Estimating the production and mortality of fine roots using minirhizotrons in a Pinus densiflora forest in Gwangneung, Korea

Abstract

The aim of this study was to estimate fine root production (FP) and fine root mortality (FM) at 0-10, 10-20, and 20-30 cm soil depths using minirhizotrons in a 75-year-old Pinus densiflora Sieb. et Zucc. forest located in Gwangneung, Korea. We developed the conversion factors (frame cm(-2)) of three soil depths (0.158 for 0-10 cm, 0.120 for 10-20 cm, and 0.131 for 20-30 cm) based on soil coring and minirhizotron data. FP and FM were estimated using conversion factors from March 26, 2013 to March 2, 2014. The annual FP and FM values at the 0-30 cm soil depth were 3200.2 and 2271.5 kg ha(-1) yr(-1), respectively. The FP estimate accounted for approximately 17 % of the total net primary production at the study site. FP was highest in summer (July 31-September 26), and FM was highest in autumn (September 27-November 29). FP was positively correlated with seasonal change in soil temperature, while FM was not related to that change. The seasonality of FP and FM might be linked to above-ground photosynthetic activity. Both FP and FM at the 0-10 cm depth were significantly higher than at 10-20 and 20-30 cm depths, and this resulted from the decrease in nutrient availability with increasing soil depth. The minirhizotron approach and conversion factors developed in this study will enable fast and accurate estimation of the fine root dynamics in P. densiflora forest ecosystems.