Intraspecific variation in morphological traits of root branch orders in Chamaecyparis obtusa

Abstract

We aimed to clarify the intraspecific variation in the morphological traits of branch orders under different soil conditions in Chamaecyparis obtusa (Siebold & Zucc.) Endl. We investigated the morphological traits of branch orders, based on 16,351 individual roots that were dissected from 12 intact fine root systems, up to a diameter of 2 mm at three C. obtusa stands. We also measured the concentrations of soil carbon, nitrogen, and inorganic nitrogen. The intact fine root systems up to the diameter of 2 mm had branched into between five and seven orders. The diameter of first- to fourth-order roots and the lengths of second- and third-order roots were significantly different among the three stands. The morphological traits of lower order (first to third) roots correlated with soil inorganic nitrogen concentrations, but higher order (fourth to sixth) roots correlated with soil carbon concentrations. We clarified the possible ranges of intraspecific variation in the morphological traits of root branch orders within C. obtusa. Both the lower and higher orders of the intact fine root systems were tightly related to the surrounding soil conditions.