Biometric-Based Net Primary Production (NPP) and the Effects of a Masting Event on Production Allocation in a Secondary Lucidophyllous Forest in Central Japan

Lucidophyllous (evergreen broad-leaved) forests are the dominant forests in human-dominated subtropical/warm-temperate regions in East Asia. Biometric-based estimates of net primary production (NPP) were conducted in a secondary lucidophyllous forest on Mt. Kinka (35°26′ N, 136°47′ E) near the northern limit of their distribution in central Japan for three years, including the masting event. The forest stand mainly consists of Castanopsis cuspidata (Thunb.) Schottky and Cleyera japonica Thunb. in the canopy and subtree layers, respectively. In 2018, the total NPP of the masting year was 14.53 ± 2.03 ton ha⁻¹ yr⁻¹, including woody NPP (above: 2.63 ± 0.35 ton ha⁻¹ yr⁻¹; below: 0.57 ± 0.08 ton ha⁻¹ yr⁻¹), foliage NPP (4.07 ± 0.23 ton ha⁻¹ yr⁻¹), reproductive NPP (4.81 ± 0.77 ton ha⁻¹ yr⁻¹), and fine root production (P_fr) (2.46 ± 1.84 ton ha⁻¹ yr⁻¹). P_fr and belowground production comprised 16.9% and 20.9%, respectively, of the total NPP. The nut production of C. cuspidata in 2018 (4.31 ± 0.75 ton ha⁻¹ yr⁻¹) was significantly higher than that in 2017 (0.77 ± 0.13 ton ha⁻¹ yr⁻¹) and 2019 (0.23 ± 0.06 ton ha⁻¹ yr⁻¹). No significant change was observed for the three years of foliage NPP and total NPP without P_fr. However, the woody NPP in 2018 (3.20 ± 0.43) was lower than in 2017 (5.37 ± 0.33 ton ha⁻¹ yr⁻¹) and 2019 (4.71 ± 0.38 ton ha⁻¹ yr⁻¹). This suggests that nut production in the masting years compensated by decreasing woody production in the Castanopsis forest.