Immense land-cover changes in Iceland over the last millennium have encompassed birch (Betula pubescencs) woodland depletion and extensive soil erosion; few studies have focused on spatial ...distribution change of birch woodland in Iceland over centuries. The main objectives of this study were to (1) map the changes of birch woodland cover in THORNjorsardalur (14,000 ha) in southern Iceland, over a period of 350 years from late sixteenth to early twentieth century, and (2) explain the impact of socio-economic and natural forces on the woodland cover over three periods: 1587-1708, 1708-1880 and 1880-1938. We used a combined approach of historical reconstruction from diverse written archives, GIS-techniques and field work. About half of the THORNjorsardalur valley was covered by birch woodland in the late sixteenth century but over a period of 350 years 94 % of woodland had been depleted. The woodland was intensively used for firewood and charcoal making during the period with limited land management restriction. The main driving force for this development was socio-economic, where the form of ownership was a fundamental factor for the fate of the woodland. Harsh climate and volcanism further exacerbated the woodland during times when it had become fragmented and beyond its state of recovery.
The immigration of woody plants, especially Betula (tree birch), is examined in relation to geomorphological regions in a compilation of Late-glacial plant macrofossil records from Denmark. The ...immigration of trees led to a large ecological transformation of the landscape and had a major effect on the flora and fauna available to Palaeolithic people. We show that soil type was a controlling factor in the development of vegetation during the Alleroed and Younger Dryas periods. Following the first immigration of trees during the Alleroed period, woods became established in the eastern part of Denmark, where ice advances from the Baltic had deposited calcareous and clayey sediments. The western and northern parts of Denmark that are characterised by more sandy and non-calcareous sediments remained treeless throughout the whole Late-glacial period. Finds from the Bromme Culture are concentrated in the region which was wooded, suggesting that the regional variable environment allowed local adaptations using the diverse resources available.
Plant architecture, which is mostly determined by shoot branching, plays an important role in plant growth and development. Thus, it is essential to explore the regulatory molecular mechanism of ...branching patterns based on the economic and ecological importance. In our previous work, a multiple-branches birch mutant br was identified from 19 CINNAMOYL-COENZYME A REDUCTASE 1 (CCR1)-overexpressed transgenic lines, and the expression patterns of differentially expressed genes in br were analyzed. In this study, we further explored some other characteristics of br, including plant architecture, wood properties, photosynthetic characteristics, and IAA and Zeatin contents. Meanwhile, the T-DNA insertion sites caused by the insertion of exogenous BpCCR1 in br were identified to explain the causes of the mutation phenotypes.
The mutant br exhibited slower growth, more abundant and weaker branches, and lower wood basic density and lignin content than BpCCR1 transgenic line (OE2) and wild type (WT). Compared to WT and OE2, br had high stomatal conductance (Gs), transpiration rate (Tr), but a low non-photochemical quenching coefficient (NPQ) and chlorophyll content. In addition, br displayed an equal IAA and Zeatin content ratio of main branches' apical buds to lateral branches' apical buds and high ratio of Zeatin to IAA content. Two T-DNA insertion sites caused by the insertion of exogenous BpCCR1 in br genome were found. On one site, chromosome 2 (Chr2), no known gene was detected on the flanking sequence. The other site was on Chr5, with an insertion of 388 bp T-DNA sequence, resulting in deletion of 107 bp 5' untranslated region (UTR) and 264 bp coding sequence (CDS) on CORONATINE INSENSITIVE 1 (BpCOII). In comparison with OE2 and WT, BpCOI1 was down-regulated in br, and the sensitivity of br to Methyl Jasmonate (MeJA) was abnormal.
Plant architecture, wood properties, photosynthetic characteristics, and IAA and Zeatin contents in main and lateral branches' apical buds changed in br over the study's time period. One T-DNA insertion was identified on the first exon of BpCOI1, which resulted in the reduction of BpCOI1 expression and abnormal perception to MeJA in br. These mutation phenotypes might be associated with a partial loss of BpCOI1 in birch.
The effects of asynchrony in the phenology of spring-feeding insect-defoliators and their host plants on insects' fitness, as well as the importance of this effect for the population dynamics of ...outbreaking species of insects, is a widespread and well-documented phenomenon. However, the spreading of this phenomenon through the food chain, and especially those mechanisms operating this spreading, are still unclear. In this paper, we study the effect of seasonally declined leafquality (estimated in terms of phenolics and nitrogen content) on herbivore fitness, immune parameters and resistance against pathogen by using the silver birch Betula pendula-gypsy moth Lymantria dispar-nucleopolyhedrovirus as the tritrophic system. We show that a phenological mismatch induced by the delay in the emergence of gypsy moth larvae and following feeding on mature leaves has negative effects on the female pupal weight, on the rate of larval development and on the activity of phenoloxidase in the plasma of haemolymph. In addition, the larval susceptibility to exogenous nucleopolyhydrovirus infection as well as covert virus activation were both enhanced due to the phenological mismatch. The observed effects of phenological mismatch on insect-baculovirus interaction may partially explain the strong and fast fluctuations in the population dynamics of the gypsy moth that is often observed in the studied part of the defoliator area. This study also reveals some indirect mechanisms of effect related to host plant quality, which operate through the insect innate immune status and affect resistance to both exogenous and endogenous virus.
Betula alnoides has been widely used in local traditional medicinal treatment for a variety of diseases, wounds and to cure diabetes. The air-dried, powdered (200 g) bark was extracted with 80% ...methanol at room temperature. The combined 80% methanolic extract was partitioned with organic solvents to yield n-hexane, ethyl acetate (EtOAc), n-butanol (BuOH; water saturated), and aqueous fractions for the investigation of antioxidant and antimicrobiology and alpha -glucosidase activity effects (GAE) of B. alnoides. Antioxidant activity was studied by using antioxidant tests, including electron donation ability test, reducing power, and metal-chelating activity assay. Antioxidant, antimicrobial activity and alpha -glucosidase inhibitory effect of 80% methanolic extracts and fractions derived from the bark of B. alnoides were evaluated and determined. The results showed that 80% methanolic extracts exhibited high 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity (80.68%). In addition, both the 80% methanolic extract and EtOAc fraction exhibited more potent reducing activity than did butylated hydroxyanisole (BHA) and trolox. The aqueous fraction had higher metal-chelating activity than other fractions. The EtOAc fraction had the highest phenolic and flavonoid content (217.73 + or - 1.02 mg GAE/g extract, and 38.42 + or - 1.87 mg QE/g extract, respectively). The 80% methanolic extract and EtOAc fraction showed higher levels of antimicrobial activity than did other fractions. The 80% methanolic extract had the most powerful alpha -glucosidase inhibitory effect (98.46%) at a concentration of 40 mu g/mL. The results suggest that bark extracts of B. alnoides could be a potential source of natural antioxidants and for treating pathogenic diseases.
Bronze birch borer (Agrilus anxius Gory) is the key pest of birches (Betula spp.) in North America, several of which have been recommended for ornamental landscapes based on anecdotal reports of ...borer resistance that had not been confirmed experimentally. In a 20-yr common garden experiment initiated in 1979 in Ohio, North American birch species, including paper birch (Betula papyrifera Marshall), ‘Whitespire’ gray birch (Betula populifolia Marshall), and river birch (Betula nigra L.), were much more resistant to bronze birch borer than species indigenous to Europe and Asia, including European white birch (Betula pendula Roth), downy birch (Betula pubescens Ehrh.), monarch birch (Betula maximowicziana Regel), and Szechuan white birch (Betula szechuanica Jansson). Within 8 yr of planting, every European white, downy, and Szechuan birch had been colonized and killed, although 100% of monarch birch had been colonized and 88% of these plants were killed after nine years. Conversely, 97% of river birch, 76% of paper birch, and 73% Whitespire gray birch were alive 20 yr after planting, and river birch showed no evidence of colonization. This pattern is consistent with biogeographic theory of plant defense: North American birch species that share a coevolutionary history with bronze birch borer were much more resistant than naïve hosts endemic to Europe and Asia, possibly by virtue of evolution of targeted defenses. This information suggests that if bronze birch borer were introduced to Europe or Asia, it could threaten its hosts there on a continental scale. This study also exposed limitations of anecdotal observation as evidence of host plant resistance.
The aim of this study was to investigate the potential of indigenous arsenic-tolerant bacteria to enhance arsenic phytoremediation by the autochthonous pseudometallophyte
The first goal was to ...perform an initial analysis of the entire rhizosphere and endophytic bacterial communities of the above-named accumulator plant, including the cultivable bacterial species.
's microbiome was dominated by taxa related to
,
, and
, especially the
and
genera. A total of 54 cultivable rhizobacteria and 41 root endophytes, mainly affiliated with the phyla
,
,
, and
, were isolated and characterized with respect to several potentially useful features for metal plant accumulation, such as the ability to promote plant growth, metal chelation, and/or mitigation of heavy-metal stress. Seven bacterial isolates were further selected and tested for
accumulation of arsenic in plants; four of them were finally assayed in field-scale bioaugmentation experiments. The exposure to arsenic
caused an increase in the total nonprotein thiol compound content in roots, suggesting a detoxification mechanism through phytochelatin complexation. In the contaminated field, the siderophore and indole-3-acetic acid producers of the endophytic bacterial consortium enhanced arsenic accumulation in the leaves and roots of
, whereas the rhizosphere isolate
strain 91R mainly promoted plant growth. Field experimentation showed that additional factors, such as soil arsenic content and pH, influenced arsenic uptake in the plant, attesting to the relevance of field conditions in the success of phytoextraction strategies.
Microorganisms and plants have developed several ways of dealing with arsenic, allowing them to resist and metabolize this metalloid. These properties form the basis of phytoremediation treatments and the understanding that the interactions of plants with soil bacteria are crucial for the optimization of arsenic uptake. To address this in our work, we initially performed a microbiome analysis of the autochthonous
plants growing in arsenic-contaminated soils, including endosphere and rhizosphere bacterial communities. We then proceeded to isolate and characterize the cultivable bacteria that were potentially better suited to enhance phytoextraction efficiency. Eventually, we went to the field application stage. Our results corroborated the idea that recovery of pseudometallophyte-associated bacteria adapted to a large historically contaminated site and their use in bioaugmentation technologies are affordable experimental approaches and potentially very useful for implementing effective phytoremediation strategies with plants and their indigenous bacteria.
New sequencing technologies allow development of genome‐wide markers for any genus of ecological interest, including plant genera such as Betula (birch) that have previously proved difficult to study ...due to widespread polyploidy and hybridization. We present a de novo reference genome sequence assembly, from 66× short read coverage, of Betula nana (dwarf birch) – a diploid that is the keystone woody species of subarctic scrub communities but of conservation concern in Britain. We also present 100 bp PstI RAD markers for B. nana and closely related Betula tree species. Assembly of RAD markers in 15 individuals by alignment to the reference B. nana genome yielded 44–86k RAD loci per individual, whereas de novo RAD assembly yielded 64–121k loci per individual. Of the loci assembled by the de novo method, 3k homologous loci were found in all 15 individuals studied, and 35k in 10 or more individuals. Matching of RAD loci to RAD locus catalogues from the B. nana individual used for the reference genome showed similar numbers of matches from both methods of RAD locus assembly but indicated that the de novo RAD assembly method may overassemble some paralogous loci. In 12 individuals hetero‐specific to B. nana 37–47k RAD loci matched a catalogue of RAD loci from the B. nana individual used for the reference genome, whereas 44–60k RAD loci aligned to the B. nana reference genome itself. We present a preliminary study of allele sharing among species, demonstrating the utility of the data for introgression studies and for the identification of species‐specific alleles.
Expansion of deciduous shrubs is a common observation throughout the Arctic, with implications for carbon (C) cycling. Shrubs may increase net ecosystem C uptake through greater leaf area and gross ...ecosystem photosynthesis (GEP), and/or through cooler summer soils and reduced ecosystem respiration (ER). We used a space-for-time substitution combined with experimental warming at a Low Arctic site in West Greenland to examine the biophysical effects of increased temperature and Betula nana abundance on ecosystem CO sub(2) exchange. Communities dominated by Betula were much stronger C sinks than graminoid communities due to greater GEP and lower ER. The warming treatment had little effect on GEP, ER, or net ecosystem CO sub(2) exchange (NEE). The start of the growing season has been advancing at our study site, as indicated by long-term observations of plant phenology. In a retrospective analysis, we estimate that earlier onset of the growing season has increased the strength of the ecosystem C sink at rates of 1.3 and 2.1 g C m super(-2) y super(-1) in Betula and graminoid tundra, respectively, since 2002. However, earlier, and presumably longer, growing seasons may be associated with greater potential for drought stress. Our data suggest that mid-summer drought-induced GEP declines may partially offset C gains associated with an earlier start to the growing season. Our results suggest greater deciduous shrub abundance and longer growing seasons will likely lead to greater net C uptake in our study area, while highlighting important complexities associated with drought and plant community composition.
Climate warming at high northern latitudes has caused substantial increases in plant productivity of tundra vegetation and an expansion of the range of deciduous shrub species. However significant ...the increase in carbon (C) contained within above‐ground shrub biomass, it is modest in comparison with the amount of C stored in the soil in tundra ecosystems. Here, we use a ‘space‐for‐time’ approach to test the hypothesis that a shift from lower‐productivity tundra heath to higher‐productivity deciduous shrub vegetation in the sub‐Arctic may lead to a loss of soil C that out‐weighs the increase in above‐ground shrub biomass. We further hypothesize that a shift from ericoid to ectomycorrhizal systems coincident with this vegetation change provides a mechanism for the loss of soil C. We sampled soil C stocks, soil surface CO₂flux rates and fungal growth rates along replicated natural transitions from birch forest (Betula pubescens), through deciduous shrub tundra (Betula nana) to tundra heaths (Empetrum nigrum) near Abisko, Swedish Lapland. We demonstrate that organic horizon soil organic C (SOCₒᵣg) is significantly lower at shrub (2.98 ± 0.48 kg m⁻²) and forest (2.04 ± 0.25 kg m⁻²) plots than at heath plots (7.03 ± 0.79 kg m⁻²). Shrub vegetation had the highest respiration rates, suggesting that despite higher rates of C assimilation, C turnover was also very high and less C is sequestered in the ecosystem. Growth rates of fungal hyphae increased across the transition from heath to shrub, suggesting that the action of ectomycorrhizal symbionts in the scavenging of organically bound nutrients is an important pathway by which soil C is made available to microbial degradation. The expansion of deciduous shrubs onto potentially vulnerable arctic soils with large stores of C could therefore represent a significant positive feedback to the climate system.
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