Researchers study volcanic ash soils in Japan and loess in China to determine the time-dependent durability of macropore forms, or pore systems formed by roots (root-formed pores). The results of their study revealed continuous and dense development of pore systems formed by roots from the surface layer to deeper layers. The calculated length of durability of the pore systems formed by the roots was 100,000 years for the deposited volcanic ash layers of Tokachi, Hokkaido, 160,000 years for the volcanic ash layers of Mt. Tengutai, Hachinohe, 320,000 years for the loess layers of Lantian, China, and 720,000 years for the volcanic ash layers of Mt. Iwate, Iwate-kawaguchi. The volcanic ash layers of Tokachi, Hokkaido, dating back to the Late Pleistocene and the last ice age were found to be highly degraded. Moreover, the partial disappearance of the pores was determined to have occurred in the volcanic ash layers dating back from the early part of the Middle Pleistocene to the early part of the Early Pleistocene. Yet, researchers have not completed their work on the durability of pore systems formed by roots in the consecutive strata effected by climatic changes. The investigation was conducted at an outcrop near the beach of Tanesashi, Hachinohe, located in the northeastern part of Japan (40 degrees 30' 10" north latitude, 141 degrees 36' 30" east longitude). This was the loam layer of the Hachinohe pumice (developed about 10,000 to 14,000 years ago), or about 1.5 m below it's surface, to a depth of about 8.5 m. This loamy layer contains 12 volcanic ash layers, among which the Toya volcanic ash formation at a depth of 6.4 m, dating back to about 105,000 to 110,000 years ago, is the key for age identification. The relationship between the identified age of the layer and the climatic changes were determined from the change curve of the oxygen isotopic ratio with the Tengutai volcanic ash formation as the reference. The geologic date of the layer belongs to the last ice age cycle, ranging from the Late Pleistocene, before the post-glacial age (13,000 years ago), to the early part of the Middle Pleistocene. Soil samples were taken consecutively from 27 layers at every 30 cm from the Hachinohe pumice layer to a depth of 8.5 m in early October 2002. The durability and change of the pore systems formed by roots in the volcanic ash soil at Tanesashi, Hachinohe, with soil strata ranging from the Late Pleistocene (relatively recent in geological age) to the early part of the Middle Pleistocene,were distributed, in each stage of growth, leading us to identify the time-dependent durability of the pore systems formed by roots. The results are summarized as follows with respect to the changes in the pore systems formed by the roots(regarding generation, maintainability and functionality): X-ray stereoscopic images revealed the continuous presence of a clear-cut caterpillar pore systems formed by roots at a high density throughout the 12 layers from the Hachinohe pumice layer to a depth of 8.5 m. 1. The pore systems formed by roots are in the preservation period following the generation period. 2. The stage of time-dependent durability of the pore systems formed by roots in each layer is from the early to the middle stage of the durability period. 3. The continuity of the pore systems formed by roots is shown to have a clear-cut continuity as it goes deeper and bears small changes. 4. The functionality of the pore systems formed by roots is that of water permeability by larger pores in the vertical direction and that of water retention by micro pores in the lateral direction. 5. The facies index of the pore systems formed by roots shows thick wood-like pores of the cold period of the ice age and thin herbal pores of the warm period of the ice age, therefore suggesting the vegetation of an ancient environment. The study revealed that the pore systems formed by roots in the volcanic ash layer at Tanesashi, Hachinohe in the eras from the Late Pleistocene to the early part of the Middle Pleistocene were intact, with small changes in quality and a very slow progress of deterioration, and were in the early or middle part of the durability period with a clear-cut continuity of pores. The Influences of the climatic changes in the Late Pleistocene on pore systems formed by the roots are identified in pore sizes and modes of distribution. 1)SATO.2000-2001 Grant-in-aids for Scientific Research (C)Research Report, 1-67(2002). 2)SATO et al..Japanese Journal of Soil Science and Plant Nutrition proceedings, 47(2001). 3)Tokunaga et al..Japanese Society of Pedology 42,88-96(1998). 4)Tokunaga et al..Japanese Society of Irrigation,Drainage and Reclamation Engineering 187,59-68(1997). 5)Sase et al.. Japan Association for Quaternary Research 31,131-146(1992).