Conifers and broadleaved trees coexist in temperate forests and are expected to differ in partitioning strategies between leaf and stem.
In a study published in Tree Physiology, researchers from China and Wageningen University compared canopy branches between conifers and broadleaved trees in a natural, temperate forest. They studied the partitioning strategies through functional balances within branches by quantifying allometric relationships between the leaf area and stem tissue areas.
They found that conifers maintain functional water balance between stem and leaves by compensating their low hydraulic conductivity with a wider xylem area. Broadleaved trees maintain functional carbon balance not by creating a larger phloem area per leaf area, but possibly by having more or larger conductive cells in phloem.
Those balances represent the coordination of water loss in the leaves versus water transport in the xylem and storage in the ray parenchyma in the stem, and the coordination between carbon gain in the leaves versus sugar transport in the phloem and storage in the ray parenchyma.
The large ray area in broadleaved trees may hint to their role in carbon storage during winter, while the low ray area in conifers may be a compromise for maximizing water transport.
“These partitioning strategies may lead to a similar xylem growth rate of canopy branches between conifers and broadleaved trees”, said Dr. CHEN Yajun, a correspondence author of the study.
“We suggest that the allocation between leaf area (carbon gain) and phloem (carbon transport) and ray (carbon and water storage) area could be important indicators in understanding adaptation of different life forms or phenology”, said Chen Yajun.
CHEN Yajun Ph.D
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China