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1.
Abstract. In this study we present a new method for predicting the occurrences of species using data from deciduous forests in South Sweden. Complete species lists of vascular plants were compiled from 101 stands and from representative sample plots inside the stands. Soil samples from each stand were collected for determination of pH and nitrogen mineralization. Presence-absence data for species were fitted to the values of four environmental variables - soil moisture, soil reaction (pH), soil nitrogen and light - by means of Linear (Multiple) Logistic Regression (LLR), and Gaussian (Multiple) Logistic Regression (GLR). First, these values were estimated by calculating the weighted averages of Ellenberg indicator values. Second, the estimates for reaction and nitrogen were substituted by the real measurements of pH and mineralized NH4+, keeping the Ellenberg estimates for light and moisture. The models were validated by an independent test data set. In general, the models had high predictive abilities. GLR fitted the species occurrences better to the environmental variables than LLR, but had a lower accuracy of prediction of species occurrence in the stands. The use of soil measurements instead of Ellenberg indicator values did not improve the predictive abilities of the models. The environmental conditions in the stand test set were successfully estimated by using species data from the plots. When using the species lists of the stands instead of plot data, a slightly better predictive ability was obtained. The collection of plot data, however, is easier and less time-consuming. The accuracy of prediction differed considerably between species. 相似文献
2.
Mathieu Rouget David M. Richardson Sandra Lavorel Jordi Vayreda Carles Gracia Suzanne J. Milton 《植被学杂志》2001,12(4):491-502
Abstract. This study explores the determinants of distribution, abundance and regeneration of six Pinus species (P. halepensis, P. nigra, P. pinaster, P. pinea, P. sylvestris and P. uncinata) that occur naturally in Catalonia, northeastern Spain. The aim of this study was to generate accurate predictions of the distribution of each species using simple and readily available environmental variables. We used recursive partitioning and GIS analyses to relate the data base of 10 600 field plots from the Forestry Inventory of Catalonia with abiotic and biotic characteristics of each plot. We present general patterns of distribution, dominance and regeneration for the six species and then focus on P. halepensis, the most abundant pine species in the western Mediterranean Basin. For all six species, the models correctly classified more than 80% of the distribution using abiotic factors, mainly altitude and rainfall variability. Biotic factors such as the basal area of other pine species were necessary to accurately predict patterns of pine species dominance. Biotic factors, especially the basal area of evergreen species (mainly Quercus ilex), were of overriding importance when predicting patterns of seedling occurrence. Potentially important factors such as land use and fire history were of little significance for predicting distribution at the scale of our study. Our models failed to predict accurately which species (and in which numbers) co‐occur with P. halepensis. Factors not included in this study, such as stand age, disturbance (cutting, clearing) and other human‐induced factors, are probably the main determinants of co‐existence patterns. 相似文献
3.
Abstract. Recolonization of two experimentally cleared 9 m2-patches by macrophytes in a former channel of the Rhône River, France, was investigated from May to July 1994. Two patterns of recolonization were recognized: (1) Groenlandia densa, Luronium natans and Potamogeton natans invaded the bare areas by propagation from the adjacent vegetation (border effect); (2) Potamogeton pusillus colonized the disturbed areas at random, apparently independently from the position of nearby clumps. An intermediate recolonization pattern was shown by Callitriche platycarpa, Elodea canadensis, Hippuris vulgaris, Ranunculus circinatus and Sparganium emersum. Species recolonization patterns and associated strategies were related to species traits, particularly vegetative and sexual reproduction. 相似文献
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5.
Abstract. A numerical syntaxonomic study of rupicolous vegetation of the Asplenietalia petrarchae in the Iberian Peninsula is described. The study is based on 37 local tables (OSUs) of different rupicolous communities from limestone cliffs found in the eastern half of the Iberian Peninsula. Three classification approaches were followed: (1) ‘hard partition’ techniques, (2) ‘fuzzy partition’ and (3) ordination partition. In order to find a direct solution, we tried an evaluation system based on the inertia associated with a CCA, Canonical Correspondence Analysis, and its relationships with the inertia of a similar CA, Correspondence Analysis. The most effective solutions were found through spatial partitions, and the best partition was obtained with CA considering five segments per axis. Among the fuzzy partitions the best solution was obtained with two clusters and a fuzziness value of 1.20. The best hierarchical partition was Complete Linkage with Chord Distance as a resemblance function. With the GRID procedure applied to the CA diagram, three different groups were distinguished. The first group is related to the Saxifragion boisseriano-reuterani, including five OSUs from Baetic ranges; the second group is very close to the Cosentinio-Lafuenteion rotundifoliae and includes 11 OSUs from thermo-mediterranean areas; the third group, including 21 OSUs basically related to meso-mediterranean areas, is strongly related to the Teucrion buxifolii. 相似文献
6.
Abstract. The effects of disturbance and microtopography on the organization and dynamics of plant communities were studied in a European salt marsh located in the Bay of Mont St. Michel, France. The existence of seed trapping mechanisms was also tested. The study took place in the lower and middle marsh plant communities dominated by the perennials Puccinellia maritima and Halimione portulacoides, respectively and associated with the annual Suaeda maritima. Three treatments were used in series of plots placed in each community: (1) vegetation removal and root destruction to a depth of 10 cm and refilling, (2) non‐remnant herbicide treatment without vegetation removal and (3) creation of depressions (20 cm deep). These treatments were compared with adjacent control plots. The first year of the experiment showed that the perennials facilitated the establishment of Suaeda by trapping its seeds. Estimation of cover, density and biomass over 5 yr following the disturbances showed that in the first 2 yr Suaeda dominated the disturbed plots. Thereafter Suaeda was gradually eliminated by competitive exclusion after ca. 3 yr in the zone originally dominated by Puccinellia maritima and after 4 yr in the zone occupied by Halimione portulacoides. Depressions constituted refuge habitats for Suaeda by limiting competition with the perennials but also led to a high risk of mortality with temporal fluctuations in density. Despite a period of investigation limited to 5 yr, our study demonstrated that natural disturbances of various types occurred and influenced the dynamics of Suaeda, Halimione and Puccinellia. We deduced that natural disturbances and microtopography are responsible for the maintenance of the habitat in a state of non‐equilibrium by favouring the establishment of both spatial and temporal environmental heterogeneity. These conditions appear to be particularly favourable for the maintenance of annual species such as Suaeda maritima. 相似文献
7.
Abstract. We studied the vegetation distribution in eight landscape types distinguished along an altitudinal gradient in the Trans‐Himalayan region of Ladakh, India. The point‐intercept method was used for vegetation sampling. Six plant communities were distinguished by cluster analysis. Of these 6 communities, three communities were dominated by shrub species. Table lands are the landscape type with the highest species diversity followed by undulating areas and river beds. Most plant species were restricted to one landscape type. 相似文献
8.
Abstract. A small-scale restoration experiment concerning a species-rich calcareous grassland was conducted over a 7-yr period. 20 yr of abandonment (1971-1990) resulted in both a strong reduction of the number of species and an absolute dominance of the shrub Crataegus monogyna and the grass Brachypodium pinnatum - which contributed 98% of the above-ground herb phytomass. The plot (3 m x 6 m) was cleared in September 1990 and thereafter yearly mown in autumn. Small soil seed bank samples were taken immediately after clearing and again in the autumn of 1996. The inner part of the plot showed a reduced soil seed bank compared to the plot underneath the vegetation outside the plot in 1990. Six years later an increased number of seeds in the soil in this inside area could be recorded mainly in the upper soil layer, although the amount was only 40% compared to the outside or control area. Ca. 20% of the species present in the restored vegetation were recorded in seed traps during the main seed dispersal period in 1997. Restoration of high species richness in the plot was a fast process during the first few years: from seven species in 1990 towards 39 three years later. This was significantly faster than the restoration process of the calcareous grassland at the same slope 20 yr earlier. This was probably due to the increased size of the community species pool at the site as a result of appropriate management during the last decades. Relative species number increase was highest at the largest scale during this experiment, viz. at the total plot area. The success of restoration of species-rich, dry grassland vegetation largely depends on the interaction between several conditions, e.g. seed availability, either originating from the seed rain or soil seed bank, favourable germination conditions and a successful development to a mature, seed producing individual. Germination and establishment strongly depend on suitable vegetation structure as a result of sustainable management. 相似文献
9.
Question: Are growth form and dispersal-mode replacement during vegetation succession in semi-arid Mediterranean conditions affected by the starting quality of the substrate and by site aspect? Location: Central-western Spain. Methods: We monitored successions on three waste materials left after uranium mining: unbroken waste, broken waste and wastes amended with a sandy material (Arkoses); both north and south aspects were also studied on each substrate. Results: The substrate starting quality had the greatest influence on spontaneous succession, separating the poorer quality substrates (broken and unbroken wastes) from the better ones (Arkoses) and two reference communities (Topsoil and Dehesa). The importance of aspect was confirmed then within each substrate type. Most species with a short life span (mostly annuals and a few biennials), together with some woody species on Arkoses, showed no response to age (years following the deposition of new soil). Others short-lived species declined over time on the poorer wastes but not on the better Arkoses. There was a tendency for life form replacement (from thero-phytes to hemicryptophytes) during succession only on the poorer-quality substrates. No dispersal-mode replacement sequence was found. Conclusion: Improving the abiotic conditions of the substrate had a great effect on vegetation succession, but this effect was modified by aspect. Aspect took longer to induce differences in floristic composition on the poorer substrates, where succession was slower. Some trends in species responses to successional change were found by considering species traits, particularly life-form. 相似文献
10.
Abstract. The community structure of a species-rich grassland was investigated at a small spatial scale (0.001 m2), to determine whether evidence suggesting assembly rules could be found in temporal or spatial variation in either species richness or guild proportions. The community was alvar limestone grassland on the island of Öland, Sweden. Three sites were sampled: two lightly grazed, the other recently ungrazed. Plots with and without fertilizer were compared. Evidence was sought for restriction on the ability of species to co-occur within a limited spatial area. Restriction due to a limited number of niches available,‘niche limitation’, could be manifest as lower variance in quadrat richness than expected under a null model (i.e. RVr, the ratio of observed: expected variance in richness, would be < 1.0). In several cases, RVr values were significantly < 1.0, even using a patch model to allow for possible spatial variation in the environment. Low RVr values were found only at the smallest square quadrat size, 10 cm2. On Fertilized plots in the years immediately after application of fertilizer, low RVr could not be demonstrated. Explanations of low RVr other than niche limitation are considered, such as environmental heterogeneity (present and/or historical) and limitations to the co-occurrence of individual plant modules. Assembly rules based on guild membership were sought by looking at the variance across quadrats in the proportions of species from morphological guilds. An assembly rule would be seen as relatively constant proportion, estimated via RVgp, the ratio of observed: expected variances in guild proportions. Significant guild proportionality was found in some cases. There was no evidence of guild proportionality in the years after the application of fertilizer. The significant effects in RVr were more numerous than expected on a random basis, though not observed in every site in every year. Similar trends were seen in RVgp. At the space/time scales examined, the species in a plant community may be constrained by assembly rules only intermittently, e.g. when resources are more limiting (Wiens 1977). Under this concept, when competition is relaxed, such as following fertilizer application, there is a temporary microhabitat ‘waterhole’ in which more species can coexist, and the assembly rules break down, at least temporarily whilst the species composition adjusts. There was some indication of a return to more deterministic community structure four years after fertilization commenced. Variants of van der Maarel's Carousel model were tested. A Niche-limited Carousel Model (i.e. a model in which there is some limitation in the number of species that can occupy a microsite) would imply restricted variation in richness through time for a single quadrat (temporal RVr). Overall differences between years in species richness were demonstrated, and their effect removed; after this adjustment there was support for the Niche-limited Carousel Model. The extent of this limitation varied between sites. There were also consistent differences between quadrats in species richness. There was little evidence for constancy of guild proportions through time. The site that showed the strongest community structure in time and space, least year-to-year variation in mean species richness, and least response to fertilizer perturbation, is that on the shallowest soil. Possibly the thin soil results in greater resource limitation, supporting suggestions that assembly rules are stronger when resources are more limited. 相似文献
11.
Abstract. The vegetation in a grassland area in the prefecture of Kilkis (N. Greece), known for its surface Cu-mineralization, was studied. 43 quadrats were established along a transect through an area where the vegetation formed patches of different size. Cover-abundance and frequency estimates for all species were made. Normal Association Analysis revealed five quadrat groups characterized by Trifolium scabrum, Linaria pelisseriana, Anthoxanthum ovatum, Gypsophila muralis and Minuartia hirsuta ssp. falcata. 43 soil samples were analysed for pH, organic C, CaCO3, total content of Fe, Zn, Pb, Cu, Mn, Ca, Mg, K, Na and soil texture. From a discriminant analysis performed on soil data five soil groups resulted, which are highly related to the five vegetation groups. Thymus sibthorpii, Minuartia hirsuta ssp. falcata and Rumex acetosella are the most important taxa with respect to physiognomy and patchi-ness of the vegetation. The number of species in each group of quadrats is affected by the relative favourableness or severity of the soil conditions. Metal contents, mainly Zn, Cu, Mg and Na, and soil texture are considered to be among the main factors controlling the structure and physiognomy of the vegetation. 相似文献
12.
Abstract. This study explored the validity of three responses of vegetation to increased soil erosion: reduction of vegetation cover, number of species and reduced substitution of species. 201 relevés, including edaphic and geomorphological data, were surveyed in the intensely eroded Eocene marls of the Prepyrenees (NE Spain). Changes in plant species’ presence in relevés from different degradation stages were compared. The level of vegetation degradation was defined as the total phanerogam cover which, in the studied area, was correlated to the degree of soil erosion. The considered trends were validated. Reduction of phanerogam cover and species number were gradual from low to high‐eroded areas. Vegetation degradation explained 48% of the species number variance. In the later stages of degradation a significant substitution of species was not observed, only a lower frequency of occurrence of several species that appeared in the whole set of relevés. Through the process of degradation, 47% of species displayed significantly reduced frequencies as degradation increased, none showed a significant increase in frequency. It is concluded that there are no characteristic species in these plant communities that survive in the severely eroded marls. Among the few species that had increased in frequency, most only colonised favourable micro‐environments. 相似文献
13.
Abstract. Data on succession were collected from 15 seres starting on bare ground in man-made habitats (i.e. sites disturbed by various mining activities, bulldozed sites, ruderal urban sites, the exposed bottom of a destroyed water reservoir, and abandoned fields), all in the western part of the Czech Republic, Central Europe. The period for which the data on succession were available ranged from 12 to 60 yr. 56 species reaching dominance in some period of succession were selected (the criterion being: at least 25 % cover in at least one year in any sere); they were compared for biological and ecological traits with other species participating in the seres (167 species with at least 1 % cover in at least one year in any sere), and with the Central European flora as a whole. Significant differences between the species dominating in succession and others were found for the following traits: life form, life strategy, pollination mode, and ability of lateral spread. Dominant species differed from the regional flora in distribution of life strategies, pollination mode and immigration status. The results suggest that an ‘ideal successional dominant’ is a tall, wind-pollinated plant, often a geophyte capable of intensive lateral spread, requiring high nutrient supply and sufficient site moisture. The set of traits contributing to achieving dominance by a species in human-made habitats includes both features occurring independently of phylogenies (life strategy, pollination mode, plant height, moisture demands) and those which dominant species probably share due to their common ancestors (nutrient demands, capability of extensive lateral spread). 相似文献
14.
Abstract. The floristic effects of river‐borne litter that accumulates in riparian zones may vary in space and time depending on variations in mass and particle size of the deposited litter. To analyse the effects of litter mass and size we applied differentsized litter (natural uncut pieces and powder) to riparian vegetation at different quantities. Vegetation responses were analysed after one season at the community level (total biomass or richness for all species) and species traits (biomass or richness for groups of species). At the community level uncut litter, but not powder, reduced species richness and both uncut and ground litter reduced above‐ground biomass. At the species trait level uncut litter had a stronger effect than powder on species richness and biomass. The only positive effect of litter addition was that powder increased graminoid species richness. The topsoil conditions indicated that the major impact of deposited, river‐borne litter was that it acted as a physical barrier directly preventing established plants from penetrating the litter layer and reducing light and soil temperature. 相似文献
15.
Abstract. In a species-rich mountain grassland in the Krkonosse Mts., Czechoslovakia, data from four permanent plots of 50 cm x 50 cm were recorded annually from 1985 to 1990 to study the spatial dynamics of the species. Plots were divided into 15 x 15 subplots and the number of vegetative units of all plants within each subplot was determined. There was not much net change at the plot level, but the subplots were very dynamic. Two aspects of the spatial dynamics of the species were followed: (1) persistence, i.e. the tendency of the species to remain in the same subplot, and (2) long-distance spreading, i.e. movement to subplots beyond the immediate neighbourhood. Species differed widely in their persistence and longdistance spreading and were classified into mobility types: long-range guerrilla, short-range guerrilla, phalanx and 'sitting’. The mobility types were, to a certain extent, correlated with the growth form of plants, but some species of one growth form showed different types of small-scale dynamics and some species with different growth forms had the same spatial dynamics. 相似文献
16.
Abstract. Epiphytic and epixylic lichens were surveyed on 15 1-ha plots in mature Picea abies-dominated boreal forests in southern Finland. The sample plots were classified into three groups according to the age of the dominant tree stand and recent signs of cutting: (1) early mature managed, ‘EM’ (95 -109 yr), (2) late mature managed, ‘LM’ (126 - 145 yr) and (3) old-growth, ‘OG’ (129 - 198 yr). Two data sets on epiphytic and epixylic lichens were recorded from each plot: (1) species on basal trunks and branches of Picea abies and (2) species on all available woody substrates, including basal parts of all tree species, saplings, snags, logs and stumps. 142 epiphytic and epixylic lichen species were found, of which 83 (58%) occurred on P. abies. Mean total numbers of species per sample plot were 69 in EM, 78 in LM and 88 in OG plots, species number on P. abies were 47, 56, and 54 respectively. The LM plots had lower species numbers than OG plots, mainly due to the lack of old Populus tremula trees, but they had higher species number than the EM plots mainly due to the higher age of Picea abies. Differences in species composition, both within and between the three groups, were small. The results suggest that the epiphytic and epixylic lichen diversity in a managed stand can be increased by prolonging the rotation of the stand to >120 yr and by increasing the diversity of habitats in the stand. 相似文献
17.
Abstract. The sequences of macrofossils in 17 cores from two Tasmanian valley Sphagnum peatlands reveal a wide variety of successional pathways. The most common sequence is from restiad mires to Sphagnum mires to heath. While it is impossible to conclusively separate allogenic and autogenic influences, it seems likely that the rapid rate of change recorded in the upper levels of the cores may, in part, reflect recent climatic change. Most other changes recorded in the core are likely to be predominantly autogenic. 相似文献
18.
Abstract. In contrast to populations of most dioecious Silene species (which usually are female-biased), populations of Silene otites have been frequently reported to be male-biased. We describe sex ratio variation in 34 natural S. otites populations in Central Germany in relation to vegetation cover, population size and fungal infection. The overall sex ratio was unbiased in 1994 and only slightly male-biased in 1995. Sex ratio varied among the populations from 26.6 % to 72.6 % females. The sex ratio of small populations varied strongly due to stochastic processes. Furthermore, we found that populations in habitats with high vegetation cover contained a higher percentage of females. Hermaphroditic plants, theoretically, could increase male bias as they only produce male or hermaphroditic offspring. Their frequency in the populations, however, was far too low to affect sex ratio. In 1994 12.1 % and in 1995 17.0 % of the plants were infected by the smut fungus Ustilago major. Disease incidence in the population was not related to sex ratio, suggesting equal susceptibility of males and females. The sex ratio of partially infected plants did not deviate from the population sex ratio, both under field conditions and in a greenhouse laboratory experiment. The results suggest that the frequently reported male bias in Silene otites populations is not a general pattern, but is mainly caused by environmental conditions. 相似文献
19.
Abstract. The alien plant species and the ecological factors that facilitate their invasion to a coastal strip in the Baix Camp region (Tarragona, NE Spain) were studied. A detailed inventory of the area showed that 20% of the plant species, most of them from the American Continent, were aliens, many of which were strongly invasive. At the habitat level, the relationships between the invasive behaviour and a number of autecological, ecological and habitat variables were analysed by means of logistic analyses. In the best model five variables were related to alien plant invasions: climatic affinity, disturbance of the invaded habitat, route of introduction, soil moisture during summer, and life form. To elucidate the environmental factors that could be responsible for alien plant invasions at a regional scale, the number of alien taxa and the environmental features at 13 localities of the western Mediterranean area were analysed. The warm lowlands, subjected to low annual rainfall and high population density, exhibited the greatest reception capacity for alien plants. It is concluded that various specific environmental features – high mean temperatures, the abundance of riparian systems, the existence of biotopes with favourable water balance which harbour a great richness of alien species and the high human pressure to which the enclave is subjected, combined with the ecological requirements of the alien species and certain species attributes (biotype) can interact at different scales and have caused the over‐representation of alien plants. 相似文献
20.
Abstract. Old-field plots used for a study of succession in Mediterranean France were revisited after 12–14 yr. Our aims were: (1) to verify if predicted patterns of species richness, turnover and composition are confirmed; (2) to compare the development in disturbed plots with that in undisturbed ones; (3) to discuss the impact of management changes. In undisturbed plots species richness and turnover decreased with successional age. Floristic composition changed in a way consistent with the predicted successional development in most plots. Therophytes decreased and phanerophytes increased; anemochorous species decreased and endozoochorous species increased, as expected. In plots disturbed since the first analysis richness decreased with successional age, but generally remained higher than in undisturbed plots. Floristic composition, species turnover and an increase in therophytes indicated changes towards younger successional stages. Thus, disturbance changed succession but not much. This is probably linked with the regeneration abilities typical of mediterranean species, e.g. resprouting. At the landscape scale, richness did not change and species turnover was low. The plots studied were situated in two distinct locations. One had not been disturbed between the two observation periods, while the other is a mosaic of undisturbed and disturbed sites. Observations fitted predictions much more closely at the undisturbed location. We conclude that permanent plot studies are powerful in identifying successional trends and can also provide additional insights into the effects of disturbance some of the mechanisms underlying the dynamics of diversity. 相似文献