Clarifying soil nitrogen (N) acquisition by the same plant species with increasing age will further improve understanding of the importance of age in nutrient cycling in terrestrial ecosystems.
A series of monoculture rubber plantations were established to produce rubber latex driven by economic profit in Xishuangbanna in the past decades. This provides an opportunity to examine how age affects N uptake by rubber.
Researchers from Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to examine how root uptake rates and preferences for organic and inorganic N forms change with plantation age. They selected rubber plantations of 7, 16, 24, 32 and 49 years of age in the same region with similar topography.
To test the N uptake patterns of rubber trees of different age, a mixture of NH4+, glycine and NO3− was employed. The researchers investigated the uptake of NH4+, NO3− and glycine to evaluate differences in uptake rates by rubber trees of increasing age.
They found that the rubber trees used NH4+ as the dominant N source independent of age, in the order of NH4+ > glycine > NO3−. This indicates that rubber trees had a strong preference for NH4+, when roots were provided with equal concentrations of all three N forms.
They also observed significant shifts in the uptake rates of NH4+, NO3−or glycine with tree age. Young rubber trees had higher NH4+ and lower glycine preferences than adult trees. Older rubber trees utilized organic N in the form of glycine from soil solution as an important N source.
These findings indicate that N uptake patterns shift with age of rubber trees and might be influenced by their changes in N requirements, by N losses via rubber tapping or shifts in carbon allocation to mycorrhizal symbionts.
The study entitled “Age alters uptake pattern of organic and inorganic nitrogen by rubber trees” has been published online in Tree Physiology.
Contact
XU Xingliang Ph.D
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
E-mail: xuxingl@hotmail.com
