Species Composition, Size-Class Structure, and Diversity of the Lienhuachih Forest Dynamics Plot in a Subtropical Evergreen Broad-Leaved Forest in Central Taiwan

Abstract

The Lienhuachih Forest Dynamics Plot (FDP), measured 500 m by 500 m square, is located in central Taiwan. The collected data, followed a unified method adopted for the worldwide FDP network, were analyzed for floristic composition, size-class structure, and species diversity. In total, the censused trees and shrubs belonged to 144 species in 86 genera and 39 families. The most dominant families were the Fagaceae, Lauraceae, Rubiaceae, Euphorbiaceae, and Melastomataceae. In total, 153268 (6131 ha^(-1)) individuals were recorded, and the total basal area was 34.77 m^2 ha^(-1). Of the 144 species, the most abundant were Randia cochinchinensis and Blastus cochinchinensis. Pasania nantoensis had the highest basal area (8.38%), followed by Engelhardtia roxburghiana (8.12%) and Schefflera octophylla (7.23%). Calculation of the importance value (IV, incorporating relative values of abundance and basal area) showed that R. cochinchinensis, B. cochinchinensis, S. octophylla, Cryptocarya chinensis, and E. roxburghiana were the most dominant species with the highest IV values in the plot. The sum of the 30 top species' IV reached 83.06% of the whole. Although the 1st 2 species were understory and very dominant due to the large number of individuals, certain numbers of rare species however increased the floristic diversity in the plot. Based on the species composition, the forest is characteristic of the Machilus-Castanopsis forest zone of Taiwan, with certain dominant understory species and possessing 2 pioneer species in the major canopy composition. For the size-class structure, 102 (each with total stems ≥ 25) species showed 4 patterns of size-class distribution: L-shaped, inverse J-shaped, fluctuating, and bell-shaped. The former 3 patterns in a total of 98 species, including a great number of small-sized individuals, imply that most current species in this study site can display good recruitment with rich resources of saplings. The woody plant richness of the Lienhuachih FDP is the highest among low-elevation FDPs in Taiwan. Compared to other Center of Ttropical Forest Science forest dynamics plots on islands, Fisher's alpha diversity (ha^(-1)) index of the subtropical Lienhuachih FDP was similar to that of the Luquillo FDP in Puerto Rico but much lower than that of other FDPs in the tropics.