2016 Volume 50 Issue 1 Pages 15-26
In the Kyoen River Delta, trees including Koyo poplar (Populus euphratica) had been extensively logged for building materials and fuel wood for military use from the 1940s to the 1980s. As a result, Koyo poplar has been designated as an endangered species. Here, we determined the current distribution and recovery trend of Koyo poplar based on Landsat data obtained in 1977, 1990, 2000 and 2010. We also attempted to identify areas suitable for planting. Koryu tamarisk (Tamarix ramosissima) is a pioneer species along rivers and provides a protective habitat for Koyo popular, which later becomes the climax species. A geographic information system (GIS) analysis showed that, as of 2010, human disturbance of the forest had almost ended and vegetation was recovering. Succession to Koyo poplar had started in some areas. A buffering analysis by GIS showed that it would take at least 450 years for Koyo poplar to recover in Koryu tamarisk forests. That means that the recovery would take 10 times as long as the period of disturbance. However,previous studies have shown that mixed planting of Koyo poplar and other tree species improves the growth of Koyo poplar seedlings and that root cutting improves bud blush from roots. The regeneration period for Koyo popular could be shortened by planting Koyo poplar in Koryu tamarisk forests along rivers and by root cutting in Koyo poplar forests that had stopped regenerating.
