Allelopathic research of subtropical vegetation in Taiwan II. Comparative exclusion of understory byPhyllostachys edulis andCryptomeria japonica

Abstract

On many hillsides of Taiwan there is a unique pattern of weed exclusion byPhyllostachys edulis (bamboo) andCryptomeria japonica (conifer) in which the density, diversity, and dominance of understory species are very different. Although the physical conditions of light, soil moisture, and soil nutrients strongly favor the growth of understory in a bamboo community, the biomass of its undergrowth is significantly low, indicating that physical competition among the understory species in the bamboo and conifer communities does not cause the observed differences. However, the biochemical inhibition revealed by these two plants appeared to be an important factor. The growth ofPellionia scabra seedlings, transplanted from the study site into greenhouse pots, was evidently suppressed by the aqueous leachate of bamboo leaves but was stimulated by that of conifer leaves. The radicle growth of lettuce, rye grass, and rice plants was also clearly inhibited by the leachate and aqueous extracts of bamboo leaves but not by those of conifer leaves. Six phytotoxins,o-hydroxyphenylacetic,p-hydroxybenzoic,p-coumaric, vanillic, ferulic, and syringic acids were found in the aqueous leachate and extracts of leaves and alcoholic soil extracts ofP. edulis, while the first three compounds were absent in the extracts ofC. japonica. The phytotoxicities of extracts were correlated with the phytotoxins present in both leaves and soils. The understory species might be variously tolerant to the allelopathic compounds produced by the two plants, resulting in a differential selection of species underneath. Therefore, comparative allelopathic effects ofPhyllostachys edulis andCryptomeria japonica may play significant roles in regulating the populations of the understories.

Bamboo dominance reduces tree regeneration in a disturbed tropical forest

“…Chou and Yang (1982) suggested that bamboos interfere with the regeneration of herb species in Taiwan through production of allelopathic substances from their leaves. It is possible that this may also have reduced tree seed germination and seedling establishment in our study area.…”

Effects of adjacent land-use types on the distribution of soil organic carbon stocks in the montane area of central Taiwan

“…Allelopathic compounds released from bamboo ( Phyllostachys edulis (Carr.)) leaves can reduce the seedling abundance and species richness and then to prevent the growth of understory plants, thus reducing litter; this would also reduce the input of SOC in the bamboo forest (Chou and Yang 1982; Chang and Chiu 2015). Meanwhile, the diversity and composition of soil bacterial communities could be different in coniferous plantations and croplands, which could affect the SOC decomposition rate and then the SOC stocks.…”

Permeability - impermeability: canopy trees as biodiversity filters

“…Jones et al (1997) highlighted that each canopy tree species is a physical ecosystem engineer that creates many specific abiotic conditions beneath its crown, like specific litter accumulation, soil composition, allelochemical compounds composition, among others (for details see Zinke, 1962;Lodhi, 1977;Binkley, 1995;Denslow, 1996;Carnevale & Montagnini, 2002). Many authors have shown that such different conditions can affect germination, seed predation, pathogens attacks, tolerance, and herbivory in a species-specific way (Chou & Yang, 1982;Denslow, 1996;Cintra, 1997;Wardle & Lavelle, 1997;Metcalfe & Turner, 1998;Nicotra et al, 1999;Van Oijen et al, 2005). These species-specific biological responses can result in the selection of specific communities of seedlings, soil fauna, bacteria, micorrhiza, and pathogens composition (e.g., see Boettcher & Kalisz, 1990, Dobson & Crawley, 1994Denslow, 1996;Cintra, 1997;Ettema & Wardle, 2002).…”