The hydrology of a wetland largely influences its vegetation, which affects the value of the wetland to human and animal life. Water level fluctuation is one of many factors impacting wetland ecosystem diversity, and precipitation variability is one of the most influential drivers of plant species composition in wetlands. This study describes the effects of water level fluctuation caused by decreased precipitation on the non-submerged aquatic vegetation community in the Nong Bong Khai Lake, Nong Bong Khai Non-hunting Area, Chiang Rai, Thailand. We applied non-submerged aquatic vegetation distribution maps based on images from unmanned aerial vehicle (UAV) at two altitudes (30m and 90 m). Rapid decreases (from 1.0 m to 0.2 m) in the water level from 2018 to 2020 were influenced by lower than average precipitation during 2019 and 2020. Increased terrestrial area (dry land) caused by low water levels offered favorable conditions for terrestrial plant species productivity. The vegetation map generated from a 30-m orthophoto showed a decrease in native plant species and an increase in invasive plant species, most notably a rapid expansion of Mimosa pigra in low water level areas. The distribution map generated by applying a 90-m UAV orthophoto showed Eichhornia crassipes continuously increased during the period of low water level. Mapping revealed that the species declined in the area in March 2020 due to the destruction caused by a heavy hailstorm. Extensive water coverage by Eichhornia crassipes mats might result in low dissolved oxygen values, indicating an increase in pollution in the lake.

I investigated the species diversity of woody plants on the forest floor in a coppice forest where undercutting management has resumed by environmental taxes in Tochigi Prefecture. I set up a 10-year continuous management zone, a 5-year-ago management zone, and a 20-year abandoned zone and measured the population density and tree height of each species in eight 10 m² quadrats. As a result of surveying 24 quadrats, I recorded 3,947 individuals from 47 woody plants growing in the area. In the 10-year continuous management zone and the 5-year-ago management zone, Rhododendron kaempferi and Acer crataegifolium dominated. These species were concentrated in the lower height classes. It was thought that these species would have a small size and survive by sprouting in large numbers with continued undercutting. The species richness and population density increased significantly with management intensity, especially in the 10-year continuous management zone, where the average was as high as 360 individuals/10m². With the resumption of undercutting, the diversity index increased significantly compared to the 20-year abandoned zone. But, there was no increase in the index value in the 10-year continuous management zone where undercutting was continued compared to the 5-year-ago management zone where undercutting was done once. The number of species (r＝－0.906), population density (r＝－0.766), and diversity index (r＝－0.690 to －0.704) were all negatively correlated with the community height of Pleioblastus chino. The lowest correlation coefficient of the diversity index was because some species, such as R. kaempferi and A. crataegifolium, grew prominently in the 10-year continuous management zone.

Addition of bamboo biochar to growing substrate's can enhance substrates' cooling potentials by increasing water holding capacity and surface evaporation rates, which could contribute to the mitigation of urban heat island effect. However, little research has determined the optimum mixing ratio of bamboo biochar for each type of substrate enhancing the substrate's cooling potential. In this study, we added bamboo biochar or coconuts coir (0, 20, and 40％ by volume) to 4 growing substrates used in urban greening (commercial mix using expanded shale for stormwater management, mineral soil sampled from a vacant lot, commercial garden mix using organic materials, coconut coir), and then these substrate samples were potted and heated by using LED lights for 14 days. We found that, among the treatments using bamboo biochar, the blend of 60％ coconut coir and 40％ bamboo biochar showed the best performance for lowering substrate temperature. Additionally, application of bamboo biochar to coconut coir increased water holding capacity and evaporation rates. However, the addition of 40％ bamboo biochar to the commercial mix using expanded shale reduced evapotranspiration rates and increased the substrate temperature. Further research is needed for determining the optimum mixing ratio of bamboo biochar specific to substrate materials, by incorporating varying particle size distributions to treatments.