Variation In Floristic Composition Research Articles

Impacts of climate change on semi-natural alpine pastures productivity and floristic composition

Climate change impact on pasture floristic composition needs to be carefully assessed, given its key role for the resilience of pastoral systems and related ecosystem services. Nevertheless, variations in floristic composition are rarely taken into account in climate change impact studies. Here, we used the plant community model CoSMo to simulate future dynamics of biomass accumulation and floristic composition for high-altitude semi-natural alpine pastures. Dedicated multi-site field activities were conducted to collect data for model calibration. Simulations were run for four 20-year climate scenarios centered on 2040, resulting from the combination of two general circulation models (GISS-ES and HadGEM2) and two representative concentration pathways (RCP4.5 and RCP8.5). Results highlighted the capability of CoSMo to successfully reproduce the productivity and floristic composition of semi-natural pastures, modeling efficiency and R2 being higher than 0.90 for aboveground biomass accumulation and relative abundance of species. CoSMo simulated an overall positive effect of increasing temperatures on pasture productivity (+ 10.7% on average), due to higher biomass accumulation rates and longer growing seasons. However, these benefits were highly heterogeneous among the monitored pastures (ranging from − 2.5 to + 16.2%), because of differences in floristic composition and in species-specific thermal requirements that led to complex, non-linear reactions to climate variations. A negative impact of climate change was simulated for grazing value (− 11.1% on average), due to the higher suitability to future conditions of Nardus stricta, which has low grazing value compared to other species. Our results highlight that floristic composition should be explicitly considered while assessing climate change impacts on semi-natural pasture productivity and connected ecosystem services.

Multi-environment factors dominate plant community structure and diversity in an ombrotrophic bog: The water level is the main regulating mechanism

Understanding the relationship between vegetation and the environment is critical to manage bog ecosystems. However, information on how environmental factors influence the species composition and diversity in the ombrotrophic bog of Northeast China is lacking. Here, we investigated species compositions and environmental characteristics (water level, water conductivity, soil moisture content, bulk density, pH, organic carbon, total nitrogen, total phosphorous) from five sample sites along the water level gradients (the water level is below the surface, near the surface, and above the surface). Plant communities presented a patchy distribution pattern along the environmental gradients and could be divided into five types of communities. Moreover, the distribution of plant communities was mainly determined by water level, water conductivity, soil moisture content, pH, and organic carbon, which significantly explained 32.2%, 30.9%, 29.7%, 29.1%, and 22.5% of the variation in floristic composition. Among these factors, water level was the dominant factor influencing the distribution of plant communities. The partial least squares path model analysis showed that water level could influence plant diversity through different pathways, which could directly affect plant diversity and indirectly affect by changing water chemistry and soil properties. Additionally, soil pH contributed most to the indirect effects of water level on plant diversity. Thus, this study highlighted the high dependence of plant communities on water level and environmental factors driven by water level in ombrotrophic bogs, which provided some valuable implications for regional vegetation restoration and plant community stability.

Biodiversity conservation and carbon storage of Acacia catechu willd. Dominated northern tropical dry deciduous forest ecosystems in north-western Himalaya: Implications of different forest management regimes

Sustainable forest management is the key to biodiversity conservation, flow of resources and climate change mitigation. We assessed the impact of various forest management regimes (FMRs): legal felling series [(reserve forest (RF), demarcated protected forest (DPF), un-demarcated protected forest (UPF), co-operative society forest (CSF) and un-classed forest (UF)] on biodiversity conservations and carbon storage in Acaciacatechu Willd. Dominated northern tropical dry deciduous forest ecosystems in Nurpur Forest Division of north-western Himalaya, India. The study revealed significant variations in floristic composition, biodiversity indices, population structure and C storage potential among different forest management regimes. The RF and DPF were found to be rich in species diversity and richness whereas the Simpson dominance index for trees and shrubs was maximum in UF and UPF, respectively. The diversity of understory herbs were higher in CSF and UF. The maximum density of seedlings, saplings and poles were recorded in RF followed by DPF and UPF, whereas the minimum density was found in CSF. The tree C density (69.15 Mg C ha−1) was maximum in UF closely followed by RF; whereas the minimum was recorded in CSF (33.27 Mg C ha−1). The soil C density was maximum in RF (115.49 Mg C ha−1) and minimum in CSF (90.28 Mg C ha−1). Similarly, the maximum total ecosystem C density was recorded in RF (183.52 Mg C ha−1) followed by DPF (166.61 Mg C ha−1) and minimum in CSF (126.05 Mg C ha−1). Overall, UF management regimes were shown to have a greater capacity for C storage in vegetation, whereas strict FMRs, such as RF and DPF, were found to be more diverse and have a higher soil and ecosystem carbon density. The study established that in the midst of climate and biodiversity emergencies, it is urgent to maintain, protect and strengthen the network of RF and DPF FMRs for biodiversity conservation, climate change adaptation and mitigation.

Seed rain in two areas with different relief types in a tropical rainforest

Seed rain participates in species enrichment during the natural regeneration of terrestrial ecosystems, as this ecological process promotes gene flow and the maintenance of forest biodiversity. However, few studies assessed variations in seed rain related to environmental heterogeneity inside forests. We studied the influence of relief (flat or slope areas) on the seasonal and monthly variation in density, floristic composition, and richness of the seed rain in an urban fragment of Atlantic Forest. We carried out the present study in Rain Tropical Forest, Northeastern Brazil. We selected two areas within the fragment: one with flat relief and the other on a slope. In each relief type we set up 20 0.25-m2 seed collectors, in a total of 40 units, to quantify seed rain. After ten months of study, we counted 9,474 seeds: 8,061 in the flat area and 1,413 in the slope area. There were significant differences in dispersal syndromes and plants habit between relief types. The seed density in the flat area differed between seasons and the species richness varied seasonally in both areas. There were variations in floristic composition between seasons in the flat and slope areas. Seed density was higher in December and January in the flat area. Differences in seed rain suggest that it is influenced by spatial heterogeneity and climate seasonality, and that the areas with different kinds of relief are important for the biodiversity conservation.

Regeneration status and soil site characteristics of Spruce (Picea smithiana Wall. Boiss) dominated forest along altitudinal gradient in North Indian Himalaya

The present study carried out at three altitudes in Daksum range of Anantnag Forest division aimed to study the variation in floristic composition, community structure, regeneration status, soil characteristics and soil seed bank of Spruce dominated forests. A total of 47 plant species belonging to 41 genera and 29 families were reported. The number of species decreased with increasing altitude. Abies pindrow, Acer caesium and Pinus wallichiana were main tree associates of Picea smithiana. The regeneration of Spruce at all the sites was low and did not show any definite trend along the altitudinal gradient. There was a decrease in availability of OC, N, P, K, Fe and Zn with increase in soil depth at all the three altitudes. However, soil pH showed the reverse trend. There was an increase in availability of OC, N, P, K and Zn while decrease in pH and available Fe in soil with the increase in altitude. The viability of soil seed bank of spruce was found to be very low (15.36 to 18.18%). The study is a pioneer in this region in many aspects and hence shall be a benchmark for further management and conservation of this important species.

Variation in floristic and trait composition along environmental gradients in the herb layer of temperate forests in the transition zone between Central and SE Europe

Species- and trait-environment linkages in forest plant communities continue to be a frequent topic in ecological research. We studied the dependence of floristic and functional trait composition on environmental factors, namely local soil properties, overstory characteristics, climatic parameters and other abiotic and biotic variables. The study area comprised 50 monitoring plots across Slovenia, belonging to the EU ICP Forests monitoring network. Vegetation was surveyed in accordance with harmonized protocols, and environmental variables were either measured or estimated during vegetation sampling. Significant predictors of species composition were identified by canonical correspondence analysis. Correlations between plant traits, i.e. plant growth habit, life form, flowering features and CSR signature, were examined with fourth-corner analysis and linear regressions. Our results show that variation in floristic composition was mainly explained by climatic parameters (mean annual temperature, mean annual precipitation), soil properties (pH) and tree layer-dependent light conditions. Trait composition was most closely related with tree layer characteristics, such as shade-casting ability (SCA, a proxy for light availability in the understory layer), tree species richness and tree species composition. Amongst soil properties, total nitrogen content and soil texture (proportion of clay) were most frequently correlated with different species traits or trait states. The CSR signature of herb communities was associated with tree layer SCA, soil pH and mean annual temperature. The floristic composition of the studied herb-layer vegetation depended on temperature and precipitation, which are likely to be influenced by ongoing climate change (warming and drying). Trait composition exhibited significant links to tree layer characteristics and soil conditions, which are in turn directly modified by forest management interventions.

Revealing floristic variation and map uncertainties for different plant groups in western Amazonia

AbstractQuestionsUnderstanding spatial variation in floristic composition is crucial to quantify the extent, patchiness and connectivity of distinct habitats and their spatial relationships. Broad‐scale variation in floristic composition and the degree of uniqueness of different regions remains poorly mapped and understood in several areas across the globe. We here aim to map vegetation heterogeneity in Amazonia.LocationMiddle Juruá river region, Amazonas State, Brazil.MethodsWe mapped four plant groups by applying machine learning to scale up locally observed community composition and using environmental and remotely sensed variables as predictors, which were obtained as GIS layers. To quantify how reliable our predictions were, we made an assessment of model transferability and spatial applicability. We also compared our floristic composition map to the official Brazilian national‐level vegetation classification.ResultsThe overall performance of our floristic models was high for all four plant groups, especially ferns, and the predictions were found to be spatially congruent and highly transferable in space. For some areas, the models were assessed not to be applicable, as the field sampling did not cover the spectral or environmental characteristics of those regions. Our maps show extensive habitat heterogeneity across the region. When compared to the Brazilian vegetation classification, floristic composition was relatively homogeneous within dense forests, while floristic heterogeneity in rainforests classified as open was high.ConclusionOur maps provide geoecological characterization of the regions and can be used to test biogeographical hypotheses, develop species distribution models and, ultimately, aid science‐based conservation and land‐use planning.

Expansive shrubs: Expansion factors and ecological impacts in northern Ethiopia

Expansive native species have the same ecological and economic consequences as invasive alien species through the reduction of ecosystem goods and services. We assessed human disturbance and environmental factors that are contributing to the expansion of two expansive shrubs, Cadia purpurea and Tarchonanthus camphoratus in Desa’a dry Afromontane forest, northern Ethiopia. We also evaluated their expansion effect on plant species composition, diversity, structure, and regeneration, and herbaceous cover. The forest was stratified into “invaded” and “uninvaded” based on percentage coverage of the two shrubs. Vegetation data were collected from each stratum using 75 nested plots per strata of 20m × 20m, 5m × 5m, and 1m × 1m for adult tree/shrub, sapling, and seedling, respectively. Moreover, data on environmental and human disturbance variables were collected from the main plots. We found that higher cover of the expansive shrubs was related to both human disturbance and environmental variables while some were species-specific. Species richness and diversity of plant species decreased significantly with an increase in abundance of the expansive shrubs. However, evenness did not change significantly with an increase in the abundance of the expansive shrubs. The density, mean diameter, mean height, and mean basal area of the plants decreased significantly with an increase with the cover of the shrubs. The expansive shrubs had a significant negative impact on regeneration and herbaceous cover. This study shows a distinctive variation in floristic composition, diversity, and regeneration status between the invaded and uninvaded communities, which suggests the need to be counteracted by management measures. Converting the underutilized expansive species into use as part of the management option should be given urge attention before it loses its ecological resilience.

Floristic Composition and Structure in Relation to Elevation in the Togo Plateau Forest Reserve in Ghana

Plateau ecosystems are of special scientific and conservation interests as they harbour rich plant diversity and exhibit considerable spatial variability along elevation gradients. In this study, variations in floristic composition and structure in relation to elevation were studied in six-fringed communities Hohoe (HH), Alavanyo (AL), Santrokofi (SA), Akpafu (AK), Bowuri (BO), and Nkonya (NK) of the Togo Plateau Forest Reserve in Ghana to help provide explicit and effective management of this ecological hotspot. A total of 180 plots (each measuring 25m × 25m) were demarcated across the six communities for sampling of trees (DBH measured at 1.3 m above ground ≥10 cm). Smaller nested plots, measuring 5m × 5m and 1m × 1m, were used for sampling saplings (DBH < 10 cm, height > 1.5 m) and seedlings (DBH < 3 cm, height < 1.5 m), respectively. Species identity and abundance and elevation were recorded for each plot. Relationships of elevation gradient with vegetation attributes were analysed using simple linear regression. A total of 281 plant species (164 trees, 60 saplings and 57 seedlings) belonging to 66 families were recorded in the study. Leguminosae, Apocynaceae and Euphorbiaceae were the most dominant families across and along the elevation gradient. Average basal area of trees across the six communities was 44.72 m2/ha (ranged from 57.10 m2/ha at BO to 33.10 m2/ha at AL) whereas the Shannon-Weiner Index (H’) averaged 3.99 (ranged from 4.14 m2/ha at BO to 3.89 m2/ha at AL) and evenness index averaged 0.96 (ranged from 1.00 at BO to 0.92 at AL). The saplings and seedlings showed a similar pattern of composition and structure as the trees. The geographical locations of the study communities, which somehow correspond with different elevations of the plateau (i.e., BO, NK occur in lower elevations, SA, AL in mid elevations and HH, AL in higher elevations), was observed to have marginally influenced the composition and structure of the vegetation on the landscape. The most important trees listed in the study were Ceiba pentandra, Albizia zygia, and Terminalia superba. The saplings were Acacia camerunensis, Microdesmis puberula and Cnestis ferruginea. The seedlings were Chromoleana odorata, Palisota hirsuta and Costus affer. The most important tree species listed were distributed along a broad range of elevations. These results generally demonstrate the high floristic diversity of the Topo Plateau and the influence of elevation gradient on this, which should help in understanding of the composition and structure of several plateau ecosystems in Ghana and elsewhere.

Variations in floristic composition and community structure between disturbed and undisturbed lowland forest in Aklan, Philippines

ABSTRACT Despite the notable plant biodiversity of the Philippines, the country still exhibits increasing anthropogenic activities in many forests of the archipelago that pose a threat to many floral species of the country. Hence, to test the hypothesis that there are differences in plant distributions and diversity between disturbed and undisturbed tropical forest patches, a rapid floristic assessment in Malinao, Aklan was conducted. A total of 106 species were sampled in both sites, with 68 present in the disturbed site, 53 present in the undisturbed site, and 12 present in both. Rarefied species accumulation curves and calculations of Shannon-Wiener Index (H) showed higher species richness and evenness in the undisturbed forest. Analysis of the similarities in species composition using the nonmetric dimensional scaling combined with the statistical test PERMANOVA showed clear significant difference between the two forest categories. In addition, one species (Artocarpus blancoi (Elmer) Merr.) that is classified as “Vulnerable” according to the IUCN was noted. Thus, standard calls for the establishment of priority areas for forest conservation in the country are recommended.

Drivers of floristic variation in biogeographic transitions: insights from the ecotone between the largest biogeographic domains of South America

ABSTRACT Ecological transitions usually represent vulnerable ecosystems and high biodiversity. Investigating their drivers is important from both biogeographic and conservationist perspectives. One of these transitions is situated between the two largest biogeographic domains of South America - the Amazon and the Cerrado. We evaluated variation in tree floristic composition throughout this transition and assessed which factors explain this variation. We used 17,240 records of occurrences of 2,530 tree species from the NeotropTree database. We investigated variation in floristic composition using UPGMA cluster analysis with bootstrap resampling and NMDS ordination, and modeled the distribution of species in relation to environmental and spatial predictors by means of transformation-based Redundancy Canonical Analysis (tb-RDA) and variance partitioning. We found four general floristic groups: 1) flooded forests; 2) white sand dwarf-forests; 3) savannic and dwarf forests; and 4) non-flooded forest types. Floristic variation along the transition was influenced by the environment, especially variables related to fire and soil moisture, and by space, especially variables acting on broader scales. Correspondence between the environmental heterogeneity found throughout the transition and our results demonstrates once again the importance of conserving biogeographical transition zones in general, and the most comprehensive of South America in particular.

After-fire Variations in Floristic Composition at the Cerrado (Brazilian Savannah) Phytophysiognomies in Curvelo, Minas Gerais, Brazil

This study aimed to evaluate the changes in the floristic composition at the Cerrado (Brazilian Savannah) stricto sensu and Cerradão (xeromorphic forest) phytophysiognomies. In the first inventory in 2010, 15 soil plots of 20 × 50 m in the Cerrado stricto sensu (CSS) and 10 soil sample plots of 20 × 50 m in the Cerradão (CD) were separated, and individual samples with diameter at soil height ≥ 5 cm were measured. The second inventory, conducted in 2015, used the same criteria. A fire hit both phytophysiognomies after the first inventory. Species loss and a mortality rate higher than recruitment rate were observed in both phytophysiognomies. Species richness and individual density have been diversified over time. Floristic changes were more intense in CD, with significant alterations between mortality and recruitment rates - the species that disappeared were represented by a few individuals; in the CSS, the changes were not significant.

Relación entre la composición florística y los nutrientes del suelo en comunidades de palmas del Chocó biogeográfico en Colombia y Ecuador

We studied the floristic composition of palm communities and their relation with soil nutrients in two localities of the Chocó biogeographic region to undestand (1) How soil nutrients vary between the two localities? (2) What is the relationship between soil nutrients and palm floristic composition? (3) What are the most important nutrients that explain the variation in floristic composition of palm communities? (4) How the abundance of the most abundant understory and canopy palm species varies along the concentration gradient of the most important nutrients? We established 20 transects (5 x 500 m) and identified all palm individuals of all growth stages. Soil samples were taken at each transect at the beginning, middle and end. Macronutrients (Al, Ca, Mg, K, P) were extracted with the Mehlich-III technique and their concentrations were analyzed by inductively coupled plasma emission spectrometry (ICP-OES). The concentration of nutrients was related to the floristic composition using Mantel, partial Mantel tests, linear regressions and non-metric multidimensional scaling. We found a total of 9158 individuals and 33 species of palms in the 5 ha covered by our transects. Species composition had a positive and significant correlation with soil nutrients (rM = 0.63-0.69) and with geographical distance between transects (rM= 0.71-0.75), whereas the soil nutrients were highly correlated with geographical distance (rM = 0.72). We found a small yet significant relationship between soil fertility and the abundance of undestorey palms, but no relationship with canopy palms. Our results demonstrate for the first time that soils play an important role in the composition of palm communities at local scales in the Chocó region, and that infertile and phosphorus-rich soils have the highest palm diversity.

Environment or management? Relative importance for floristic composition of sub‐Mediterranean hay meadows in Central Italy

AbstractQuestionsWhat are the separate and combined effects of natural and management factors on floristic assemblage in sub‐Mediterranean hay meadows? How are hay meadow dynamics affected by the environment excluding management?LocationCentral Apennines, Italy.MethodsVegetation was studied in 66 hay meadows by random plots, recording four groups of explanatory variables: management, soil, topography, and space. Using partial ordinations, the explanatory variables of the variation in floristic composition and plant traits were divided into sets. Then, to emphasize the relationship between purely environmental variables and vegetation, we considered only the partial ordination executed with soil and topographic variables using management and spatial data as covariables.ResultsThe soil variables had the highest marginal explanatory power. Organic matter was the main driver of floristic composition, indicating a gradient associated also with soil moisture. The pure effect of spatial variables was very important, reflecting historical processes. On the contrary, management and topography variables sets were relatively weak predictors. Partial ordination showed that two topographic variables, slope and height above the plain, had an important weight in the hay meadow floristic assemblage, influencing soil fertility.ConclusionsThis analysis (a) confirms the determining function of soil fertility and moisture in driving plant species composition and traits; (b) focuses on the marginal power of current management when past traditional agro‐pastoral activity undergoes changes in mode and intensity; (c) highlights the role of spatial variables and site history; and (d) improves knowledge about topographical factors as drivers of species composition. The maintenance of hay meadow mosaics requires preservation of grasslands in complete topographical catenae and prevention of the abandonment of parcels on steep slopes. Considering the spatial variability of the studied communities, it is necessary to include a high number of geographically and ecologically different areas in a conservation network.

Land-use impacts on the composition and diversity of the Baikiaea– Guibourtia–Pterocarpus woodlands of north-western Zimbabwe

Variation in floristic composition of recovering Baikiaea–Guibourtia–Pterocarpus woodlands was studied in different development stages (from early regrowth to mature woodland) under different land-use systems (protected areas, timber harvesting, pole and firewood collection, and abandoned crop fields), in the Gwayi and Tsholotsho areas in north-western Zimbabwe. A total of 150 nested circular plots were sampled representatively in four different development stages related to the land-use systems. The DBH (stem diameter at 1.3 m above ground level) and tree height were recorded by species for all stems of tree species with DBH ≥ 15 cm in a 30-m-radius plot (0.283 ha) and for trees with DBH 5.0–14.9 cm in a 11.3-m-radius plot (0.04 ha) (both centred around the same midpoint). Stems with DBH < 5 cm were counted by species in an inner sub-plot of 5.65 m (0.01 ha) radius. Tree data (stem DBH ≥ 5 cm) and regeneration data (stem DBH < 5 cm) by stem counts per species per plot, were used separately to run TWINSPAN (TWo-way INdicator SPecies ANalysis) classifications of species assemblages. Importance values were calculated for all tree species per community. Shannon–Wiener diversity indices were calculated for each community and tested for differences using one-way ANOVA in SPSS version 21. Detrended correspondence analysis (DCA) implemented in the CANOCO ordination software was used to determine the extent of variation amongst the identified communities. The classification identified 12 tree communities and 13 regeneration communities, clustering plots from different land uses together. Baikiaea plurijuga was the most important tree species in all tree communities, except where Combretum collinum, C. apiculatum, Commiphora mossambicensis and Pterocarpus angolensis were dominant. Pterocarpus angolensis showed low importance in most communities, except for communities from undisturbed sites (mostly mature trees) and abandoned fields (mostly young trees). Baikiaea plurijuga was most important in most regeneration communities, except in communities dominated by Baphia massaiensis, C. collinum, C. apiculatum and P. angolensis. Species diversity differed significantly (p < 0.05) amongst tree communities. The DCA ordination showed little variation amongst the communities. The cumulative contribution of environmental factors explaining variation in species composition was 22.6% for tree communities and 26.1% for regeneration communities, suggesting that recovery from disturbance after different land uses may explain more of such variation.

Influence de la liane envahissante Sericostachys scandens Gilg & Lopr. (Amaranthaceae) sur la diversité des espèces végétales ligneuses du Parc National de la Kibira au Burundi

ABSTRACTThis study aims to (1) estimate the effect of Sericostachys scandens density on the species richness of woody species development stages, and (2) evaluate the variation in floristic composition of woody species development stages according to S. scandens density within the Kibira National Park (KNP) in Burundi. The abundance of this liana and other woody species (regeneration, juvenile and adult trees) was measured in 100 plots of 50 m × 50 m each, evenly distributed in invaded and non-invaded areas. A negative binomial regression was performed to test the effect of liana density on the species richness of each development stage of woody plant species. A multivariate analysis of the variance on dissimilarity matrix (ADONIS) was performed to test the variation of the floristic composition of woody communities according to the density of the invading liana. Liana density negatively affects regeneration (t = −10.170; p < 0.0001), juvenile (t = −4.346; p < 0.0001) and adult trees (t = −7.740; p < 0.0001). The invasion by S. scandens causes variation in the floristic composition of juvenile (p = 0.02) and adult trees (p = 0.01). Future studies should identify the woody species having the highest local extirpation probability owing to the expansion of S. scandens.

Woody species diversity, population structure, and regeneration status in the Gra-Kahsu natural vegetation, southern Tigray of Ethiopia

The study was conducted at Gra-Kahsu protected natural vegetation (PNV) and communal grazing land (CGL), in order to evaluate the conservation impact level. The diversity of plant species, population structure of woody species, and regeneration status were analysed from 62 quadrats, each with 20 m × 20 m for trees and 5 m × 5 m for shrubs, using systematic sampling methods. A total of 64 vascular plant species belonging to 52 genera and 37 families from PNV and 43 plant species belonging to 34 genera and 25 families from CGL was identified. Shannon diversity index values of PNV and CGL were 2.29 and 1.84, respectively. The mean basal area of PNV and CGL were 8.29 and 5.32 m2/ha, respectively. Three community types from PNV and two from CGL were identified. The population structure of woody species based on diameter and height class distribution showed reflected reversed J-shape for PNV however, bell-shaped, and interrupted inverted J-shape for CGL. The regeneration status of PNV and CGL were considered as good (sapling > seedling > matures) and fair (mature > sapling > seedling), respectively. Therefore, the floristic analysis of these two adjacent land use systems located in similar landscape showed distinctive variation in floristic composition, diversity, and regeneration status, which could be taken as the best practice of restoration and rehabilitation programs like, area exclosure.

The role of climate on floristic composition in a latitudinal gradient in the Brazilian Atlantic Forest

Background and aims – Latitudinal gradients have an important influence on species distribution reflecting the effects of environmental factors such as temperature, rainfall, soil, and geographical distance. In the southeastern Brazilian Atlantic Forest, the role of climatic variables in the floristic composition is better known for altitudinal gradients of the Serra do Mar Mountains rather than for the latitudinal gradient. Here, we investigated the effects of mean annual temperature and rainfall on tree species distribution and composition in a latitudinal gradient in the Atlantic forest.Methods – We calculated each species frequency of occurrence and the latitudinal range. We used multivariate analyses (direct ordination, Hierarchical Clustering followed by Indicator Species analysis and NMDS) to investigate variation in floristic composition, and regression analyses to evaluate mean annual temperatures and rainfall effects on tree species composition along the latitudinal gradient (21°S to 28°S).Key results – A total of 789 species were registered, of which a majority (646 species) were present in less than 20% of the sampled areas, and only four species (0.5%) were present in more than 80% of the sampled areas. Only ten species (1.3%) reached the maximum latitudinal range (~6°). We found a strong correlation between variation in floristic composition and the spatial position in the latitudinal gradient. The cluster analyses detected two main floristic groups, one composed by the forests from Rio de Janeiro (21°S to 23°S) and the second by the forests from São Paulo, Paraná and Santa Catarina States (23°S to 28°S). The multiple regression analysis revealed a strong effect of the climatic variables on the variation of the floristic composition along the latitudinal gradient (r2 = 0.81, P &lt; 0.001), where 62.82% of the variation were explained by mean annual temperature, 8.27% by annual rainfall and 10.45% by both variables together.Conclusions – The restricted distribution of most species may be explained by variations in mean annual temperature and annual rainfall along the latitudinal gradient. For instance, the decreasing mean annual temperature along the coast and the occurrence of frosts at higher latitudes may limit the southward distribution of some species while the lower annual rainfall (with marked seasonality) in the north of the gradient may limit the northward distribution of other species. Although mean annual temperature explained most of the variation in species composition along the latitudinal gradient, the abrupt variation in annual rainfall may explain the high floristic dissimilarity detected in the north of the gradient.

Floristic composition, structure and soil-vegetation relations in three white-sand soil patches in central Amazonia

ABSTRACT The Amazonian white-sand vegetation presents a set of unique features, such as the dominance of a few species, high endemism and low species richness, which differentiate it from other Amazonian forests. Soil parameters have long been recognized as the main drivers of white-sand vegetation (WSV) characteristics. However, how they influence the composition, richness and structure of this vegetation type is still poorly understood. In this study we investigated the variation in floristic composition between patches and the soil-vegetation relations in three central Amazonian WSV patches. We tested whether slight differences in soil properties are linked with differences in floristic composition, species richness and forest structure in adjacent patches. In each patch three plots of 50 x 50 m were sampled (a total of 2.25 ha). Soil samples were collected for each plot. The sampling cutoff for arboreal individuals was DBH ≥ 5 cm. We sampled a total of 3956 individuals belonging to 40 families and 140 species. In each patch only a few species were dominant, but the dominant species varied among patches. Differences among patches were significant, but plots in the same patch tended to have similar species composition. The variable sum of bases (SB) was directly related to species composition, however, species richness and forest structure were not related to soil parameters. Even small variations in soil parameters can change species composition in WSV, although these variations do not necessarily influence the richness and other structural parameters.

Variations in floristic composition of wild and cultivated species associated with Moringa oleifera Lam. in Egypt

The aim of this work is to study the cultivated and wild species associated with Moringa oleifera in different sites in Egypt. The cultivated species were 174 related to 145 genera and 67 families, while the wild species were 45 related to 39 genera and 21 families. Fabaceae was the most represented cultivated family (15 species), while Poaceae was the most represented wild family (8 species). Phoenix dactylifera and Portulaca oleracea were the most common cultivated and wild species, respectively. Phanerophytes were the most represented life form, regarding the cultivated species (79.5%), whereas therophytes were the most represented life form (62.2%). The application of Two Way Indicator Species Analysis (TWINSPAN) on the floristic composition of the sampled stands led to classify them into 7 vegetation groups at level 5 for the cultivated species, and 5 groups at level 3 for the wild species. The cultivated groups were named according to their dominant species as follows: Ficus elastica, Abutilon hirtum, Cordia myxa, Carya illinoensis, Azadirachta indica, Ficus benjamina and Ceiba speciosa. In addition, the wild groups were: Pancratium maritimum, Digitaria ciliaris, Cyperus rotundus, Lantana camara and Bidens pilosa.