Long-term growth rates of cirio (Fouquieria columnaris), a giant succulent of the Sonoran Desert in Baja California

Factors affecting temporal and spatial variations of growth were studied in cirio, a succulent often surpassing 10 m in height. Measurements were obtained for intervals of 3–93 years at 14 sites in Baja California. Height tended to be asymptotic but total plant length (i.e. including all succulent stems) increased in linear relation to trunk diameter. Growth in length showed an overall average of 4·6 cm year⁻¹ but ranged from 0·3–16·7 cm year⁻¹ (annualized from data for intervals >34 year). Most of the variation was among individuals, but some differences between sites were also significant. Growth was clearly and strongly related to size only for individuals less than 1 m in height. Repeated measures on the same individuals showed that the autocorrelation of growth was about 0·8 between intervals of 3 or more years. Differences among individuals were related to physiographic position, the presence of caliche and the density of neighboring plants, which together explained 43% of the variation. We discuss the implications of these results for age estimates, indicators of site quality and studies of similar plants.     

Who Is “Forest‐Dependent”? Capturing Local Variation in Forest‐Product Sale,Eastern Honduras

How researchers describe groups living within or near the world's tropical rain forests has important implications for how and why these groups are targeted for assistance by conservation and development organizations. This article explores how data about market behavior can be used to assess one aspect of forest peoples’ livelihoods: their “dependence” on forest resources as a source of market income. With the intent of revealing the importance of methodology to how we describe forest peoples’ livelihoods, I draw from a multiyear survey of market activity among the Tawahka Sumu of Honduras and distinguish nested measures of the Tawahkas’ engagement in forest‐product sale. Results indicate that whether or not the Tawahka —or any forest group — can be considered financially “dependent” on forest resources depends on the spatial and temporal scales at which data are aggregated. As a group, the Tawahka earned 18 percent of total market income from forest‐product sale, but their group profile masked a high degree of heterogeneity at the village and household level. Similarly, multiyear data indicated that while group‐level generalizations adhere from year to year, they belie considerable change in households’ market behavior across years. I discuss three ways in which the findings are relevant to the theory and practice of conservation and development in the humid tropics. I emphasize the importance of spatial scale in interventions, how market‐oriented conservation schemes can benefit from a broader conceptualization of the economic context in which forest‐product sale occurs, and how longitudinal analysis can reveal the dynamism of forest peoples’ livelihoods.     

Farlie-Gumbel-Morgenstern bivariate densities: Are they applicable in hydrology?

Certain bivariate densities constructed from marginals have recently been suggested as models of hydrologic variates such as rainfall intensity and depth. It is pointed out that (i) these densities belong to the families of the Farlie-Gumbel-Morgenstern densities and the Farlie polynomial densities, which have been extensively studied in the statistical literature, and that (ii) these densities have a limited potential applicability in hydrology since they can model only weakly associated variates, whose product-moment correlationR is within the range |R|1/3, under the first family of densities, and |R|1/2 under the second family.     

Impact of difference accuracy on computational properties of vertical grids for a nonhydrostatic model

Starting from nonhydrostatic Boussinesq approximation equations, a general method is introduced to deduce the dispersion relationships. A comparative investigation is performed on inertia-gravity wave with horizontal lengths of 100, 10 and 1 km. These are examined using the second-order central difference scheme and the fourth-order compact difference scheme on vertical grids that are currently available from the perspectives of frequency, horizontal and vertical component of group velocity. These findings are compared to analytical solutions. The obtained results suggest that whether for the second-order central difference scheme or for the fourth-order compact difference scheme, Charny–Phillips and Lorenz (L) grids are suitable for studying waves at the above-mentioned horizontal scales; the Lorenz time-staggered and Charny–Phillips time staggered (CPTS) grids are applicable only to the horizontal scales of less than 10 km, and N grid (unstaggered grid) is unsuitable for simulating waves at any horizontal scale. Furthermore, by using fourth-order compact difference scheme with higher difference precision, the errors of frequency and group velocity in horizontal and vertical directions produced on all vertical grids in describing the waves with horizontal lengths of 1, 10 and 100 km cannot inevitably be decreased. So in developing a numerical model, the higher-order finite difference scheme, like fourth-order compact difference scheme, should be avoided as much as possible, typically on L and CPTS grids, since it will not only take many efforts to design program but also make the calculated group velocity in horizontal and vertical directions even worse in accuracy.     

高温高压及干燥条件下斜长石和辉石断层泥的摩擦滑动研究

岩石摩擦滑动的力学行为能够很好地用速率和状态依赖性摩擦本构关系来描述。在速率和状态依赖性本构关系中,速度依赖性参数a-b是控制摩擦滑动稳定性的重要参数。且a-b<0是断层上不稳定滑动成核的必要条件。为了进一步研究控制摩擦滑动的矿物成分因素,在已有辉长岩摩擦滑动实验结果的基础上,对辉长岩中主要矿物(斜长石和辉石)在不同加载条件下进行了3个系列的摩擦滑动实验研究。通过对实验结果的分析得到如下结论:(1)斜长石断层泥在实验温度范围内(<617℃)显示速度强化,且在大于450℃的高温区其速度依赖性参数a-b随温度的增大而增加。辉石断层泥的实验显示其有利于速度弱化滑动行为的出现,是造成辉长岩在615℃出现速度弱化的原因。(2)斜长石与辉石断层泥的摩擦强度都没有随温度的增加而显著变化。辉长岩断层泥的摩擦强度(1.83mm滑动位移处的值)为斜长石与辉石断层泥摩擦强度按体积百分比加权的平均值(摩擦系数精确到2位有效数字一致)。这一结果表明,辉长岩断层泥的应力支承结构可以抽象为一种双组分并列单元模型。(3)尽管前人研究结果表明石英控制了花岗岩的摩擦特性,但是某种主要矿物对岩石整体摩擦滑动性质的控制作用并不具有普适性。对于中性岩、基性岩而言,不能以一种主要矿物(如斜长石等)来判断岩石整体的摩擦滑动稳定性,否则会导致错误结论。     

环境规制对西部地区水资源利用效率的影响研究——基于产业部门和资源依赖度异质性视角

以中国西部地区12个省（自治区、直辖市）为研究对象,采用含有非期望产出的SBM-Windows模型测算了2000—2018年中国西部地区整体和不同产业部门的水资源利用效率,并在此基础上实证分析了环境规制对西部地区水资源利用效率的影响。研究表明：① 在维持现有技术水平不变的前提下,西部地区整体水资源利用效率仍有33.89%的改进潜力。② 样本期内西部地区的水资源利用效率呈现出先上升后下降的趋势。区域间、产业部门间水资源利用效率存在明显的差异性,具体表现为西南地区的水资源利用效率明显高于西北地区,工业部门的水资源利用效率高于农业部门。③ 环境规制抑制了西部地区水资源利用效率的提升。从产业部门和资源依赖程度差异性的角度来看,环境规制对工业部门水资源利用效率的提升具有不利影响,且对高资源依赖度地区水资源利用效率的提升具有显著的负向影响。     

“大分流”的隐喻：中国与西欧优势手工业发展逻辑再审视（7—14世纪）

“大分流”相关学说异彩纷呈、数家争鸣的背后,实质均是通过构建自身话语体系对“西方中心论”的质疑和挑战。从历史实践看,工业革命始终是中西方经济发展的分水岭,而手工业作为工业革命的先声,均曾在中西方历史上大放异彩。7—14世纪中国和西欧由于农业资源禀赋的差异,形成了各自的优势手工行业——丝织业和呢绒业。就发展逻辑而言,中西方均展现出分工不断细化（由行业内分工向劳动分工发展）、产品市场关联增强的特点,但中国主要是官府需求推动并存在于官营手工工场,西欧则是由市场发展分化而来且广泛分布于城市及郊区作坊工场;中国受“施坚雅模式”层级市场影响,丝织产地之间缺乏竞争意识,西欧面对共同的区域或海外市场形成佛兰德斯、意大利和英格兰相互竞争的呢绒产业格局。分工层次和产地竞争的路径依赖殊异明显,隐喻了工业革命后中西方经济发展的“大分流”。     

Human population distribution modelling at regional level using very high resolution satellite imagery

Modelling the distribution of human population based on satellite-derived information has become an important field of research, providing valuable input e.g. for human impact assessments related to the management of threatened ecosystems. However, few regional-scale studies have been conducted in developing countries, where detailed land cover data is usually absent, and the potential of very high resolution (VHR) satellite imagery in this context has not been explored yet. This study uses results obtained through object-based image analysis (OBIA) of QuickBird imagery for a subset of a highly populated rural area in western Kenya. Functions are established that approximate frequency distributions of QuickBird-derived locations of houses in relation to five factors. These factors are known to impact settlement patterns and data is available for the entire study area. Based on an overall probability coefficient (weight) calculated from the single functions, human population is redistributed at the smallest administrative level available (version A). In addition, the problem of artefacts remaining at administrative boundaries is addressed by combining the approach with the pycnophylactic smoothing algorithm (Tobler, 1979) (version B). The results show distinct patterns of population distribution, with particular influence of rivers/streams and slope, while version B in addition is free of boundary artefacts. Despite some limitations compared to models based on detailed land cover data (e.g. the ability of capturing abrupt changes in population density), a visual and numerical evaluation of the results shows that using houses as classified from VHR imagery for a study area subset works well for redistributing human population at the regional level. This approach might be suitable to be applied also in other regions of e.g. sub-Saharan Africa.     

基于抛物线密度模型的频率域三维界面反演及其在川滇地区的应用

密度界面反演作为了解地球内部结构的一种重要方法,长期以来都是重力学研究的主要内容.本文结合抛物线密度模型及频率域算法的优点,将抛物线密度函数应用于Parker-Oldenburg算法,经过理论推导得到了抛物线密度模型的频率域公式,从而建立了基于抛物线密度模型的三维密度界面重力异常正反演的算法和流程.理论模型数据试验表明本方法快速、有效,适用于大多数浅部比深部增加更快的实际地壳密度.研究中还利用该方法对川滇地区重力异常进行了反演,获得了该区的莫霍面深度分布,并与接收函数研究结果进行对比分析,进一步验证了本文方法的正确性和有效性.     

最小曲率位场分离方法研究

位场分离是位场数据处理和解释中的重点和难点之一.本文给出了单步长非原位和原位两种最小曲率位场分离差分迭代格式,并利用Fourier频谱分析理论研究了这两种迭代格式的收敛性.通过研究表明,单步长非原位迭代格式不收敛,只有单步长原位迭代格式收敛,但单步长原位迭代格式受迭代方向选择的影响,随着迭代次数的增大其影响逐渐消失.根据单步长非原位迭代格式的频谱特点,提出了叠加步长非原位和原位迭代格式,同样利用Fourier频谱分析理论研究了叠加步长非原位和原位迭代格式的收敛性.通过研究认为,一维叠加步长非原位迭代格式收敛,但二维叠加步长非原位迭代格式不收敛;不论是一维或二维,其原位迭代格式均收敛.进一步的理论研究表明,非原位迭代格式的频率响应是一个实偶函数,而原位迭代格式的频率响应是一个复函数;单步长迭代格式的频率响应具有一定的周期性,而叠加步长迭代格式的频率响应无周期性特征;叠加步长迭代格式比单步长迭代格式的收敛性好.