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CHAPTER VI
Conclusion
Recently managing the vegetation seems to be a potential problem in several places around the
globe. Although, there are several approaches that are being tested on trial-and-error bases
there is not any suitable method developed yet to help manage the biodiversity. There are
several traditional techniques which are being followed by several vegetation management
authorities but unfortunately, they are time consuming and the costly methods.
The results of the current study show the effect of elevation gradient and moisture variation
on the abundance of different species along a riparian zone. Species-specific zones of
colonization or recruitment were clearly revealed using hydrogen peroxide as an environmental
stress quantification index. Additionally, because most plant species face environmental stress,
the current study proposes a rapid, efficient, and reliable monitoring system for vegetation
management. With this method, only a relatively simple chemical analysis is involved when
assessing oxidative stress, which is measured in the form of the hydrogen peroxide content. In
measuring oxidative stress, it is important to truly understand the intensity of the stress, predict
probable outcomes, and take appropriate measures to protect vegetation accordingly.
Flexible management-based methods are commonly used in the ecological management of
riparian systems, where long-term monitoring of vegetation is conducted to identify stressors.
Salix trees growing in this area have been monitored for 8 years in order to gain a better
understanding of the mechanisms driving their high mortality. However, the responsible
stressor was not identified solely from monitoring, as the change in Salix health was due to
prolonged stress conditions. In this study, one ROS, H2O2,was identified as the primary cause
of the increase in Salix mortality based on relatively straightforward analyses, and our results
suggest that H2O2 levels can be used as an effective indicator of environmental stress levels
and plant condition.
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Salix are inundation-tolerant species often found along reservoir shorelines and are capable of
colonizing the drawdown zones of flood-control dams, which otherwise would remain devoid
of vegetation. These individuals are vulnerable to water stress during periods of water
drawdowns, however. Oxidative stress levels of the inundated trees included in our study were
as low as those of trees recently exposed following inundation, suggesting that one potential
measure for reducing stress levels in Salix would be to supply additional water to the colony.
Several studies have shown that Salix require high soil moisture in order to germinate but we
recommend that soil moisture content be maintained at appropriate levels even for mature trees.
The high concentrations of H2O2 introduced by high flow velocity and high solar radiation
in summer inhibited the formation of large colonies in the gravel channel, owing to the high
oxidative stress. The accumulation of H2O2 in E. densa showed a significant relationship for
both flow velocity and solar radiation. The critical H2O2 concentration to maintain a healthy
population of E. densa can be considered as 16 µmol/gFW, which corresponds to the
termination of biomass accumulation. Under the strongest solar radiation on summer days, the
H2O2 level often exceeds the critical condition, leading to the deterioration of E. densa and
ultimately, the H2O2 concentrations decline as the plant tissues start to deteriorate. H2O2
concentrations of E. densa were estimated for channels with different slopes and different
depths. The H2O2 concentration is higher than the critical value in shallow water and increases
in steeper channels, exceeding the critical value at a channel slope larger than 1/100. Once
colonized, E. densa accumulates sandy suspended sediment efficiently and creates a preferable
environment for further colonization. The present methodology can be applied to predict the
area that can be conveniently colonized by E. densa within a short time period, which has been
determined based on a prolonged monitoring activity.
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