| Reduced groundwater levels has caused drying and shrinkage of mires、 resulting in rapid changes in wetland vegetation. To conserve preexistent wetland vegetation、 it is important to clarify its behavior in relation to fluctuations in groundwater levels. Sarobetsu Mire、 biggest high moor in Japan、 is experiencing a transition of wetland vegetation due to an increase in the invasion of dwarf bamboo (Sasa (Eusasa)). Previous studies were limited to qualitative assessment concluding that the reduction of wetland vegetation areas. The invasion of dwarf bamboo was inhibited in areas with high groundwater levels、 and few studies have sought to quantitatively assess the responses of individual plants to groundwater levels. The activity of the crop has often been measured by the triphenyl-tetrazolium-chloride (TTC) method、 which is a simple approach. The purpose of this study is to develop a quantitative assessment method for the responses (activities) of wetland vegetation to groundwater levels. To examine the relationship between groundwater levels and wetland vegetation activity (i.e.、 whether plants are dead or alive)、 two laboratory experiments were conducted using the TTC method and absorptimetry with dwarf bamboo that were collected in Sarobetsu Mire. The first experiment was to investigate the activity of wetland vegetation in inundated environment、 and the second was to investigate an annual fluctuation of the activity of wetland vegetation. [*]Activity (absorbance) of dwarf bamboo continued to decrease immediately after collection、 and the absorbance peak at a wavelength of 480 nm was also smaller. However、 after the submersion period exceeded 30 days、 there were no significant changes in absorbance as the submersion period went on. This indicates that dwarf bamboo underwent activity loss and died when the submersion period exceeded 30 days. Dwarf bamboo was considered dead when absorbance (480 nm) was 0.2 or lower and the peak became unclear. Since the change in absorbance was the largest for dwarf bamboo at 480 nm、 comparison at this wavelength was considered effective for activity judgment. This result indicated the feasibility of quantitative assessment for the activities of underground rhizomes of dwarf bamboo using TTC dyeing. The activity of dwarf bamboo is the lowest in July (summer)、 rise from July to December (summer ~ winter)、 is flat or falling tendency from December to May (winter ~ spring)、 and takes a nosedive from June to July (spring ~ summer). Activity of Rhizomes was low from June to August、 because activity of the rhizome (nutrition) moved to the aerial part to supply nutrients to the shoots. Growth of the aerial part became calm、 so nutrient is stored in rhizome since September. [*]In the future、 groundwater levels are expected to increase due to the restoration of river meanders as part of nature restoration projects、 as well as in response to changes in hydrological environments caused by influences such as climate changes. It will be necessary to verify the response of activities to groundwater levels using the TTC assessment method for various types of wetland vegetation and to promote verification in field tests. |
