基于概念设计的长短桩复合地基典型工程应用模式          下载免费PDF全文

郭密文  隋旺华  闫德刚 《水文地质工程地质》2010,37(3):92-96

本文从长短桩复合地基各组成部分的功能角度,阐述了长桩、短桩、褥垫层的作用机理,提出长短桩复合地基概念设计应遵循的设计原则。应用概念设计思想,建立了长短桩复合地基的五种典型工程应用模式,并在各典型模式的分析说明中,提出设计与施工参数的选用建议。通过在北京某工程的实际应用,显示长短桩复合地基的典型工程应用模式具有较好的实用性。  相似文献   

喀斯特适生植物固碳增汇策略   总被引：5，自引：1，他引：4  

吴沿友 《中国岩溶》2011,30(4):461-465

通过分析喀斯特地区的土壤化学性质,明确了喀斯特地区植物的固碳增汇的限制因素为岩溶干旱、低营养、高pH、高重碳酸盐等。通过对喀斯特适生植物和非适生植物的无机碳源、氮源的利用以及对低营养的响应差异分析,总结出了喀斯特适生植物交替、高效利用碳酸氢根离子作碳源的开源固碳增汇策略,以较低的营养成本获取较高的光合固碳能力的低成本倍增固碳增汇策略,以及掠夺式吸收限制性的铵态氮和补偿式吸收硝态氮来实现固碳增汇作用的以氮增汇策略等;提出了喀斯特适生植物固碳增汇能力的利用途径,可最大限度挖掘出喀斯特地区植物的固碳增汇潜能。   相似文献   

An Ex Situ Salinity Restoration Assessment Using Legume,Saltbush, and Grass in Australian Soil          下载免费PDF全文

Mohammad S. I. Bhuiyan  Anantanarayanan Raman  Dennis Hodgkins  David Mitchell  Helen Nicol 《洁净——土壤、空气、水》2016,44(7):840-848

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Saguaro Distribution under Nurse Plants in Arizona's Sonoran Desert: Directional and Microclimate Influences*     

《The Professional geographer》2013,65(4):505-512

Abstract

The saguaro cactus, an icon of the American southwestern desert, defines the extent of the Sonoran Desert through portions of its range. Saguaros rely upon nurse plants for establishment and survival in the harsh temperature and moisture regime of the desert. Freezing temperatures limit the range of the saguaro to the north in Arizona. However, nurse plants extend the range of saguaros by providing more moderate conditions beneath their canopies. This study focuses on precisely these small, highly localized temperature variations, which, we suggest, are linked to regional-scale patterns of distribution of the species, particularly in marginal, cold-limited locales.

We sampled 291 saguaros over thirty populations in Arizona, in the northern portion of their range. Saguaros establish under the south side of their nurse's canopy in the coldest parts of their range more often than expected, while a significant distributional bias is not observed in those in warmer, more moderate plots. To further investigate air temperature as a possible factor in the directional bias of saguaro establishment, we collected microclimate data under the north and south sides of the canopies of two common nurse plants, Cercidium microphyllum (a tree) and Ambrosia deltoidea (a shrub) in Phoenix, Arizona. South sides of nurses have significantly higher minimum temperatures than do the north sides. Survivorship in the coldest areas appears to be greatest under the south side of a nurse's canopy, where warmer wintertime microclimatic conditions occur. We suggest that within-canopy microclimatic variability under a single nurse plant may be reflected in regional distributional and in the survivorship patterns of saguaros throughout Arizona.  相似文献   

Trading in the dark – The medicinal plants production network in Uttarakhand     

Tim Pauls  Martin Franz 《Singapore journal of tropical geography》2013,34(2):229-243

Medicinal plant cultivation and gathering can play a vital role in the course of livelihood diversification for the marginalized population living in remote areas. However, this requires an integration of the respective production networks that allows the producers a fair and reliable income and does not endanger rare plant species. This paper analyses the situation within the Indian state of Uttarakhand, and identifies structures and entities hindering medical plant cultivation and its potentials. Based on the broad network understanding of the Global Production Network approach, the case study focuses on the middlemen and their hidden embeddedness. It shows how governmental organizations and in particular non‐governmental organizations and farmers' institutions can help to overcome clandestine structures of illegal trade and contribute towards a redesign of the medicinal plant network in a more equitable and transparent way.  相似文献   

Ornamental plants and the production of nature(s) in the Spanish real estate boom and bust: the case of Alicante     

María Hernandez  Alfredo Morales 《Urban geography》2013,34(1):71-85

The Spanish real estate boom and bust of the 2000s caused immense economic, social, and environmental changes across the country. Massive urbanization, however, does not necessarily entail the end of nature and natural processes, instead marking a radical transformation of environments and societies. Through a political ecology approach, we analyze how ornamental species have become a fundamental part of new natures induced by urbanization in the Spanish province of Alicante. We connect the economic and ecological characteristics of ornamental plants like the palm tree to urbanization and real estate trends in Alicante. Our evidence indicates that, in Alicante, economic recession and environmental crises (manifested in the pests affecting palm trees) have mutually reinforced one other, creating a new geography of ecological desolation in many areas.  相似文献   

中国北方四类典型下垫面能量分配特征及其环境影响因子研究   总被引：1，自引：0，他引：1  

任雪塬  张强  岳平  杨金虎  闫昕旸 《高原气象》2021,40(1):109-122

中国北方疆域辽阔,多种植被类型交错分布,陆面过程较为复杂。研究该区域地表能量平衡及分配过程,有助于进一步了解其生态系统的生产力及气候变化。本文使用"中国北方协同观测实验"观测资料,选取中国北方四种植被类型——高寒草甸、荒漠草地、玉米农田及半干旱草地,在深入认识地表能量分配特征的基础上,讨论了环境因子对能量分配的影响。结果表明,上述四类典型下垫面能量闭合度在71%~91%,其中半干旱草地最大,玉米农田最小。从各能量分量与净辐射的比率来看,荒漠草地、半干旱草地净辐射主要通过感热形式加热大气,感热通量占净辐射的百分比分别为29%和36%;高寒草甸、玉米农田潜热通量占主导地位,其值分别占净辐射的42%和37%。影响各下垫面水热综合参数Bowen比的气象因子中,半干旱草地受地-气温差(R2=0.64)和饱和水汽压差(R2=0.56)的影响;玉米农田则主要受地-气温差(R2=0.52)的影响;荒漠草地地-气温差(R2=0.37)和平均风速(R2=0.23)是其主要影响因子。Bowen比与NDVI之间存在显著的指数关系(R2=0.74),且随NDVI的增大而减小。  相似文献   

A SIMPLE SOIL MOISTURE INDEX TO FORECAST CROP YIELDS     

Scott A. Isard  Mark R. Welford  Steven E. Hollinger 《自然地理学》2013,34(6):524-538

Neutron probe soil moisture measurements obtained biweekly during the growing season between 1982 and 1991 from multiple depths under grass-covered plots at 17 Illinois Climate Network sites are used to forecast crop yields. A Soil Moisture Index (SMIX) that combines the effect of intensity, duration, and timing of drought or excessively wet conditions was computed by integrating the quantity of available soil moisture throughout the rooting zone over the growing season. Relationships between the SMIX values and crop yields are evaluated at county, regional, and statewide scales. Coefficients of determination (r ²) for relationships between the SMIX values and maize, soybeans, and hay yields at the statewide level are 0.88, 0.74, and 0.81, respectively, when the period of integration is terminated at the end of the growing season. This new soil index can be employed to forecast yields as early as 12 weeks before harvest for the state of Illinois. However, predictions with RMSE ≤ 10% of the mean yield can be achieved only for SMIX integration periods ending 5, 9, and 6 weeks before harvest for maize, soybeans, and hay, respectively. Nomograms are presented for using the relationships between the SMIX values and crop yields to forecast Illinois's major crops well before harvest.  相似文献   

西藏高原典型草地地上生物量遥感估算   总被引：3，自引：0，他引：3  

除多  德吉央宗  姬秋梅  唐红 《国土资源遥感》2013,25(3)

准确估算草地地上生物量对合理规划区域畜牧业、评估草地植被的生态效益有重要意义.利用每月两次的野外调查资料和对应的MODIS植被指数,以GIS空间数据处理技术和多元统计分析方法等为手段,建立了西藏高寒草甸、高寒草原和温性草原3个典型草地类型的地上生物量遥感估算模型和方法.结果表明:MODIS植被指数更适合于高寒草甸和高寒草原的地上生物量估算,对于高寒草甸,最佳估算模型是基于归一化植被指数(normalized difference vegetation index,NDVI)的三次多项式,其相关系数为0.82;对高寒草原,则是基于增强型植被指数(enhanced vegetation index,EVI)的三次多项式,相关系数达0.83;由于温性草原存在很强的空间异质性,估算效果较其他2个草地类型差.MODIS植被指数对草地生长期鲜草生物量的估算和模拟效果要优于总地上生物量.在生长期,高寒草甸和高寒草原的鲜草生物量与植被指数之间的相关系数都大于0.8,最高达0.92;对温性草原,两者的相关系数也均大于0.67,其中,NDVI是高寒草甸和温性草原鲜草生物量估算的最佳植被指数,对高寒草原则是EVI.对同一草地类型,由于地上生物量差异较小,使得相比其他模型,线性或多项式回归模型更适合于西藏高原草地地上生物量的估算.  相似文献   

运用放射性水化学方法寻找隐伏铀矿体     

辛至秀 《国外铀金地质》2012,(2):92-98

着重介绍了放射性水化学方法寻找隐伏铀矿的过程：即,从找到放射性水化学异常点到放射性水化学异常晕,到初步评价和工程揭露。以放射性水化学找矿2个成果为例,说明放射性水化学方法是寻找隐伏铀矿的有效方法之一。  相似文献