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.

Groundwater quality and land use change in a typical karst agricultural region:a case study of Xiaojiang watershed,Yunnan

Taking the typical karst agricultural region, Xiaojiang watershed in Luxi of Yurman Province as a research unit, utilizing the groundwater quality data in 1982 and 2004, the aerial photos in 1982 and TM images in 2004, supported by the GIS, we probe into the law and the reason of its space-time change of the groundwater quality over the past 22 years in the paper. The results show： （1） There were obvious temporal and spatial changes of groundwater quality during the past 22 years. （2） Concentrations of NH4^＋, SO4^2- , NO3, NO2^-, Cl^- and the pH value, total hardness, total alkalinity increased significantly, in which NH4^2-, NO3, and NO2^- of groundwater exceeded the drinking water standards as a result of non-point pollution caused by the expansion of cultivated land and mass use of the fertilizer and pesticide. （3） Oppositely, Ca^2＋ and HCO3^- showed an obvious decline trend due to forest reduction and degradation and stony desertification. Meantime, there was a dynamic relation between the groundwater quality change and the land use change.

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.

Impact of Labor Transfer on Agricultural Land Use Conversion at Rural Household Level Based on Logit Model

Since land and labor force are primary resources to be used and controlled by rural households, the allocation of labor forces will influence land uses, and further lead to land use conversion. The present study used the Binary Logit model to investigate the influence of labor force transfer, characteristics of rural households, location, and land market on agricultural land use conversion at rural household level. This study was conducted based on 329 valid questionnaires, which were obtained in Changshu, Rudong, and Tongshan counties, respectively representing the southern, middle and northern areas of Jiangsu Province. The results showed that land market participation, location, zonal difference and labor transfer had strong influences on agricultural land use conversion. The participation of land market had a strong positive effect on land use conversion, especially for the farmland converted to the fishpond. The nearer to the county seat, the more conversion of land use occurred. Particularly, the labor force transfer caused by wage employment decreased this conversion probability, while the labor transfer caused by self-employment led to more conversion; and the increasing of income from labor transfer increased the conversion. Moreover, land use con- versions demonstrated zonal difference, which were more in Rudong and Changshu counties than in Tongshan County, and the factors influencing this conversion were different in the three regions.

The impact of land use on soil properties in a karst agricultural region of Southwest China: a case study of Xiaojiang watershed, Yunnan

Supported by RS and GIS, the land use change from 1982 to 2003 were analyzed and the impacts of land use changes on pH value, organic matter, total N, total P, total K, available N, available P, and available K in soil of Xiaojiang watershed, a typical karst agricultural region of Yunnan Province, Southwest China were assessed. The following aspects are concluded. （1） The total land use converted during the past 20 years in Xiaojiang watershed covers an area of 610.12 km^2, of which 134.29 km^2 of forestland was converted into cultivated land, and 210 km^2 of.unused land was converted into cultivated land. （2） The rapid growth of population and the economic development were the main driving forces of land use change. （3） With the change in land use, the soil properties have been changed significantly. The pH, organic matter, total N, total P, total K, available N, available P and available K in soil in 1982 were 6.3, 38.02 g·kg^-1, 1.86 g·kg^-1, 1.63 g·kg^-1, 10.94 g·kg^-1, 114.42 g·kg^-1, 11.65 mg·kg^-1 and 64.69 mg·kg^-1g, respectively; and those in 2003 were 6.73, 25.26 g·kg^-1, 1.41 g·kg^-1, 0.99 g·kg^-1, 12.6 g·kg^-1, 113.43 mg·kg^-1, 11.11 mg·kg^-1 and 151.59 mg·kg^-1, respectively. Pared samples t-test of the tested indices of soil properties indicate that those indices have changed significantly during the last 20 years. But the soil properties changed differently, due to the differences in land use change. （4） Also, with the change in land use and management measures of soil, the modifications in soil properties which developed from carbonate rocks were more sensitive than those in the soil developed from sandstone.

The causes and environmental effects of land use conversion during agricultural restructuring in Northeast China

During the last decade of the 20th century, extensive conversion inagricultural land use took place in Northeast China. The goal of this study is to ascertain itsspatial distribution and regional differentiation, determine its causes, and analyze itsenvironmental impact. Especially we attempt to elucidate how institutional constraints havefacilitated the change at a time of agrarian restructuring when newly emerging free market washybridized with the former planned economy. Information on six categories of land use was mappedfrom interpretation of Landsat TM images recorded in 1990, 1995 and 2000. Most of land use changestook place during the first half of the decade, coinciding with abrupt and chaotic changes ingovernment directives. Farmland was changed mainly to woodland, water body and built-up areas whilewoodland and grassland were converted chiefly to farmland. Spatially, the change from farmland towoodland was restricted to the west of the study area. The change from grassland to farmland tookplace in the grazing and farming interlocked west. These chaotic and occasionally conflictingchanges were largely caused by lack of stability and consistency in agricultural land use policiespromulgated. They have exerted adverse impacts on the local environment, including land degradation,increased flooding, and modified climate regime.

Effect of Agricultural Land Use Changes on Soil Nutrient Use Efficiency in an Agricultural Area,Beijing,China

Agricultural land use and management practices may affect soil properties,which play a critical role in sustaining crop production.Since the late 1970s,several new agricultural land use types had been introduced in the rural areas of China.The purpose of this study is to evaluate the effect of these land use changes on the soil properties,nu-trient absorption rate,and nutrient use economic efficiency ratio in an agricultural area of Beijing.Specifically,the cropland,the orchard and the vegetable field were examined.Results of this study suggest that land use and farming management practices significantly affect the content of soil organic carbon (SOC),total nitrogen (TN),total phos-phorus (TP),and available phosphorus in the surface layer of 0-25 cm (p<0.05) in the Yanqing Basin,northwestern Beijing.Soil nutrients in each agricultural land use type decrease rapidly with the increasing soil depth.Orchard and vegetable field tend to have higher soil nutrients than the cropland does.However,the soil nutrient-absorption rate (NAR) of the orchard and vegetable field is lower than that of the cropland,even though orchard and vegetable field may provide much higher economic benefit.While increasing SOC,TN,and TP in the orchard and vegetable field by intensive farming may be a valuable option to improve soil quality,potential increase in the risk of nutrient loss,or agricultural non-point source pollution can be a tradeoff if the intensive practices are not managed appropriately.

Impacts of the Rising Opportunity Cost of Farm Labor on Agricultural Land Use Structure: Theory and Empirical Evidences

Nowadays the rising of opportunity cost of farm labor comes to the forefront of attention in China. In order to understand its impact on agricultural land-use structure, a theoretical framework of household economics is formulated drawn on Low's model. Under the theoretical framework, the impact of the rising opportunity cost of on-farm on cropping structure is deduced in theory. And then, using statistic and survey data, taking mountain area of southern Ningxia as an example, the theoretical assumes are verified. The results show that the rise of opportunity cost of farm labor leads to less diversified cropping structure.

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.

Issues concerning Farmland Transfer in the Development of China's Agricultural Modernization——Based on the Survey of Farmers in 21 Townships of Sichuan Province

Based on the actual survey of 724 rural households in 21 townships of Sichuan Province,this article analyzes the basic information,basic characteristics and problems in current China's farmland transfer.The results show that the rural land contractual management right is relatively stable;in farmland transfer market,the degree of development of farmland transfer-out market is higher than that of farmland transfer-in market;at the same time,there are many problems,such as fragmentation of rural land resources allocation,incomplete land property rights system,too powerful land security function,single land transfer pattern and unsound transfer system.Corresponding countermeasures are put forward as follows:unifying urban and rural planning,and adjusting distribution pattern of rural land in concert with the course of urbanization;improving land property rights system,so that the farmers have the land contractual management right with real right tendency;strengthening the legal construction of land transfer,regulating the land transfer process,and guiding regularized and legalized development of land transfer;promoting farmers' cognitive level,and establishing the intermediary platform to provide land transfer information,ensuring information symmetry between both sides of transfer;providing more non-agricultural jobs,establishing and improving social security system for farmers,and diluting the social security function of land.

An Agent-Based Assessment of Land Use and Ecosystem Changes in Traditional Agricultural Landscape of Portugal

This paper presents an assessment of land use changes and their impacts on the ecosystem in the Montado, a traditional agricultural landscape of Portugal in response to global environmental change. The assessment uses an agent-based model (ABM) of the adaptive decisions of farmers to simulate the influence on future land use patterns of socio-economic attributes such as social relationships and farmer reliance on subsidies and biophysical constraints. The application and development of the ABM are supported empirically using three categories of input data: 1) farmer types based on a cluster analysis of socio-economic attributes;2) agricultural suitability based on regression analysis of historical land use maps and biophysical attributes;and 3) future trends in the economic and climatic environments based on the A1fi scenario of the Intergovernmental Panel on Climate Change. Model sensitivity and uncertainty analyses are carried out prior to the scenario analysis in order to verify the absence of systematic errors in the model structure. The results of the scenario analysis show that the area of Montado declines significantly by 2050, but it remains the dominant land use in the case study area, indicating some resilience to change. An important policy challenge arising from this assessment is how to encourage next generation of innovative farmers to conserve this traditional landscape for social and ecological values.

Land Use Change and Its Effect on Environment Based on Farmers’Behaviors: A Case Study in Agricultural Areas of Tibet, China

In the case study in Agricultural Area of Tibet, the process and characteristics of farmers' land use were surveyed by semi-structural interview questionnaire. By comparing the change of land covers and farmers' land decision in two periods, the spatial connection of them was obtained. And the relations among farmers' land decision, land use change and environment were examined by calculating emergy and value flow. The results show that: hunting the maximal profits is the primary aim of farmers' land decision; farmers' land decision is incompatible with sustainable land use presently; farmers' land decision and land cover can be embodied spatially by each other; the change of farmers' land decision can be monitored by observing the change of land cover, and the sustainability of farmers' land decision can be appraised by calculating emergy and value flow.

Analysis of the Price of Development Right of Agricultural Land in China

According to the viewpoints of predecessors, we define the signification of development right of agricultural land and connotation of the price of development right of agricultural land as follows: the development right of agricultural land is to change the former use nature of agricultural land, so as to become the right of construction use land; the price of development right of agricultural land refers to the price that is difference between the price of construction use land, and summation of the price of former agricultural land, the expense of developing agricultural land, the expense of management, and profit, after the agricultural land is transformed into non-agricultural construction use land. By using the principle of economics of land, this paper expounds the generation mechanism of the price of development right of agricultural land, namely the diversity of agricultural land use and the change of demand and supply of development right of agricultural land. The influencing factors of the development right of agricultural land are analyzed, and there are mainly the price of agricultural land, the price of construction use land, the contradiction of demand and supply of urban land, land use, and agricultural land.

Discussion on Registration Validity Doctrine of Housing Land Use Right

Relationship between the registration and right change of housing land use right is not clearly stipulated in the Property Law. Land registration involves functions of private law and public law. It is partial to only considering private rights dimension when deciding whether registration validity doctrine or registration confrontation doctrine should be implemented in housing land use right. Compilation of land use planning, implementation of land use control and promotion of arrangement project in rural residential area all rely on sound and complete housing land registration data. To clarify housing land right adscription, eliminate hidden troubles causing housing land dispute and promote the establishment of harmonious countryside can never be achieved without housing land registration data. To carry out registration validity doctrine of housing land use right can effectively guide farmers' registration behavior and thus build a perfect registration information system of housing land use right. After the cross-village and even cross-town arrangement in rural residential areas, rural acquaintance society has transformed into semi-acquaintance society and even stranger society. Therefore, housing land use right commending its existence with registration in public form has been a necessary choice in legislation.

Sustainable Use of Agricultural Land in Zhoukou City Based on Emergy Analysis

Taking Zhoukou City in Henan Province as an example,we select the statistics during the period 2000-2009,and use emergy analysis method to research the sustainable use of agricultural land in Zhoukou City. The study results show that: ( i) The agricultural input is mainly based on resources purchase input,which accounts for more than 90% of total emergy input; the industrial energy input is to a large extent dependent on the input of chemical fertilizer and pesticide; precipitation significantly affects the input of renewable environmental resources. ( ii) The agricultural output is mainly based on farming and animal husbandry,with the proportion reaching 99% ; the proportion of fishery and forestry is too low; the agricultural output structure is relatively simple. ( iii) The use of agricultural land has achieved initial success in terms of economic sustainability,but in terms of ecological sustainability and social sustainability,it is at a low level; the sustainable use index shows the great vitality and development potential of agricultural system; unsustainability is reflected in considerable input of chemical fertilizer and pesticide,and simple agricultural output structure.

Study on Circulation and Management of Rural Land Use Right

Currently,agriculture and rural economy have entered a new development stage. According to market demands and comparative advantages of regional resources,strategic adjustment of agricultural structure and realizing transformation from traditional agriculture to modern agriculture have become primary tasks. Land is the essential element of agricultural production,making innovation upon rural land use system and establishing flexible and effective land circulation system concern efficiency and optimization of agricultural resource allocation and development of rural element market. With more and more farmers engaged in secondary and tertiary industries,land left by those farmers is circulated to those farmers willing to do farming. Rural land circulation is inevitable trend of economic and social development,but it is a progressive process. To realize smooth rural land circulation,there must be standardized system.

Impacts of Changes in Structure of Rural Land Property Rights on Agricultural Performance

In the reform process of the rural land property rights system,the incentive mechanism of the rural land property rights system has a crucial impact on the production activities of rural economic entities.Due to the different rights structures of the property rights system in different social and economic development stages,the land rights and interests enjoyed by rural economic subjects are different,and the degree of incentives for farmers is also different.This difference in incentives affects farmers investment in agricultural production factors,which in turn affects agricultural performance.This paper analyzes the incentive impacts of the structure of rural land property rights on the changes of farmers land rights and agricultural performance since the founding of the People s Republic of China,in order to further deepen the reform of the land system,protect the rights and interests of farmers,promote the modernization of agriculture and rural areas,and explore the realization form and operation mechanism of the rural collective land system in the new era.

Reform Paths of Rural Land Property Rights System in the Context of Agricultural Modernization

The reform of rural land property rights system can promote large-scale and intensive agricultural production,improve the quality of laborers,improve agricultural production efficiency,increase farmers'income,and effectively promote the development of agricultural modernization.In the context of the reform of the"separation of three powers",the rural land property rights system still has problems in terms of ownership,use rights,disposal rights,and income rights,which affect the healthy development of agricultural modernization.In this situation,it is necessary to further clarify the subject of rural land ownership,thoroughly improve the right to use rural land,vigorously improve the right to dispose of rural land,effectively protect the right to benefit from rural land,and deeply promote the reform of the rural land property rights system in order to effectively promote the development of agricultural modernization.

The Influence of Land Use and Fish Farming on the Contents of Ca²⁺, Mg²⁺, K⁺and Na⁺in Pond and Reservoir Ecosystems in an Agricultural Small Watershed, China

It is not understood well that how the effects of land use and fish farming on the contents of alkali metals (Ca2+, Mg2+, K+ and Na+) in small water bodies of pond and reservoir ecosystems at the watershed scale. In this study, the concentrations of Ca2+, Mg2+, K+ and Na+ in water bodies were measured for 103 ponds and reservoirs used as fish farming or surrounded by different agricultural land use types in the subtropical hilly watershed of Jinjing (105 km2), China. The two important environmental factors of fishing farming and agricultural land use influenced the spatial variation the contents of alkali metals. The ponds and reservoirs in residential area had significantly higher concentrations of Ca2+ and Na+ than those with other land use types, reflecting the influence of domestic wastewater. Compared with those of natural ponds with non-fish farming, no significant increase of alkali metal contents occurred in fish farming ponds, due to the regular cleaning of ponds by farmers. However, the effect of fish culture on alkali metal contents was still supported indirectly by the fact that the alkali metal contents significantly correlated with nitrate contents in fish farming ponds and but high related with that of DIP in natural ponds. The suitability assessment for irrigation on the pond water indicated that almost all of ponds were suitable for irrigation except some ponds surrounded by residential area and tea plantation. Generally, our results demonstrated that fish farming and agricultural land use affected the contents of alkali metals in ponds and reservoirs. The agricultural water irrigation would be with caution from the ponds with tea plantation and residential area in the subtropical hilly watershed.