Akihiro Nakamura

Impact of leaf physiological characteristics on seasonal variation in CO2, latent and sensible heat exchanges over a tree plantation

This study investigated the impact of leaf physiological characteristics on CO 2, sensible heat, and latent heat exchanges over a plant community. Measurements were carried out over plantation trees using an eddy correlation system, under well-watered soil conditions for several days spanning the year, and under soil drought conditions during autumn only. The following leaf physiological characteristics were investigated: the maximum rate of carboxylation (VcMAX25: [Planta 149 (1980) 78–90]), the relationship between stomatal conductance (gs) and net assimilation rate (An) adjusted by relative humidity (hs), and CO2 concentration at the leaf surface (cs) [An analysis of stomatal conductance. Ph.D. Thesis. Stanford University, CA, 89 pp.]. As the leaf physiological parameters, VcMAX and the relationship between stomatal conductance (gs) and Anhs/cs of four evergreen trees were estimated from gas exchange measurements at the single leaf scale. Numerical simulations were carried out using a multi-layer model consisting of a second-order closure model for atmospheric diffusion coupled with a radiation transfer model, a Farquhar type photosynthesis model, and Ball’s stomatal conductance model. The results suggest that the value of VcMAX25 changes every day, and that appropriate values should be used in simulations. The relationship between stomatal conductance (gs) and Ahs/cs changed under soil drought conditions, and this change should also be allowed for in simulations. These results show that changes in leaf physiological characteristics contribute considerably to seasonal variation in CO 2, latent heat, and sensible heat exchanges over plantation trees.

Role of the EXPO ’70 forest project in forest restoration in urban areas

The forest-restoration project of EXPO ’70 Commemorative Park, Japan, is an epoch-making attempt to restore a nature-oriented forest park in an urban area in which large-scale land reclamation had occurred. The objective of this paper is to review the concept, planning, and design, and the outcome so far, and discuss current aspects of creating a core natural habitat in the city of Osaka. Innovative planning policy and design methods have been used for construction of the forest-restoration project of EXPO Park. Unexpected troubles have occurred, however. After approximately 10xa0years severe effects of poor drainage and soil compaction on the establishment of the forest have been revealed by intensive monitoring. Partial redevelopment and soil-amendment work has therefore been conducted. These improvements seemed to have resulted in “a self-sustaining forest”, the original objective of the planning policy. After approximately 25xa0years, however, a second intensive monitoring program has revealed that the status of nature restoration is generally favorable in quantity but not in structure of forest communities or biodiversity. The major issues identified are excessive tree density with a single foliage layer caused by the single generation of immature forest stand, and ecological isolation from the source of nature. The EXPO forest is currently in the “Second Generation” stage; this involves management, including artificial gap regeneration, and soil seed bank introduction, with careful monitoring. The project is expected to be an ideal example of a core habitat of nature-oriented forest in urban areas achieved by adaptive management.

Evaluation of revegetation using forest top soil by seed density, species and divesity-area curves.

関西地方の18箇所の森林から表土を採取し, 撒き出し施工および実験を行った。多くの森林に生育していたコナラ, アベマキの実生出現頻度は小さかったが, ヒサカキの群落および実生出現頻度はともに大きかった。群落での出現頻度の小さかったアカメガシワ, ヌルデなどの実生出現頻度は大きく, 平均埋土種子密度も7個/m2以上と大きく, 表土撒き出し緑化によって, これらの先駆種からなる群落形成の可能性が示された。複数のサブプロットの組み合わせで算出した種数, 多様度指数—面積曲線によって, 異なる面積のプロット間での多様性の比較が可能となった。低密度出現種の多いプロットでは, 出現種数は面積の影響を大きく受けるため, 種多様性評価を行う場合には大面積の調査が必要であることが明らかとなった。

Surface Temperature Estimation from Airborne Imagery Using Neural Network Model

Abstract Comparisons for surface temperature estimation from radiance received by airborne multispectral sensor (MSS) were made between linear regression, multiple regression and back propagation neural network model. Data of upwelling radiance recorded at morning (AM) and afternoon (PM) were applied for analysis. Based on ± 10% residual error interval, a neural network trained with separate AM and PM data sets attained 87.5% prediction of surface temperature compared with 50% by conventional models but attained only 62.5% prediction for AM data when trained with combined data sets. Training with separate data gave more uniform prediction of surface temperature, out-performing conventional models.

Assesment for Earthquake Disaster on Growth of Trees by Dendrochronological Method

阪神・淡路大震災の液状化, 火災の影響が樹木の成長に与える影響を, 年輪解析から明らかにした。成長錐で被災した神戸市内に生育する樹木の, また震災の影響のなかった大阪府堺市に生育する同一樹種のコアサンプルを採取し, 年輪幅の比較を行った。その結果, 液状化の生じた場所に生育するクスノキ, クロマツ, アキニレには, 液状化による長期的な成長量低下の影響はなかった。また火災によって被災したクスノキには肥大成長量低下がみられたが, ケヤキにはみられなかった。しかし被災の翌年に成長量の低下した樹木も, 2年後から成長量の増加がみられ, 震災の影響は短期的であったと考えられた。

Photosynthetic Characteristics of Interior Trees under Different Light Environment

異なる光環境 (全天光下, 遮光下, 室内) に生育するモッコク, クロガネモチ, モチノキ, カラタネオガタマの常緑広葉樹4種の光合成特性を, 切り枝を用いてアトリウム空間で測定した。これら4種の樹木は, 暗呼吸速度, 光補償点が, 同時に測定を行った陽樹のアカメガシワに比べて小さく, 異なる光合成特性を示した。およそ70%の遮光条件下では, 野外の全天条件下に比べ多少耐陰性が増加し, 室内条件下ではさらに耐陰性が増加した。屋外または遮光条件下のモチノキ, クロガネモチは, 高光量域でアカメガシワと同程度の大きな光合成速度を示すが, 室内条件下では, 熱帯林林床の樹木に近い小さな暗呼吸速度, 光補償点を示し, 光合成の可塑性が大きな樹種と考えられた。

A Method for Growth Monitoring of Planted Quercus Forests by Photometry inside the Community

植物群落をモニタリングする手法の1つとして, 群落内の光環境に注目し, 群落内に入射する光の量を照度ではなく波長特性に応じて測定することによって, 群落の生育状況が把握できる可能性について考察を加えた. 葉の分光反射・分光透過率を分光放射計にて測定し, 樹葉の重なり合った時の光学モデルを作成したところLAの変化に対する感度は, 反射光よりも透過光が, 赤色光よりも近赤外光が高いということがわかった. 反射光の植生指数と同様に, 群落内透過植生指数 (R/IRとNDVI) の使用により群落の生育診断が可能である見通しを得た.