Natural disturbance and tree species coexistence in an old-growth beech - dwarf bamboo forest,southwestern Japan

Abstract. The structure and composition of a cool-temperate old-growth beech (Fagus crenata) - dwarf bamboo (Sasa spp.) forest, partially affected by landslide disturbance, in the Daisen Forest Reserve of southwestern Japan, were investigated in relation to forest floor and canopy conditions. All stems ≥ 4 cm DBH were mapped on a 4-ha plot and analyses were made of population structure, spatial distribution and spatial association of major tree species. The dominant species, F. crenata, which had the maximum DBH among the species present, had the highest stem density. However, for other species, larger-sized species had lower stem density with few smaller stems or saplings, while smaller-sized species had higher stem density with many smaller stems or saplings. Canopy trees of F. crenata were distributed randomly in the plot, while its stems in the other layers and all other species were distributed patchily. Small patches represent gap-phase regeneration. Larger patches correlate with landslide disturbance, difference in soil age, or the presence/absence of Sasa. Cluster analysis for spatial associations among species and stems in the different layers revealed that the forest community consists of several groups. One main group was formed on sites not covered with Sasa. This group contained a successional subgroup (from Betula grossa to Acer mono and/or F. crenata) initiated by landslide disturbance and a subgroup of tree species that avoid Sasa. Another group was formed on sites with mature soils covered largely with Sasa. This contained associations of canopy trees of F. crenata and smaller-sized tree species such as Acanthopanax sciadophylloides and Acer japonicum. It is found that the community of this old-growth beech forest is largely organized by natural disturbance and heterogeneous conditions of the forest floor (difference in soil age and presence/absence of Sasa). The existence of these different factors and the different responses of species to them largely contribute to the maintenance of tree species diversity in this forest.; Keywords: Cluster analysis; Fagus crenata; Forest dynamics; Gap; Landslide; Spatial pattern.     

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

Abstract. 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.     

Successional status of trees in gallery forest along the river Rhine

Abstract. 20 alluvial forest stands of different ages along the river Rhine in central Alsace, France, are described. A natural complex landscape occurs which is formed by erosion activity of the river. Recent human impact (canal construction, cutting) has affected river hydrology: flooding is eliminated over large areas and the underground water levels are stabilized. The forest vegetation varies in species diversity and structure, from young pioneer to older, mid-successional forests. The forests were classified into four associations: Salici-Populetum nigrae, Ligustro-Populetum nigrae, Fraxino-Populetum albae and Querco-Ulmetum minoris. The first three communities are ‘softwood’ because of the dominance of Salix and Populus, the fourth, dominated by Quercus robur, Fraxinus excelsior and Ulmus minor, is ‘hardwood’. Differences in structure, species composition and diversity in 10 widely varying stands in 30-yr and 150-yr old forests are quantified and interpreted in relation to the processes and gradients (moisture and texture) involved. A model of forest succession is developed as follows:

• 1 Whatever the topographic level, Salix and Populus species are the most competitive in colonizing bare sediments.
• 2 Under natural conditions, pioneer softwoods are generally replaced by hardwoods in less than 100 yr.
• 3 Old Querco-Ulmetum is basically the terminal stage of the alluvial succession.
• 4 Old softwood forests result from an interruption of the natural course of succession. Softwoods may be an intermediate or late-successional phase depending on the interruption.
• 5 Successional processes change according to hydrological and edaphic gradients.
• 6 Allogenic processes of flooding are fundamental in the space-time species pattern.
• 7 Allogenic processes are responsible for the high species and community diversity.

     

A cross-diffusion model of forest boundary dynamics

A simple mathematical model of mono-species forest with two age classes which takes into account seed production and dispersal is presented in the paper. This reaction — diffusion type model is then reduced by means of an asymptotic procedure to a lower dimensional reaction — cross-diffusion model. The existence of standing and travelling wave front solutions corresponding to the forest boundary is shown for the later model. On the basis of the analysis, possible changes in forest boundary dynamics caused by antropogenic impacts are discussed.     

Sackville Waterfowl Park,Sackville, New Brunswick,Canada. Baseline characterization,towards long-term monitoring

The Sackville Waterfowl Park, contains a 19 hectare shallow freshwater wetland created by reflooding a saltwater marsh that was drained three centuries ago. Its primary purpose is to provide wetland habitat and wildlife viewing opportunities to tourists and residents. This newly created, eutrophic wetland supports high densities of waterfowl, 2.1 and 3.3 brood ha^–1 in 1991 and 1992 respectively. It is hoped that long term monitoring of the Park's waterfowl population and wetland habitat will contribute to a better understanding of factors controlling breeding waterfowl populations.     

The biogeochemistry of a north-temperate grassland with native ungulates: Nitrogen dynamics in Yellowstone National Park

Nutrient dynamics of large grassland ecosystems possessing abundant migratory grazers are poorly understood. We examined N cycling on the northern winter range of Yellowstone National Park, home for large herds of free-roaming elk (Cervus elaphus) and bison (Bison bison). Plant and soil N, net N mineralization, and the deposition of ungulate fecal-N were measured at five sites, a ridgetop, mid-slope bench, steep slope, valley-bottom bench, and riparian area, within a watershed from May, 1991 to April, 1992.Results indicated similarities between biogeochemical properties of Yellowstone grassland and other grassland ecosystems: (1) landscape position and soil water affected nutrient dynamics, (2) annual mineralization was positively related to soil N content, and (3) the proportion of soil N mineralized during the year was negatively related to soil C/N.Grazers were a particularly important component of the N budget of this grassland. Estimated rates of N flow from ungulates to the soil ranged from 8.1 to 45.6 kg/ha/yr at the sites (average = 27.0 kg/ha/yr), approximately 4.5 times the amount of N in senescent plants. Rates of nitrogen mineralization for Yellowstone northern range grassland were higher than those measured in other temperate grassland ecosystems, possibly due to grazers promoting N cycling in Yellowstone.     

Changes in the content and constituents of the cuticular wax of Picea abies (L.) Karst. in relation to needle ageing and tree decline in five European forest areas

Cuticular wax composition of healthy and and declining mature Norway spruce trees [Picea abies (L.) Karst.] was investigated in five European forest areas. The amount of extracted wax and the content of alkanes and secondary alcohols were analysed as a function of the factors sample area (five areas, detailed below), needle age (current year to 2 years) and decline class (Class O to Class 2). Using a GC-MS, alkanes from C₂₀ to C₃₁ and the following alcohols were quantified: 10-nonacosanol, 5,10-nonacosandiol, 4,10-nonacosandiol and the triterpenol 24-methylenecycloartanol. According to our results, the total wax content as well as the alkane and alcohol content of waxes show a large variation corresponding to sample area and needle age. Ageing caused a highly significant increase in alkane content and a highly significant decrease in total wax and alcohol content. The decline class significantly influenced only the content of the long chain alkane C₃₁ (increase), the secondary alcohol 10-nonacosanol (decrease), and the triterpenic alcohol (decrease). Total wax weight was not influenced by tree damage. Thus, according to our results, needle ageing and progressive tree damage are correlated to different changes in the examined parameters.     

长白山站的研究数据库管理系统

长白山站的研究数据库管理系统翟永华,赵士洞（中国科学院沈阳应用生态研究所１１００１５）Ｄａｔｅ－ＢａｓｅＭａｎａｇｅｍｅｎｔＳｙｓｔｅｍｉｎＣｈａｎｇｂａｉｓｈａｎＦｏｒｅｓｔＥｃｏｓｙｓｔｅｍＲｅｓｅａｒｃｈＳｔａｔｉｏｎ．￥ＺｈａｉＹｏｎｇｈｕａ...     

Ammonia formation and soil pH increase caused by decomposing fruitbodies of macrofungi

The formation of gaseous compounds from decomposing fruibodies of three common macrofungi was qualitatively analysed. It was shown that significant production of ammonia took place. When the fruitbodies were decomposing on the surface of a podzolic forest floor more than 90% of the ammonia produced was absorbed by the soil, causing soil pH to increase.