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1.
Based on historical records, Jesuit missionaries were the first to introduce date palm (Phoenix dactylifera L., Arecacea) to the mission oases of the Mexican Baja California peninsula. Seedling date palms readily naturalized and have partially, and in some cases almost entirely replaced the native fan palm, Washingtonia filifera and Washingtonia robusta in the oases. These wild and introduced palms form the over-story for smaller cultivated trees, shrubs, and open gardens of mixed perennial and annual cultivars in complex agro-ecosystems. They also grow in dense stands along the oases arroyos where they may be “owned” by various oasis residents and semi- to carefully managed, or comprise wild populations beyond the periphery of the oasis settlements. These palms serve as ecological and cultural keystone species, altering oasis microclimates and providing shade for understory crops, shelter and food resources for resident and migratory fauna, and building materials and food for oasis human residents. I explore the agro-ecological role of the date palm in Baja California peninsula oases. 相似文献
2.
灌溉方式对现代绿洲影响的数值模拟 总被引：8，自引：3，他引：5
灌溉是农业发展的根本,没有灌溉就没有荒漠区农业。利用美国NCAR中尺度模式MM5V3模拟了喷灌与不同水量地灌以及没有灌溉对绿洲土壤湿度、地下径流以及感热、潜热通量的不同影响。结果表明:①地灌后地表蒸发与植被层的蒸腾更旺盛,散失的水分更多;而喷灌可以抑制地表蒸发与植被层的蒸腾,对土壤水的保持更有利。②喷灌试验要在土壤湿度达饱和以后才会形成地下径流量,而地灌试验则是土壤湿度与地下径流量同时增长。总之,喷灌方式是一种高效节水的灌溉方式,它比其它灌溉方法更有利于绿洲农业生态系统的温度整体降低,不论土壤湿度还是大气湿度都会相应增大,抑制地表土壤水分的蒸发,有利于绿洲农业维持。 相似文献
3.
渭干河-库车河三角洲绿洲50 a来农业开发及所引发的生态问题探析 总被引：6，自引：5，他引：6
从渭干河-库车河三角洲绿洲50a来农业开发与生态建设的过程看，人工绿洲耕作农业的生产力水平有较显著的提高，人工绿洲生态也得到了改善。主要表现是单位面积生产力水平提高，农田防护林体系初步建立，水利工程建设得到加强，生活能源的短缺得到改进。但从流域的绿洲农业经济发展与生态环境建设仍存在一些不协调的问题。主要是农田施肥重化肥轻有机肥，土壤肥力不高；灌区中游重灌轻排，灌排不协调，盐渍化面积有所扩大；流域下游由于缺水和人为等因素使天然绿洲的稳定性受到威胁，天然林的绿色屏障作用大为削弱等。对此必须引起足够重视，逐步加以协调，才能实现绿洲农业经济的可持续发展。 相似文献
4.
灌溉在现代绿洲维持与发展中的重要作用 总被引：16，自引：7，他引：9
灌溉是荒漠绿洲农业发展的根本,没有灌溉就没有干旱区农业。本文运用美国NCAR的非静力平衡中尺度模式MM5V3,模拟了1991年8月1日到11日张掖绿洲地表感热、潜热通量和波文比,模拟结果表明此模式可以较好地反映张掖绿洲地表能量及水汽交换状况。同时模拟了当水源被截断后,地表感热、潜热通量及波文比随时间的变化:潜热迅速下降,感热迅速上升,波文比绝对值也迅速增大。如不及时补充水,绿洲将最终退化为沙漠。模拟结果证明了:①在我国西北干旱区有水才有绿洲,无水便成沙漠,水是绿洲的生命线,灌溉是现代绿洲维持与发展的基础;②绿洲一旦因缺水而退化为沙漠,就很难恢复。 相似文献
5.
6.
M. Horrocks W. T. Baisden J. Flenley D. Feek L. González Nualart S. Haoa-Cardinali T. Edmunds Gorman 《Journal of Paleolimnology》2012,48(4):767-783
Previous paleoenvironmental records from the lake of Rano Raraku crater, Easter Island??s statue quarry, showed evidence of two major environmental changes, fluctuating lake levels and Polynesian forest clearance. There have been no reports, however, of former shorelines and it is not known if deforestation of the crater was for quarrying alone, or also for agriculture. We shed light on this by examining macrofossil casts of plants found in dryland iron pan deposits, and using combined analyses of pollen, phytoliths and starch in a lake sediment core and dryland soil profile. Casts of wetland taxa, namely Scirpus californicus and fern rhizomes, were identified in the iron pan deposits up to ~10?m above the current lake level, providing evidence of higher lake level during the last Glacial period. This height is near the level of the col on the western side of the crater, indicating that the lake was at its maximum possible elevation at the time, with overflow via the col. Microfossils of introduced Colocasia esculenta (taro), Ipomoea batatas (sweet potato), Musa (banana sp.) and possibly Lagenaria siceraria (bottle gourd) were identified in the core and soil profile, providing evidence of ancient Polynesian agriculture. Earliest evidence of gardening occurs at ~627?C513?cal BP, immediately after large-scale forest clearance. The core and soil profile were located on opposite sides of the catchment, suggesting that the crater was intensively multi-cropped and that widespread irrigated gardens co-existed with statue-quarrying activity. 相似文献
7.
Barney Warf 《Geographical review》2014,104(4):414-438
Cannabis, including hemp and its psychoactive counterpart, has a long but largely overlooked historical geography. Situating the topic within varied perspectives such as world‐systems theory, Foucauldian biopolitics, and the moral economy of drugs, this paper charts its diffusion over several millennia, noting the contingent and uneven ways in which it was enveloped within varying social and political circumstances. Following a brief theorization, it explores the plant's early uses in East and South Asia, its shift to the Middle East, and resultant popularity in the Arab world and Africa. Next, it turns to its expansion under colonialism, including deliberate cultivation by Portuguese and British authorities in the New World as part of the construction of a pacified labor force. The fifth section offers an overview of cannabis's contested history in the United States, in which a series of early 20th‐century moral panics led to its demonization; later, the drug enjoyed gradual liberalization. 相似文献
8.
透视伊拉克的地缘政治 总被引：1，自引：0，他引：1
伊拉克共和国地处亚、欧、非三大洲的结合部,是广大中东干旱缺水地区中的一块最大的绿洲,自古以来就是中东的心脏,地理位置非常重要。在近代,伊拉克发现了丰富的石油,更使之成为世界列强的争夺之地。2003年3月20日上午10时35分,在全球各国无数人的关注之下,伊拉克战争全面打响了。本文从政治地理的角度对伊拉克的位置、民族宗教与地缘政治的关系,以及未来中东地区的地缘政治结构进行了系统分析,供关心伊拉克战争的同仁参考。 相似文献
9.
三工河流域新老绿洲发育度的比较 总被引：1，自引：0，他引：1
绿洲是干旱区最重要的景观单元之一。人工绿洲是在干旱条件下经长期人类活动改造而形成的特殊景观。随着人类对绿洲水土资源开发利用程度的不断加强,绿洲呈现出不同的发展阶段。从天然绿洲到人工绿洲,是人类适应和改造干旱区自然环境的历程。在这一人地相互作用的过程中,绿洲显示出明显的发育演化特征。从多学科综合的角度,提出绿洲发育度的概念,并从灌溉体系的建设状况、水资源的利用水平、植被与生态建设、农业发展程度、社会经济水平和绿洲景观结构等7个方面提出了绿洲发育度的评价指标体系,以天山北坡2个人工绿洲为例,从空间上定量比较2个绿洲的发育程度,其中阜康市绿洲发育度高于222团绿洲(阜北农场)。 相似文献
10.
The purpose of this paper is to bring into light the landscape change and natural resources management in the Moroccan Middle
Atlas across centuries. The pastoral way of life prevailed for many centuries. However, following the results of this research,
evidence of important socioeconomic changes and resources use is found. Ancient agricultural activities, as well as the exploitation
of the forest and even mineral resources have been growing activities over time. The survey shows that the agricultural activity
has existed for several centuries as indicated by terraces and encrusted travertine channels used for irrigation. The landscapes
and the ways of resources use are therefore in continuous change. The increasing needs in water and agriculture for demographic
and climatic reasons (the dry periods in summer or periodic droughts) generated because of intensive over-exploitation of
resources. The vegetation degraded facing human pressure (the pastoral activities, the coal of wood making, the lime manufacturing,
etc.). Field observations show that irrigation has been used in this domain, for several centuries. Travertine channels, encrusted
in the valleys of Jnane Mas and Arougou, illustrate these ancient uses of water resources for agriculture irrigation. 相似文献
11.
水分胁迫对绿洲影响的数值模拟 总被引：7，自引：0，他引：7
运用耦合了包含土壤-植被-水文参数化陆面过程的非静力平衡中尺度大气模式MM5,将水平分辨率提高到1km,通过数值模拟的方式,分别从地气间水热交换、对绿洲小气候影响、土壤湿度变化以及径流量的角度,研究了2002年7月下旬我国西北干旱区绿洲环境在不同水量滴灌条件下的变化,从理论上找到了较适宜绿洲小气候维持的滴灌水量。结果表明：1、绿洲下垫面为农田时,从土壤保湿和绿洲小气候维持角度考虑,500m^3／hm^2／10天的滴灌水量对7月下旬黑河流域中游绿洲是一个比较合适的灌溉量。2、500m^3/hm^2／10天的灌溉水量仅为同期大水漫灌定额下限的一半,上限的1／3,间接证明了滴灌是一种高效节水的灌溉方式,可以为干旱区节约大量水资源。 相似文献
12.
黑河调水对下游生态环境恢复效果的卫星遥感监测分析 总被引：27，自引：7，他引：20
利用2002年7月至2003年9月EOS/MODIS资料, 计算了黑河尾闾湖——东居延海重新出现后水域面积并分析其变化特征; 通过对2002和2003年6~8月黑河下游额济纳旗和古日乃绿洲植被指数的对比分析, 了解黑河调水对下游植被恢复的效果。结果表明: 东居延海重新出现后仍为季节性湖泊, 其面积2002年初冬最大, 2003年春季迅速减小并于6月6日干涸。随着中游地区再次向下游调水, 2003年8月中旬东居延海再次出现, 干涸时间为70d, 较前些年大大缩短。东居延海再现后对位于河道周围的额济纳旗绿洲植被恢复效果比较明显, 对远离河道的古日乃绿洲植被生长影响不显著。 相似文献
13.
Douglas Deur 《The Professional geographer》2002,54(2):140-157
The indigenous peoples of the Northwest Coast of North America are widely believed to have been true “hunter‐fisher‐gatherers,” lacking plant cultivation of any kind. This depiction of the region's indigenous inhabitants emerged within early colonial accounts and was perpetuated within the literatures of geography, anthropology, and archaeology. Still, there is ample evidence of plant cultivation available from archival, archaeological, and ethnographic sources. In particular, the peoples of coastal British Columbia created large gardens of edible estuarine plants, using sophisticated indigenous technologies. The oversight of these practices in written representations of the region reveals consistent patterns of bias, emanating from the agendas of colonial agents and early academics alike. In turn, this bias has undermined aboriginal traditions of cultivation and indigenous land claims. 相似文献
14.
In Malaysia, the main land change process is the establishment of oil palm plantations on logged‐over forests and areas used for shifting cultivation, which is the traditional farming system. While standing carbon stocks of old‐growth forest have been the focus of many studies, this is less the case for Malaysian fallow systems and oil palm plantations. Here, we collate and analyse Malaysian datasets on total carbon stocks for both above‐ and below‐ground biomass. We review the current knowledge on standing carbon stocks of 1) different forest ecosystems, 2) areas subject to shifting cultivation (fallow forests) and 3) oil palm plantations. The forest ecosystems are classified by successional stage and edaphic conditions and represent samples along a forest succession continuum spanning pioneer species in shifting cultivation fallows to climax vegetation in old‐growth forests. Total carbon stocks in tropical forests range from 4 to 384 Mg C/ha, significantly wider than the range of total carbon stocks of oil palm plantations, 2 to 60 Mg C/ha. Conversion of old‐growth forest areas to oil palm plantations leads to substantial reduction in carbon storage, while conversion of forest fallows to oil palm plantations may sustain or even increase the standing carbon stock. 相似文献
15.
利用滴灌盆栽试验,研究蕾期和花铃期不同施N水平的条件下,滴灌棉花ABA浓度与土层20 cm田间持水率之间的响应特征,结果表明:在蕾期不同处理纯N分别为N2、N4、N6 g/盆的条件下,滴灌棉花ABA含量与土层20 cm田间持水率之间的相关性系数(r)的分别为-0.946、-0.917、-0.966, T检验显著水平P为0.015、0.029、0.007;模型拟合决定系数(R2)分别为0.977、0.852、0.934;花铃期,滴灌棉花ABA含量与土层20 cm田间持水率之间的相关性系数(r)的分别为-0.788、-0.959、-0.861;模型拟合决定系数(R2)分别为0.737、0.937、0.872;因而,蕾期盆栽滴灌棉花在纯N分别为N2、N4、N6 g/盆的条件下,滴灌棉花ABA含量与土层20 cm田间持水率之间的相关性为负相关, N6 g/盆的相关性达到显著水平, N6 g/盆处理拟合决定系数(R2)达到极显著水平,其模型为对数。花铃期滴灌棉花ABA含量与土层20 cm田间持水率之间的相关性为负相关, N4 g/盆的相关性达到极显著水平,模型拟合决定系数(R2) N4 g/盆达到极显著水平其模型为指数函数。本文研究的回归模型很好地描述了滴灌棉花腾发量及需水特性,为内陆干旱区绿洲农业滴灌棉花耗水量的估算提供了新计算方法和科学依据。 相似文献
16.
《The Professional geographer》2013,65(2):140-157
The indigenous peoples of the Northwest Coast of North America are widely believed to have been true “hunter-fisher-gatherers,” lacking plant cultivation of any kind. This depiction of the region's indigenous inhabitants emerged within early colonial accounts and was perpetuated within the literatures of geography, anthropology, and archaeology. Still, there is ample evidence of plant cultivation available from archival, archaeological, and ethnographic sources. In particular, the peoples of coastal British Columbia created large gardens of edible estuarine plants, using sophisticated indigenous technologies. The oversight of these practices in written representations of the region reveals consistent patterns of bias, emanating from the agendas of colonial agents and early academics alike. In turn, this bias has undermined aboriginal traditions of cultivation and indigenous land claims. 相似文献
17.
三工河流域绿洲土地利用对土壤特性的影响 总被引：2，自引：1，他引：1
Understanding the effect of human activities on the soil environment is fundamental to understanding global change and sustainable development. In the process of transformation of tropical rain forests and semiarid grasslands to farmlands, land degradation usually occurs. But the transformation of arid desert landscape to oasis is found to have quite different consequences. Taking an alluvial plain oasis in the north piedmont of the Tianshan Mountains as a case study, we investigate oasis soil properties related to different land-use systems during the transformation of arid desert to oases. Selected land-use systems con- sisted of an annual crop field less than 3 years old, annual crop field 3-6 years old, annual crop field more than 6 years old, perennial crop field less than 4 years old, perennial crop field of 4-6 years old, perennial crop field more than 6 years old, abandoned farmland more than 3 years old, woodland field more than 6 years old, ecological forestation field, natural shrubbery field, desert grass land, and saline or alkaline field. Different land-use systems affect significantly the distribution of sand, silt and clay. Sand content in oasis soil tends to decrease with cultivation years but silt and clay contents tend to be increased in the oasis soils. Soil fertility is higher in the land-use systems under strong human disturbance than under weak human disturbance. Oasis soil nutrients also tend to increase with cultivation years. Soils have a significantly lower salinity in the land-use systems under strong human disturbance than under weak human disturbance. Soil organic matter and nutrients of the annual and perennial crop systems in the oasis tend to increase with cultivation time with the oasis soil acting as a carbon sink. These results show that soils are not degraded and the soil quality is gradually improved under rational land use and scientific management patterns, including uniform exploitation of land resources, effective irrigation systems, sound drainage systems, balanced ferti 相似文献
18.
黑河流域水资源承载力分析计算与对策 总被引：84，自引：17，他引：67
根据干旱区水资源开发利用阶段可用水资源的计算方法和内陆河流域社会经济发展及其需水预测,分析计算了黑河流域中游地区的水资源承载力。结果表明,当完成水资源开发利用第二阶段,可用水资源在首先保证未来50 a内流域中游地区人口、环境和工业等部门发展的需水后,农业灌溉用水的总量将还有所增加,水资源不会成为社会经济发展的制约因素,可以使绿洲和农业走可持续发展道路。但东干流中游张掖盆地,因要在下世纪初完成分水指标,在下世纪的前20 a农业灌溉用水有缺口,但只要加大农业节水力度,在此期间提前完成农业节水目标的60%,就能顺利渡过今后20 a的社会经济快速发展时期。如果在2050年能按计划完成流域社会经济发展的预测目标,则届时流域人均国内生产总值将超过一万美元,可以达到世界中等发达国家的水平。 相似文献
19.
This study reviews 17 published Neogene pollen records with independent age control to provide a better understanding of the vegetation evolution and climate change in China, especially of the past shifts of the arid–semiarid steppe. During the late Early Miocene to early Middle-Miocene period, most of East and South China was covered by woodland vegetation (e.g., Quercus, Carya, Alnus, and Juglans) while Northwest China was mainly steppe (e.g., Artemisia), generally indicating a warm and humid climate influenced by a strong East-Asian summer monsoon. Since the Early Miocene the vegetation boundary between both regions has moved through time as the climate has changed. During the late Middle to Late Miocene cooling, herbs and shrubs increased significantly in the vast region north to the Yangtze River of South China and major woodland vegetation retreated to south of the Yangtze River. In the context of this cooling, a drier season probably became established north to the Yangtze River, as is evident from the late Middle Miocene to Pliocene compiled palynoflora data. Nevertheless, a little resumption for woodland vegetation occurred during the Early Pliocene in North China, presumably corresponding to global climate amelioration. Thus, the stepwise declining pattern of modern vegetation distribution from southeast to northwest in China can be traced back to at least the late Middle Miocene. In the meanwhile, the Neogene vegetation and its inferred climate history in China indicated a general declining trend of East-Asian summer monsoon. 相似文献
20.
民勤盆地水资源可持续利用对策——2000年民勤水资源利用调查 总被引：15，自引：1，他引：14
水资源短缺和生态环境恶化已成为民勤绿洲面临的严重问题。本文在分析民勤盆地水资源特点及开发利用中存在的问题的基础上,本着水资源可持续利用的原则,从加强水资源保护与管理,发展节水农业生产体系,以及开源调水和减少人口等方面,提出了水资源可持续利用途径与措施。 相似文献