Natural Colonization Research Articles

The Microevolution and Epidemiology of Staphylococcus aureus Colonization during Atopic Eczema Disease Flare

Staphylococcus aureus is an opportunistic pathogen and variable component of the human microbiota. A characteristic of atopic eczema (AE) is colonization by S. aureus, with exacerbations associated with an increased bacterial burden of the organism. Despite this, the origins and genetic diversity of S. aureus colonizing individual patients during AE disease flares is poorly understood. To examine the microevolution of S. aureus colonization, we deep sequenced S. aureus populations from nine children with moderate to severe AE and 18 non-atopic children asymptomatically carrying S. aureus nasally. Colonization by clonal S. aureus populations was observed in both AE patients and control participants, with all but one of the individuals carrying colonies belonging to a single sequence type. Phylogenetic analysis showed that disease flares were associated with the clonal expansion of the S. aureus population, occurring over a period of weeks to months. There was a significant difference in the genetic backgrounds of S. aureus colonizing AE cases versus controls (Fisher exact test, P = 0.03). Examination of intra-host genetic heterogeneity of the colonizing S. aureus populations identified evidence of within-host selection in the AE patients, with AE variants being potentially selectively advantageous for intracellular persistence and treatment resistance.

Antimicrobial resistant Escherichia coli in the reproductive tract microbiota of cows and sows.

Escherichia coli is a natural colonizer of the urogenital mucosa of healthy females; however it is one of the pathogens associated to reproductive failures in cows and sows. A better knowledge about the characteristics of native E. coli will allow us to differentiate them from pathogenic strains. Ninety autochthonous isolates from the reproductive tract of sows and cows were characterized to determine the phylogenetic profile, antibiotic resistance and virulence factors; also, comparisons between different breeding systems were performed. Vaginal colonization of E. coli was statistically higher in cows (57.5%) than sows (23.8%), and most isolates belonged to the phylogenetic group A: 79.69 and 80.77%, respectively; moreover phylo-groups B1 (12.5 and 11.54%) and D (7.81 and 7.69%) were significantly lower; however, none was classified as B2. Positive associations between virulence factors and group D were found. Isolates with antimicrobial susceptibility were associated with group A and the MDR (Multiple Drug Resistance) was related to the porcine source. These results contribute to the knowledge of extra-intestinal E. coli populations; which could affect the reproductive performance of females.

Restoration of lowland meadows in Austria: A comparison of five techniques

European environmental policy mandates that biodiversity loss should be halted through restoration. However, knowledge about the efficacy of different restoration treatments for lowland meadows is still incomplete. Our study monitored two restoration projects in South-East Austria that served as compensation measures for the loss of species-rich grassland. We compared the efficacy of five restoration techniques: (1) sod transplantation, (2) natural colonization, (3) hay transfer and additions of seed mixtures for (4) wet and (5) bare soils. Over three years, we measured species richness, number of target species, Shannon diversity and similarity to reference sites. We asked: (A) What is the most effective technique for the restoration of lowland meadows? and (B) Is the applied restoration method more important than abiotic site conditions? We included 66 plots (reference and donor sites: 8 plots, restoration sites: 58 plots) in our study. We sampled data on species composition (4m×4m plots) in three consecutive years since restoration initiation, estimated the slope inclination and analyzed soil parameters (K, P, pH). In general, species composition developed towards the reference vegetation for all techniques but sod transplantation produced by far the best result in terms of species richness and similarity to reference sites. By comparison, hay transfer and natural colonization produced intermediate results but performed better than seeding; the latter led to homogenous, species-poor swards. Soil preparation and abiotic site conditions played a minor role in this early stage of the restoration process, though these factors may gain importance in a longer time frame. We found sod transplantation to be a superior method for lowland meadow restoration in our study area but managers must consider its destructive nature and high costs, which might outweigh its benefits. In this light, hay transfer and natural colonization – or a combination of different techniques – could provide less destructive and more cost-effective alternatives.

Home Range, Survival, and Activity Patterns of the Southeastern Pocket Gopher: Implications for Translocation

Abstract The southeastern pocket gopher Geomys pinetis is absent from a large portion of its historical range. Translocation may represent a viable management technique to reestablish populations into suitable habitat. However, several aspects of the species' ecology are poorly understood, making development of an effective translocation approach challenging. Therefore, we used radiotelemetry to examine home range, survival, dispersal, and daily activity patterns of the southeastern pocket gopher in southwestern Georgia. We measured soil and vegetation characteristics within individual home ranges and examined relationships between home range size, habitat variables, and body mass. Mean home range size of 17 radio-tagged pocket gophers was 921.9 m2 (range = 43.4–2246.8 m2). Home range size was positively related to body mass, percent silt at a depth of 25 cm, and soil carbon content at 75 cm and was negatively related to percent sand at 25 cm, percent clay at 50 cm, and ground cover of grasses other than wiregrass Aristida beyrichiana. Survival rate was 0.78 (range = 0.50–1.00) over the 51-wk study, and we documented predation, likely by avian predators, on two individuals. Three individuals dispersed, with a maximum dispersal distance of 319.1 m (range = 143.2–319.1 m), the farthest known southeastern pocket gopher dispersal. Pocket gophers exhibited greater activity from 0000 to 0400 hours and from 1600 to 2000 hours, contrasting previous research that southeastern pocket gophers were equally active throughout the diel period. Our home range size estimates for southeastern pocket gophers are the first determined using radiotelemetry and are considerably smaller than previous estimates. Although we documented dispersal distances more than 300 m, the fragmented nature of current and restored habitats likely will prevent large-scale natural colonization. Our results provide information important for maximizing success in future southeastern pocket gopher translocation efforts.

Restoration of inland brackish vegetation by large‐scale transfer of coastal driftline material

AbstractQuestionDoes large‐scale transfer of coastal driftline material enhance the establishment of inland brackish vegetation?LocationThe Klutenplas of 11 ha, a formerly reclaimed agricultural field, north coast of the Netherlands.MethodsA large quantity of coastal driftline material of local origin was transferred to the restoration site in 2006 after top soil removal in 2005 leaving bare areas for control plots. A priori species composition of the driftline was analysed in a greenhouse germination study. Target species were assigned to saline and brackish ecological species groups and present and historic regional occurrences. Our procedure for selecting target species resulted in a list of 98 species characteristic of terrestrial salt and brackish ecological species groups. The establishment of plant species in the field was recorded annually from 2006 to 2009, with a final survey in 2012. A comparison between locations with and without driftline was made. The entire study site was grazed with sheep.ResultsDriftline material contained 39 species, including 26 target species. During the first 4 yr, the mean number of target species in the established vegetation of driftline plots was significantly higher than in control plots. When corrected for spontaneous occurrence by natural colonization in control plots, 44% of the target species in the established vegetation of driftline plots during the first 4 yr could be attributed to the transferred material. After 7 yr driftline and control plots converged to similar levels, probably as a result of dispersal by wind and animals.ConclusionsTransfer of coastal driftline material enhanced the rate of establishment of inland brackish vegetation for at least the first 4 yr.

Reduced Campylobacter jejuni colonization in poultry gut with bioactive phenolics

This study was designed to determine the effects of bioactive phenolics (BPE) extracted from blackberry (Rubus fruticosus) and blueberry (Vaccinium corymbosum) byproducts/pomaces on Campylobacter jejuni colonization in broiler cecum. We raised a total of 120 Cobb-500 broiler chicks in duplicate trials up to 3 weeks to determine the effect of BPE on the reduction of colonization using a C. jejuni RM1221 marker strain in broiler cecum. We observed that, as a water supplement, 1.0 g Gallic Acid Equivalent (GAE)/L of BPE reduced C. jejuni colonization level by 1 log in three weeks old broiler cecum compared to the control group. 1 g GAE/L of BPE also resulted a complete inhibition of the C. jejuni marker strain in drinking water with a potential for reduced horizontal transfer in poultry flocks. In a separate experiment, we also raised a total of 200 Cobb-500 broilers in duplicate trials up to 6 weeks to investigate natural colonization of Campylobacter in presence of BPE and observed that 1.0 g GAE/L of BPE reduced natural colonization level of Campylobacter by 2 logs in broiler cecum as a water supplement. Relative expression of several C. jejuni stress response genes, including rod shape determining protein (mreB) were down-regulated in the presence of sub-lethal concentration of BPE. Prolonged exposure of C. jejuni to BPE resulted the minimum inhibitory concentration (MIC) of BPE to increase from 0.5 to 1.0 mg GAE/mL; however, after single sub-culture in BPE-free broth, the MIC value revived to 0.5 mg GAE/mL. Findings from this study reveal the high potential of berry phenolics as green antimicrobials against enteric pathogen Campylobacter and application in the reduction of pre-harvest colonization level of Campylobacter in poultry gut.

Methyl jasmonate induction of cotton: a field test of the 'attract and reward' strategy of conservation biological control.

Natural or synthetic elicitors can affect plant physiology by stimulating direct and indirect defence responses to herbivores. For example, increased production of plant secondary metabolites, a direct response, can negatively affect herbivore survival, development and fecundity. Indirect responses include increased emission of plant volatiles that influence herbivore and natural enemy behaviour, and production of extrafloral nectar that serves as a food source for natural enemies after their arrival on induced plants. Therefore, the use of elicitors has potential for the study of basic aspects of tritrophic interactions, as well as application in biorational pest control, i.e. an 'attract and reward' strategy. We conducted a field study to investigate the effects of methyl jasmonate, an elicitor of plant defence responses, on three trophic levels: the plant, herbivores and natural enemies. We made exogenous applications of methyl jasmonate to transgenic cotton and measured volatile emission, extrafloral nectar production and plant performance (yield). We also assessed insect abundance, insect performance, and parasitism and predation of brown stink bug, Euschistus servus, eggs in methyl jasmonate-treated and untreated control plots. Application of methyl jasmonate increased emission of volatiles, in particular, (+)-limonene and (3E)-4,8-dimethyl-1,3,7-nonatriene, and production of extrafloral nectar, but not yield, compared with the control treatment. Despite increased volatile and extrafloral nectar production, methyl jasmonate application did not affect plant bug performance, or mortality of E. servus egg masses, and only marginally influenced insect abundance. Mortality of E. servus eggs varied over the course of the study. Overall, methyl jasmonate treatment affected cotton plant-induced responses, but not the insects that inhabit the plants. Our results were probably influenced by reduced natural enemy colonization of cotton from adjacent non-crop habitats, and subsequent low within-field population recruitment. Much remains to be learned about the effects of exogenous application of plant-produced 'enhancers' on the behaviour of natural enemies before crop physiology can be manipulated to enhance pest control.

Understanding the legacy of widespread population translocations on the post‐glacial genetic structure of the European beech, Fagus sylvatica L.

AbstractAimHuman impacts have shaped species ranges throughout the Holocene. The putative native range of beech, Fagus sylvatica, in Britain was obscured by its late post‐glacial arrival and subsequent extensive management. We sought to differentiate the interacting effects of post‐glacial colonization and anthropic impacts on the current genetic structure and diversity of beech by contrasting phylogeographical signals from putatively natural and translocated populations.LocationSamples were obtained from 42 sites throughout Great Britain.MethodsChloroplast and nuclear microsatellite marker data were interpreted alongside palynological, historical and anecdotal evidence. Genetic structure was analysed using individual‐based Bayesian assignment methods and colonization history was analysed using an approximate Bayesian computation framework.ResultsPhylogeographical patterns suggested contemporary forests originated from putative native south‐eastern populations. High haplotypic diversity was found near the entry point of beech into Britain. Cryptic signals of isolation‐by‐distance persisted in the putative native range, together with higher levels of gene diversity in nuclear markers. Weak regional nuclear genetic structure suggested high levels of contemporary gene flow throughout the country.Main conclusionsGenetic patterns driven by natural colonization persist despite widespread anthropic intervention. Forests in northerly regions were established from forests in the putative native range, diminishing the credibility of any present boundary between the native and non‐native range of beech in Britain.

Effect of Feed Additives on Productivity and Campylobacter spp. Loads in Broilers Reared under Free Range Conditions.

The poultry reservoir, especially broiler meat, is generally recognized as one of the most-important sources for human Campylobacteriosis. The measures to control Campylobacter targeted essentially the primary production level. The aim of this work was to evaluate the effectiveness of different treatments against natural Campylobacter colonization in a French experimental farm of free-range broilers during the whole rearing period. Five commercial products and a combination of two of them were tested and all the products were added to feed or to water at the dose recommended by the suppliers. Campylobacter loads in caeca and on carcasses of broilers at the slaughter were determined by culture methods. Natural contamination of the flock occurred at the end of the indoor rearing period between day 35 and day 42. At day 42, the multispecies probiotic added to the feed reduced the contamination of 0.55 log10 CFU/g (p = 0.02) but was not significant (p > 0.05) at the end of rearing at day 78. However, another treatment, a combination of a cation exchange clay-based product in feed and an organic acid mixture (formic acid, sodium formate, lactic acid, propionic acid) in water, led to a slight but significant reduction of 0.82 ± 0.25 log10 CFU/g (p = 0.02) compared to the control group at day 78. Testing this combination in field conditions in several flocks is needed to determine if it is biologically relevant and if it could be a valuable measure to reduce Campylobacter in broiler flocks.

Effects of native diversity, soil nutrients, and natural enemies on exotic invasion in experimental plant communities.

Many factors can promote exotic plant success. Three of these factors-greater pressure from natural enemies on natives, increased soil nutrient supply, and low native species richness-may interact during invasions. To test for independent and interactive effects of these drivers, we planted herbaceous perennial communities at two levels of native richness (monocultures and five-species polycultures). We then factorially manipulated soil nutrient supply and access to these communities by aboveground foliar enemies (fungal pathogens and insect herbivores), and allowed natural colonization to proceed for four years. We predicted that nutrient addition would increase exotic success, while enemy exclusion and increasing native richness would reduce exotic success. Additionally, we expected that enemy exclusion would reduce the benefits of nutrient addition to exotic species most in species-poor communities, and that this effect would be weaker in species-rich communities. In total, we found no evidence that nutrient supply, enemy access, and native richness interacted to influence exotic success. Furthermore, native richness had no effect on exotic success. Instead, nutrient addition increased, and enemy exclusion decreased, exotic success independently. As predicted, enemy exclusion reduced exotic success, primarily by slowing the decline in abundance of planted native species. Together, these results demonstrate that multiple drivers of exotic success can act independently within a single system.

Relocation and Recolonization of Coho Salmon in Two Tributaries to the Elwha River: Implications for Management and Monitoring

AbstractIn 2012 the lower of two Elwha River dams was breached, restoring access of anadromous salmonids to the middle Elwha River (between the two dams), including two distinct tributaries, Indian Creek and Little River. While comparable in size, Indian Creek is considerably less steep than Little River (mean slope of 1.0% versus 3.5%, respectively) and has a warmer stream temperature regime due to its source, Lake Sutherland. During and after breaching, Coho Salmon Oncorhynchus kisutch were relocated to these tributaries from lower Elwha River hatcheries (below the dams) to determine if individuals from a hatchery‐dominated population would successfully spawn and seed the systems with juveniles and to assess differences in recolonization between the streams. Transplantation led to immediate spawning, which resulted in levels of smolt out‐migrants per stream kilometer comparable with other established Coho Salmon populations in the Pacific Northwest. During the first 2 years of the relocation, redd densities in the two systems were similar but Indian Creek produced four to five times as many smolts per kilometer as Little River. In addition, fry out‐migration occurred 2 to 4 weeks earlier in Indian Creek, as predicted by the warmer incubation temperatures. In the first years of the study, there was little evidence of natural colonization of the two tributaries by adults. However, in 2016 over half of the observed adults returning to the two tributaries were not transplanted, suggesting that the progeny from the transplanted fish were returning to their natal waters. This work demonstrates that transplanting hatchery‐dominated Coho Salmon adults into newly available habitat can result in immediate freshwater production that is comparable to other systems and that density and timing of juvenile out‐migrants can differ dramatically based on the seeded habitat.Received December 9, 2016; accepted March 30, 2017 Published online July 28, 2017

Effects of Planted Versus Naturally Growing Vallisneria natans on the Sediment Microbial Community in West Lake, China.

Submerged macrophytes play an important role in aquatic ecosystems, which has led to an increase in studies on vegetation recovery in polluted lakes from which submerged macrophytes have disappeared. The comparison of microbial communities in sediment cloned with planted and naturally growing submerged macrophytes is an interesting but rarely studied topic. In this investigation, Maojiabu and Xilihu, two adjacent sublakes of West Lake (Hangzhou, China), were selected as aquatic areas with planted and naturally growing macrophytes, respectively. Sediment samples from sites with/without Vallisneria natans were collected from both sublakes. The results showed that sediment total nitrogen and organic matter were significantly lower in the plant-covered sites than that in the non-plant sites in Maojiabu. Additionally, the sediment microbial community characterized by 16S ribosomal RNA (rRNA) sequencing differed more significantly for Maojiabu than for Xilihu. The relative abundances of microbes involved in C, N, and S elemental cycling were significantly higher in the sediments with plants than in those without. Results from both fatty acid methyl ester analysis and 16S rRNA sequencing indicated that vegetation significantly influenced the sulfate-reducing bacteria (SRB). Thus, the gene copies and composition of SRB were explored further. The relative gene abundance of SRB was 66% higher with natural vegetation colonization but was not influenced by artificial colonization. An increase in dominant SRB members from the families Syntrophobacteraceae and Thermodesulfovibrionaceae contributed to the increase of total SRB. Thus, macrophyte planting influences sediment nutrient levels and microbial community more than natural growth does, whereas the latter is more beneficial to sediment SRB.

Colonization with Helicobacter is concomitant with modified gut microbiota and drastic failure of the immune control of Mycobacterium tuberculosis.

Epidemiological and experimental observations suggest that chronic microbial colonization can impact the immune control of other unrelated pathogens contracted in a concomitant or sequential manner. Possible interactions between Mycobacterium tuberculosis infection and persistence of other bacteria have scarcely been investigated. Here we demonstrated that natural colonization of the digestive tract with Helicobacter hepaticus in mice is concomitant with modification of the gut microbiota, subclinical inflammation, and drastic impairment of immune control of the growth of subsequently administered M. tuberculosis, which results in severe lung tissue injury. Our results provided insights upon the fact that this prior H. hepaticus colonization leads to failures in the mechanisms that could prevent the otherwise balanced cross-talk between M. tuberculosis and the immune system. Such disequilibrium ultimately leads to the inhibition of control of mycobacterial growth, outbreak of inflammation, and lung pathology. Among the dysregulated immune signatures, we noticed a correlation between the detrimental lung injury and the accumulation of activated T-lymphocytes. Our findings suggest that the impact of prior Helicobacter spp. colonization and subsequent M. tuberculosis parasitism might be greater than previously thought, which is a key point given that both species are among the most frequent invasive bacteria in human populations.

The influence of site factors and proximity of adjacent vegetation on tree regeneration into roadslopes

Many studies have shown evidence of very rapid natural colonization of trees on roadslopes. Tree colonization on roadslopes can be a useful tool in the ecological restoration of these degraded areas. However, little is known about the characteristics of the tree species capable of colonizing these novel habitats. Moreover, it is necessary to know how tree species respond to the two main limitations in these areas: microsite availability (i.e., roadslope characteristics) and seed arrival, which is related to propagule source, dispersion vector and landscape characteristics. The present study aims to investigate the natural colonization of tree species on roadslopes, as well as the factors determining their occurrence. We identified all tree individuals on 150 roadslopes, along 51km of a motorway. A total of 1143 individuals belonging to 18 species was recorded. Most individuals found resulted from a natural colonization process, although we found various fruit trees (present in 7 roadslopes) and Robinia pseudoacacia (2 roadslopes), which are probably associated with unintentional human-mediated seed dispersal. Only the six most abundant species were analysed in detail: Populus nigra, Quercus ilex, Quercus pyrenaica, Fraxinus angustifolia, Salix spp. and Ulmus pumila. Each roadslope was characterized both by site variables and by surrounding variables. We analysed the effect of the descriptive variables on the occurrence and density of each species on the roadslopes, and we subsequently used decision trees (classification and regression trees) to analyse the combined effect of the different predictors considered. Our results show successful tree colonization on the roadslopes, although they appear to indicate limitations to colonization associated with the availability of propagules. Furthermore, tree species dispersed by animals required a continuous flow of seeds favoured by an appropriate community of seed dispersers and a suitable landscape structure. By contrast, wind-dispersed tree species basically need favourable site characteristics on the roadslopes.

Abundance–occupancy relationships in deep sea wood fall communities

The generally positive relationship between the number of sites a species occupies and its average abundance within those sites provides an important link between population processes occurring at different spatial scales. Although such abundance–occupancy relationships (AORs) have been documented across a very wide range of taxa and in many different environments, little is known of such patterns in Earth's largest ecosystem, the deep sea. Wood falls – derived from natural or anthropogenic inputs of wood into the oceans – constitute an important deep‐sea habitat, habouring their own unique communities ultimately entirely dependent on the wood for chemical energy. In this study we take advantage of the unique features of an experimental wood fall deployment to examine AORs for the first time in deep‐sea invertebrates. The study design combines advantages of both experimental (tractability, control of key environmental parameters) and observational (natural colonisation by taxonomically diverse communities) studies. We show that the interspecific AOR is strongly positive across the 48 species occurring over 32 wood fall communities. The precise form of the AOR is mediated by both species‐level life history (body size) and by the colonisation stage at which communities were harvested, but not by environmental energy (wood fall size). Temporal dynamics within species are also generally consistent with positive intraspecific AORs. This support for positive AORs in the deep sea is an important extension of a macroecological generality into a new environment offering considerable potential for further testing and developing mechanistic macroecological theories.

Genetic diversity of the sweet chestnut (Castanea sativa Mill.) in Central Europe and the western part of the Balkan Peninsula and evidence of marron genotype introgression into wild populations

The sweet chestnut (Castanea sativa Mill.) is a widely spread and important multipurpose tree species in the Mediterranean area, which has played an important role in human history. Natural events, such as glaciations, and human influence played significant roles in the distribution and genetic makeup of the sweet chestnut. In order to better understand how natural and human-mediated past events affected the current genetic diversity and structure of the sweet chestnut, we analysed populations from Central Europe and the western part of the Balkan Peninsula, utilizing ten polymorphic nuclear microsatellite markers. The study revealed the existence of three genetically and, to a large extent, geographically distinct and well-defined groups of sweet chestnut populations. Two not entirely separated groups of populations were detected in the northern part of the studied area and one in the southern. Our results indicate that the genetic structure of sweet chestnut populations in Central Europe and the western part of the Balkan Peninsula is the result of both natural colonization events and significant and lengthy human impact. Furthermore, it has been proven that the gene flow between cultivated/grafted trees’ and wild chestnut stands can influence their genetic structure. However, our results reveal that cultivated-to-wild introgression in the sweet chestnut is dependent on the close proximity of chestnut orchards and naturally occurring populations.

Establishment of woody species across 26 years of revegetation on a Queensland coal mine

SummaryThe establishment success of woody plant species at 56 revegetation sites, four to 26 years old, across the Meandu open‐cut coal mine in south‐east Queensland was assessed. The revegetation process involved returning stockpiled topsoil, deep ripping and mechanical sowing of a mix of native seeds. Blakes Wattle (Acacia blakei) and less often Black Wattle (A. leiocalyx), both primarily derived from respread topsoil seed, dominate the vegetation canopy at 59% and 20% of revegetation sites, respectively. The additional sowing of seeds of many tree and shrub species within the sites has had limited success with most failing to persist or grow well. Revegetation management, for example selective thinning of acacias (Acacia spp.) saplings within the first 5 years is recommended to release the competition pressure on the poorly performing tree species. This will also allow opportunities for other less well represented shrub and herb species to persist. This study has shown that a range of tree and shrub species, including Eucalyptus spp., are performing poorly under the current revegetation regime, suggesting adjustments to revegetation species selection and/or methodologies are needed. The natural colonization of woody native species within the sites from nearby remnant vegetation is shown to be limited to only four species, and therefore is unlikely to significantly supplement the species diversity of the revegetation.

Wetland management strategies lead to tradeoffs in ecological structure and function

Anthropogenic legacy effects often occur as a consequence of land use change or land management and can leave behind long-lasting changes to ecosystem structure and function. This legacy is described as a memory in the form of ecological structure or ecological interactions that remains at a location from a previous condition. We examined how forested floodplain restoration strategy, based on planting intensity, influenced wetland community structure and soil chemical and physical factors after 15 years. The site was divided into 15 strips, and strips were assigned to one of five restoration treatments: plantings of acorns, 2-year-old seedlings, 5-ft bareroot trees, balled and burlapped trees, and natural seed bank regeneration. Our community composition survey revealed that plots planted with bareroot or balled and burlapped trees developed closed tree canopies with little herbaceous understory, while acorn plantings and natural colonization plots developed into dense stands of the invasive species reed canary grass (RCG; Phalaris arundinacea). Restoration strategy influenced bacterial community composition but to a lesser degree compared to the plant community response, and riverine hydrology and restoration strategy influenced wetland soil conditions. Soil ammonium concentrations and pH were similar across all wetland restoration treatments, while total organic carbon was highest in forest and RCG-dominated plots compared to mixed patches of trees and open areas. The differences in restoration strategy and associated economic investment resulted in ecological tradeoffs. The upfront investment in larger, more mature trees (i.e., bareroot, balled and burlapped) led to floodplain forested communities, while cheaper, more passive planting strategies (i.e., seedlings, seedbank, or acorns) resulted in dense stands of invasive RCG, despite the similar floodplain hydrology across all sites. Therefore, recovery of multiple ecosystem services that encompass plant and microbial-derived functions will need to include additional strategies for the recovery of plants, microbes, environment, and functions.

Animating tree colonization and growth

In the early twentieth century the woodland at Heald Brow, north-west England, was largely a tree-less pasture, but changing land management practices lead to natural tree colonization and the development of a mixed deciduous woodland with ash (Fraxinus excelsior), oak (Quercus robur), yew (Taxus baccata) and small-leaved Lime (Tilia cordata) the main components. The research focused on T. cordata due to its rarity and conservation value, and aimed to investigate the timing of its appearance, rates of reproduction by layering and the effects of competition on its longer-term survival. A small, 0.32ha area of woodland was mapped using standard field-based survey methods and increment cores were taken to provide minimum age estimates for living stems of all species present. The spatial and temporal data generated led to the development of a new micro-GIS animation method, using ArcGIS software, that visually highlighted secondary woodland establishment and development, and gave novel insights into the competitive interactions that governed the development. Results showed T. cordata colonization in the 1940s and layering developing in the 1960s. The later appearance and rapid establishment of T. baccata with its light-excluding canopy produced high competition scores and undoubtedly restricted further development of the main T. cordata canopy aided by F. excelsior at the periphery. This animation method and associated GIS analyses have potential application in both dendrochronological, wider ecological research and in conservation management.

Natural Nodulation and AMF Colonization of Retama raetam and their Impact on Soil Microbial Properties in Arid Regions of Tunisia

Natural Nodulation and AMF Colonization of Retama raetam and their Impact on Soil Microbial Properties in Arid Regions of Tunisia