Relative Contributions of Spatial and Environmental Processes and Biotic Interactions in a Soil Collembolan Community

Understanding the underlying processes of how communities are structured remains a central question in community ecology. However, the mechanisms of the soil animal community are still unclear, especially for communities on a small scale. To evaluate the relative roles of biotic interactions and environmental and spatial processes in a soil collembolan community, a field experiment was carried out on a small scale(50 m) in the farmland ecosystem of the Sanjiang Plain, Northeast China. In August and October, 2011, we took 100 samples each month in a 50 m × 50 m plot using a spatially delimited sampling design. Variation partitioning was used to quantify the relative contributions of the spatial and environmental variables. A null model was selected to test for the non-randomness pattern of species co-occurrence and body size in assemblages of collembolans and to test whether the pattern observed was the result of environmental or biotic processes that structured the community on a small scale. The results showed that large variance was accounted for by spatial variables(18.99% in August and 21.83% in October, both were significant). There were relatively lower effects of environmental variation(3.56% in August and 1.45% in October, neither was significant), while the soil water content, soil p H and soybean height explained a significant portion of the variance that was observed in the spatial pattern of the collembolan community. Furthermore, the null model revealed more co-occurrence than expected by chance, suggesting that collembolan communities had a non-random co-occurrence pattern in both August and October. Additionally, environmental niche overlap and the body size ratio of co-occurrence showed that interspecific competition was not influential in collembolan community structuring. Considering all of the results together, the contributions of spatial and environmental processes were stronger than biotic interactions in the small-scale structuring of a soil collembolan community.

Co-occurrence Patterns of Above-ground and Below-ground Mite Communities in Farmland of Sanjiang Plain, Northeast China

One of the fundamental questions in community ecology is whether communities are random or formed by deterministic mechanisms. Although many efforts have been made to verify non-randomness in community structure, little is known with regard to co-occurrence patterns in above-ground and below-ground communities. In this paper, we used a null model to test non-randomness in the structure of the above-ground and below-ground mite communities in farmland of the Sanjiang Plain, Northeast China. Then, we used four tests for non-randomness to recognize species pairs that would be demonstrated as significantly aggregated or segregated co-occurrences of the above-ground and below-ground mite communities. The pattern of the above-ground mite commu- nity was significantly non-random in October, suggesting species segregation and hence interspecific competition. Additionally, species co-occurrence patterns did not differ from randomness in the above-ground mite community in August or in below-ground mite com- munities in August and October. Only one significant species pair was detected in the above-ground mite community in August, while no significant species pairs were recognized in the above-ground mite community in October or in the below-ground mite communities in August and October. The results indicate that non-randomness and significant species pairs may not be the general rule in the above-ground and below-ground mite communities in farmland of the Sanjiang Plain at the fine scale.

Responses of Soil Fauna Structure and Leaf Litter Decomposition to Effective Microorganism Treatments in Da Hinggan Mountains,China

Microorganisms are nutritious resources for various soil fauna.Although soil fauna grazing affects microorganism composition and decomposition rate,the responses of soil fauna and leaf litter decomposition to added microorganism is little understood.In this study,in the coniferous and broad-leaved mixed forest of Tahe County in the northern Da Hinggan Mountains,China,three sampling sites(each has an area of 10 m2) were selected.The first two sites were sprinkled with 250 times(EM1) and 1000 times(EM2) diluted effective microorganism(EM) preparations evenly,and the third site was sprinkled with the same volume of water as a control site.The responses of soil fauna structure and leaf litter decomposition to EM treatment were conducted during three years.The results revealed that EM treatment resulted in significant increase of soil organic matter.The number of soil fauna in the EM1 and EM2 sites increased by 12.88% and 2.23% compared to the control site,and among them springtails and mites showed the highest increase.However,the groups of soil fauna in the EM1 and EM2 sites decreased by 6 and 9,respectively.And the changes in the diversity and evenness index were relatively complicated.EM treatment slowed the decomposition of broad-leaved litter,but accelerated the decomposition of coniferous litter.However,the decomposition rate of broad-leaved litter was still higher than that of coniferous litter.The results of this study suggested that the added microorganisms could help individual growth of soil fauna,and this method led to a change in the process of leaf litter decomposition.This paper did not analyze the activity of soil microorganisms,thus it is difficult to clearly explain the complex relationships among litter type,soil fauna and soil microorganisms.Further research on this subject is needed.

Establishment of a diatom-total phosphorus transfer function for lakes on the Songnen Plain in northeast China

To understand the relationship between planktonic diatoms and environmental variables in the lakes on the Songnen Plain,northeast(NE)China,we investigated water quality and planktonic diatoms from 71 sampling points in 27 lakes,based on which Canonical Correspondence Analysis(CCA)was conducted.The result show that planktonic diatoms displayed certain responses to environment gradients,and the total phosphorus(TP)explained the maximum variation of planktonic diatom species among the 15 environmental variables,suggesting that TP was the most important and significant environmental parameter affecting the distribution of diatom species.In addition,we established a diatom-total phosphorus transfer(DTPT)function,of which component 5 of the weighted averaging partial least squares regression(WAPLS)was chosen to and compared with a series of weighted average regression(WA)models and WA-PLS models.According to the jackknifing statistical test,the component 5 of WA-PLS models provided a lower root-mean-square error prediction(RMSEP=0.202)and a higher correlation coefficient between observation and prediction(R^2_Jack=0.759).After deletion of three outliers,the root-mean-square error prediction of the DTPT function was reduced(RMSEP=0.169)while the correlation coefficient between observation and prediction was increased(R^2_Jack=0.823).Therefore,this DTPT function performed better than other regional TP models in the world.However,it remains demanding for expanding the background dataset to improve the prediction ability of the model.

Characterizing the changing environment of cropland in the Songnen Plain, Northeast China, from 1990 to 2015

Quantitative characterization of environmental characteristics of cropland(ECC)plays an important role in maintaining sustainable development of agricultural systems and ensuring regional food security. In this study, the changes in ECC over the Songnen Plain, a major grain crops production region in Northeast China, were investigated for the period 1990–2015. The results revealed significant changes in climate conditions, soil physical properties and cropland use patterns with socioeconomic activities. Trends in climate parameters showed increasing temperature(+0.49°C/decade, p < 0.05) and decreasing wind speed(–0.3 m/s/decade, p < 0.01) for the growing season, while sunshine hours and precipitation exhibited non-significant trends. Four topsoil parameters including soil organic carbon(SOC), clay, bulk density and pH, indicated deteriorating soil conditions across most of the croplands, although some do exhibited slight improvement. The changing amplitude for each of the four above parameters ranged within –0.052 to 0.029 kg C/kg, –0.38 to 0.30,–0.60 to 0.39 g/cm^3, –3.29 to 2.34, respectively. Crop production significantly increased(44.0 million tons) with increasing sown area of croplands(～2.5 million ha) and fertilizer application(～2.5 million tons). The study reveals the dynamics of ECC in the Songnen Plain with intensive cultivation from 1990 to 2015. Population growth, economic development, and policy reform are shown to strongly influence the spatiotemporal changes in cropland characteristics.The study potentially provides valuable scientific information to support sustainable agroecosystem management in the context of global climate change and national socioeconomic development.

The basic characteristics and spatial patterns of global cultivated land change since the 1980s

In this paper, we analyzed the spatial patterns of cultivated land change between 1982 and 2011 using global vector-based land use/land cover data. （1） Our analysis showed that the total global cultivated land area increased by 528.768×10^4 km^2 with a rate of 7.920×10^4 km^2/a, although this increasing trend was not significant. The global cultivated land increased fastest in the 1980s. Since the 1980s, the cultivated land area in North America, South America and Oceania increased by 170.854×10^4 km^2, 107.890×10^4 km^2, and 186.492×10^4 km^2, respectively. In contrast, that in Asia, Europe and Africa decreased by 23.769×10^4 km^2, 4.035×10^4 km^2 and 86.76×10^4 km^2, respectively. Furthermore, the cultivated land area in North America, South America and Oceania exhibited significant increasing trends of 7.236× 10^4 km^2/a, 2.780×10^4 km^2/a and 3.758×10^4 km^2/a, respectively. On the other hand, that of Asia, Europe and Africa exhibited decreasing trend rates of–5.641×10^4 km^2/a,–0.831×10^4 km^2/a and–0.595×10^4 km^2/a, respectively. Moreover, the decreasing trend in Asia was significant. （2） Since the 1980s, the increase in global cultivated lands was mainly due to converted grasslands and woodlands, which accounted for 53.536% and 26.148% of the total increase, respectively. The increase was found in southern and central Africa, eastern and northern Australia, southeastern South America, central US and Alaska, central Canada, western Russia, northern Finland and northern Mongolia. Among them, Botswana in southern Africa experienced an 80%–90% increase, making it the country with the highest increase worldwide. （3） Since the 1980s, the total area of cultivated lands converted to other types of land was 1071.946×10^4 km^2. The reduction was mainly converted to grasslands and woodlands, which accounted for 57.482% and 36.000%, respectively. The reduction occurred mainly in southern Sudan in central Africa, southern and central US, southern Russia, and southern European countries including Bulgaria, Romania, Serbia and Hungary. The greatest reduction occurred in southern Africa with a 60% reduction. （4） The cultivated lands in all the continents analyzed exhibited a trend of expansion to high latitudes. Additionally, most countries displayed an expansion of newly increased cultivated lands and the reduction of the original cultivated lands.

Spatially precise reconstruction of cropland areas in Heilongjiang Province, northeast China during 1900-1910

It is necessary to reconstruct past changes in land use and land cover to under- stand the historical effects of humans on climate and the local environment. We collected information from historical documents on the cropland area at the county level for Heilongji- ang Province, northeast China during 1900-1910. The original records from different histori- cal documents were calibrated with each other. We then defined an agricultural suitability index quantified by the distance from settlements, the slope and complexity of the topography, and the distance from rivers. Following the order of the agricultural suitability index from high to low values, the documented areas of cropland at the county level were then allocated into 1 km x 1 km cells. The area of cropland in 2009 was then retrieved from Landsat ETM＋ images and compared with the areas of cropland during 1900-1910 to determine the human-induced changes in land use and land cover. In this period, the total area of cropland was about 25,397 km2 and this mainly occurred in the mid-southern part of Heilongjiang, in particular the six counties of Hailun, Bayan, Wuchang, Hulan, Shuangcheng and Wangkui. In 2009, the total area of cropland had increased to about 163,808 km2 and had spread over the south- western part to the central and northeastern parts of Heilongjiang. The area of cropland had therefore increased by about 138,411 km2 during the 20th century. The proportion of land used as cropland increased from about 5.6% during 1900-1910 to about 36.2% in 2009, indicating that about 30.6% of the natural land surface in Heilongjiang was replaced by cropland. A total of about 44% （60,962 km2） of the cropland was converted from forest, mainly on the western edge and in the northeastern part of the present-day agricultural area. These areas of cropland reconstructed from historical records for the period 1900-1910 could be used as a basic data set to study the effects of agricultural development on climate and the local environment.

Reconstruction of cropland spatial patterns and its spatiotemporal changes over the 20th century on the Songnen Plain, Northeast China

We initially estimated the cropland area at county level using local historical documents for the Songnen Plain （SNP） in the 1910s and 1930s. We then allocated this cropland area to grid cells with a size of 1 km ×1 km, using a range of cultivation possibilities from high to low; this was based on topography and minimum distances to rivers, settlements, and traffic lines. Cropland areas for the 1950s were obtained from the Land Use Map of Northeast China, and map vectorization was performed with ArcGIS technology. Cropland areas for the 1970s, 1980s, 1990s, 2000s, and 2010s were retrieved from Landsat images. We found that the cropland areas were 4.92 ×10^4 km^2 and 7.60 ×10^4 km^2, accounting for 22.8% and 35.2% of the total area of the SNP in the 1910s and 1930s, respectively, which increased to 13.14 × 10^4 km^2, accounting for 60.9% in the 2010s. The cropland increased at a rate of 1.18 ×10^4 km^2 per decade from the 1910s to 1970s while it was merely 0.285 ×10^4 km^2 per decade from the 1970s to 2010s. From the 1910s to 1930s, new cultivation mainly occurred in the central SNP while, from the 1930s to 1970s, it was mainly over the western and northern parts. This spatially explicit reconstruction could be offered as primary data for studying the effects of changes in human-induced land cover based on climate change over the last century.

Effect of farmland expansion on drought over the past century in Songnen Plain,Northeast China

The effects of human activities on climate change are a significant area of research in the field of global environmental change.Land use and land cover change(LUCC)has a greater effect on climate than greenhouse gases,and the effect of farmland expansion on regional drought is particularly important.From the 1910s to the 2010s,cultivated land in Songnen Plain increased by 2.67 times,the area of cultivated land increased from 4.92×10^4 km^2 to 13.14×10^4 km^2,and its percentage of all land increased from 25%to 70%.This provides an opportunity to study the effects of the conversion of natural grassland to farmland on climate.In this study,the drought indices in Songnen Plain were evaluated from the 1910s to the 2010s,and the effect of farmland expansion on drought was investigated using statistical methods and the Weather Research and Forecasting Model based on UK’s Climatic Research Unit data.The resulting dryness index,Palmer drought severity index,and standardized precipitation index values indicated a significant drying trend in the study area from 1981 to 2010.This trend can be attributed to increases in maximum temperature and diurnal temperature range,which increased the degree of drought.Based on statistical analysis and simulation,the maximum temperature,diurnal temperature range,and sensible heat flux increased during the growing season in Songnen Plain over the past 100 years,while the minimum temperature and latent heat flux decreased.The findings indicate that farmland expansion caused a drying trend in Songnen Plain during the study period.

Applicability evaluation of the SWIM at river basins of the black soil region in Northeast China： A case study of the upper and middle Wuyuer River basin

In this paper, we selected the middle and upper reaches of the Wuyuer River basin in the black soil region of Northeast China as the study area. We adopted the soil and water integrated model （SWIM） and evaluated the parameter sensitivity using partial correlation coefficient. We calibrated and validated our simulation results based on the daily runoff data from Yi＇an hydrological station at the outlet of the river basin and the evaporation data re- corded by various weather stations from 1961 to 1997. Following evaluation of the modeling data against the observed data, we present the applicability of SWIM in the river basin of the black soil region, and discuss the resulting errors and their probable causes. Results show that in the periods of calibration and validation, the Nash-Sutcliffe efficiency （NSE） coeffi- cients of the monthly and daily runoffs were not less than 0.71 and 0.55, and the relative er- rors were less than 6.0%. Compared to daily runoffs, the simulation result of monthly runoffs was better. Additionally, the NSE coefficients of the potential monthly evaporation were not less than 0.81. Together, the results suggest that the calibrated SWIM can be utilized in various simulation analyses of runoffs on a monthly scale in the black soil region of Northeast China. On the contrary, the model had some limitations in simulating runoffs from snowmelt and frozen soil. Meanwhile, the stimulation data deviated from the measured data largely when applied to the years with spring and summer floods. The simulated annual runoffs were considerably higher than the measured data in the years with abrupt increases in annual precipitation. However, the model is capable of reproducing the changes in runoffs during flood seasons. In summary, this model can provide fundamental hydrological information for comprehensive management of the Wuyuer River basin water environment, and its applica- tion can be potentially extended to other river basins in the black soil region.

Accuracy assessment of approaches to spatially explicit reconstruction of historical cropland in Songnen Plain,Northeast China

To understand historical human-induced land use/cover change （LUCC） and its climatic effects, it is essential to reconstruct historical land use/cover changes with explicit spatial information. In this study, based on the historically documented cropland area at county level, we reconstructed the spatially explicit cropland distribution at a cell size of 1 km × 1 km for the Songnen Plain in the late Qing Dynasty （1908 AD）. The reconstructions were carried out using two methods. One method （hereafter, referred to as method 1） allocated the cropland to cells ordered from a high agricultural suitability index （ASI） to a low ASI, but they were all within the domain of potential cropland area. The potential cropland area was created by excluding natural woodland, swamp, water bodies, and mountains from the study area. The other method （hereafter, method II） allocated the cropland to cells in the order from high ASI to low ASI within the domain of cropland area in 1959. This method was based on the hypothesis that the cropland area domain in 1959 resulted from enlargement of the cropland area domain in 1908. We then compared these two reconstructions. We found that the crop- land distributions reconstructed by the two methods exhibit a similar spatial distribution pat- tern. Both reconstructions show that the cropland was mostly found in the southern and eastern parts of the Songnen Plain. The two reconstructions matched each other for about 68% of the total cropland area. By spatially comparing the unmatched cropland cells of the two reconstructions with the settlements for each county, we found that unmatched cropland cells from method I are closer to settlements than those from method I1. This finding suggests that reconstruction using method I may have less bias than reconstruction with method I1.

Preparation and characterization of Pd/Fe bimetallic nanoparticles immobilized on Al_2O_3/PVDF membrane:Parameter optimization and dechlorination of dichloroacetic acid

Using a liquid-solid phase inversion method, a hybrid matrix poly（vinylidene fluoride）（PVDF） membrane was prepared with alumina（Al2O3） nanoparticle addition. Pd/Fe nanoparticles（NPs） were successfully immobilized on the Al2O3/PVDF membrane, which was characterized by Scanning Electron Microscopy（SEM） and Transmission Electron Microscopy（TEM）. The micrographs showed that the Pd/Fe NPs were dispersed homogeneously. Several important experimental parameters were optimized, including the mechanical properties, contact angle and surface area of Al2O3/PVDF composite membranes with different Al2O3 contents. At the same time, the ferrous ion concentration and the effect of hydrophilization were studied. The results showed that the modified Al2O3/PVDF membrane functioned well as a support. The Al2O3/PVDF membrane with immobilized Pd/Fe NPs exhibited high efficiency in terms of dichloroacetic acid（DCAA） dechlorination. Additionally, a reaction pathway for DCAA dechlorination by Pd/Fe NPs immobilized on the Al2O3/PVDF membrane system was proposed.

Air transportation in China: Temporal and spatial evolution and development forecasts

This paper analyses the features and dynamic changes of the spatial layout of air transportation utilization among different provinces in China. It makes use of data for the airport throughput and socio-economic development of every province throughout the country in the years 2006 and 2015, and employs airport passenger and cargo throughput per capita and per unit of GDP as measures of regional air transportation utilization, which is significant for refining indicators of regional air transportation scale and comparing against them. It also analyzes the spatial differences of coupling between the regional air transportation utilization indicators and the key influencing factors on regional air transportation demand and utilization, which include per capita GDP, urbanization rate, and population density. Based on these key influencing factors, it establishes a multiple linear regression model to conduct forecasting of each province＇s future airport passenger and cargo throughput as well as throughput growth rates. The findings of the study are as follows：（1） Between 2006 and 2015, every province throughout the country showed a trend of year on year growth in their airport passenger and cargo throughput per capita. Throughput per capita grew fastest in Hebei, with a rise of 780%, and slowest in Beijing, with a rise of 38%. Throughput per capita was relatively high in western and southeastern coastal regions, and relatively low in northern and central regions. Airport passenger and cargo throughput per unit of GDP showed growth in provinces with relatively slow economic development, and showed negative growth in provinces with relatively rapid economic development. Throughput per unit of GDP grew fastest in Hebei, rising 265% between 2006 and 2015, and Hunan had the fastest negative growth, with a fall of 44% in the same period. Southwestern regions had relatively high throughput per unit of GDP, while in central, northern, and northeastern regions it was relatively low.（2） Strong correlation exists between airport passenger and cargo throughput per capita and per capita GDP, urbanization rate, and population density. Throughput per capita has positive correlation with per capita GDP and urbanization rate in all regions, and positive correlation with population density in most regions. Meanwhile, there is weak correlation between airport passenger and cargo throughput per unit of GDP and per capita GDP, urbanization rate, and population density, with positive correlation in some regions and negative correlation in others.（3） Between 2015 and 2025, it is estimated that all provinces experience a trend of rapid growth in their airport passenger and cargo throughput. Inner Mongolia and Hebei will see the fastest growth, rising221% and 155%, respectively, while Yunnan, Sichuan, and Hubei will see the slowest growth, with increases of 62%, 63%, and 65%, respectively.

Source - Area Weathering and Recycled Sediment for Dumeng Sandy Land Inferred from Geochemistry Compositions: Implication for Contribution to Aeolian Dust

In this study, twenty seven sets of the μ63 /nm fine — grained subsamples from fluvial sand, floodplain muddy silt, sandy paleosoil and aeolian sand, respectively, in Dumeng Sandy Land, were collected and analyzed for major, trace elements and REE as well as Sr —Nd isotopic compositions to evaluate their source — area chemical weathering and sediment recycling, and to infer their contribution to aeolian dust.