Host: The Japanese Forestry Society
The area of desert and desertificated land in China is increasing by 14 thousand km2 every year. Major causes of desertification are excessive felling, grazing and agriculture, which are induced by human-activity. Greening is necessary to restore these deserted areas, and Chinese and Japanese government and NGO have achieved the artificial planting in the Loess Plateau of China so far. However, since the study about tree physiology was unsatisfactory, the "aged small trees" (poplars which repeat die-back) are often found in planting areas in the 1970s because of the lack of water. Therefore, it is very important to study about tree physiology and pick up the kinds of trees which are very drought-resistant for the purpose of selection for tree plantation. The measurement of stable-carbon isotope (d13C) is very useful to estimate the water-use efficiency of C3 plant, and the study of stable-carbon isotope have produced good results in the selection of the kinds of crop plant which are very drought-resistant. Thus, the objective of this study is to research drought-resistant character of trees along with gradient of precipitation in the Loess Plateau of China and to estimate the kinds of planting trees which are appropriate to each area. The correlation between ring width, stable carbon isotope and climate data are obtained using tree samples taken from the Loess Plateau of China. There was not good correlation between ring width and precipitation or temperature, and it is considered that the formation of tree rings are affected by factors other than climate condition. On the other hand, there is high correlation between stable carbon isotope of latewood and precipitation or temperature, and it is thought that the stomatal aperture is highly influenced by climate condition. Thus, it is suggested that it is useful to estimate drought-resistance of tree species on the basis of the relation between stable carbon isotope and climate data.
