Hisayuki Maenaka

Dynamics of species diversity in a Japanese warm-temperate secondary forest

To examine the dynamics of species diversity during secondary succession, growth, death and recruitment of trees were monitored for 39 years (1966 to 2005) in two plots (P-1 and P-3, 40 m × 40 m each) in a Japanese warm-temperate secondary forest recovering from clearcutting that occurred in the 1910s. Typhoons in the early 1990s seriously damaged P-1 and moderately damaged P-3. We examined how species diversity of trees changed through succession for three size classes: large (diameter at breast height, dbh ≥ 4.5 cm), medium (4.5 cm > dbh ≥ 1.0 cm), and small (dbh < 1.0 cm). Before the typhoons occurred, species diversity and evenness generally increased over time in all size classes in both plots, except for medium trees in P-1. After the typhoons, species diversity increased over time without exception, and this usually involved increases in both species evenness and number. We found that recruitment always contributed to increases in species diversity but mortality did not. Recruitment increased speci...

Dead forms of canopy trees and regeneration process in Tadasu-No-Mori Forest

ギャップ更新の視点から，下鴨神社糺の森において林冠木の枯死形態と跡地への木本実生の侵入と定着の状態について調査を行い，各樹種の更新状況を検討した。その結果，林冠木の枯死形態はその後の実生の定着に影響をおよぼしてはいなかった。林床で見られた実生のうち，シュロの個体数が最も多く，また高木性樹種ではアラカシの実生が多数みられた。このことから今後アラカシが高木層の優占種となる可能性が高いと考えられた。林冠層での優占種ニレ科樹木では，ムクノキ，ケヤキで実生個体数が少なく，最優占種であるクスノキの実生密度も低い値であった。これは林冠木の枯死跡地であっても，その天空率の平均値が非常に低いことが理由として考えられた。

Pteridophyte Species Richness in Japanese Gardens in the City Matrix

The present study was performed to examine the pteridophyte species richness of Japanese gardens in the city matrix as urban wildlife habitats. We investigated the relationships between the number of species in 24 Japanese gardens with ponds or streams and various landscape factors in the Kyoto city area. Our results demonstrated a significant positive correlation between species richness and garden size. Comparison of the pteridophyte species-area curve of Japanese gardens with that of fragmented forest patches indicated greater species richness in the former as compared with the latter. This was considered to be because the fragmented forest floor undergoes drying with increases in edge effect with reduction of patch size or increases in the isolation distance, while the ponds and streams in Japanese gardens mitigate the dehydration of forest floor plants by providing a moist environment.

Simulation Model of Size Frequencies of Saplings in Restored Natural Habitat in Urban Area by Using Exponential Distribution

The population dynamics of saplings taller than 50cm were investigated from 1998 to 2003 in every year in the whole 6048m² area of the restored natural habitat Inochi-No-Mori in Kyoto city. There were 1249 saplings in the area in 2003. Population density was 32.2 individuals / 100m². Celtis sinensis formed 32.3% of the total number of individuals and was dominant species of Inochi-No-Mori. Only 126 saplings had been dead from 1998 to 2003 , so mortality rate was very low. We examined the height growth characteristic of saplings. As a result, there were size dependencies on the height growth of saplings. So we approximated the height distributions of saplings by exponential functions. By using this model, simulation about the height growth of each sapling was conducted in assuming that mortality rate and number of recruitment individuals was constant. We got the calculated size distributions from 1999 to 2003 and compared the calculated size distributions with the observed ones. As a result, differences between the observed size distributions and the calculated ones were very slight. This model predicted that the frequency of saplings taller than 500cm would be highest in 2015. The simulation was very valid for predication dynamics of saplings.

Evaluation of a basin ecosystem in arid region using satellite remote sensing

In Central Asia, large-scale expansion of agriculture in Aral Sea basin caused by heavy exploitation of irrigation water from international rivers in the early 1960s. This resulted in the rapid shrinking of the natural wetlands and significant change in the ecosystems. The decrease in river water and the resultant shrinking of the water area have led to destruction of the natural environment. To evaluate such landscape changes satellite remote sensing is most useful. Thus, we started monitoring the ecosystem through investigation and using satellite remote sensing. The study site is the lower Syr-Darya region where is considered as the most unstable in the catchment environment. Ground-truth data of land surface was collected through expeditions from 1999 to 2003. Based on floristic composition and soil investigation, vegetation was classified by using multivariate and cluster analyses. Based on the classification, spectral reflectance, biomass, LAI and plant coverage were measured on each type of vegetation in summer, 2002 and 2003. We found that LAI is a good estimate of biomass, and LAI can be estimated from either NDVI or TSAVI depending on vegetation type in this region. Using these data and methods, we analyzed succession of vegetation on the dried bottom of Aral Sea and relationship between wetland and river flow changes, relationships between the occurrence of Pelicans colony and environmental factors of each lake. From the results, we found that artificial water control of upper irrigational canal is most important to rehabilitate declined ecosystem in this region. It is concluded that maintenance of water consumption will affect wetlands maintenance and preservation of water fowl.

Transpiration of Cut Branches of Several Species Grown in the Innermongolian Autonomous Region

中国内蒙古の沙地の緑化に用いられている旱柳 (Salix matsudana), 沙柳 (Salix psammophila), 楊柴 (Hedysarum mongolicum), 油蒿 (Artemisia ordosica), ヨシ (Phragmites australis) について, 切り枝水挿し法による蒸散速度の現地測定を行った。同時に気温, 湿度, 照度の環境測定も行った。油蒿を除く4種については, 蒸散速度は, その時点での照度にほぼ比例した。しかし, 油蒿は夜間の蒸散速度も大きく, 照度と蒸散速度に明瞭な関係が認められなかった。また, 今回の水挿し法によって得られた蒸散速度は, 過去に行われた水無し法による数値のよりも小さい。今回の値を用いて油蒿群落からの蒸散量を推定すれば, 940g・m-2・day-1となる。

Transpiration of Sand Dune Plants and Water Economy in the Innermongolian Autonomous Region

中国内蒙古の毛鳥素沙地の自生および導入された植物24種について現地で切り枝重量法によって, 蒸散速度を測定した。葉乾燥重当たりの蒸散係数は, 種によって異なり, 0.7～28.9g・hour-1・g-1の範囲にあった。自生地との関係では, 湿地に自生する種は, 蒸散速度が大きく, 流動砂丘など乾燥の程度が高いところに自生する植物は蒸散速度が小さい傾向にあうた。他地域から導入された緑化植物はとくに蒸散速度が小さかった。安定化した砂丘地の優占植物である油蒿 (Artemisia ordosica) では5.4g・hour-1・g-1であり, 現存葉量から計算すれば, 夏期における群落からの日蒸散量は5mm・day-1と見積もられた。また, 砂丘からの蒸発量は約2mm・day-1であった。