东灵山植物群落生活型谱的比较研究

应用由丹麦学者Ｒａｕｎｋｉａｅｒ提出的生活型分类系统,研究了北京东灵山植物群落的生活型,并编制了主要植物群落类型的生活型谱。同时,用主成分分析（ＰＣＡ）作为排序的方法和系统聚类中的离差平方和法与类平均法,对东灵山植物群落的生活型谱进行了排序和分类。并用双重筛选逐步回归的方法分析了环境（气候和土壤）因子与植物群落生活型谱梯度的关系,建立了相应的数学模型。研究结果表明：东灵山地区植物群落生活型谱的特征符合暖温带植物生活型谱的基本特点,地面芽植物占的比例最大。但不同植物群落因所存在的生境有差异,也表现出各自的谱特征。排序的结果与用植物种类成分进行的ＤＣＡ 排序结果吻合度较好,排序的环境梯度特征也十分明显。研究结果还表明：地下芽和中高位芽对于温度梯度的反应比较灵敏;其次是小高位芽和一年生植物;对于水分梯度的变化,则以地上芽和矮高位芽植物的反应比较强烈和敏感。温带植被生活型谱主要特征的地面芽植物在本地区表现稳定,不随各植物群落和水热梯度发生大的波动,显示出地带性的强大约束力。所建立的海拔梯度和群落类型与生活谱的统计数学模型,对于中高位芽、矮高位芽和地下芽植物的相关较好,估测的精度高,而对其它几种生活型的估测较差     

东灵山地区植物区系的基本特征与若干山区植物区系的关系

东灵山地区拥有高等植物997种, 隶属于127科、476属, 其中, 种子植物有97科、430属、935种。最大的科是菊科, 共有116种, 其它超过25种的科还有禾本科等7科。这8个科共457种, 占东灵山种子植物种总数的近46%。430属种子植物分别属于15个分布类型, 占第一位的是北温带分布类型, 有155属之多。各类温带分布类型共298属, 各类热带、亚热带分布类型仅有76属, 说明东灵山地区植物区系具有很强的温带地质。此外, 世界分布类型有50属, 中国特有分布类型有8属。根据吴征镒等学者的理论, 本文对植物区系谱的概念和分析方法进行了改进, 利用主成分分析(PCA)对东灵山地区植物区系与我国其它地区植物区系所构成的 植物区系谱进行了定量研究, 探讨了东灵山地区的植物区系在我国一系列山区植物 区系中的地位。对我国包括东灵山地区在内的29个山区植物区系进行了定量分 析, 降维效果很好, 前2个轴的累计贡献率近于80%, 前3个轴已超过92%。通过 常用的热带属与温带属比率(R/T)的计算也得到了与此相近的结果, R/T值随 着纬度的升高近于单调下降, 植物区系纬向地带性规律得到了很好地显示。     

松嫩平原南部植物群落的分类和排序

 松嫩平原南部的气候具有温带半湿润大陆性的特点。地带性植被为草甸草原。由于小地形起伏,土壤盐碱和水分含量有差异,影响植物的分布和组合,形成不同的群落。本文采用定性和定量相结合的方法,对该地区的植物群落进行了分类和排序,划分了11个群落类型,归为5类生态组合。通过样地和群落的排序说明植被既是连续的,又是间断的,同时明显看出植物群落随着土壤盐碱和水分含量的变化。     

京西百花山地区环境梯度与植物群落

 本文应用梯度分析的原理与方法,在有一定人为干扰的自然植被地段研究植物种群、植物群落与环境之间的相互关系,分析了植物种群、植物群落沿环境梯度的分布状况。     

宁夏盐池荒漠草原植被的数量分类和排序

为检验荒漠草原封育恢复的效果,对宁夏盐池围封9年的退化草场进行了植被调查,共记录34个物种,分属于12个科、27个属,其中豆科(9种)、禾本科(7种)、菊科(6种)所含物种数较多.与封育前相比,物种组成基本相同,常见种和建群种发生了明显变化.采用PCA排序和分层聚类将80个样方分为长芒草、白草、赖草3个群系,依据建群种或优势种的生物学特性将其生境划分为旱生生境、中生生境和轻度盐渍化生境.3个群系的演替速率不同,其中长芒草群系演替进入反应阶段,赖草群系的演替等级相对较高.群系间存在激烈的资源竞争关系,风蚀能够促进赖草群系的进一步扩大.建议通过划区轮牧的方式合理调控长芒草群系和赖草群系的放牧时期,以提高草场的放牧利用价值,降低赖草群系的扩张危险.     

青海湖北岸植物群落与环境因子关系的初步研究

依据对青海湖北岸 1 8个群落的样方调查和环境因子原始数据 ,用主分量分析 ( PCA)排序技术和回归模型 ,定量分析湖滨平原植物群落在空间地理上的分布格局 ,以及群落结构特征和环境梯度之间的关系。结果表明 :植物群落的类型分布主要决定于环境中的土壤水分含量及土壤全盐含量。代表植物群落结构特征的生物多样性 ( X1)和生态优势度 ( X2 )分别与环境梯度没有显著的相关性 ,但是 ,这两个指标和第一主分量排序轴 (土壤水分度 ,Y)的二元线性回归关系显著 ,回归模型为 :Y =- 4 .85 1 .4 7X1 1 0 .71 X2 ( P <0 .0 1 )。     

A mathematical model for water and nutrient uptake by plant root systems

This article deals with modelling the simultaneous uptake of water and highly buffered nutrient, such as phosphate, by root branching structures from partially saturated soil. We use the simultaneous water and nutrient uptake model to investigate the effect that water movement has on nutrient uptake. With the aid of this model we are also able to show that the previous models by Barber and Tinker and Nye systematically underestimated the phosphate uptake, due to the oversimplified approach in dealing with root branching structure. In this article we show how this discrepancy can be remedied and the root branching structure included in the models of plant nutrient uptake. We will also discuss the differences in the results for continuous and spot fertilization combined with variable rainfall.     

The eco-sociological value of dispersal spectra of two plant communities

Summary A new system of dispersal units has been elaborated, based on weight and morphological features functional in dispersal. Weight was divided into eight classes and the functional morphological features were selected in such a way that their effectiveness could be tested by experiments.The spectra of weight and dispersal adaptations of dispersal units sampled in Euphorbio-Pinetum nigrae and Fumano-Stipetum habitats south of Vienna are calculated with this system and then compared.The results show that both communities can be characterized with such spectra. It is also possible with these spectra to make statements about the ecological and social position of the association in a succession.Nomenclature follows Ehrendorfer (1973).     

川西北甘南云冷杉林的DCA排序、环境解释和地理分布模型的研究

 本文应用DCA排序的方法进行了四川西北部和甘肃南部云冷杉林的梯度分析,建立了植物群落梯度环境解释的数学模型和植物群落地理分布的数学模型。研究结果表明：影响川西北甘南云冷杉林植物群落地理分布的生态梯度中最显著并起主导作用的是温度梯度和水分梯度。在水分梯度上,大致有这样的植被序列,由较湿的藓类和杜鹃冷杉及云杉林,中生性的箭竹冷杉林和云杉林,偏旱的高山栎冷杉林和云杉林;处于恢复中期的桦木林的生境也偏旱,但一般不如高山栎林。冷杉林比云杉林更趋于阴湿的生境。 在温度梯度上,呈现出灌木云杉林—桦木林—落阔冷杉林—高山栎云杉林—箭竹云杉林—箭竹红桦林—高山栎冷杉林—藓类红桦林—藓类云杉林—箭竹冷杉林—藓类云冷杉林—藓类冷杉林—小叶章云杉林—杜鹃冷杉林的排序。基本特征是：川西北和甘南的云杉林的温度需求高于冷杉林。川西北云冷杉林与甘南云冷杉林在DCA排序轴上没有明显的区别。虽然川西北地区云冷杉林的海拔分布高于甘南地区,但是其纬度也低于甘南,故在温度条件上基本一致。在水分梯度上,川西北云冷杉林的湿度要稍大于甘南云冷杉林。利用植物地理分布的数学模型和有关的图、表,详细地分析了植物群落的空间分布,进行了环境解释,并找出了主导的环境因子。     

Structure,diversity, and regeneration of tropical dry deciduous forest of northern India

This study examined the impact of disturbance on the pattern of diversity, forest structure and regeneration of tree species in the Vindhyan dry tropical forest of India. A total of 1500 quadrats distributed over five, 3-ha permanent plots in five sites, differing in degree of disturbance, were used to enumerate and measure the tree species. A total of 65 species with 136,983 individuals were enumerated in the total 15-ha area for stems 30 cm height. The number of species and number of stems ranged from 12 to 50 and 8063–65331 per 3-ha area. The number of species and stems for trees 10 cm dbh ranged from 3 to 28 species, with a mean value of 16 species ha^–1, and from 16 to 477 stems, with a mean value of 256 stems ha^–1, respectively. The adult based PCA ordination indicated uniqueness of sites in terms of species composition and habitat characteristics. PCA ordination also showed uniqueness of sites in terms of seedling composition, but the seedling and adult distributions were not spatially associated. The distinct species composition at the different sites and at the two life-cycle stages on the same site is indicative of marked spatio-temporal dynamics of the dry tropical forest. The density–diameter semi-logarithmic curves ranged from a near linear to an overall concave appearance with a limited plateau in the mid-diameter ranges. The -diversity and its components decreased with increasing disturbance intensity, reflecting enhanced utilization pressure with increasing disturbance. The site-wise and species-wise regression analyses of the number of individuals in different stages of the species revealed that both the level of disturbance and the nature of species strongly affect the regeneration. In conclusion, although the forest is relatively species-poor, the differential species composition on different sites and the temporal dynamics lend a unique level of diversity to the tropical dry deciduous forest.     

Influence of light and soil moisture on Sierran mixed-conifer understory communities

Sierra Nevada forests have high understory species richness yet we do not know which site factors influence herb and shrub distribution or abundance. We examined the understory of an old-growth mixed-conifer Sierran forest and its distribution in relation to microsite conditions. The forest has high species richness (98 species sampled), most of which are herbs with sparse cover and relatively equal abundance. Shrub cover is highly concentrated in discrete patches. Using overstory tree cover and microsite environmental conditions, four habitats were identified; tree cluster, partial canopy, gap, and rock/shallow soil. Herb and shrub species were strongly linked with habitats. Soil moisture, litter depth and diffuse light were the most significant environmental gradients influencing understory plant distribution. Herb cover was most strongly influenced by soil moisture. Shrub cover is associated with more diffuse light, less direct light, and sites with lower soil moisture. Herb richness is most affected by conditions which influence soil moisture. Richness is positively correlated with litter depth, and negatively correlated with direct light and shrub cover. Disturbance or management practices which change forest floor conditions, shallow soil moisture and direct light are likely to have the strongest effect on Sierran understory abundance and richness.     

A model for water uptake by plant roots

We present a model for water uptake by plant roots from unsaturated soil. The model includes the simultaneous flow of water inside the root network and in the soil. It is constructed by considering first the water uptake by a single root, and then using the parameterized results thereby obtained to build a model for water uptake by the developing root network. We focus our model on annual plants, in particular the model will be applicable to commercial monocultures like maize, wheat, etc. The model is solved numerically, and the results are compared with approximate analytic solutions. The model predicts that as a result of water uptake by plant roots, dry and wet zones will develop in the soil. The wet zone is located near the surface of the soil and the depth of it is determined by a balance between rainfall and the rate of water uptake. The dry zone develops directly beneath the wet zone because the influence of the rainfall at the soil surface does not reach this region, due to the nonlinear nature of the water flow in the partially saturated soil. We develop approximate analytic expressions for the depth of the wet zone and discuss briefly its ecological significance for the plant. Using this model we also address the question of where water uptake sites are concentrated in the root system. The model indicates that the regions near the base of the root system (i.e. close to the ground surface) and near the root tips will take up more water than the middle region of the root system, again due to the highly nonlinear nature of water flow in the soil.     

太行山区冬凌草生态环境及生物学特性研究

对冬凌草在太行山区生长的生态环境及其生长区的植物群落进行了调查分析,对冬凌草的生长发育规律进行了研究,为了解冬凌草生物特性的形成以及确定人工种植条件提供了科学依据.     

一种描述针刺对脉象影响的方法

针刺与脉象在传统中医观念中是紧紧联系在一起的。本课题针对这一传统理论,建立一个基于频域上的模拟函数得出的脉象频谱数学模型,并用此模型来检验针刺前后脉象发生的结构上的变化。由量化的脉象信号得出的大量统计数据显示,脉象在频域上的包络线呈指数衰减的趋势,并且针刺后其拟合率更高。由统计结果得出,脉象在频域上的衰减率明显增大。同时,从数学上说明了其衰减率的增大等价于脉象在时域上的降中峡、重搏波,及低频涨落程度的变化,也对时域上的脉象作了新的数学模型的模拟。本项研究证实了针刺对脉象具有调整作用。     

The desert vegetation of El Pinacate,Sonora, Mexico

The Pinacate region is part of the Gran Desierto, one of the driest deserts in North America. The presence-absence of perennial plant species, together with soil and landform characteristics, were registered in 110 sampling sites within this region. A classification and ordination of plant communities showed soil and landform units to be good predictors of plant variation. Plant distribution and species richness were also strongly related to altitude and rockiness. A Generalised Linear Model was used to fit the response curves of individual species.The environmental factors related with plant distribution are indicators of the water regime within a given site. Plant communities repeat along topographic gradients the large-scale biogeographic variation of the Sonoran Desert. Microphyllous shrubs colonise the drier bajada slopes, while more diverse communities, dominated by cacti and drought-deciduous trees, grow on the wetter pediments and in pockets within rocky soils.     

Optimal phenology of annual plants under grazing pressure

Plants show phenological responses to herbivory. Some enclosure experiments have demonstrated that the onset of the peak flowering season is dependent on grazing pressure. We constructed a mathematical model using Pontryargin's maximum principle to investigate changes in flowering time by examining shifts in resource allocation from vegetative to reproductive plant components. We represented a primary production of a plant individual by two types of function of vegetative part size, a linear function and a convex non-linear function. The results of a linear production model indicate that optimal phenology follows a schedule that switches from the production of vegetative parts to that of reproductive parts at a given time ('bang-bang' control). However, in a non-linear model, a singular control, wherein the plant invests in both productive and reproductive parts, may be included between obligate production and reproduction periods. We assumed that the peak of the flowering season occurs immediately following the exclusive investment in reproduction. In a linear production model, differential herbivory rates on the vegetative and reproductive parts of a plant resulted in shifts in the peak flowering time. A higher herbivory rate on the vegetative components advanced the peak, whereas it was delayed when grazing pressure focused on reproductive components of the plant. In the non-linear production model, increased grazing pressure tended to postpone the flowering peak. These results corresponded well with results of enclosure experiments, thus suggesting adaptive control of flowering time in plants.