title: Intraspecific variation in fine root respiration and morphology in response to in situ soil nitrogen fertility in a 100-year-old Chamaecyparis obtusa forest.
abstract: Soil N fertility has an effect on belowground C allocation, but the physiological and morphological responses of individual fine root segments to variations in N availability under field conditions are still unclear. In this study, the direction and magnitude of the physiological and morphological function of fine roots in response to variable in situ soil N fertility in a forest site were determined. We measured the specific root respiration (Rr) rate, N concentration and morphology of fine root segments with 1-3 branching orders in a 100-year-old coniferous forest of Chamaecyparis obtusa. Higher soil N fertility induced higher Rr rates, root N concentration, and specific root length (SRL), and lower root tissue density (RTD). In all fertility levels, the Rr rates were significantly correlated positively with root N and SRL and negatively with RTD. The regression slopes of respiration with root N and RTD were significantly higher along the soil N fertility gradient. Although no differences in the slopes of Rr and SRL relationship were found across the levels, there were significant shifts in the intercept along the common slope. These results suggest that a contrasting pattern in intraspecific relationships between specific Rr and N, RTD, and SRL exists among soils with different N fertility. Consequently, substantial increases in soil N fertility would exert positive effects on organ-scale root performance by covarying the Rr, root N, and morphology for their potential nutrient and water uptake.
authors.affiliation: Kansai Research Center, Forestry and Forest Products Research Institute, Nagai-Kyutarou, Momoyama, Fushimi, Kyoto, 612-0855, Japan. makita701@gmail.com.|Graduate School of Agricultural Science, Kobe University, Kobe, 657-8501, Japan. makita701@gmail.com.
authors.forename: Naoki
authors.initials: N
authors.lastname: Makita
authors.affiliation: Kansai Research Center, Forestry and Forest Products Research Institute, Nagai-Kyutarou, Momoyama, Fushimi, Kyoto, 612-0855, Japan.|Graduate School of Environmental Studies, Nagoya University, Nagoya, 464-8601, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Hirano
authors.affiliation: Graduate School of Agricultural Science, Kobe University, Kobe, 657-8501, Japan.
authors.forename: Takanobu
authors.initials: T
authors.lastname: Sugimoto
authors.affiliation: Kansai Research Center, Forestry and Forest Products Research Institute, Nagai-Kyutarou, Momoyama, Fushimi, Kyoto, 612-0855, Japan.
authors.forename: Toko
authors.initials: T
authors.lastname: Tanikawa
authors.affiliation: Graduate School of Agricultural Science, Kobe University, Kobe, 657-8501, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Ishii
mesh_terms: D029780:Chamaecyparis / Q000254:growth & development* / Q000502:physiology; D005298:Fertility; D065928:Forests; D007564:Japan; D009584:Nitrogen / Q000032:analysis*; D018517:Plant Roots / Q000254:growth & development / Q000502:physiology; D012987:Soil / Q000737:chemistry*
chemical_list: D012987:Soil; D009584:Nitrogen
keywords: Fertility gradient; Nitrogen; Root CO2 efflux; Root tissue density; Specific root length