Effects of Soil Gas Composition on Transpiration and Leaf Conductance of Bamboos

Abstract

The growth rate of bamboo plants is considered to be higher than other tree species and thus bamboo is a promising plant for afforestation if the plantation forests can be well managed. Recently bamboo plants have invaded mountainous areas and expelled indigenous plant species in Japan. Therefore we need to develop methods for regulating the growth of bamboos. We examined the effects of soil gas composition on transpiration and leaf conductance of bamboos in order to obtain the basic data for establishing a method for controlling the environment in the root zone. The experiments were conducted with Phyllostachys pubescens in a bamboo forest and with Phyllostachys aurea grown in pots in a growth chamber. Transpiration rates of leaves and leaf conductance were measured with a porometer after the treatment suppressing soil aeration by covering the soil surface in the forest and the pots with plastic film. Concentrations of O2 and CO2 in the soil were measured with O2 and CO2 sensors, respectively. The O2 concentration in the soil decreased from 21% to 19% and the CO2 concentration increased from 0.05% to 2.0% two days after the treatment. The transpiration rate and leaf conductance decreased by 25% a day after the treatment. Therefore, the gas exchange of bamboo leaves and thus the growth of bamboo plants can be controlled by controlling soil aeration.