Growth Response of Acer Truncatum to Periodic Changes in the Water Supply at Different Stages of Its Annual Growth Period

摘要

Although numerous studies have examined the effects of water stress on trees, few of them have compared the response of trees to drought at different stages of their annual growth period. We conducted a simulated drought experiment to test the sensitivity of Acer truncatum saplings to variations in the soil water content during different stages of their annual growth period. The goals of this study were to i) investigate the adaptability of Acer truncatum to fluctuations in soil water content, ii) determine which stage of the annual growth period of the tree was most sensitive to drought stress, iii) develop an irrigation plan that would optimise the growth of Acer truncatum saplings in water-limited areas, and iv) investigate the feasibility of matching the species' sensitivity and tolerance to drought stress at different growth stages with the unique climate features of a given area. The pot experiment was conducted in a rain-free shelter using one-year old Acer truncatum saplings. The annual growth period of the saplings was divided into three growth stages by means of a logistic curve according to the height growth of Acer truncatum. Drought stress during the different growth stages was simulated by adjusting the soil water content in the pots according to a second-order regression general rotation and combination design that included five different soil water contents: 100 %, 87.84 %, 70 %, 52.16 % and 40 % of field capacity. The results showed that although Acer truncatum is a species with strong drought resistance, its height growth and basal diameter growth were very sensitive to the timing of water stress, but the most sensitive stages was different, for height growth it was in the early growth stage and for basal diameter growth it was in the accelerating growth stage. The optimum soil moisture for roots growth of Acer truncatum was 74.05 % of field capacity in the earlygrowth stage, 84.89 % of field capacity in the accelerating growth stage, and 44.93 % in the late growth stage. In particular, there was a proliferation in the growth of fine roots at this moisture level. Total biomass production as well as the biomass production of roots, leaves and branches+stems varied according to the timing of water stress. The optimum soil moisture content for dry matter production was 60.78 % of field capacity in the early growth stage, 64.62 % of field capacity in the accelerating growth stage, and 73.37 % in the late growth stage. A statistical model was obtained by the graded approach of multiple indexes. The model can be used to predict and control the growth effects under the conditions of different water supply at different stages of the annual growth period.