The vast variety of leaf morphology are important manifestation of plant functional diversity, and simple- and compound-leaf forms are prominent traits of leaf morphology of trees. Compound-leaved tree species are usually pioneer (photophilous) species and have higher potential productivity (e.g. higher radial stem growth rates) compared with simple-leaved species. However, little research has been done to explain the underlying physiological mechanisms.
In order to uncover the physiological mechanisms that determine the high potential productivity of compound-leaved tree species, a team of researchers from the Institute of Applied Ecology (IAE) of the Chinese Academy of Sciences (CAS) selected five compound-leaved and five simple-leaved tree species in a forest in Changbai Mountain, Northeast China, and measured a total of 14 functional traits of these species in detail.
The compound-leaf form is associated with high stem water transport efficiency, and the compound-leaved species with ring-porous wood have even higher ‘rate of water flux through shoots and high photosynthetic carbon assimilation rate’, the researchers found.
They also found that most compound-leaved species in northern China have ring-porous wood. According to their speculation, compound-leaved species with diffuse-porous wood are more likely to be the evolutionary losers because their limited hydraulic conductance and lower carbon assimilation rate cannot compensate for the carbon loss caused by annual dropping of large rachises; while compound-leaved species with ring-porous wood that are commonly found today, become the evolutionary winners because of their higher potential productivity.
However, tree species with ring-porous wood are very sensitive to freeze–thaw-induced embolism, which makes a majority of compound-leaved tree species distribute mainly in lower altitudinal ranges in temperate zones.
The study for the first time gives a physiological explanation (i.e. from the perspective of tree hydraulics) for the high productivity hypothesis associated with compound-leaved species, which helps understanding the environmental adaptability of these species. The study also provides important experimental data and theoretical guidelines for planting such tree species in their suitable geographical regions and ecological conditions.
The study entitled “Compound leaves are associated with high hydraulic conductance and photosynthetic capacity: evidence from trees in Northeast China” has been published in Tree Physiology.
The research is financially supported by the Outstanding Youth Science Fund of the National Natural Science Foundation of China.