Late Successional Stages Research Articles

Biodiversity conservation effectiveness provided by a protection status in temperate forest commons of north Spain

The establishment and maintenance of protected areas is the backbone of global conservation strategies to halt biodiversity loss. However, despite the more than 200,000 legally designated protected sites worldwide, the rate of species extinction has not decreased, for which some debate the real effectiveness of protected areas to preserve biodiversity. Using data from tropical areas, many studies have attempted to test the effectiveness of protected areas by comparing species richness in protected and neighbouring unprotected sites, without reaching a consensus. Here, we extend this line of research with data from temperate deciduous forests inside and outside Picos de Europa National Park and Biosphere Reserve (N Spain). Specifically we compare data from mixed broadleaved woodlands, beech forests (Fagus sylvatica L.) and Pyrenean oak (Quercus pyrenaica Willd.) forests. We conducted botanical inventories and recorded ecological data from 25 0.2-ha concentric plots distributed in forest commons inside the reserve and from other 25 similar plots established in neighbouring not protected forest commons. Data were used to construct a set of ecological indicators and evaluated using modelling methods. We found no significant differences in species composition between plots in protected and non-protected forest commons, likely due to the similar management criteria applied in both land uses. We found less active management outside the protected area, which helps to maintain stands in a semi-natural state. In contrast, we observed the presence of silvicultural treatments inside the protected area, although these treatments were non-intensive, promoting vegetation composition associated to late-successional ecosystems. We only detected significant differences between plots inside and outside the protected area when relation between species richness was analysed with reference to forest habitat type. Precisely, plots of beech forests inside Picos de Europa were more homogenous than plots outside the protected area, which may indicate that management practices inside the protected area do not favour tree species diversity. Non-intensive silviculture management in beech forests inside Picos de Europa seems to promote the presence of the dominant tree species Fagus sylvatica L., which in the absence of perturbations is characterized by conforming monospecific vegetation communities. Overall, our results do not support the idea that protected areas hold more biodiversity than surrounding forest commons. Conservation treatments applied in protected areas should promote the presence of species associated to disturbances, particularly in stands tending to homogeneous species composition at late-successional stages, as this may enhance their resilience under the current rapid global changes.

Changes of mycorrhizal fungal community occurring during the natural restoration after the chi-chi earthquake in Taiwan

Arbuscular mycorrhizal (AM) fungi influence the plant establishment after disturbances, however, there were no reports on the succession of soil AM fungal communities after earthquakes. This study was carried out to monitor the changes of AM fungal species composition during plant succession after earthquakes. After a major earthquake, the ‘Chi-Chi’ event of 1999, a total of 4238 AM fungal spores belonging to 13 species were recorded. Higher AM fungal spore density was found in the crest area of the affected mountainside and the AM fungal community was significantly different between the crest and valley area. Scutellospora nigra, Acaulospora scrobiculata and Acaulospora tuberculata were dominant in the early succession stage. Glomus ambisporum, Glomus deserticola and Acaulospora mellea were more abundant in the late successional stage. These results demonstrated the dynamics of AM fungal community during succession and vegetation recovery.

Potential for synergy in soil inoculation for nature restoration by mixing inocula from different successional stages

Background and aimsSoil inoculation is a powerful tool for the restoration of terrestrial ecosystems. However, the origin of the donor material may differentially influence early- and late-successional plant species. Donor soil from late-succession stages may benefit target plant species due to a higher abundance of soil-borne mutualists. Arable soils, on the other hand, may suppress ruderals as they support more root herbivores that preferentially attack ruderal plant species, while mid-succession soils may be intermediate in their effects on ruderals and target species performance. We hypothesized that a mixture of arable and late-succession inocula may outperform pure late-successional inocula for restoration, by promoting late-successional target plants, while simultaneously reducing ruderal species’ performance.MethodsWe conducted a glasshouse experiment and tested the growth of ruderal and target plant species on pure and mixed inocula. The inocula were derived from arable fields, mid-succession grasslands and late-succession heathlands and we created a replacement series testing different pairwise mixitures for each of these inocula types (ratios: 100:0, 75:25, 50:50, 25:75, 0:100 of inoculum A and B respectively).ResultsIn general, we found that a higher proportion of heathland material led to a higher aboveground biomass of target plant species, while responses of ruderal species were variable. We found synergistic effects when specific inocula were mixed. In particular, a 50:50 mixture of heathland and arable soil in the inoculum led to a significant reduction in ruderal species biomass relative to the two respective pure inocula. The overall response was driven by Myosotis arvensis, since the other two ruderal species were not significantly affected.ConclusionsMixing inocula from different successional stages can lead to synergistic effects on restoration, but this highly depends on the specific combination of inocula, the mixing ratio and plant species. This suggest that specific inocula may need to be developed in order to rapidly restore different plant communities.

Nutrient retention during ecosystem succession: a revised conceptual model

We propose an important revision to a previously published conceptual model of nutrient retention during terrestrial ecosystem succession, which predicted that ecosystem losses of limiting nutrients such as nitrogen (N) should increase as rates of biomass accumulation slow during late stages of succession. This revision explicitly recognizes that mineral soil horizons (the layers of subsoil beneath the organic‐rich surface layers) can behave as an “N bank”, serving as a source of N for growing forests early in secondary succession and as a sink for N later in succession as plant biomass accumulation slows. If this soil N sink were present, mature forests would continue to retain N for decades following the cessation of biomass accumulation. This conceptual model is consistent with long‐term data collected from the Hubbard Brook Experimental Forest in the US state of New Hampshire, where existing N budgets that exclude the mineral soil horizon indicate both a missing source early in succession and a missing sink as the forest has matured.

The effect of urban park landscapes on soil Collembola diversity: A Mediterranean case study

By increasing landscape patchiness and habitat loss, urbanization threatens biodiversity. Its adverse effects may be mitigated by urban parks, in which conditions that promote structural and functional biodiversity contribute to preserve ecosystem processes. Therefore, deep knowledge of urban park biodiversity and of patterns driving species assemblages is required, especially for soil communities which are understudied. This study, conducted in public parks in Montpellier (Southern France), is the first one examining the impact of landscape patterns on Collembola communities. Moreover, soil abiotic properties were analyzed to examine how local factors drive species assemblages in different landscape types. The results of the study highlighted that Collembola community structure is affected by landscape patterns. Specifically, Collembola communities with species-abundance structures typical of late successional stages were found within woody landscapes, whereas those with early successional stage structures were observed in wide turf patches surrounded by other vegetation covers. When turf patches become small and isolated, homogenization was observed in Collembola community composition. From the perspective of urban park planning, managers should consider limiting landscape fragmentation (i.e. interspersion and configuration of impervious surfaces) and preserving landscape diversity (especially through woody vegetation patches). These may promote the development of diverse and structured Collembola communities, indicators of the overall soil quality.

Eco-exergy based self-organization of the macrobenthic faunal assemblage during mangrove succession in Zhanjiang, China

Eco-exergy (ecological exergy) has been used to evaluate the health and self-organization of aquatic and wetland ecosystems following perturbation or natural succession. Although macrobenthic fauna are important components of mangrove ecosystems, their self-organization during mangrove succession is unclear. In this study, eco-exergy was used to quantify the self-organization processes of macrobenthic faunal assemblages in a mangrove chronosequence that included a primary (unvegetated shoal), early (Avicennia marina), middle (Aegiceras corniculatum), and late (Bruguiera gymnorrhiza + Rhizophora stylosa) community in Zhanjiang, China. Eco-exergy and biomass of the macrobenthic faunal community tended to decrease in the wet season during mangrove succession. The specific eco-exergy of the macrobenthic faunal community, in contrast, remained relatively constant in both wet and dry seasons during mangrove succession, although mollusk eco-exergy tended to decrease and arthropod eco-exergy tended to increase. Statistical analyses indicated that the self-organization of the macrobenthic faunal community during mangrove succession was mainly associated with the development of a suite of vegetation characteristics and sediment physicochemical properties, e.g., plant crown breadth, plant density, sediment ammonium nitrogen and sediment total nitrogen. Unlike the diversification trends of species richness and functional groups, this study confirmed the decreased self-organization trend of macrobenthic fauna assemblage mainly derived from biomass and genetic information. These results highlight the importance of conserving the macrobenthic faunal community in mangrove forests, especially in the late successional stages.

Effects of canopy structure and species diversity on primary production in upper Great Lakes forests

Canopy structure and tree species diversity, shaped by succession, disturbance, and community composition, are linked to numerous ecosystem functions, including net primary production (NPP). Understanding of how ecosystem structural metrics are interrelated and mechanistically link to NPP, however, is incomplete. We characterized leaf area index (LAI), Simpson's index of Diversity (D', a measure of species diversity), and canopy rugosity (Rc, a measure of canopy physical complexity) in 11 forest stands comprising two chronosequences varying in establishing disturbance, and in three late successional communities. We related LAI, D', and Rc to wood NPP (NPPw), and examined whether absorption of photosynthetically active radiation and light use-efficiency (LUE) link NPPw with ecosystem structure. We found that recovery of LAI and D' was delayed following more severe establishing disturbances, but that the development of Rc was strikingly conserved regardless of disturbance, converging on a common mean value in late-successional stands irrespective of differences in leaf area index and species diversity. LAI was significantly correlated with NPPw in each stage of ecosystem development, but NPPw was only correlated with Rc in early successional stages and with D' in late successional stages. Across all stands, NPPw was coupled with LAI and Rc, (but not D') through positive relationships with light absorption and LUE. We conclude by advocating for better integration of ecological disciplines investigating structure-function interactions, suggesting that improved understanding of such relationships will require ecologists to traverse disciplinary boundaries.

Using LiDAR waveform metrics to describe and identify successional stages of tropical dry forests

During the past several decades, full-waveform LiDAR has been widely employed to estimate biophysical and biochemical attributes of forests. Many LiDAR metrics have been proposed for distinguishing tree species. However, little work has been dedicated to identifying tools for accurately classifying forests in different levels of ecological succession. This paper explores the potential of full-waveform LiDAR metrics in the identification and classification of tropical dry forests (TDFs) at three levels of ecological succession: early, intermediate, and late. Based on the effective LiDAR waveform and the cumulative return energy curve from the Laser Vegetation Imaging Sensor (LVIS), we derived a total of 21 LiDAR metrics which can be classified into point-, line-, area-, or shape-based groups. We further evaluated their ability in differentiating TDF succession using multiple comparison analysis (Duncan method and Tamhane’s T2 method) and ISODATA clustering. Our results showed that the response of LiDAR energy could well reflect the variation in TDF vertical structure. The effective LiDAR waveform of the early successional stage was characterized by one narrow peak; the late successional stage was characterized by multiple major and minor peaks; and the intermediate stage showed transitional characteristics. The normalized cumulative curves tended to be linear with the development of succession. Our multiple comparison analysis suggested that shape- and area-based metrics were generally better than point- and line-based ones in the differentiation of successional stages. Meanwhile the late successional stage can be identified by metrics from any of the four metric groups, the early and intermediate successional stages can be better identified using shape- or area-based metrics. Our ISODATA classification results further confirmed the advantages of area-based metrics since they presented the highest accuracies in nearly all accuracy measurements and for all successional stages. Our study suggests the encouraging potential of LiDAR waveform metrics in the quantification of tropical forests structure as a function of different levels of ecological succession.

Biodiversity along temperate forest succession

Abstract The successional dynamics of forests—from canopy openings to regeneration, maturation, and decay—influence the amount and heterogeneity of resources available for forest‐dwelling organisms. Conservation has largely focused only on selected stages of forest succession (e.g., late‐seral stages). However, to develop comprehensive conservation strategies and to understand the impact of forest management on biodiversity, a quantitative understanding of how different trophic groups vary over the course of succession is needed. We classified mixed mountain forests in Central Europe into nine successional stages using airborne LiDAR. We analysed α‐ and β‐diversity of six trophic groups encompassing approximately 3,000 species from three kingdoms. We quantified the effect of successional stage on the number of species with and without controlling for species abundances and tested whether the data fit the more‐individuals hypothesis or the habitat heterogeneity hypothesis. Furthermore, we analysed the similarity of assemblages along successional development. The abundance of producers, first‐order consumers, and saprotrophic species showed a U‐shaped response to forest succession. The number of species of producer and consumer groups generally followed this U‐shaped pattern. In contrast to our expectation, the number of saprotrophic species did not change along succession. When we controlled for the effect of abundance, the number of producer and saproxylic beetle species increased linearly with forest succession, whereas the U‐shaped response of the number of consumer species persisted. The analysis of assemblages indicated a large contribution of succession‐mediated β‐diversity to regional γ‐diversity. Synthesis and applications. Depending on the species group, our data supported both the more‐individuals hypothesis and the habitat heterogeneity hypothesis. Our results highlight the strong influence of forest succession on biodiversity and underline the importance of controlling for successional dynamics when assessing biodiversity change in response to external drivers such as climate change. The successional stages with highest diversity (early and late successional stages) are currently strongly underrepresented in the forests of Central Europe. We thus recommend that conservation strategies aim at a more balanced representation of all successional stages.

Managing Successional Stage Heterogeneity to Maximize Landscape-Wide Biodiversity of Aquatic Vegetation in Ditch Networks.

The presence of a high diversity of different successional stages in a landscape may help to conserve and promote landscape-wide biodiversity. A strategy to achieve this is using Cyclic Rejuvenation through Management (CRM), an approach employed in a variety of different ecosystems. CRM periodically resets the successional stages in a landscape. For aquatic systems this constitutes vegetation removal and dredging. For this approach to be useful (a) successional stages are required to be different in community composition and (b) these differences need to be caused by true replacement of species between stages. While potentially valid, these assumptions are not generally tested prior to application of CMR. In this study we test these assumptions to explore the usefulness of managing on successional stage heterogeneity for maximizing landscape-wide aquatic plant diversity. We carried out vegetation surveys in the ditch networks of 21 polder landscapes in Netherlands, each containing 24 ditch reaches. Using a clustering approach combined with insight from literature on vegetation succession in these systems we assigned our sampled communities to defined successional stages. After partitioning landscape diversity into its alpha and beta components, we quantified the relative importance of replacement among successional stages. Next, through scenario analyses based on simulations we studied the effects of reducing successional stage heterogeneity on landscape-wide biodiversity. Results showed that differences in community composition among successional stages were a potentially important factor contributing to landscape diversity. Early successional stages were characterized by higher replacement of species compared to late successional stages. In a scenario of gradual decrease of heterogeneity through the systematic loss of the earliest successional stages we found 20% of the species richness in a polder was lost, pointing toward the importance of maintaining early successional stages in a polder. This makes a compelling case for application of CRM within agricultural drainage ditch landscapes to maximize regional aquatic plant diversity. While applied to drainage ditch systems, our data-driven approach is broadly applicable to other systems and may help in providing first indications of the potential of the CRM approach. We argue that CRM may maintain and promote regional biodiversity without compromising the hydrological function of the systems.

Linking soil bacterial and fungal communities to vegetation succession following agricultural abandonment

Globally, the rate and extent of cropland abandonment increase greatly since 1950s. Knowledge of soil bacteria and fungi succession during long-term vegetation development is particularly limited for the abandoned croplands. In order to test the effects of agricultural abandonment on soil biota succession, we studied the soil bacterial and fungal composition and diversity in abandoned farmlands across a century of secondary vegetation successional gradient in China’s Qinling Mountains. Using high-throughput sequencing technologies, the soil fungal and bacterial communities were studied in 22 abandoned farmlands, as well as 7 adjacent arable fields representing non-abandoned references. The stand age, i.e., years since agricultural abandonment, affected the soil bacterial and fungal composition and explained 8.7 and 31.6% variations of bacterial and fungal communities (at order level), repectively. The Proteobacteria, dominated by chemoorganotrophic bacteria, kept its absolute dominance status (38.66% - 40.77%) constantly during succession even though the vegetation changed obviously from crop to grass, shrub, and forest. The relative abundances of Acidobacteria, Planctomycetes, Verrucomicrobia, Nitrospirae, and Spirochaetes increased significantly with stand age (i.e., years since abandonment), while the Firmicutes, Actinobacteria, Gemmatimonadetes, Cyanobacteria, and Armatimonadetes showed an opposite trend. A distinct shift in fungal communities from Ascomycota -dominant in young stands to Basidiomycota -dominant in older stands was observed, which could be attributed to the increase of vegetation coverage and soil moisture during succession. The soil bacterial richness and diversity increased logarithmically with increasing stand age and gradually reached equilibrium in late-successional stage. Soil fungal diversity tended to increase in the early successional stages and then followed by a decreasing trend. The soil pH was the most important environmental factor predicating the soil fungal α-diversity measurements. Both the soil bacterial and fungal communities displayed successional trends along with vegetation succession. The soil bacteria and fungi exhibited marked differences in successional pattern during secondary succession following agricultural abandonment.

The Impact of Anthropogenic Intervention on the Walauwewaththa Wathurana Fresh Water Swamp Forest in Sri Lanka

Swamp forests are considered as the late succession stage of a freshwater marsh ecosystem and it is the rarest wetland type in Sri Lanka, rich in biodiversity thus providing a number of ecosystem services. The Walauwewatta Wathurana has been identified as the most dynamic fresh water ecosystem in Sri Lanka. These rare forest ecosystems have been subjected to degradation over the past decades due to various reasons especially anthropogenic activities. A study was conducted to explore the magnitude of these impacts caused by anthropogenic activities. A household survey was conducted using a structured questioner and Participatory Rural Appraisals (PRA) and discussions were made to gather information from the people living close by the swamp. Data analysis based on both quantitative and qualitative techniques. It was revealed that, a large number of activities carried out in the surrounding area of the forest by the neighboring communities directly or indirectly were related to their livelihoods as well as for their daily household needs. The richness of the species and the abundance have decreased over the past two decades due to the unsustainable fishing activities, contamination of agro-chemicals as well as chemical effluents of rubber based industries, sand mining, bamboo and rattan industries located around the forest area. Therefore the Wathurana fresh water swamp forest has been subjected to degradation due to anthropogenic activities. Conservation strategies should be implemented to strengthen the sustainability of the ecosystem services provided by this freshwater swamp forest.

Decreased occurrence of carbon cycle functions in microbial communities along with long-term secondary succession

The succession of microbial community structure and function is a central ecological topic; however, the mechanisms that underlie community assembly and promote temporal succession remain unclear. We studied microbial community-associated functional dynamics in a well-established secondary successional chronosequence that spans approximately 160 years of ecosystem development on the Loess Plateau of China, by sequencing both 16S and ITS rRNA genes and soil metagenomes, resulting in a total of 132.5 Gb of data. Notably, both bacterial and fungal communities shifted with succession, but the microbial community changed little from the pioneer forest stage (approximately 110 years) to the latter successional forest stage. Fungi showed higher variability with succession than bacteria, and the shift of both the bacterial and fungal communities was related more to the soil characteristics than to the litter characteristics. Shifts in soil microbial functions were associated with microbial phylogenetic changes, but microbial gene function also showed changes in the absence of phylogenetic changes at the late successional stages. The reduction in microbial C cycle genes was related to a decrease in litter decomposition ability, thus resulting in a steady state of nutrient cycle in the ecosystem. In addition, high microbial respiration in nutrient-rich soil does not necessarily indicate high microbial decomposition functions; the latter also depend on the abundance of related genes, on enzyme activity and on the physicochemical properties of the litter. Our study provides a metagenome profile of a successional chronosequence and provides insight into the mechanisms underlying the soil microbe-driven functional changes in nutrient cycles during succession.

Forest aging, disturbance and the carbon cycle.

Contents Summary 1188 I. Introduction 1188 II. Forest aging and carbon storage 1189 III. Successional trends of NEP in northern deciduous forests 1190 IV. Mechanisms sustaining NEP in aging deciduous forests 1191 Acknowledgements 1192 References 1192 SUMMARY: Large areas of forestland in temperate North America, as well as in other parts of the world, are growing older and will soon transition into middle and then late successional stages exceeding 100yr in age. These ecosystems have been important regional carbon sinks as they recovered from prior anthropogenic and natural disturbance, but their future sink strength, or annual rate of carbon storage, is in question. Ecosystem development theory predicts a steady decline in annual carbon storage as forests age, but newly available, direct measurements of forest net CO2 exchange challenge that prediction. In temperate deciduous forests, where moderate severity disturbance regimes now often prevail, there is little evidence for any marked decline in carbon storage rate during mid-succession. Rather, an increase in physical and biological complexity under these disturbance regimes may drive increases in resource-use efficiency and resource availability that help to maintain significant carbon storage in these forests well past the century mark. Conservation of aging deciduous forests may therefore sustain the terrestrial carbon sink, whilst providing other goods and services afforded by these biologically and structurally complex ecosystems.

When and where does dispersal limitation matter in primary succession?

AbstractPrimary succession encompasses the earliest and most fundamental stages of community assembly. The relative contributions of plant dispersal and ecosystem development, the main drivers that control the rate of primary succession, remain largely unknown, in spite of their central roles in community organization in general. Understanding the contribution of dispersal is especially critical because it casts light on our ability to manage succession resulting from climate change or anthropogenic disturbance.Here, we review the literature in order to understand when and where dispersal limits primary succession. Studies from many systems (tropical, temperate, boreal, arctic, alpine, floodplain forest, desert, mines, volcanic eruption and glacier forelands) show that dispersal limitation occurs consistently in the early stages of primary succession, suggesting that this is a general pattern. On the other hand, we found strong biases in study sites towards the Northern Hemisphere, temperate regions, volcanic eruptions and glacier forelands, which suggests that there are risks in drawing general conclusions about the importance of dispersal for primary succession for other biomes.Little is known about the contribution of dispersal to the later stages of primary succession. We present a recently developed method, multiscale chronosequence comparison that compares rates of succession in similar systems at relatively small and large spatial scales. Rapid succession at small scales compared to large scales suggests that seed dispersal influences succession over time periods of centuries and also limits the development of ecosystem functions such as vegetation cover and soil carbon accumulation.Synthesis: Dispersal limitation likely matters not only in the early stages but also in the late stages of primary succession by controlling the rate at which new species arrive. Both the accumulation of comparable case studies and novel approaches, such as multiscale chronosequence comparisons and factorial experiments, in contrasting biomes, are necessary to clarify the generality or context dependency of the role of dispersal in future primary successions undergoing changing climate.

Functional characteristics of phenolic compounds accumulated in young leaves of two subtropical forest tree species of different successional stages.

The abundance of phenolic compounds (including anthocyanins) in leaves is associated with photosynthetic performance, but the regulatory mechanism is unclear. Schima superba Gardn. et Champ. and Cryptocarya concinna Hance., which exhibit distinct anthocyanin accumulation patterns, are dominant tree species in the early- and late-successional stages, respectively, of subtropical forests in China. RNA-seq and analyses of phenolic concentrations, antioxidant capacity and photosynthetic characteristics were performed on young and mature leaves of these two species under contrasting light conditions. The high-light-acclimated young leaves of S. superba and C. concinna and low-light-acclimated young leaves of C. concinna were red. These red leaves had higher ratios of electron transport rate to gross photosynthesis (ETR:Pgross) and total antioxidant capacity to chlorophyll (TAC:Chl) than did the green leaves, regardless of light conditions. In addition, the red leaves had a higher expression level of the UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT) gene than did the green leaves, irrespective of light conditions. Total antioxidant capacity was positively correlated with flavonoid content in C. concinna leaves and with total phenolic content in leaves of both species under both high and low light. Consistent with the measurements of photosynthetic performance and flavonoids:Chl ratio, photosynthesis-related genes were extensively downregulated and flavonoid-pathway-related genes were extensively upregulated in young leaves relative to mature leaves. Under high and low light, both non-photochemical quenching and TAC:Chl, which serve as different types of photoprotective tools, were enhanced in young leaves of S. superba, whereas only TAC:Chl was enhanced in young leaves of C. concinna. Our results indicate that the biosynthesis of phenolic compounds in young leaves is likely enhanced by an imbalance between photosynthetic electron supply and demand and that flavonoids play a larger role in meditating photoprotection in late-successional species than in early-successional ones.

Biodiversity of biological soil crusts from the Polar Regions revealed by metabarcoding.

Biological soil crusts (BSCs) are amalgamations of autotrophic, heterotrophic and saprotrophic organisms. In the Polar Regions, these unique communities occupy essential ecological functions such as primary production, nitrogen fixation and ecosystem engineering. Here, we present the first molecular survey of BSCs from the Arctic and Antarctica focused on both eukaryotes and prokaryotes as well as passive and active biodiversity. Considering sequence abundance, Bryophyta is among the most abundant taxa in all analyzed BSCs suggesting that they were in a late successional stage. In terms of algal and cyanobacterial biodiversity, the genera Chloromonas, Coccomyxa, Elliptochloris and Nostoc were identified in all samples regardless of origin confirming their ubiquitous distribution. For the first time, we found the chrysophyte Spumella to be common in polar BSCs as it was present in all analyzed samples. Co-occurrence analysis revealed the presence of sulfur metabolizing microbes indicating that BSCs also play an important role for the sulfur cycle. In general, phototrophs were most abundant within the BSCs but there was also a diverse community of heterotrophs and saprotrophs. Our results show that BSCs are unique microecosystems in polar environments with an unexpectedly high biodiversity.

Land-use type strongly shapes community composition, but not always diversity of soil microbes in tropical China

Forest secondary succession and conversion to an agricultural use are rapidly altering tropical forests, and this alteration has consequences on soil microbial communities. Using high-throughput sequencing of 16S rRNA genes and internal transcribed spacer regions, we compared bacteria and fungi community composition and diversity in soils between the three stages of forest succession (primary forest, PF; secondary forest, SF; pioneer plant community dominated by Macaranga denticulate trees, PP) and two agricultural drylands (rubber plantation, RP; Plukenetia volubilis plantation, PV) in Xishuangbanna, a tropical region of China, and identified the factors associated with the shift in community composition across the five land-use types. The results indicated that the most abundant bacterial genera (Bacillus, Kitasatospora, Nitrospira and Streptacidiphilus) were found at differentially relative abundances among the five land-use types. Through the analysis of indicator species, several bacterial species were significantly associated with the PP site; one to four species were significantly associated to the other sites. Strikingly, almost all fungal genera had site-specific characteristic. Soil properties, especially pH and available P and K, were associated with microbial community composition. Across the three stages of forest succession, bacterial and fungal richness and bacterial alpha diversity had the lowest levels in the earliest stage (PP), but there were no significant differences in microbial richness or diversity between the late stages (PF vs. SF). Compared to PF and SF with their similar bacterial and fungal diversity, the agricultural drylands (RP and PV) had higher bacterial richness but lower fungal richness, indicating that both PF and SF can act as reservoirs for the recolonisation of forest-associated microbes. Overall, these results showed a distinct difference in soil microbe taxonomic composition, especially in fungi, among the various land-use types, even at a very small geographical scale (<4 km), but no great difference of microbial diversity was found between the late stages of forest succession and agricultural drylands. Tropical forest succession and forest conversion to agricultural drylands strongly affect the distribution of microbial species, whereas microbial diversity may not always tightly follow the same successional trajectories.

MYRACRODRUON URUNDEUVA FR ALL. (AROEIRA TREE) POPULATION DYNAMICS, DIAMETER GROWTH RATE AND ITS POTENTIAL FOR SUSTAINABLE MANAGEMENT IN SUCCESSIONAL TROPICAL DRY FORESTS OF BRAZIL

ABSTRACT Myracrodruon urundeuva, better known in Brazil as “Aroeira”, is an arboreal species highly used for its commercial and pharmacological value. Despite the high commercial value in the timber market, this species lacks studies analyzing the recovery time and growth in different stages of succession in the Brazilian tropical dry forests. The main objective of this study was to determine growth rates of this species in three successional stages of a tropical dry forest in Mata Seca State Park, in Minas Gerais, Brazil. We measured all individuals (≥5cm of DBH) annually in 18 permanent plots in early, intermediate, and late successional stages over a period of 8 years (2006-2014). We calculated the annual diameter increments for each individual of this species, for each successional stage and by diameter class. We obtained the following mean annual increments by successional stage: early (10.53 mm/yr), intermediate (2.09 mm/yr), and late (2.90 mm/yr). Increment growth rates were similar between the intermediate and late successional stages. The highest incremental increase in diameter was obtained in the diameter classes 5-15 cm and 15-25 cm in the early stage, and for the intermediate stage, maximum increments were found in the 5-15 cm diameter class and 35-45 cm class for the late stage. Results from this study support the conclusion that this tree is not only a pioneering species but that it also tolerates the conditions of advanced successional stages. Given the fast and high diametric increments observed in the early stage of succession and the smaller diametric classes, this species demonstrates great potential for silvicultural management.

Consistent changes in the taxonomic structure and functional attributes of bacterial communities during primary succession.

Ecologists have long studied primary succession, the changes that occur in biological communities after initial colonization of an environment. Most of this work has focused on succession in plant communities, laying the conceptual foundation for much of what we currently know about community assembly patterns over time. Because of their prevalence and importance in ecosystems, an increasing number of studies have focused on microbial community dynamics during succession. Here, we conducted a meta-analysis of bacterial primary succession patterns across a range of distinct habitats, including the infant gut, plant surfaces, soil chronosequences, and aquatic environments, to determine whether consistent changes in bacterial diversity, community composition, and functional traits are evident over the course of succession. Although these distinct habitats harbor unique bacterial communities, we were able to identify patterns in community assembly that were shared across habitat types. We found an increase in taxonomic and functional diversity with time while the taxonomic composition and functional profiles of communities became less variable (lower beta diversity) in late successional stages. In addition, we found consistent decreases in the rRNA operon copy number and in the high-efficient phosphate assimilation process (Pst system) suggesting that reductions in resource availability during succession select for taxa adapted to low-resource conditions. Together, these results highlight that, like many plant communities, microbial communities also exhibit predictable patterns during primary succession.