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PubMed2002

Mapping epigenetic quantitative trait loci (QTL) altering a developmental trajectory.

Genetic variation in a quantitative trait that changes with age is important to both evolutionary biologists and breeders. A traditional analysis of the dynamics of genetic variation is based on the genetic variance-covariance matrix among different ages estimated from a quantitative genetic model. Such an analysis, however, cannot reveal the mechanistic basis of the genetic variation for a growth trait during ontogeny. Age-specific genetic variance at time t conditional on the causal genetic effect at time t - 1 implies the generation of episodes of new genetic variation arising during the interval t - 1 to t. In the present paper, the conditional genetic variance estimated from Zhu's (1995) conditional model was partitioned into its underlying individual quantitative trait loci (QTL) using molecular markers in an F2 progeny of poplars (Populus trichocarpa and Populus deltoides). These QTL, defined as epigenetic QTL, govern the alterations of growth trajectory in a population. Three epigenetic QTL were detected to contribute significantly to variation in growth trajectory during the period from the establishment year to the subsequent year in the field. It is suggested that the activation and expression of epigenetic QTL are influenced by the developmental status of trees and the environment in which they are grown.

Analysis of Variance↗

PubMedDate not supplied

[Sensitization to Castanea sativa pollen and pollinosis in northern Extremadura (Spain)].

BACKGROUND: Castanea sativa pollen allergy has generally been considered to be uncommon and clinically insignificant. In our geographical area (Plasencia, Cáceres, Spain) Castanea sativa pollen is a major pollen. OBJECTIVE: To determine the atmospheric fluctuations and prevalence of patients sensitized to Castanea pollen in our region and to compare this sensitization with sensitizations to other pollens. METHODS: Patients with respiratory symptoms attending our outpatient clinic for the first time in 2003 were studied. The patients underwent skin prick tests with commercial extracts of a battery of inhalants including Castanea sativa pollen. Serologic specific IgE to Castanea sativa pollen was determined using the CAP system (Pharmacia and Upjohn, Uppsala, Sweden). Airborne pollen counts in our city were obtained using Cour collection apparatus over a 4-year period (2000 to 2003). RESULTS: The most predominant pollens detected were (mean of the maximal weekly concentrations over 4 years in pollen grains/m3): Quercus 968, Poacea 660, Olea 325, Platanus 229, Pinus 126, Cupresaceae 117, Plantago 109, Alnus 41, Populus 40, Castanea 32. We studied 346 patients (mean age: 24.1 years). In 210 patients with a diagnosis of pollinosis, the percentages of sensitization were: Dactylis glomerata 80.4%, Olea europea 71.9%, Fraxinus excelsior 68%, Plantago lanceolata 62.8%, Chenopodium album 60.9%, Robinia pseudoacacia 49%, Artemisia vulgaris 43.8%, Platanus acerifolia 36.6%, Parietaria judaica 36.1%, Populus nigra 32.3%, Betula alba 27.6%, Quercus ilex 21.4%, Alnus glutinosa 20.9%, Cupressus arizonica 7.6% and Castanea sativa 7.1%. Fifteen patients were sensitized to Castanea sativa and 14 had seasonal rhinoconjunctivitis and asthma. Ten patients had serum specific IgE to Castanea pollen (maximum value: 17.4 Ku/l). Castanea pollen is present in our area in large amounts from the 23rd to the 28th weeks of the year, with a peak pollen count in the 25th week. CONCLUSIONS: The most important allergenic pollens in northern Extremadura were Poaceae, Olea europaea and Plantago sp. The prevalence of sensitization to Castanea sativa pollen was very low (7.1%). Most sensitized patients had asthma and polysensitization. Castanea sativa pollen is not a major cause of pollinosis in our area.

Adolescent↗

PubMed1980

Characteristics of pollen diffusates and pollen wall cytochemistry in poplars.

Pollen diffusates, known to be important in pollen-stigma interactions controlling interspecific incompatibility between Populus deltoides and Populus alba, have been partly characterized and shown to contain more than 20 protein bands by polyacrylamide gel electrophoresis, at least 4 of these being glycoproteins. Seven fractions had antigenic activity in rabbits and several enzyme activities were also present. Peroxidase and leucine aminopeptidase isoenzymes were detected in the diffusates, demonstrating the extracellular location of these 2 enzymes. Isoenzyme patterns of peroxidase, esterase and acid phosphatase were complex, with some bands common to both species. Localization of acid phosphatase in the intine and esterase in the exine was demonstrated after brief aldehyde fixation and low-temperature embedding in glycol methacrylate. The intine and exine sites were distinguished by their chemical and structural features. Calcofluor white M2R new proved to be an excellent stain for differentiating the intine. Aniline blue-positive material, probably beta-1,3-glucan, is present associated with the intine of many ungerminated as well as germinating grains: production of this material may be a response to damage.

Antigens↗

PubMedDate not supplied

Inhibition by Salix- extracts and Phytodolor of copper-catalyzed oxidative destruction.

Oxidation of low density lipoprotein (LDL) by copper ions is strongly inhibited by different aqueous extracts (Salix spec (SE); Fraxinus-Dolidago-Populus (Phytodolor)(PD) in a concentration range between 4 and 7 micrograms/ml. 10 to 50 microM salicylic acid (SA) stimulate LDL-oxidation whereas higher concentrations (10 to 500 micromM) showed no effect. Likewise ethene release from 2-keto-4-methylthiobutyrate (KMB) is strongly inhibited by the above extracts in a reaction driven by dihydroxyfumarate (DHF) in the presence of copper ions. This system may represent some features of the diabetic situation where DHF as an endiole may stand for certain Amadori products. In order to find out whether the inhibitory effects are due to copper chelation we tested the copper-dependent conversion of photodynamic ethane release from alpha-linolenic acid into ethene formation. Copper chelation is apparently only partially involved in inhibition of copper-dependent oxidations and only at a certain concentration of extracts from salix spec (SE) or extracts from Fraxinus-Solidago-Populus (Phytodolor)(PD).

Antioxidants↗

PubMed2001

Cellulose in cyanobacteria. Origin of vascular plant cellulose synthase?

Although cellulose biosynthesis among the cyanobacteria has been suggested previously, we present the first conclusive evidence, to our knowledge, of the presence of cellulose in these organisms. Based on the results of x-ray diffraction, electron microscopy of microfibrils, and cellobiohydrolase I-gold labeling, we report the occurrence of cellulose biosynthesis in nine species representing three of the five sections of cyanobacteria. Sequence analysis of the genomes of four cyanobacteria revealed the presence of multiple amino acid sequences bearing the DDD35QXXRW motif conserved in all cellulose synthases. Pairwise alignments demonstrated that CesAs from plants were more similar to putative cellulose synthases from Anabaena sp. Pasteur Culture Collection 7120 and Nostoc punctiforme American Type Culture Collection 29133 than any other cellulose synthases in the database. Multiple alignments of putative cellulose synthases from Anabaena sp. Pasteur Culture Collection 7120 and N. punctiforme American Type Culture Collection 29133 with the cellulose synthases of other prokaryotes, Arabidopsis, Gossypium hirsutum, Populus alba x Populus tremula, corn (Zea mays), and Dictyostelium discoideum showed that cyanobacteria share an insertion between conserved regions U1 and U2 found previously only in eukaryotic sequences. Furthermore, phylogenetic analysis indicates that the cyanobacterial cellulose synthases share a common branch with CesAs of vascular plants in a manner similar to the relationship observed with cyanobacterial and chloroplast 16s rRNAs, implying endosymbiotic transfer of CesA from cyanobacteria to plants and an ancient origin for cellulose synthase in eukaryotes.

Amino Acid Sequence↗

PubMed2001

Nutrient and heavy metal uptake and storage in constructed wetland systems in Arizona.

The Constructed Ecosystems Research Facility (CERF) was conceived in the early 1980s as a test facility to explore the potential for using plants to treat wastewater in the arid west of the USA. One of the major issues that has been identified in the use of constructed wetland technology is plant nutrient uptake and tissue storage of nutrients as well as heavy metals. Our approach to understanding plant uptake and storage has been to look at both controlled conditions in constructed systems and background concentrations in natural systems. Plant tissues have been collected and analyzed from natural systems and from controlled systems receiving either wastewater or municipal water. Plants studied included the herbaceous species Anemopsis californica (Yerba mansa), Scirpus spp. (bulrush) and Typha domingensis (cattail), and tree species Fraxinus velutina (ash), Populus fremontii (cottonwood) and Salix spp. (willow). Data indicate that uptake varies not only among plant species, but also among chemical species, depending upon water quality within the wetlands. Leaf tissues of Fraxinus, Salix and Populus, contained the lowest amounts of nutrients and heavy metals studied (Na, P, K, Cu, Pb and Zn), while the root tissues of the herbaceous plants generally had the highest concentrations.

Ecosystem↗

PubMedDate not supplied

Comparative analysis of phenolic acids in mistletoe plants from various hosts.

Phenolic acids present in mistletoe plants collected from various hosts were analysed with the use of HPLC. The following numbers of compounds were found in the mistletoe plant material gathered from respective hosts: Sorbus aucuparia- 12 compounds; Acer plantanoides--14 compounds: Malus domestica, Pyrus communis and Populus nigra--13 compounds each; Quercus robur--15 compounds. Altogether 21 phenolic acids were chromatographically identified in the tested material. The compounds were either free or combined as esters or glycosides. Comparative chromatography revealed qualitative differences in the investigated compounds between the various plant materials. For example o-coumaric acid was only found in mistletoe hosted by Quercus robur. Digallic acid was only found in the plant material hosted by Acer plantanoides. Qualitative and quantitative composition of mistletoes hosted by Malus domestica and Pyrus communis showed considerable similarities as far as phenolic acids were concerned. Moreover. vanillic acid. absent in all other batches of plant material, seemed to be characteristic of the above mistletoes. Quantitative HPLC analysis demonstrated a considerable content of salicylic acid (39.55 mg%) in mistletoe hosted by Sorbus aucuparia. Apart from the above material, this compound was only present in small quantities in plants hosted by Populus nigra (15.63 mg%) and Quercus robur (2.63 mg%).

Chromatography, High Pressure Liquid↗

PubMed2003

[Phosphorus transfer between mixed poplar and black locust seedlings].

In this paper, the 32P radio-tracer technique was applied to study the ways of phosphorus transfer between poplar (Populus euramericana cv. 'I-214') and black locust (Robinia pseudoacacia). A five compartment root box (18 cm x 18 cm x 26 cm) was used for testing the existence of the hyphal links between the roots of two tree species when inoculated with vesicular-arbuscular (VA) mycorrhizal fungus (Glomus mosseae). Populus I-214 (donor) and Robinia pseudoacacia (receiver) were grown in two terminal compartments, separated by a 2 cm root-free soil layer. The root compartments were lined with bags of nylon mesh (38 microns) that allowed the passage of hyphae but not roots. The top soil of a mixed stand of poplar and black locust, autoclaved at 121 degrees C for one hour, was used for growing seedlings for testing. In 5 compartment root box, mycorrhizal root colonization of poplar was 34%, in which VA mycorrhizal fungus was inoculated, whereas 26% mycorrhizal root colonization was observed in black locust, the other terminal compartment, 20 weeks after planting. No root colonization was observed in non-inoculated plant pairs. This indicated that the mycorrhizal root colonization of black locust was caused by hyphal spreading from the poplar. Test of tracer isotope of 32P showed that the radioactivity of the treatment significantly higher than that of the control (P < 0.05), 14 days from the tracer applied, to 27 days after, when VA mycorrhizal fungus was inoculated in poplar root. Furthermore, mycorrhizal interconnections between the roots of poplar and black locust seedlings was observed in situ by binocular in root box. All these experiments showed that the hyphal links was formed between the roots of two species of trees inoculated by VA mycorrhizal fungus. Four treatments were designed according to if there were two nets (mesh 38 microns), 2 cm apart, between the poplar and black locust, and if the soil in root box was pasteurized. Most significant differences of radioactivity among four treatments appeared 44 days after feeding 32P, the radioactivity of the day was applied to estimating the contribution of the various possible transfer ways to the total amount of nutrient transfer. Level of 32P radioactivity was found to be significantly (P < 0.05) higher in leaves of the treatment of "no separated and soil non-pasteurized" (17.1 pulse.g-1.s-1) than in leaves of "net separated and soil non-pasteurized" (5.3 pulse.g-1.s-1), and also significantly higher in leaves of "no net separated and soil pasteurized" (11.5 pulse.g.s-1) than in leaves of "net separated and soil pasteurized" (2.3 pulse.g-1.s-1), and very significantly (P < 0.01) higher in leaves of "no net separated and soil non-pasteurized" than in leaves of "net separated and soil pasteurized", whereas the levels of 32P radioactivity were not significantly different between the other treatments. The results showed that root contact and root exudations were the main ways of phosphorus transfer between the two species and the amount of phosphorus transfer through these two ways accounted for 62% of the total. The activity of the microorganisms including VA mycorrhizal fungi and the interaction between the microorganisms and root contact and root exudations made up 38% of total amount of phosphorus. The effect of mycorrhizal hyphal links in the direct nutrient transfer between poplar and black locust through separate mesh (38 microns) was little.

Biological Transport↗

PubMed2003

[Spatial and temporal characteristics of soil moisture dynamics in Loess Plateau].

Field monitoring results of wasteland soil water content of during growing season of seven years in Zhuanyaogou valley of northwestern Shanxi Province, and the results showed that the seasonal dynamics of the soil water was controlled by annual precipitation and its distribution. The seasonal dynamics of soil water in a normal rainfall year could be divided into three stages, i.e., consumption stage from late spring to early summer, storage stage from late summer to early autumn, and second consumption stage from late autumn to early winter. The relationship equation between soil water content and measuring number was linear (1988, 1990), exponent (1992, 1995) and parabola curve (1993). The vertical profiles of soil water in the wasteland in different rainfall year were different, and the soil water content increased with increasing depth. The equations between soil water content and soil depth in all years were cubic. Taking 150 cm as a boundary, the ratio of soil water content in lower layers to upper layers was larger than 1, and the variance coefficient of soil water decreased with increasing depth. The soil water profile in 0-300 cm depth for seven year's average could be divided into three layers, i.e., active layer (above 200 cm), transitive layer (between 200-250 cm) and stable layer (below 250 cm), and the depth of each layer varied with the annual precipitation and its distribution. The ANOVA result of soil water content in extremely high rainfall showed a great difference with that in other years. The difference between soil water content in wasteland and in Caragana korshinskii plantation was significant, but was not different from that in Populus hopeiensis and Populus simonii plantation respectively. The quantitative analysis methods used in this paper facilitated the comparison of soil moisture in different region and in different vegetation.

Ecosystem↗

PubMed2003

[Quantitative analysis on sharp-tooth oak stands in Qinling Mountains].

The arbor stratum of Quercus aliena var. acuteserrata stands included two substratums. Phanerophyta synusium was in first position, and hemicryptophyta was inferior to it. The DBH structures of Quercus aliena var. acuteserrata and Pinus armandii were sinister normal school, which could finish self-regeneration under the natural conditions. The small DBH class individuals of Pinus tabulaeformis were dominant, their DBH classes being distributed irregularly and absent very much. The large DBH classes of Toxicodendron vernicifluum took biggish proportion, belonging to declining population. Young trees were the principal individuals of Castanea mollissima, and in transitional age stage from the young to the middle. Populus davidiana was in the transitional stage from progressive to stable and young-middle age stands. The stands DBH structure was mainly influenced by the DBH variety of Quercus aliena var. acuteserrata population. Quantitative classification (ward's method ward) and ordination (PCA) were used to study the community types of sharp-tooth oak. The results showed that the community could be divided into 6 types: 1. Ass. Smilax stans + Rosa multiflora-Quercus variabilis + Ulmus glaucescens-Quercus aliena var. acuteserrata; 2. Ass. Smilax stans + Lespedeza bicolor-Castanea mollissima-Q. aliena var. acuteserrata; 3. Ass. Corylus mandshurica-Populus davidiana + Dendrobenthamia angustata-Q. aliena var. acuteserrata; 4. Ass. Prunus pseudoccrasus + Corylus mandshurica-Toxicodendron vernicifluum-Q. aliena var. acuteserrata; 5. Ass. Corylus mandshurica + Rosa multiflora-Pinus armandii-Q. aliena var. acuteserrata; and 6. Ass. Sinarundinaria nitida-Pinus armandii + Pinus tabulaeformis-Q. aliena var. acuteserrata. Ward's method ward was better for classifying community types than the other clustering analyses in Qinling Mountains. The PCA results were consistent with the clustering, and demonstrated that the sharp-tooth oak stands were influenced by the altitude, site gradient and soil mainly.

China↗

PubMed2004

Airborne pollen calendar of Lublin, Poland.

Pollen concentration in the atmosphere of Lublin (eastern Poland) was studied by means of volumetric method using Hirst sampler (VPPS 2000, Lanzoni) in 2001-2002. The pollen trap was mounted at the height of 15 m in the centre of Lublin. On the basis of analysis of mean daily values of pollen concentration, the pollen calendar was constructed for 16 taxa producing the allergenic pollen: Alnus, Corylus, Populus, Ulmus, Fraxinus, Betula, Carpinus, Quercus, Fagus, Pinaceae, Poaceae, Rumex, Plantago, Chenopodiaceae, Artemisia, Urticaceae. Great differences referring to the course of pollen seasons for most of the studied taxa of trees within the 2 years of study were found. They were associated with the beginning and end of the pollen season, the amount and the date of maximum pollen concentration occurrence, as well as annual sums of pollen grains. Much lower differentiation was observed in the case of herbaceous plants. This referred mainly to maximum concentration occurrence dates (Urtica, Poaceae) and the length of pollen season (Chenopodiaceae). The most similar course of pollen seasons during 2 years was recorded for Artemisia. Among trees, the highest pollen concentrations were recorded for Betula, Pinaceae and Alnus; the lowest for Ulmus, Fagus and Corylus. Very high concentration of herbaceous plant's pollen was observed for Poaceae and Urtica; Plantago and Chenopodiaceae showed the lowest level. Annual sums of pollen grains for Alnus, Populus, Quercus, Betula and Pinaceae were much higher in 2001, but in the case of Ulmus, Fraxinus, Carpinus, Fagus the annual sums of pollen grains in 2002 were almost twice as high as in 2001. For 5 among 7 herbaceous taxa, annual sums of pollen grains in both years were similar.

Air Pollutants↗

PubMed2003

[Research progress in forest tree genetic linkage map construction and its future prospects].

The research progress in genetic linkage map construction of forest tree species both at home and abroad were reviewed in the paper. Two main problems involved in the field were discussed. One was the limitation of the number of individuals of mapping populations and the other was the random markers mostly employed by the majority of studies. These problems have resulted in crossing combination specificity in the constructed maps and the QTLs located on the basis of the maps. As a result,the QTLs discovered up to now have low credibility and poor practicability in marker-assisted selection. Therefore considering the biological characteristics of forest tree species,the selection of the most suitable genetic markers is crucial to obtain a high quality genetic linkage map, and it is both important and necessary to carry out comparative genetic mapping. Progress in the ongoing expressed sequence tag (EST) sequencing projects were summarized and EST polymorphism (ESTP), the most informative and highly conservative marker with known function,as well as the main ESTP detection techniques were elaborated. It was pointed out that ESTP markers should be integrated into the present studies of genetic linkage map construction, QTL mapping and genome comparative mapping. Finally the future prospects in the fields of genetic linkage map and QTL mapping were discussed. In China, such studies around Populus, especially in the local Populus species should make a breakthrough in the related fields.

English Abstract↗

PubMed2006

Aspen SP1, an exceptional thermal, protease and detergent-resistant self-assembled nano-particle.

Stable protein 1 (SP1) is a homo-oligomeric protein isolated from aspen (Populus tremula aspen) plants which forms a ring-shape dodecameric particle with a central cavity. The oligomeric form of SP1 is an exceptionally stable structure that is resistant to proteases (e.g., trypsin, V8, and proteinase K), high temperatures, organic solvents, and high levels of ionic detergent. Analytical ultra-centrifugation, chemical cross-linking, matrix-assisted laser-desorption time-of-flight mass spectrometry (MALDI-TOF-MS), and transmission electron microscopy were used to further characterize the SP1 dodecamer. Introduction of a single cysteine at the N-terminus of SP1 enabled the formation of disulfide bridges within the SP1 dodecamer, concurrent with increased melting point. A six-histidine tag was introduced at the N-terminus of SP1 to generate 6HSP1, and the DeltaNSP1 mutant was generated by a deletion of amino acids 2-6 at the N-terminus. Both 6HSP1 and DeltaNSP1 maintained their ability to assemble a stable dodecamer. Remarkably, these SP1 homo-dodecamers were able to re-assemble into stable hetero-dodecamers following co-electro-elution from SDS-PAGE. The exceptional stability of the SP1-nano ring and its ability to self-assemble hetero-complexes paves the way to further research in utilizing this unique protein in nano-biotechnology.

Crystallization↗

PubMed2004

Dendroremediation of trinitrotoluene (TNT). Part 1: Literature overview and research concept.

BACKGROUND, AIM AND SCOPE: For decades, very large areas of former military sites have been contaminated diffusely with the persistent nitroaromatic explosive 2,4,6-trinitrotoluene (TNT). The recalcitrance of the environmental hazard TNT is to a great extent due to its particulate soil existence, which leads to slow but continuous leaching processes. Although improper handling during the manufacture of TNT seems to be a problem of the past in developed countries, environmental deposition of TNT and other explosives is still going on unfortunately, resulting from thousands of unexploded ordnance or low order explosions at munitions test areas and at current battlefields. OBJECTIVE: Sustainable phytoremediation strategies for explosives in Germany, which intend to use trees to decontaminate soil and groundwater ('dendroremediation'), have to consider that most of the former German military sites are already covered with woodlands, mainly with conifer stands. Therefore, parallel investigation of the remediation potential is necessary for both of the selected hybrids of fast growing broadleaf trees, which are waiting for planting and forest conifers, which have already proven for decades that they are able to grow on explosive contaminated sites. MAIN FEATURES: A short literature review is given regarding phytoremediation of TNT with herbaceous plants and some general aspects of dendroremediation are discussed. Furthermore, an overview of our TNT-dendroremediation research network is introduced, which has the strategic goal to make dendroremediation more calculable for a series of potent trees for site-adapted in situ application and for the assessment of tree remediation potentials in natural attenuation processes. RESULTS AND DISCUSSION: Some of our methods, results and conclusions yet unpublished are presented. For a preliminary calculation of area-related annual TNT dendroremediation potential of five-year-old trees, the following values were assessed: Salix EW-13 6.0, Salix EW-20 8.5, Populus ZP-007 4.2, Betula pendula 5.2, Picea abies 1.9 and Pinus sylvestris 0.8 g m(-2) a(-1). For a 45-year-old spruce forest, an annual natural attenuation potential of 4.2 g TNT m(-2) a(-1) was found. CONCLUSION, RECOMMENDATIONS AND PERSPECTIVE: Our main results deliver quantitative proposals for dendroremediation strategies in situ and provide decision aids. Also aspects of growth of raw materials for energy production are considered. Our dendroremediation research concept for TNT and its congeners can be easily completed for other trees of interest and it can also be applied to herbaceous plants. Knowing the current bottlenecks of phytoremediation and considering the known environmental behaviour of other contaminants, elements of our methodological approach may be easily adapted to those pollutant groups, e.g. for pesticides, pharmaceuticals, PAHs, chlorinated recalcitrants and, with some restrictions, to inorganics and to multiple contaminations. Our dynamical dendrotolerance test systems will help to predict tree growth on polluted areas. To provide some light into the black box of TNT dendroremediation, experimental data regarding the uptake, distribution and degradation of [14C]-TNT in mature tree tissues will be reported in the second part of this publication.

Biodegradation, Environmental↗

PubMed2003

Ex-situ conservation of Black poplar in Europe: genetic diversity in nine gene bank collections and their value for nature development.

Populus nigra L. is a pioneer tree species of riparian ecosystems that is threatened with extinction because of the loss of its natural habitat. To evaluate the existing genetic diversity of P. nigra within ex-situ collections, we analyzed 675 P. nigra L. accessions from nine European gene banks with three amplified fragment length polymorphism (AFLP) and five microsatellite [or simple sequence repeat (SSR)] primer combinations, and 11 isozyme systems. With isozyme analysis, hybrids could be detected, and only 3% were found in the gene bank collection. AFLP and SSR analyses revealed effectively that 26% of the accessions were duplicated and that the level of clonal duplication varied from 0% in the French gene bank collection up to 78% in the Belgian gene bank collection. SSR analysis was preferred because AFLP was technically more demanding and more prone to scoring errors. To assess the genetic diversity, we grouped material from the gene banks according to topography of the location from which the accessions were originally collected (river system or regions separated by mountains). Genetic diversity was expressed in terms of the following parameters: percentage of polymorphic loci, observed and effective number of alleles, and Nei's expected heterozygosity or gene diversity (for AFLP). Genetic diversity varied from region to region and depended, to some extent, on the marker system used. The most unique alleles were identified in the Danube region (Austria), the Rhône region (France), Italy, the Rijn region (The Netherlands), and the Ebro region (Spain). In general, the diversity was largest in the material collected from the regions in Southern Europe. Dendrograms and principal component analysis resulted in a clustering according to topography. Material from the same river systems, but from different countries, clustered together. The genetic differentiation among the regions (F(st)/G(st)) was moderate.

Cluster Analysis↗

PubMed2006

Relationships between microbial community structure and soil processes under elevated atmospheric carbon dioxide.

There is little current understanding of the relationship between soil microbial community composition and soil processes rates, nor of the effect climate change and elevated CO(2) will have on microbial communities and their functioning. Using the eastern cottonwood (Populus deltoides) plantation at the Biosphere 2 Laboratory, we studied the relationships between microbial community structure and process rates, and the effects of elevated atmospheric CO(2) on microbial biomass, activity, and community structure. Soils were sampled from three treatments (400, 800, and 1200 ppm CO(2)), a variety of microbial biomass and activity parameters were measured, and the bacterial community was described by 16S rRNA libraries. Glucose substrate-induced respiration (SIR) was significantly higher in the 1200 ppm CO(2) treatment. There were also a variety of complex, nonlinear responses to elevated CO(2). There was no consistent effect of elevated CO(2) on bacterial diversity; however, there was extensive variation in microbial community structure within the plantation. The southern ends of the 800 and 1200 ppm CO(2) bays were dominated by beta-Proteobacteria, and had higher fungal biomass, whereas the other areas contained more alpha-Proteobacteria and Acidobacteria. A number of soil process rates, including salicylate, glutamate, and glycine substrate-induced respiration and proteolysis, were significantly related to the relative abundance of the three most frequent bacterial taxa, and to fungal biomass. Overall, variation in microbial activity was better explained by microbial community composition than by CO(2) treatment. However, the altered diversity and activity in the southern bays of the two high CO(2) treatments could indicate an interaction between CO(2) and light.

Biodiversity↗

PubMed2003

Model-based assessment of aspen responses to elk herbivory in Rocky Mountain National Park, USA.

In Rocky Mountain National Park (RMNP), aspen (Populus tremuloides Michx.) has been observed to be declining on elk (Cervus elaphus nelsoni) winter range for many decades. To support elk management decisions, the SAVANNA ecosystem model was adapted to explore interactions between elk herbivory and aspen dynamics. The simulated probability of successful vegetative regeneration for senescent aspen stands declines sharply when elk densities reach levels of 3-5 elk/km2, depending on model assumptions for the seasonal duration of elk foraging activities. For aspen stands with a substantial component of younger trees, the simulated regeneration probability declines more continuously with increasing elk density, dropping below 50% from densities at 8-14 elk/km2. At the landscape scale, simulated aspen regeneration probability under a scenario of extensive seasonal use was little affected by elk population level, when this level was above 300-600 elk (25%-50% current population) over the ca. 107 km2 winter range. This was because elk distribution was highly aggregated, so that a high density of elk occupied certain areas, even at low population levels overall. At approximately current elk population levels (1000-1200 elk), only 35%-45% of senescent aspen stands are simulated as having at least a 90% probability of regeneration, nearly all of them located on the periphery of the winter range. Successful management for aspen persistence on core winter range will likely require some combination of elk population reduction, management of elk distribution, and fencing to protect aspen suckers from elk browsing.

Animals↗

PubMed2002

Climatic and stream-flow controls on tree growth in a Western montane riparian forest.

Humans have severely impacted riparian ecosystems through water diversions, impoundments, and consumptive uses. Effective management of these important areas is becoming an increasingly high priority of land managers, particularly as municipal, industrial, and recreational demands for water increase. We examined radial tree growth of four riparian tree species ( Pinus jeffreyi, Populus trichocarpa, Betula occidentalis, and Pinus monophylla) along Bishop Creek, California, and developed models relating basal area increment (BAI) and relative basal area increment (RBAI) to climatic and stream flow variables. Between years 1995-1999, univariate regression analysis with stream flow explained 29 to 61% of the variation in BAI and RBAI among all species except P. trichocarpa; growth by P. trichocarpa was not significantly related to stream flows over this period. Stepwise linear regression indicated that species responded differently to climatic variables, and models based on these variables explained between 33 to 86% of variation in BAI and RBAI during the decade of the 1990s. We examined branch growth of P. trichocarpa for sensitivity to differences in stream flow regimes and found that annual branch growth did not vary between a high- and low-flow site, but that annual branch growth was significantly higher in wet years with greater stream flows. Our results support the establishment of site-specific management goals by land managers that take into account all of the important tree species present in riparian ecosystems and their differential responses to altered hydrologic condition. Instream flow requirements for maintaining tree growth and vigor are only one of the species-specific responses that need to be evaluated, and these assessments should attempt to separate experimentally stream-flow (managed) controls from climatic (unmanaged) controls on growth.

Betula↗