Impact of nitrogen addition on growth and carbon sequestration potential of Syzygium cumini under different carbon dioxide environment conditions

Human activities have significantly accelerated emissions of each carbon dioxide and biologically reactive nitrogen into the atmosphere. As nitrogen availability frequently limits forest productivity, it has long been anticipated that anthropogenic nitrogen deposition ought to stimulate carbon sequestration in forests. The present study aimed to understand the effects of nitrogen addition on the growth of the Syzygium cumini in ambient (408 ppm) and elevated (450 ppm, 500 ppm, 550 ppm and 600 ppm) carbon dioxide conditions. The addition of nitrogen in the form of potassium nitrate in different levels (0, 3, 6, 12, & 24 g N m^?2) was used in this study. The responses of the plant in terms of growth (shoot length, leaf length and leaf width) were examined. Multiple regression equation was used for the model fit to determine the carbon content. The carbon content was found to be higher in all ambient and elevated CO₂ conditions at the nitrogen addition level of 24 g N m^?2.     

Effect of controlled carbon dioxide on in vitro shoot multiplication in Feronia limonia (L.) Swingle

The effect of controlled carbon dioxide environment on in vitro shoot growth and multiplication in Feronia limonia (a tropical fruit plant, Family- Rutaceae) was studied. Carbon dioxide available in the ambient air of the growth room was insufficient for in vitro growth of the shoots alone. Also, the presence of sucrose only as the C-source in the medium (without CO₂), was found to be inadequate for sustainable growth and multiplication of shoots. The carbon dioxide enrichment promoted shoot multiplication and overall growth. The promotory effect of CO₂ was independent of the presence of sucrose in the medium. In the presence of both CO₂ and sucrose, an additive effect was observed producing maximum shoot growth. In the absence of sucrose a higher concentration of CO₂ (10.0)g m⁻³ was required to achieve photoautotrophic shoot multiplication comparable to ambient air controls. Highest leaf area per shoot cluster promoting shoot growth and multiplication was recorded under this treatment. Shoots growing on sucrose containing medium under controlled CO₂ environment of 0.6 g m⁻³ concentration evoked better response than ambient air controls (shoots growing on sucrose containing medium) in growth room. This treatment produced the overall best response. The present study highlighted the possibility of photoautotrophic multiplication which might prove useful for successful hardening and acclimatization in tissue culture plants.     

Sagebrush carbon allocation patterns and grasshopper nutrition: the influence of CO2 enrichment and soil mineral limitation

Summary Artemisia tridentata seedlings were grown under carbon dioxide concentrations of 350 and 650 l l^–1 and two levels of soil nutrition. In the high nutrient treatment, increasing CO₂ led to a doubling of shoot mass, whereas nutrient limitation completely constrained the response to elevated CO₂. Root biomass was unaffected by any treatment. Plant root/shoot ratios declined under carbon dioxide enrichment but increased under low nutrient availability, thus the ratio was apparently controlled by changes in carbon allocation to shoot mass alone. Growth under CO₂ enrichment increased the starch concentrations of leaves grown under both nutrient regimes, while increased CO₂ and low nutrient availability acted in concert to reduce leaf nitrogen concentration and water content. Carbon dioxide enrichment and soil nutrient limitation both acted to increase the balance of leaf storage carbohydrate versus nitrogen (C/N). The two treatment effects were significantly interactive in that nutrient limitation slightly reduced the C/N balance among the high-CO₂ plants. Leaf volatile terpene concentration increased only in the nutrient limited plants and did not follow the overall increase in leaf C/N ratio. Grasshopper consumption was significantly greater on host leaves grown under CO₂ enrichment but was reduced on leaves grown under low nutrient availability. An overall negative relationship of consumption versus leaf volatile concentration suggests that terpenes may have been one of several important leaf characteristics limiting consumption of the low nutrient hosts. Digestibility of host leaves grown under the high CO₂ treatment was significantly increased and was related to high leaf starch content. Grasshopper growth efficiency (ECI) was significantly reduced by the nutrient limitation treatment but co-varied with leaf water content.     

CYTOTAXONOMY OF THE CHARACEAE: KARYOTYPE ANALYSIS OF NITELLA OPACA AND NITELLA FLEXILIS

The haploid chromosome complement of Nitella flexilis (n = 12) is composed of two quite different basic karyotypes. One of these is symmetrical and appears to be identical to the karyotype of N. opaca (n = 6), and the other is quite asymmetrical and seems to be identical to that of an apparently undescribed dioecious Nitella from Kansas (n = 6). This may indicate that the monoecious N. flexilis has arisen through hybridization between two dioecious species. Although heteromorphic sex chromosomes were not observed in either species, it appears that female and male potentialities are confined to separate basic chromosome complements and mechanisms determining the monoecious and dioecious states are in close relation to ploidy.     

Acetogenium kivui,a new thermophilic hydrogen-oxidizing acetogenic bacterium

Hydrogen-oxidizing acetogenic bacteria in pure culture are presently represented by the two mesophilic species, Acetobacterium woodii and Clostridium aceticum. From Lake Kivu we have isolated a Gram negative, chemolithotrophic, thermophilic anaerobe (LKT-1) that oxidizes hydrogen and reduces carbon dioxide to acetic acid. It is a non-motile, non-sporeforming rod, about 0.7m in width and 2–7.5m in length, often occuring in pairs or chains. The cell wall has a banded appearance; the surface layer contains a regular array of particles with six-fold rotational symmetry. No outer membrane is present. The temperature optimum for growth is 66°C, and the pH optimum is 6.4. Organic growth substrates include glucose, mannose, fructose, pyruvate, and formate; acetate is the principal product. The doubling time for growth on hydrogen and carbon dioxide is about 2h. Vitamins are neither required nor stimulatory. Yeast extract and Trypticase enhance the final yield but do not affect the growth rate. Cysteine or sulfide are required and cannot be replaced by thioglycolate or dithiothreitol. LKT-1 was mass cultured on hydrogen and carbon dioxide in a 24.1 fermentor with a yield of 34g (wet weight) of cells. The DNA base composition as determined by buoyant density is 38 mol % guanine plus cytosine. LKT-1 appears only distantly related to physiologically similar bacteria. A new genus Acetogenium is proposed, and the species is Acetogenium kivui.     

Mitigation of growth retardation effect of plant defense activator,acibenzolar-<Emphasis Type="Italic">S</Emphasis>-methyl,in amaranthus plants by plant growth-promoting rhizobacteria

Four rhizobacterial strains and acibenzolar-S-methyl (ASM), a chemical activator, which suppressed foliar blight of amaranthus (Amaranthus tricolor L.) caused by Rhizoctonia solani Kühn were evaluated for their effect on plant growth. The experiments were performed both under sterile and non-sterile soil conditions, in the presence or absence of the pathogen. In all cases, plants treated with ASM showed significant reduction in growth, as determined by shoot length, and shoot and root dry weight when compared to other treatments. The growth retardation effect of ASM was more profound with respect to shoot length. Reduction in shoot length was least when plants were treated with a combination of the chemical activator and Pseudomonas putida 89B61 under non-sterile soil conditions in the absence of the pathogen. Both under sterile and non-sterile soil conditions, in the presence of the pathogen, reduction in shoot length due to application of ASM was diminished significantly when plants were treated with rhizobacterial strain Pseudomonas fluorescens PN026R. Combined use of plant growth-promoting rhizobacteria (PGPR) and ASM was found to be beneficial as the growth retardation effect of the plant defense activator was reduced by the growth-promoting ability of the rhizobacteria.     

Stand dynamics of Pinus flexilis-dominated subalpine forests in the Colorado Front Range

Population age structure and succession were investigated in subalpine forests in the Colorado Front Range dominated by Pinus flexilis (limber pine). Age, size, and spatial data were collected from three recent burns (<100 yr old), six ca. 240 year-old post-fire stands, and two old-growth stands (individuals > 400 yr old). The sequence of colonization of now extant trees on these post-fire sites appeared to be consistent: first Pinus flexilis, then Picea engelmannii (Engelmann spruce), and later Abies lasiocarpa (subalpine fir) with a delay between the first Pinus flexilis and Abies of as long as 140 yr. The advantage of Pinus flexilis on post-burn sites can be attributed to avian seed dispersal and the exceptional drought tolerance of its seedlings. The three recent burns were not extensive, and the delay in establishment of Picea and Abies appeared to be limited by harsh site conditions rather than lack of seed dispersal. Spatial analysis indicated a consistent, although sometimes weak, attraction between Pinus flexilis and Picea and Pinus flexilis and Abies at a scale of 1–4 m, suggesting that Pinus flexilis may facilitate establishment of Picea and Abies seedlings by providing shade or protection from wind. On xeric to slightly xeric sites, Pinus flexilis appeared to form broadly even-aged, non-regenerating populations that were gradually being replaced by Picea and Abies. Replacement is proceeding at a faster rate on the least xeric sites (north aspects, valley bottoms) compared to the most xeric sites (south aspects). On the most extreme sites, Pinus flexilis formed all-aged, self-maintaining populations with no evidence of replacement by Picea and Abies. In these old-growth forests with occasional trees aged at > 1300 yr, recruitment is continuous or episodic.     

Responses of native and invasive wetland plants to hydroperiod and water depth

Monotypic stands of reed canary grass, Phalaris arundinacea, replace native wetland vegetation where stormwater runoff alters hydrologic conditions, nutrient inflows, and sedimentation rates. We asked if different hydrologic conditions could explain the dominance of Phalaris and/or loss of the native grass, Spartina pectinata, and we compared the growth of each species alone and together under four hydroperiods (varying inundation frequency and duration) each at two water depths (surface saturation and flooding to 15 cm). When grown alone, aboveground biomass was similar for the two species, but Phalaris produced twice the stem length of Spartina via its low tissue density. Per unit biomass, Phalaris distributed its leaves over a larger canopy volume. Flooding reduced belowground biomass and increased total shoot length and shoot:root biomass of each species. Phalaris produced the most biomass, shoots, and total shoot length when wetter and drier conditions alternated weekly, while Spartina grew best with prolonged (4-week) inundation. When grown with Spartina, Phalaris changed its morphology by increasing its total shoot length:biomass ratio by 50%. However, ratios of Spartina:Phalaris aboveground biomass, shoot number, and total shoot length in two-species pots were not significantly affected by water depth or hydroperiod. We conclude that two plant attributes facilitate Phalaris' dominance of wetlands: its high ratio of total shoot length:biomass and its adaptable morphology (characterized herein as increased total shoot length:biomass when grown with Spartina).     

Recent carbon and nitrogen accumulation and acidification in soils of two Scots pine ecosystems in Southern Germany

Changes of the soil chemical status during the recent 22–30 years at two historically degraded forest sites in southern Germany (Pfaffenwinkel, Pustert) stocked with mature Scots pine (Pinus sylvestris L.) stands were studied by repeated soil inventories conducted in 1974, 1982–1984, 1994, and 2004 on replicated control plots of fertilization experiments, allowing a statistical analysis. Additionally, the nutritional status of the stands at all plots was monitored from 1964 until 2004 by annual or bi-annual analysis of current-year foliage, and stand growth was assessed by repeated stand inventories carried out in 3- to 9-year intervals. For both sites, a statistically significant systematic decrease of the forest floor C/N ratio between 1974 and 2004 from 35.4 to 29.2 (Pfaffenwinkel) and from 36.5 to 23.0 (Pustert) was observed. The soils at both sites also showed a considerable accumulation of organic carbon (210 and 400 kg C ha⁻¹ year⁻¹ for Pfaffenwinkel and Pustert, respectively) and nitrogen (13 and 18 kg N ha⁻¹ year⁻¹). In addition, the mineral topsoil at both sites has acidified considerably, indicated by significantly decreased pH values (Pustert only; mean decrease 0.1 units per decade), base saturation, and base cation stocks. The trend of N enrichment and base cation loss in the soils is mirrored by the trends of stand nutrition at both sites, which are characterized by improved N nutrition and reduced supply with K, Mg (Pustert only), and Ca. The results confirm findings of other studies indicating a recent N eutrophication and acidification of forest soils in Central Europe and southern Scandinavia. Since soils with historic degradation due to earlier non-sustainable forest utilization are widespread in Central Europe, the results obtained on our study sites probably apply for large forested areas, suggesting a significant potential of Central European forests to sequester atmospheric carbon and nitrogen not only in stand biomass, but also in the soil.     

Nitrogen incorporation and remobilization in different shoot components of field-grown winter oilseed rape (Brassica napus L.) as affected by rate of nitrogen application and irrigation

The seasonal course of nitrogen uptake, incorporation and remobilization in different shoot components of winter oilseed rape (Brassica napus L.) was studied under field conditions including three rates of ¹⁵N labelled nitrogen application (0, 100 or 200 kg N ha^-1) and two irrigation treatments (rainfed or watered at a deficit of 20 mm). The total amount of irrigation water applied was 260 mm, split over 13 occasions in a 7-week-period ranging from 1 week before onset of flowering until 4 weeks after flowering.Nitrogen application and irrigation increased plant growth and nitrogen accumulation. Irrespective of N and irrigation treatment more than 50% of total shoot N was present in the stem when flowering started. At the end of flowering, pod walls were the main N store containing about 30–40% of shoot N. The quantities of N remobilized from stems and pod walls amounted in all treatments to about 70% of the N present in these organs at mid-flowering. At harvest, stem and pod walls each contained about 10% of total shoot N, the remaining 80% being incorporated into seeds. The main component contributing to the response of seed N accumulation to nitrogen application and irrigation was pods in axillary racemes. Up to 20 kg N ha^-1, corresponding to about 10% of final shoot N content, was lost from the plants by leaf drop.Irrigation increased the recovery at harvest of applied N from 30% to about 50%, while the level of N application did not affect the N recovery. ¹⁵N labelled (fertilizer derived) nitrogen constituted a greater proportion of the N content in old leaves than in young leaves and increased with age in the former, but not in the latter. Relative to soil N, fertilizer derived N also contributed more to the N content of vegetative than to that of reproductive shoot components. Small net changes in shoot N content after flowering reflected a balance between N import and export, leading to continuous dilution of ¹⁵N labelled N with unlabelled N.     

Chronological and Isotopic data support a revision for the timing of cave bear extinction in Mediterranean Europe

Abstract

The Cave Bear, Ursus spelaeus (sensu lato), was one of many megafaunal species that became extinct during the Late Pleistocene in Europe. With new data we revisit the debate about the extinction and paleoecology of this species by presenting new chronometric, isotopic and taphonomic evidence from two Palaeolithic cave bear sites in northeastern Italy: Paina Cave and Trene Cave. Two direct radiocarbon dates on well-preserved collagen have yielded ages around 24,200–23,500 cal yr BP, which make them the latest known representatives of the species in Europe. The carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopic values of bone collagen exhibit values similar to those of older cave bears from Swabian Jura and France, suggesting that the feedings preferences of cave bears remained unchanged until the disappearance of this species in Europe. Several bear remains preserved traces of human modification such as cut marks, which enables a reconstruction of the main steps of fur recovery and the butchering process. The broad range of plant types available and the favorable location of Berici Hills may have played an important role in the range expansion of cave bears and their interaction with the Paleolithic hunters settled the same area.     

Estimates of seasonal nitrogen fixation of annual subterranean clover-based pastures using the15N natural abundance technique

Annual pasture legumes play a key role in ley farming systems of southern Australia, providing biologically fixed nitrogen (N) to drive the production of the pastures as well as subsequent crops grown in rotation. Seasonal inputs of biologically fixed N in shoot biomass of the subterranean clover (Trifolium subterraneum) component of grazed annual pastures were assessed using the¹⁵N natural abundance technique and appropriately timed sampling of herbage dry matter (DM) for N accumulation. At three study sites spanning a gradient across the Western Australian wheatbelt from 300 to 600 mm annual rainfall the performance of the clover and non-legume herbs and grasses was examined as paired comparisons involving two management treatments expected to give contrasting effects on pasture productivity, botanical composition and N₂ fixation. The proportion of clover N derived from atmospheric N₂ fixation (%Ndfa) ranged from 65 to 95% across sites, treatments and sampling times. Amounts of fixed N accumulated in clover shoot biomass ranged from 50 to 125 kg ha⁻¹, and paralleled trends in clover production. Substantial increases in pasture production in high yielding treatments generally occurred without decrease in %Ndfa, suggesting that N₂ fixation was essentially non-limiting to performance of the clover component. Seasonal profiles for accumulation of fixed N were skewed towards the late winter and spring period, particularly in low plant density pastures following a cereal crop. There were seasonal, site and treatment-specific effects on the proportion of clover and non-legume pasture components and consequently clover yield and N₂ fixation were variably affected by competition from non-legume species.     

A spatial model of interspecific competition and selective predation: The case of the two Hippolais

Mutual exclusion between congeneric species has been observed such as the case of the grey and red squirrels in Great Britain and the case of the twoHippolais warbler speciesHippolais icterina andH. polyglotta in Europe. This process can lead to the formation of an extinction wave which propagates. Two main assumptions are tested, competition and selective predation. The aim of this work is to present spatial models of these two processes. The animals of two species are assumed to move on a two dimensional array of spatial patches with local interactions of competition or of selective predation between them. We focus on the case of mutual exclusion. Initially, the two competing species occupy complementary areas in an array of spatial patches with a small common zone. Numerical simulations show that under particular conditions, one species gets extinct and the other invades the whole set of spatial patches. These simulations show that with time, the length of the overlapping zone stabilizes and moves at a constant velocity. The limit length of the overlapping band and the velocity of the extinction wave are found to be functions of the parameters of the models. We relate this general model to the case of two sibling species of birds:H. icterina andH. polyglotta.     

Effort to reconstruct past population history in the fern <Emphasis Type="Italic">Blechnum spicant</Emphasis>

Our aim was to evaluate the potential of existing herbarium collections in reconstructing the past population history of the rediscovered clone of the regionally extinct Blechnum spicant by comparing it with herbarium material from previous sites of occurrences in Finland and elsewhere in northern Europe, as well as to reveal the genetic and geographic relationship among the samples. We detected a total of nine polymorphic sites within the three sequenced regions, two SCAR markers developed now for B. spicant and the chloroplast trnL-trnF spacer, totalling 763 bp. Despite low variability, the phylogeographic analysis revealed the presence of some geographic pattern among the samples, of which all except one represented herbarium samples of up to 100 years of age. The rediscovered clone of B. spicant proved to represent the prevalent genotype occurring in northern Europe. The studied sequences were neutral in terms of evolution. It is apparent that existing herbarium collections are useful resources for a range of evolutionary and population studies.     

Impact of two shoot-galling biological control candidates on Russian knapweed, Acroptilon repens

Russian knapweed, Acroptilon repens, is one of the most serious exotic invaders of temperate grasslands in North America. Here we present results from a field experiment in which we quantified the impact of two potential biological control agents, the gall wasp Aulacidea acroptilonica V.Bel. (Hymenoptera, Cynipidae) and the gall midge Jaapiella ivannikovi Fedotova (Diptera, Cecidomyiidae), on A. repens under field conditions in the plant’s native range in Uzbekistan. Attack by A. acroptilonica reduced shoot length by 21%, above-ground biomass by 25% and seed output by 75%, while attack by J. ivannikovi reduced shoot length by 12%, above-ground biomass by 24%, and seed output by 92%. The results of these field experiments are likely to accurately reflect the potential of these two gall formers to reduce above-ground biomass and sexual reproduction of A. repens shoots, since the shoots were part of a clonal network. Despite this, the attacked shoots were not able to compensate for the reallocation of plant resources to gall formation. Moreover, the mean number of galls per shoot obtained in the experiments was within the range of observed gall incidences in the native range. The impact of these two gall-forming insects on Russian knapweed in North America will depend on the population size the species reach and on the timing of attack. The highest impact is likely to occur when the insects attack shoots that have not yet started producing flower-buds.     

A new notion on the heteropterofauna (Insecta: Hemiptera,Heteroptera) from the Pliocene of Willershausen (N Germany)

Mainly based on collections from Willershausen (Lower Saxony, North Germany), the Pliocene Heteroptera fauna of West Europe is briefly revised. The present compilation includes a checklist with taxonomic and systematic corrections ofJordan’s (1967, 1969) type materials. Naucoroid water bugs of the family Aphelocheiridae are distinguished and the extinct species of the genusAphelocheirus are redescribed. The new genusWillershausenia n.gen. (type species:Nabis strausi Jordan, 1969) is defined and transferred to the coreoid family Alydidae.      

Biochemical and morphological evidence for host race evolution in desert mistletoe,Phoradendron californicum (Viscaceae)

Allozymes and morphological characters were used to test whether host race evolution—the genetic divergence of parasitic populations caused by adaptation to different host species—has occurred in desert mistletoe,Phoradendron californicum. Populations ofPhoradendron californicum from two hosts,Acacia greggii andProsopis glandulosa, were surveyed from the Mojave and Colorado deserts. Electrophoretic data indicated genetic differentiation of mistletoes occurring on these hosts. Three of four morphological characters (internode length, main shoot lateral shoot diameter ratio and berry color) also showed significant host-specific differentiation. These data support the hypothesis that host race formation has occurred or is occurring in this parasitic angiosperm.     

Nitrogen and carbon dynamics in C3 and C4 estuarine marsh plants grown under elevated CO2 in situ

Summary Carbon dioxide concentrations were elevated in three estuarine communities for an entire growing season. Open top chambers were used to raise CO₂ concentrations ca. 336 ppm above ambient in monospecific communities of Scirpus olneyi (C₃) and Spartina patens (C₄), and a mixed community of S. olneyi, S. patens and Distichlis spicata (C₄). Nitrogen and carbon concentration (% wt) of aboveground tissue was followed throughout growth and senescence. Green shoot %N was reduced and %C was unchanged under elevated CO₂ in S. olneyi. This resulted in a 20%–40% increase in tissue C/N ratio. There was no effect of CO₂ on either C₄ species. Maximum aboveground N (g/m²) was unchanged in S. olneyi, indicating that increased productivity under elevated CO₂ was dependent on reallocation of stored N. There was no change in the N recovery efficiency of S. olneyi in pure stand and a decrease in the mixed community. Litter C/N ratio was not affected by elevated CO₂ suggesting that decomposition and N mineralization rates will also remain unchanged. Continued growth responses to elevated CO₂ could, however, be limited by the ability of S. olneyi to increase the total aboveground N pool.