Soil‐vegetation relationships of three arid land plant species and their use in rehabilitating degraded sites

It is essential to consider soil characteristics when establishing vegetation in arid lands. In this study, the redundancy analysis (RDA) ordination method was used in this study to evaluate the habitats of Halocnemum strobilaceum, Limonium iranicum and Tamarix passerinoides growing in the Sejzy region, east of Isfahan. The study area was stratified into six ecologic‐floristic complexes. Stratified random sampling was then employed to collect soil and vegetation data from 1‐ha quadrats on nine sites. The soil samples were analysed to determine the characteristics of the soil in which the three species grew and to examine the soil profiles up to a depth of 2 m. Soil analyses revealed that high amounts of gypsum, silt, clay, saline, alkali and sulphate in the soil constituted a favourable habitat for Halocnemum strobilaceum. However, the per cent of silt and sulphate concentration in deep layers were negatively correlated with the growth of this species. Evaluation of the L. iranicum habitat revealed that the amounts of carbonate and CCE in the topsoil were positively correlated with the establishment and growth of the species but salinity and alkalinity were negatively correlated. The primary soil characteristics that positively influenced T. passerinoides included the presence of organic matter and bicarbonate ions in the soil layers and the total Ca and Mg content of the topsoil. However, Na was negatively correlated with Tamarix species. Determination of the soil characteristics that are associated with each of these xerophytic species can be used to determine which species is suitable for rehabilitating degraded sites in the study area. Copyright © 2010 John Wiley & Sons, Ltd.     

酸度对胡敏酸与镉和锌离子络合反应的影响

用离子交换平衡法研究了不同pH下胡敏酸与锌、镉单独及复合存在下形成络合物的稳定性及配位数.结果表明：在Zn^2＋,Cd^2＋单独存在时,络合反应的稳定常数及配位数随着pH值的增大而增大;相同pH条件下,Zn^2＋和胡敏酸络合物的稳定常数及配位数大于Cd^2＋.在Zn^2＋,Cd^2＋复合存在时,pH的变化与胡敏酸络合金属离子的稳定常数及配位数没有明显依存关系;与单独存在时相比,在pH 3.5和pH7.0时,Zn^2＋,Cd^2＋和胡敏酸络合物的稳定常数和配位数都减小;而在pH 5.0时,Cd^2＋和胡敏酸络合物的稳定常数和配位数都增大,Zn^2＋和胡敏酸络合物的稳定常数和配位数都减小.     

贺兰山灰榆群落的种间关联、排序及分类研究

贺兰山的灰榆群落具有重要的生态学意义和研究价值。在系统的样方调查基础上,对贺兰山灰榆群落类型及特征进行全面分析。结果表明:贺兰山灰榆群落的主要特征与海拔及地形因子相关。种间关联分析显示,群落中存在显著差异的喜阳耐旱种组和阴湿林下种组两组,灰榆与前者呈负相关,而与后者呈正相关。CCA排序将群落分为4个群丛,海拔和坡向是群落类型分异的主要影响因子。针阔混交林群丛分布在高海拔的阳坡,落叶阔叶疏林群丛分布在中高位置的阴坡,灰榆-蒙古扁桃疏林分布在中低海拔的阳坡,灰榆疏灌林分布在最低海拔的阴坡。4个群落的空间分布位置、物种组成和群落特征差异显著。在研究结论的基础上,对贺兰山灰榆群落的重建和保育提出了相对应的措施。     

Hierarchical,Multi-scale decomposition of species-environment relationships

We present an adaptation of existing variance partitioning methods todecompose species-environment relationships in hierarchically-structured,multi-scaled data sets. The approach translates a hierarchical, multi-scaleconceptual model into a statistical decomposition of variance. It uses a seriesof partial canonical ordinations to divide the explained variance inspecies-environment relationships into its independent and confoundedcomponents, facilitating tests of the relative importance of factors atdifferent organizational levels in driving system behavior. We discuss themethod in the context of an empirical example based on forest bird communityresponses to multiple habitat scales in the Oregon Coast Range, USA. Theexamplepresents a two-tiered decomposition of the variation in the bird community thatis explainable by a series of habitat factors nested within three spatialscales(plot, patch, and landscape). This method is particularly suited for theproblems of hierarchically structured landscape data. The explicit multi-scaleapproach is a major step forward from conducting separate analyses at differentscale levels, as it allows comprehensive analysis of the interaction of factorsacross scales and facilitates ecological interpretation in theoretical terms.This revised version was published online in May 2005 with corrections to the Cover Date.     

太原市草坪秋季杂草与草坪草的生态关系分析

2009年秋季对太原市不同类型的草坪植物进行物种调查和数量分类排序研究。结果表明,太原市草坪秋季入侵杂草种类达29科59属70种,其中菊科和禾本科的杂草最多;TWINSPAN分类将所调查的72个样方划分为14个群丛,各群丛的草坪草或主要的杂草有所不同;样方和优势种的DCA排序图第1轴反映了草坪土壤的湿度,沿着湿度梯度,草坪杂草由耐旱植物过渡为中生植物,第2轴反映了草坪除杂修剪程度的变化,除杂修剪程度不同,杂草的侵入种数和数量也不相同,人工管理养护水平是影响草坪杂草入侵的主导因子。     

西藏色季拉山林线植被群落数量特征

为揭示藏东南高山林线的植被空间分布及林线植被的生态适应性,应用TWINSPAN和DCA多元分析方法,以调查样地中草本、灌木和乔木层的重要值总和为指标,对色季拉山林线植被的特征进行分析,并分别以样地和物种为单位进行数量分类和排序.调查样地为色季拉山林线研究区域(林线及附近垂直高度1000 m)的森林及灌木植被类型,共26...     

现代黄河三角洲植物群落数量分类研究

采用TWINSPAN和DCA排序方法对现代黄河三角洲植物群落进行了数量分类。TWINSPAN将研究区植被分为碱蓬群落、柽柳群落和草本群落3大类,包括12个群落类型。采用3类物种多样性指数,计算了各群落的物种丰富度、均匀度和多样性。结果表明,从碱蓬群落、柽柳群落到草本群落过渡,多样性指数和丰富度指数逐渐增加。均匀度指数在碱蓬群落和柽柳群落波动较大,而在草本群落波动较小。DCA排序结果表明,决定现代黄河三角洲植物分布类型的环境因子主要是土壤盐分和水文状况。在土壤含盐量较高区域,植物群落物种组成单一,群落结构简单;在土壤含盐量较低区域,组成群落的植物物种丰富,群落结构复杂。      

Climate shapes the novel plant communities that form after deforestation in Puerto Rico and the U.S. Virgin Islands

Environmental and past land use controls on tree species assemblages on the Commonwealth of Puerto Rico and the U.S. Virgin Islands were characterized to determine whether biophysical factors or land-use history has been more important in determining the species composition of secondary tropical forests after large-scale forest clearing for agriculture, widespread species introduction, and landscape-scale forest fragmentation. Post-deforestation, secondary forest assemblages are comprehensively described, both as broad general assemblages and island-specific variations by calculating species importance values from forest inventory data. Hierarchical clustering and indicator species analysis defined species assemblages, and then correlations between species assemblages and environmental variables were explored with non-metric multidimensional scaling, analysis of variance and χ² testing. These assemblages are arrayed along environmental gradients of decreasing spring moisture stress, decreasing maximum temperatures, and increasing minimum temperatures. Land-use history is not as important to determining variation in species composition across climatic zones, although several species assemblages are associated with certain geology types or land-use histories. Naturalized tree species are prominent in these secondary forests and contribute to the formation of some novel assemblages, but native late and early successional species also colonize former agricultural land, all influenced by the degree of disturbance. We conclude that environmental factors have an overarching effect on forest species composition across the broader range of climatic, geologic and topographic conditions and larger geographic scales, while land-use history influences subtropical secondary forest species assemblages within a specific climatic zone or set of relatively narrow environmental conditions.     

青海湖湖盆南部植物群落二维极点排序

利用极点排序对青海湖湖盆南部的植物群落进行了分析。结果表明，在研究地区不同海拔影响植物群落分布的主要环境因子不同。根据影响植落分布的环境因子的变化情况，可将研究地区划分为３个地段，即较低地段，中间地段和较高地段。