基于熵权TOPSIS模型的小流域农地水土保持绩效评价

为解决当前小流域农地水土保持绩效评价中植被覆盖不达标的问题,提出对基于熵权TOPSIS模型的小流域农地水土保持绩效评价方法分析验证。采用多阶的方式,扩展评价反映的信息,进行主、客观多阶权重计算,构建熵权TOPSIS农地水土保持绩效评价模型,采用障碍因子二次核验实现绩效评定。测试结果表明:此次所设计的熵权TOPSIS模型的小流域农地水土保持绩效评价结构经过处理最终得出的植被覆盖率均可以达到65%以上,设计的农地水土保持绩效评价方法更加真实、高效,应变效果更强。

农地水土保持在GIS和RUSLE条件下的小流域规划

经由野外调研、遥感情形下的信息采集,采纳了带有通用特性的土体流失方程,也即RUSLE这一模型,解析了调研得来的数值;在规模偏小的调研流域,明辨了土体侵蚀关涉的时空布设状态。依循最大范畴以内的许可流失量、水土保持这样的拟定规划,变更了惯用的保持措施。具体而言,变更了植被特有的管理因子、水土保持关涉的这种因子,拟定了新颖特性的流域规划。调研得来的新颖规划,带有凸显的耦合特性;GIS协同下的这种规划,凸显出简洁及精准这样的优势。

现代农地水土保持研究与展望

水土流失是我国面临的一大生态难题,随着多年的深入研究,开发出了多种农地水土保持措施,如坡耕地修筑等高梯田可以减缓土壤侵蚀和养分流失,作物留茬可以有效防止水蚀和风蚀,施用有机肥可以改变土壤的理化性质,从而增强土壤抗蚀性。能否将这些措施协同利用,共同治理水土流失,并在此基础上,增加牲畜养殖量,将牲畜粪便腐熟后还田,进而将粪便对环境的污染降到最低,形成一条完整的水土保持循环生态链,对提高当地经济水平和改善生态环境有积极作用。

江西红壤区农业产业政策改革的农户行为响应与水土保持效果分析——以江西省上饶县村庄及农户调查为例

在江西红壤山丘典型区2001年三个样本村111个农户的抽样调查资料基础上,建立了区域农地水土保持效果分析的数量经济模型,分析了农业产业政策改革背景下农户行为对农地水土保持效果的影响。研究表明,当前上饶县农业产业结构调整过程中农地水土流失状况受到农户行为直接影响,农业劳动力的转移、农业生产资料价格、农户受教育水平以及农户土地规模经营的程度等是其影响的主要因素。作者认为,这种状况目前在江西红壤区具有普遍性,因此必须先调整农业政策,增加科技资金投入,保护农业土地利用;其次,优化农户土地长期投入所需要的外部环境,减少长期投资的风险性和不确定性;加大经济刺激力度,增加农户投资获利能力,促进其加大土地长期投入;调整用地结构,优化农业用地组合,发展规模农业,防止水土流失。

PRESSURE OF WATER SHORTAGE ON AGRICULTURE IN ARID REGION OF CHINA

The arid areas in China are mainly located in North China and NorthwestChina. The North China is the main region for food production. There is 31. 19% of the totalfarmland and 26. 01% of the total population, but only 6. 14% of the available water resources ofChina. Groundwater is over pumped (6. 53 X 10~9m^3 every year) in the regions of Beijing, Tianjin,and Hebei Province, so water supply could not meet the water demand there. The distribution of waterin Northwest China is uneven, some inland rivers and lakes are dried up, and desertification hasexpanded since river water in the upper and middle reaches is diverted for irrigation. Up to 2050,population will be up to 1. 6 X 10~9 in China, and industry will be developed fast, therefore 50% ofthe water supply will be used by industry and resident, and water for agriculture will be decreasedyear by year. In the coming 50 years, water demand for agriculture will be increased by 5. 6 x10^9m^3 in the Huanghe (Yellow) River valley, and by 1. 7 x 10~9m^3 in the Northwest China. It willbe impossible for the Huanghe River to meet the water demand, because it always dried up in the coldhalf year since 1984. To avoid water shortage of agriculture in the arid regions, it is necessaryto divert water from the Changjiang (Yangtze) River in the south of China, and to use waterefficiently. It is the best way to use drip irrigation in agriculture, recycle water in industry andresident use, and control water pollution. Otherwise water shortage in the arid regions willrestrict the development of agriculture in China.

Efects of Cropland Cover Changes on Regional Climate over Western China Based on Simulations with RegCM3

The impacts of land cover changes on regional climate with RegCM3. Sensitivity experiments were conducted by in Shaan-Gan-Ning （SGN） in western China were simulated replacing crop grids with different new land cover types in the key area of SGN, where the returning cropland to tree/grass project has been carried out since 1999. The modified new land cover types include desert, forest, shrub and grass. They represent degraded, improved, and maintained vegetation cover with natural canopy in the key area. Results from three individual case studies show that the land cover change causes changes in temperature and terrestrial water variables especially within the key area, while changes in precipitation are found for a larger area. The strongest changes appear where the cropland is degraded to bare soil, leading to increasing temperature and decreases in rainfall, evaporation and soil water. Opposite changes occur when cropland changed into forests, especially with strong increases in soil water. When cropland changed to grass and shrub land, the climatic changes are closer to those with forest cover. This shows the importance of improving and maintaining the vegetation in SGN for the ecosystem and regional climate.

Determinants of Adoption of Sawah Rice Technology among Farmers in Ashanti Region of Ghana

The purpose of this study is to identify the determinants of adoption of sawah technology in Ashanti region of Ghana. It identifies those independent variables that explain adoption and can also facilitate further dissemination and adoption of sawah technology. Sawah refers to leveled rice field surrounded by banks with inlet and outlet for irrigation and drainage. This study uses data from 108 farmers randomly selected from 198 sawah farmers in the study area. Regression analysis showed that age, educational level and year of experience in rice production were the personal factors that determined the adoption of sawah technology among the respondents. The result further showed that contact with extension agents, attendance in previous sawah trainings, land tenure arrangement, yield from sawah farm and attributes of sawah technology determined adoption. This study suggested that adoption of sawah technology should be targeted at young, educated and experienced farmers. Also, security of land must be ascertained by farmers in order to enhance adoption, continuous and sustained use of sawah technology.

Climate Change and Environmental Impact Caused by Anthropogenic

For the last two decades the world has undergone a population explosion which has been accompanied by a speeding up of urbanization and land use for industrial and agricultural products. These involve a vast increase in the discharge of pollutants into very different receiving water bodies, and have had adverse effects on the various components of the environment. For a long time, human has concerned a little of the natural environment. It is obvious that this variation in surface temperature of the earth increases the level of sea due to snowmelt. So climate change is manifested by many phenomena： floods, droughts, fires, tornadoes, cyclones, earthquakes, volcanic eruptions, diseases etc.. The statement today is dramatic. Entire regions were devastated and many rivers and lakes have become polluted around the world. Pollution has it nature which is hard to be absorbed. Where did the different pollutants come from？ What are the risks to the aquatic environment？ To prevent and combat the general decline of these ecosystems, it is important to distinguish and determine the effects of different sources of pollution and any changes that may suffer the physical environment. The climate depends primarily on changes in earth orbit parameters, which affect the solar radiation received by the earth surface. Therefore, human participates strongly to these changes, for example, pollution is the main reason to argue the greenhouse effect, an increase of anthropogenic carbon dioxide （CO2） into the atmosphere, which promotes global warming to the planet. These modifications are already applied in order to ensure durable development in water resources by controlling discharges into streams to preserve water resources for future generations and to ensure reconciliation between man-climate and environment.

Typical Water-land Utilization GIAHS in Low-lying Areas:The Xinghua Duotian Agrosystem Example in China

Xinghua Duotian Agrosystem is a raised ifeld agriculture system with typical water-land utilization. It was identiifed as a Globally Important Agricultural Heritage Systems （GIAHS） site by FAO in April 2014. Based on a literature review and ifeld investigations, we analyzed the history and development, structure and characteristics, functions and values of the Xinghua Duotian Agrosystem in this research. The system has a long history, rich biodiversity, important ecosystem services, traditional adapted agricultural technologies and a folk culture. Altogether, these features form an attractive landscape created by its special water-land utilization. It also has great importance for the livelihood maintenance of the local people. However, the inheritance and conservation effort of Xinghua Duotian Agrosystem is facing great threats from modern agriculture, urbanization and labor loss. This paper wil provide insight into the Xinghua Duotian Agrosystem, and provide scientiifc support for the conservation and development of this special system. It will also provide a good example for similar areas in China and worldwide.

Influence of Agricultural Activity on Nitrogen Budget in Chinese and Japanese Watersheds

To analyze the effect of agricultural activity on nitrogen(N) budget at the watershed scale,a comparative study was conducted at two Japanese watersheds,the Shibetsu River watershed(SRW) and Upper-Naka River watershed(UNRW),and one Chinese watershed,the Jurong Reservoir watershed(JRW).The total area and the proportion of agricultural area(in parentheses) of the watersheds were 685(51%),1 299(21%),and 46 km 2(55%) for SRW,UNRW,and JRW,respectively.The main agricultural land use in SRW was forage grassland,while paddy fields occupied the highest proportion of cropland in UNRW(11% of total area) and JRW(31% of total area).The farmland surplus N was 61,48,and 205 kg N ha 1 year 1 for SRW,UNRW,and JRW,respectively.The total input and output for the whole watershed were 89 and 76,83 and 61,and 353 and 176 kg N ha 1 year 1 for SRW,UNRW,and JRW,respectively.The proportion of discharged N to net anthropogenic N input was 31%,37%,and 1.7% for SRW,UNRW,and JRW,respectively.The two watersheds in Japan showed similar proportions of discharged N to those of previous reports,while the watershed in China(JRW) showed a totally different characteristic compared to previous studies.The high N input in JRW did not increase the amount of discharged N at the outlet of the watershed due to high proportions of paddy fields and water bodies,which was an underestimated N sink at the landscape scale.

Soils and Surface Waters as Affected by Long-Term Swine Slurry Application in Oxisols of Southern Brazil

The accelerated expansion of swine production in Brazil has increased the generation of liquid wastes, which are usually applied to agricultural soils after a simplified treatment and pose potential environmental impacts. The objective of this study was to assess the agronomic and environmental impacts of long-term application of swine slurry(SS) on soil and stream water properties in watersheds dominated by Oxisols in Quinze de Novembro of Southern Brazil. Soil samples(0–30 cm) were collected from farms with continuous application of SS since 1990 at low(40–80 m3 SS ha-1year-1) and high(120–300 m3 SS ha-1year-1) rates of SS. Surface water samples were collected from streams adjacent to the farm fields. Long-term SS application did not change total organic C and particulate organic C compared to cropland and woodland soils without SS application. The high rates of SS increased total N, P, Cu,and Zn and available P and Cu in the topsoil(0–10 cm) compared to woodland and cropland soils without SS application. Surface water analyses showed that fecal coliform bacteria and biological oxygen demand exceeded the legal limits for high quality water(Class 1). Other water parameters(such as NO-3, phosphate and total suspended solids) were within the acceptable limits. Long-term disposal of SS in cropland under no-tillage had impaired water quality in Quinze de Novembro, especially biological parameters. Some best management practices should be adopted, including more rigorous control of SS application to cropland as well as requiring edge-of-field and riparian vegetative buffers.

An Integrated Quantitative Method to Simultaneously Monitor Soil Erosion and Non-Point Source Pollution in an Intensive Agricultural Area

In China, some areas with intensive agricultural use are facing serious environmental problems caused by non-point source pollution(NPSP) as a consequence of soil erosion(SE). Until now, simultaneous monitoring of NPSP and SE is difficult due to the intertwined effects of crop type, topography and management in these areas. In this study, we developed a new integrated method to simultaneously monitor SE and NPSP in an intensive agricultural area(about 6 000 km2) of Nanjing in eastern China, based on meteorological data,a geographic information system database and soil and water samples, and identified the main factors contributing to NPSP and SE by calculating the NPSP and SE loads in different sub-areas. The levels of soil total nitrogen(TN), total phosphorus(TP), available nitrogen(AN) and available phosphorus(AP) could be used to assess and predict the extent of NPSP and SE status in the study area.The most SE and NPSP loads occurred between April to August. The most seriously affected area in terms of SE and NPSP was the Jiangning District, implying that the effective management of SE and NPSP in this area should be considered as a priority. The sub-regions with higher vegetation coverage contributed to less SE and NPSP, confirming the conclusions of previous studies, namely that vegetation is an effective factor controlling SE and NPSP. Our quantitative method has both high precision and reliability for the simultaneous monitoring of SE and NPSP occurring in intensive agricultural areas.

Mapping Soil Texture Based on Field Soil Moisture Observations at a High Temporal Resolution in an Oasis Agricultural Area

Due to the almost homogeneous topography in low relief areas, it is usually difficult to make accurate predictions of soil properties using topographic covariates. In this study, we examined how time series of field soil moisture observations can be used to estimate soil texture in an oasis agricultural area with low relief in the semi-arid region of northwest China. Time series of field-observed soil moisture variations were recorded for 132 h beginning at the end of an irrigation event during which the surface soil was saturated.Spatial correlation between two time-adjacent soil moisture conditions was used to select the factors for fuzzy c-means clustering. In each of the ten generated clusters, soil texture of the soil sample with the maximum fuzzy membership value was taken as the cluster centroid. Finally, a linearly weighted average was used to predict soil texture from the centroids. The results showed that soil moisture increased with the increase of clay and silt contents, but decreased with the increase of sand content. The spatial patterns of soil moisture changed during the entire soil drying phase. We assumed that these changes were mainly caused by spatial heterogeneity of soil texture. A total of 64 independent samples were used to evaluate the prediction accuracy. The root mean square error(RMSE)values of clay, silt and sand were 1.63, 2.81 and 3.71, respectively. The mean relative error(RE) values were 9.57% for clay, 3.77% for silt and 12.83% for sand. It could be concluded that the method used in this study was effective for soil texture mapping in the low-relief oasis agricultural area and could be applicable in other similar irrigation agricultural areas.