Earth pillar formation on the Mountain Pine Ridge,Belize

The roadcuts of Belize's Mountain Pine Ridge feature numerous coarsely textured earth pillars less than 10 cm in height. Preferential impregnation of iron occurs over a buried pebble resulting in a dripline. The higher concentration of iron along the buried pebble's dripline is later oxidized and exposed to the surface by rainsplash erosion. For slopes greater than five degrees, the intensity of sheetwash erosion is great enough to remove pillars. Earth pillar genesis thus seems a function of laterization, slope angle, and sheetwash intensity.     

气候变化对我国红松林的影响

在对红松适生范围、生态习性等广泛深入调查分析基础上,依据环境因子对树木生长影响的作用规律,首先推出一个能反映红松年生长量与水热因子间关系的W-T模式,进而分析了各种可能的气候变化对红松生长量与分布的影响。结果表明,气温升高,无论降水增减,都将使红松适生范围与生长量大幅度减少。但在可预见的气候变化范围内,红松不会退出我国的东部山地。     

松毛虫危害的光谱特征与虫害早期探测模式

根据生态学特征，本文将松毛虫危害的针叶样品分为５个等级，对其反射光谱和叶绿素含量进行了测量分析。结果表明，随受害程度加重，叶绿素含量降低，５５０ｎｍ处的反射率、近红外肩反射率与红光最低反射率之差及红界一阶导数谱最大值均呈下降趋势，６３０ｎｍ处反射率呈上升趋势，红界光谱蓝移、叶绿素反射峰红移明显。应用逐步判别分析法对比分析证实了细分光谱特征参量比绿、红、近红外三波段反射率参量有更强的判别分类能力，这就为用细分光谱特征参量早期遥感探测松毛虫害提供了判别模式。     

大别山地区黄山松和油松树轮宽度的气候意义

本文基于2010年采自大别山地区黄山松、油松树轮资料分别建立了树轮宽度标准年表,利用相关函数检验了年表与附近的麻城气象站1959-2009年月平均最高气温、月平均气温、月平均最低气温和月降水量之间关系,旨在探讨黄山松、油松树轮宽度的气候意义。研究结果显示,平均敏感度、标准差、信噪比等统计量黄山松年表均高于油松年表,表明黄山松年表较油松年表包含更多的气候信息,具有更高的树轮气候学研究价值。黄山松径向生长主要受当年2-7月平均气温限制,任何月份及月份组合降水量对黄山松径向生长的限制作用均不显著;油松径向生长主要受当年5-6月降水总量限制,任何月份及月份组合气温对油松径向生长的限制作用均不显著。研究表明,在中国亚热带暖湿地区,气候要素的年际变化亦可对部分树种径向生长具有较强的限制作用,树木年轮宽度的变化对气候具有指示意义。研究结果将进一步弥补中国亚热带暖湿地区树轮宽度年表的不足,为树轮气候重建研究提供参考和依据。     

Phytolith assemblages as a promising tool for reconstructing Mediterranean Holocene vegetation

The reliability of phytolith assemblage analysis for characterizing Mediterranean vegetation is investigated in this study. Phytolith assemblages are extracted from modern and buried Holocene soils from the middle Rhône valley (France). The relation between modern phytolith assemblages and the surrounding vegetation, as well as between fossil assemblages and contemporaneous vegetation, already reconstructed through other proxies, is discussed. We demonstrate that the main northwestern Mediterranean biomes are well distinguished by soil phytolith assemblage analysis. In particular, the density of pine and nonconiferous trees (densities expressed relatively to the grass cover) and the overall degree of opening of the vegetation appear well recorded by three phytolith indexes. North Mediterranean vegetation changes during the Holocene period, mainly tree line shifts, pine wood development and deforestation are poorly documented, due to the scarcity of proxy-preserving sites. Phytolith assemblage analysis of soils, buried soils, and sediments appears to be a promising technique to fill this gap.     

Application of a statistical water-table model reveals connections between dunes and vegetation at Doñana

We present a simple statistical model of the water-table fluctuations based on a set of multiple regressions for a dune slack of the Doñana National Park, and its utility to understand some ecological processes. The variation in the coefficients of the regressions for different locations allows discrimination between different zones in the dune slack, and explains the spatial pattern of heath vegetation observed in the stabilized sands. Model simulations were compared with an existing sparse data set of water-table levels, and suggests possible mechanisms responsible for the catastrophic pine tree mortality, which happened during the drought of 1979–83.     

An Investigation of Higher-Order Closure Models for a Forested Canopy

Simultaneous triaxial sonic anemometer velocity measurements vertically arrayed at six levels within and above a uniform pine forest were used to examine two parameterization schemes for the triple-velocity correlation tensor employed in higher-order closure models. These parameterizations are the gradient-diffusion approximation typically used in second-order closure models, and the full budget for the triple-velocity correlation tensor typically employed in third-order closure models. Both second- and third-order closure models failed to reproduce the measured profiles of the triple-velocity correlation within and above the canopy. However, the Reynolds stress tensor profiles (including velocity variances) deviated greatly from the measurements only within the lower levels of the canopy. It is shown that the Reynolds stresses are most sensitive to the parameterization of the triple-velocity correlation in these lower canopy regions where local turbulent production is negligible and turbulence is mainly sustained by the flux transport term. The failure of the third-order closure model to reproduce the measured third moments in the upper layers of the canopy-top contradicts conclusions from a previous study over shorter vegetation but agrees with another study for a deciduous forest. Whether the third-order closure model failure is due to the zero-fourth-cumulant closure approximation is therefore considered. Comparisons between measured and predicted quadruple velocity correlations suggest that the zero-fourth-cumulant approximation is valid close to the canopy-atmosphere in agreement with recent experiments.     

Stratigraphy and tectonics of the Early to Middle Proterozoic transition,Katherine‐El Sherana area,Northern Territory

Abstract

Two unconformity‐bound groups of volcanic rocks and associated sediments (El Sherana and Edith River Groups) separate the older Pine Creek Geosyncline metasediments from platform cover of the McArthur Basin. Dominated by intersecting NW and ENE rift systems, the volcanics are genetically related to an extensional tectonic system which was also active during deposition of the Pine Creek Geosyncline sequence. In contrast, the younger platform cover was deposited in a relatively stable environment. The rift valleys were filled with rhyolite flows, ignimbrite and ill‐sorted arenite and rudite, and flyschoid sediments spread onto adjacent lands. Following tight upright folding, granite intrusion and erosion, an extensive ignimbrite sheet (=6000 km²) spread from a centre probably at the intercept of the two rifts. Microgranite at this intersection was possibly emplaced in the evacuated magma chamber. The volcanic sequences were deeply eroded and weathered before platform cover deposition began. The platform sediments, represented in the area by the Kombolgie Formation, were deposited from about 1690 Ma to 1650 Ma, and their base is taken as the closest stratigraphic indicator of the boundary between the Early and Middle Proterozoic.     

云南省松材线虫病风险评估GIS平台开发

松材线虫病被称为松树的＂癌症＂。云南省针叶树种面积大,松材线虫寄主多,地形复杂,虫病防治难度大。综合运用.NET平台、ArcEngine组件技术、ArcSDE空间数据库引擎技术、SQL Server数据库技术,在云南省气象、空间、松材线虫数据基础上,建立一个云南省松材线虫病风险评估GIS平台,主要包括图层控制、风险评估、疫点操作、地图显示、专题图输出等功能,对云南省松材线虫病疫情进行更加精细化、标准化、可视化的评估。     

Geochemistry of the low‐grade Early Proterozoic sedimentary sequence in the Pine Creek Geosyncline,Northern Territory

Abstract

The geochemistry of Early Proterozoic sedimentary rocks from the low‐grade metamorphic terrain W of the South Alligator Hinge Zone in the Pine Creek Geosyncline is reported and discussed in terms of the stratigraphy and differences in rock type. Major element trends are dominated by lithological and mineralogical variations; in particular, the dolomitic nature of pelites in the Mount Partridge and Namoona Groups, the presence of chlorite in Crater Formation pelites, and the volcanic affinity of pelites within the Gerowie Tuff. Concentration of Th, U, Zr, Y, Nb, Ce and La in the clastic sediments of the Finniss River and South Alligator Groups is probably related to the presence of felsic volcanics in these groups; high levels of Sn in these groups may be similarly related, and highlight the apparent volcanogenic source for this metal. The South Alligator Group is a preferred host for base‐metal mineralization, and the regional abundance of several metals in this group enhance its economic potential and support a syngenetic, possibly exhalative, origin for these deposits. Anomalous Co, Ni, and V values in Masson Formation pelites are probably related to the nearby mafic Stag Creek Volcanics. Detrital minerals derived from reworked Archaean basement account for high Zr and Th in the Crater Formation. The geochemical data support the shift in REE patterns related to changes in crustal composition about the Archaean‐Proterozoic boundary, though patterns within the Early Proterozoic have also been influenced by felsic volcanism in the South Alligator Group. The chemical index of alteration (which reflects the degree of weathering of sedimentary rocks) reflects the existence of a major unconformity between the Mount Partridge and Namoona Groups; however, other hiatuses observed in or inferred from the rock record are not evident. The dominant felsic volcanic component of the Gerowie Tuff pelites is also indicated by this technique.