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Information on the rate and pattern of urban expansion is required by urban planners to devise proper urban planning and management policy directions. This study evaluated the dynamics and spatial pattern of Mekelle City's expansion in the past three decades . Multi-temporal Landsat images and Maximum Likelihood Classifier were used to produce decadal land use/land cover (LULC) maps. Changes in LULC and spatial pattern of urban expansion were analysed by post-classification change detection and spatial metrics, respectively. The results showed that in the periods 1984-1994, 1994-2004, and 2004-2014, the built-up area increased annually by 10%, 9%, and 8%, respectively; with an average annual increment of 19% (100 ha year −1 ), from 531 ha in 1984 to 3524 ha in 2014. Between 1984 and 2014, about 88% of the gain in built-up area was from conversion of agricultural lands, which decreased by 39%. Extension of existing urban areas was the dominant growth type, which accounted for 54%, 75%, and 81% of the total new development during 1984-1994, 1994-2004, and 2004-2014, respectively. The spatial metrics analyses revealed urban sprawl, with increased heterogeneity and gradual dispersion in the outskirts of the city. The per capita land consumption rate (ha per person) increased from 0.009 in 1984 to 0.014 in 2014, indicating low density urban growth. Based on the prediction result, the current (2014) built-up area will double by 2035, and this is likely to have multiple socioeconomic and environmental consequences unless sustainable urban planning and development policies are devised.

To determine the means and variations in CH4 uptake and N2O emission in the dominant soil and vegetation types to enable estimation of annual gases fluxes in the forest land of Japan, we measured monthly fluxes of both gases using a closed‐chamber technique at 26 sites throughout Japan over 2 years. No clear seasonal changes in CH4 uptake rates were observed at most sites. N2O emission was mostly low throughout the year, but was higher in summer at most sites. The annual mean rates of CH4 uptake and N2O emission (all sites combined) were 66 (2.9–175) µg CH4‐C m−2 h−1 and 1.88 (0.17–12.5) µg N2O‐N m−2 h−1, respectively. Annual changes in these fluxes over the 2 years were small. Significant differences in CH4 uptake were found among soil types (P < 0.05). The mean CH4 uptake rates (µg CH4‐C m−2 h−1) were as follows: Black soil (95 ± 39, mean ± standard deviation [SD]) > Brown forest soil (60 ± 27) ≥ other soils (20 ± 24). N2O emission rates differed significantly among vegetation types (P < 0.05). The mean N2O emission rates (µg N2O‐N m−2 h−1) were as follows: Japanese cedar (4.0 ± 2.3) ≥ Japanese cypress (2.6 ± 3.4) > hardwoods (0.8 ± 2.2) = other conifers (0.7 ± 1.4). The CH4 uptake rates in Japanese temperate forests were relatively higher than those in Europe and the USA (11–43 µg CH4‐C m−2 h−1), and the N2O emission rates in Japan were lower than those reported for temperate forests (0.23–252 µg N2O‐N m−2 h−1). Using land area data of vegetation cover and soil distribution, the amount of annual CH4 uptake and N2O emission in the Japanese forest land was estimated to be 124 Gg CH4‐C year−1 with 39% uncertainty and 3.3 Gg N2O‐N year−1 with 76% uncertainty, respectively.

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Dielectric sensors have been widely used for nondestructive determination of volumetric soil water content (θ, m3 m−3). Since the output of such sensors is affected by soil temperature (T, °C), the calibration for the effect is indispensable for accurate determination of θ. The objectives of this paper were (i) evaluation of the temperature effects on outputs of the commercial capacitance probes called ECH2O probes for various types of soils, and (ii) to include temperature in empirical calibration equations. Laboratory experiments were performed to obtain probe outputs at various T (5– 35°C) and θ (air‐dry– near‐saturation), using four soils and four probe models with different oscillation frequencies (5 and 70 MHz). The results showed that the outputs linearly responded to T at constant θ for all tested soil–probe combinations. The slope values of the linear responses to T depended on θ. The curves of the output–θ functions at a reference temperature (25°C) varied among the soils and probe models. A calibration equation describing the probe output as a function of θ and T was derived for each soil–probe combination by combining the output–θ function at the reference temperature and the slope–θ function. The derived calibration equations substantially reduced the temperature effects on the probe outputs for all soil–probe combinations. We also briefly considered the theoretical background of temperature effects on the probe outputs based on the results from the experiments and the properties of the soils tested. To demonstrate the importance of temperature calibration, the derived calibration equations were applied to two field observations from arid reasons.

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