土地利用变化对中国土壤碳储量变化的间接影响

中国土壤有机碳储量及其在全球变暖背景下的变化趋势是影响全球碳循环的一个重要因素。土地利用变化对土壤有机碳储量既有直接影响,也有间接影响。一方面,土地利用变化直接改变了生态系统的类型,从而改变了生态系统的净初级生产力（NPP）及相应的土壤有机碳的输入。另一方面,土地利用变化潜在地改变了土壤的理化属性,从而改变了土壤呼吸对温度变化的敏感性系数（常用Q10表示）。在全球变暖背景下,Q10值的改变显著影响着土壤有机碳释放的强度。利用生态系统碳循环过程模型（CASA模型）反演了不同土地利用类型下的Q10值,并评价了土地利用类型的改变对土壤有机碳储量变化的间接影响。研究结果表明,林地与草地转换成耕地后将增大土壤呼吸的Q10值,此外,人类通过灌溉、氮肥的施用也能增大土壤呼吸的Q10值,从而使得全球变暖背景下土壤呼吸的碳通量有所增强。     

土壤甲烷吸收汇研究进展

人类活动导致大气中温室气体浓度增加,是全球气候变暖的主要原因之一。由于陆地生态系统中通气状况良好的土壤是甲烷最大的吸收汇,研究吸收汇强度及其影响因素对估算大气中甲烷储存增量、采取措施增强土壤吸收汇的强度是很有意义的。综述了全球透气土壤吸收甲烷总量及土地利用变化、农业措施对甲烷吸收汇的影响。     

农业土地利用对岩溶地下水影响研究综述

地球表层系统最突出的景观标志是土地利用/土地覆被。人类通过土地利用改变天然土地覆被从而对脆弱敏感的岩溶水文系统产生了重大的影响。文章着重从农业土地利用出发综述了当前农业土地利用对岩溶水影响的研究。农业土地利用对岩溶地下水的影响主要围绕着水质和水量两个核心从以下几个方面展开:天然植被的清除,农业灌溉和排水,农业集约化所带来的化肥杀虫剂等的使用以及污染物质在岩溶含水层中的运移和影响。在此基础上作者从研究内容,理论方法和建立模型等方面都提出了自己的想法和建议。      

基于无人机遥感的四川省昭觉县农业产业园土地适宜性评价

昭觉县是大凉山腹地的典型彝族聚居县,也是国家级深度贫困县,以传统农业居多,为推动农业发展方式的转变,昭觉县开展了现代农业园建设。笔者通过无人机航测,获取了拟建园区的高分辨率影像,使用面向对象的影像分析软件,快速提取了土地利用现状等信息,结合收集的其他资料,筛选了坡度、坡向、断层、地质灾害、土地利用、灌溉、交通、自然保护区8个评价因子,在GIS的支持下,先开展单因子土地适应性评价,然后进行综合评价。结果显示：拟建园区土地适宜性以适宜性高和适宜性较高等级为主,二者合计2.56 km²、占79.26%,超过3/4,土地适宜性好,适宜建设现代农业产业园,适合建设标准化蔬菜温室大棚和露地蔬菜种植基地,建成后,不但可以为周边地市提供蔬菜供应,还可带动园区周围农户增收,促进周围农户脱贫,发展前景好。小型无人机遥感系统具有机动灵活、成本低的优势,能快速获取小区域、大尺度农业产业园区的基础数据,在西南地区小区域土地适宜性评价中应用效果好。小区域土地的自然环境与社会环境相对单一,许多大区域土地适宜性评价指标并不完全适用,需要根据土地利用的主要目的选择合适的评价指标。     

基于不同灌溉方式的水稻作物需水规律试验分析

本文结合观测试验探讨不同灌溉方式下水稻作物的需水量及需水的规律。试验结果表明:在淹灌方式下,水稻完全封垄后的孕穗和抽穗开花期,叶面吸收热能率最大,蒸腾量也最大,需水量也较大;相比于淹灌方式,浅湿灌溉方式下水稻的蒸腾强度都有不同程度的降低,其中以分蘖末期最为明显,蒸腾强度减少了30%,其次是孕穗期的蒸腾强度也减少了27%,其它时期也有不同程度的减少,该灌溉方式下水稻作物需水量减少,有利于农业节水灌溉。研究成果对于水稻作物的节水灌溉方式具有指导价值。     

基于土地利用变化的河西内陆河流域碳排放时空特征北大核心CSCD

土地利用变化是引起碳排放增加的重要原因之一。探索区域土地利用变化引起的碳排放量和碳排放效率问题,对于把握各土地利用类型的碳排放特征、制定土地利用减排策略具有重要意义。本研究以集中国生态系统重要性与脆弱性于一体的典型区域的河西内陆河流域为研究区,利用1985—2020年的土地利用现状遥感数据,通过土地利用动态变化模型、排放系数法深入分析了河西内陆河流域的土地利用变化及其引起的碳排放量和碳排放效率的时空变化特征。结果显示:(1)1985—2020年绿洲规模呈持续扩张趋势,与1985年相比,2020年的绿洲面积相对增加了13.17%;建设用地以单向转入为主,其余土地利用类型之间的双向转变频繁。(2)各土地利用类型的净碳排放量总体呈增加趋势,2020年净碳排放量(113.17×104t)相对1985年(48.57×104t)增加了1.33倍,净碳排放量与绿洲面积显著正相关,耕地和建设用地扩张引起的碳排放量是净碳排放量增加的主要原因。碳排放弹性系数整体呈增加趋势,由1990年的-1.83增至2020年的205.91。(3)1985—2020年的耕地和建设用地碳排放强度、绿洲碳排放强度均呈增加趋势,分别由1985年的32.17 t·km-2和5.09 t·km-2增至2020年的60.74 t·km-2和10.48 t·km-2,但绿洲碳排放强度增加速率小于耕地和建设用地,同期的绿洲碳吸收强度普遍呈递减趋势。(4)工业城市嘉峪关市、金昌市的多年平均绿洲碳排放强度最大,以灌溉农业为主的行政单元相对较低,以畜牧业为主的祁连县最低。本研究通过定量分析河西内陆河流域土地利用的碳排放量及其变化,有助于宏观把握河西内陆河流域土地利用的碳排放特征,对于寻找解决土地利用的减排方案、加强土地管理和推动土地利用的低碳发展模式提供了科学认识基础和决策参考。     

中国旱灾农业承灾体脆弱性诊断与评价

旱灾是世界上影响面最广、造成农业损失最大的自然灾害类型，世界近一半的国家干旱严重。中国旱灾频繁，每年旱灾损失占各种自然灾害损失的15%以上，随着人口和农业的快速发展，农业承灾体脆弱性对灾情的放大也在增加。基于灾害系统理论，从致灾因子和耕地承灾体的区域组合角度，在旱灾频发高值区，选择雨养农业、灌溉农业和水田农业为主要承灾体类型，构建了农业旱灾脆弱性生产压力和生活压力，灾前—灾中易损性和灾中—灾后适应性等农业旱灾承灾体脆弱性诊断指标体系。提出脆弱性评价的区域模型，即：雨养农业的易损—适应模型（兴和）、灌溉农业的生产—生活压力模型（邢台）和水田农业的需水—灌水模型（鼎城）。基于农业承灾体脆弱性评价，提出制定适应降水变化的波动土地利用结构调整区域政策、建立农业生态—生产范式、建立“水银行”管理机制、建立用水效益和开源节流的评估体系以及加强“截水—抽水—控水”为一体的灌溉系统工程建设，提高灌溉应急能力等对策，以期为农业旱灾的防御和区域粮食安全决策提供科学依据。     

江西丰城董家—尚庄地区土地质量地球化学评估方法

江西丰城董家—尚庄土地质量评估是在土壤理化性质的基础上,根据K、Ca、Fe、Mn、Na、As、Cd、Se、F、I、pH及有机质等指标,运用层次分析法和隶属函数建立土地质量地球化学评估模型对其进行评估。结果表明：优质、优良、良好、中等土地面积分布分别占总面积的0.2%、74.9%、9.3%、15.6%,反映土地质量地球化学综合分等有明显差异。优良以上的土地占该区土地面积的75.1%,大面积分布于研究区,是发展绿色无公害农产品的最佳区域;良好等级的土地位于研究区中部,适宜发展一般性农业,应加强保护与合理利用;中等土地分布于研究区东部铁路沿线及赣江冲积平原,应避免种植粮食、蔬菜等食用作物。     

大洼灌区稻田预测指标及控肥节水灌溉技术探讨

大洼灌区是以稻田为主的灌区,农业用水以水稻为主。为预测水稻耗水量,须分析育苗期、稻田期和生长期耗水量等定额。采用水稻生态肥控节水灌溉技术和节能灌溉技术,使灌区水稻产量和水分利用效率分别提高10%～15%和15%～20%。可以提高水分利用效率和肥料利用率,减少深层渗漏,降低土壤酸化和地下水污染的风险,保护生态环境,促进农业良性循环,实现精准化和产业化经营。对保证粮食安全和农业可持续发展具有重大意义。     

河套灌区井渠联合运用优化灌溉模型

针对河套灌区的地面水与地下水联合运用问题,提出了井渠结合优化灌溉模型,以最佳种植模式和最优工程运行策略,达到控制地下水位、防治土壤盐碱化、获得农作物稳产高产的目的.模型有调蓄地面水源、土壤贮水层、地下含水层的能力.优化计算成果与266.7hm2试验示范区的实际运行结果相吻合,节水、节能、增产及控制地下水位、改良盐碱地等效果十分显著,这对发展节水型灌溉农业具有重要的现实意义.     

Soil salinity and sodicity in a shrimp farming coastal area of the Mekong Delta,Vietnam

Soil salinity and sodicity are environmental problems in the shrimp farming areas of the Cai Nuoc district, Ca Mau province, Vietnam. In 2000, farmers in the district switched en masse from rice cropping to shrimp culture. Due to recent failure in shrimp farming, many farmers wish to revert to a rotational system with rice in the wet season and shrimps in the dry season. So far, all their attempts to grow rice have failed. To assess soil salinity and sodicity, 25 boreholes in shrimp ponds were analysed in four consecutive seasons from 2002 to 2004. The results showed that soil salinity was quite serious (mean EC_e 29.25 dS m⁻¹), particularly in the dry season (mean EC_e 33.44 dS m⁻¹). In the wet season, significant amounts of salts still remained in the soil (mean EC_e 24.65 dS m⁻¹) and the highest soil salinity levels were found near the sea. Soil sodicity is also a problem in the district (exchangeable sodium percentage range 9.63–72.07%). Sodicity is mainly a phenomenon of topsoils and of soils near the sea. Both soil salinity and sodicity are regulated by seasonal rainfall patterns. They could together result in disastrous soil degradation in the Cai Nuoc district.     

农地利用变化假说与相关的环境效应命题

将用途转移和集约度升降这两种类型的土地利用变化整合在一个过程中,解释变化机制的理论,有古典经济学的地租理论,还有若干理论性假说。这些假说又常常与一些土地利用的环境效应命题联系在一起,扩充为解释人地关系的假说。综述了解释农地利用变化的四大假说（包括基于马尔萨斯人口论的土地面积持续扩张假说、博斯鲁普的需求诱发型集约化假说、吉尔茨的集约度弹性假说、土地利用粗放化假说）和农地利用环境效应的三大命题（包括农地面积扩张造成土地退化、优质土地的集约化间接促使生态脆弱地区环境改善、农地利用粗放化和弃耕促使环境和生态恢复）,以及围绕这些假说和命题的争论和实证研究,旨在为土地利用变化的情景构建、模型模拟及愿景设计提供学术依据。     

Land Reserves in Southern Sumatra/Indonesia and their potentialities for agricultural utilization

In contrast to overpopulated Java the neighbouring island of Sumatra still provides huge unused land reserves. However, by far not all of these reserves can be regarded as real agricultural potentials, e.g. for resettlement projects. Especially the poor soils often prove an agricultural handicap. Besides soil fertility the existing vegetation has to be conidered. Thus, for example, the so called “alang alang grass savannas” in general show better potentialities than forest areas, while most of the swamps prove rather unsuitable for agricultural development. With regard to the already existing landuse types the cultivation of perennial bush- and tree crops, for instance rubber, seems to be best suited for further expansions. An expansion of annual food crops would be feasible too, however only be applying heavy capital inputs; here wet rice cultivation would be more appropiate than the permanent cultivation of annual upland crops like cassava, maize, etc. The traditional shifting cultivation does not serve as an alternative any longer. Animal breeding will have its difficulties, with the exception of certain highland areas. Taking into account all ecological, social, and economic reservations it is concluded that, in spite of considerable restrictions, a good part of the land reserves in southern Sumatra could still be opened and used successfully for agricultural purposes.     

吉林西部大安灌区土壤贮水能力空间变异特征及土壤水分有效性

为研究吉林西部土壤贮水能力的空间分布特征和水分有效性,以吉林西部大安灌区为研究对象,通过试验测定土壤贮水量及根系区土壤的水分特征曲线,并利用van Genuchten模型进行水分特征曲线拟合,结合经典统计和地统计分析方法分析土壤贮水量空间变异特征。结果表明:盐碱土和非盐碱土吸持贮水量、滞留贮水量和饱和贮水量的均值之间不存在显著性差异(P0.05),实际贮水量均值存在显著差异(P0.05);土壤实际贮水量呈现由西向东、由北向南逐渐升高的变化趋势,且南北方向的空间变异性均高于东西方向的空间变异性;轻度盐碱地、水田和旱田实际有效含水量分别占其最大有效含水量的78.94%、58.28%和56.62%,水分有效性较高,蔬菜地、高粱地、草甸土以及中度和重度盐碱土实际有效含水量占其最大有效含水量的20.83%27.13%,土壤水分有效性较小;水田、轻度和中度盐碱地的贮水和持水能力强,旱田和蔬菜地土壤贮水能力较强,持水能力中等,而重度盐碱地、高粱地、草甸土等土壤的持贮水能力较弱。研究结果对旱改水工程水资源管理和预防次生盐渍化有重要意义。     

节水稻基农田作物轮作与灌溉模式需水规律研究

采取田间试验方法,研究了南方丘陵典型季节性干旱区节水稻基农田作物轮作与灌溉模式的需水规律和稻田水分利用率.结果表明,节水稻基农田作物轮茬与灌溉模式通过对水稻和油菜等作物产生的生长调控作用和补偿生效应,使植株蒸腾量、棵间蒸发量及稻田渗漏量大幅降低,各阶段的腾发量、需水强度和需水模系均发生显著变化,形成了稻基农田作物轮茬与灌溉模式新的需水规律.与常规双季模式相比,节水灌溉双季稻模式、水旱轮作双季稻模式、稻油轮作模式的需水强度分别减少了0.76、1.15、0.71 mm/d,渗漏强度分别减少了0.12、0.16、0.19mm/d,水分利用率提高了30.14%、47.95%、17.81%.     

Eroding battlefields: Land degradation in Java reconsidered

Land degradation has been a major political issue in Java for decades. Its causes have generally been framed by narratives focussing on farmers’ unsustainable cultivation practices. This paper causally links land degradation with struggles over natural resources in Central Java. It presents a case study that was part of a research project combining remote sensing and political ecology to explore land use/cover change and its drivers in the catchment of the Segara Anakan lagoon. Historically rooted land conflicts have turned the land into a political battlefield, with soil erosion being the direct outcome of the political struggles. Starting from an analysis of environmental changes using satellite images and historical maps, the research explored a history of violent displacements in the frame of a series of brutal insurgencies and counterinsurgencies in the 1950/60s. In these struggles over national political power, entire villages were erased, and peasants’ land was appropriated by the state. This political history is ‘inscribed’ in today’s landscape. The contested land comprises some of the most erosion-prone sites in the entire catchment of the lagoon. The landscape of erosion is a landscape of conflict and a symbol of historical violence and injustice. In line with our research in other parts of the catchment, the case study presented here challenges dominant political discourses about the nature of upland degradation in Java. It provides insight into still unresolved and underexplored chapters of Indonesian history and presents a strong plea for combining land use change science and (historical) political ecology.     

农用土地环境质量的全要素整合评价

把影响农用土地环境质量的所有环境要素综合起来,分解量化指标,重建评价体系,提出宏观指标分等、微观指标定级的新观点,并就县市级农用土地环境质量进行全要素整合评价和等级评定进行了探讨。结果表明,保证评价精度和把握等级评定的关键步骤是正确选择和划分评价单元;土地农业综合生产能力和清洁度指标是农用土地环境质量的综合反映和集中体现,是所有被整合调查要素和评价因素中最重要的两个刚性指标,在评价中必须加大权重;全要素整合评价可以弥补农业或土地部门多指标评价的不足,能够比较全面和客观地反映农用土地环境质量状况。农用土地环境质量的全要素整合评价为新一轮土地利用规划修编、基本农田保护区准确划定、农用土地分等定级和建设用地的区划调整以及土地基准定价能提供有力技术支持。     

Land use effects on the properties of an Alfisol on the Jos Plateau, Nigeria

This study was carried out to determine the effects of different land-use types on the properties of an Alfisol on the Jos Plateau, Nigeria. Areas being used for nature conservation (forest), grazing and maize cultivation were chosen, and the three are contiguous within a nearly level, moderately well-drained site. Within each of the three land-use areas, a plot of 30 x 20 m was chosen. Each plot was divided into 6 grids of 100 m² size. Within each of these grids, four sampling sites were chosen by throwing up a coin four times. The four surface soil (0–5 cm depth) samples taken at the points where the coin landed, were mixed to form the composite sample, out of which sizeable portion was taken. This means that six soil samples were taken for each land use area (forest, grass, and cultivated). Same procedure was repeated for each of the following soil depths 5–15, 15–30 and 30–50 cm. Laboratory soil analyses were carried out while analysis of variance was used to test the significance of mean difference. The results show that forest clearing for grazing and maize cultivation has lead to significant decreases in most soil fertility variables. Organic matter levels of the grassland and cultivated soils are just about 28% and 13%, respectively, of that of the forest soil in the 0–5 cm depth, while they are 36% and 19%, respectively, in the 5–15 cm depth. Exchangeable cations and effective cation exchange capacity are also significantly higher in the forest soils. The effects are attributable to soil organic matter decomposition and nutrient removal resulting from forest clearance, maize cultivation and grazing. Hence, for sustained agricultural productivity, the soils require adequate inorganic and organic fertilizer additions together with appropriate cultural practices such as agroforestry, crop rotation and mixed cropping involving legumes.     

A critical political ecology of cotton and soil fertility in Mali

The aim of this article is to analyse the influence of commodified cotton production on soil fertility in southern Mali. From the late 1950s and until recently, production of both cash-crop cotton and food crops have increased rapidly in this region, giving it a reputation of being an African ‘success story’. The flip side of this economic success is, however, said to be environmental degradation especially in terms of loss of soil fertility. We collected 273 soil samples in 19 villages located in various zones of land use intensity. In each village, the samples were collected on up to six different land use types varying with intensification. The analysis of the soil samples showed that soil fertility was highest in the sacred groves that have been protected and never cultivated. However, comparing soils under continuous cultivation and soils under fallow no clear trends in soil fertility were found. Cotton yields have declined since the early 1990s, while the total use of fertilisers has increased. This is often interpreted as proof of soil exhaustion, but there is no clear indication in this study that cotton-cereal rotation as practiced by smallholders in southern Mali reduces soil fertility. We argue that the decline in yields has been caused by an extensification process. Cotton fields expanded rapidly, due to attractive cotton prices in the 1990s, leading to falling investments per ha and cultivation of more marginal lands. These findings also have implications for a political ecology of commodity production and lead us to argue for an open-ended and empirically based ‘critical political ecology’.     

The Effect of Farmland Fragmentation on the Intensity of Farmland in Different Utilization Ways

The agricultural development of mountainous areas in China is undergoing the transformation from the traditional agricultural land use mode dominated by single and inefficient grain production to the new agricultural land use mode such as high-yield and efficient horticultural crops. The research on the impact of farmland fragmentation on the agricultural land intensity degree is the basis of agricultural modernization and land remediation in mountainous areas. Based on the UAV high-resolution remote sensing image data of two typical villages in Guizhou Province and the questionnaire survey data of farmers, using the road accessibility index of farmers' plot, the area index and the shape index to measure the degree of farmland fragmentation, we analyzed the impact of different degrees of farmland fragmentation on the traditional and new types of farmland use intensification. The research showed that the farmland fragmentation had a significant negative impact on the intensive degree of agricultural land, but the impact on the intensive degree of agricultural land in different ways of use was different. With the intensification of the degree of farmland fragmentation, the impact on the input and output of horticultural crops and other new-type agricultural land utilization was less than that of grain crops and other traditional agricultural land utilization. Adjusting agricultural structure and transformation of farmland utilization greatly alleviated the negative impact of farmland fragmentation on farmland intensity in mountainous areas.