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Ozegahara Mire is the largest alpine mire in Japan. The mire has been preserved as the precious peatland ecosystem with high ecological diversity. After the late 20th century, the mire has been exposed to ecosystem disturbance by mire flooding due to heavy rain as well as invaded Sika deer. Especially, browsing and digging of the mire vegetation by invaded Sika deer have caused considerable impacts on not only vegetation but also physicochemical properties of the mire peat soil. Little information has been published on the effect of flooding and Sika deer disturbance on greenhouse gas emission from the mire. This study aims to provide investigation about the effects of Sika deer disturbance on the soil physicochemical properties and the emission of carbon dioxide (CO2) and methane (CH4) from Ozegahara Mire. Soil and gas samples were collected at 14 fixed plots on 5 sites with and without mire disturbance by Sika deer at eastern Naka-tashiro of Ozegahara Mire through 5 months of 2019 (June to October). Groundwater levels at the study sites were measured each month using hand measurements and continuously using water level loggers. Soil samples were collected with a trowel and gas samples were collected in cylindrical polyvinyl chloride chambers installed on the study sites. Subsequent physicochemical analysis of the soil samples and the gas chromatographic analysis of the gas samples were conducted at the laboratory. Groundwater level displayed similar seasonal change in two sites, being affected by precipitation. The concentrations of NH4+ nitrogen in the disturbed sites were higher than those in the undisturbed sites. Mechanical disturbance of the peat soils by deer resulted in mineralization of organic matter. CO2 and CH4 fluxes from the disturbed sites were lower than those from the undisturbed sites where highest fluxes were recorded in August. Negative correlation was found between CO2 and groundwater level (r = −0.327, p < 0.05), suggesting the importance of groundwater level in greenhouse gas flux. These results indicate the marked influences of the mire disturbance by Sika deer on physicochemical properties of the peat soils and greenhouse gas fluxes at Ozegahara Mire. [ABSTRACT FROM AUTHOR]

Ozegahara Mire is the largest alpine mire in Japan, and it has been preserved as the precious peatland ecosystem under oligotrophic condition. However, after the late 20 century, the mire has been exposed to ecosystem disturbance by invaded Sika deer. Browsing and digging of the mire vegetation by Sika deer have given considerable impacts on not only vegetation but also biochemical property of the peat soil, resulting in the changes in microbiological activities and nutrient dynamics. However, little information has been provided about the effect of deer disturbance on nitrogen (N) dynamics in the mire. This study aims to provide information about the effects of deer disturbance on nitrogen dynamic including N2 fixation and denitrification in Ozegahara Mire. Soil samples were collected at 6 plots on 2 sites with and without mire disturbance by Sika deer at eastern Naka-Tashiro of Ozegahara mire in July 2018. Mineral N contents and other physicochemical properties of the soil samples were measured. N2 fixation and denitrification activities of the soil samples were also measured at different incubation temperatures (15, 20 or 25°C) under either aerobic or anaerobic conditions by acetylene reduction activity (ARA) and inhibition methods, respectively. As results, the ARA in the disturbed sites were lower than those in the undisturbed sites and also lower under aerobic condition than anaerobic condition. Negative correlation was found between ARA and ammonium N in the soil (R2 = 0.353, p< 0.05), suggesting that mechanical disturbance of the peat soils by deer enhanced mineralization of organic N to suppress N2 fixation. ARA was increased by elevated incubation temperature in the undisturbed sites, while no change in the disturbed sites. Denitrification activities was not affected by the disturbance by Sika deer, while higher under aerobic condition than in anaerobic condition, and in higher temperature than lower temperature. Multi-regression analysis of ARA affecting factors revealed that ARA was significantly influenced by temperature, ammonium N and disturbance. These results indicate the marked influences of the mire disturbance by Sika deer on N2 fixation and denitrification activities of the peat soils and N dynamics in Ozegahara Mire. [ABSTRACT FROM AUTHOR]

This study aims to characterize soil chemical properties and microbial biomass, greenhouse gas production, and organic matter dynamics in upland rice field as affected by the long-term fertilizer managements in Uganda. Soil total C (TC) and N (TN) contents were in the relatively smaller range under different fertilizer treatments, even after 20 crop seasons. However, available phosphate contents showed positive correlation with average yield of upland rice. Incubation experiments were conducted under aerobic or under flooding conditions to measure CO2, methane, and nitrous oxide productions. After the incubation, soil samples were extracted to quantify nitrification rate for aerobic condition and ammonification rate for flooding condition. Soil microbial biomass carbon (MBC) and nitrogen were measured. Stable isotope ratio of 13C and 15N were also determined for the soil samples. CO2 production potential under aerobic condition was higher than the flooding condition. The qCO2 (CO2/MBC) in the treatment applied with compost tended to be higher than the other treatments. Positive correlation between nitrous oxide production and nitrification was found. The delta 13C values of the soil samples indicated that the effect of C4 plants before rice cultivation still remained, while the contribution of biological N2 fixation was little according to delta 15N values. These results indicate that soil microbial biomass in upland rice field of the long-term fertilizer experiment in Uganda was characterized with higher qCO2. Greenhouse gas production was affected by fertilizer management, while soil organic C before the long-term experiment still remained in the experiment. [ABSTRACT FROM AUTHOR]

Methane is one of the greenhouse gases emitted from paddy soil ecosystems and may induce global warming and climate change; therefore, mitigation options are urgently required to establish mitigation technology to reduce methane emission without affecting rice production. Methane is produced by a balance between oxidizing agents (such as iron) and reducing agents (easily decomposable soil organic matter), according to the so-called Takai theory. To evaluate options for mitigating methane production potential and to examine the applicability of the Takai theory in Southeast Asian paddy soils, 23 soil samples were collected from Thailand, Indonesia, Philippines, and Vietnam. These soil samples were anaerobically incubated to measure their methane production potential and examined to see whether their chemical properties, such as the ferrous, total iron, and organic matter contents, were correlated. We found a significant negative correlation between the methane production potential and the total iron content, and a positive correlation between the methane production potential and the hexose content, as an index for a soil’s easily decomposable organic matter content. The methane–C/CO2–C production ratio was also positively correlated with the mineralizable nitrogen/ferrous contents ratio, which indicated that the Takai theory, established for Japanese paddy soils, is also useful in Southeast Asian paddy soils and that the soil’s iron content is important to estimate the methane production potential. [ABSTRACT FROM PUBLISHER]

The production/consumption of greenhouse gases (GHG) in soils are of great importance in global warming, but the involved soil physico-chemical and biological characteristics affecting GHG production and consumption potentials are poorly understood in different land-use types. Carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) production/consumption potentials from four land-use types and 10 soil types in central Japan and eastern Hungary, and their relationships with soil characteristics, were investigated. The average of CO2production in Japanese soils was significantly higher than that of Hungarian soils due to the relatively higher microbial biomass carbon (MBC) content. N2O production from both countries' soils did not exhibit a significant difference. Most soils except Japanese paddy and soybean soils showed the potentials for CH4consumption. Forest and grassland soils had relatively higher CO2and N2O production than orchard and cropland soils for both countries. From regression analyses, it could be concluded that soil total nitrogen (TN) and ammonium-nitrogen (NH4+-N) account for 40.8% and 25.5% variations of the soils' CO2and N2O productions, respectively. The CH4consumption was positively correlated with soil carbon/nitrogen (C/N) ratio, while soil MBC availability could account for 15% variation of CH4consumption under aerobic conditions. [ABSTRACT FROM AUTHOR]