Oligotrophic Habitats Research Articles

Nitrogen deposition and heathland management cause multi‐element stoichiometric mismatches, reducing insect fitness

Abstract Increased nitrogen and acidifying deposition negatively affect biogeochemical cycles and nutrient stoichiometry, particularly in oligotrophic habitats. In heathlands, management aims to mitigate effects of deposition by topsoil removal (sod‐cutting) or by liming to increase soil pH. However, these management efforts may further exacerbate macro‐ and micronutrient stoichiometric mismatch, with cascading effects on heathland insects. Here, we investigate the physiological mechanisms by which deposition and management affect insects, focusing on nutrient uptake and excretion. We combined a phosphorus (P) addition and liming experiment in previously sod‐cut heathland with laboratory‐rearing experiments using the field cricket (Gryllus campestris L., 1) as a model species. We hypothesized that P addition would benefit cricket performance by reducing food N:P ratio. Conversely, we hypothesized that liming would reduce performance by decreasing food Mn:Mg and/or Fe:Mg ratios. Elemental uptake efficiency, consumption and reproduction, as well as cricket field density, were significantly higher under increased P availability, confirming insect P limitation in the field. Liming decreased food Mn:Mg ratio and reduced reproductive success, eliminating any beneficial effects of P addition. Moreover, cricket stoichiometry better explained growth rates than the amount of food consumed. The best model highlighted cricket N and Mn content, with increasing N content negatively influencing growth, while the opposite was true for Mn. We found no support for liming‐induced Fe limitation. We propose that both P and Mn limit crickets independently. Specifically, P limitation affects growth via reduced ribosomal content, and Mn limitation impacts growth by limiting arginase activity and hence restricting the recycling of amino acids. Our study shows that restoration management can fail to restore habitat quality for insects and may even amplify mismatches in macro and micronutrient stoichiometry. To address this, the addition of not only P but also Mn may be required as follow‐up management, but reducing N‐emission remains imperative as this removes the need for disruptive management interventions. Read the free Plain Language Summary for this article on the Journal blog.

Organic fertilizer significantly mitigates N2O emissions while increase contributed of comammox Nitrospira in paddy soils

Nitrification is the dominant process for nitrous oxide (N2O) production under aerobic conditions, but the relative contribution of the autotrophic nitrifiers (the ammonia-oxidising archaea (AOA), the ammonia-oxidising bacteria (AOB) and the comammox) to this process is still unclear in some soil types. This is particularly the case in paddy soils under different fertilization regimes. We investigated active nitrifiers and their contribution to nitrification and N2O production in a range of unfertilized and fertilized paddy soils, using 13CO2-DNA based stable isotope probing (SIP) technique combined with a series of specific nitrification inhibitors, including acetylene (C2H2), 3, 4-dimethylpyrazole phosphate (DMPP) and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO). The soils had a long-term history of fertilizer application, including chemical fertilizer only, a mixture of chemical fertilizers (70 %) and chicken manure (30 %) or a mixture of rice straw and chemical fertilizers. 13CO2-DNA-SIP and Illumina MiSeq sequencing demonstrated that comammox clades A.1 and B were active nitrifiers in all fertilized paddy soils. Inhibitor experiment showed that AOB largely contributed to nitrification activity and N2O emission in all paddy soils, while comammox contribution was more significant than AOA. Fertilization considerably altered nitrifiers' relative contribution to nitrification activity and N2O emissions. Applying organic fertilizers significantly decreased the N2O emissions but increased the contribution of comammox to the process. These findings expand the functional ecological niche of comammox, revealing their nitrification role and N2O production in other ecosystems than oligotrophic habitats.

Adaptations to nitrogen availability drive ecological divergence of chemosynthetic symbionts.

Bacterial symbionts, with their shorter generation times and capacity for horizontal gene transfer (HGT), play a critical role in allowing marine organisms to cope with environmental change. The closure of the Isthmus of Panama created distinct environmental conditions in the Tropical Eastern Pacific (TEP) and Caribbean, offering a "natural experiment" for studying how closely related animals evolve and adapt under environmental change. However, the role of bacterial symbionts in this process is often overlooked. We sequenced the genomes of endosymbiotic bacteria in two sets of sister species of chemosymbiotic bivalves from the genera Codakia and Ctena (family Lucinidae) collected on either side of the Isthmus, to investigate how differing environmental conditions have influenced the selection of symbionts and their metabolic capabilities. The lucinid sister species hosted different Candidatus Thiodiazotropha symbionts and only those from the Caribbean had the genetic potential for nitrogen fixation, while those from the TEP did not. Interestingly, this nitrogen-fixing ability did not correspond to symbiont phylogeny, suggesting convergent evolution of nitrogen fixation potential under nutrient-poor conditions. Reconstructing the evolutionary history of the nifHDKT operon by including other lucinid symbiont genomes from around the world further revealed that the last common ancestor (LCA) of Ca. Thiodiazotropha lacked nif genes, and populations in oligotrophic habitats later re-acquired the nif operon through HGT from the Sedimenticola symbiont lineage. Our study suggests that HGT of the nif operon has facilitated niche diversification of the globally distributed Ca. Thiodiazotropha endolucinida species clade. It highlights the importance of nitrogen availability in driving the ecological diversification of chemosynthetic symbiont species and the role that bacterial symbionts may play in the adaptation of marine organisms to changing environmental conditions.

Lichen biocrusts contribute to soil microbial biomass carbon in the northern temperate zone: A meta‐analysis

AbstractBiological soil crusts (biocrusts) have crucial ecological functions in dryland ecosystems, yet understanding the variations in soil microbial biomass within biocrusts across diverse ecosystems, climates and soil conditions remains limited. This knowledge gap constrains our understanding of how microbial communities within biocrusts regulate terrestrial carbon and nitrogen cycling. Hence, we conducted a meta‐analysis using 255 paired observations from 42 study sites across the northern temperate ecosystem. The analysis revealed that biocrusts harbour significantly higher soil microbial biomass carbon and nitrogen (SMBC and SMBN, respectively) levels than bare (non‐biocrust) soil across all habitat types. Notably, deeper soil layers (5–10 and >10 cm) accumulated less SMBC and SMBN than biocrust and biocrust–5‐cm soil, revealing that biocrusts influence shallow soil environments. Ecosystem type, soil texture, depth and season emerged as key factors influencing the distribution of SMBC within biocrusts. Of particular interest, lichen biocrusts accumulated the most SMBC compared with other biocrust types. Furthermore, the difference in SMBC between biocrust and non‐biocrust soils was more pronounced in oligotrophic habitats (e.g., desert, grassland, sand and sandy loam soils) than in eutrophic habitats (e.g., forest and loam soils). Random forest analysis confirmed that soil variables affected SMBC accumulation in biocrusts more than climatic factors. Soil organic carbon (SOC), as the primary source of SMBC, could be the most important determinant. Moreover, the disparity between non‐biocrust SMBC and biocrust SMBC increased with increasing mean annual temperature (MAT) or decreasing altitude. These insights underscore the substantial contribution of lichen biocrusts to SMBC and emphasize the need to incorporate this knowledge into regional models for predicting the effects of climate change on soil carbon budgets within biocrust microbiomes in temperate ecosystems of the Northern Hemisphere.

Comparative genomics reveals the adaptation of ammonia-oxidising Thaumarchaeota to arid soils.

Thaumarchaeota are predominant in oligotrophic habitats such as deserts and arid soils, but their adaptations to these arid conditions are not well understood. In this study, we assembled 23 Thaumarchaeota genomes from arid and semi-arid soils collected from the Inner Mongolia Steppe and the Qinghai-Tibet Plateau. Using a comparative genomics approach, integrated with 614 Thaumarchaeota genomes from public databases, we identified the traits and evolutionary forces that contribute to their adaptations to aridity. Our results showed that the newly assembled genomes represent an early diverging group within the lineage of ammonia-oxidising Thaumarchaeota. While the genomic functions previously identified in arid soil lineages were conserved across terrestrial, shallow-ocean and deep-ocean lineages, several traits likely contribute to Thaumarchaeota's adaptation to aridity. These include chlorite dismutase, arsenate reductase, V-type ATPase and genes dealing with oxidative stresses. The acquisition and loss of traits at the last common ancestor of arid soil lineages may have facilitated the specialisation of Thaumarchaeota in arid soils. Additionally, the acquisition of unique adaptive traits, such as a urea transporter, Ca2+ :H+ antiporter, mannosyl-3-phosphoglycerate synthase and phosphatase, DNA end-binding protein Ku and phage shock protein A, further distinguishes arid soil Thaumarchaeota. This study provides evidence for the adaptations of Thaumarchaeota to arid soil, enhancing our understanding of the nitrogen and carbon cycling driven by Thaumarchaeota in drylands.

Responses of a polycyclic aromatic hydrocarbon-degrading bacterium, Paraburkholderia fungorum JT-M8, to Cd (II) under P-limited oligotrophic conditions

For the bioremediation of mixed-contamination sites, studies on polycyclic aromatic hydrocarbon (PAH) degradation or Cd (II) tolerance in bacteria are commonly implemented in nutrient-rich media. In contrast, in the field, inocula usually encounter harsh oligotrophic habitats. In this study, the environmental strain Paraburkholderia fungorum JT-M8 was used to explore the overlooked Cd (II) defense mechanism during PAH dissipation under P-limited oligotrophic condition. The results showed that the growth and PAH degradation ability of JT-M8 under Cd (II) stress were correlated with phosphate contents and exhibited self-regulating properties. Phosphates mainly affected the Cd (II) content in solution, while the cellular distribution of Cd (II) depended on Cd (II) levels; Cd (II) was mainly located in the cytoplasm when exposed to less Cd (II), and vice versa. The unique Cd (II) detoxification pathways could be classified into three aspects: (i) Cd (II) ionic equilibrium and dose–response effects regulated by environmental matrices (phosphate contents); (ii) bacterial physiological self-regulation, e.g., cell surface-binding, protein secretion and active transport systems; and (iii) specific adaptive responses (flagellum aggregation). This study emphasizes the importance of considering culture conditions when assessing the metal tolerance and provides new insight into the bacterial detoxification process of complex PAH-Cd (II) pollutants.

Biomass Amounts of Spontaneous Vegetation on Post-Coal Mine Novel Ecosystem in Relation to Biotic Parameters

The amounts of biomass in ecosystems depends on the efficiency of energy gathering in organic chemical bonds by autotrophs, which are the only organisms that synthesize inorganic compounds into organic compounds structured into biomass. Plant species composition in the vegetation patch and the associated microorganism communities are factors that affect the matter and energy flow in the ecosystem. In human-established or severely transformed novel ecosystems, in particular in mineral-poor, oligotrophic habitats, the knowledge about the biotic parameters related to the biomass amount is very limited. The presented studies were performed on post-black coal mining heaps that provide the mineral material habitat. The following biotic parameters, the vegetation plant species composition of the distinguished vegetation types, soil organic matter, soil enzymatic activity, soil fauna presence, and the functional aspect of soil carbon release concerning amount of biomass are considered. The aim of this research was to analyze the influence of the selected biotic factors on the biomass amount in the vegetation patches of the studied sites. The results showed that the effect of the species composition diversity on the biomass amount is complex. The influences of soil enzyme activity on biomass amount are dependent on the enzyme presence and the vegetation type. Similarly, the impact of the soil organic matter (SOM) on the biomass amount is significantly different and dependent on vegetation type. The relationship between the amount of biomass and respiration showed that the biomass of the dominant plant species is positively correlated with the biomass amount in the studied vegetation types.

Радиальный рост ели (Picea abies (L.) Karst. × P. obovata Ledeb.) в условиях горных разработок

A dynamic of radial growth of spruce near a quarry of kimberlite pipes is investigated in this study. The quarry is considered as a potential source of anthropogenic impact. The research takes place at the central part of the White Sea Kuloi plateau, at the diamond deposit named after M.V. Lomonosov. The wood cores for dendrochronological analysis are from six trail plots located at different distances from the active quarry. The annual radial increment of spruce in all plots ranges from medium to high or very high. It is noticed that spruce trees have different durations of depression and expression cycles. The growth rates of the trees from the same plot do not coincide, or they show similarities to certain periods of tree’s life with cyclical patterns. In most cases, minimum and maximum extremes are observed near the well-known values of solar activity cycles. An inverse relationship is found between duration and repetition of the cycles. The measurements from all trail plots show a decrease in the amplitude of radial growth, which started in 2000. It took much greater extent in the period from 2010 to 2019. The samples of the spruce, which were taken from the oligotrophic habitats located near the quarry, indicate an increase of width of annual rings in the last 10–20 years. Fifty percent of them reveal a distinct radial extent. The trees from the most distant trail area are characterized by high simultaneity in the dynamics of the annual layers. Moreover, it is found a decrease in the maximum value of radial growth relative to the entire series of observations. Likewise, a reduce in the amplitude of increments is noted as a rise in the repeatability of relative growth indices below the regular values. It can be assumed that the change in the trend of radial growth in spruce in the oligotrophic habitats is mostly associated with the formation of а depression cone and, as a result, a general lowering of the groundwater level. For citation: Barzut O.S., Surso M.V. Radial Growth of Spruce (Picea abies (L.) Karst. × P. obovata Ledeb.) in the Conditions of Mining Impact. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 2, pp. 58–72. (In Russ.). https://doi.org/10.37482/0536-1036-2023-2-58-72

Plant-moth community relationships at the degraded urban peat-bog in Central Europe.

Peatlands have their own, specific insect fauna. They are a habitat not only for ubiquistic but also stenotopic moths that feed onplants limited to wet, acid and oligotrophic habitats. In the past, raised bogs and fens were widely distributed in Europe. This has changed since 20th c. Due to irrigation, modern forestry, and increasing human settlement, peatlands have become isolated islands in anagricultural and urban landscape. Here, we analyze the flora in a degraded bog situated in a large Lodz city agglomeration in Poland in relation to the diversity and composition of moth fauna. Over the last 40 years since the bog has become protected as a nature reserve, birch, willow, and alder shrubs replaced the typical raised bog plant communities due to the decreased water level. The analysis of moth communities sampled in 2012 and 2013 indicates dominance of ubiquistic taxa associated with deciduous wetland forests and rushes. Tyrphobiotic and tyrphophile moth taxa were not recorded. We conclude that the absence of moths typical of bog habitats and the dominance of common, woodland species are associated with hydrological changes, the expansion of trees and brushes over typical bog plant communities, and light pollution.

Ecological distribution of modern diatom in peatlands in the northern Greater Khingan Mountains and its environmental implications.

Relationships between diatom assemblages and environmental variables in peatlands of the northern Greater Khingan Mountains are helpful for understanding the indicative significance of diatoms to environment changes, and potentially provide a reference for environmental monitoring and paleoenvironment reconstruction in the edge of monsoon region. In this study, we analyzed modern diatom assemblages and their relationships with environment factors in 30 surface samples from shrubby-herbaceous and herbaceous peatlands based on ordination analysis. Benthic and epiphytic Pennatae diatoms are mainly ecological types, whereas planktonic Centricae diatoms are relatively fewer. The most diverse genera are Pinnularia and Eunotia. Eunotia paludosa and Achnanthidium minutissimum dominated in shrubby-herbaceous peatlands, while Navicula minima and Fragilaria capucina dominated in herbaceous peatlands. The diatom community structures are different in different vegetation types and the diatom species diversity in herbaceous peatlands is higher than that in shrubby-herbaceous peatlands. CODMn and pH are the most important environmental factors affecting diatom species composition and diversity. Eunotia bilunaris, Eunotia mucophila, and Eunotia paludosa can be used as indicators of acidic water environments. Caloneis silicula, Fragilaria capucina, Hantzschia amphioxys, and Navicula radiosa can be applied to indicate the weak alkaline conditions. Eunotia bilunaris and Eunotia paludosa can indicate low conductivity, while Sellaphora pupula indicates the medium-high conductivity. Fragilaria capucina and Navicula radiosa can indicate oligotrophic habitats.

Novel Ecosystems in the Urban-Industrial Landscape–Interesting Aspects of Environmental Knowledge Requiring Broadening: A Review

Human activity is affecting and transforming the natural environment, changing the ecosystem mosaic and natural biogeochemical processes in urban-industrial landscapes. Among the anthropogenic ecosystems, there are many present features of Novel Ecosystems (NE), e.g., the de novo created habitats on post-mineral excavation sites. The biological nature of the functional mechanisms of Novel Ecosystems is mostly unknown. In natural and semi-natural ecosystems, biodiversity is considered as the primary element influencing ecosystem processes and functioning. The preliminary studies conducted on post-mineral excavation sites have shown that, in poor oligotrophic habitats, the species composition of the assembled vascular plants is non-analogous, distinctive, and not found in natural and semi-natural habitats. This paper aims to present the gaps between scientific identification of the biological mechanisms driving ecosystem processes and functioning (including the expanding areas of Novel Ecosystems created de novo). Among the identified gaps, the following issues should be listed. The detailed identification and understanding of the processes and biodiversity-dependent functioning of Novel Ecosystems is crucial for proper environmental management, particularly when facing the challenges of ecological constraints and of global change. The ecology of Novel Ecosystems is a social and economic issue because of the relationships with densely populated urban-industrial areas.

Post-Extraction Novel Ecosystems Support Plant and Vegetation Diversity in Urban-Industrial Landscapes

Long-term exploitation of mineral resources has significantly changed the natural environment in urban-industrial landscapes. The changes on the surface of the extraction sites as a consequence of excavation of mineral resources provide specific mineral oligotrophic habitats on which plant species and thus vegetation can establish spontaneously. Some of these sites fulfill the prerequisites of novel ecosystems. This study was conducted on the spontaneous vegetation of post-extraction sites. Lists of species spontaneously covering these sites were prepared based on published data and our own records. This research revealed that species composition and vegetation types vary in time. These post-extraction novel ecosystems are also important for the presence of rare, endangered, and protected species noted in patches of different vegetation types. The variety of habitat conditions provided by these sites facilitates the occurrence of a wide spectrum of plants (both in terms of their socio-ecological origin and their ecological spectrum). This research proves how important these post-extraction novel ecosystems are for supporting plant and vegetation diversity in urban-industrial landscapes. Enhancing the biodiversity significantly increases the ecosystem services delivered by these sites and also the functioning of entire ecosystems. These natural processes on human habitats are essential in urban-industrial ecosystem landscape mosaics.

Reduced litterfall and decomposition alters nutrient cycling following conversion of tropical natural forests to rubber plantations

Natural tropical landscapes have been continuously altered by land use change and other climate factors. Forest management practices have transformed massive tropical forests into rubber plantations throughout mainland Southeast Asia and Southwest China. However, the effect of the forest-to-plantation conversion on ecosystem functions associated with plant litter is limited. Here, we compare litterfall production, decomposition, nutrient return and nutrient use efficiency between a tropical natural forest (TNF) and a monoculture rubber plantation (MRP) in Xishuangbanna (China) over three years. Annual mean litterfall production was significantly higher in TNF (10.92 Mg ha−1 yr−1) than in MRP (5.23 Mg ha−1 yr−1). Production of leaf litter was positively correlated to that of total litterfall, suggesting that leaf litter could be reliably estimated from total litterfall. Temperature and solar radiation are dominant drivers of seasonal variation of litterfall production. The litterfall production was more sensitive to climate variables in MRP. The average stand litter and the decomposition quotient were 1.8 and 1.2 times greater in TNF than in MRP, respectively. The total nutrient return to the forest floor was 2.1 times higher in TNF (5.66 Mg ha−1 yr−1) than in MRP (2.76 Mg ha−1 yr−1); the return of each mineral element was significantly lower in MRP relative to TNF. The nutrient return preferentially occurred during the cold and dry seasons, which was consistent with the trend of litterfall. Relatively high N, P, Ca, and Mg use efficiencies were observed in MRP in line with their deficiency in the present tropical soils, indicating that rubber trees likely possess an efficient nutrient uptake mechanism to facilitate their adaption to oligotrophic habitats. Our results suggest that the large scale transformation of tropical forests to rubber plantations could alter the biogeochemical cycles related to litterfall, and thus possibly affect the resilience of ecosystems to climate variation. An increasing organic matter input in rubber monoculture may favor the sustainable development of rubber cultivation.

The specialized white-sand flora of the Uatumã Sustainable Development Reserve, central Amazon, Brazil

The consensus is that Amazonian white-sand ecosystems (campinaranas) shelter several endemic plant species. However, recent studies have shown that most species are generalists, and they also occur in other Neotropical ecosystems. To investigate this issue, we analyzed the proportion of endemic/specialist species in a checklist of trees, palms, and shrubs sampled between 2014 and 2020 in campinarana patches of the Uatumã Sustainable Development Reserve (USDR), central Amazon. We also provide a description of phytophysiognomies, habitats, distribution, and phenology. We found 167 species belonging to 117 genera and 50 families. Fabaceae was the most representative (21 spp.), followed by Rubiaceae (16 spp.) and Chrysobalanaceae (10 spp.). We found that 30.5% of the species were exclusive to campinaranas, confirming that although there are many endemics, proportionally most species are generalists. The USDR has a rich flora specialized in oligotrophic habitats, which must be considered in the management and conservation strategies of these complex and fragile Amazonian ecosystems. 

Mallomonas voloshkoae sp. nov. (Synurales, Chrysophyceae) and distribution of M. pechlaneri in mountain lakes of Siberia

Mallomonas voloshkoae sp. nov. was described from Russia based on silica-scale morphology studied by means of transmission and scanning electron microscopy. This species belongs to the section Striatae and is characterised by scales with wide anterior flanges, forming wing-like extensions. This species is most similar in scale ultrastructure to M. pechlaneri. Mallomonas voloshkoae was reported in four mountain lakes of the Transbaikal area and was found in acidic to slightly acidic conditions with very low values of specific conductance. Mallomonas pechlaneri was reported in Russia for the first time. This is the first record of this species after the description of this taxon in Europe. Mallomonas pechlaneri was found in three oligotrophic habitats in the Altay and Sayan Mountain areas.

Bolstering fitness via CO2 fixation and organic carbon uptake: mixotrophs in modern groundwater

Current understanding of organic carbon inputs into ecosystems lacking photosynthetic primary production is predicated on data and inferences derived almost entirely from metagenomic analyses. The elevated abundances of putative chemolithoautotrophs in groundwaters suggest that dark CO2 fixation is an integral component of subsurface trophic webs. To understand the impact of autotrophically fixed carbon, the flux of CO2-derived carbon through various populations of subsurface microbiota must first be resolved, both quantitatively and temporally. Here we implement novel Stable Isotope Cluster Analysis to render a time-resolved and quantitative evaluation of 13CO2-derived carbon flow through a groundwater community in microcosms stimulated with reduced sulfur compounds. We demonstrate that mixotrophs, not strict autotrophs, were the most abundant active organisms in groundwater microcosms. Species of Hydrogenophaga, Polaromonas, Dechloromonas, and other metabolically versatile mixotrophs drove the production and remineralization of organic carbon. Their activity facilitated the replacement of 43% and 80% of total microbial carbon stores in the groundwater microcosms with 13C in just 21 and 70 days, respectively. The mixotrophs employed different strategies for satisfying their carbon requirements by balancing CO2 fixation and uptake of available organic compounds. These different strategies might provide fitness under nutrient-limited conditions, explaining the great abundances of mixotrophs in other oligotrophic habitats, such as the upper ocean and boreal lakes.

Responses of Seagrass Amphibolis antarctica Roots to Nutrient Additions Along a Salinity Gradient in Shark Bay, Western Australia

Seagrass meadows in oligotrophic environments are particularly susceptible to nutrient enrichment, yet morphological and architectural seagrass root responses in these ecosystems are poorly understood. This study aimed to investigate the response of Amphibolis antarctica, one of dominant seagrass species in Shark Bay, roots to nutrient additions along a salinity gradient in the oligotrophic ecosystem of Shark Bay, Western Australia. A fully factorial nutrient additional experiment with four treatments (Control, N, P and N+P) was conducted at each of five sites along a salinity gradient (between ~38ppt in site 1 and ~50ppt in site 5) in Shark Bay across a three-year period (2012-2015). In the laboratory, the roots morphology and architecture A. antarctica were investigated using a software (WinRhizo). Then, a two-way analysis of variance (ANOVA) was performed to investigate if there was a significant change in the morphology and architecture of the roots after the nutrient inputs and along five sites with salinity gradient. There was no significant impact of nutrient addition on the root’s morphology and architecture of A. antarctica species. However, the effect of site factor with salinity gradient was significant to all morphological aspects (total root length, root surface area and root diameter) of A. antarctica roots. These findings highlight the more ecological function of A. antarctica roots being in anchoring of the plant into the seafloor rather than to absorb nutrient from the sediment.Keywords: Nutrient addition, Oligotrophic habitats, Amphibolis antarctica, Shark Bay

Transformation of an Oligotrophic Sphagnum Bog during the Process of Rewetting

The vast peatlands of the European North of Russia were drained in the 20th century. Some of the drained areas were left without management and maintenance, which led to re-waterlogging. The current trend towards peatlands restoration requires an understanding of all the changes that have taken place in such ecosystems. The study aims to assess the changes in vegetation cover relative to changes in peat deposits in the rewetted oligotrophic bogs. The objects of research were located on the south-White Sea oligotrophic bogs. The studies were carried out using generally accepted geobotanical and geoecological methods in conjunction with the authors’ method for studying the group chemical composition of peat organic matter. The species diversity, structure and spatial distribution of the vegetation cover, the structure and composition of the peat, as well as the composition of the peat organic matter have been studied. It was shown that the transformation of an oligotrophic bog during the process of rewetting manifests itself in a significant change in the vegetation species diversity, somewhat reversible concerning ecologically tolerant species. Changes occurring in the peat deposit are irreversible. That limits the possibility of restoration of species of oligotrophic habitats to the initial state.

Plant and soil nitrogen in oligotrophic boreal forest habitats with varying moss depths: does exclusion of large grazers matter?

The boreal forest consists of drier sunlit and moister-shaded habitats with varying moss abundance. Mosses control vascular plant–soil interactions, yet they all can also be altered by grazers. We determined how 2 decades of reindeer (Rangifer tarandus) exclusion affect feather moss (Pleurozium schreberi) depth, and the accompanying soil N dynamics (total and dissolvable inorganic N, δ15N), plant foliar N, and stable isotopes (δ15N, δ13C) in two contrasting habitats of an oligotrophic Scots pine forest. The study species were pine seedling (Pinus sylvestris L.), bilberry (Vaccinium myrtillus L.), lingonberry (V. vitis-idaea L.), and feather moss. Moss carpet was deeper in shaded than sunlit habitats and increased with grazer exclusion. Humus N content increased in the shade as did humus δ15N, which also increased due to exclusion in the sunlit habitats. Exclusion increased inorganic N concentration in the mineral soil. These soil responses were correlated with moss depth. Foliar chemistry varied due to habitat depending on species identity. Pine seedlings showed higher foliar N content and lower foliar δ15N in the shaded than in the sunlit habitats, while bilberry had both higher foliar N and δ15N in the shade. Thus, foliar δ15N values of co-existing species diverged in the shade indicating enhanced N partitioning. We conclude that despite strong grazing-induced shifts in mosses and subtler shifts in soil N, the N dynamics of vascular vegetation remain unchanged. These indicate that plant–soil interactions are resistant to shifts in grazing intensity, a pattern that appears to be common across boreal oligotrophic forests.

Influence of the chlorophyll-a gradient on the community structure of plankton microcrustaceans (Cladocera and Copepoda) in a Neotropical reservoir.

Fish farming in net cages is considered as an alternative to food production in response to elevated population growth, and zooplankton is an important resource to the development of this economic activity. We (i) compared microcrustacean composition in eutrophic and oligotrophic habitats under net tank influence, (ii) investigated changes in species distributions in these habitats, and (iii) indicated which chlorophyll-a concentrations presented thresholds that alter community structure. We expected different responses of species to changes in chlorophyll-a concentration due to net cage management, as chlorophyll-a represents an estimate of food availability. Microcrustacean samplings and chlorophyll-a estimation were made upstream, downstream and close to the net cages, during 120 days, in the Rosana Reservoir (Brazil). Species composition differed significantly (p<0.05) among habitats where in the eutrophic environment was found the largest number of species. However, only in the eutrophic habitats did frequency of occurrence and relative abundance of some species change with chlorophyll-a variation. Thus, net cage management influenced species distribution only in the most productive habitat. These responses can affect ecosystem processes related to trophic dynamics as secondary productivity and nutrient cycling.