Kazue Fujiwara

Warm-Temperate Deciduous Forests: Concept and Global Overview

The zonal vegetation of [humid] warm-temperate regions is normally considered to be evergreen broad-leaved forest, such as the “laurel forests” of East Asia, southern Brazil, and much of New Zealand. Observing the vegetation of Japan and other parts of East Asia, however, Kira noted in 1949 that some deciduous Quercus species do not occur in either the cool-temperate (deciduous) or the subtropical (evergreen) zone and eventually proposed the concept of warm-temperate deciduous forest, composed especially of Quercus species. These species occur in the drier climates of interior Honshū, especially around Nagano, where summers are warm enough but winters are too cold for evergreen broad-leaved forest. This concept also fits parts of middle-eastern China and lowland Korea, where most of the same Quercus species also occur. Analogous warm-temperate deciduous forests beyond Asia appear to include, inter alia, the Quercus-Carya forests of interior southeastern North America and the Quercus pubescens forests of southern Europe. In East Asia, some main deciduous species are Quercus variabilis, Q. serrata, Q. aliena and Q. dentata, all occurring on mesic to dry sites. These species also form the canopy of secondary deciduous forests that are eventually replaced by the zonal warm-temperate evergreen broad-leaved (laurel) forests. In eastern North America, some Quercus and other deciduous taxa (including Fagus) have wide north-south ranges, but deciduous Q. falcata, Q. nigra, and others have distinctly southern ranges. This southern area is in the warm-temperate zone and has mean winter temperatures significantly higher than in East Asia (albeit with unusual lower extremes). Warm-temperate deciduous forest analogs around the Northern Hemisphere can be identified from climatic considerations but also from phytosociological analysis (and ordinations) based on releve data, suggesting that this is a consistent sub-zonal forest type.

Evergreen Broad-Leaved Forests in Japan and Eastern North America: Vegetation Shift under Climatic Warming

Evergreen broad-leaved forests include “laurel” forests, evergreen Fagaceae forests, tropical and temperate rainforests, and some nonFagaceae sclerophyll forests. Laurel forests are especially well developed in humid warm-temperate to subtropical areas of East Asia and occur topogenically (moist/wet depressions) in the sandy, drier coastal plain of the southeastern USA. Evergreen Fagaceae forests also occur in both regions, but with more mesomorphic, laurophyll character in East Asia and more semi-sclerophyll character in the southeastern USA. Both warm-temperate regions have secondary forests which are deciduous and more closely related to the adjacent typical-temperate deciduous forests. Under global warming (even without drying), weedy and other highly mobile species from warmer areas can be expected to invade northward. Species of the warm-temperate evergreen broad-leaved forests, however, may also expand northward, invading the adjacent deciduous forest regions. In Japan, Quercus myrsinaefolia has recently expanded inland, but a relationship to climatic warming has not yet been verified. In the southeastern USA, no such northward or inland expansion has been documented, but this could be related to a substrate discontinuity and/or to the more erratic nature of the North American climatic limit for evergreens.

Eine Erweiterte Gliederung der Oxycocco-Sphagnetea

Arbeiten aus der Arbeitsstelle fur Theoretische und Angewandte Pflanzensoziologie, Todenmann (95)

Phytosociological Study of Quercus variabilis Forest in Warm-Temperate China

Deciduous Quercus forest is a typical forest type in the warm-temperate zone of China (sensu sinico). Among different kinds of deciduous Quercus forest, Quercus variabilis forest is the important, major forest type in the southern part of this area. In order to clarify the phytosociological characteristics of Q. variabilis forest in warm-temperate China, this study surveyed 12 sites and recorded 54 releves, using the Braun-Blanquet (1964) methodology (Fujiwara 1987, 1997); a syntaxonomical scheme for Q. variabilis forest was also made. The classification result showed that there were five communities, five associations grouped into three alliances, an order Quercetalia variabilis ord. nov. and the class Quercetea variabilis class. nov. This can be subdivided into: (1) a Lonicero standishii-Quercion variabilis all. nov., consisting of an Acer grosseri-Quercus variabilis comm. nov., a Junipero formosanae-Quercetum variabilis ass. nov., and a Vitici negundo heterophyllae-Quercetum variabilis ass. nov., on very poor soil over granite; (2) a Carpino turczaninowii-Quercion variabilis all. nov., composed of Rhododendron mariesii and Melica radula communities, and a Viburno mongolicae-Quercetum variabilis ass. nov., which can always be found at higher elevation on south-facing aspects; and (3) a Pistacio chinensis-Quercion variabilis all. nov., which includes a Pteroceltio tatarinowii-Quercetum variabilis ass. nov., an Alangio chinensis-Quercetum variabilis ass. nov., and Vitex negundo and Zelkova schneideriana communities, usually occurring on limestone at relatively low elevation. De-trended correspondence analysis (DCA) was performed to distinguish the spatial distribution characteristics of the different communities. The result showed that the communities classified are mostly related to elevation and climatic variables such as mean annual temperature, mean annual precipitation, and mean temperature of the warmest and coldest months. This indicates that, even within the same forest type, Quercus variabilis forest shows very different floristic composition and environmental characteristics across the warm-temperate zone of China.

Rehabilitation of tropical forests from countryside to urban areas

Tropical forests have been reduced drastically in the last ten years. Tropical forests in the Philippines, Thailand and the Malay Peninsula have disappeared particularly rapidly. The Philippines, Indonesia and Thailand stopped exporting tropical timber in the 1980s. Some nearly natural tropical forests remain in some parts of the national park area. Even national parks do not have real virgin forests. Most are younger natural forests and/or substitute vegetation such as dry dipterocarp forests, or Macaranga secondary forests, Trema orientalis scrub, etc. Montane tropical forests still barely remain above 800 or 1000 m. In the lowland the original landscape has completely changed from mangrove and lowland tropical forests to urban and rural landscapes.

Phytosociological Study of Pteroceltis tatarinowii Forest in the Deciduous-Forest Zone of Eastern China

Pteroceltis tatarinowii is a Chinese endemic tree species belonging to the family Ulmaceae. This species likes high-calcium soil, can tolerate drought and barren environmental conditions, has strong rooting ability, and is regarded as one of the important tree species for vegetation restoration on limestone mountains in the warm-temperate zone (sensu sinico) of eastern China. But existing Pteroceltis tatarinowii forests have survived mostly in small areas, and so far there have been only rare phytosociological studies of Pteroceltis tatarinowii forest reported. To clarify the phytosociological characteristics of Pteroceltis tatarinowii forest in eastern China, this study selected five sites in the main distribution areas of Pteroceltis tatarinowii forest and recorded 28 vegetation samples, using Braun-Blanquet methodology. Field data were also collected for Quercus forests in the same region (including Quercus variabilis forest and Quercus acutissima forest), in order to determine the position of Pteroceltis tatarinowii forest in the hierarchical syntaxonomic system of deciduous broad-leaved forests. Data on Pteroceltis tatarinowii forest were classified by tabular comparison and summarized in a synoptic table, along with typical Quercus forests occurring in the same region. The different geographical distributions of Pteroceltis tatarinowii forest and deciduous Quercus forests were demonstrated by de-trended canonical correspondence analysis (DCCA). The compared results show that Pteroceltis tatarinowii forest in eastern China can be recognized as a new alliance in the Quercetea variabilis class, named Moro australis-Pteroceltidion tatarinowii. This new alliance can be subdivided into two associations (i.e. Isodo rubescens-Pteroceltido tatarinowii ass. nov. and Pteroceltido tatarinowii-Quercetum variabilis) and one community (i.e. Platycladus orientalis-Pteroceltis tatarinowii community). The results of DCCA show that suitable environmental ranges of Pteroceltis tatarinowii forest are narrower than for Quercus forests and the different geographical distributions can be explained by the geographical and climate conditions. Compared with Quercus forests, Pteroceltis tatarinowii forest is more likely to occur in relatively harsh habitats at low altitudes, on steep cliffs or hillsides, on dry slopes with much exposed rock, and on calcium-rich limy soils. The constituent species of Pteroceltis tatarinowii communities are not many, the average number being about 34, because most species are unable to tolerate unfavorable dry, rocky, or barren environments. The structure of Pteroceltis tatarinowii communities is relatively simple, but many seedlings and clonal ramets of Pteroceltis tatarinowii appeared in the understory, so natural regeneration of Pteroceltis tatarinowii populations is better in forests. The structure and species composition of Pteroceltis tatarinowii forests showed significant differences along with environmental temperature and humidity. The community types of Pteroceltis tatarinowii forest in the study area change from Isodo rubescens-Pteroceltido tatarinowii to a Platycladus orientalis-Pteroceltis tatarinowii community, and then to Pteroceltido tatarinowii-Quercetum variabilis, with increasing environmental temperature and decreasing humidity (from north to south).

Introduction: Why Warm-Temperate Deciduous Forests?

Warm-temperate deciduous forests would seem to be an enigma. In the various global (and globally aware) bioclimatic zonation systems, warm-temperate climates are generally construed as humid temperate climates with warm summers, mild winters (no lasting snow cover), and evergreen broad-leaved forest as the zonal (i.e. climatic potential) vegetation type. This is the general conceptualization both in global treatments of vegetation and climate, as by Rubel (1930), Schmithusen (1968), and Walter (1968, 1970, 1985); and in regional systems, such as by Kira and others for East Asia (cf Kira 1945, 1949, 1977, 1991; Suzuki 1953; Miyawaki 1967). Such zonal evergreen broad-leaved forests occur in East Asia (often called “laurel forests”) as well as in southern Brazil, northern New Zealand, parts of eastern Australia, in montane belts of tropical Asia (and even the Canary Islands), and, where topography permits, in small areas of the warm-temperate southeastern USA. Thermally, some mediterranean climates are also warm-temperate and may carry evergreen broad-leaved forests, albeit with sclerophyll rather than laurophyll foliage.

Character of Warm-Temperate Quercus Forests in Asia

The concept of warm-temperate deciduous forest was re-proposed, from mid-temperate forest (Mid-Zone of Tanaka 1887), by Kira (1949, 1991, 2011), based on climatic data and values of his Warmth and Coldness Indices. T. Suzuki (1966) recognized this as the intermediate-temperate zone (Tsugion sieboldii). What kind of forests are warm-temperate forests in Asia? This chapter treats deciduous forests in eastern Asia, especially deciduous Quercus forests, and compares them, based on forest composition and climate data, with more typical temperate and cool-temperate Quercus forests. Quercus serrata forests, in most of eastern Asia, occur in drier, warmer climates than do Fagus forests and in climates that are colder in winter than the evergreen forest area. In Japan such forests are composed mainly of deciduous Quercus serrata, Q. acutissima, Q. variabilis, Castanea crenata, Carpinus tschonoskii, and C. laxiflora. This kind of forest occurs mainly as secondary forest preceding evergreen broad-leaved forest, in both Japan and Korea. Q. serrata and Q. variabilis forests occur naturally and secondarily in Korea and China too, the latter in particular as natural forest in Chinese protected areas. In Japan there is a natural Quercus serrata forest region in inland Honshū, around Nagano and Ueda, as mentioned by Kira (1949) and described by Wada (1977, 1982a, b). We compared these drier, warmer deciduous Quercus forests with Quercus forests in cooler climatic zones, dominated mainly by Q. mongolica var. crispula, Q. mongolica, and Q. wutaishanica. As a result, it appears that Quercus forests can be classified into ten forest types (see main text), which can be grouped into three broader forest classes: (1) warm-temperate forests, with Q. serrata, Q. brevipetiolata Q. variabilis, Q. acutissima and Q. aliena; (2) temperate forests, with Q. mongolica var. crispula and Q. dentata in Japan, Q. mongolica in the Beijing area and southern Chinese Manchuria, and Q. wutaishanica in drier southern Inner Mongolia and the northern Qinling Mts.; and (3) cool-temperate forests, especially mixed forests of Q. mongolica and conifers (Pinus koraiensis, Abies holophyla and A. homolepis) on the Asian mainland (China, Korea and Russia), plus Q. mongolica var. crispula and Abies sachalinensis in Japan. Under human impact, species from the warm-temperate Quercus serrata and Q. variabilis forest invade both the cooler Quercus mongolica and Q. mongolica var. crispula forest in China, Korea and Japan and the warmer evergreen broad-leaved forests in Japan and Korea. Potential natural sites of Q. serrata and Q. variabilis forest in East Asia are subject to laurophyllization, i.e. invasion by planted evergreen species, but laurophyllization from Quercus serrata forests to Q. mongolica forests does not occur in China. Q. variabilis forests occur in areas much drier than those of Q. mongolica and evergreen broad-leaved forests. Conclusions: (1) Quercus serrata and Q. variabilis forests are the main warm-temperate forests in East Asia; and (2) these species also invade as secondary elements into both temperate (deciduous) forests and warm-temperate evergreen broad-leaved forests in East Asia. Similar laurophyllization also occurs in western Mediterranean areas with good soil, where evergreen broad-leaved species invade Quercus pubescens forests, especially in Insubria (southern low slopes of the European Alps) and near the glacial lakes. (3) These warm-temperate forests can be characterized by values of the Warmth and Coldness Indices and an annual moisture index (Box and Fujiwara 2013 and herein).