Biophysical Effects of Temperate Forests in Regulating Regional Temperature and Precipitation Pattern across Northeast China

The temperate forests in Northeast China are an important ecological barrier. However, the way in which temperate forests regulate the regional temperature and water cycling remains unclear. In this study, we quantitatively evaluated the role that temperate forests play in the regulation of the regional temperature and precipitation by combining remote sensing observations with a state-of-the-art regional climate model. Our results indicated that the forest ecosystem could slightly warm the annual air temperature by 0.04 ± 0.02 °C and bring more rainfall (17.49 ± 3.88 mm) over Northeast China. The temperature and precipitation modification function of forests varies across the seasons. If the trees were not there, our model suggests that the temperature across Northeast China would become much colder in the winter and spring, and much hotter in the summer than the observed climate. Interestingly, the temperature regulation from the forest ecosystem was detected in both forested regions and the adjacent agricultural areas, suggesting that the temperate forests in Northeast China cushion the air temperature by increasing the temperature in the winter and spring, and decreasing the temperature in the summer over the whole region. Our study also highlights the capacity of temperate forests to regulate regional water cycling in Northeast China. With high evapotranspiration, the forests could transfer sufficient moisture to the atmosphere. Combined with the associated moisture convergence, the temperate forests in Northeast China brought more rainfall in both forest and agricultural ecosystems. The increased rainfall was mainly concentrated in the spring and summer; these seasons accounted for 93.82% of the total increase in rainfall. These results imply that temperate forests make outstanding contributions to the maintainance of the sustainable development of agriculture in Northeast China.

Treatment of Polluted Urban Surface Waters by Sponge Based Aerobic Biofilm Reactor: Purification Performances and Resilience

Surface waters are suffering continuous discharging of pollutions, and low DO and black-odorous were easily formed, especially in those slow-flowing urban lakes and enclosed small ponds. In-situ treatment by artificial aeration or water cycling with a combination of polyurethane sponge as biofilm carriers can disentangle this situation without any land occupation. Long-term continuous experiments (187 days) showed that indigenous microorganisms in urban surface waters could form biofilms in the novel style of sponge-based aerobic biofilm reactors (SABRs). In urban lake waters treatment, the purification performances of SABRs were stable and resilient as the NH4+-N and NO2−-N removals were steady, even facing the abrupt increase of NH4+-N and NO2−-N concentrations in influent. Enhancing the polyurethane sponge filling ratios in SABRs can reduce DO but did not affect NH4+-N removal. SABRs were also able to treat enclosed surface waters or black-odorous waterbodies. Combined SABRs with water cycling, NH4+-N removal time was shorter than the time needed by water cycling when biodegradable organic matter was not present. The massive biodegradable organic matter could inhibit nitrification and prolong the purification time. Further results showed that organic matter could be used as carbon sources to eliminate the produced NO3−-N in SABRs. Therefore, the developed new bioreactor could act as one effective way for treating N-polluted urban surface waters.