Showing papers in "Plant Ecology in 1980"

Detrended correspondence analysis: an improved ordination technique

Abstract: Studies by ourselves and others (Swan 1970, Austin & Noy-Meir 1972, Beals 1973, Hill 1973, 1974, Austin 1976a, b, Fasham 1977, Gauch Whittaker & Wentwarth 1977, Noy-Meir & Whittaker 1977, Orloci 1978, Gauch, Whittaker & Singer 1979) have found faults with all ordination techniques currently in use, at least when applied to ecological data specifying the occurrences of species in community samples. These faults certainly do not make existing techniques useless; but they mean that results must be interpreted with caution. Even with the best techniques, the underlying structure of the data is often poorly expressed.

The Use of Vital Attributes to Predict Successional Changes in Plant Communities Subject to Recurrent Disturbances

Abstract: The established view of ecological succession is that, following a disturbance, several assemblages of species progressively occupy a site, each giving way to its successor until a community finally develops which is able to reproduce itself indefinitely. Implicit in this view is the assumption that each suite of species modifies the site conditions so that they become less suitable for its own persistence and more suitable for its successor, and the assumption that only the final community is at equilibrium with the prevailing environment. These ideas owe their origin largely to Clements (1916, 1936) who viewed the community as a kind of super-organism, and succession as a form of ontogeny. They are entrenched to various degrees in the ecological literature and have been supported by many authors (see, for example, Golley 1977).

Structural and floristic diversity of shrublands and woodlands in Northern Israel and other Mediterranean areas

Abstract: Between 1974 and 1978 structure and diversity of shrublands and woodlands of northern Israel were studied along climatic and human-disturbance gradients using 0.1 ha vegetation samples. Diversity increased along the moisture gradient, with highest woody and herb species richness in open Pistacia shrubland on the xeric border of the Mediterranean region, and highest equitability and lowest dominance concentration in sub-humid, moderately grazed, open oak woodlands. Semi-open disturbed shrublands were rich in herbs and had much higher structural, plant species, and animal species diversities than the closed, mature, ‘climax’ maquis. Diversity showed a two-slope response to grazing with highest species numbers in heavily (but not the most severely) grazed woodlands and shrublands. These communities have some of the highest plant alpha diversities in the world; the richness of their floras (especially in annual plants) is the product of relatively rapid evolution under stress by drought, fire, grazing, and cutting. Comparative data on diversity and growth-form composition are compiled for mediterranean communities: Israeli' shrublands and woodlands, California chaparral and woodlands, Chilean matorral, South African fynbos, and Australian heath and mallee. Communities of three of these areas are of more recent (primarily Pleistocene) development and share some similarities; these threc form a sequence (California, Chile, and Old World Mediter-ranean) of increasing length of human disturbance and consequent species diversity. The southwest Australian heath or kwongan and the South African fynbos are, in contrast, derived from ancient Gondwanan heath like communities and are adapted to very old, nutrient-poor soils. The Gondwanan communities are quite different in growth-form structure and soil and nutrient relationships from communities of the three more recent mediterranean areas; the Gondwanan communities are almost lacking in annual species and are exceedingly rich in woody species. The richest temperate plant communities known — grazed Mediterranean pastures vs. fynbos and Australian heath — are in almost polar contrast in their growth-form structures and the bases of their species diversities. This study, sponsored by the U.S.-Israel Binational Science Foundation (No. 450), was carried out by Z. Naveh as principal investigator with R.H. Whittaker as American collaborator. We thank Mr. A. Mann, S. Burmil, Mrs. Chaim, and Mrs. A. Kleen for botanical field work and statistical computations, Mr. D. Feigin and S. Ben Ezrah for technical assistance, Mr. S. Asherow for identification of young plants, and the Nature Reserve Authorities, the Neve Yaar Experimental Station, the Agricultural School Kfar Hanoar Hadati, and Kibbutzim Allonim and Allone Abba for allowing us to use their land for this study. The work by R.H. Whittaker was supported by the U.S. National Science Foundation, Australian National University, and Canberra Botanic Gardens; and we thank all the collaborators in this work.

Succession: a population process

Abstract: For over 80 years succession theory has played a central role in plant ecology, providing both a predictive tool and organizational scheme. Drawing on this long history of research and observation, Margalef (1968), Odum (1969), Whittaker (1975) and others have identified general trends in community development. Their synthetic treatments have helped focus the efforts of subsequent workers examining the empirical and experimental basis of succession theory (e.g. Connell & Slatyer 1977, Drury & Nisbet 1973, Egler 1975, Horn 1974, Pickett 1976, van Hulst 1978). This more recent work suggests that the classical succession paradigm is seriously flawed and that many long held concepts need to be reexamined.

Searching for a Model for Use in Vegetation Analysis

Abstract: Current methods of indirect vegetation analysis either explicitly or implicitly assume a certain ecological model of how vegetation responds to environment Indirect or vegetational ordination methods; (Whittaker 1978) including the more recent methods; of reciprocal averaging (Hill 1973), multidimensional scaling (Fasham 1977, Prentice 1977), PARAMAP (Noy-Meir 1974), and Gaussian ordination (Gauch et al 1974; Ihm & van Groenewoud 1975) appear sensitive to small changes in the generating model (Austin 1976a, b) These indirect methods are multivariate exploratory data analysis techniques (Noy-Meir 1971, see also Tukey 1977) whose purpose is to expose the unknown ecological dimensions associated with floristic variation; their efficacy depends on the relevance of their model of the vegetation/environment relationship (Austin 1976a, Whittaker 1978) Testing their effectiveness with artificial data sets is entirely dependent on the appropriateness of the model used to generate the artificial data

Diversity and Stability in Garrigue Ecosystems After Fire

Abstract: By its frequent recurrence fire is an important factor for the dynamics of plant communities in the French mediterranean region. Up to now it was considered to create series of more and more degraded successive stages (Braun-Blanquet 1936, Kuhnholtz-Lordat 1938, 1958, Kornas 1958, effect of fire was studied by Le Houerou (1974, 1977) and as due to fire action. But, the processes by which vegetation is recovering after fire were not tackled precisely: the authors only compared different associations.

Fine-root production, mortality and decomposition in forest ecosystems

Abstract: The temporal variations in fine root growth, mortality and decomposition were studied in a young and a mature (18 and 120 year in 1974, respectively) Scots pine Pinus sylvestris stand located on sandy sediments of glacifluvial origin at Ivantjarnsheden in Sweden. The structural composition of this specific ecosystem type is fairly simple with only a few dominating vascular species with distinctive morphological rooting features, e.g. Pinus sylvestris, Calluna vulgaris, and Vaccinium vitis-idaea. The root phytomass of these species was separated into one living (biomass) and one dead (necromass) fraction when excavating and sorting the root samples.

Convergence in vegetation structure in the mediterranean communities of California, Chile and South Africa

Abstract: Plant communities on desert to montane transects in the mediterranean type climatic areas in southern California, central Chile and the Cape, South Africa have been analysed to determine the extent of vegetation convergence. Data on floristic richness, growth form, leaf duration, leaf size, and spineseence, of the woody plants, collected by Parsons & Moldenke (1975) from analogous climatic sites in California and Chile, were compared with data from analogous sites in the Cape. Considerable convergence in vegetation structure between floristically distinct but climatically similar sites in California and Chile has been demonstrated by Parsons & Moldenke (1975). Cape vegetation, however, shows little convergence to these mediterranean regions. In Cape desert communities succulence rather than drought deciduousness is the principal adaptive strategy. Cape fynbos communities show major differences from communities at analogous sites on the other continents. Much of the divergence between fynbos and the vegetation of the other continents can be attributed to the nutrient-poor soils on which fynbos has evolved.

The Individualistic Nature of Plant Community Development

Abstract: Most models of plant community development (succession) explicitly or implicitly consider the process to be a series of graded steps culminating in, or converging upon, some relatively stable long-term plant community. Those models which do not proceed by an orderly series of steps nevertheless call for relatively predictable changes in plant communities. Recently, Connell & Slatyer (1977) have seriously questioned the ‘facilitation’ models of succession, and Olson (1958), Drury & Nisbet (1973), Walker (1970) and Matthews (1979) have questioned the hypothetical convergence of successional pathways. In this paper, I use several sources of evidence to call into question the predictability of plant community change over time. Two of these sources are anecdotal observations, three are reviews of previously published data, and one is research first described here in detail; the quantitative data come from vegetation studies in the north-central United States.

Vegetation Dynamics and Sex Structure of the Populations of Pioneer Dioecious Woody Plants

Abstract: The incursion of trees and shrubs in the course of succession is frequently so impetuous that it has often been referred to as ‘invasion’ (e.g. Blackburn & Tueller 1970, Brakenhielm 1977, Tuxen 1973, Hard 1975, Meisel 1978, Falinski 1980, in press).

Development of Species Diversity in Some Mediterranean Plant Communities

Abstract: Changes in plant species composition during succession are interpreted as the result of a dynamic equilibrium between colonization, persistence and extinction of species.

Ordination as a Tool for Analyzing Complex Data Sets

Abstract: Ordination, or indirect gradient analysis, has been widely used in plant ecology as a tool for examining relationships between environment and vegetation. Since the classic work of Bray & Curtis (1957) which popularized such applications, the mathematical models underlying ordination methodology have become increasingly sophisticated. Principal Components Analysis provided increased conceptual rigor and objectivity. The realization that the assumptions of linearity implicit in PCA were not consistent with representation of nonlinear species responses along environmental gradients (Beals 1973, Jeglum, Wehrhahn & Swan 1971, Whittaker & Gauch 1973) led to introduction of a series of nonlinear methods including Reciprocal Averaging, RA, (Hill 1973, 1974), Gaussian Ordination, GO, (Gauch, Chase & Whittaker 1974, Ihm & Groenewoud 1975) and Nonmetric Multidimensional Scaling, NMDS, (Fasham 1977, Prentice 1977). Subsequent comparative studies (e. g., Fasham 1977, Gauch, Whittaker & Singer 1980) have suggested these nonlinear methods to consistently and accurately recover the structure of simulated data.

Plant species diversity in cape fynbos: gamma and delta diversity

Abstract: This paper reports the number of plant species on circumscribed fynbos areas (gamma diversity), ranging in size from 0.27 km2 (a site with 364 species) to 471 km2 (2351 species). The composition of the floras of four of these sites was analysed to measure delta diversity, the change in flora from one site to the next. Maximum gamma diversity values fitted a species-area curve log S=2.69+0.25 log A. Gamma diversity is apparently higher than in any of the world's biogeographic zones except perhaps the tropical rain forest, and in other South African sites of areas around 1.0 km2, which have about as many species. High delta diversities are reflected in differences between fynbos floras of 50 to 70 %, in spite of relative proximity; this degree of diversity is apparently unmatched anywhere. The results support the conventional view that fynbos plant diversity is partly a consequence of the peculiar geography of the zone, and of palaeo-climatic change, which have favoured geographic speciation.

The development of numerical classification and ordination

Abstract: The invitation to open this session set me thinking about the development of numerical procedures of classification and ordination. Their technical development has been reviewed by various authors from various viewpoints, e.g. Cormack (1971), Orloci (1975, 1978), Dale (1975), Goodall (1970), Greig-Smith (1954, 1964, 1980), Whittaker (1967, 1973). I do not intend to discuss this in more than broad terms, but there is another aspect that has received less attention. This concerns the influences and constraints which have affected the development of numerical methods and their acceptance by phytosociologists. Their acceptance is particularly important; numerical methods are tools and unless they are used in the investigation of real ecological problems we are wasting our time in developing them.

Succession in a South Swedish Deciduous Wood: A Numerical Approach

Abstract: Studies of successions in vegetation must, in many cases, involve observation periods of considerable length. Especially when successions are dependent on or strongly influenced by developments in tree- and shrub layers, observations must be extended over decades. Very rarely one and the same investigator is in a position to be able to observe his permanent plots for such a long time. An alternative to this dilemma is the possibility of reestablishing, with acceptable accuracy, the plots once used and having them analyzed by other investigators. The approach thus uses semipermanent plots, and I use the term corresponding quadrats for those unit areas used to sample one such plot at different points in time.

Preliminary survey of the peat-bog Hummell Knowe Moss using various numerical methods

Abstract: (1) Hummell Knowe Moss is one of several fine and relatively undamaged peat bogs in northern England, close to the border with Scotland. (2) The central, eccentrically domed, mass of peat is ca 300×600 m, and much of this is 7 to 10 m deep. (3) A single profile has 8 m of bog peat overlying 2.5 m of Phragmites peat with seeds of Potamogeton and Nymphaea. The bog as a whole is probably part ‘raised’ and part ‘blanket’, as are others in the area. (4) Much of the present surface is wet, with Sphaanum magellanicum, Eriophorum spp., Andromedia polifolia etc. There are some eroded areas with less Sphagnum and more abundant fruticose lichens (Cladonia spp.), and marginal areas with Molinia caerulea, Deschampsia flexuosa, Sphognum recurvum and Polytrichum commune. (5) Numerical analyses show the importance of data transformation. Of the ordination methods tried, PCA produced unhelpful results, but RA, PCO and NP-MDS were all adequate. PCO can take a variety of dissimilarity measures, but not all produce useful results. NP-MDS is more tolerant, and can also be used to adjust the relative importance of inter-pair dissimilarities in a more flexible way than can PCO. (6) Further analyses by RA after removal of outliers were not of great use, but those by PCO and NP-MDS revealed clear patterns. Two of the groups of sites were less clearly developed versions of the erosion and marginal vegetation types. The third type may be developed in slightly drier conditions, or may in some places result from differences in management. (7) The usefulness of the methods in this survey was NP-MDS > PCO > RA > PCA. Computing cost of NP-MDS, PCO and RA paralles usefulness: more useful, greater cost.

On the interpretability of ordination diagrams

Abstract: In my review of multivariate methods in phytosociology (van der Maarel 1979) I briefly commented on the interpretability of Type A distortions (see Orloci 1974b, 1978), i.e. ‘horseshoe’, (‘arch’) effects in ordination diagrams of axes 1 and 2. Such effects are now generally recognized as the result of curvilinearities intrinsic to community data i.e. (1) the bellshaped species response curves along environmental gradients and (2) the nonlinear decrease of sample similarity with increasing sample separation (Gauch, Whittaker & Wentworth 1977, see also Swan 1970, Noy-Meir & Austin 1970, Gauch & Whittaker 1972, Austin 1976, Noy-Meir & Whittaker 1978 and Whittaker & Gauch 1978 to mention a few papers I consulted again for this purpose). Hill & Gauch (1980) even say more straightforwardly: ‘the arch effect is simply a mathematical artifact, corresponding to no real structure in the data’, when discussing faults of reciprocal averaging.

Some effects of grazing on vegetation dynamics in the Camargue, France

Abstract: The effects of horses, rabbits and coypu on plant succession were studied in five different vegetation types in the Camargue (southern France) over three years. The horses had a very marked effect on a Scirpus maritimus-Phragmites marsh, considerably reducing the amount of the two main species. In the other sites, the effects were less drastic. In the two grassland areas, they reduced the vegetation height in the third year, and there was also a change in species composition at one site which was used more intensively than the other. In a second marsh site, they caused a reduction in the amount of the dominant grass (Aeluropus litoralis), while they controlled the quantity of two of the principal species of a dwarf serub area (Halimione portulacoides and Puccinellia distans). The effects of the rabbits and coypu, on the other hand, were not very pronounced. Very high rainfall during the experiment was an important constraint on succession. These are preliminary results from a long term study of vegetation dynamics in the area.

Vegetation Dynamics or Ecosystem Dynamics: Dynamic Sufficiency in Succession Theory

Abstract: Recently several authors have claimed that long term vegetation change, at least in the case of forest ecosystems, can usefully and quite accurately be described by stationary Markov chain models (Anderson, 1966; Waggoner & Stephens, 1970; Horn, 1974, 1975a, 1975b, 1976) or their deterministic counterpart, coupled differential equation models (Shugart et al., 1973). Markov chain models do indeed form a class of unusually versatile and well-studied models and their exploratory use as models of succession would seem quite appropriate (for an introduction see van Hulst 1979 and references therein). Markov models, for example, can mimic not only simple linear succession (with species or community B replacing species or community A C replacing B, and so on), but also successions involving such phenomena as reversals or ‘sticky’ states, cyclical successions, indeterminate situations, a gradual approach to a steady state, and several other complications (see e.g. Horn 1976).

Vegetation survey of the Alaska Highway, Yukon Territory: types and gradients.

Abstract: The vegetation and environment in the vicinity of the Alaska Highway in the southern Yukon were surveyed. Our methods included stratified random sampling and automated data analysis. The vegetation units and compositional gradients, which we recognized, and the nature of the environmental conditions which characterize them, are described. Our results clearly indicate a significant group structure at the level of different vegetation units, and a close relationship of compositional variation in the vegetation to changing environmental conditions. We offer the contents of this report for predictive use in applications where site sensitivity or other ecological conditions have to be assessed, or a framework is needed for a more complete ecological inventory. The authors also thank Misses C. Emo, D. State, Messrs. P. Fewster and P. Merluzzi for their participation in the field work; Miss D. State for assistance in the preparation of the manuscript; Drs. G.W. Douglas and P. Vaartnou for sharing floristic information; Ms. B.J. Woodfield, Messrs. L.W.Bouckhout, R.A. Owens, C. Fouks, M. Romaine, C.E. Brown, E. Nyland, and D. Schuler for contributions in various ways to facilitate completion of the report. The Federal Department of the Environment, ALCAN Task Force, and Foothills Pipe Lines (South Yukon) Ltd., Calgary, Alberta, funded the project, and also supported this publication. Foothills also made available photo mosaics, aerial photographs, and other necessary maps.

Patterns of Plant Species Diversity in Fynbos Vegetation, South Africa

Abstract: Fynbos is the broad category of sclerophyllous shrublands which dominate the vegetation of the southwestern Cape, South Africa (see Kruger 1979 & Taylor 1978 for detailed descriptions). Plant species diversity both at the landscape level (gamma diversity) and at the community level (alpha diversity) is, supposedly, exceptionally high. Kruger & Taylor (1980) suggest that gamma diversity is apparently much higher than in any of the other world’s biogeographic zones, except the tropical rain forest zones and other South African sites of about 1 km2. Kruger (1977) states that fynbos communities are probably the richest shrubland communities in the world. He states further that with the exception of plant communities in extreme habitats (for example, where soils are alternatively waterlogged and droughted), alpha diversity is consistently high and some record figures are 83 species on 50 m2 and 121 species on 100 m2 (data from Taylor 1977, 1978). These figures exclude annuals and geophytes. Kruger et al (1977) suggest that ‘it could be that fynbos community diversity is exceeded only by that of tropical rain forests, if at all”.

Changes in mediterranean shrub communities with Cytisus purgans and Genista scorpius

Abstract: Shrub communities are important in the mediterranean landscape and linked very much with human activities. The permaneney and the spreading of these communities are related to biological characteristics of the dominant species which control the patterns of changes in structure, richness, ‘types of life forms, and ability of colonization by trees. In this paper, changes in communities are analysed and compared for Cytisus purgans and Genista scorpius (both Papilionaceae). For both communities the schemes of origin and spreading are rather the same: overgrazing and fire play a prominent role. Changes in structure show different stages emphasized by the types of distribution of the chlorophyll containing stratum. There is a direct relation between changes in structure and changes in species richness and life form spectrum: richness decreases generally from the second or third year after fire. According to the dryness of the stand therophytes may or may not be important in the youngest stands. The colonization of the shrub communities by trees is dependent on several conditions, either on the shrub community itself, or on the plant-matrix surrounding the shrub community patch and also on animals; man, too, plays an important role. In conclusion we think that the above-mentioned changes in shrub communities fit the ‘inhibition’ model proposed by Connell & Slatyer (1977); but, more generally it seems that the plant successions observed in our regions follow both, this model and the ‘facilitation’ and ‘tolerance’ models of the same authors. Linked with this fact, it seems that the successions show generally fluctuating values of richness as is suggested by Whittaker (1975). We think that plant succession must be well analyzed at different levels of organization and include the study of the influences man and animals may have.

An Exploratory Analysis of Grassland Dynamics: An Example of a Lawn Succession

Abstract: The floristic composition of a lawn is studied by means of permanent plots over ten years. Observations show that changes in the life history behaviour of certain species (Trifolium repens, and Sagina procumbens) have important effects on the vegetation dynamics of the lawn. These changes are ascribed to senescence and possibly a pathogen. Numerical classification (divisive information analysis) is used to define suitable classes for transition matrix simulation of grassland succession. The influence of life history changes and catastrophic drought is incorporated by estimating appropriate transition matrices. The limitations of the approach due to spatial patterns are emphasized.

Evaluation of Ordination Methods Through Simulated Coenoclines: Some Comments

Abstract: The ordinations based on resemblance matrices (Orloci 1978b) received special attention in plant ecology during the past decade. Many papers dealing with this topic could be mentioned. It should however be satisfactory to refer to the general survey by Dale (1975). He distinguished two main approaches in ordination (cf. also Beals 1973): One is associated with pattern recognition and pattern analysis (ordination sensu lato, Noy-Meir & Whittaker 1977), which started with Goodall (1954) and is still dominant in phytosociology (see Westhoff & van der Maarel 1978 and Orloci 1978a for references). The other one is more strictly related to Whittaker’s work (ordination sensu stricto, Noy-Meir & Whittaker 1977) and concerned with gradient analysis (Whittaker 1967)

Vegetation analysis and order invariant gradient models

Abstract: Ordination has been a major topic of recent research in vegetation analysis. A central problem has been to find a method that will recreate ecological gradients from vegetation sample data, given that species are expected to respond to gradients in a certain way: thus the current approach to ordination involves an explicit ecological response model, and differs from the purely ‘descriptive’ approach where efficient reduction of dimensionality is the sole objective.

Rapid Initial Clustering of Large Data Sets

Abstract: Multivariate analysis of plant community data primarily involves ordination and classification. The data analyzed are abundance or/and cover values of species recorded for a number of samples, resulting in a species-by-samples matrix of observations. Multivariate analysis of such data has three general aims: (1) to identify similar, redundant samples, (2) to identify outliers (samples very different from all other samples), and (3) to elucidate relationships among samples. (Alternatively analysis may concern species or both species and samples, but for simplicity only samples are discussed here). These three aims correspond to aspects of the data with different underlying biological processes and different requirements for mathematical analysis, and may be characterized as follows.

A numerical study of successions in an abandoned, damp calcareous meadow in S Sweden

Abstract: Two sites at Orup, SE skane, Sweden, have been investigated, viz. a grazed, unimproved, tussocky pasture on a calcareous moraine clay; and an originally similar, adjacent area that was abandoned about 1960. On the grazed site the vegetation is extremely rich in species. This vegetation type was formerly widespread, but nowadays it is rare and therefore it is important to try to conserve examples of it. In total, 80 0.1 m2 quadrates distributed at random within 4 homogeneous plots were investigated. The species composition and the cover, the height of the vegetation, the position on a tussock or in a depression and the amount of litter were recorded. The cover data were ordinated (PCA). The differentiation between tussocks and depressions and the effects of ceasing grazing were clearly separated. The connections between the vegetation and the position of the quadrat, grazing intensity etc. were investigated. The vegetation of the ungrazed parts had become dominated by Filipendula ulmaria and Carex disticha; on an average there were 5.5 species/0.1 m2. The grazed quadrats contained three times as many species and showed much higher spatial variation, important species being Carex panicea, C. flacca, Molinia caerulea, Festuca ovina, Potentilla erecta, Centaurea jacea and Serratula tinctoria.

Energy content of water- and bog-plant associations in the region of Valdivia (Chile)

Abstract: Mapping the vegetation of the littoral zone of different types of aquatic habitats in the region of Valdivia (Chile) submerged Egerietum densum, the emergent Sagittario-Alismetum and the Scirpetum californiae were found. In the littoral zone of the banados (i.e. lakes) formed by inundation after subsidence the submerged Egerietum densum, the floating-leaved Polygono-Jussiaetum and the emergent Juncetum procerii; the analyzed pond of Mehuin contained the Callitrichetum stagnalis chilensis and the artificial ponds close to La Union the Lemno-Azolletum. The caloric values of 18 hydrophytes showed a decline from the large emergent hydrophytes (3 818 cal/g) to the submerged (2 907 cal/g) and there was also a decrease from the free-floating (3 652 cal/g) to the floating-leaved (3 364 cal/g) and to the submerged plants. In the most eases high caloric values correspond to a high content of lignin (large emergent hydrophytes) or lipids (floating-leaved plants).

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

Abstract: 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.

Some applications of principal components analysis in vegetation: Ecological research of aquatic communities

Abstract: Several recently published studies (Nichols 1977, Feoli 1977, Noy-Meir & Whittaker 1977) have made a fundamental contribution to clarify certain misunderstandings that have been linked to the application of PCA and the interpretation of its results. It can be concluded that with certain options such as data transformation, standardization of variables, different similarity measures, and axis rotation, PCA is ecologically appropriate. Nichols (1977) discussed three important aspects of PCA