Carbon‐cycling changes during regeneration of a decinduous broadleaf forest after clear‐cutting II. Aboveground net production

Abstract

AbstractGrowth and death rates of aboveground plant parts were measured in a mature forest and four different‐aged deciduous broadleaf forests regeneratede after clear‐cutting, with special reference to rates for woody parts (stems and branches) of different diameters (ø) in rerms of the pipe model theory (Shinozaki et al., 1964). The total biomass increment of woody parts of trees higher than 1.3 m varied within a range of 2.1‐4.6 ton ha−1 yr−1, the increase beingdue largely to the growth of canopy trees exposed to direct sunlight. Biomass increments of small (ø<1 cm) and medium (1≤ø<5 cm) woody parts were negligibly small except in the youngest forest, and changes in aboveground woody biomass with forest age after clear‐cutting mainly resulted from accumulation of large (5 cm<ø) woody parts of canopy trees. Biomass loss of trees due to death and grazing increased with forest age from 4.0 to 8.3 ton ha−1 yr−1. Recovery of leaf and small wood falls was observed at the early stage of regeneration, while large wood falls increased during regeneration. Flower and fruit fall was markedly higher in the mature forest than in the other four forest types. Mortality of woody parts became higher with forest age and was 20, 5.0 and 0.46% yr−1 for small, medium and large parts, respectively, at the mature stage. Aboveground net production of the forest was in therange 7.6‐13.3 ton ha−1 yr−1 with the undergrowth vegetation lower than 1.3 m being 0.4‐1.4 ton ha−1 yr−1. Production recovered rapidly at an early stage of regeneration and was highest in mature forest.