Impacts of Agricultural Expansion (1910s-2010s) on Water Cycle in the Songneng Plain, Northeast China

Agricultural expansion is one of the primary land use changes on the Earth’s surface. The Songnen Plain in Northeast China is renowned for its Black Soil and is one of the most important agricultural regions of this country. In the last century, its population increased 20-fold and excessive areas of grassland were cultivated. Based on a series of decadal land use/land cover data sets in the plain (1910s–2010s), this study simulated the water balance in each decade using the Weather Research and Forecasting (WRF) model and assessed the water effects of centurial agricultural expansion. Six variables were simulated to explain the land-atmosphere interaction: precipitation, total evapotranspiration, canopy transpiration, canopy interception evaporation, land evaporation and land surface runoff and infiltration. Agreeing with historical climate reanalysis data, the simulated precipitation in the plain did not have a significant trend. However, the total evapotranspiration significantly increased in the study region. The canopy transpiration and interception evaporation increased and the runoff and infiltration decreased, both indicating a drought effect in soil. The drying trend varied spatially with the strongest pattern in the central plain where large areas of wetlands remain. As a consequence of agricultural expansion, the centurial drying process in the fertile Black Soil may put strong pressure on the crop productivity and food safety of this important agricultural region

Environmental Influences on Forest Fire Regime in the Greater Hinggan Mountains, Northeast China

Fires are the major disturbances in the Greater Hinggan Mountains, the only boreal forest in Northeast China. A comprehensive understanding of the fire regimes and influencing environmental parameters driving them from small to large fires is critical for effective forest fire prevention and management. Assisted with satellite imagery, topographic data, and climatic records in this region, this study examines its fire regimes in terms of ignition causes, frequencies, seasonality, and burned sizes in the period of 1980–2005. We found an upward trend for fire occurrences and burned areas and an elongated fire season over the three decades. The dates of the first fire in a year did not vary largely but those of the last fire were significantly delayed. Topographically, spring fires were prevalent throughout the entire region, while summer fires mainly occurred at higher elevations under severe drought conditions. Fall fires were mostly human-caused in areas at lower elevations with gentle terrains. An ordinal logistic regression revealed temperature and elevation were both significant factors to the fire size severity in spring and summer. Other than that, environmental impacts were different. Precipitation in the preceding year greatly influenced spring fires, while summer fires were significantly affected by wind speed, fuel moisture, and human accessibility. An important message from this study is that distinct seasonal variability and a significantly increasing number of summer and fall fires since the mid-1990s suggest a changing fire regime of the boreal forests in the study area. The observed and modeled results could provide insights on establishing a sustainable, localized forest fire prevention strategy in a seasonal manner

Environmental Influences on Forest Fire Regime in the Greater Hinggan Mountains, Northeast China

Fires are the major disturbances in the Greater Hinggan Mountains, the only boreal forest in Northeast China. A comprehensive understanding of the fire regimes and influencing environmental parameters driving them from small to large fires is critical for effective forest fire prevention and management. Assisted with satellite imagery, topographic data, and climatic records in this region, this study examines its fire regimes in terms of ignition causes, frequencies, seasonality, and burned sizes in the period of 1980–2005. We found an upward trend for fire occurrences and burned areas and an elongated fire season over the three decades. The dates of the first fire in a year did not vary largely but those of the last fire were significantly delayed. Topographically, spring fires were prevalent throughout the entire region, while summer fires mainly occurred at higher elevations under severe drought conditions. Fall fires were mostly human-caused in areas at lower elevations with gentle terrains. An ordinal logistic regression revealed temperature and elevation were both significant factors to the fire size severity in spring and summer. Other than that, environmental impacts were different. Precipitation in the preceding year greatly influenced spring fires, while summer fires were significantly affected by wind speed, fuel moisture, and human accessibility. An important message from this study is that distinct seasonal variability and a significantly increasing number of summer and fall fires since the mid-1990s suggest a changing fire regime of the boreal forests in the study area. The observed and modeled results could provide insights on establishing a sustainable, localized forest fire prevention strategy in a seasonal manner

Remote Sensing of Soil Alkalinity and Salinity in the Wuyu’er-Shuangyang River Basin, Northeast China

The Songnen Plain of the Northeast China is one of the three largest soda saline-alkali regions worldwide. To better understand soil alkalinization and salinization in this important agricultural region, it is vital to explore the distribution and variation of soil alkalinity and salinity in space and time. This study examined soil properties and identified the variables to extract soil alkalinity and salinity via physico-chemical, statistical, spectral, and image analysis. The physico-chemical and statistical results suggested that alkaline soils, coming from the main solute Na2CO3 and NaHCO3 in parent rocks, characterized the study area. The pH and electric conductivity (EC ) were correlated with both narrow band and broad band reflectance. For soil pH, the sensitive bands were in short wavelength (VIS) and the band with the highest correlation was 475 nm (r = 0.84). For soil EC, the sensitive bands were also in VIS and the band with the highest correlation was 354 nm (r = 0.84). With the stepwise regression, it was found that the pH was sensitive to reflectance of OLI band 2 and band 6, while the EC was only sensitive to band 1. The R2Adj (0.73 and 0.72) and root mean square error (RMSE) (0.98 and 1.07 dS/m) indicated that, the two stepwise regression models could estimate soil alkalinity and salinity with a considerable accuracy. Spatial distributions of soil alkalinity and salinity were mapped from the OLI image with the RMSE of 1.01 and 0.64 dS/m, respectively. Soil alkalinity was related to salinity but most soils in the study area were non-saline soils. The area of alkaline soils was 44.46% of the basin. Highly alkaline soils were close to the Zhalong wetland and downstream of rivers, which could become a severe concern for crop productivity in this area

Object-Based Crop Classification with Landsat-MODIS Enhanced Time-Series Data

Cropland mapping via remote sensing can provide crucial information for agri-ecological studies. Time series of remote sensing imagery is particularly useful for agricultural land classification. This study investigated the synergistic use of feature selection, Object-Based Image Analysis (OBIA) segmentation and decision tree classification for cropland mapping using a finer temporal-resolution Landsat-MODIS Enhanced time series in 2007. The enhanced time series extracted 26 layers of Normalized Difference Vegetation Index (NDVI) and five NDVI Time Series Indices (TSI) in a subset of agricultural land of Southwest Missouri. A feature selection procedure using the Stepwise Discriminant Analysis (SDA) was performed, and 10 optimal features were selected as input data for OBIA segmentation, with an optimal scale parameter obtained by quantification assessment of topological and geometric object differences. Using the segmented metrics in a decision tree classifier, an overall classification accuracy of 90.87% was achieved. Our study highlights the advantage of OBIA segmentation and classification in reducing noise from in-field heterogeneity and spectral variation. The crop classification map produced at 30 m resolution provides spatial distributions of annual and perennial crops, which are valuable for agricultural monitoring and environmental assessment studies

Dcc Regulates Asymmetric Outgrowth of Forebrain Neurons in Zebrafish

The guidance receptor DCC (deleted in colorectal cancer) ortholog UNC-40 regulates neuronal asymmetry development in Caenorhabditis elegans, but it is not known whether DCC plays a role in the specification of neuronal polarity in vertebrates. To examine the roles of DCC in neuronal asymmetry regulation in vertebrates, we studied zebrafish anterior dorsal telencephalon (ADt) neuronal axons. We generated transgenic zebrafish animals expressing the photo-convertible fluorescent protein Kaede in ADt neurons and then photo-converted Kaede to label specifically the ADt neuron axons. We found that ADt axons normally project ventrally. Knock down of Dcc function by injecting antisense morpholino oligonucleotides caused the ADt neurons to project axons dorsally. To examine the axon projection pattern of individual ADt neurons, we labeled single ADt neurons using a forebrain-specific promoter to drive fluorescent protein expression. We found that individual ADt neurons projected axons dorsally or formed multiple processes after morpholino knock down of Dcc function. We further found that knock down of the Dcc ligand, Netrin1, also caused ADt neurons to project axons dorsally. Knockdown of Neogenin1, a guidance receptor closely related to Dcc, enhanced the formation of aberrant dorsal axons in embryos injected with Dcc morpholino. These experiments provide the first evidence that Dcc regulates polarized axon initiation and asymmetric outgrowth of forebrain neurons in vertebrates

Phenology-assisted classification of C3 and C4 grasses in the U.S. Great Plains and their climate dependency with MODIS time series

Grassland ecosystems in the North America are primarily composed of C3 and C4 plant functional types (PFTs) that have different responses to the changing climate. Knowledge of their spatial distributions and temporal var- iations helps us better understand the ecological functions and climate dependencies of grasslands. This study used the 500-m MODIS surface reflectance products (MOD09A1) from 2000 to 2009 to extract NDVI time series of C3 and C4 grass PFTs in different floristic regions (tallgrass, shortgrass, and mixed-grass prairies.) A set of phe- nology metrics, including Start of Season, End of Season, Season Length, Peak NDVI, Peak Date, and ∑NDVI, were found useful in delineating these grass types. A phenology-assisted decision tree classifier was developed to map the four grass PFTs in the Great Plains. The relative abundance of C3 and C4 PFTs generally showed the expected latitudinal shifts. Longitudinal shifts of tallgrass and shortgrass PFTs were also in agreement with the distributions of floristic prairie regions. In shortgrass and northern mixed prairies, shortgrass C3 was located in the north while shortgrass C4 was in the south. The native tallgrass C4 remained in prairie remnants, although other native grasslands had been mostly converted to croplands or tallgrass C3-dominated pastures. The interannual spatial variations of PFTs were statistically correlated with climate factors over a 10-year study period. The preliminary findings revealed that the strength and direction of correlations varied geographically and sea- sonally for different PFTs. This spatio-temporally explicit information may provide quantitative inputs in ecological forecasting for various climate change scenarios

Adsorption of Arsenite by Six Submerged Plants from Nansi Lake, China

Nansi Lake is the largest and the most important freshwater lake in north China for the South-North Water Transfer Project. Due to long-time and large-scale fish farming of history, the excess fish food and excretion usually release pentavalent arsenic, which is converted into trivalent arsenic (As (III)) in the lake sediment and released into lake water. Adsorption of arsenite using six submerged plants (Mimulicalyx rosulatus, Potamogeton maackianus, Hydrilla, Watermifoil, Pteris vittata, and Potamogeton crispus) as adsorbing materials was investigated. The experimental data obtained have been analyzed using Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models and the pseudo-first-order, pseudo-second-order, and intraparticle diffusion kinetics models. According to the results, the As (III) equilibrium data agreed well with the Freundlich isotherm model. The adsorption capacity of the plants was in the following order: Potamogeton crispus > Pteris vittata > Potamogeton maackianus > Mimulicalyx rosulatus > Hydrilla > Watermifoil. The sorption system with the six submerged plants was better described by pseudo-second-order than by first-order kinetics. Moreover, the adsorption with Potamogeton crispus could follow intraparticle diffusion (IPD) model. The initial adsorption and rate of IPD using Potamogeton crispus and Pteris vittata were higher than those using other plants studied

500-year growth cycle of stalagmite and its response to regional hydrological changes in Heshang cave, western Hubei

Stalagmitesare important high-resolution paleoclimate archives, and possess abundant physical, chemical and microbial paleoclimate proxies. Among of them, the growth rate (GR)of stalagmites quite popular because its easy access and non-destruction.However, the environmental implicationsof GR are still ambiguous due to the complex influence factors. Here we established the GR series span past 8.8 ka of HS4 stalagmite came from the Heshang Cave located in the middle reaches of Yangtze River. It was found that the GR of HS4 stalagmite showed two stages in the millennial timescale: the low and stable GR duration between 8.8 and 5.0 ka BP and the high and fluctuated GR duration since 5.0 ka BP. Above millennial variation is negative correlated with the intensity of regional summer monsoon and positive correlated with the frequency of El Nino and regional paleo-hydrological condition. The GR of HS4 stalagmite exhibited a significant 500-year cycle with confidence level more than 99%. The centennial periodic GR variation coincide well with the occurrence of regional heavy precipitation with the higher frequency of heavy precipitation correspond to the faster GR, and this correlation is especially significant in the Late Holocene. but which was forcing by considering the regional precipitation in millennial and centennial time scale were mainly affected direct or indirectly by the solar radiation and El Nino-Southern Oscillation (ENSO) activity, we conclude that the GR of HS4 stalagmite is mainly controlled by the regional effective precipitation forcing by the solar radiation and ENSO activity, showing the greater the rainfall the faster the growth rate

Removal of Arsenite from Water by Ce-Al-Fe Trimetal Oxide Adsorbent: Kinetics, Isotherms, and Thermodynamics

Ce-Al-Fe trimetal oxide adsorbent was prepared. The morphology characteristics of the new adsorbent were analysed by the transmission electron microscope (SEM) method. The SEM results implied its ability in the adsorption of As (III). To verify the analyses, bench-scale experiments were performed for the removal of As (III) from water. In the experiments of adsorption, As (III) adsorption capacity of the trimetal oxide adsorbent was presented significantly higher than activated aluminium oxide and activated carbon. As (III) adsorption kinetics resembled pseudo-second-order adsorption mode. When initial As (III) concentration was 3, 8, and 10 mg·L−1, the maximum adsorption capacity achieved was 1.48, 3.73, and 5.12 mg·g−1, respectively. In addition, the experimental adsorption data were described well by the Freundlich adsorption isotherm model at 20, 30, and 40°C. The enthalpy change (ΔS), the standard free energy (ΔG), and entropy change (ΔH) indicated that the nature of As (III) adsorption was exothermic and spontaneous with increasing randomness on the interface of solid and liquid. And the adsorption mechanism can be interpreted as chemisorption with As (III) multilayer coverage formation on the adsorbent surface