Northeast Institute of Geography and Agroecology, Chinese Academy Of Sciences
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Methane Emission Potential from Freshwater Marsh Soils of Northeast China: Response to Simulated Freezing-Thawing Cycles
No full textBoreal wetlands are significant natural sources of methane (CH4) to the atmosphere, and are vulnerable to freezing-thawing cycles (FTC). Nonetheless, the underlying factors that induce CH4 emission in boreal wetlands during FTC are still unclear. Our goal was to characterize soil CH4 emission potential from a freshwater marsh as impacted by FTC and to determine the corresponding mechanisms. We collected soil samples from two soil layers (0-20 and 2040 cm) of an undisturbed freshwater marsh in Sanjiang Plain, Northeast China, and subjected them to various freezing (6 to -6 degrees C) and thawing (-6 to 6 degrees C) cycles. Soil CH4 emission, DOC, and the aromaticity and complexity of DOC indexes were monitored. The results showed that FTC significantly increased CH4 emission potential in the 0-20 cm surface soil layer. The maximum hourly CH4 emission rate was 55.0 mg C m(-2) h(-1), approximately 19 times as high as that of the unfrozen control sample (2.8 mg C m(-2) h(-1)). However, the peak intensity of CH4 emission decreased when the numbers of FTC increased. Meanwhile, FTC not only increased the quantity of DOC released, but also enhanced its instability via increasing the contribution of relatively small, readily degradable organic molecules. Additionally, the CH4 emission potential was significantly correlated with the aromaticity and complexity of DOC, indicating that the release of labile substrates under FTC was one important factor controlling the microbial production of CH4 and the high emissions upon thawing. Our study suggested that global warming-induced increases in seasonal FTC in boreal wetlands may increase CH4 emissions beyond what would occur from long-term temperature increases alone
Spatial and Temporal Variations of Water Quality in Songhua River from 2006 to 2015: Implication for Regional Ecological Health and Food Safety
No full textThe Songhua River is the largest river in northeastern China; the river's water quality is one of the most important factors that influence regional ecological health and food safety in northeastern China and even the downstream of the Heilong River in Russia. In recent years, the Chinese government implemented several water resource protection policies to improve the river's water quality. In order to evaluate the influence of the new policies on the water quality in the Songhua River, water quality data from 2006 to 2015 were collected monthly from the nine sites along the mainstream of the Songhua River. Results show that the water quality in the Songhua River could be divided into two groups during the last 10 years. Before 2010, water quality in the Songhua River was primarily influenced by regional human activities. Industries were the major pollutant sources in the upstream of the Songhua River. After several new policies were implemented by the local government in 2010, water quality in the Songhua River improved. As a result, the biodiversity of fish and ecological health in the Songhua River improved
Mapping the Influence of Land Use/Land Cover Changes on the Urban Heat Island Effect-A Case Study of Changchun, China
No full textThe spatio-temporal patterns of land use/land cover changes (LUCC) can significantly affect the distribution and intensity of the urban heat island (UHI) effect. However, few studies have mapped a clear picture of the influence of LUCC on UHI. In this study, both qualitative and quantitative models are employed to explore the effect of LUCC on UHI. UHI and LUCC maps were retrieved from Landsat data acquired from 1984, 1992, 2000, 2007, and 2014 to show their spatio-temporal patterns. The results showed that: (1) both the patterns of LUCC and UHI have had dramatic changes in the past 30 years. The urban area of Changchun increased more than four times, from 143.15 km(2) in 1984 to 577.45 km(2) in 2014, and the proportion of UHI regions has increased from 15.27% in 1984 to 29.62% in 2014; (2) the spatiotemporal changes in thermal environment were consistent with the process of urbanization. The average LST of the study area has been continuously increasing as many other land use types have been transformed to urban regions. The mean temperatures were higher in urban regions than rural areas over all of the periods, but the UHI intensity varied based on different measurements; and (3) the thermal environment inside the city varied widely even within a small area. The LST possesses a very strong positive relationship with impervious surface area (ISA), and the relationship has become stronger in recent years. The UHI we employ, specifically in this study, is SUHI (surface urban heat island)
Lysinibacillus endophyticus sp. nov., an indole-3-acetic acid producing endophytic bacterium isolated from corn root (Zea mays cv. Xinken-5) (vol 109, pg 1337, 2016)
No full textNitrogen addition in a freshwater marsh alters the quality of senesced leaves, promoting decay rates and changing nutrient dynamics during the standing-dead phase
No full textNitrogen (N) is often the nutrient limiting the decomposability of shoots from macrophytes in wetlands. We aimed to determine the effects of increasing soil N availability on the decomposition of shoots during the standing-dead phase.We measured the quality of senesced leaves from graminoids and their subsequent aerial decay under different N addition treatments (Control, 0 kg N ha(-1) yr.(-1); N60, 60 kg N ha(-1) yr.(-1); N120, 120 kg N ha(-1) yr.(-1); N240, 240 kg N ha(-1) yr.(-1)) in a temperate marsh.Nitrogen addition increased N concentrations in senesced leaves and often increased phosphorus (P) concentrations. The exponential decay constants (k) of leaves from the N120 and N240 treatments were higher than the control treatment during aerial decay. Nitrogen amounts (in percentage terms) remaining in decaying leaves always significantly decreased after N addition, but the effects on P amounts varied with N addition rates. The nutrient amounts remaining in leaves during the standing-dead phase had negative relationships with the initial nutrient concentrations.Soil N availability exerts remarkable effects on the decay process of standing litters by altering the initial quality, and thus the biogeochemical cycling in temperate wetlands
