Estimating density and biomass of canopy arthropods in coniferous plantations: an approach based on a tree-dimensional parameter

Abstract

The number of individuals and biomass of canopy arthropods were estimated in coniferous plantations of Cryptomeria japonica and Larix kaempferi in central Japan. Foliage and arthropod samples were collected from the canopies of three sample trees at each site by seasonal branch-clipping at intervals of 2 weeks from May to November 1997. The numbers of all arthropods per unit foliage mass ranged from 30 to 100 kg −1 dry weight on C. japonica and 150–18 900 on L. kaempferi. L. kaempferi also greatly exceeded C. japonica in arthropod biomass, 700–32 700 ( L. kaempferi) vs. 100–600 ( C. japonica) (mg fresh weight kg −1 foliage dry weight), averaging 4900 vs. 300. The major groups were Hemiptera, lepidopteran larvae, and hymenopteran (mainly sawflies) larvae as herbivores, Coleoptera (including a few guilds), and spiders as predators, accounting on average for >80% at both sites. Spiders were the dominants on C. japonica, while lepidopteran and hymenopteran larvae and Hemiptera were relatively more important on L. kaempferi in both number and biomass. The foliage biomass of individual sample trees was estimated using allometric regressions on a tree-dimensional parameter, D B, diameter at the height just below the lowest living branch. The mean value for total arthropods per tree during the survey period was: by number, 2200–5800 ( C. japonica) and 6300–26 000 ( L. kaempferi); biomass (mg fresh weight), 13 000–32 000 ( C. japonica) and 36 000–106 000 ( L. kaempferi). The study presented an approach for estimating the biomass of canopy arthropods in a forest at a given time of year on an individual-tree- and a per unit-area basis, using the mean estimate of arthropod biomass from sample trees and a dimensional parameter for trees in a plot of given area via the estimation of foliage biomass of individual trees using allometric regression.