We investigated distribution characteristics of Abies homolepis forests with aerial photograph analysis and field exploration in the mountainous areas of Oku-Nikko, in central Japan. Abies homolepis was distributed widely in pure stands with high population density, in patch stands and/or mixed stands with low density in the investigated area. They were widely distributed on the southern slope of Mt. Nantai with high density. Its density gradually rose with increasing gradient of the slope. Patch stands of A. homolepis occurred noticeably in the sites of the natural levee and of the flood plain. We analyzed the annual rings to locate the regenerated years of A. homolepis forests and to explain the growth progress made after the regeneration. The analysis presented three types of the annual rings as being normal, with suppressed growth and gaps waiting for growth. All the types showed strong dependency on the light factor of the forest floor. Established ages of seedlings and diameter growth ascertained corresponded with the occurrences of the heavy typhoon attacks in each stand. This phenomenon was remarkable in the event of the typhoons occurred in the middle of 1800's, and in the early and the middle of the 1900's. A. homolepis which might have appeared before the 1800's did not show at investigated years. The age of old-growth forests of A. homolepis in the mountainous areas of Oku-Nikko was estimated as being in the range of 130-160 years old. It might be needed to regenerate for their species existence because of their relatively short life span. The forest decline and canopy release evidenced to have occurred in 1959 caused by Isewan-typhoon was followed by marked acceleration in its regeneration after the typhoon. The general patterns of regeneration in Oku-Nikko area were, therefore, explained from the perspective of canopy release that occurred due to the natural death of A. homolepis and the large-scale collapse of canopy with the events of typhoon, and by their seedling bank on the forest floor. Another and yet critical problem, discovered during the investigation, threatening the survival of the forests, was of the bark tripping done by Sika deer living in Oku-Nikko area We came to be convinced of the need of investigation on the influence of Sika deer exerted on the life of A. homolepis.

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Mangrove is a vegetation distributed in seashore lines and estuaries in tropical and sub-tropical zones. The distribution patterns of mangrove species are influenced by some environmental factors, such as submergence time, salinity, character of soil substructure, etc. Especially, salinity is one of the main factors to determine the mangrove distribution and a change of mangrove species caused by salinity can be observed along tidal river. This study was conducted to understand relationships between distribution of mangrove species and salinity level along the tidal river. Three tidal rivers shorter than 50km were selected for the survey, which are the Linao and the Cabuyo Rivers in Cagayan Province, and the Kabibihan River in Quezon Province in the Philippines. As salinity of river water diminishes, composition of mangrove species is also changed. Only Nypa fruticans revealed wide suitability for salinity (0-29mgL^<-1>) among 28 species, while almost other mangrove species indicated partially high or low salinity. Tolerance of or adaptation to salinity appeared to lie in a series as Major components>Minor components>Associates. However, most mangrove species has wider adaptation to salinity and no apparent relationship is observed between dominance and salinity. Therefore, it is difficult to explain mangrove distribution pattern such as mangrove zonation only salinity factor.

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In tree planting constructions and tree management works, we have used the rank appraisal method by the Resources Council in the Science and Technology Agency to evaluate tree vigor. However, this evaluation method has a weak point about the change of results due to personal factors. Consequently, an objective method has been needed. The new evaluation method for tree vigor, the relative change of sap temperature, was proposed using the degrees of changes that sap temperature was fluctuated by heat exchanges between the tree and its external environments. In this study, we investigated the net radiation on the surface of stems and the vertical changes of temperature in the stems for the vital and weak trees. When the transpiration is active in the almost same thermal environment such as air temperature, the degree of tree vigor related to the transpiration can be almost judged by the relative change of sap temperature calculated from some tree stem temperatures and etc.. And it is obvious that the relative change of sap temperature has some physiological meanings.

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The purpose of this study is to clarify the reason for changes in the soil carbon contents depending on the conversion of the forest management type from natural deciduous broad-leaved forests (broad-leaved forests) to artificial Japanese cypress and Japanese cedar forests (coniferous forests). In the coniferous forests, Japanese cypress (Chamaecyparis obtusa) was planted on the upper slop and Japanese cedar (Cryptomeria japonica) was planted on the lower slope. In this study, comparisons of the results were made between the broad-leaved forest and coniferous forest in each slope position. The soil carbon content in the cypress forest was about 0.6 times lower than that of the broad-leaved forest on the upper slope. On the other hand, the soil carbon content in the cedar forest was almost the same to that of the broad-leaved forest on the lower slope. The amounts of soil microbial biomass C and soil respiration rates, metabolic activity of the soil microorganisms, cellulose decomposition rates and the amounts of nitrogen mineralization of the cypress forest was 0.3-0.5 times lower than that of the broad-leaved forest. The amounts of soil microbial biomass C and soil respiration rates, metabolic activity of the soil microorganisms, cellulose decomposition rates and the amounts of nitrogen mineralization of the cedar forest was 0.6-1.3 times than that of broad-leaved forest. These tendencies reflected the soil carbon contents. The carbon mineralization rate of the cypress litter was 1.2 times higher than that of the broad-leaved litter on the upper slope. The carbon mineralization rate of cedar litter was 0.8 times lower than that of the broad-leaved litter on the lower slope. This suggested that the cypress litter had been easily mineralized and had been difficult to accumulate relative to the litter in the broad-leaved forest on the upper slope, while the cedar litter had been mineralized with difficulty which provided a rapid accumulation relative to the litter in the broad-leaved forest on the lower slope.

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To determine the accumulation rates of soil carbon and nitrogen after afforestation practice, we investigated surface soil and organic layer in different aged four nurseries, from a two years-old stand to a 33 years-old stand. The accumulation rate of carbon and nitrogen in the soil of 0-5cm depth were 60.3gCm^<-2>yr^<-1>, 4.66gNm^<-2>yr^<-1> in 2 years-old stand (Cryptomeria japonica), 47.3gCm^<-2>yr^<-1>, 2.57gNm^<-2>yr^<-1> in 6 years-old stand (deciduous tree), 14.0gCm^<-2>yr^<-1>, 0.70gNm^<-2>yr^<-1>, in 18 years-old stand (Pinus parviflora), 19.0gCm^<-2>yr^<-1>, 1.01gNm^<-2>yr^<-1> in 33 years-old stand (Crytomeria japonica). The accumulation rate of carbon and nitrogen in soil tended to be faster in younger stand. Althrough the accumulations of carbon and nitrogen in the organic layer were not correlated with stand ages, the accumulations of carbon and nitrogen in the soil of 0-5cm depth were linearly correlated with stand ages. The mean accumulation rate of carbon and nitrogen in soil was estimated at 18.7gCm^<-2>yr^<-1> and 0.99gNm^<-2>yr^<-1>, respectively. Since the reference layer (5-10cm depth) was used in order to estimate the accumulation rates of soil carbon and nitrogen, the accumulation rates may have been estimated to be low. But, carbon and nitrogen in the soil of 0-5cm depth were clearly increased after afforestation.

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The temporal variation in leaf nitrogen content was investigated in an 8m tall Cryptomeria japonica canopy. Leaf nitrogen content (expressed on area basis) decreased with increasing leaf age. The nitrogen content of current leaves increased from June to October and then decreased thereafter. Nitrogen content of one-year-old leaves decreased gradually as the season progressed. There was no clear variation in leaf nitrogen content in two- and three-year-old leaves. The oldest leaf was three-year-old, and about half amount of the nitrogen was resorbed prior to leaf abscission. Nitrogen use efficiency was calculated from leaf life-span, resorption efficiency, and photosynthetic capacity. Photosynthetic capacity was estimated from leaf nitrogen content. Nitrogen use efficiency of Cryptomeria japonica was intermediate to that of other conifer species previously described. We concluded that Cryptomeria japonica, which has short-life leaves and moderate resorption efficiency, increases nitrogen use efficiency with increasing photosynthetic capacity per unit leaf nitrogen.

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