Susumu Okitsu

Establishment processes and regeneration patterns of montane virgin coniferous forest in northeastern China

. The co-occurrence of Larix olgensis var. changpaiensis, Picea jezoensis and Abies nephrolepis in the coniferous forest of Mount Changbai, northeastern China, is discussed, and the regeneration pattern of these taxa compared on the basis of the analysis of the age structure and the age-height relationship of the three conifers. The presence of tall individuals (ca. 30 m in height) of Larix olgensis var. changpaiensis, which does not show any regeneration, was related to the large eruption of Mount Changbai up to ca. 400 yr ago. Picea jezoensis compensates its small recruitment by a large stem size and long life span together with a continuous height growth. Abies nephrolepis recruits well, but its small stem size and short life span do not result in its dominance in the forest.

Conditions for the development of the Pinus pumila zone of Hokkaido, northern Japan

The development of the Pinus pumila zone of Hokkaido, northern Japan is discussed on the basis of an examination of the Warmth Index (WI). The Pinus pumila zone is developed on deforested areas in the boreal subalpine belt, and is characterized by strong wind and heavy snow accumulation in winter, and by the presence of rocky fields. It is concluded that in Japan, including Hokkaido, this high mountain zone generally is intrazonal, belonging mainly to the subalpine belt, and that such zones are not common in Europe and North America. Its formation is due mainly to present-day wind, snow and substrate conditions and partly to conditions prevailing during the glacial period.

FACTORS CONTROLLING GEOGRAPHICAL DISTRIBUTION IN SAVANNA VEGETATION IN NAMIBIA

Here, I describe the geographical distribution of the savanna types in Namibia and identify the factors controlling the occurrence of each savanna type in relation to the amount of annual precipitation and the various physiographical regions, including the mopane ( Colophospermum mopane) area. The different types of savanna can be distinguished on the basis of the leaf habits of the dominant vegetation: deciduous, evergreen nanophyll, and evergreen notophyll. In general, vegetation performance (i.e., vegetation cover and maxi- mum height) was positively correlated with the amount of annual precipitation. However, the occurrence of a particular savanna type coincided well with physiographical region regard- less of the amount of annual precipitation received. Deciduous savanna occurred primarily in the Central Highland and had the smallest total vegetation cover among the three types. The dry soil of this region determined inevitably the deciduous leaf habit of the vegetation during the dry season and thus the smallest total vegetation cover. Evergreen nanophyll savanna was found mainly in the Mega Kalahari, where I observed a clear relationship between the amount of annual precipitation and total vegetation cover. The soil moisture in this region favored an evergreen leaf habit, even in the dry season, resulting in the effective use of soil water throughout the year. This probably accounted for the large increase in total vegetation cover with increasing annual precipitation. Evergreen notophyll savanna exclusively appeared in the mopane area, regardless of the physiographical region, and had the largest total vegeta- tion cover, apparently as a result of the ecological characteristics of mopane. Therefore, it appears that the geographical distribution of the various savanna types in Namibia is princi- pally controlled by two different factors that are independent of the amount of annual precipi- tation: the water-holding capacity of the soil and the ecological characteristics of mopane.

The subalpine vegetation of Mt. Vysokaya, central Sikhote-Alin

The subalpine vegetation structure of Mt. Vysokaya, the Central Sikhote-Alin, is described. This vegetation consists mainly of subalpine spruce-fir forest, a complex of subalpine meadows, shrubs, groves of Betula lanata (B. ermanii s.l.), krummholz of Pinus pumila and alpine tundras. Significant disturbances in the vegetation structure were noted, especially in the forest-tundra ecotone accompanying a sharp reduction of the belts of Betula lanata and Pinus pumila. The altitudinal level of the upper timberline reaches 1600 m a.s.l. which is 250 m less than the expected altitude calculated by Kiras warmth index. An undergrowth of scattered trees of Picea and Betula are growing up to the mountain top. Based on these data and a review of the literature, we concluded that a catastrophic lowering of the timberline and devastation of the subalpine vegetation belt occurred several centuries ago, probably as result of fires.

The effects of bryophyte communities on the establishment and survival of an epiphytic fern

Ferns typically grow in soil that has sufficient moisture to enable the germination, fertilization and growth of gametophytes. However, the epiphytic fern, Lepisorus thunbergianus grows on tree trunks often in urban areas, where its gametophytes are susceptible to desiccation and its spores are easily washed off by rainwater. To understand how these ferns become established and survive in such challenging conditions, we conducted a quadrat survey on trunks of Prunus mume (which has cracked bark) and Ilex integra (which has smooth bark), focusing on the presence of bryophyte communities, which are known to facilitate seed establishment. Regardless of bark roughness, fern gametophytes occurred more frequently in the communities of small-leaved and short-bodied liverworts, and young fern sporophytes occurred more frequently in the communities of tall-bodied mosses. As the gametophytes of L. thunbergianus are taller than the liverworts, they are able to grow in the presence of liverworts without experiencing shading effects. However, sites with liverworts were unsuitable for fertilization of fern gametophytes because they were more desiccative environments than the sites where tall mosses grew. In habitats where tall mosses grow, fern gametophytes tended to be affected by competition from the bryophytes, whereas once fern gametophytes had established and matured, it was easy for them to generate young sporophytes because tall mosses retain sufficient moisture for the ferns’ fertilization. In summary, the presence of a moss community is an important factor aiding the establishment of this epiphytic fern in desiccated urban areas.

Carbon and nitrogen contents and greenhouse gas fluxes of the Eurasian steppe soils with different land-use histories located in the Arkaim museum reserve of South Ural, Russia

The effects of different land-use histories on contents of soil carbon (C) and nitrogen (N) and fluxes of greenhouse gases [carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)] measured using the closed chamber method were investigated in the Arkaim museum reserve located in the South Ural of Russia. A natural forest site (NF) and two grassland sites that had different land-use histories (CL: cropland until 1991; PST: pasture until 1991; both sites have been fallow for 18 years) were selected for soil sampling and gas flux measurements. The vegetation in NF was mainly Betula pendula Roth. with steppe cherry and grassy cover. Perennial grasses (Stipa spp., Festuca spp. and others) have been planted in CL and PST since 1991 to establish reserve mode, and the projective cover of these plants were > 90% in both sites in 2009. Soil samples were taken from the A horizon in the three sites, and additionally samples of the O horizon were taken from NF. The contents of soil C and N [total C, total N, soluble organic C, soluble N and microbial biomass C (MBC)] in the O horizon of NF were the largest among all investigated soils (p < 0.05). Additionally, the total C, total N and MBC in PST were significantly larger than in CL (p < 0.05). Positive CO2 fluxes (i.e., CO2 efflux) in all three investigated sites were observed. The CO2 efflux in NF was significantly larger than in CL and PST (129, 30 and 25 mg C m−2 hour−1, respectively, p < 0.05), although there was no significant difference in values of CO2 efflux between CL and PST. There were no significant differences in the fluxes of CH4 and N2O among NF, CL and PST (p > 0.05). Our current research indicated that, in soils of the Eurasian steppe zone of Russia, total C, total N and MBC were affected not only by current land-use (i.e., fallow grassland vs. natural forest) but also by past (until 18 years ago) land-use.

Forest Vegetation of Northern Japan and the Southern Kurils

The composition and geographical distribution of major forest types of northern Japan, including the southem Kuril Islands, are summarized, along with phytogeographical relationships of the major forest types to the forests of the adjacent Korean Peninsula, northeastern China and the Russian Far East. Two major forest zones appear, a cool-temperate forest zone and a boreal forest zone, as well as a subalpine forest belt in mountains of northern Japan. The cool-temperate forest zone includes five major climax forest types: Fagus japonica forest, Quercus serrata forest, Fagus crenata forest, Quercus mongolica forest and Abies sachalinensis-Quercus mongolica forest. This zone covers almost all of lowland northern Japan. The boreal forest zone includes three major climax forest types: Picea jezoensis-Abies sachalinensis forest, Picea glehnii forest and Larix gmelinii forest. This zone occurs in central Hokkaido and on the southern Kuril Islands. The subalpine forest belt includes three major forest types: Abies mariesii forest, Betula ermanii forest and Pinus punrila thicket. Phytogeographically, the Quercus serrata forest and Quercus mongolica forest are the principal forest types of cool-temperate deciduous broad-leaved forest in northeastern Asia. The Fagus crenata forest is a snow-induced, non-zonal climax. The Abies sachalinensis-Quercus mongolica forest is the most essential forest type of the Pan-Mixed Forest Zone (sensu Tatewaki), together with the Quercus mongolica forest. The Picea jezoensis-Abies sachalinensis forest composes the eastern and southernmost extension of the boreal evergreen forest zone in northeastern Asia. The subalpine Abies mariesii forest is endemic to northern Japan, while the Betula ermanii forest occupies the area of highly oceanic climate in northeastern Asia. Finns punula thicket is a homologue of the Larix gmelinii-Pinus pumila forest in continental northeastern Asia. The south to north zonation of forest types in lowland northern Japan corresponds to the following sequence: Quercus serrata forest, Quercus mongolica forest, Abies sachalinensis-Quercus mongolica forest, and Picea jezoensis-,Abies sachalinensis forest.

Spore-holding Capacity of Bryophyte Colonies Influences Pteridophyte Establishment in a Vertical Environment

Abstract Gametophytes of epiphytic and epipetric pteridophytes occur frequently in bryophyte colonies; however, little is known about the influence of bryophytes on pteridophyte establishment. In the present study, we describe how the spore-holding capacity of bryophyte colonies contributes to the retention of pteridophyte spores in a vertical environment. Lycophytes did not grow at the sampling site; hence, we used Lycopodium spores to distinguish from any other pteridophyte spores that might have already been present in the wild. We dispersed aliquots of approximately 500,000 spores on vertically suspended bryophyte (both mosses and liverworts) colonies (5 cm × 5 cm) attached to ceramic plates. The bryophyte colonies included ten species (seven mosses and three liverworts), which have different characteristics in colony height, leaf length, and dry weight. Mudstone blocks and ceramic plates were used as control surfaces (5 cm × 5 cm). After simulated rainfall, we counted the number of spores retained in the colonies and controls. We found that the bryophyte colonies retained a significantly higher percentage of Lycopodium spores (90.7±7.4%) than the controls (ceramic plate: 7.5±20.9%; mudstone: 39.7±20.6%). The average values of retained spores within the bryophyte colonies correlated with their logarithmic values of dry weight per square centimeter (R2 = 0.62, P < 0.05). Leaf thickness and stem diameter were slightly different across species. Thus, dry weight value of bryophyte colony per unit area is very likely a simple function of number of stem-and-leaf units, which correlate closely with the surface area. Bryophyte colonies that have high surface area on which pteridophyte spores might be retained within a colony might provide a suitable environment for spore adherence in epiphytic and epipetric habitats.

Basic Geomorphological and Geological Characteristics of Northeast Asia

The geology and geomorphology of Northeast Asia are briefly described, including the most important relief and hydrologic components. The basic geological setting, structural foundation, stratigraphy, tectonics, sedimentary and volcanic development, and present geological processes are briefly introduced.