@phdthesis{oai:sucra.repo.nii.ac.jp:00019705,
 author = {LEKKALA, VAMSI KRISHNA},
 month = {},
 note = {120p, Understanding the ecophysiology of riparian vegetation is an important factor in managing and promoting biodiversity. Additionally, because riparian vegetation along an elevation gradient is constantly prone to fluctuations in water levels, it is often subjected to environmental stress. The current study examined the effect of elevation on riparian vegetation communities along the Hii River in Japan by quantifying environmental stress using foliar hydrogen peroxide concentrations. Four abundant species occurring along the Hii River, Phragmites australis, Phragmites karka, Juglans mandshurica, and Salix pierotii, were used for the investigation. Leaf samples were collected from all four species at different elevations along the river line. The results indicated that compared to the same species living at high elevations, P. australis,P. karka, and S. pierotii at low elevations had reduced hydrogen peroxide contents, indicating low levels of stress. However, J. mandshurica showed the opposite trend； this species had a high concentration of hydrogen peroxide at low elevations and was thus highly stressed compared to the other species at high elevations. Moreover, J. mandshurica preferred highly fertile soil, especially with regard to the nitrogen content, and J. mandshurica had a high and low hydrogen peroxide content at low and high soil nitrogen, respectively. This clearly indicates that for J. mandshurica, the preferential location and stress was mainly based on soil nutrient availability. Our findings reveal that hydrogen peroxide is a very efficient and reliable index for quantifying environmental stress to help manage biodiversity.
 Plants are subjected to various environmental stressors, both natural and artificial. Environmental stressors that lead to an excessive generation of reactive oxygen species (ROS) may adversely affect physiology and well-being of organisms. The amount of ROS, therefore, could potentially be used to quantify environmental stresses in plants. In this study, the effect of changes of water levels and elevation at which plants are located was examined in the drawdown zone of a flood control dam (Miharu dam), located in Fukushima in northern Japan. The Salix subfragilis willows are important plant species in the reservoir as these plants are resistant to prolonged submerged conditions. S. subfragilis growing in the drawdown zone exhibited high mortality rates from 2008 to 2016. Leaf samples of S. subfragilis were collected in the drawdown zone at different elevations shortly after drawdown (June), and several months after drawdown (August and October). The samples were taken under light exposure; additionally, dark-adapted (30 min) samples were collected in order to evaluate photosystem-induced ROS generation. The mortality rate of S. subfragilis trees was abnormally high over the previous years, particularly at higher elevated sites. Foliar H₂O₂ concentrations were significantly increased in samples collected in August and October samples, compared to June samples. Catalase, ascorbate peroxidase, and guaiacol peroxidase activities were also increased, corresponding with the H₂O₂ content. No significant difference in H₂O₂ concentrations was found between samples from the lower edge of the drawdown zone and those collected at constantly inundated sites. The H₂O₂ concentration of light- and dark-treated samples indicated that there was no additional ROS accumulation due to photosynthesis. The results indicated that the high mortality of the trees was associated with long-term exposure to drought conditions due to the drawdown, although this was not confirmed by conventional monitoring. These findings support the use of H₂O₂ as an environmental stress indicator in vegetation management.
 Egeria densa is an often-found invasive species in Japan, which has spread widely in the past two decades in rivers where no macrophytes had previously been found. As a result, these ecosystems have now become dominated by E. densa. The habitat preference for E. densa colony formation was investigated using the tissue concentrations of hydrogen peroxide (H₂O₂: a reactive oxygen species) under varying conditions in rivers and laboratory conditions. The empirical equations that can describe the macrophyte tissue H₂O₂ formation under various velocity and light conditions were produced. The H₂O₂ concentrations of dark-adapted plants are proportional to the flow velocity, and the surplus H₂O₂ concentration in the light-exposed condition corresponded to the photosystems produced H₂O₂. When the H₂O₂ concentration exceeds 16 μmol/gFW, plant tissue starts to deteriorate, and biomass declines, indicating the critical values required for long-term survival of the plant. The empirically obtained relationships between flow velocity or light intensity and the analysis of H₂O₂ concentration for different slopes and depths of channels found that the H₂O₂ value exceeds the critical H₂O₂ concentration in channels with above 1/100 at around 0.6 m depth. This agrees with the observed results where colonies were not found in channels with slopes exceeding 1/100, and biomass concentration was the largest at depths of 0.6 to 0.8 m. H₂O₂ concentration is quite applicable to understanding the macrophyte condition in various kinds of macrophyte management., Acknowledgements ................................................................................................... 05
Abstract ........................................................................................................... 06
List of Figures .................................................................................................... 09
List of Tables ..................................................................................................... 12

Chapter I : Introduction ........................................................................................... 13
1.1 Riparian vegetation ............................................................................................ 13
1.2 Importance of riparian vegetation .............................................................................. 15
1.3 Description of research problem ................................................................................ 17
1.4 Objective of study ............................................................................................. 18
1.5 Importance of study ............................................................................................ 18
1.6 Outlines and constraint ........................................................................................ 19
References ......................................................................................................... 20

Chapter II : Literature review ..................................................................................... 22
2.1 Riparian vegetation structure and variations.................................................................... 22
2.2 Types of riparian vegetation ................................................................................... 23
2.3 Types of threats to riparian vegetation ........................................................................ 23
2.4 Riparian vegetation Management Practices ....................................................................... 25
2.5 Chemical assays for riparian vegetation Management ............................................................. 27
2.6 Riparian macro phytic environment............................................................................... 27
2.7 Macrophytes management ......................................................................................... 28
2.8 Restoration of macrophytes ..................................................................................... 30
References ......................................................................................................... 32

CHAPTER III : Spatial pattern of foliar hydrogen peroxide concentration and its implication in riparian vegetation management ............................................................... 37
3.1 Introduction ................................................................................................... 37
3.2 Observation site ............................................................................................... 37
3.3 Methodology .................................................................................................... 40
 3.3.1 Soil and leaf sampling ...................................................................................... 40
 3.3.2 Determination of photosynthetic Pigments ................................................................ 43
 3.3.3 Plant tissue preparation for the Stress Assay ............................................................... 43
 3.3.4 H₂O₂ concentrations ......................................................................................... 43
 3.3.5 CAT activity ................................................................................................ 43
 3.3.6 APX activity ................................................................................................ 44
 3.3.7 Total Carbon, total nitrogen and total phosphorus in sediment ................................... 44
3.4 Results ........................................................................................................ 45
 3.4.1 H₂O₂ concentration related to site elevation ............................................................... 45
 3.4.2 H₂O₂ concentration related to edaphic condition ........................................................ 45
 3.4.3 Chlorophyll content and H₂O₂ concentration .............................................................. 48
 3.4.4 CAT activity of plants ...................................................................................... 49
 3.4.5 Site elevation and plant distribution ....................................................................... 50
3.5 Discussion ..................................................................................................... 52
 3.5.1 Site elevation and vegetation colonization ................................................................. 52
 3.5.2 Soil nutrient and plant stress .............................................................................. 54
 3.5.3 Site elevation and plant stress ............................................................................. 55
 3.5.4 Plant stress and antioxidant activities ..................................................................... 55
 3.5.5 Tissue H₂O₂ concertation in vegetation management ................................................. 56
3.6 Conclusion ..................................................................................................... 57
References ......................................................................................................... 58

CHAPTER IV : Impact of regulated water levels on willows (Salix subfragilis) at a floodcontrol
dam, and the use of hydrogen peroxide as an indicator of environmental stress.................................................................................................................................................. 63
4.1 Introduction ................................................................................................... 63
4.2 Observation site ............................................................................................... 66
4.3 Methodology .................................................................................................... 67
 4.3.1 Determination of H₂O₂, CAT, APX, and POD via assays ........................................... 68
4.4 Results ........................................................................................................ 70
 4.4.1 Relationship between quadrant elevation and number of trees .................................. 70
 4.4.2 Effect of hydrogen peroxide concentration on Salix subfragilis .............................. 71
 4.4.3 Effect of soil moisture on Salix subfragilis ................................................................ 72
 4.4.4 Effect of coverage by Sciyos angulatus L. ................................................................ 73
 4.4.5 Effect of light and dark treatment on Salix subfragilis leaves .................................... 73
 4.4.6 Effect of antioxidant activities ............................................................................ 74
4.5 Discussion ..................................................................................................... 76
 4.5.1 Role of soil moisture for the survival of S.Subfragilis................................................ 76
 4.5.2 Effect on photosynthetic pigments ........................................................................... 77
 4.5.3 The effect of a long period inundation on the early mortality of Salix subfragilis ... 79
 4.5.4 Effect of Antioxidant activities ............................................................................ 79
4.5.5 Effect of coverage by Sicyos angulatus L. ................................................................ 80
4.6 Conclusion ..................................................................................................... 81
References ......................................................................................................... 82

CHAPTER V: Evaluation of habitat preferences of invasive macrophyte Egeria densa in different channel slopes using hydrogen peroxide as an indicator .................................. 85
5.1 Introduction ................................................................................................... 85
5.2 Methodology .................................................................................................... 89
 5.2.1 Field observations .......................................................................................... 89
 5.2.2 Laboratory experiments ...................................................................................... 91
 5.2.3 Chemical and biomass analyses ............................................................................... 92
 5.2.4 Statistical comparison ...................................................................................... 92
5.3 Results ........................................................................................................ 94
 5.3.1 Diurnal H₂O₂ variation of E. densa .......................................................................... 99
5.4 Discussion .................................................................................................... 104
 5.4.1 Environmental stressors on E. densa ........................................................................ 104
 5.4.2 Threshold condition of E. densa mortality ............................................................... 107
 5.4.3 Empirical expression of habitat preference and colonizableconditionsimulation................................108
 5.4.4 E. densa colonization in rivers ............................................................................ 110
5.5 Conclusion .................................................................................................... 113
References ........................................................................................................ 114

Chapter VI: Conclusion ............................................................................................ 119, 指導教員 : FUJINO, Takeshi, text, application/pdf},
 school = {埼玉大学},
 title = {Study on stress environmental response of riverbank plants for the purpose of applying watershed environmental management},
 year = {2021},
 yomi = {レッカ, ヴァムシ クリシュナ}
}