Floristic Gradients Research Articles

Strong soil–vegetation relationship in riparian forests of the middle Rio Doce watershed, south-eastern Brazil

Phytosociological surveys and soil quality studies are relevant tools for the implementation of restoration programmes. This study aimed to characterise the vegetation of the tree and sapling strata in preserved riparian forests of the middle portion of the Rio Doce watershed in the Atlantic Rain Forest, Brazil. In addition, we tested the association between edaphic factors and the vegetation community. We sampled three sites of the middle sector of the Rio Doce watershed in Itueta (two sites) and Santa Rita do Itueto (one site) municipalities in Minas Gerais, south-eastern Brazil. At each sampling site, we inventoried 15 plots of 100 m2 (10 × 10 m) for the tree stratum. Within each plot of the tree stratum we delimited a 25 m2 (5 × 5 m) plot, totalling 4 500 m2 and 1 125 m2 respectively for the tree and sapling strata. We employed co-inertia analysis to test the relationship between soil factors and the plant community and to highlight the taxon– environment relationship. We recorded 157 species belonging to 31 families, with 105 species from 24 families in the tree stratum, and 85 species from 22 families in the sapling stratum. Edaphic factors were highly heterogeneous among plots, although most of the plots presented soils with neutral pH and high fertility (base saturation > 50%). Co-inertia analyses showed highly significant associations between edaphic factors and the plant community, both for the tree (RV = 0.486, p < 0.001) and the sapling strata (RV = 0.692, p < 0.001). We highlighted the existence of a clear edaphic– floristic gradient, with a significant association of certain species with contrasting soil conditions. Knowledge about the association between environmental characteristics and floristic composition can assist in the selection of species with greater chances to establish in specific environmental conditions.

How to classify forests? A case study from Central Europe

Aims: Inconsistent treatment of the vegetation layers is one of the main problems in the floristic classification of forests. In this study I investigate whether a classification based solely on woody species leads to units similar to the Braun-Blanquet system or to something completely different. Study area: Austria (Central Europe) and adjacent regions. Methods: 23,681 forest relevés from the Austrian Vegetation Database were classified using TWINSPAN. Spruce and pine plantations and stands with a cover of non-native woody species &amp;gt; 5% were excluded from the dataset. Only native tree and shrub species were used in the classification while herbs, dwarf shrubs, cryptogams and all records of woody species in the herb layer were omitted. Results: The TWINSPAN classification revealed elevation (i.e., climate) as the main floristic gradient in the data set. Within lowland communities, soil moisture was the dominant factor. The higher units of the Braun-Blanquet system were mostly well reproduced. Conclusions: The higher levels of the phytosociological forest classification (class, order, partly also alliance) can basically be defined by taking only the shrub and tree layer into account. However, all past and current classifications suffer from arbitrary exceptions to this rule. This leads to many inconsistencies and blurs the main biogeographical patterns within European forests. Here I argue that using the tree and shrub species for defining the higher levels and the understorey species for defining the lower ones is best suited to meet the properties that users would expect from a good forest classification. Taxonomic reference: Fischer et al. (2008). Syntaxonomic reference: Mucina et al. (2016) if not stated otherwise. Abbreviations: EVC = EuroVegChecklist (Mucina et al. 2016).

Drivers of exceptional Neotropical biodiversity: an updated view

The Neotropics, following the most common definition, comprise the tropical areas of the American continent from Mexico to Argentina (Morrone, 2017) and encompass the largest number of described species in the world, accounting for almost one third of global biodiversity (Raven et al., 2020). This outstanding biodiversity fascinated early naturalists including Alexander Von Humboldt, who proposed the foundations of biogeography by observing the floristic gradients of the Andes (Humboldt & Bonpland, 1805), and Alfred Wallace, whose proposal of Amazonian rivers as isolation barriers for animals built one of the pillars of evolutionary theory (Wallace, 1852). The Neotropical region has also been an important natural laboratory for more recent advances in ecology and evolution, such as the role of the landscape and ecological interactions in the diversification of plants (Antonelli et al., 2018; Rull & Carnaval, 2020). Since...

Disturbance alters relationships between soil carbon pools and aboveground vegetation attributes in an anthropogenic peatland in Patagonia.

Anthropogenic‐based disturbances may alter peatland soil–plant causal associations and their ability to sequester carbon. Likewise, it is unclear how the vegetation attributes are linked with different soil C decomposition‐based pools (i.e., live moss, debris, and poorly‐ to highly‐decomposed peat) under grassing and harvesting conditions. Therefore, we aimed to assess the relationships between aboveground vegetation attributes and belowground C pools in a Northern Patagonian peatland of Sphagnum magellanicum with disturbed and undisturbed areas. We used ordination to depict the main C pool and floristic gradients and structural equation modeling (SEM) to explore the direct and indirect relationships among these variables. In addition, we evaluated whether attributes derived from plant functional types (PFTs) are better suited to predict soil C pools than attributes derived from species gradients. We found that the floristic composition of the peatland can be classified into three categories that follow the C pool gradient. These categories correspond to (1) woody species, such as Baccharis patagonica, (2) water‐logged species like Juncus procerus, and (3) grasslands. We depicted that these classes are reliable indicators of soil C decomposition stages. However, the relationships change between management. We found a clear statistical trend showing a decrease of live moss, debris, and poorly‐decomposed C pools in the disturbed area. We also depicted that plant diversity, plant height, and PFT composition were reliable indicators of C decomposition only under undisturbed conditions, while the species‐based attributes consistently yielded better overall results predicting soil C pools than PFT‐based attributes. Our results imply that managed peatlands of Northern Patagonia with active grassing and harvesting activities, even if small‐scaled, will significantly alter their future C sequestration capacities by decreasing their live and poorly‐decomposed components. Finally, aboveground vegetation attributes cannot be used as proxies of soil C decomposition in disturbed peatlands as they no longer relate to decomposition stages.

Landform-vegetation units in karstic depressions (dolines) evaluated by indicator plant species and Ellenberg indicator values

In this study, the objects of research were circular and concave karstic depressions, called sinkholes or dolines. All these negative topographic anomalies were previously recognized as safe havens for cool-adapted species on karstic plateaus. However, the high geodiversity of doline landforms on karst plateaus does not ensure that all dolines are really safe havens that should be considered for conservation status. We propose the use of indicator species to identify different dolines' “sections” and their overall types to identify dolines with high conservation value for cool-adapted species. We aimed to divide dolines into landform-vegetation units (LVU) according to basic geomorphic characteristics and indicator plant species. We carried out intensive sampling of vegetation plots (n = 286) across 10 dolines of different geomorphology ranging from 20 m to 100 m in diameter and from 2 m to 20 m in depth. Each doline was classified into a maximum of four LVUs: bottom, lower slope, upper slope and top. Vascular plants were used as a proxy for ecosystem biodiversity and indicator of ecological conditions. The diversity of vascular plant communities was sampled along N–S transects from one side of the doline over the bottom to the other side. Geodiversity parameters of individual dolines were calculated using a high-resolution digital elevation model (LiDAR / Light Detection And Ranging) and their significance was established by permutation test in CCA (Canonical Correlation Analysis). The floristic gradient was established by the first axis of PCoA (Principal Coordinates Analysis) and shows the species turn-over along the trajectory. Discrete plant communities were determined by TWINSPAN (Two-Way Indicator Species ANnalysis) classification. Based on this analysis, transects were disintegrated into four LVUs. Communities within LVUs were compared by Ellenberg indicator values and according to habitat preference of species. The indicator (also termed diagnostic) plant species were calculated by fidelity measure and related to ecological conditions along transects. We found that all four LVUs appear only in dolines that are at least 13.5 m deep and those can serve as a good safe haven for cool-adapted species in foreseen climatic change. We also confirmed that doline depth is the most important factors influencing the plant community composition. The results can be directly transformed to other karst regions (karst plateaus) with the same zonal vegetation, but calibration is needed in case of their application in other areas.

Study of Forage Quality of Grasslands on the Southern Margin of the Pannonian Basin

Since grasslands provide many ecosystem services, there are often different opinions on their management (e.g., agronomy, ecology, botany). Multidisciplinary research on this topic is therefore needed. This article focuses on the impact of ecological conditions, functional groups, ecological strategies, floristic composition (through habitat preference of species), major floristic gradients (presented as first two NMDS axes), and the management on forage quality. We estimated the forage quality using indicator values. All of the available vegetation plots in the region on wet and mesic meadows, managed pastures, and tall-herb meadow/pasture fringes on deeper or shallower soils (i.e., grasslands) were collected, organized in a database, and elaborated according to standard procedure. We used a widely accepted grassland classification system that uses floristic composition to define grassland types. Based on an NMDS ordination diagram and according to functional groups, ecological strategies, and habitat preferences (behavior of species) and management, we defined three major groups: mesic meadows (mowed), wet meadows (mowed), and pastures (grazed). We correlated all groups’ functional groups, ecological strategies, habitat preferences (behavior of species), major floristic gradients, management, and forage quality. We found that forage quality mainly depends on moisture conditions and that nutrients and grazing are less important. Within the grasslands under consideration, mesic meadows and mesic pastures have the highest forage quality.

Using floristic gradient mapping to assess seasonal thaw depth in interior Alaska

AbstractQuestionsIs it possible to map floristic gradients in heterogeneous boreal vegetation by using remote‐sensing data? Does a continuous vegetation map enable the creation of a spatially continuous map of seasonal permafrost soil thaw depth?LocationBonanza Creek LTER, Fairbanks, Alaska, USA.MethodsVegetation records are subjected to an ordination to extract the predominant floristic gradient. The ordination scores are then extrapolated using Sentinel 2 imagery and a digital elevation model (DEM). As the relation between vegetation pattern and seasonal thaw depth was confirmed in this study, the spatial distribution of ordination scores is then used to predict seasonal thaw depth over the same area.ResultsThe first dimension of the ordination space separates species corresponding to moist and cold soil conditions from species associated with well‐drained soils. This floristic gradient was successfully mapped within the sampled plant communities. The extrapolated thaw depths follow the typical distribution along a topographical and geomorphological gradient for this region. Besides vegetation information also DEM derivatives show high contributions to the thaw depth modeling.ConclusionWe demonstrate that floristic gradient mapping in boreal vegetation is possible. The accuracy of the thaw depth prediction model is comparable to that in previous analyses but uses a more parsimonious set of predictors, underlining the efficacy of this approach.

Let your maps be fuzzy!—Class probabilities and floristic gradients as alternatives to crisp mapping for remote sensing of vegetation

AbstractMapping vegetation as hard classes based on remote sensing data is a frequently applied approach, even though this crisp, categorical representation is not in line with nature's fuzziness. Gradual transitions in plant species composition in ecotones and faint compositional differences across different patches are thus poorly described in the resulting maps. Several concepts promise to provide better vegetation maps. These include (1) fuzzy classification (a.k.a. soft classification) that takes the probability of an image pixel's class membership into account and (2) gradient mapping based on ordination, which describes plant species composition as a floristic continuum and avoids a categorical description of vegetation patterns. A systematic and comprehensive comparison of these approaches is missing to date. This paper hence gives an overview of the state of the art in fuzzy classification and gradient mapping and compares the approaches in a case study. The advantages and disadvantages of the approaches are discussed and their performance is compared to hard classification (a.k.a. crisp or boolean classification). Gradient mapping best conserves the information in the original data and does not require an a priori categorization. Fuzzy classification comes close in terms of information loss and likewise preserves the continuous nature of vegetation, however, still relying on a priori classification. The need for a priori classification may be a disadvantage or, in other cases, an advantage because it allows using categorical input data instead of the detailed vegetation records required for ordination. Both approaches support spatially explicit accuracy analyses, which further improves the usefulness of the output maps. Gradient mapping and fuzzy classification offer various advantages over hard classification, can always be transformed into a crisp map and are generally applicable to various data structures. We thus recommend the use of these approaches over hard classification for applications in ecological research.

Modeling of tree height–diameter relationships in the Atlantic Forest: effect of forest type on tree allometry

Tree height is one of the most important variables for quantitative assessment of forest stocks, but it is difficult to directly measure. Such allometric relationships of trees can vary between geographical regions, however, mainly due to climatic, edaphic, and floristic gradients. Based on the hypothesis that different forest types influence the generic modeling of tree height–diameter relationships on geographical scales, this study aimed to (i) fit equations to estimate tree height in Atlantic Forest types in the state of Rio de Janeiro, Brazil; (ii) compare efficiency and precision between generic and specific equations for forest types; and (iii) test the effect of different forest types and species on the height–diameter relationship. Four allometric models were tested for all forests (generic) and three main forest types (specific). Effects of tree size, forest types, and species on tree height estimation were analyzed using multiple linear models and mixed-effect linear models. A significant effect of forest type and species on tree height was seen, showing the need to apply local specific equations to minimize the effects that are not captured by generic equations. Differences in tree allometry between forest types were associated with temperature, rainfall, soil, and forest structure. These results confirm the effect of the local environment on the height–diameter relationship of trees as found over large scales in tropical forests.

A Small Elevational Gradient Shows Negative Bottom-to-Top Bryophyte Richness in a Seasonally Dry Forest in Brazil

Elevational gradients can serve as powerful tools for testing ecological relationships between species richness versus environmental variables. Although the patterns be usually from positive to humped-shaped, elevational gradients may run in a negative way with the species richness decreasing in relation to the altitude. The floristic gradient may vary according species biology, site and, scale for analyses. Therefore, elevational gradient can be useful for detecting points for biological conservation and may be analized by using sensitive species as approach for others species including banner-species. Along an elevational gradient in a harsh semiarid environment we are showing a negative relationship between bryophyte species richness and increasing elevation. The observed floristic gradient reflects environmental constraints related to light requirements and low humidity as environmental conditions become more severe at higher altitudes, where anthropogenic activities such as farming dramatically alter the vegetation covering. The diversity of bryophytes in terms of their light requirements makes them excellent bioindicators of environmental quality. We provide data that will be useful for conservation planning and management, and report species with rare distributions in Brazil and others not yet recorded as occurring in dry forests.

Remote sensing of coastal vegetation: Dealing with high species turnover by mapping multiple floristic gradients

AbstractAimsMapping gradual transitions in plant species composition via a combination of ordination and regression from remote sensing data is becoming an established approach. However, straightforward analysis of areas with high species turnover rates may result in a loss of information since a high level of generalization is required. In this study, we investigate whether analysis of more homogeneous subsets, in contrast to processing of the complete dataset, is a viable approach to mapping multiple floristic gradients.LocationThe coastal nature reserve “Zwin” (Belgium).MethodsThe measured dataset is partitioned into more homogeneous subsets based upon species composition using hierarchical classification. The dataset and subsets are then processed separately. First, ordination is performed to extract floristic gradients in plant species composition; second, these gradients are related to airborne hyperspectral remote sensing data through regression models and mapped by projecting these models on image data. Regression validation and Mantel tests are used to compare the results within the study and to other studies.ResultsHierarchical classification resulted in two homogeneous vegetation subsets. Ordination yielded four gradients in the area and all regression models compared favorably to similar studies in other areas with R² values ranging from 0.47 to 0.74. The Mantel test showed that by dividing the dataset into subsets, higher resemblance to the original vegetation data can be achieved.ConclusionWe showed that mapping gradual transitions in plant species composition across multiple subsets sampled from one measured vegetation dataset is a promising approach for retrospective analysis of areas with high species turnover rates. In addition to potential improvements in performance, this complementary analysis enables mapping of additional gradients, suggesting that all conventionally predicted maps remain available, valuable, and necessary for thorough understanding of plant species composition.

Niche‐based processes outperform neutral processes when predicting distance decay in co‐dominance along the Amazon – Andes rainforest gradient

AbstractQuestionDispersal limitation (neutral hypothesis) and deterministic factors (niche hypothesis) shape floristic gradients including between‐site patterns of species’ dominance (co‐dominance). Because their relative importance remains poorly known, we ask how their comparative contribution to co‐dominance changes with elevation and geographical extent.LocationMadidi region, NW Bolivia.MethodsWe analysed floristic composition and environmental factors of 90 plots spanning the gradient from Amazonian (&lt;1,000 m) to montane forests at three elevations (1,200–1,500; 2,000–2,300; and 2,800–3,200 m) and two geographical extents: local (plots &lt;12 km apart) and regional (38–120 km apart). We modelled distance decay within each elevational band with a neutral model, using two parameters (speciation rate and dispersal distance). Subsequently, we related the model's residuals to environmental differences using flexible machine learning models.ResultsWe found that 5–44% of the variability in floristic differences along the gradient studied can be explained by a neutral model of distance decay, while 18–50% can be explained by environmental differences. Montane forests showed an overall gradient in floristic composition that is congruent with an increase in elevation for both dispersal limitation and environmental filtering. However, Amazonian forest was more niche‐structured and more dispersal‐limited relative to its elevation and topography.ConclusionsEnvironmental differences explained floristic differences better than the neutral model, even giving preferential attribution to the more parsimonious neutral processes.

Discovering floristic and geoecological gradients across Amazonia

AbstractAimTo map and interpret floristic and geoecological patterns across the Amazon basin by combining extensive field data with basin‐wide Landsat imagery and climatic data.LocationAmazonia.TaxonGround truth data on ferns and lycophytes; remote sensing results reflect forest canopy properties.MethodsWe used field plot data to assess main ecological gradients across Amazonia and to relate floristic ordination axes to soil base cation concentration, Climatologies at High Resolution for the Earth's Land Surface Areas (CHELSA) climatic variables and reflectance values from a basin‐wide Landsat image composite with generalized linear models. Ordination axes were then predicted across all Amazonia using Landsat and CHELSA, and a regional subdivision was obtained using k‐medoid classification.ResultsThe primary floristic gradient was strongly related to base cation concentration in the soil, and the secondary gradient to climatic variables. The Landsat image composite revealed a tapestry of broad‐scale variation in canopy reflectance characteristics across Amazonia. Ordination axis scores predicted using Landsat and CHELSA variables produced spatial patterns consistent with existing knowledge on soils, geology and vegetation, but also suggested new floristic patterns. The clearest dichotomy was between central Amazonia and the peripheral areas, and the available data supported a classification into at least eight subregions.Main conclusionsLandsat data are capable of predicting soil‐related species compositional patterns of understorey ferns and lycophytes across the Amazon basin with surprisingly high accuracy. Although the exact floristic relationships may differ among plant groups, the observed ecological gradients must be relevant for other plants as well, since surface reflectance recorded by satellites is mostly influenced by the tree canopy. This opens exciting prospects for species distribution modelling, conservation planning, and biogeographical and ecological studies on Amazonian biota. Our maps provide a preliminary geoecological subdivision of Amazonia that can now be tested and refined using field data of other plant groups and from hitherto unsampled areas.

Beta-Diversity Modeling and Mapping with LiDAR and Multispectral Sensors in a Semi-Evergreen Tropical Forest

Tree beta-diversity denotes the variation in species composition at stand level, it is a key indicator of forest degradation, and is conjointly required with alpha-diversity for management decision making but has seldom been considered. Our aim was to map it in a continuous way with remote sensing technologies over a tropical landscape with different disturbance histories. We extracted a floristic gradient of dissimilarity through a non-metric multidimensional scaling ordination based on the ecological importance value of each species, which showed sensitivity to different land use history through significant differences in the gradient scores between the disturbances. After finding strong correlations between the floristic gradient and the rapidEye multispectral textures and LiDAR-derived variables, it was linearly regressed against them; variable selection was performed by fitting mixed-effect models. The redEdge band mean, the Canopy Height Model, and the infrared band variance explained 68% of its spatial variability, each coefficient with a relative importance of 49%, 32.5%, and 18.5% respectively. Our results confirmed the synergic use of LiDAR and multispectral sensors to map tree beta-diversity at stand level. This approach can be used, combined with ground data, to detect effects (either negative or positive) of management practices or natural disturbances on tree species composition.

Spatio‐temporal gradients in food supply help explain the short‐term colonisation dynamics of the critically endangered central rock‐rat (Zyzomys pedunculatus)

AbstractCurrently, the impact of introduced predators on small mammal population decline is a focal research direction in the Australian desert literature. In all likelihood though, single‐factor explanation of population dynamics is inadequate, leaving gaps in our knowledge of the multitude of potential influences on small mammal abundance and occupancy patterns in time and space. Here, we investigated floristic gradients across four potential refuge sites of the central rock‐rat, Zyzomys pedunculatus, a granivore rodent (50–120 g) that is endemic to central Australia and is categorised as critically endangered. The study took place in Tjoritja/West MacDonnell National Park in the MacDonnell Ranges bioregion. Floristic sampling was allocated across the four sites, the locations of which were predetermined by an established monitoring and management programme for the central rock‐rat. Our aim was to examine the relationship between environmental gradients and floristic composition across the four sites, and thereby test the extent to which the patterns of food type and food availability can inform central rock‐rat spatio‐temporal dynamics. We found high site‐scale floristic patterning that related foremost to elevation and then to antecedent rainfall and time‐since‐fire and fire‐severity effects. To interpret these results, we applied the principles of refuge theory and we described a gradient from core refuge habitat to intermittent and then marginal habitat within the current central rock‐rat stronghold area. Overall, our results implied a strong floristic basis to central rock‐rat site occurrence, and they thus compel us to take explicit account of spatial (elevation) and temporal (rainfall–productivity and fire‐disturbance) influences on the food axis of potential refuge sites of this critically endangered species.

Vegetation on mesic loamy and sandy soils along a 1700-km maritime Eurasia Arctic Transect.

QuestionsHow do plant communities on zonal loamy vs. sandy soils vary across the full maritime Arctic bioclimate gradient? How are plant communities of these areas related to existing vegetation units of the European Vegetation Classification? What are the main environmental factors controlling transitions of vegetation along the bioclimate gradient?Location1700‐km Eurasia Arctic Transect (EAT), Yamal Peninsula and Franz Josef Land (FJL), Russia.MethodsThe Braun‐Blanquet approach was used to sample mesic loamy and sandy plots on 14 total study sites at six locations, one in each of the five Arctic bioclimate subzones and the forest–tundra transition. Trends in soil factors, cover of plant growth forms (PGFs) and species diversity were examined along the summer warmth index (SWI) gradient and on loamy and sandy soils. Classification and ordination were used to group the plots and to test relationships between vegetation and environmental factors.ResultsClear, mostly non‐linear, trends occurred for soil factors, vegetation structure and species diversity along the climate gradient. Cluster analysis revealed seven groups with clear relationships to subzone and soil texture. Clusters at the ends of the bioclimate gradient (forest–tundra and polar desert) had many highly diagnostic taxa, whereas clusters from the Yamal Peninsula had only a few. Axis 1 of a DCA was strongly correlated with latitude and summer warmth; Axis 2 was strongly correlated with soil moisture, percentage sand and landscape age.ConclusionsSummer temperature and soil texture have clear effects on tundra canopy structure and species composition, with consequences for ecosystem properties. Each layer of the plant canopy has a distinct region of peak abundance along the bioclimate gradient. The major vegetation types are weakly aligned with described classes of the European Vegetation Checklist, indicating a continuous floristic gradient rather than distinct subzone regions. The study provides ground‐based vegetation data for satellite‐based interpretations of the western maritime Eurasian Arctic, and the first vegetation data from Hayes Island, Franz Josef Land, which is strongly separated geographically and floristically from the rest of the gradient and most susceptible to on‐going climate change.

A sharp floristic discontinuity revealed by the biogeographic regionalization of African savannas

AbstractAimIn tropical Africa, savannas cover huge areas, have high plant species richness and are considered as a major natural resource for most countries. There is, however, little information available on their floristics and biogeography at the continental scale, despite the importance of such information for our understanding of the drivers of species diversity at various scales and for effective conservation and management. Here, we collated and analysed floristic data from across the continent in order to propose a biogeographical regionalization for African savannas.LocationWe collated floristic information (specifically woody species lists) for 298 samples of savanna vegetation across Africa, extending from 18° N to 33° S and from 17° W to 48° E.TaxaWe focused on native woody species.MethodsWe used ordination and clustering to identify the floristic discontinuities and gradual transitions across African savannas. Floristic relationships, specificity and turnover, within and between floristic clusters, were analysed using a (dis‐)similarity‐based approach.ResultsWe identified eight floristic clusters across African savannas which in turn were grouped into two larger macro‐units. Ordinations at species and genus levels showed a clear differentiation in woody species composition between the North/West macro‐unit and the South/East macro‐unit. This floristic discontinuity matches to the High (i.e. N&amp;W) and Low (S&amp;E) division of Africa previously proposed by White () and which tracks climatic and topographical variation. In the N&amp;W savannas, the floristic gradient determined by rainfall was partitioned into the Sudanian (drier) and Guinean (wetter) clusters. Within the highly heterogeneous S&amp;E savannas and woodlands, six clusters were identified: Ugandan, Ethiopian, Mozambican, Zambezian, Namibian and South African.Main conclusionsThe proposed pan‐African classification of savannas and woodlands might assist the development of coordinated management and conservation policies.

Mapping floristic gradients of forest composition using an ordination-regression approach with landsat OLI and terrain data in the Central Hardwoods region

Mapping forest properties with supervised remote sensing has historically and increasingly remained vital to research and management efforts, and the demand for such products will only increase as better tools and data increase the usability of such maps. Multispectral imagery by the Landsat program has been an invaluable resource for forest type characterization for several decades. As an alternative to traditional classification approaches dominating these efforts, we instead employed an ordination-regression approach to mapping forest composition as floristic gradients across a ∼5000-km2 forestland in southeastern Ohio’s Central Hardwoods. Plot data (n = 699 plots; 99 species/genera) from a comprehensive sample of both overstory and understory woody plants across structurally- (open to closed canopy) and topographically-variable forest conditions were projected onto a non-metric multidimensional scaling (NMDS) ordination solution. Floristic gradients, via their ordination scores, were related to spectral reflectance provided by a multitemporal Landsat 8-Operational Land Imager (OLI) image and various terrain variables using Random Forests models. Approximately 61%, 49%, and 25% of the floristic variation among the three axes of the NMDS ordination were related to the remotely-sensed variables during regression modeling. The axes were predicted onto three images and merged to a RGB color composite for the final floristic gradient map, displaying multivariate vegetation variation across the landscape in terms of variation in color. The color values, by referencing ordination space position within the original solution, provide a statistical approximation of the taxonomic composition of individual forest stands in relation to the plot data. We found this approach highly effective and an attractive alternative to traditional classifications. It is time-efficient, more realistic in that compositional turnover is expressed in continuous fields rather than arbitrary breaks, and less subjective, overcoming the generalization problem inherent in categorizing vegetation assemblages a priori. Moving forward, our model will be a valuable tool in developing suitable management options on individual forest stands for the restoration of desired species, adapting to a changing climate, and improving wildlife habitat in forestlands across the Central Hardwoods.

Successional trajectories and rates of change in sub-tropical Quercus forests in west-central Mexico: evidences from a permanent plot network

Forest succession was studied in sub-tropical high-altitude, Quercus-dominated forest in west-central Mexico in order to address the following research questions: (1) How do successional trajectories progress in three contrasting floristic zones? (2) Which is the magnitude of successional rate of change at different time-scales? (3) What are the major environmental drivers contributing to the observed patterns of forest succession? Data was derived from 86 non-managed permanent plots, 500 m2 each, established along a 10 km floristic gradient, ranging from xeric to mesic sites. In portraying successional trajectories over time and to measure the magnitude of rate of change in three floristic zones, Detrended Correspondence Analysis (DCA) was developed. In order to represent the most significant environmental drivers on patterns of successional trajectories and successional rate of change, we used generalized linear models with gaussian error. Results showed that successional trajectories were not deterministic in each of the floristic zones over the different time-scales analysed; instead we observed four successional trajectories i) plots with an outstanding displacement between time periods, accompanied by an erratic migration over the DCA diagram; ii) plots with a moderate rate of change and uniform movement across the ordination space; iii) a small number of plots with slight change and; iv) few plots with no changes. Soil related variables such as pH, P, N, Mg and Mn, together with slope and catena, were predicted as important contributing factors related to successional processes.

Patterns of Spatial Diversity and Structure of Mangrove Vegetation in Pacific West-Central Mexico

Mangrove ecosystems are important sources of goods and services to people, supporting ecological, biological, social and economic values. Nevertheless the scale of human-impact on mangroves in many countries has increased dramatically over the past years. Understanding their structure and plant composition is decisive for a proper design of conservation and management strategies, therefore we assessed patterns of floristic composition and structure together with their spatial and temporal environmental variability. Sixty-five 100 m2 permanent plots were established across the study area in order to cover the full range of structural and floristic variation. We sampled interstitial water properties (salinity, total dissolved solid, pH, oxygen dissolved and temperature) during the dry and the wet seasons. We ran non-metric multidimensional scaling ordinations (NMDS) to discern both floristic composition and structural changes related to interstitial water. We also ran multiple linear regression analyses, to determine the relationship between interstitial water with stand structural variables. Results showed a floristic gradient related to salinity while structure indicated by stand density and tree sizes, were explained primarily by salinity along the whole year; oxygen dissolved and pH were also significant in both wet and dry season while temperature was only important in the dry season.