Relationship between the vertical distribution of fine roots and residual soil nitrogen along a gradient of hardwood mixture in a conifer plantation

Abstract

In forest ecosystems, understanding the relationship between the vertical distribution of fine roots and residual soil nitrogen is essential for clarifying the diversity-productivity-water purification relationship.Vertical distributions of fine-root biomass (FRB) and concentrations of nitrate-nitrogen (NO 3 -N) in soil water were investigated in a conifer plantation with three thinning intensities (Control, Weak and Intensive), in which hardwood abundance and diversity were low, moderate and high, respectively.Intensive thinning led to the lowest NO 3 -N concentration in soil water at all depths (0-100 cm) and highest FRB at shallow depths (0-50 cm). The NO 3 -N concentration at a given depth was negatively correlated with total FRB from the surface to the depth at which NO 3 -N concentration was measured, especially at shallow depths, indicating that more abundant fine roots led to lower levels of downward NO 3 -N leaching. FRB contributed positively to nitrogen content of hardwood leaves.These findings demonstrate that a hardwood mixture in conifer plantations resulted in sufficient uptake of NO 3 -N from soil by well developed fine-root systems, and translocation to canopy foliage. This study suggests that productivity and water purification can be achieved through a hardwood mixture in conifer plantations.

Essential Role of Symbiotic Microorganisms Supporting Forests in East Asia under Changing Environment

“…We also evaluated the colonization percent of mycorrhizal fungi for the seedlings of the most dominant AM (basswood: Cornus controversa) and ECM (Quercus serrata) hardwoods in both the Sugi-cedar plantation and adjacent forests dominated by ECM tree species (e.g., Q. serrata, Alnus hirsuta var. sibirica, Castanea crenata) [30,[45][46][47][48].…”

Explaining the variation in 137Cs aggregated transfer factor for wild edible plants as a case study on Koshiabura (Eleutherococcus sciadophylloides) buds

“…Each individual wild edible plant will form an unique root system to acquire nutrients in accordance with the growth environment. Previous studies have clarified that diversity in root systems enables a plant to acquire water and nutrients in forest and grassland ecosystems 18 – 20 . The variation in vertical distribution of root systems may give rise to a soil-depth dependency on the uptake of radiocesium as well as nutrients in plant species 21 – 23 .…”