Soil Organic Carbon Stock Variation under Different Soil Types and Land Uses in the Sub-Humid Noun Plain, Western Cameroon

This study was conducted to assess the current stock of soil organic carbon under different agricultural land uses, soil types and soil depths in the Noun plain in western Cameroon. Three sites were selected for the study, namely Mangoum, Makeka and Fossang, representative of the three dominant soil types of the noun plain (Andosols, Acrisols and Ferralsols). Three land uses were selected per site including natural vegetation, agroforest and crop field. Soil was sampled at three depths;0 - 20 cm, 20 - 40 cm, and 40 - 60 cm. Analysis of variance showed that soil type did not significantly influence carbon storage, but rather land uses and soil depth. SOCS decreased significantly with depth in all the sites, with an average stock of 66.3 ± 15.8 tC/ha at 0 - 20 cm, compared to an average stock of 33.3 ± 7.4 tC/ha at 40 - 60 cm. SOCS was significantly highest in the natural formation with 57.2 ± 19.7 tC/ha, and lowest in cultivated fields, at 37.7 ± 10.6 tC/ha. Andosols, with their high content of coarse fragments, stored less organic carbon than Ferralsols and Acrisols.

Impacts of climate change mitigation on agriculture water use:A provincial analysis in China

Agriculture consumes huge amounts of water in China and is profoundly affected by climate change.This study projects the agricultural water use towards 2030 under the climate change mitigation target at the provincial level in China by linking a computable general equilibrium(CGE)model and a regression model.By solving the endogeneities amongst agricultural water use,output and climate factors,we explore how these variables affect water use and further predict future trends through soft-link with the IMED|CGE model.It is found that sunshine duration has a slightly positive impact on water use.Furthermore,agricultural output will significantly drive agricultural water use based on historical data of the past 16 years.Results also show that carbon reduction would have a trade-offor co-benefit effect on water use due to regional disparity.Provinces with increasing agricultural exports,such as Xinjiang and Ningxia,would anticipate considerable growth in agricultural water use induced by carbon reduction.The soft-link method proposed by this study could be applied for future studies that aim to incorporate natural and geographical factors into human activities,and vice versa,for assessing sustainable development policies in an integrated way.

Regional disparity in the changes of agricultural land use intensity in China during 1980-2002

Based on the cost-benefit data （1980-2002） of farm products and China Agriculture Yearbooks, this paper studies the regional disparity in the changes of the agricultural land use in China during the period 1980-2002 from three aspects such as the degree of intensity, the sown area and the abandoned farmland. The results show that： （1） The degree of intensity of land use in the westena region during 1980-2000 has a strong uptrend, but in the eastern and central regions the degree of intensity descends obviously and has shown a continuous downtrend since 1997. （2） The total sown area shrinks notably in the eastern region, while it enlarges constantly in the western region. （3） The sown area in the eastern, central and western regions has gone through a similar cyclic process： down （1980-1985）-up （1985-1991）-down （1991-1994）-up （1994-1999）-down （1999-2002）. However, there are obvious differences in amplitude variation and tendency among them. The sown area has shrunk in the eastern region and expanded in the central and western regions especially before 1999. （4） The most cases of abandoned farmland are reported in the central region, the second in the eastern region and the least in the western region. The abandonment phenomena chiefly occurred during 1992-1995 in the eastern region, and during 1998-2002 in the central region.

Countermeasures of Reclaimed Municipal Wastewater for Safety of Agricultural Use in China

China is facing a severe water resource crisis, and the shortage of water for agricultural consumption is a prominent problem. Irrigation with reclaimed municipal wastewater that can reach the agricultural recycling standards is an important way to deal with water shortage in agricultural production. Owing to the complex sources of municipal wastewater, there are multifarious pollutants in municipal wastewater. Improper use of wastewater can cause potential risks to agoenvironment, agricultural products safety, and human health. This article deals with the current situation and the development prospects of reclaimed wastewater for agricultural use in China and abroad; the potential risks to human health and environmental pollution from the reclaimed municipal wastewater for agricultural reuse are also discussed. And some countermeasures and advices of reclaimed municipal wastewater for safety of agricultural reuse are provided.

Function of Agricultural Land Use and Its Evolvement in Peri-urban Area: A Case Study of Beijing

Rapid urbanization in Beijing stimulates the urban land expansion and diminishes available agricultural land. Monofunctional agricultural land use can not meet the demand of the devel- opment of the multifunctional agriculture and urbanization any more, so multifunctional agricultural land use is going to be promoted in the city. This article proposes the evolvement of the land use change from 1992 to 2004 and discusses some evolvement views.

Accumulation and bioavailability of heavy metals in a soil-wheat/maize system with long-term sewage sludge amendments

A long-term field experiment was carried out with a wheat-maize rotation system to investigate the accumulation and bioavailability of heavy metals in a calcareous soil at different rates of sewage sludge amendment. There are significant linear correlations between the contents of Hg, Zn, Cu, Pb, and Cd in soil and sewage sludge amendment rates. By increasing 1 ton of applied sludge per hectare per year in soil, the contents of Hg, Zn, Cu, Pb, and Cd in soil increased by 6.20, 619, 92.9, 49.2, and 0.500 μg kg–1, respectively. For Hg, sewage sludge could be safely applied to the soil for 18 years at an application rate of 7.5 t ha–1 before content exceeded the soil environmental quality standards in China(1 mg kg–1). The safe application period for Zn is 51 years and is even longer for other heavy metals(112 years for Cu, 224 years for Cd, and 902 years for Pb) at an application rate of 7.5 t ha–1 sewage sludge. The contents of Zn and Ni in wheat grains and Zn, Cu, and Cr in maize grains increased linearly with increasing sewage sludge amendment rates. The contents of Zn, Cr, and Ni in wheat straws and Zn, Cu, and As in maize straws were positively correlated with sewage sludge amendment rates, while the content of Cu in wheat straws and Cr in maize straws showed the opposite trend. The bioconcentration factors of the heavy metals in wheat and maize grains were found to be in the order of Zn>Cu>Cd>Hg>Cr=Ni>Pb>As. Furthermore, the bioconcentration factors of heavy metals in wheat were greater than those in maize, indicating that wheat is more sensitive than maize as an indicator plant. These results will be helpful in developing the critical loads for sewage sludge amendment in calcareous soils.

Monitoring the Heavy Element of Cr in Agricultural Soils Using a Mobile Laser-Induced Breakdown Spectroscopy System with Support Vector Machine

Due to its complicated matrix effects, rapid quantitative analysis of chromium in agricultural soils is difficult without the concentration gradient samples by laser-induced breakdown spectroscopy. To improve the analysis speed and accuracy, two calibration models are built with the support vector machine method： one considering the whole spectra and the other based on the segmental spectra input. Considering the results of the multiple linear regression analysis, three segmental spectra are chosen as the input variables of the support vector regression （SVR） model. Compared with the results of the SVR model with the whole spectra input, the relative standard error of prediction is reduced from 3.18% to 2.61% and the running time is saved due to the decrease in the number of input variables, showing the robustness in rapid soil analysis without the concentration gradient samples.

Research and Development of Rare Earth Advanced Materials in China

China is rich in resources of rare earths(REs). Based on tremendous work, China has made great achievements in research and development of REs since 1980s, and the production of RE has won the leading position in the world. The application of RE elements in advanced materials have progressed significantly during the past years. The wide range of rare earth application in China has been reviewed and discussed in this paper, including the development of advanced RE materials (RE-Al alloys, rare earth nonferrous metal alloys, rare earth luminescent materials, rare earth hydrogen storage materials, rare earth permanent magnet and rare earth compounds used in agriculture, i.e., rare earth micronutrient fertilizer etc.) End the research of new RE materials (high T-c rare earth superconductor, rare earth electronic and photonic materials, rare earth ceramics and rare earth precious metal alloys). Finally, the further development works to be required are as follow: (1) to enhance the applied fundamental research, study the intrinsic properties of rare earth elements and develop less well known uses; (2) to undertake the applied research of median and heavy rare earth and find a way out of the unbalance of RE resources in the various applications; (3) to strengthen the applied research of RE element's in energy field, solving the energy-related, energy-saved and environmental problems.

Biomonitoring of endosulfan toxicity in human

Chemicals are comprehensively used worldwide to control herbs,weeds,pests,and other competing agents with various growing crops.The consumption of crops grown with these chemicals(even in small quantities)can upshot into accumulation in the human body.People can accidentally inhale these hazardous chemicals if they are in an area where they were applied.These chemicals can be ingested in a human with contaminated food and drinks.Ultimately it causes various adverse effects(chronic toxicity,teratogenic,mutagenic,carcinogenic effect,reproductive,and organ toxicity)on human health.Among the pool of these chemicals used as pesticides in the environment,exposure of endosulfan to humans has a potential health risk throughout the globe.The poisoning of endosulfan is reported frequently in society,therefore,this article highlights the toxicological and other harmful properties of endosulfan to humans and emphasized its essential biomonitoring.Its quick monitoring and effective hazard evaluation are possible with multiomics technologies and some other analytical approaches.This review summarizes the introduction and mechanism of action of endosulfan along with some other toxic chemicals used in the agriculture work,the toxicity of endosulfan in human/environment,and importantly its biomonitoring(detection of chemicals and their metabolites in a biological sample)in human because biomonitoring is often considered as the most preferred method.Biomonitoring could be easily done in human samples(blood,hair,milk,and urine)with a multi-omics approach,which is a quick,reliable,and state-of-the-art technique.

Spatio-Temporal Patterns of Nitrogen and Phosphorus Stoichiometry in Cascade Ponds in an Agricultural Small Watershed and Their Influencing Factors

Ecological stoichiometry of nitrogen and phosphorus is an important indicator to characterize the nitrogen and phosphorus trophic status in aquatic ecosystems. The study of the spatio-temporal patterns of nitrogen and phosphorus stoichiometry is beneficial to the nitrogen and phosphorus pollution management in pond ecosystems. In this study, 18 groups (36 in total) of typical cascade ponds were selected as long-term observations to investigate the spatial distribution patterns of nitrogen and phosphorus component ratios (ratio of total nitrogen to phosphorus: TN:TP, ratio of dissolved nitrogen to phosphorus: TDN:TDP, ratio of particulate nitrogen to phosphorus: PN:PP) in water bodies in the tropical agricultural watershed of Jinjing. The results showed that the average values of TN:TP and TDN:TDP in the upstream ponds were 26.4 and 53.4, respectively, and were more than those in the downstream (22.95 and 48.1, respectively). In contrast, the PN:PP (13.78) in the upstream was significantly lower than that of the downstream (30.39). Furthermore, the factors of rainfall, agricultural land use and fish farming influenced the spatio-temporal variability of the N:P ratios. The ratios of TN:TP and TDN:TDP were higher in the wet season and lower in the dry season. Agricultural land use and fish farming reduced the ratios of the above three nitrogen and phosphorus components in cascade ponds in the study area. Our results show that strengthening agricultural land pollution control and aquaculture management could help to improve water quality of pond ecosystems in the study area.

Agricultural Land Use Effects on Climate over China as Simulated by a Regional Climate Model

The Abdus Salam International Centre for Theoretical Physics（ICTP） Regional Climate Model version 3（RegCM3） is used to investigate the climate effects of land use change related to agriculture over China.The model is driven by the European Center for Medium-range Weather Forecast 40-yr Re-Analysis（ERA40） data.Two sets of experiments for 15 yr（1987-2001） are conducted,one with the potential vegetation cover and the other the agricultural land use（AG）.The results show that the AG effects on temperature are weak over northern China while in southern China a significant cooling is found in both winter（DecemberJanuary-February） and summer（June-July-August）.The mean cooling in the sub-regions of South China（SC） in winter and the sub-regions of Southeast（SE） China in summer are found to be the greatest,up to 0.5°and 0.8 ℃ ,respectively.In general,the change of AG leads to a decrease of annual mean temperature by 0.5-1 ℃ in southern China.Slight change of precipitation in western China and a decrease of precipitation in eastern China are simulated in winter,with the maximum reduction reaching-7.5% over SE.A general decrease of precipitation over northern China and an increase over southern China are simulated in summer,in particular over SE where the increase of precipitation can be up to 7.3%.The AG effects on temperature and precipitation show strong interannual variability.Comparison of the climate effects between AG and the present-day land use（LU） is also performed.In southern China,the ratio of temperature（precipitation） changes caused by AG and LU is greater than（closer to） the ratio of the number of grid cells with changed vegetation cover due to AG and LU variations.

Agricultural land use intensity study in Taibus Banner, and its determinants： a case Inner Mongolia, China

Based on rural household survey data from Taibus Banner, in the Inner Mongolia Autonomous Region, China, this study separately categorizes agricul- tural land use intensity into labor intensity, capital intensity, the intensity of labor-saving inputs, and the intensity of yield-increasing inputs, and then analyzes their determinants at the household level. The findings reveal that within the study area： （1） labor intensity is higher and capital intensity is lower than in the major grain-producing and economically developed areas of eastern and central China; （2） the most widely planted crops are those with the lowest labor intensity （oats） and capital intensity （benne）; （3） there are marked differences in agricultural land use intensity among households; a major factor affecting land use decision-making is the reduced need for labor intensity for those households with high opportunity costs, such as those with income earned from non-farming activities which alleviates financial constraints and allows for increased capital intensity. As a result, these households invest more in labor-saving inputs; （4） households with a larger number of workers will allocate adequate time to manage their land and thus they will not necessarily invest more in labor-saving inputs. Those households with more land to manage tend to adopt an extensive cultivation strategy. Total income has a positive impact on capital intensity and a negative impact on labor intensity. House- holds that derive a higher proportion of their total income through farming are more reliant upon agriculture, which necessitates significant labor and yield-increasing inputs. Finally, the authors contend that policy makers should clearly recognize the impacts of non-farming employment on agricultural land use intensity. In order to ensure long- term food security and sustainable agricultural develop-ment in China, income streams from both farming and non- farming employment should be balanced.

Water use efficiency data from 2000 to 2019 in measuring progress towards SDGs in Central Asia

Central Asia,located in the hinterland of the Eurasian continent,is characterized with sparse rainfall,frequent droughts and low water use efficiency.Limited water resources have become a key factor restricting the sustainable development of this region.Accurately assessing the efficiency of water resources utilization is the first step to achieve the UN Sustainable Development Goals(SDGs)in Central Asia.However,since the collapse of the Soviet Union,the evalua-tion of water use efficiency is difficult due to low data availability and poor consistency.To fill this gap,this paper developed a Water Use Efficiency dataset(WUE)based on the Moderate Resolution Imaging Spectroradiometer(MODIS)Gross Primary Production(GPP)data and the MODIS evapotranspiration(ET)data.The WUE dataset ranges from 2000 to 2019 with a spatial resolution of 500 m.The agricultural WUE was then extracted based on the Global map of irrigated areas and MODIS land use map.As a complementary,the water use amount per GDP was estimated for each country.The present dataset could reflect changes in water use efficiency of agriculture and other sectors.

Geographic concentration and driving forces of agricultural land use in China

Since the 1990s, China has entered the middle phase of urbanization which leads to the existence of significant geographic concentration of agricultural land use. The average value of regional concentration degree of ten representative crops in China was 59.03%, showing a high degree of geographic concentration in farming. Some typical agriculture provinces in farming have arisen. The degree of geographic concentration in farming has been enhanced, with the average degree of regional concentra- tion often crops increasing considerably by 3.83% in 2009 compared to that in 1990 （55.20%）. The spatial growing center of farming was found to move westward and northward during 1990-2009. Meanwhile food production concentrated in the Northeast China and main producing area, and cash crops production concentrated in Northwest China. Off-farm employment of rural labor force, commercialization of agricultural product and regional comparative advantage are the main driving forces of geographic concentration of agricultural land use. Govern- mental policies with regional differences should be considered to promote further development of agriculture.

面向黄土高原耕地高效利用的两季种植模式可行性分析

Cropping systems worldwide have been affected by the current trend in global warming and the optimization of cropping systems is an important area of research in the transition of agricultural land. The Loess Plateau is a typical ecologically fragile region with the most serious soil erosion in China. We carried out a field experiment in Yan’an city on the Loess Plateau to explore the effect of sowing date on crop growth and yield. We then analyzed the feasibility of a double-cropping system by considering climatic adaptability, ecological suitability and economic viability. Our results showed that different sowing dates resulted in significant differences in crop growth and that appropriate early sowing can result in higher crop yields for early maturing varieties. We showed that double-cropping systems of sweet maize(Zea mays)–forage rape and feed maize–forage rape are feasible on the Loess Plateau. We discuss the implications for the efficient use of farmland, which is important in guiding agricultural supply-side reform and the development of modern agricultural management.

Relative importance of biological and human-associated factors for alien plant invasions in Hokkaido, Japan

Aims The invasion success of alien plants is strongly affected by both biological and human-associated factors.Evaluation of the rela-tive contribution of each factor is important not only for the further understanding of invasion processes but also for the better manage-ment of invasion risk,particularly in protected areas of high con-servation priority.Here,we quantified the relative importance of species biological traits and association with a human activity,i.e.agriculture,in explaining the invasion success of alien plants across the entire region and in protected areas in Hokkaido,Japan.Methods As a quantitative measure of invasion success,the distribution ex-tent of naturalized populations across the entire prefecture and in protected areas was calculated for 63 alien species with equal residence time based on species occurrence records at a spatial resolution of 5-km mesh grid units.For each species,we identi-fied seven biological traits(seed mass,dispersal mode,maximum plant height,capability of vegetative reproduction,flowering start time and period and life span)and two human-associated factors(introduction purpose and cultivation frequency for agricultural use).Cultivation frequency was determined based on the frequency of seed-sowing in pastures:(1)not sown,(2)accidentally sown as a seed contaminant and(3)intentionally sown for commercial cul-tivation.The importance of biological traits and human-associated factors in explaining the distribution extent was determined using an information-theoretic approach.Important Findings In explaining the distribution extent across the entire prefecture,species biological traits and human-associated factors showed comparable importance;cultivation frequency exhibited the high-est importance value closely followed by seed mass,maximum height and flowering period.In contrast,when focusing on pro-tected areas,human association was more important than bio-logical traits,as indicated by the greatest importance of cultivation frequency and much lower values for most biological traits.The results demonstrated that species biological traits and human as-sociation almost equally contributed to invasion success across the entire region,while invasions into protected areas were more attributable to human association than to biological traits.We highlight that the control of propagule pressure associated with artificial cultivation may be key to preventing further invasions into protected areas.

1Chinese human geography and its contributions

The aim of this paper is to sift through examples of outstanding contributions made by Chinese human geography in terms of social applications and explain the basic concepts and theoretical methods explored by human geography that are behind the applications of results with major social influence, so as to be able to summarize the main school that represents developments in contemporary Chinese human geography. Chinese human geography upholds the subject＇s designation as being integrated and interdisciplinary. Research focuses on interactions between the natural and human spheres of the Earth＇s surface, and it is guided by the understanding and effects of the processes of regional sustainable development at different spatial scales. Chinese human geography has innovatively established the following development paradigm： ＂To be guided by application requirements, refine key issues of the discipline in the course of solving major issues of human geography in national and regional development, and by solving those key issues, to enhance its ability to provide scientific and technological support to serve national and local needs while promoting its own development.＂ Results from early Chinese human geography studies on land use and agricultural zoning, recent research results on point-axis system models and T-shaped national spatial development patterns, and current research results on territorial function theory and major function oriented zones have all continued and strengthened the mainstream school of Chinese human geography and have avoided the global tendency for human geography to become rapidly human-oriented, while results have been applied at the highest level of decision-making management. Chinese human geography can provide lessons for developing countries and may play a leading role in the future development of global human geography.