共查询到20条相似文献，搜索用时 31 毫秒
1.
The Pampa de Chaparrí (Pampa) in hyperarid northwest coastal Peru is an ideal area to study late prehispanic agricultural technology and production because irrigation canals and furrowed fields have been preserved since abandonment approximately 500 years ago. We collected 55 samples for soil characterization, fertility, and micromorphic analyses and compared these results to a noncultivated control soil previously sampled in an adjacent valley. Natural soil fertility levels for maize, cotton, and bean production were generally high during late prehispanic cultivation in the Pampa. Maintaining adequate nitrogren levels for production, however, would have required external inputs from livestock manure, guano, or leguminous plants. The management of low soil salinity levels was possible because of rapidly permeable soils and irrigation waters low in salt. Based on available water capacity and climate conditions, the Blaney‐Criddle Equation yields evapotranspiration rates indicating that irrigation frequency was necessary in a range of every 10–16 days during the growing season. © 2004 Wiley Periodicals, Inc. 相似文献
2.
Thomas J. Bassett 《Geoforum》2010,41(1):44-55
This paper examines the extent to which certified fairtrade cotton programs in West Africa present an alternative to the conventional cotton economy. Two fairtrade programs operating in Burkina Faso and Mali serve as case studies. The paper argues that fairtrade cotton fails to offer an alternative to conventional cotton because it works within the same commodity chain that impoverishes farmers in the first place. Cotton grower organizations seek more power within the conventional cotton sector to increase incomes and improve the living standards of all cotton growers. They are also active at the international level to eliminate the inequities of international trade. It is in these arenas that cotton growers are struggling to improve their incomes and livelihoods. Fairtrade does not address these fundamental inequities and power relations. The slim pickings of these programs are further evident in the very small amount of cotton produced and marketed as fair trade. Plans to expand production from less than 1% to 10% by 2012 are unrealistic in light of the introduction of genetically modified cotton and the limited market demand for fairtrade cotton. Despite these limitations, fairtrade cotton programs are producing some positive effects, notably women’s participation in cash crop cultivation, higher cotton quality, and the diffusion of organic farming techniques. An innovative direct marketing agreement linking the National Cotton Growers’ Union of Burkina Faso with the US women’s apparel company Victoria’s Secret indicates that alternative trading relations can be constructed outside the conventional commodity chain. 相似文献
3.
近年来农用地土壤质量受重金属污染影响进而导致农产品受到威胁的问题愈发严重,然而关于土壤质量评价的研究很少考虑土壤污染状况,忽略了土壤污染风险对土壤质量的影响。本文以某典型制造业县级市为例,在以土壤理化性质为主要指标的土壤肥力状况评价基础上,对研究区土壤重金属进行污染风险管控类型划分。通过建立分段函数将土壤污染风险管控类型划分结果引入土壤质量评价体系,对农用地土壤质量进行评价。结果表明：研究区土壤理化指标的变异系数从大到小为速效磷(AP)含量>土壤电导率(SEC)>全磷(TP)含量>土壤有机碳(SOC)含量>阳离子交换量(CEC)>全氮(TN)含量>pH。土壤肥力状况随地势降低和河流增加呈现升高的趋势,高肥力区主要分布在平原区西北部和平原区东北部,低肥力区主要分布在东南部丘陵山区和西部低洼区,肥力过渡区环绕低肥力区分布。农用地土壤污染风险管控类型的划分结果表明,Cd、Hg、As、Pb、Cr、Ni、Cu和Zn 8种重金属中至少有88.89%的Cd样点和98.61%的Cr样点属于优先保护类,11.11%的Cd样点、1.39%的Cr样点属于安全利用类,该区重金属污染以Cd为主。土壤质量评价结果表明,土壤质量总体分布与土壤肥力状况分布规律类似,但由于受土壤污染风险的影响,研究区西南部低质量土壤范围向东扩张,东南部低质量土壤分布范围更小,更密集化。上述研究结果说明,引入土壤污染风险管控类型划分结果一般会对土壤肥力状况作减幅修正,并在一定程度上改变原土壤肥力状况的空间分布格局。 相似文献
4.
Abdurazack Karriem 《Geoforum》2009,40(3):316-325
The Brazilian Landless Movement (MST) is widely acknowledged as one of the most organized, dynamic, and influential social movements in Latin America. The MST has increasingly inserted the struggle for land within larger political contestations for broad social change, leading conservatives and leftists alike to describe it as a “first class actor” in Brazilian politics. What explains the move from corporatist struggles for land to broader counter-hegemonic contestations; put differently, how did the MST come to acquire ‘global ambition’? Much of the literature on the MST analyzes its external actions but without explaining what drives these actions. This paper utilizes a Gramscian political ecology approach to comprehend the MST’s political actions and its rise and transformation into a counter-hegemonic political actor. Specifically, I evaluate the development of the MST’s organizational praxis from corporatist struggles for land in the late 1970s to ‘global ambition’ and changing nature-society relations by the early 2000’s. Such an approach brings to light the role of organization building, political education, alliance building, and subaltern agency in propelling the MST’s political mobilizations. In so doing, this paper contributes to the literature on the MST and collective action. This paper also engages with a ‘politics of scale’ since the conquest of geographic scale is critical to understanding the MST’s national growth and political actions. This paper concludes by arguing that the rise and transformation of the MST into a vibrant counter-hegemonic actor in Brazilian politics was a gradual process that matured as it territorialized into a national movement. 相似文献
5.
A. Wendy Russell 《Geoforum》2008,39(1):213-222
In this paper, I argue that genetically modified organisms (GMOs) have inherent potential to contribute to socially and environmentally sustainable agriculture by virtue of their ‘biological embeddedness’. Their actual ‘performance’ and how this contributes to sustainability depends on the ‘mutual shaping’ of technology and context. While much attention has been given to the design context of GMOs, this paper considers the influence of the application context and of users. A case study investigating the use of insect-resistant and herbicide-tolerant GM cotton in the cotton-growing region of New South Wales in Australia is presented. The study was based on focus groups with farmers and other stakeholders in a cotton-growing community. It demonstrated a range of direct and indirect effects of GM cotton use, both positive and negative for sustainability, and the ways in which these effects were influenced by the local social context. The influences of the biotechnology industry context, in limiting the contributions that gene technologies can make to sustainability, were also considered, and remedies suggested. I argue that the polarity of the GM debate is hindering progress on these issues, and that a more balanced approach to our analysis of GMOs is necessary in order to fully understand, and to influence, their role in the future of rural spaces. 相似文献
6.
Alex Loftus 《Geoforum》2009,40(3):326-334
This paper seeks to explore the radical democratic potential in urban artistic interventions. It does so through bringing Gramsci’s concept of nature together with his ‘cultural writings’ and broader debates around avant-garde artistic practice. Empirically, I focus on the work of City Mine(d), a Brussels-based interventionist collective, and Siraj Izhar, a London-based artist-activist. Within Gramsci’s writings, I argue, socio-natural relationships emerge through sensuous activity or work. Making a somewhat more ambitious claim, I suggest that Gramsci’s concept of nature rests on what geographers have come to understand as the production of nature. Whilst attention has only recently turned to this implicit political ecology, much greater attention has been focussed on Gramsci’s cultural insights. For Gramsci, cultural struggles are an integral part of the effort to shape a new reality. Whilst he emphasises the ‘bottom up’ nature of such struggles, the intervention of enlightened outsiders is often a necessary and frustrating complement. However, by turning attention to the manner in which hegemony relates to the production of nature, and through bringing this into dialogue with radical artistic practice, such implicit elitism might be challenged. City Mine(d) and Izhar, I argue, develop a non-vanguardist politics that sees the contestation of hegemony as a struggle integral to the day-to-day nature of cities. 相似文献
7.
U. Scholz Dr. 《GeoJournal》1980,4(1):19-30
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. 相似文献
8.
Abu Muhammad Shajaat Ali 《地球科学进展》2006,21(2):183-191
在实地采访、地块土地利用/覆盖调查和1 260个土样的收集和实验室分析等野外工作的基础上,对比分析了1984—1985年和2003—2004年265个家户的人口、农业系统、土地利用和土壤质量数据,研究了孟加拉国6个村庄农业诱导强度增强对土地和土壤质量的影响。1984—2004年家户和土质数据的百分比变化用来构建诱导强度增强模型和土地退化模型中的统计变量和土地退化指标。结果表明：研究区种植强度和土地生产力的增加主要是由于低压泵灌溉的普及,化肥和杀虫剂的使用以及水稻、蔬菜和虾生产的多元化高产。诱导强度增强模型可以解释研究区81%的种植强度增量和73%的土地生产力增量。人口压力和市场驱动也诱发了农业利用强度的增加;环境约束起到了一定制约作用;低压泵灌溉等应对干旱的技术也对农业增产有一定贡献。然而动力耕作机、低压泵灌溉和化学物质的持续利用再加上除草性水稻、蔬菜和虾的频繁耕作和养殖已经导致土壤结构、质地和化学属性的退化,生产力也有所降低。利用强度越大的土地退化现象越严重,生产力下降得也更多。土地的不断退化将有可能会引发孟加拉国的马尔萨斯危机。 相似文献
9.
微咸水在西北干旱区广泛分布, 越来越多地被运用于灌溉棉花(Gossypium hirsutum L.)等作物.微咸水中NaCl和微量元素含量比淡水高, 有关NaCl和微量元素各自对棉花生长的影响已有大量研究, 而他们对棉花生长的相互作用研究比较缺乏.选取对棉花生长作用敏感的NaCl和微量元素Zn, 开展不同NaCl和Zn浓度灌溉水盆栽试验.结果表明, 缺Zn环境下, 在灌溉水电导率为2.90~3.95 dS/m的范围内, 随着电导率增大, NaCl促进棉花根和地上部生长及皮棉产量增加.富Zn环境下, 灌溉水电导率大于5.04 dS/m时, 随着电导率增大皮棉产量明显下降.在灌溉水中Zn浓度为0.192 0~3.068 0 μmol/L的范围内, Zn浓度越大棉花营养生长越快; 大于0.767 6 μmol/L时, 随着Zn浓度增大皮棉产量下降.灌溉水中NaCl和Zn对棉花生长和产量的影响作用, 表现为相互拮抗作用关系.棉花叶的Ca、K、Mg、B和Fe含量以及铃的Cu和Zn含量高于其他组织, Na和Mn不易迁移, 易富集在棉花根部.Zn在盐胁迫条件下影响棉花对营养元素的吸收, 使棉花体内相关营养元素含量发生变化, 进而影响棉花生长及产量. 相似文献
10.
An evaluation of the contribution of soil micromorphology to the study of ancient arable agriculture
This article provides an overview of the development of soil micromorphological studies of ancient agriculture and the current position of research in this field. The stance adopted by the authors is deliberately combative, and it is hoped that the article will stimulate discussion of the current limitations and potentialities of the technique. The findings of this review may be summarized in three proposals: (1) Soil micromorphology cannot be used at present to identify cultivation in ancient soils. Ambiguous or multiple interpretations of soil micromorphological features are unlikely to be resolved, so that the detection of large scale agricultural features in the field (cultivation marks, lynchets) will remain the most secure and direct guides to the presence of a former cultivated soil. Indirect evidence on inferred land use can be provided from pollen and land snail evidence. (2) Micromorphology should retain a key role in the determination of the impact of agriculture on soils, encompassing issues such as erosion, soil structure, fertility, and biological activity. These can be related to agricultural practice: methods of tillage, manuring, soil conservation, and fallowing. (3) Three areas of micromorphological research can be proposed that address the impact of agriculture on soil: (a) the study of well-sealed, buried agricultural soils which have a clearly understood archaeological context; (b) the study of recent soils with known agricultural histories; (c) the establishment of controlled experiments with ancient agricultural techniques. © 1998 John Wiley & Sons, Inc. 相似文献
11.
Merje Kuus 《Geoforum》2007,38(2):241-251
This paper investigates the role of intellectuals in the production of geopolitical discourses. It analyzes how the cultural capital of humanist credentials and artistic aura functions to authenticate and legitimate geopolitical claims. Drawing empirically from Central Europe and especially Estonia, I argue that intellectuals are central to the production of a particular ‘cultural’ concept of geopolitics - the notion that foreign policy expresses the state’s and the nation’s identity. As cultural capital gives intellectuals a special license to speak about culture, it constitutes an essential component in geopolitical discourses in Central Europe.The paper contributes to Europeanist geography by clarifying the mechanisms through which Central Europe is cast externally and internally as a place particularly imbued with culture and identity - a place whose integration with the EU and NATO represents its cultural ‘return’ to Europe. It takes us beyond the romanticized notion of intellectuals - especially the formerly dissident ones - as ‘speaking truth to power’, and offers a more subtle account of their role as producers of power discourses.Beyond Central Europe, the paper underscores the political and cultural milieu of geopolitical claims and the specific structures of legitimacy through which these claims are justified and normalized. A nuanced understanding of the role of ‘culture’ in geopolitical discourses requires that we closely examine the cultural and moral capital of intellectuals. This would also enable us to better delineate human agency in the production of geopolitics. 相似文献
12.
Laïla Smith 《Geoforum》2008,39(1):236-251
This article presents a case study of the World Bank’s relationship with South Africa to argue that the Bank uses its knowledge brokering role as a device to facilitate the development of a lending relationship with countries that may initially be reluctant to enter into this kind of engagement. This article reviews the World Bank’s 10-year effort to develop a lending relationship with South Africa. The Bank inserted itself into the country in the early 1990s at the outset of its democratic transformation. Throughout the decade, South Africa acceded to the Bank’s policy interventions through technical assistance rather than through a concerted lending programme. In doing so, South Africa internalized the Bank’s market-driven political economy framework underlying its technical assistance programme. The country’s application of the Bank’s knowledge has had questionable outcomes for its development agenda. While the Bank’s ‘expert’ interventions may have offered valuable technical insights, it neglected the politics of distribution that are embedded in a more localized knowledge formation process. The result has led to the instrumentalization of local governance and undermined the engagement of civil society actors in the construction of a democratic state at the local level. 相似文献
13.
Plant-available reserves of major base cations, Ca2+ and Mg2+, decreased markedly in soils over the past century, thus posing a potential threat to forest ecosystem health. Trees are thought to obtain dissolved Ca2+ ions mainly from an easily accessible soil-water reservoir also termed the ‘exchangeable cation pool’. The status of Ca reserves in this soil pool is sensitive to anthropogenic perturbations such as soil acidification induced by acid rain and/or excessive timber harvesting. Here we show that in a base-poor forest of the northeastern USA (i.e. Wachusett Mountain, Massachusetts) the ‘exchangeable Ca pool’ of deeper mineral soils has a unique isotope signature that is significantly enriched in the radiogenic 40Ca, due to the dissolution of K-rich silicate minerals such as biotite. Using a simple isotope mass balance, and assuming that the input of Ca from biotite has a εCa signature of ∼16, the results of our calculation indicate that the weathering of biotite may supply a sizeable fraction, up to 25%, of Ca2+ ions into the ‘exchangeable cation pool’ of deeper mineral soils. Importantly, samples of local vegetation (i.e. woody tissues of red oak) show no detectable excess of the radiogenic 40Ca, and based on our model the upper limit of a possible biotite-derived Ca contribution in vegetation is estimated at ∼5%. We also found no evidence of the radiogenic 40Ca signal in the samples of forest floor and the uppermost organic-rich soils (0-15 cm depth), which in turn suggest that over the long-term development of the forest and its organic matter accumulation, the vegetation growth must have also relied primarily on the non-radiogenic Ca sources. Based on our experimental data, such sources may include (i) wet atmospheric deposition, (ii) the organically-complexed Ca in topsoil horizons, and (iii) chemical weathering and/or fungal-mediated dissolution of apatite and Ca-rich plagioclase. Hence, our stable and radiogenic Ca isotope data indicate that the studied base-poor forest is able to bypass the ‘exchangeable cation pool’ of deeper (i.e. below 15 cm) mineral soils, and still manages to meet its nutritional requirements with respect to Ca. Another important implication of this study is that the organically-complexed Ca in the topsoil horizon (0-15 cm depth) has to be tightly bound to the ion exchange sites, otherwise the large radiogenic 40Ca signatures present in the ‘exchangeable cation pool’ of deep mineral soils would be swamped by the downward gravitational flux of non-radiogenic Ca from the decaying organic matter and litterfall. Hence, the limited mobility of the organically-complexed Ca in soils and its tight biological cycling could explain the lack of a significant impact of vegetation on the Ca isotope systematics observed in large rivers. 相似文献
14.
Thomas J. Bassett 《Geoforum》2009,40(5):756-766
Côte d’Ivoire’s adoption of land privatization policies promoted by the World Bank and European Union is producing new land use patterns in the countryside. A centerpiece of these policies is the 1998 Rural Land Law that aims to restructure rural economic life along agrarian capitalist lines. The purported “development” objective of land privatization is to stimulate agricultural productivity based on the assumption that land titling will lead farmers and herders to make greater investments in their production systems. This paper argues that the mobile livestock raising system of immigrant FulBe pastoralists in Côte d’Ivoire is threatened by the new land law. Since mobility is crucial to animal health and fertility rates, I argue that reduced mobility will lead to lower livestock productivity. Although the land law has yet to be implemented, its very existence is leading prospective claimants to test their land rights by planting orchards and lending land to immigrant farmers. The monetization of land lending and grazing rights is increasingly common. Land disputes over who has the power to allocate land are also on the rise. I argue that this heightened interest in “tenure building” is constraining herd mobility, especially for herders with limited resources to negotiate access to rangelands. On the other hand, land privatization is strengthening the hand of local cattle-owning farmers who increasingly practice mobile livestock raising and compete with FulBe herders for grazing lands. Under these new conditions of land access, control, and competition, FulBe herd mobility and productivity are at risk of declining. 相似文献
15.
Adewale Emmanuel Olowolafe 《GeoJournal》2008,71(2-3):83-91
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. 相似文献
16.
Soyeun Kim 《Geoforum》2010,41(4):627-637
This article aims to illustrate the extent and ways in which a traditional development aid project became the focus of a ‘greening’ process in the 1990s (and beyond). The article examines the San Roque Multi-purpose Project in the Philippines - a major Japanese bilateral international cooperation project - from a political ecology perspective. The analysis highlights how a complex story of contemporary aid dynamics in the bilateral Japan-Philippines relationship influenced this ‘greening’ process. The article interrogates critically and empirically the stated greening of a proto-type development aid project. This specific example of the practices of the Japanese aid industry is set within the context of the wider political economy of both donor and recipient elite interests. 相似文献
17.
Marginalisation and revolt among the Tuareg in Mali and Niger 总被引：1，自引：0，他引：1
Thomas Krings 《GeoJournal》1995,36(1):57-63
The article is dealing with the origins, causes and forms of the ongoing Tuareg revolt in Mali and Niger which since 1990 has developed to a new serious trouble spot in two of the least developed countries in the Sahelian zone. Four crises seem to be the decisive factors for the marginalisation and deprivation of the Tuareg:1. The disturbance of their pastoral lifestyle and the loss of access to livelihood resources due to state intervention and development projects. 2. The negation of the existence of the Tuareg ethnic community as a whole by the black African political leaders. 3. The increasing refugee migrations from Mali and Niger to neighbouring countries. 4. The exclusion of the Tuareg from political participation in the postcolonial state.The differences between the conflict in Mali and Niger are discussed within its country specific political geographical background. It is evident that peace is only possible if substantial participation of the Tuareg in the political, administrative and judiciary institutions is guaranteed. In the field of development policy a fundamental change is necessary from mainly farmers-oriented development approaches to concepts which respect pastoral needs and nomadic land use rights. 相似文献
18.
Salar Rezapour 《Environmental Earth Sciences》2014,71(5):2199-2210
Monitoring general variability of soil attributes is a fundamental requirement from the point of view of understanding and predicting how ecosystems yield. In order to monitor impact of different land use types on the combination of morphological, clay mineralogical and physicochemical characterizes, 42 soil samples (0–30 cm) were described and analyzed. Soil samples belonging to Cambisols and Vertisols reference soil groups collected from three neighboring land use types included cropland (under long-term continuous cultivation), grassland, and forestland. The soils were characterized by high pH (mean of 7.1–7.5) and calcium carbonate equivalent (CCE) (mean of 35–97 g kg?1) in the three land use types. The weakening in soil structure, hardening of consistency, and lighting of soil color occurred for the cropland under comparable condition with grassland and forest. Changes in land use types produced a remarkable change in the XRD patterns of clay minerals containing illite and smectite due the dynamic and removal of potassium. Continuous cultivation resulted in an increase in sand content up to 35 % while silt and clay content decreased up to 22 and 18 %, respectively, as compared to the adjoining grassland and forest mainly as a result of the difference of dynamic alterational and erosional process in the different land use. Long-term cultivation caused a negative and degradative aspects on soil heath as is manifested by the increasing in soil pH (a rise of 0.3–0.46 unit), electrical conductivity (EC) (a rise of 1.78–5.5 times), sodium absorption ration (SAR) (a rise of 10–51 %), exchangeable sodium percentage (ESP) (a rise of 3–46 %), and the decrease in soil organic C (a drop of 12–41 %), along with soil fertility attributes. Overall, the general distribution of soil organic C, total N, available P and K, cation exchange capacity (CEC), and exchangeable cations (Ca, Mg, and K) followed the order: forestland > grassland > cropland. The general distribution of EC, SAR, ESP, and exchangeable Na, however, followed the order: cropland > grassland > forestland. Soil quality index (SQI), calculated based on some physicochemical properties, specified that cultivation led to a negative effect in SQI for both Cambisols (a drop of 10–17 %) and Vertisols (a drop of 17 %) as compared to those of under grassland and forestland. 相似文献
19.
黄河三角洲内陆到潮滩土壤中碳、氮元素的梯度分布规律 总被引：1，自引：0，他引：1
黄河三角洲是我国典型的通过黄河冲积泥沙填海造陆形成的近代沉积区。区域受到黄河冲积、沉积等自然过程和农业耕种熟化等人类活动的双重影响。本研究通过在黄河三角洲地区内陆到河口海湾不同距离采集典型土壤类型剖面发生层样品,探讨土壤有机碳、总氮等生源要素的空间分布规律,为阐明我国典型海岸带地区陆源碳、氮的输送及循环特征提供基础依据。研究结果表明,黄河三角洲内陆与河口地区呈现出完全不同的土壤碳、氮分布规律。表层土壤碳、氮含量在黄河沿岸及三角洲南部均表现出由陆向海逐级递减的空间分布特征,而在黄河刁口流路和清水沟流路沿行水方向有梯度升高的趋势。内陆地区土壤碳、氮与盐分呈一定的负相关关系,表明土壤碳、氮主要受到耕作熟化过程的影响;而在河口地区两者呈显著的正相关关系（p〈0.01）,表明靠近海湾地区土壤碳、氮积累可能受到细颗粒泥沙沉积和滩涂湿地厌氧等环境影响。表层土壤碳、氮比变幅在3.6~8.6之间,说明该地区土壤有机质分解较快,不利于有机碳的积累。土壤剖面中,一些特殊发生层如红色夹黏层、黑色泥炭层对土壤碳、氮的富集具有明显的作用,其中红色夹黏层的土壤碳、氮含量接近耕层土壤。总之,黄河三角洲土壤在耕作垦殖、泥沙沉积等综合作用下形成的空间分布格局以及剖面特征发生层是影响碳、氮封存、释放和增汇等循环过程的关键驱动因素。 相似文献
20.
David Crouch 《Geoforum》2003,34(3):395-408
In this paper we explore history and heritage mobilised to do service for marginalized interests. We discuss how resources, such as, place, texts, artefacts and practice are drawn upon to forward particular political interests. Touching on recent work in non-representational theory we suggest that more attention be paid to the micro-politics of doing and link more formal action to that of ‘everyday’ practice. The examples used show how particular actors draw on history and heritage to advance their positions and how their performances reinforce claims based on alternative practices. The examples used illustrate how this involves the notion of ‘reclaiming’ historical action, historical texts and historical place. In particular how this relates to land and specifically in this paper the metaphor, representation and practice of ‘digging’. 相似文献