Patterns of frugivory,seed dispersal and predation of blue fan palms (Brahea armata) in oases of northern Baja California

Variations in spatial and temporal availability of fruits and seeds in oases are important not only for animal seeking resources, but also for palm population dynamics. We explored spatial association patterns between avian frugivores and blue fan palms in two natural palm patches of Baja California. Spatial patterns were analyzed at the individual tree and at 2 ha patches. We evaluated seed predation by vertebrates and invertebrates, and vertebrate seed dispersal around palms. Birds responded to fruit aggregation at the individual tree and the patch scales, but responses varied between patches. Palm fruit variables—the quantity and the phenological phase—and avian visits showed strong spatial aggregation and association at both scales in one patch, but not in the other. The intensities of seed predation and seed dispersal were significantly higher directly below palms than at >3 m away from them. Patches differed in the intensity of seed predation around palms and in the diversity of mammalian dispersers, but not in the intensity of seed dispersal. Blue fan palms function as important resources' focuses for a great number of animals that use palm oases as corridors, bringing seeds as they move and connecting isolated populations of palms.     

Baja California peninsula oases: An agro-biodiversity of isolation and integration

Agro-biodiversity in the desert oases of the Baja California peninsula, Mexico is a product of isolation and integration events through time and across peninsular spaces. Historic inventories of agricultural introductions provide a baseline from which to measure Mission-era crop persistence or genetic erosion in fifteen missions established during the Jesuit occupation (1697–1768). These mission-oases function as a network of interconnected sites supporting cultivated plant assemblages isolated from one another and the Mexican mainland by a desert matrix, by limited transportation infrastructure on the peninsula, and the surrounding sea. Garden surveys of perennial crop species and farmer interviews reveal that oases serve as refugia of Mission-era crop species and traditional knowledge. Isolation-connectivity analyses indicate that this agro-biodiversity disappears at the extremes: The most isolated and the fully integrated oases are unable to support heritage perennial crop species and traditional farming systems over long time scales. We describe how phases and processes of isolation and connectivity transform agro-biodiversity composition in this archipelago of peninsula oases and explore policy applications that could preserve this critical diversity and the rare and available oasis communities.     

Beginnings and early history of date palm garden cultivation in the Middle East

Despite its economic and symbolic importance in the arid regions of the Middle East little is still known about the early cultivation of the date palm (Phoenix dactylifera L.). Besides its numerous uses, this fruit tree constitutes the main species and structural element of the date palm gardens that characterize the hot deserts of the Old World. These agrosystems, perfectly adapted to the specific constraints of the environment, concentrate agricultural production in an artificial and intensively cultivated space depending on irrigation. While the first evidence of the cultivation of date palms in southern Mesopotamia dates to the 5th millennium B.C., oasis agriculture seems to have developed mainly during the early Bronze Age (from around 3000 B.C.) when this type of agrosystem can be reconstructed in different parts of the Middle East: Mesopotamia, southeastern Iran and eastern Arabia. The present paper draws together evidence from different kinds of sources (archaeobotany, texts, iconography) bearing on the early history of oasis agriculture. Questions of particular interest are the organization of past date palm gardens and their irrigation.     

Notes on Notiosorex crawfordi (coues) from two oases in the Baja California peninsula, México

Data from distribution, ecology, and stomach contents of four desert shrews, Notiosorex crawfordi (Coues), collected from a large gap in their known distribution on the Baja California peninsula, in Mexico is presented in this paper. The contents in the stomach were specimens of the order Araneae, Hymenoptera, Coleoptera, Dictioptera, and Acari, and small quantities of plant material were also found.     

Loading nutrients from oases to sea on arid watersheds NW Mexico

In arid climates, inputs of nitrogen and phosphorus in coastal waters are mainly driven by groundwater discharge, and runoff from oases near the coast. Each nutrient may increase from human activity and be a source of environmental pollution of coastal zones. We report on nutrient variability and content at five oases in Baja California Sur, their watercourses, and discharge sites to the sea during a 4 year period (2004–2007). Measurements were carried out of temperature, salinity, dissolved oxygen, nitrates, nitrites, ammonium, orthophosphates, and silicates along the oasis watercourses and adjacent coasts. Higher content of nitrogen and phosphorus was found at sites where agriculture and high populations were present. Differences on geographic localization, and rainfall rates were not an important factor on nutrient variability. Lagoons and estuaries as part of the end of the watercourses were important because these zones reduce nitrogen and phosphorus by biological activity and sediment retention, so that water quality of adjacent coast is not disturbed. The Oasis San José is affected by sewage input from a population (77 000 inhabitants) and this water body seems to be near its limit of assimilative capacity to these nutrients.     

New constraints on relative motion between the Pacific Plate and Baja California microplate (Mexico) from GPS measurements

We present a new surface velocity field for Baja California using GPS data to test the rigidity of this microplate, calculate its motion in a global reference frame, determine its relative motion with respect to the North American and the Pacific plates, and compare those results to our estimate for Pacific–North America motion. Determination of Pacific Plate motion is improved by the inclusion of four sites from the South Pacific Sea Level and Climate Monitoring Project. These analyses reveal that Baja California moves as a quasi-rigid block but at a slower rate in the same direction, as the Pacific Plate relative to North America. This is consistent with seismic activity along the western edge of Baja California (the Baja California shear zone), and may reflect resistance to motion of the eastern edge of the Pacific Plate caused by the 'big bend' of the San Andreas fault and the Transverse Ranges in southern California.     

Coincidence of abandoned settlements and climate change in the Xinjiang oases zone during the last 2000 years

The study on the relationship of abandoned settlements and climate change in the oases could provide a historical reference for understanding human responses to present and future global warming in the arid zone. A total of 554 abandoned historical settlements in Xinjiang Uygur Autonomous Region, China, were used to examine the relationship between abandoned settlements and temperature change over the past 2000 years. The analysis covered dynastic epochs from the Han Dynasty (206BC–220AD) to the Qing Dynasty (1644AD–1911AD) in the oases of Xinjiang. Greater density of settlements was found at the oases larger than 2000 km², which were more stable and less sensitive to climate change compared to smaller oases. Settlements flourished at small oases and the middle and lower reaches of rivers during warm periods and shrank back to piedmont basins and upstream alluvial fans during cold periods. These results demonstrated responses of oasis agriculture to climate change.     

中国内陆河流域绿洲发育度的综合评价

人工绿洲是干旱区人类活动主要场所,绿洲管理和生态建设体现了人类活动的积极作用;而不适当的土地开发与经济活动又形成了对绿洲生存与可持续发展的过度压力与生态负荷。科学准确地对绿洲状态进行综合评价,已成了人们正确认识绿洲并对其进行生态建设和环境保护的重要前提。针对目前我国绿洲综合评价研究的指标单一、应用区域受限等缺陷和不足,提出了可普遍用于内陆河流域绿洲评价的指标体系--基于因子分析法的“绿洲发育度”,并以河西走廊的15个绿洲为研究对象进行了案例分析。结果表明：依据发育度综合评价值可将河西走廊绿洲划分为工业绿洲、较高开发程度的农业绿洲、中度开发的农业绿洲和衰退或较低开发程度的农业绿洲4个等级,与当地实际情况完全符合;同时,还可通过因子水平上的发育度指标对各个绿洲的优势和劣势进行准确的定量表达,为绿洲管理者和政策制定者提供简明、准确的科学依据。     

中国绿洲分区及其基本类型

根据我国绿洲分布区域地理环境的差异性,地理位置和地势,大气环流与气候以及绿液演变和人类活动影响,将我国绿洲划分为三大区：东部河套平原绿洲区,西北干旱内陆绿洲区和柴达木高原绿洲区。首先,在学习、综合分析前人对绿洲的基础上,对绿洲赋予新的定义：干旱荒漠中有稳定水源,植物繁茂,生物活跃,具有一定的空间规模,且明显高出周边环境的高效生态地理景观区。最后,依据绿洲发生的水、土基本因素,将我国绿液分为四大基本类型,即沿河两岸阶地型绿洲、扇形地型绿洲、冲积平原型绿洲和三角洲型绿洲。     

Distribution and Characteristics of Nitraria sphaerocarpa nebkhas in a Gobi habitat outside an oasis in Hexi Corridor region, China

Nitraria sphaerocarpa Maxim., a typical desert plant which often appears in nebkha form, is widely distributed along the periphery of oasis in arid regions of Northwest China, and plays an important role in desertification control around oases. In this paper, the characteristics and distribution patterns of N. sphaerocarpa nebkhas were investigated in a Gobi environment outside an oasis. Results shows that about 200 N. sphaerocarpa nebkhas per hectare was recorded and total sand sediments was 25 m³/ha. Nebkhas vary in size, and the mean height (H) and horizontal composition (L) were 15 cm and 80 cm, respectively. There exists a significant linear relationship between H and L, suggesting that the investigated nebkhas are mostly in the growth stage. The numbers, height and sand deposit of nebkhas decreased with increasing distance away from the oasis. Grain-size analysis indicates that the mean grain size of sediments at the crests of nebkhas increased with increasing nebkha height. Organic C and total N concentrations were related to the mean grain size. It was concluded that N. sphaerocarpa shrubs are efficient horizontal sand traps for wind-driven sediments. A better understanding of the development of nebkha can provide information for the design of biological sand control measures around oases in arid regions.     

绿洲景观若干理论问题的探讨

本文应用近年来日益活跃的景观生态学研究成果，对绿洲的概念，基本特征，分布，景观类型，景观命名等理论问题进行了探讨。     

塔里木盆地南缘古绿洲分布与河流、冰川的关系

依据野外实地考察和考古资料对塔里木盆地南缘河流与其流域内的古绿洲分布情况进行了研究,着重探讨了历史时期以来古绿洲分布规律、迁移过程与河流、冰川特点之间的耦合关系。研究表明,盆地南缘东侧的且末、若羌地区河流及冰川规模小,数量少;其中下游形成的绿洲小,且从汉代至今都在河流出山口处分布,变化不大,而西侧的和田地区反之,河流下游的沙漠中分布着数量较多的大规模古绿洲;汉代的古绿洲多分布在冲积平原下部的沙漠中心,中部则是以唐代古绿洲遗址为主,上部沙漠边缘多为近代和现代绿洲;古绿洲迁移最大距离可达200 km左右;河流年径流量与古绿洲在沙漠分布的距离呈正相关关系。     

不同取样单元对干旱区绿洲小麦地上生物量光谱估算模型的影响

为了更好地了解小麦高光谱特征与其地上生物量的关系,采用美国ASD公司手持便携式野外光谱仪（ASD Fieldspec HandHeld）在甘肃河西绿洲进行了小麦高光谱遥感地面观测。运用单变量线性和非线性回归分析方法,以不同绿洲为取样单元,建立4种NDVI-小麦地上生物量（ANPP）的地面光谱模型。研究结果表明,各模型均达到极显著检验水平（小样区:α=0.01,n=20;大样区:α=0.01,n=34）,通过对各个模型进行误差分析,确定基于同一绿洲和不同绿洲单元构建的最优光谱模型均为指数函数模型。其中,张掖绿洲、酒泉绿洲和河西绿洲模型分别为ANPP=0.1567e12.568NDVI(R2=0.8123)、ANPP=0.4082e11.108NDVI(R2=0.8321) 和ANPP=17.255e5.4326NDVI(R2=0.7369)。基于同一绿洲（小样区）构建的小麦光谱生物量预测模型在不同绿洲之间可以通用,但不能用于河西绿洲小麦估产;河西绿洲小麦估产要借助不同绿洲小样区构建的小麦光谱生物量模型进行预测。     

LOCAL PEOPLE AND CONSERVATION IN MEXICO's EL VIZCAÍNO BIOSPHERE RESERVE*

ABSTRACT. It is increasingly clear that local participation in conservation endeavors is not only critical but also highly problematic. El VizcaÍno Biosphere Reserve in Baja California Sur, Mexico, is examined to study the difficulties involved in translating community-based conservation rhetoric into on-the-ground nature-protection efforts. This case illustrates how inhabitants of a reserve are marginalized by the very conservation process meant to engage them as key actors in promoting natural-resource protection. It also highlights recent attempts to enhance local participation in reserve endeavors through collaborative efforts among field staff, nongovernmental organizations, and area residents.     

干旱区内陆河流域生态系统类型及其整治途径——以新疆为例

干旱区内陆河流域生态系统类型 ,可按水资源的形成、转化、消耗、积蓄和排泄 ,结合地貌和植被划分为山地、水域、人工绿洲、自然绿洲和荒漠五大类型。各类型是在以荒漠为背景情况下 ,山地为基础 ,水域为主导 ,人工绿洲是核心 ,自然绿洲是屏障。流域生态系统整治途径是 :治理山区环境 ,涵养保持水源 ;合理利用水源 ,维护生态稳定 ;建设人工绿洲 ,优化生存基地 ;保护自然绿洲 ,发挥生态效益 ;防治荒漠化扩大 ,减少危害程度     

末次冰盛期以来塔里木盆地绿洲演化研究进展与问题

塔里木盆地绿洲是中亚干旱区历史时期和现代人类生产和生活的重要场所,也是古丝绸之路和现代丝绸之路经济带的重要节点。对此区域绿洲沉积记录进行研究,可以了解绿洲演化过程,从而进一步对绿洲演化的机制进行分析。由于塔里木盆地周边绿洲人类活动剧烈,导致连续完整的绿洲沉积记录较为缺乏;而且此区域环境变化敏感复杂,沉积记录存在‘同期异相’等特性,限制了对绿洲演化过程和影响机制的探讨。因此,对塔里木盆地绿洲沉积物与绿洲演化过程研究进行系统总结非常必要。通过梳理目前对绿洲和绿洲沉积物的分类与定义,认为除了地貌与沉积相,还需结合表征绿洲沉积阶段的指标体系才能更好地厘清绿洲演化过程。筛选了记录塔里木盆地末次冰盛期以来的24篇绿洲沉积序列的文献,对文献中232个绿洲沉积发育年代和其中的120个河湖相沉积发育年代数据分别进行概率密度统计。总体来看,绿洲沉积与河湖相沉积发育年龄具有较好的一致性,暗示绿洲发育与盆地内部水文过程密切相关。同时,6 ka之前,绿洲发育概率密度与古里雅冰芯δ¹⁸O记录的温度具有相同变化趋势,盆地周边高山地区冰川融水可能是绿洲发育的主控因素;6 ka之后,绿洲发育与天山鹿角湾黄土-古土壤序列记录的湿度变化较为一致,绿洲发育可能主要响应于山地降水变化。进一步对塔里木盆地不同区域绿洲发育概率与古环境演化记录进行对比,发现不同区域绿洲发育与古环境记录存在着不一致性。在未来研究中,应该对塔里木盆地各区域大范围不连续的绿洲沉积进行集成研究,构建区域绿洲演化过程和年代框架,在此基础上对控制各区域绿洲发育的因素进行深入探讨。     

河西地区绿洲NDVI的演变特征及与气候因子的关系分析

选取NOAA和NASAPathfinder AVHRR陆面资料中的1982-2000年中国区域的NDVI逐月数据,进行河西地区植被覆盖状况分析,探讨河西绿洲植被的演变规律,分析研究河西地区NDVI的年际变化特征,发现近20年来额济纳绿洲是明显退化的;临泽和民勤是明显的正值,金塔绿洲也为正值,但值较小。从时间段上来说,1982-1984年,NDVI处于相对高值段,各绿洲有所发展;1985-1989年是NDVI的低值段,绿洲退化;1990-1995是NDVI的高值段,绿洲的发展很明显;1996年开始,NDVI有所下降,绿洲有所退化。对1982-2000年河西绿洲的降水、气温、地温、及各内陆河的径流资料与河西绿洲中部临泽、民勤、金塔、额济纳旗四个绿洲的NDVI作了相关分析,研究了河西中部地区绿洲发展和气候变化及水资源的关系,发现河西中部地区绿洲NDVI与前期3、4月份的气温、降水、内陆河径流的关系较好,与5月份地气温差的相关关系较好。     

EDAPHIC LIMITATION OF A BRAZILIAN RAINFOREST PALM: THE ROLE OF ENERGY ALLOCATION AND COMPETITION FOR SUNLIGHT

Tropical forest palms are often associated with specific soil conditions, yet the ecological role of edaphic limitation in Palmae has seldom been considered. In the Atlantic Coastal Forest Biome of eastern Bahia, Brazil, the piassava palm (Attalea funifera) inhabits coastal podzolic soils but not nearby latosols. This paper examines the role of changing edaphic conditions and access to sunlight in the restriction of this species to tropical podzols.     

黑河绿洲坡面分异演化研究

对干旱区绿洲的物质和能量随坡面分异现象和规律的研究,有助于我们深刻了解不同类型绿洲形成和演化的自然背景和农业资源组合的特点,为农业生产的合理布局和农业自然资源的优化配置提供理论依据。以黑河流域绿洲为例,在综合分析影响绿洲坡面分异的气候、地质构造和地貌演化、地表水和地下水水文化学性质、土壤性状和水资源供应状况等自然地理要素基础上,将黑河绿洲划分为高位绿洲、中位绿洲和低位绿洲等不同类型。在此基础上,分析了黑河流域不同类型绿洲主要农作物气候适宜性随坡面的分异,为绿洲农业资源的优化配置提供了重要的理论依据。     

塔里木盆地南缘2000-2013年人工绿洲扩张特点

利用2000、2005、2011、2013年4期MODIS13Q1、Landsat TM/ETM+/OLI遥感影像,基于RS、GIS技术,分别提取土地利用/覆被类型信息,探讨塔里木盆地南缘人工绿洲扩张特点。结果表明:塔里木盆地南缘人工绿洲在2000-2013年不断扩张,各时段扩增来源中,天然绿洲比重不断减小,绿洲-沙漠过渡带比重逐步上升,荒漠比重快速增加。各流域人工绿洲扩张的阶段性与区域性差异明显,且扩增来源结构由于扩张的相对区位不同而异。人口增长、政策引导使人工绿洲不断扩张,并具有阶段性与区域差异性特点。人工绿洲扩张过程中,天然绿洲和绿洲-沙漠过渡带有明显退化现象,使其生态屏障功能下降,威胁到绿洲安全和经济社会的可持续发展。