Cool-temperate Deciduous Forest Research Articles

東北日本の気候的水収支について

In the present study, the distribution maps of climatic water balance components were provided by climatic year method. The water balance was evaluated by “bookkeeping procedures” for each year based on the Thornthwaite's system (1948) as shown in Table 1. The data used here were monthly precipitation amount and monthly mean temperature recorded at 321 stations over the northeastern part of Japan during the period 1967-1982.The distribution of the mean annual total of potential evapotranspiration (PET) is shown in Figure 1. The local differences of PET can be seen among basins and plains. The amount of PET is greater than 720 mm in the Kanto Plain and the Echigo Plain, Central Japan, and less than 540 mm in the southeastern part of Hokkaido.Figure 2, Figure 3 and Figure 4 show the distribution of mean annual water surplus, mean annual water deficit and mean annual number of dry months, respectively. The distribution pattern of water surplus (Fig. 2) shows orographic effects of mountain ranges facing the Japan Sea ; the large amounts are observed along the mountains and the small amounts are observed over basins and plains on the Pacific side of the mountains. As shown in Figure 3 and Figure 4, the distribution pattern of water deficit and dry month is almost the same. The dry month is defined here as the month in which the monthly potential evapotranspiration exceeds the monthly precipitation. The features of these distribution are more complicated than that of water surplus. Large amounts of water deficit are appeared in some basins and plains blocked by mountains to the south.We would like to study the significance of water balance components as environmental elements in the future. In this study, an interpretation was given for the geographical distribution of beech trees (Fagus crenata) in Hokkaido. AOYAMA (1986b) showed that the PET indicates a similar thermal indicator for vegetation to Kira's warmth index (1945). The border between cool-temperate deciduous forest and subarctic coniferous forests runs along the western foot of the central mountains in Hokkaido, where annual amount of PET is about 560 mm. The northern limit of beech trees is located further south, in the Kuromatunai lowland, where the PET is about 600 mm. KIRA (1971 a, 1976) interpreted that the difference of location of these borders was caused by the advance of beech trees from south during th period since the last retreat of the ice. In addition to this interpretation, we can indicate climatic reasons to set the northern limit of the beech trees. At the root of the Oshima Penninsula, north of the Kuromatunai lowland, region with the amount of PET less than 560 mm spreads and reaches to the Pacific coast. Moreover, a large amount of water deficit is recognized along the coast of the Japan Sea. In general, the beech trees dominate in the cool-temperate deciduous forest under the condition of wetter maritime climate. Consequently, it can de considered that the thermal condition as indicated by PET on the coast of the Pacific side and the moisture condition as indicated by water deficit on the Japan Sea coast make a barrier for the advance of beech trees toward the north.

Late-Quaternary dynamics of temperate forests: Applications of paleoecology to issues of global environmental change

Paleoecological evidence recently summarized from 162 fossil-pollen sites in eastern North America provides new insights concerning the nature and rate of response of temperate forest ecosystems to late Pleistocene and Holocene environmental changes. Across this subcontinental region (25°N to 60°N; 50°W to 100°W), temperate forests have changed in composition, location and area occupied in adjustment to major episodes of climatic cooling and warming during glacial-interglacial cycles of the Quaternary. Forest taxa have migrated differentially, reflecting their individualistic life-history characteristics, dispersal and competitive abilities, and tolerance thresholds to environmental changes, as well as the geographic distribution of corridors and barriers to plant migration. Gradient analysis and ecological ordination of paleovegetational data illustrate that: (1) both positions and breadth of major vegetational ecotones have shifted latitudinally over the past 20 ka; (2) good modern analogues exist for certain full-glacial warm-temperate and boreal forests; (3) during the transition from Pleistocene to Holocene conditions, mixed conifer-northern hardwoods forests, spreading across newly deglaciated terrain, lacked good analogues within the modern vegetation; and (4) most cool-temperate deciduous forest communities north of 35°N developed in the Holocene. Forest clearance and cultivation by Native Americans along principal riverways resulted in a transformation from natural to cultural landscapes during the mid- and late Holocene intervals. Fragmentation of temperate forests accelerated with the onset of EuroAmerican settlement and technologic developments after the Industrial Revolution.

Late-Quaternary Dynamics of Temperate Forests: Applications of Paleoecology to Issues of Global Environmental Change

Paleoecological evidence recently summarized from 162 fossil-pollen sites in eastern North America provides new insights concerning the nature and rate of response of temperate forest ecosystems to late Pleistocene and Holocene environmental changes. Across this subcontinental region (25°N to 60°N; 50°W to 100°W), temperate forests have changed in composition, location and area occupied in adjustment to major episodes of climatic cooling and warming during glacial-interglacial cycles of the Quaternary. Forest taxa have migrated differentially, reflecting their individualistic life-history characteristics, dispersal and competitive abilities, and tolerance thresholds to environmental changes, as well as the geographic distribution of corridors and barriers to plant migration. Gradient analysis and ecological ordination of paleovegetational data illustrate that: (1) both positions and breadth of major vegetational ecotones have shifted latitudinally over the past 20 ka; (2) good modern analogues exist for certain full-glacial warm-temperate and boreal forests; (3) during the transition from Pleistocene to Holocene conditions, mixed conifer-northern hardwoods forests, spreading across newly deglaciated terrain, lacked good analogues within the modern vegetation; and (4) most cool-temperate deciduous forest communities north of 35°N developed in the Holocene. Forest clearance and cultivation by Native Americans along principal riverways resulted in a transformation from natural to cultural landscapes during the mid- and late Holocene intervals. Fragmentation of temperate forests accelerated with the onset of EuroAmerican settlement and technologic developments after the Industrial Revolution.

CALCULATED THERMAL INDEX MAPS FOR THE RECONSTRUCTION OF PAST VEGETATION SINCE THE LAST GLACIAL AGE IN JAPAN

Two kinds of indices, the warmth index (WI) and the coldness index (CI) were proposed by Lira (1945, 1948) to correlate the geographical distribution of vegetation zones with the thermal condition. This Lira's concept is considered to be useful for the reconstruction of past vegetation during the last 20, 000 years. The distribution maps of WI and CI are made on the basis of the mean monthly temperature for the period from 1921 A. D, to 1950 at 860 weather stations distributed over Japan (Figs. 1 and 2). In this paper, five distribution maps are presented as the representative temperature conditions during the past 20, 000 years. These maps show the thermal limitation of the vegetation zones for five periods when the mean annual tempetature are -7°C, -5°C, -3°C, -1°C and +2°C at different from the present temperature, respectively. The distribution map of WI and CI at the time when the mean annual temperature is 7°C lower than the present (Fig. 3) roughly represents the thermal limitation of the forest types at the maximum glacial period (about 20, 000_??_18, 000 years B. P.). Based on this map, Hokkaido should be covered with the tundra and subalpine conifer forests. The subalpine conifer forest also covers the Tohoku and Chubu districts. While, most of southwest Japan should be covered with the cool-temperate deciduous forest. Evergreen oak-laurel forests are only found in the lowland in southern Kyushu, Tanegashima and Yakushima islands. The second map for the case of 5°C lower than the present (Fig. 4) approximately shows the thermal limitation at the late glacial period (about 13, 000_??_10, 000 years B. P.). This map indicates that subalpine conifer forests spread in Hokkaido. While mountainous regions in the Tohoku and Chubu districts are still under the subalpine conifer forest, the forest in the lowlands should be changed into the cool-temperate deciduous one. Evergreen oak-laurel forests invade into the southern coastal area of the Kii Peninsula. It is notable that warm-temperate deciduous forests should appear in western Kyushu, Setouchi and Osaka Bay areas. The third map for the case of 3°C lower than the present (Fig. 5) is roughly correlated with the condition at the early Holocene period. The thermal limitation of the cool-temperate deciduous forest appears in the Ishikari Plain, Hokkaido. The the main part of Tohoku and Chubu districts are covered with cool-temperate deciduous forests. Warm-temperate deciduous forests extend a wide area in northern Kanto Plain, marginal part of Nobi Plain, and coastal lowlands along the western part of the Japan Sea. The northern limit of the evergreen oak-laurel forest should attain to the southern Kanto Plain in the Pacific Ocean side, while it is located at Matsue City in Shimane Prefecture in the Japan Sea side. The fourth map for the case of 2°C higher than the present (Fig. 6) approximately shows the thermal limitation at the Hypsithermal time (about 7, 000_??_6, 500 years B. P.). Forests in Hokkaido should be changed into the cool-temperate deciduous one. Inland basins of the Tohoku and Chubu district are covered by the warm-temperate deciduous forest. Evergreen oak-laurel forests spread over the central and southern part of Japan. The northern limit of this forest is located at Kuji City, Iwate Prefecture in the Pacific Ocean side and at the Lake of Jusan, Aomori Prefecture in the Japan Sea side. The fifth map for the case of 1°C lower than the present (Fig. 7) roughly represents the condition at the latest Jomon and early Yayoi periods (about 3, 000_??_2, 000 years B. P.) . This map is similar to the present potential natural vegetation maps which were made by Honda (1912), Horikawa (1968), Yoshioka (1973) and, Miyawaki et at. (1975), although there are some differences between two types of the maps.