Although CO₂ flux observations by eddy covariance technique have many advantages, the nocturnal CO₂ efflux remains uncertain. To complement these observations and clarify the carbon budget/dynamics of an apple orchard, we applied an open chamber method and measured the soil respiration rate in September 2006-July 2010 for 237 days. We analyzed the temperature and moisture dependency of the soil respiration rate. The daily soil respiration rate, when normalized by soil temperature, was maximum when soil moisture was at the field capacity, and decreased linearly with the increase and decrease of the soil suction (pF). Excluding the negative effect of the pF, the exponential relationship between the daily soil respiration and the soil temperature became slightly closer, with the determination coefficient increasing from 0.76 to 0.84. The temperature sensitivity indicator Q₁₀ fluctuated inter-annually from 2.0 to 3.1, and seemed to depend on the soil moisture status of each year. We also constructed a mathematical model to calculate the daily soil respiration from the soil temperature and pF. The mean annual soil respiration estimated by the model was 616 gC m^-2, being 208 gC m^-2 lower in 2008 than in 2009. We sampled mowed grass and found that the carbon accumulated was 140 gC m^-2 lower in 2008 than in 2009. The low annual soil respiration in 2008 could be almost entirely explained by the reduced mowed grass production likely caused by the drought conditions of that year.

抄録全体を表示

　Using so-called KATAM, a crop calendar being promoted by the Indonesian government for agricultural risk management, as a case study, the present paper aims to identify factors that affect the extent of use among farmers of meteorological information. To this end, it employed structured interviews with farmers (n = 422) in three different regencies in Java. It also conducted follow-up surveys in two villages during the recent drought to understand how meteorological information was used at the farmer level. This study finds that the importance of meteorological information, as viewed by farmers relative to other factors that also influence farming decisions, differs by location. It is therefore important to understand the contexts of agricultural decision-making in order to exploit the potential benefits of meteorological information. While this study finds a decreasing significance of local knowledge of weather forecasts, it points to the importance of the role of extension workers to help farmers in understanding the implications of meteorological information on their agricultural production and livelihoods. This study also finds that education is the most significant factor for differentiating the use of KATAM, which indicates that the tool may have uneven effects, potentially exacerbating existing inequalities.

抄録全体を表示

　Ground-level ozone (O₃) increases yearly and negatively affects the growth of birches via leaf dynamics. Leaf area is directly related to plant production and is usually reduced by elevated O₃ (eO₃) and insect herbivores. The objective of this study was to explore factors affecting change in leaf number of white birch saplings and insects grazing under eO₃. In order to accomplish this objective, we observed seasonal changes in leaf phenology and determined foliar defense chemicals in saplings grown under ambient air and free-air O₃ enrichment (60 nmol mol^-1 for daytime). The leaf phenology showed the total number of emerged leaves was about 10 per shoot in the control and eO₃ plots. However, the number of attached leaves per shoot at ambient air decreased after mid-July, probably due to grazing by larvae of the leaf beetle. In addition, the concentration of condensed tannin in early leaves was higher in the eO₃ plot than that in the control plot. Such leaves with decreased nutritional value under eO₃ may prevent feeding of leaf beetles. These findings lead to the plausible understanding of an indirect effect of eO₃ on leaf phenology via foliar defense of white birch against insect herbivores.

抄録全体を表示

　Freshwater resources management has become a primary global issue. Improved management of agricultural water is important because agriculture is the dominant user of fresh water. Estimation of evapotranspiration (ET) using satellite imagery is regarded as an effective tool for improving agricultural water management.
　This paper presents the progress made in the development of a global Evapotranspiration-Index (ET_index) estimation algorithm that is applicable to Global Change Observation Mission-Climate (GCOM-C) satellite observation. The algorithm computes an ET-related indicator that is termed the ET_index. The primary input data are thermal observation data from the satellite and near-surface wind speed data from a global climate model. The ET_index is equivalent to the crop coefficient, which has been applied widely for agricultural and irrigation water management around the globe. As a result, the ET_index maps have congruency with traditional agricultural water management methodologies, although the application targets of the ET_index are not limited to irrigation or agriculture.
　The algorithm estimates the ET_index by analyzing the relative position of actual surface temperature between two extreme surface conditions (wet and dry conditions). Estimation of the wet and dry surface temperatures is a key component of the algorithm. The developed model represents the wet and dry surface temperatures with less than 1°C bias and less than 6°C random error in Shenmu, China. The simple structure of the algorithm is designed to process global data with limited computational load. The final product is a 16-day, cloud-free global ET_index map having spatial resolution equal to that of GCOM-C thermal observation. Daily actual ET is estimated from the global ET_index map using local or global weather datasets that include cloudy and rainy days.

抄録全体を表示

　The increase of atmospheric carbon dioxide (CO₂) and tropospheric ozone (O₃) concentrations has affected forest ecosystems both above and below ground. A high dose of O₃ alters stomatal function and accelerates foliar senescence, which lead to changes in assimilation and water use efficiency. Consequently, biomass production and plant growth are suppressed by elevated levels of O₃. In contrast, elevated CO₂ ameliorates these responses of plants to high O₃ via stomatal closure. The harmful effect of O₃ on above ground is indirectly linked with below-ground. Importantly, the fine root dynamics and the relationship with symbiotic fungi are significantly influenced. However, the effects of such a changing environment on forest rhizosphere are still poorly understood. The aim of this study is to analyze the combination effect of CO₂ and O₃ on tree roots and ectomycorrhizae. In particular, we summarize and discuss 1) the response of ectomycorrhizal symbionts (colonization rate, community composition, richness, and diversity) under these environmental stresses; and 2) the root dynamics under elevated CO₂ and O₃ concentrations, along with current methodologies used for root sampling.

抄録全体を表示