Floristic Sampling Research Articles

Vegetação em afloramentos rochosos na Serra do Sincorá, Chapada Diamantina, Bahia, Brasil

The Chapada Diamantina, which represents the northern portion of the Espinhaço Range, is characterized by a mosaic of caatinga and cerrado vegetation, diverse forests types, and principally “campos rupestres”. Its flora is rich in characteristic species, including many endemics. Vegetation of the Chapada Diamantina has been heavily altered by several anthropogenic factors making its conservation urgent. This work was designed to aid in the elaboration of a management plan for the Chapada Diamantina National Park. It deals with the floristic composition and structural aspects of vegetation growing on rock outcrops situated between 400-500 m a.s.l. Four areas (12º35’S and 41º23’W) with a high proportion of exposed rock surface were chosen for detailed examination, and four 10 x 10 m plots were randomly selected for floristic sampling in each of these exposed areas. Each of the four 10 x 10 m plots was further subdivided into 25 2 x 2 m subplots in order to estimate species coverage. We found 57 species of vascular plants distributed among 27 families, including eight monocotyledons, 18 eudicotyledons and one monilophyte. Although the eudicotyledons had the highest numbers of species, the monocotyledons demonstrated the highest coverage. The most abundant species was Vellozia punctulata Seub., which mainly occurred in dense stands. The rock outcrops studied demonstrate similarities with the “campos rupestres”, in terms of the richest families, the most abundant species, and life forms (hemicryptophytes, nanophanerophytes and chamaephytes). Similarity analysis between the 10 x 10 m plots demonstrated groups related to the numbers of species present.

Filtering processes in the assembly of plant communities: Are species presence and abundance driven by the same traits?

AbstractQuestion: Is the response of plant traits to environment at the community level similar when considering species abundance and when considering species presence only?Location: Mountain grasslands, central Argentina.Methods: We used data from 57 floristic samples, ordinated through DCCA along moisture and grazing gradients combined with trait values from 85 species (plant height, leaf area, leaf thickness leaf toughness and SLA). For each sample, we calculated the weighted average (considering species abundance) and the simple average (considering only species presence). Through multiple regressions we analysed how each average (dependent variable) responded to moisture and grazing (DCCA scores along Axes 1 and 2, respectively, as independent variables).Results: Weighted averages of all traits were significantly associated to both gradients, while simple averages did not always respond. In some cases the responses followed similar but weaker trends than the responses of weighted averages, but in other cases these responses were qualitatively different. Traits more associated with size (plant height, leaf area, leaf thickness) responded more consistently (similar trends for both averages) to grazing than to moisture, while traits more associated with plant resource acquisition (SLA, leaf toughness) responded more consistently to moisture than to grazing.Conclusion: The trait values and combinations which determine the probability of species presence are not necessary the same as those which determine their probability of becoming abundant. To understand community assembly rules, both species presence and species abundance should be taken into account as the result of different, although closely linked, filtering processes.

Filtering processes in the assembly of plant communities: Are species presence and abundance driven by the same traits?

Question: Is the response of plant traits to environment at the community level similar when considering species abundance and when considering species presence only? Location: Mountain grasslands, central Argentina. Methods: We used data from 57 floristic samples, ordinated through DCCA along moisture and grazing gradients combined with trait values from 85 species (plant height, leaf area, leaf thickness leaf toughness and SLA). For each sample, we calculated the weighted average (considering species abundance) and the simple average (considering only species presence). Through multiple regressions we analysed how each average (dependent variable) responded to moisture and grazing (DCCA scores along Axes 1 and 2, respectively, as independent variables). Results: Weighted averages of all traits were significantly associated to both gradients, while simple averages did not always respond. In some cases the responses followed similar but weaker trends than the responses of weighted averages, but in other cases these responses were qualitatively different. Traits more associated with size (plant height, leaf area, leaf thickness) responded more consistently (similar trends for both averages) to grazing than to moisture, while traits more associated with plant resource acquisition (SLA, leaf toughness) responded more consistently to moisture than to grazing. Conclusion: The trait values and combinations which determine the probability of species presence are not necessary the same as those which determine their probability of becoming abundant. To understand community assembly rules, both species presence and species abundance should be taken into account as the result of different, although closely linked, filtering processes.

Delving into the Datasets II: ‘CORVEG’ Site-based Floristic Data in Queensland

The collection and databasing of information on species distributions ultimately shapes our ability to conserve and manage biota. Retrospective analysis of trends provides a means to assess the utility of databases for such purposes. This article analyses the Queensland Herbarium's site-based floristic dataset, CORVEG, using data from the South-east Queensland Bioregion. Despite the limited geographical extent of this study, the issues considered are relevant to all taxa-based dataseis. Analysis showed significant differences (P < 0.01) in dataset completeness between recorders, the number of recorders, sampling level, sampling floristics and sampling period. Clear improvements in data and a corresponding decrease in the amount of missing data were evident in the past decade, apparently as a consequence of more explicit sampling protocols. Examination of species richness trends revealed that sites with missing sampling information were of a level comparable to those sites subject to detailed floristic and site sampling for eucalypt and rainforest vegetation types. This highlights the need for complete and consistent records when databasing information. The results demonstrate ongoing improvement in the CORVEG dataset. To build on these gains, it is recommended that greater consideration is given to the current and future uses of such data, including the implementation of a stratified network of permanently marked plots serving multiple biodiversity research and management objectives.

Richesse et diversité floristique de la suberaie de la Mamora (Maroc).

RÉSUMÉ. Richesse et diversité floristique de la suberaie de la Mamora (Maroc). L’étude vise la quantification de la richesse et de la diversité floristique de l’écosystème à chêne - liège de la forêt de la Mamora sur la base de transects et relevés floristiques répartis selon un échantillonnage stratifié et systématique dans différentes formations végétales préalablement distinguées. Les résultats montrent que l’écosystème renferme 62 familles, 261 genres, 408 espèces, sous-espèces et variétés. 35 taxons sont très rares et 29 rares. 18 taxons sont endémiques, 1 très rare et endémique et 4 rares et endémiques. L’étude a, par ailleurs, permis de révéler la disparition totale de Erica arborea et E. scoparia de cet écosystème et de définir le spectre biologique de la région d’étude qui se caractérise par une nette dominance des thérophytes (50.5%).Mots clés. Quercus suber, richesse, diversité, Mamora, Maroc.ABSTRACT. Floristic richeness and diversity of the Mamora’s Cork Oak forest (Morocco.) The survey aims to quantify the floristic richeness and diversity of the Mamora’s forest oak-cork ecosystem on the basis of transects and floristic samples distributed according to a stratified and systematic sampling in the different plant formations previously distinguished. The results show that the ecosystem contains 62 families, 261 genders, 408 species, subspecies and varieties : 35 very rare taxa , 29 rare taxa ; 18 endemic taxa, 1 very rare and endemic taxa and 4 rare and endemic taxa. The survey has, otherwise, permitted to reveal the total disappearance of Erica arborea and E. scoparia from this ecosystem and to define the biological spectrum of the studied region, wich is characterized with a clear dominance of therophytes (50.5%).Keys words. Quercus suber, richeness, diversity, Mamora, Morocco.

Diversidade florística de plantas vasculares no município de Januária, Minas Gerais, Brasil

The vegetation in north Minas Gerais State is poorly known, and for some authors it is the southern limit of natural occurrence for ‘carrasco’ and ‘caatinga’ species. Floristic sampling was made in different areas of Januária municipality, Minas Gerais, including physiognomies of ‘carrasco’ (tree-shrub ‘caatinga’), deciduous forest, ‘cerrado’, floodable field and riparian vegetation (‘vereda’), besides calcicolous vegetation. Six-hundred-eight species in 114 families were found, the five most diverse families were Fabaceae (87 species), Asteraceae (35 species), Euphorbiaceae (28 species), Bignoniaceae (25 species), and Malpighiaceae (21 species). The sampled vegetation included a diversity of vegetation forms. The most diverse areas were the ‘carrasco’ and the deciduous forest (274 species), secondary vegetation along roads and trails, and pastures (160 species), ‘cerrado’ (105 species), ‘vereda’ (98 species), and calcicolous vegetation and riparian vegetation (78 species each). Compared to other floristic surveys performed in northeastern Brazil, even considering only the woody component (tree and shrubs with 323 species), these results highlight the floristic and physiognomic diversity of the studied area.

Evaluating the adequacy of sampling germinable soil seed banks in semi-arid systems

Quantification of soil seed is an important tool for understanding vegetation dynamics. However, determining adequate sample sizes and sampling regimes is problematic. The literature reports highly variable sample sizes and regimes without any generally applicable standards appearing to emerge. This problem is exaggerated by the heterogeneous and patchy nature of arid and semi-arid environments. Species accumulation curves are commonly used in floristic sampling to plan sampling effort and to evaluate its adequacy. However, the precision of the sample cannot be quantified and it is difficult to determine the number of species missed. We suggest an alternate approach in which a species richness estimator is compared to the actual number of species found. When applied to data collected in a semi-arid region of South-West Queensland, this method gave a good indication of sampling adequacy at large sample sizes. We suggest that this post hoc comparison of the predicted species richness (with coefficient of variation) to the actual number of species found would be useful in all studies reporting seed bank composition. This would allow the reader to evaluate the adequacy of the sampling effort, when judged against the research aims. We also investigated the deployment of sampling effort by examining structured subsets of our data. The results suggest that sampling effort may be optimized by taking fewer samples per transect in any one site, but selecting more transects and sites.

Plant functional traits, herbivore selectivity and response to sheep grazing in Patagonian steppe grasslands

Summary In some ecosystems there is a positive feedback between forage quality and grazing intensity. This involves three components of plant tolerance to grazing: functional traits, herbivore selectivity and response to grazing. We analysed the relationships between these components at species and community levels in Patagonian steppe grasslands. We measured plant functional traits [height, specific leaf area (SLA) and foliar toughness] and estimated sheep selectivity and grazing response indices for 35 plant species. Sheep selectivity indices were obtained from microhistological and species’ availability data, and grazing response indices from species’ abundances in sites with contrasting grazing intensities. We performed correlations and multiple regressions among the three types of variables across the pool of 35 species. To analyse data at the community level, we computed weighted averages of traits and sheep selectivity indices for 34 floristic samples taken from each side of 17 fence lines with contrasting grazing intensities. Correlations between mean trait values and sheep selectivity across the 34 samples, and paired comparisons of those variables between sides of the fences, were performed. Taller plants had leaves with lower SLA and/or higher toughness. Short species of intermediate toughness were selected more often by sheep, while SLA was not related to sheep selectivity. Short species with high SLA increased with grazing, while toughness and sheep selectivity were unrelated to grazing response. At the community level, short swards with high average SLA had high selectivity indices and were more abundant on the most intensively grazed sides of fence lines. Leaf toughness was unrelated to other traits or to sheep selectivity, and showed no significant response to grazing. Synthesis and applications. Intensive grazing can increase the forage value of grasslands by the creation of lawns dominated by tolerant species. However, results from this study showed that some plant species that were avoided by grazers also increased, indicating a potential risk of a shift in composition of grazing lawns towards states of low forage value. This suggests that periodic resting of lawns could be a good management strategy to favour palatable species, thereby minimizing the risk of undesirable shifts in the overall species composition.

Efficient plot-based floristic assessment of tropical forests

The tropical flora remains chronically understudied and the lack of floristic understanding hampers ecological research and its application for large-scale conservation planning. Given scarce resources and the scale of the challenge there is a need to maximize the efficiency of both sampling strategies and sampling units, yet there is little information on the relative efficiency of different approaches to floristic assessment in tropical forests. This paper is the first attempt to address this gap. We repeatedly sampled forests in two regions of Amazonia using the two most widely used plot-based protocols of floristic sampling, and compared their performance in terms of the quantity of floristic knowledge and ecological insight gained scaled to the field effort required. Specifically, the methods are assessed first in terms of the number of person-days required to complete each sample (‘effort’), secondly by the total gain in the quantity of floristic information that each unit of effort provides (‘crude inventory efficiency’), and thirdly in terms of the floristic information gained as a proportion of the target species pool (‘proportional inventory efficiency’). Finally, we compare the methods in terms of their efficiency in identifying different ecological patterns within the data (‘ecological efficiency’) while controlling for effort. There are large and consistent differences in the performance of the two methods. The disparity is maintained even after accounting for regional and site-level variation in forest species richness, tree density and the number of field assistants. We interpret our results in the context of selecting the appropriate method for particular research purposes.

Combined effects of environment and grazing on vegetation structure in Argentine granite grasslands

Abstract. Effects of grazing and environment on vegetation structure have been widely acknowledged, but few studies have related both factors. We made 57 floristic samples in a highly variable landscape of mountain grasslands in central Argentina; 26 sample were in fence‐lines with contrasting vegetation. For each sample, we recorded topographic and edaphic parameters, as well as grazing intensity indicators. Floristic gradients were analysed with DCA and relations with abiotic and grazing‐related variables were detected with DCCA. Floristic axis 1 was explained by edaphic parameters associated to topography, ranging from communities in well drained soils on upper topographic positions to hydromorphic vegetation in poorly drained soils on lower topographic positions. Species richness decreased as soil moisture increased. Floristic axis 2 was associated with present and long‐term grazing indicators, and reflected shifts in vegetation physiognomy and species evenness. Tall tussock grasslands, with low species evenness and evidences of low or null grazing intensity were located at one extreme. Tussocks were gradually replaced by short graminoids and forbs towards the centre of the gradient, as grazing increased, and evenness reached a maximum. In degraded sites with heavy long‐term grazing intensities, short perennial species were replaced by an annual species, and evenness decreased. The magnitude of changes in floristic composition produced by grazing decreased with increasing soil moisture, and vegetation‐environment relationships were stronger in moderate to highly grazed situations than in lightly or non grazed situations.

Combined effects of environment and grazing on vegetation structure in Argentine granite grasslands

Abstract. Effects of grazing and environment on vegetation structure have been widely acknowledged, but few studies have related both factors. We made 57 floristic samples in a highly variable landscape of mountain grasslands in central Argentina; 26 sample were in fence-lines with contrasting vegetation. For each sample, we recorded topographic and edaphic parameters, as well as grazing intensity indicators. Floristic gradients were analysed with DCA and relations with abiotic and grazing-related variables were detected with DCCA. Floristic axis 1 was explained by edaphic parameters associated to topography, ranging from communities in well drained soils on upper topographic positions to hydromorphic vegetation in poorly drained soils on lower topographic positions. Species richness decreased as soil moisture increased. Floristic axis 2 was associated with present and long-term grazing indicators, and reflected shifts in vegetation physiognomy and species evenness. Tall tussock grasslands, with low species evenness and evidences of low or null grazing intensity were located at one extreme. Tussocks were gradually replaced by short graminoids and forbs towards the centre of the gradient, as grazing increased, and evenness reached a maximum. In degraded sites with heavy long-term grazing intensities, short perennial species were replaced by an annual species, and evenness decreased. The magnitude of changes in floristic composition produced by grazing decreased with increasing soil moisture, and vegetation-environment relationships were stronger in moderate to highly grazed situations than in lightly or non grazed situations.

Composición florística de las riberas del río Reconquista y sus alteraciones antrópicas

Floristic composition of riparian vegetation of the Reconquista river and its anthropic alterations . This paper analyses the riparian vegetation of the Reconquista river (Buenos Aires Province, Argentina) and the anthropic alterations which are taking place. Floristic samples were taken at different locations under the Braun-Blanquet´s methodology. The results allow us to divide the river in three sections, from its head waters to its confluence, showing a decrease in helophytic species and an increase in allien ones. These changes are due to the urbanization effects. To solve these problems restoration is needed. This could preserve the ecological balance of the watershed and also increase the aesthetic and recreative value of the studied area.

Modelling floristic species richness on a regional scale: a case study in Switzerland

In this paper a multivariate linear regression model is proposed for predicting and mapping regional species richness in areas below the timberline according to environmental variables. The data used in setting up the model were derived from a floristic inventory. Using a stepwise regression technique, five environmental variables were found to explain 48.9% of the variability in the total number of plant species: namely temperature range, proximity to a big river or lake, threshold of minimum annual precipitation, amount of calcareous rock outcrops and number of soil types. A considerable part of the unexplained variability is thought to have been influenced by variations in the quality of the botanical inventory. These results show the importance of systematic floristic sampling in addition to conventional inventories when using floristic data as a basis in nature conservation. Nevertheless it is still possible to interpret the resulting diversity patterns ecologically. Regional species richness in Switzerland appears to be a function of: (i) environmental heterogeneity; (ii) threshold values of minimum precipitation; and (iii) presence of calcareous rock outcrops. According to similar studies, environmental heterogeneity was the strongest determinant of total species richness. In contrast to some studies, high productivity decreased the number of species. Furthermore, the implications of this work for climate change scenarios are discussed.

Applying a Two‐Stage System to Prioritize Riparian Restoration at the San Luis Rey River, San Diego County, California

AbstractA two‐stage system for selecting stream reaches and riparian communities for restoration was applied to the 80‐km San Luis Rey River below the Lake Henshaw dam in southern California. In the first satge, data from topographic quadrangles and aerial photographs were analyzed to define and classiy reaches. These analyses concluded that (1) 28 km of the river and adjacent floodplain were suitable for second‐stage evaluation of restoration needs and (2) 32 km met criteria for reference conditions at the stream reach scale and should be protected from further impacts. The remaining 20 km of the river and floodplain were considered unsuitable for restoration to reach‐scale reference conditions; individual sites may be restored under existing regulatory review. Second‐stage field sampling provided data on vegetation and floodplain landforms and substrate from more thatn 3000 plots within the 28 km of river and 1120 ha of floodplain selected for further Study. Classification of floristic samples stratified by landform/substrate class indicated six primary riparian communities on the floodplain, some associated with particular floodplain landform/substrate classes and others ubiquitous. Reference conditions for these communities were interpreted from the data. There were two major departures from reference conditions: tree‐dominated communities were less extensive than historic levels and exotic plants had significantly invaded some landforms and communities, displacing natural com‐munities. General goals would include restoration of tree communities and removal of exotics, with further consideration of site‐specific objectives. The results included estimates of the areas by community type re‐quiring restoration. The approach was developed for streams in the semi‐arid western United States, but it may be adapted for use elsewhere.

Applying a Two‐Stage System to Prioritize Riparian Restoration at the San Luis Rey River, San Diego County, California

AbstractA two‐stage system for selecting stream reaches and riparian communities for restoration was applied to the 80‐km San Luis Rey River below the Lake Henshaw dam in southern California. In the first stage, data from topographic quadrangles and aerial photographs were analyzed to define and classify reaches. These analyses concluded that (1) 28 km of the river and adjacent floodplain were suitable for second‐stage evaluation of restoration needs and (2) 32 km met criteria for reference conditions at the stream reach scale and should be protected from further impacts. The remaining 20 km of the river and flood‐plain were considered unsuitable for restoration to reach‐scale reference conditions; individual sites may be restored under existing regulatory review. Second‐stage field sampling provided data on vegetation and floodplain landforms and substrate from more than 3000 plots within the 28 km of river and 1120 ha of floodplain selected for further study. Classification of floristic samples stratified by landform/substrate class indicated six primary riparian communities on the floodplain, some associated with particular flood‐plain landform/substrate classes and others ubiquitous. Reference conditions for these communities were interpreted from the data. There were two major departures from reference conditions: tree‐dominated communities were less extensive than historic levels and exotic plants had significantly invaded some landforms and communities, displacing natural communities. General goals would include restoration of tree communities and removal of exotics, with further consideration of site‐specific objectives. The results included estimates of the areas by community type requiring restoration. The approach was developed for streams in the semi‐arid western United States, but it may be adapted for use elsewhere.

Edaphic variability and floristic structure on Mediterranean grassland slopes

One of the most important characteristics of grassland communities is their strong dynamic nature. This is accentuated in the case of slopes and allows distinctions among well‐differentiated enclaves as regards structure and organization. In relation to slopes, this study first attempts to establish whether the edaphic variables governing the vegetation structure of uplands (exportation sectors) are the same as those governing the vegetation structure on lowlands (deposition sectors). A second aim is to determine whether the apparent similarity between the floristic structure of uplands on granites and on slates, and that of lowlands on granites and on slates, is real. Finally, the issue of which other factors, besides the edaphic variables, might affect the structure of the vegetation is addressed, taking into account the livestock‐raising regime that these communities support. With these objectives, 30 typical Mediterranean slope grasslands (province of Salamanca, Spain) were chosen. Half of these grasslands were situated on granites, and the other half on slates. Floristic sampling and edaphic analyses were carried out on the uplands and the lowlands of each slope. A balanced representation (15 sites in each case) of upland on granites, upland on slates, lowland on granites, and lowland on slates was found. The results show that differences exist between upland and lowland sites as to which edaphic variables are of greater influence, since in the former the granulometric composition of the soil predominates, whereas in the latter organic matter, N and P, are more important. Within a particular topographic position, the sites on granites are always poorer than those situated on slates, which implies greater local diversity (alpha diversity) and less heterogeneity over large spaces. Lastly, despite the great importance of the soil in governing vegetation, grazing, competition for light, and the availability of water may be other factors that determine floristic composition and structure. The difference between the structures of the vegetation on uplands and lowlands basically depends on soil variables. The same is found on comparing communities developed on granites and slates corresponding to the same topographic position, the overall situation being mediated by other environmental factors.

Vegetation changes along a precipitation gradient in Central Argentina

Changes in vegetation along a precipitation gradient in Central Argentina were studied. Floristic sam ples were taken along an east-west transect of about 300 km. Correlation analysis between precipitation and ordination axes was used to provide an environmental interpretation of vegetation variability. Floristic analysis produced an ordination of plant communities from evergreen forests (precipitation > 500 mm) to desert shrublands and therophyte communities (precipitation < 200 mm). Results showed a trend of floristic and structural impoverishment towards the west. There is a replacement of species along the transect and a shift in dominant growth forms. The first ordination axis is significantly, neg atively correlated with annual precipitation.

Estrutura da floresta equatorial úmida da estação experimental de silvicultura tropical do INPA

Analisam a estrutura da floresta equatorial úmida próxima a Manaus, introduzindo a qualidade de fuste na. análise. Utilizam 8 amostras de 20m x 500m para indivíduos com DAP &gt; 20cm, 24 subamostras de 10m x 100m para. indivíduos com DAP entre 5cm e 20cm e 120 subamostras de 2m x 10m para indivíduos com DAP &lt; 5cm. Determinam valores mínimos de 2,6 e 22 amostras para composição florística é de 6,18 e 80 para a abundância em cada fração da floresta. Concluem que a floresta é muito heterogênea, com 324 espécies, 173 gêneros e 57 fiamílias e com grande diferença entre a regeneração e o povoamento adulto. Eschweilera odora, Corythophora alta., Protium apiculatum e Radlkoferella sp. são as espécies mais importantes. A floresta em geral apresenta a estrutura diamétrica regular esperada para florestas nativas devido às espécies do estrato inferior e sub-bosque.

Recent Approaches to the Description and Analysis of Vegetation

In contrast to the informality of Tansley's approach to vegetation description, modern studies have adopted a more scientific and analytical approach. Two main directions of study can be recognized in Britain: first, a classifica- tory approach suggested by M. E. D. Poore which is useful for the primary survey of a large area and is based upon the subjective comparison of numerous, detailed, floristic samples; secondly, a statistical approach which increasingly relies upon the use of fast computers. To date, these statistical methods have proved most useful for detailed investiga- tions of the vegetation of restricted areas. The most important methods are outlined and examples of their application to British vegetation are provided. All methods emphasize the need to treat vegetation as the product of a multivariate system, and most methods seek to express the interrelationships between communities in terms of a multi-dimensional network. This is in marked contrast to the linear treatment of community interrelationships in Tansley's classification. The increased number of multivariate methods available for the detailed analysis of vegetation is a reflection of an overall shift in emphasis, from the provision of classifications which are universally applicable, to the provision of techniques which are designed to serve particular ecological purposes.