1Preface
In the earth, volcanic activity has come to occur in places almost without break since at least 3.5 billion years
ago. At the present time about 800 terrestrial volcanoes are recognized as active. Whenever we think of theactivity of volcanoes, what first comes to mind will be the vastness of volcanic fumes and lava flows. A large
number of disaster records from past volcanic activities show, for example, a giant volcanic fume reaching aheight of several tens of kilometers and very fine volcanic ash drifting in the sky for a long time, resulting inserious damage to photosynthesis of plants on the ground due to the obstruction of sunlight and weaker intensity
reaching the ground. Furthermore, many violent volcanic activities accompanied by earthquakes have beenreported to affect people dwelling near volcanoes, causing great loss of life.
Once volcanic activities, however, terminate and become calm for a long time there occur many biologicalactivities such as plants growing on thick volcanic ash deposits, and they help develop the volcanic ash, including
other pyroclastic materials, into volcanic ash soils. Volcanic ash soils under temperate, humid climates havecharacteristic properties such as very fine particle size, large specific surface area and distinctively black soil colorthat are rarely found in soils derived from other parent materials. In 1949, J. Thorp and G.D. Smith firstrecognized these as a soil group in a global system of soil classification and gave them the name of Ando soils,
coined from the Japanese term for dark soils. At a later time, Ando soils were renamed as Andisols, andAridisols was added as one of 11 Orders, which are ranked by highest categories in the world soil classification
system of Soil Taxonomy.
The total distribution of Andisols worldwide is estimated to account for more than 0.8% of the earth’s surface,covering more than 124 × 104 km2. Comparing the acreage of Andisols worldwide with those of soils derived
from other parent materials, one discovers they are not widely distributed, in fact, but considerably more narrowly.
In spite of the relatively smaller acreage of Andisols in the world, most of these soils are located on stable, flatland surfaces and have become a very important agricultural resource, though some Andisols require some soil
amelioration due to undesirable characteristics for crop production such as low soil reaction originating from
active aluminum. Furthermore, I believe that another background factor for including Andisols in the highest
categories of the world soil classification system comes from the many studies with detailed data carried out on
the distribution, nature, properties and management of these soils. In Japan, New Zealand, Chile and somehumid temperate or tropical regions Andisols have a considerably wide distribution and importance to agriculturaldevelopment in these regions. For example, in Japan Andisols cover about one-sixth of the total land surface,and occupy 27% of all agricultural lands, with 51% of the acreage used as a soil medium for upland crop and fruit
tree production.
This special issue was planned and produced in consideration of the important background mentioned above.

Satoshi Matsumoto