Biochar is becoming a popular soil amendment for achieving sustainable agriculture. It is important to identify biochar’s optimal application rates by testing a wide range of biochar application rates for increasing yields while reducing nitrogen leaching. We grew leaf lettuce (Lactuca sativa var. crispa) for consecutive two cropping cycles (four weeks each) in the laboratory experiment using pots filled with loamy Andosols mixed with biochar (0, 50, 100, 150 t/ha) and organic fertilizer (100, 200 kg-N/ha). In the first cropping cycle, nitrogen leaching decreased in samples having biochar application rates of 150 t/ha or more for either fertilizer application rate (100 or 200 kg-N/ha) (p < 0.025). For the fertilizer application rate of 200 kg-N/ha, yields were not significantly different for samples having biochar application rates between 0-150 t/ha. In the second cropping cycle, samples having 100-150 t/ha of biochar had higher yields than the control group for either fertilization rate (100 or 200 kg-N/ha) (p < 0.025). We recommend the application rate of 150 t/ha of biochar and 200 kg-N/ha of organic fertilizer, aiming to balance yield and nitrogen leaching for growing green leafy vegetables, while further longitudinal research is needed for testing biochar application for border ranges of crop, soil, and / or fertilizer types.

There is an interest in cultivating native plants on drought-prone artificial grounds in green spaces on for biodiversity conservation. Biochar, produced from organic matters, is expected to be introduced as a soil conditioner which can improve water holding capacity. However, there are few studies which had focused on the impacts of application of biochar on the health conditions of Japanese native plants. In order to clarify the effectiveness of biochar as a soil conditioner, current study cultivated three Japanese native plants (e.g. Imperata cylindrica, Platycodon grandiflorus and Potentilla hebiichigo) with bamboo or wood biochar in the experiment. The results indicated that the health conditions of the leaves only in I. cylindrica was kept well by biochar application at rate of 20％ and 40％, and thus the impacts of biochar application to soils could be differed by plant species.

On Chichijima Island in the Ogasawara Islands, where ecological impacts of invasive rodents are of concern, this study aimed to quantitatively evaluate the feeding preference and feeding pressure of the Rattus rattus on plant stems and leaves. We conducted route censuses to record shoot damage caused by R. rattus, calculated species-specific palatability indices, and compared their distributions among endemic, cosmopolitan, and alien plant species. We also defined local feeding pressure as the palatability threshold above which plant species experienced shoot damage and calculated feeding pressure for each survey route. We found that some endemic species exhibited particularly high palatability. The median of the palatability frequency distribution among plant species did not differ significantly among species groups. In contrast, the presence of highly palatable endemic species suggested greater interspecific variability in palatability within endemics, although this tendency was weak. Feeding pressure along survey routes tended to be higher at higher elevations. Because remnant dry scrub forests at higher elevations on Chichijima Island include many highly palatable plant species, vegetation type may be associated with R. rattus density. This study quantitatively evaluated the impacts of invasive rodents on vegetation on an oceanic island and provides insights relevant to future conservation and management.

This study clarified the seed germination rates and seedling emergence and survival conditions of Patrinia scabiosifolia growing in the Nishinohara grasslands at the foot of Mt. Sanbe, Shimane Prefecture. We conducted germination tests in incubators and in a field. The incubators were set under dark light condition to either a constant temperature of 25°C or an alternating temperature regime of 10°C and 25°C for 12 h each (hereinafter, 10/25°C). In the field, we set five soil conditions (soil, litter, charcoal, decomposed granite soil, or gravel) and two light conditions (bright condition with 22% shading and dark condition with 51% shading). The results revealed that seeds did not germinate at 25°C but had a germination rate of 22.8% at 10/25°C. In the field, large numbers of seedlings emerged in soil and charcoal under both light conditions, but none emerged in gravel. In soil and charcoal, seedlings emerged almost immediately under a period of temperature increase and continuous rainfall in late June. The highest rate (27.3%) was observed in soil under dark conditions, exceeding even the incubator germination rates. These findings suggest that P. scabiosifolia germination may be facilitated by rapidly changing moisture conditions following a period of dryness. However, all seedlings under all conditions died during a 27-day period in August with no rainfall and an average daily temperature of about 30°C, indicating that summer drought has a strong and negative effect on P. scabiosifolia seedling survival.