Total biomass and biomass production of Pinus roxburghii trees growing in all-aged natural forests

Abstract

Detailed morphometric measurements for individual trees in an age series (16-128 years) of P. roxburghii Sarg were carried out. The dry weight of each component of the tree increased with age and total aboveground biomass in a 128-year-old tree was 1939 kg. Satisfactory allometric equations relating biomass of different components with circumference at breast height (cbh) and square diameter × height (d²h) were developed. The error in estimates was lower when the independent variable included tree height. Within an individual tree the biomass of bole increased downwards and the canopy of the tree was concentrated towards the upper part of the tree. The intercomponent biomass relationships were also significant, and the resulting allometric equations carried less error than the equations using cbh as the independent variable. The cumulative dry matter produced by a sample tree within its lifetime was much greater than the respective current biomass. The largest proportion of the production was accounted for by the tree crown and fine roots, while the largest biomass resided in the bole. The maximum current biomass increment was attained at the age of 39 years. The mean annual production increased with age except for bole and root system where it first increased and then attained a constant value after 61 years. The relationships of bole and shoot production per annum to total leaf area and fine roots for different age periods indicated a significant spurt of activity during 36-39 years and a secondary limited spurt during 97-103 years in the life history. The production of nonphotosynthetic components was significantly related with the leaf area and with foliage production.