Quantitative assessment of decadal water temperature changes in Lake Kasumigaura, a shallow turbid lake, using a one-dimensional model.

To assess the decadal water temperature (WT) changes observed at the center of Lake Kasumigaura, a shallow turbid lake in Japan, we constructed a prediction model for WT. The thermal interactions among air, water, and sediment were simulated by a one-dimensional differential equation using hourly observations of meteorological and limnological parameters. The validated model showed good performance (i.e., <1 °C RMSE for the daily averaged WT) for 2012, 2013, and 2015, respectively, in both upper and lower water layers, which were attained by incorporating a physical sub-model regarding the surface water temperature (surface WT). The good description of seasonal, daily, and hourly changes in surface WT obtained with the sub-model was confirmed by the observed and simulated time series. We then quantified and evaluated the trends of the meteorological and limnological parameters influencing WT changes from 1979 to 2015 based on their effects on WT by using the prediction model with the increases in air temperature (AT), solar radiation (SR), wind velocity (WV), and turbidity during that period; then, WT in the former period (1979) was predicted according to the trends and compared with the measured WT. The observed WT changes during the period were quantitatively explained by the compound effects of the parameters' changes, i.e., the AT and SR raising the WT, and the WV and turbidity lowering the WT.

An overview of the rangelands atmosphere-hydrosphere-biosphere interaction study experiment in northeastern Asia (RAISE).

Intensive observations, analysis and modeling within the framework of the rangelands atmosphere-hydrosphere-biosphere interaction study experiment in northeastern Asia (RAISE) project, have allowed investigations into the hydrologic cycle in the ecotone of forest-steppe, and its relation to atmosphere and ecosystem in the eastern part of Mongolia. In this region, changes in the climate have been reported and a market oriented economy was introduced recently, but their impact on the natural environment is still not well understood. In this RAISE special issue, the outcome is presented of the studies carried out by six groups within RAISE, namely: (1) Land-atmosphere interaction analysis, (2) ecosystem analysis and modeling, (3) hydrologic cycle analysis, (4) climatic modeling, (5) hydrologic modeling, and (6) integration. The results are organized in five relevant categories comprising (i) hydrologic cycle including precipitation, groundwater, and surface water, (ii) hydrologic cycle and ecosystem, (iii) surface-atmosphere interaction, (iv) effect of grazing activities on soils, plant ecosystem and surface fluxes, and (v) future prediction. Comparison with studies on rangelands in other parts of the world, and some future directions of studies still needed in this region are also summarized.

Natural recovery of steppe vegetation on vehicle tracks in central Mongolia.

Steppe desertification due to vehicle travel is a severe environmental issue in Mongolia. We studied natural vegetation recovery on abandoned vehicle tracks in the central Mongolia steppe through vegetation surveys and stable isotopic techniques. The following issues were addressed: (i) invasion of pioneering plant species, (ii) alteration of soil surface features, and (iii) contribution of revegetated plants to soil organic matter (SOM). The pioneering plant species that firstly invaded the abandoned tracks are those that could germinate, root and survive in the compacted track surface. Salsola collina is one of these candidate plants. Due to revegetation, soil surface hardness was reduced. With the improvement of surface microenvironmental conditions, other plants began to colonize and establish; con-comitantly species richness and species diversity increased. Carbon isotope ratios of SOM at the top surface layer indicated that C4 -derived carbon contributed more to SOM in the early phase of recovery and decreased with further recovery.