Succession Model Research Articles

An Integrated Conceptual Model of Performance Appraisals and Succession Planning using Multi valued Evaluation

<span>The quality of Human Resource and leadership are the two important determinants that<span> determine the success of an organization. Though many organizations asserts that people<span> are their most valuable asset, still very few organizations follows a structured approach<span> for proper talent management i.e. the anticipation of needed human capital in<span> organization, with appropriate system for retaining and rewarding their workforce. The<span> paper proposes a model for performance based Succession Planning(SP) and<span> Performance Appraisals (PA) on the basis of ordinal scale of measurements using expert<span> opinion in terms of linguistic variables such as excellent performance high performance,<span> Moderate and poor performance. The model presented in this paper is an attempt to help<span> organizations in identifying and developing successors for the key position using data<span> gathered through performance appraisals that will help in evaluating the performance of<span> an employee using specific performance appraisals criteria. The proposed model will be<span> beneficial for organizations in strategically identifying and developing required talent<span> pool within the organization for internal promotions through performance appraisal<span> reviews and competency assessments using fuzzy logic, multi valued evaluation model.<br /><br class="Apple-interchange-newline" /></span></span></span></span></span></span></span></span></span></span></span></span></span></span></span>

Land use, fallow period and the recovery of a Caatinga forest

AbstractCaatinga vegetation continues to be converted into mosaics of secondary forest stands, but the affect of this process on biodiversity has not yet been examined. We used 35 regenerating and old‐growth stands of Caatinga to examine the recovery of plant assemblages subsequent to slash‐and‐burn agriculture and cattle ranching/pasture in northeastern Brazil. Plant assemblages were contrasted in terms of community structure (stem density/basal area/species richness/diversity), functional (leaf habit/reproductive traits) and taxonomic composition. Soil attributes were also examined to infer potential drivers for cross‐habitat differences. As expected, plant assemblages clearly differed across a large set of community‐level attributes, including all trait categories relative to leaf habit and reproduction (pollination syndrome/floral color, size, type). Overall, old‐growth forest stands supported distinct and more diverse assemblages at the plot and habitat level;e.g., long‐lived tree species were almost exclusively found in old‐growth forest stands. For most attributes, plant assemblages subsequent to pasture exhibited intermediate values between those exhibited by old‐growth forest and those of agriculture‐related stands. Surprisingly, soils exhibited similar fertility‐related scores across habitats. Our results indicate that: (1) sprouting/resprouting represents an important mechanism of forest regeneration; (2) assemblage‐level attributes suggest recovery at distinct rates; (3) forest regeneration implies community‐level changes in both vegetative and reproductive functional attributes, including directional changes; (4) Caatinga is not able to completely recover in a period of 15‐yr following land abandonment; and (5) historical land use affects recovery rates and successional pathways/taxonomic trajectories. Seasonally dry tropical forests may intrinsically cover a wide range of patterns relative to successional model, recovery rates and successional pathways.

Threshold dynamics in plant succession after tree planting in agricultural riparian zones

Summary Trajectories of plant communities can be described by different models of plant succession. While a Clementsian (gradual continuum model) or Gleasonian approach (relay floristics model) has traditionally been used to inform restoration outcomes, alternative succession models developed recently may better represent restoration trajectories. The threshold dynamics succession model, which predicts an abrupt species turnover after an environmental threshold is crossed, has never been used in a restoration context. This model might, however, better describe shifts in plant competitive ranking and facilitation interactions during species turnover. Fifty‐three riparian zones, planted with trees 3–17 years prior to sampling, and 14 natural riparian forests were studied in two agricultural watersheds of south‐eastern Québec (Canada). The cover of vegetation strata was assessed at the site scale, and the cover of plant species was estimated in a total of 784 1‐m2 plots. Canopy cover was measured stereoscopically for each plot. As revealed by Principal Response Curves and broken stick models, herbaceous species composition was stable during the first 12–13 years after tree planting, but then abruptly shifted. This two‐step pattern in species turnover followed the increase in canopy cover after tree planting. Once canopy cover passed a threshold of ca 40%, plant succession started and led to the re‐establishment of forest communities 17 years after planting. Following herbaceous species turnover, the cover of ecological groups changed significantly towards covers of natural riparian forests: shade‐tolerant species generally increased, while light‐demanding and non‐native species decreased. Vegetation structure was also significantly affected by tree planting: tree and shrub cover increased, while monocot cover decreased. Synthesis and applications. Tree planting efficiently restored herbaceous forest communities in riparian zones by inducing a species turnover mediated by light availability corresponding to the threshold dynamics model in plant succession. Fostering and monitoring canopy closure in tree‐planted riparian zones should improve restoration success and the design of alternative strategies. The innovative statistical approach of this study aiming to identify succession patterns and their associated theoretical models can guide future restoration in any type of ecosystem around the world to bridge the gap between science and management.

Changes in Structure and Diversity of Woody Plants in a Secondary Mixed Pine-Oak Forest in the Sierra Madre del Sur of Mexico

The biotic province of the Sierra Madre del Sur presents a mosaic of woodlands at different successional stages due to frequent modifications in land use. In this study, we analyzed changes in woody flora across three successional stages of pine-oak forest: early, intermediate, and mature. Vegetation composition and diversity were characterized in 10 plots (each 0.28 ha). The mature stage had the highest values for species richness, abundance, and diversity. Pioneer plants were dominant in the early-successional site and may promote the establishment of late-successional species. The vegetation structure was more complex in the mature stage, where members of the Quercus genus were co-dominant with Pinus species. Pine tree richness was highest in the early-successional stage, and its abundance increased at the intermediate-successional site. These results suggest that Pinus species can grow in perturbed and sunny environments but also require favorable edaphic and microclimatic conditions, such as those found in intermediate woodlands. Results of this fieldwork support the initial floristic composition succession model, which suggests that species present at early stages will also occur in subsequent stages. Ecological succession may be considered to be a natural restoration process, and thus, conservation strategies should focus on maintaining distinct successional communities in addition to mature forests in order to preserve a high number of species.

Sedimentology, diagenesis, clay mineralogy and sequential analysis model of Upper Paleocene evaporite-carbonate ramp succession from Tamerza area (Gafsa Basin: Southern Tunisia)

Integrated sedimentological studies, diagenesis, sequential analysis and clay mineralogy on the Upper Paleocene rocks in Tamerza area provide important information on the reconstruction of the depositional basin, cyclicity, and paleoclimatic contexts. Facies analysis and petrographic studies have led to the recognition of nine facies that were deposited in three facies belts: Sebkha, inner ramp and outer ramp summarized in a carbonate ramp model: Homoclinal ramp under an arid climate.The upward and lateral changes in thickness and composition show a general regressive trend that records a transition from an outer ramp to Sebkha, creating different types of confinement. The facies stacking patterns constitute several kinds of meter-scale, shallowing-upward cycles. Nine different types of depositional cycles and several models of Sebkha sequences were defined. These different types of facies, characterized within the Thelja Formation, compose seven depositional sequences, mainly made of carbonates, marls and evaporates. Detailed multi approach analysis provides important information on evaporitic sequence stratigraphy.In carbonates beds, the diagenetic analysis provides an overview and chronology of diagenetic processes. A particular attention was paid to early stage cementation which enables us to characterize better the depositional environments. In addition to cementation, other features define the diagenetic history.X-ray diffraction reveals the presence of smectite suggesting an arid climate. Moreover, the clinoptilolite and the frequency of primary dolomite indicate different degrees of confinement.The seven depositional sequences showing a hierarchical organization of many cycles, as described above, suggested that eustatic sea level oscillations caused by cyclic perturbations of the Earth's orbit play a fundamental role in determining the formation of hierarchical cyclic rhythmicity.

Principles of geomorphic disturbance and recovery in response to storms

AbstractThe most important geomorphic responses to storms are qualitative changes in system state. Minor storms produce no state change or very rapid recovery to pre‐storm state, and extinction events wipe out the system. In other cases disturbance results in a state change, which may be transitional (change to a previously existing state), state space expansion (change to a new state), and clock‐resetting events that return the system to its initial state. Recovery pathways are much more varied than the monotonic progressions represented in classic vegetation succession and linear channel evolution models. Those linear sequential pathways are only one of several archetypal recovery pathways, which also include binary, convergent, divergent, and more complex networks. Filter‐dominated systems are more likely to follow linear sequential or convergent patterns, whereas amplifier‐dominance is characteristic of divergent and more complex mesh or fully‐connected patterns. Amplifier domination is also more likely to lead to evolutionary or state space expansion responses. Amplification and filtering in geomorphic response and recovery can be assessed using the 'Four R's' framework of response, resistance, relaxation, and recursion. High resistance and resilience, rapid relaxation times, and stable recursive feedback networks reduce or offset effects of disturbances, thus filtering their impacts. Conversely, low resistance and resilience, slow relaxation, and dynamically unstable feedbacks can exaggerate disturbances, creating disproportionately large and long‐lived impacts, thereby amplifying disturbances.Unless new filter mechanisms evolve (either autogenically or anthropically), or the number of extinction or clock‐resetting events increases, intensified storminess will result in more geomorphic variability. These ideas are applied to a case study of a flood on the Clark Fork River, Montana, USA. Copyright © 2016 John Wiley & Sons, Ltd.

Windthrow modelling in old-growth and multi-layered boreal forests

Windthrow is a recurring disturbance process in regions that are influenced by maritime climates, including boreal forests. Within the circumboreal region, forest management approaches have been adapted to emulate natural disturbance in order to promote biodiversity and ecosystem resilience. Few studies have evaluated windthrow outcomes in natural or managed old-growth boreal mixed-species stands, and these studies are primarily empirical. The objective of this study was to adapt the hybrid empirical-mechanistic ForestGALES_BC model, to investigate windthrow dynamics in natural and managed boreal old-growth stands, under various wind regimes. ForestGALES_BC was updated by adding biomechanical data for balsam fir (Abies balsamea (L.) Mill.) and black spruce (Picea mariana (Mill.) B.S.P.). The model has the ability to simulate damage propagation during wind events by recalculating wind loading on a subject tree after failure of upwind trees. The number of iterations of this recalculation provides insights into the potential for propagation during longer duration storms. A simulation space made up of 500, 20m×20m cells, was created using tree-lists from silviculture systems experiments in north eastern Quebec. The tree-lists for cells within the simulation space were edited to represent the plot conditions at the Quebec experimental sites, allowing simulation of a range of cell- (plot) and matrix-level (landscape) partial harvesting regimes. Above-canopy winds of various speeds were applied in order to test the initiation and propagation of damage within the simulated forest. Simulated outcomes were compared to observations of windthrow 6–7 years after partial harvesting at the field experimental site. Observed damage at the experimental site ranged from 1 to 40% of plot total basal area (mean=14%, se=1.96). For above-canopy wind speeds within the range expected for the experimental site, simulated windthrow levels in partial cuts ranged from 7 to 32% (mean=12%, se=1.94). When the combined effects of wind speed and number of iterations (∼event duration) were investigated, event duration was more important for wind speeds over 20m/s. By enabling simulation of outcomes at the tree, plot (cell) and stand (simulation space) levels, the model allows investigation of a wide range of harvesting strategies, and sets the stage for inclusion of wind disturbance in ecosystem succession models and other stand or landscape-level decision-support tools for forests in windy climates.

Incorporating shape constraints in generalized additive modelling of the height-diameter relationship for Norway spruce

Measurements of tree heights and diameters are essential in forest assessment and modelling. Tree heights are used for estimating timber volume, site index and other important variables related to forest growth and yield, succession and carbon budget models. However, the diameter at breast height (dbh) can be more accurately obtained and at lower cost, than total tree height. Hence, generalized height-diameter (h-d) models that predict tree height from dbh, age and other covariates are needed. For a more flexible but biologically plausible estimation of covariate effects we use shape constrained generalized additive models as an extension of existing h-d model approaches. We use causal site parameters such as index of aridity to enhance the generality and causality of the models and to enable predictions under projected changeable climatic conditions. We develop unconstrained generalized additive models (GAM) and shape constrained generalized additive models (SCAM) for investigating the possible effects of tree-specific parameters such as tree age, relative diameter at breast height, and site-specific parameters such as index of aridity and sum of daily mean temperature during vegetation period, on the h-d relationship of forests in Lower Saxony, Germany. Some of the derived effects, e.g. effects of age, index of aridity and sum of daily mean temperature have significantly non-linear pattern. The need for using SCAM results from the fact that some of the model effects show partially implausible patterns especially at the boundaries of data ranges. The derived model predicts monotonically increasing levels of tree height with increasing age and temperature sum and decreasing aridity and social rank of a tree within a stand. The definition of constraints leads only to marginal or minor decline in the model statistics like AIC. An observed structured spatial trend in tree height is modelled via 2-dimensional surface fitting. We demonstrate that the SCAM approach allows optimal regression modelling flexibility similar to the standard GAM but with the additional possibility of defining specific constraints for the model effects. The longitudinal character of the model allows for tree height imputation for the current status of forests but also for future tree height prediction.

Forest succession and population viability of grassland plants: long repayment of extinction debt in Primula veris.

Time lags in responses of organisms to deteriorating environmental conditions delay population declines and extinctions. We examined how local processes at the population level contribute to extinction debt, and how cycles of habitat deterioration and recovery may delay extinction. We carried out a demographic analysis of the fate of the grassland perennial Primula veris after the cessation of grassland management, where we used either a unidirectional succession model for forest habitat or a rotation model with a period of forest growth followed by a clear-cut and a new successional cycle. The simulations indicated that P. veris populations may have an extinction time of decades to centuries after a detrimental management change. A survey of the current incidence and abundance of P. veris in sites with different histories of afforestation confirmed the simulation results of low extinction rates. P. veris had reduced incidence and abundance only at sites with at least 100 years of forest cover. Time to extinction in simulations was dependent on the duration of the periods with favourable and unfavourable conditions after management cessation, and the population sizes and growth rates in these periods. Our results thus suggest that the ability of a species to survive is a complex function of disturbance regimes, rates of successional change, and the demographic response to environmental changes. Detailed demographic studies over entire successional cycles are therefore essential to identify the environmental conditions that enable long-term persistence and to design management for species experiencing extinction debts.

The effect of intergenerational value divergence on post-succession change in Chinese family firms

This paper focuses on the antecedents of changes made by family business successors’ post-succession period and introduces an inter-generational value-based succession model using a multiple-case s...

Quantifying the Adaptive Cycle

The adaptive cycle was proposed as a conceptual model to portray patterns of change in complex systems. Despite the model having potential for elucidating change across systems, it has been used mainly as a metaphor, describing system dynamics qualitatively. We use a quantitative approach for testing premises (reorganisation, conservatism, adaptation) in the adaptive cycle, using Baltic Sea phytoplankton communities as an example of such complex system dynamics. Phytoplankton organizes in recurring spring and summer blooms, a well-established paradigm in planktology and succession theory, with characteristic temporal trajectories during blooms that may be consistent with adaptive cycle phases. We used long-term (1994–2011) data and multivariate analysis of community structure to assess key components of the adaptive cycle. Specifically, we tested predictions about: reorganisation: spring and summer blooms comprise distinct community states; conservatism: community trajectories during individual adaptive cycles are conservative; and adaptation: phytoplankton species during blooms change in the long term. All predictions were supported by our analyses. Results suggest that traditional ecological paradigms such as phytoplankton successional models have potential for moving the adaptive cycle from a metaphor to a framework that can improve our understanding how complex systems organize and reorganize following collapse. Quantifying reorganization, conservatism and adaptation provides opportunities to cope with the intricacies and uncertainties associated with fast ecological change, driven by shifting system controls. Ultimately, combining traditional ecological paradigms with heuristics of complex system dynamics using quantitative approaches may help refine ecological theory and improve our understanding of the resilience of ecosystems.

Long-Term Patterns in the Population Dynamics of Daphnia longispina, Leptodora kindtii and Cyanobacteria in a Shallow Reservoir: A Self-Organising Map (SOM) Approach.

The recognition of long-term patterns in the seasonal dynamics of Daphnia longispina, Leptodora kindtii and cyanobacteria is dependent upon their interactions, the water temperature and the hydrological conditions, which were all investigated between 1999 and 2008 in the lowland Sulejow Reservoir. The biomass of cyanobacteria, densities of D. longispina and L. kindtii, concentration of chlorophyll a and water temperature were assessed weekly from April to October at three sampling stations along the longitudinal reservoir axis. The retention time was calculated using data on the actual water inflow and reservoir volume. A self-organising map (SOM) was used due to high interannual variability in the studied parameters and their often non-linear relationships. Classification of the SOM output neurons into three clusters that grouped the sampling terms with similar biotic states allowed identification of the crucial abiotic factors responsible for the seasonal sequence of events: cluster CL-ExSp (extreme/spring) corresponded to hydrologically unstable cold periods (mostly spring) with extreme values and highly variable abiotic factors, which made abiotic control of the biota dominant; cluster CL-StSm (stable/summer) was associated with ordinary late spring and summer and was characterised by stable non-extreme abiotic conditions, which made biotic interactions more important; and the cluster CL-ExSm (extreme/summer), was associated with late spring/summer and characterised by thermal or hydrological extremes, which weakened the role of biotic factors. The significance of the differences between the SOM sub-clusters was verified by Kruskal-Wallis and post-hoc Dunn tests. The importance of the temperature and hydrological regimes as the key plankton-regulating factors in the dam reservoir, as shown by the SOM, was confirmed by the results of canonical correlation analyses (CCA) of each cluster. The demonstrated significance of hydrology in seasonal plankton dynamics complements the widely accepted pattern proposed by the plankton succession model for lakes, the PEG (Plankton Ecology Group), and may be useful for the formulation of management decisions in dam reservoirs.

Low-sulfide PGE mineralization in layered intrusion ring, Vestfold Hills, Antarctica

This paper presents results of the study of norite complex from the Vestfold Hills (East Antarctica) containing a low-sulfide type of mineralization. The ore mineralization occurs in specific rock types and along the contact of norites the host rocks. Three mineralization types: Fe–Ni–Cu sulfide, oxide, and PGE-bearing are known. PGE mineralization is represented by palladium–bismuth tellurides of the michenerite–merenskyite series. A model of ore-formation succession and a concept of the origin of low-sulfide PGE mineralization by means of crystallization and subsequent evolution of monosulfide and intermediate solid solutions have been developed.

Contrasts in short- and long-term responses of Mediterranean reptile species to fire and habitat structure.

Changes in habitat structure constitute a major factor explaining responses of reptiles to fire. However, few studies have examined habitat factors that covary with fire-history variables to explain reptile responses. We hypothesise that more complex habitats should support richer reptile communities, and that species-specific relative abundance should be related to particular habitat features. From spring 2012-2014, twenty-five transects were surveyed in the Albera Region (north-east Iberia). The vegetation structure was measured and the extent of habitat types in a 1000-m buffer around each transect calculated. Reptile-community metrics (species richness and reptile abundance) were related to fire history, vegetation structure, and habitat types, using generalized additive models. These metrics correlated with habitat-structure variables but not with fire history. The number of species increased with more complex habitats but decreased with pine-plantation abundance in the 1000-m buffer. We found contrasting responses among reptiles in terms of time since fire and those responses differed according to vegetation variables and habitat types. An unplanned fire in August 2012 provided the opportunity to compare reptile abundance values between pre-fire and the short term (1-2 years) after the fire. Most species exhibited a negative short-term response to the 2012 fire except Tarentola mauritanica, a gecko that inhabits large rocks, as opposed to other ground-dwelling species. In the reptiles studied, contrasting responses to time since fire are consistent with the habitat-accommodation model of succession. These differences are linked to specific microhabitat preferences and suggest that functional traits can be used to predict species-specific responses to fire.

Testing a model of biological soil crust succession

AbstractQuestionBiocrust composition is important for the diversity, structure and function of dryland ecosystems globally, but there is no universally applicable model of biocrust succession, and the models that do exist may not apply everywhere. We ask: (1) how do biocrust species vary in their response to time since livestock exclusion (Time) across environmental gradients; (2) is there evidence for ruderal, mid‐ and late successional responses to Time in biocrust species; (3) can exploration of species attributes within response groups reveal potential mechanisms for biocrust succession; and (4) do our data support an existing standard conceptual model of biocrust succession described in the literature.LocationSemi‐arid woodlands of northwest Victoria, Australia.MethodsWe use data from a space‐for‐time study of biocrust composition following livestock exclusion and develop a hierarchical regression model of succession amongst a moss‐dominated biocrust community.ResultsTime since livestock exclusion (Time) was the most important driver of biocrust community dynamics in our study region; species varied widely in their response to Time. Succession within this moss‐dominated biocrust community did not follow the general sequence predicted by the standard model of biocrust succession presented in the literature. We classified species by their successional response from model coefficients. All late successional species were short‐statured and closely attached to the soil, whereas nearly all tall‐statured and loosely attached species were classified as mid‐successional.ConclusionsThis study demonstrates the utility of hierarchical models for investigating successional processes at the species and community level, for testing a standard conceptual model of succession and for suggesting hypotheses about underlying trait‐based mechanisms. We propose an alternative model of biocrust succession that distinguishes between succession in favourable and unfavourable environments. We propose species response to Time is mediated by species structural density, which in turn relates to a suite of correlated traits including growth rate and longevity. This alternative conceptual model is useful for its generality.

Selective logging: Do rates of forest turnover in stems, species composition and functional traits decrease with time since disturbance? – A 45 year perspective

Selective logging, the targeted harvesting of timber trees in a single cutting cycle, is globally rising in extent and intensity. Short-term impacts of selective logging on tropical forests have been widely investigated, but long-term effects on temporal dynamics of forest structure and composition are largely unknown. Understanding these long-term dynamics will help determine whether tropical forests are resilient to selective logging and inform choices between competing demands of anthropogenic use versus conservation of tropical forests. Forest dynamics can be studied within the framework of succession theory, which predicts that temporal turnover rates should decline with time since disturbance. Here, we investigated the temporal dynamics of a tropical forest in Kibale National Park, Uganda over 45years following selective logging. We estimated turnover rates in stems, species composition, and functional traits (wood density and diameter at breast height), using observations from four censuses in 1989, 1999, 2006, and 2013, of stems ⩾10cm diameter within 17 unlogged and 9 logged 200×10m vegetation plots. We used null models to account for interdependencies among turnover rates in stems, species composition, and functional traits. We tested predictions that turnover rates should be higher and decrease with increasing time since the selective logging event in logged forest, but should be less temporally variable in unlogged forest. Overall, we found higher turnover rates in logged forest for all three attributes, but turnover rates did not decline through time in logged forest and was not less temporally variable in unlogged forest. These results indicate that successional models that assume recovery to pre-disturbance conditions are inadequate for predicting the effects of selective logging on the dynamics of the tropical forest in Kibale. Selective logging resulted in persistently higher turnover rates, which may compromise the carbon storage capacity of Kibale’s forest. Selective logging effects may also interact with effects from other global trends, potentially causing major long-term shifts in the dynamics of tropical forests. Similar studies in tropical forests elsewhere will help determine the generality of these conclusions. Ultimately, the view that selective logging is a benign approach to the management of tropical forests should be reconsidered in the light of studies of the effects of this practice on long-term forest dynamics.

The preservation of total organic carbon of the Silurian Pridoli strata in the Milaičiai-103 well core of Western Lithuania

The Pridoli series is one of the thickest and most complete stratigraphic intervals of the Silurian as well as other systems of the Lithuanian part of the Baltic sedimentary basin. In this study we present a sequence stratigraphic model of the sedimentary succession in the Milaičiai-103 core section. High resolution trend of concentrations of total organic carbon is presented in the developed stratigraphic context. The variability in the total organic matter amount in different sequence stratigraphic system tracts was statistically evaluated using the generalized linear mixed-effect modeling approach. The statistical analysis revealed that the highest concentrations of total organic carbon in the studied section are expected in a highstand and transgressive system tracts and significantly lower concentrations are expected in a lowstand and falling stage system tracts.

Empfindlichkeit typischer Schweizer Waldbestände auf den Klimawandel

Sensitivity of typical Swiss forest stands to climate change In Switzerland, first climate-induced changes of forest ecosystems can be observed. However, it is widely unknown how and to what extent the typical (widespread) forest stands will respond to future climate change. With the data of the third National forest inventory and the forest succession model ForClim we examined the development 71 typical stands under current and future climatic conditions (A2 emission scenario) with and without management, respectively. The simulations show a weak response until the middle of the century. In contrast, an increased sensitivity towards the end of the century becomes apparent, expressed by declines of basal area at lower elevations, respectively increases at higher elevations. The responses of forest stands are depending on site-specific characteristics. For example, Norway spruce is expected to decline up to higher elevations. Our results show an increase of deciduous tree species in higher elevation zones, particularly if management is applied. The impacts of climate change on important forest ecosystems services vary along a bioclimatic elevation gradient. Thereby, current forest management shows approaches how to at least partly counteract adverse effects of climate change. However, target- and site-specific strategies are needed and, particularly with regard to lower elevations, more knowledge on the potential of tree species to adapt is required.

Successional trajectory of the fouling community on a tropical upwelling ecosystem in southeast Rio de Janeiro, Brazil

Abstract The present study describes the successional trajectory of the fouling community in the upwelling region of Cabo Frio in southeastern Rio de Janeiro, Brazil. For 12 months, five PVC panels were sampled monthly by underwater photography to record the percent cover of fouling organisms, which allowed for the evaluation of the successional process through functional groups. The variability in the composition of the fouling community increased throughout the successional trajectory, creating a mosaic pattern. The identification of two associations after a year of observation, with one characterized by filamentous algae, Hydrozoa and Cirripedia and another mainly by articulated calcareous algae, shows that divergent trajectories can be observed even under the same environmental conditions. As an important seasonal factor of the local oceanographic characteristics, the upwelling events allowed for an environmental heterogeneity, and rejecting the classic orderly and directional succession model.

Changing gears during succession: shifting functional strategies in young tropical secondary forests.

Adaptations to resource availability strongly shape patterns of community composition along successional gradients in environmental conditions. In the present study, we examined the extent to which variation in functional composition explains shifts in trait-based functional strategies in young tropical secondary forests during the most dynamic stage of succession (0-20 years). Functional composition of two size classes in 51 secondary forest plots was determined using community-weighted means of seven functional traits, which were intensively measured on 55 woody plant species (n = 875-1,761 individuals). Along the successional gradient in forest structure, there was a significant and consistent shift in functional strategies from resource acquisition to resource conservation. Leaf toughness and adult plant size increased significantly, while net photosynthetic capacity (A(mass)) decreased significantly during succession. Shifts in functional strategies within size classes for A(mass) and wood density also support the hypothesis that changes in functional composition are shaped by environmental conditions along successional gradients. In general, 'hard' functional traits, e.g., A(mass) and leaf toughness, linked to different facets of plant performance exhibited greater sensitivity to successional changes in forest structure than 'soft' traits, such as leaf mass area and leaf dry matter content. Our results also suggested that stochastic processes related to previous land-use history, dispersal limitation, and abiotic factors explained variation in functional composition beyond that attributed to deterministic shifts in functional strategies. Further data on seed dispersal vectors and distance and landscape configuration are needed to improve current mechanistic models of succession in tropical secondary forests.