To understand the magnitudes of temporal variation in soil respiration (Rs) and its spatial heterogeneity, and the effect of abiotic and biotic factors to cause the variation in a young plantation recovering after the clear-cutting of a mature forest, we analyzed 8 year Rs, microclimate, and vegetation data obtained in a young hybrid larch plantation with dense undergrowth of dwarf bamboo Sasa in northern Japan during snow-free periods from 2004 to 2014. Rs was measured by a multichannel automated chamber system and was resolved into two components, temperature sensitivity of respiration, Q10, and temperature-normalized basal respiration at 10°C, R10. Volumetric soil water content affects both seasonal and inter-annual variation of Rs by suppressing R10, whereas soil temperature affects only its seasonal variation. Vegetation recovery had significant effect on both temporal variation and spatial heterogeneity in Rs, although the tree and undergrowth Sasa had different contribution to these variations. Increase in the undergrowth Sasa PAI (plant area index) recovering after clear-cutting increased the Rs through the increase in Q10, whereas the spatial heterogeneity in Rs was increased by the increase in the tree PAI through the increase in R10. These results reveal that the soil water and vegetation has strong effect on the inter-annual variation of Rs and its spatial heterogeneity in the recovering young plantation, in spite of the strong exponential relationship of Rs with Ts in their seasonal variation. Although our results were obtained under the limited range in the inter-annual variation in seasonal mean Ts ( < 2°C), this may not be the unique case only in our study site and gives us a caution when predicting Rs in future warmer environment.
Abrupt temperature drops pose serious concerns for rice production in northern Japan. Previous early warning systems have been based on projected temperature tendencies, and alerts have announced for the occurrence of low temperatures. The rice crop has low-temperature-sensitive stages; however, previous systems have not considered them because of the difficulty of simulating rice growth at the local scale. The forecast system would be more valuable by considering both the rice growth stage and current meteorological forecast techniques. In this study, we synthesized ensemble numerical weather prediction and a cultivar-based rice growth model to forecast 14-day cold damage risk. The ensemble mean forecast with nine members predicted surface air temperatures more skillfully for seven days with lower root-mean-square errors (RMSEs) (1.3-1.9°C) than those of the climatological forecast (2.1-2.4°C) that is derived from historical observations over 30 years. The single deterministic forecast predicted the temperatures better for five days with 1.3-2.0°C of RMSEs, showing the extension of the predictable period by two days with ensemble forecasting. For the cooling degree-days, both the single and ensemble mean forecasts showed lower RMSEs than the climatological forecast throughout the forecast period of 14 days (4.1, 3.8, and 5.2°C at the forecast time = 14 day for single deterministic, ensemble mean, and climatological forecasts, respectively). Although the climatological forecast estimated the rice growth stages reasonably, the performance for cooling degree-days was inferior to the ensemble mean and single deterministic forecasts. The meteorological mean state is sufficient to estimate the rice growth stage, but an accurate temporal pattern of the surface air temperature provided by numerical weather forecast is essential for reliable cold damage forecasting. Moreover, ensemble forecasting is more effective than the single deterministic forecast to reduce prediction errors for both the surface air temperature and cold damage.
Fertilization in farming systems should not only optimize crop yields and soil fertilizer but also maintain soil biodiversity and functions. In young oasis farmland, knowledge regarding soil bacteria respond to fertilization strategies is very limited. We performed a 12-year field experiment to evaluated the effects of organic manure, mineral fertilizer and their combination on a typical young oasis farmland in Northwest China, and quantified soil bacterial diversity and composition by using high-throughput DNA sequencing on the Illumina MiSeq platform. Our results showed that maize yield was highest in the pure organic manure treatment and significantly higher than that of the low mineral fertilizer treatment. Organic manure application significantly increased soil nutrient content, while the organic manure level also positively influenced soil nutrient content. Soil bacterial diversity was more sensitive to the application of organic manure than mineral fertilizer. The PERMANOVA results confirmed that bacterial community composition changed along an organic manure level gradient, which was not observed for mineral fertilizer. Organic manure application promoted the abundance of the copiotrophic group, while the environment resistant group were abundant in the only mineral fertilizer treatments. The present study indicated the critical role of organic manure application for increasing crop yield, soil fertility, and soil bacterial diversity while optimizing the community composition of soil bacteria, emphasizing the contribution and importance of organic manure application to overall soil health.
The mitigation of the urban heat island effect is an important environmental issue for sustainable urban development. We quantified the relative contributions to surface cooling associated with land use changes from an urban center to an urban park using the temperature decomposition method, with one-year paired eddy covariance measurements in Sakai, Japan. The enhanced heat transport efficiency achieved through park creation decreased daytime surface temperatures by 3.9-4.9 K, which was the greatest contribution to daytime surface cooling throughout the season. The disappearance of anthropogenic heat flux due to park creation reduced nighttime surface temperatures by 0.1-0.6 K, which was the greatest contribution at night in summer months. Enhancing heat transport efficiency through urban greening is thus a good mitigation strategy for cooling urban surfaces.