic distributions [9,14]. It has been found that the growing season length, temperatures or both constrain latitudinal and elevational range limits of plant species [16,17,18]. Growing-season length constrained the upper limits of European plants along an elevational gradient [16]. Low growing-season temperatures can determine the upper limits of elevational distributions in alpine tree species [17,19]
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