Tatsuaki Kobayashi

Ecophysiological behavior ofArtemisia ordosica on the process of sand dune fixation

The population structure and water relations ofArtemisia ordosica were studied at different stages of the sand dune fixation process. Vegetation coverage and biomass increased as the sand dune fixation process progressed. In contrast, individual growth rate decreased in the late fixation stage. On fixed sand dunes the modal age ofA. ordosica plants was higher and seedlings or saplings were rearely observed. On active sand dunes, settlement of seedlings was regulated by sand mobility; that is, seedlings were observed only when sand mobility was below 10 cm per year. Leaf transpiration was highest in active sand dunes. Stand transpiration in fixed sand dunes was lower than in semi-fixed sand dunes. These differences in transpiration were related to a decrease in soil water availability, which was affected by the increase in the aeolian fine soil component during the course of sand dune fixation. The reduction in soil water status and the cessation of sand movement were considered to be important factors in the decline of theArtemisia ordosica community.

Carbon content of soil in urban parks in Tokyo, Japan

Because of difficulties in estimating the carbon fixation rate, we alternatively investigated the C content of the soil in 19 urban parks in the Tokyo metropolitan area. The C content of the soil under three vegetation types was measured: grassland/turf (“turf”); tree-planting area with plant management (with weeding and removal of fallen leaves) (“tree-planting area”); coppice or tree-planting area without plant management (“coppice”); bare land was used as control. Average C contents of turf, tree-planting area and coppice were about 82, 79 and 120 Mg–C ha−1, respectively, and were larger than the C content of trees in an urban park, as estimated in previous studies. The results indicate that the soils of urban parks function as a C sink.

A coupled model of photosynthesis-transpiration based on the stomatal behavior for maize (Zea mays L.) grown in the field

The study presents a theoretical basis of a stomatal behavior-based coupled model for estimating photosynthesis, A, and transpiration, E. Outputs of the model were tested against data observed in a maize (Zea mays L.) field. The model was developed by introducing the internal conductance, gic, to CO2 assimilation, and the general equation of stomatal conductance, gsw, to H2O diffusion, into models of CO2 and H2O diffusion through the stomata of plant leaves. The coupled model is easier for practical use since the model only includes environmental variables, such as ambient CO2 concentration, leaf temperature, humidity and photosynthetic photon flux received at the leaves within the canopy. Moreover, concept of gic, and factors controlling A and E were discussed, and applicability of the model was examined with the data collected in the maize field.

The Land-use Changes of "yatsuda″and the Peculiarity of the Paddy Field Vegetation(PAPERS OF THE 18th SCIENTIFIC RESEARCH MEETING)

近年変化が著しい里山「谷津田」の保全に関する基礎的研究として, 千葉市内の谷津の伝統的水田, 谷津の整備水田, および平野部の整備水田で土地利用図の作成, 水田, 畦と水路際の植生調査水田と畦の土壌水分測定を行った。谷津の伝統的水田の多くは耕作放棄され, 草地となっていた。土壌水分, 単位面積当たりの種数や多年草と水湿植物の種数は谷津, 特に伝統的水田で多かった。希少種は谷津で多く確認された。水路際の種数は整備水田におけるコンクリート水路より伝統的水田における土水路で著しく多かった。谷津田は平野の水田に比べ種多様性が高いことがわかり, その特異的環境を保っている斜面林との一体的な景観保全の必要性が指摘された。

Socio-ecological analysis of desertification in the Mu-Us Sandy Land with satellite remote sensing

To understand the contemporary process of desertification in the Mu-Us Sandy Land, China, we assessed the current status of desertification from satellite images. We analyzed the effect of land use by comparing desertification images and GIS-based thematic data. Socioeconomic factors were studied through interviews with local people. The desertified area ratio in each village was related to the sand dune ratio. Desertification in this region was affected by the activity of sand dunes. The revegetated area ratio had a close relationship with the cropland ratio. The development of cropland and surrounding woods contributed to revegetation of desertified land. Desertified areas were distributed mainly in pastoral regions. Critical carrying capacity of grassland for sheep and goats was approximately 2 head/ha. High population density of goats was evident in the severely desertified ranges. Goats were increasingly introduced to earn money through modernization, but they overgrazed fenced pastures. Further environmental education is needed to promote sustainable land use.

Natural hybridization of Japanese Rhododendron section Brachycaryx in Mount Kintoki in eastern Japan and concerns for genetic diversity in restoring their habitat

Native Rhododendrons section Brachycaryx in eastern Japan are decreasing in their natural habitats and the need to restore these habitats is increasing. Conservation of genetic diversity in restoring habitat requires clarification of the balance of interspecies genetic exchange which occurs in their natural habitats. In well-preserved natural habitats of Rhododendron dilatatum, R. kiyosumense, and R. wadanum and their natural hybrids R.×kuratanum and R.×hasegawai we investigated their geographical distribution, frequency, and flowering period. DNA analysis of the internal transcribed spacer (ITS) region was also conducted to confirm the species related to hybridization. Our findings in the field survey were: (1) Hybridizations occur in the overlap zones of related species. (2) R.×hasegawai occurs more frequently than R.×kuratanum, probably because the flowering seasons of R. kiyosumense and R. wadanum overlap longer than those of R. dilatatum and R. kiyosumense. (3) Natural hybrid occurrence is, nevertheless, under 9% of all related Rhododendrons section Brachycalyx. Analysis of the ITS region suggested that the two hybrids are generated from interspecific gene exchange, i.e., (4) R. dilatatum and R. kiyosumense relate to the formation of R.×kuratanum. (5) R.×hasegawai is a hybrid of R. wadanum and some species other than R. wadanum. On the basis of these findings we delineated several guidelines for restoring habitats of Rhododendrons of Section Brachycaryx with concerns for genetic diversity: (1) Before use, identify plant materials by morphological traits to determine whether they are original species or hybrids. (2) Investigate the distribution of remnant Rhododendrons section Brachycaryx before restoration. (3) Combine plant materials of original species in the natural distribution.

Comparison of organic matter dynamics in soil between Japanese cedar (Cryptomeria japonica) forest and adjacent Japanese red pine (Pinus densiflora) forest established on flatland

In order to clarify the effects of tree species on organic matter dynamics in soil, we investigated the amount of forest floor material, leaf litter decomposition rate, soil chemical characteristics, soil respiration rate and cellulose decomposition rate in a Japanese cedar forest (cedar plot) and an adjacent Japanese red pine forest (pine plot) established on a flatland. The amount of forest floor material in the cedar plot was 34.5 Mg ha−1 which was greater than that in the pine plot. Because the leaf litter decomposition rate was higher in the pine plot than in the cedar plot, it is likely that the difference in the amount of forest floor material between the plots is caused by the difference in the leaf litter decomposition rate. The C concentrations of soil in the cedar plot were 1.2–2.1 times higher than those in the pine plot. Soil pH(H2O)s in the cedar plot were significantly higher than those in the pine plot. The soil respiration rates and the rates of mineralized C in the cedar plot byin vitro incubation were higher than those in the pine plot. From this result, it is assumed that soil organic matter in the cedar plot was decomposed relatively faster compared with the pine plot. Furthermore, microbial activities, which were reflected as cellulose decomposition rates in the cedar plot, were higher than those in the pine plot.

The effects of urbanization on chemical characteristics of forest soil in Tamagawa basin, Japan

In order to clarify the effects of urbanization on the chemical characteristics of forest soils, we investigated several surface soil chemical characteristics, including (1) carbon (C) concentration, (2) concentrations of exchangeable bases, (3) cation exchangeable capacity (CEC), and (4) soil pH of forests in the Tamagawa basin, Japan. We defined the road ratio as level of urbanization. Study sites were located in areas with varying levels of surrounding urbanization. Surface soil concentration of exchangeable bases (especially calcium and magnesium), percent base saturation, and pH (H2O) increased with an increasing road ratio; in other words, with increased urbanization, C and CEC were unrelated to road ratio. One reason for the observation of increasing exchangeable bases with increasing urbanization appears to be the deposition of dust. The increase in exchangeable bases concentration (and % base saturation) corresponds to increases in soil pH.

Allelopathic Activities of Tree Species

木本植物種の他感作用物質の有無や他感作用の程度・様式を把握する目的で, 関東地方に見られる木本種30種類について, 葉からの水抽出液と工タノール抽出液を用いた, レタスを検定植物とする発芽・生育試験を行った。発芽開始時間, 発芽速度, 最終発芽率, 幼根・胚軸の伸長量を求め, 種間比較を行った。いずれの樹種でも発芽速度の低下と幼根の伸長阻害が見られた。陽樹であるアカマツ・クロマツ・イイギリ・エゴノキは水抽出液, エタノール抽出液のいずれについても顕著な他感作用を示すことから, 他感作用物質を持つと考えられる。このような他感作用物質を持つ樹種を緑地へ植栽することによる, 雑草の発生や生育の抑制が期待される。

Efficient field data collection of tropical forest using terrestrial laser scanner

Various remote sensing technologies are utilized to monitor tropical forest for REDD project. In developing countries, the accuracy of field measurement does not satisfy the quality required for the validation of satellite remotely sensed data. Therefore, we introduce the most portable laser sensor, SICK LMS511, to measure trees in the field of tropical forest and the semi-automatic process to derive tree parameters from the 3D point cloud is established to provide accurate forest inventory data. From the accuracy assessment of the portable laser system provided 3.61 cm of root mean square error (RMSE) of stem diameter and 0.50 m of RMSE of tree height measurement. The portable terrestrial laser sensor can be the standard technique to create forest inventory data for the field validation of satellite remote sensing.