Bacterial and phytoplankton dynamics in a sub-tropical estuary

Heterotrophic bacterial and biomass, production, specific growth rates and growth efficiencies were studied in July 2001 and January 2002 during both spring and neap tides, along a tidal cycle, at three sites in a subtropical estuary. Major freshwater inputs located in the Northern region led to differences in both and bacterioplankton biomass and activity along the estuary. While in the Northern region is light-limited, with mean production (PP) between 1.1 and 1.9 mu g C l(-1) h(-1) and mean specific growth rates (PSG) between 0.14 and 0.16 d(-1), the Southern region registered values as high as 24.7 mu g C l(-1) h(-1) for PP and 2.45 d(-1) (mean PP between 3.4 and 7.3 mu g C l(-1) h(-1); mean PSG between 0.28 and 0.57 d(-1)). On the other hand, maximum bacterial production (BP: 63.8 mu g C l(-1) h(-1)) and specific growth rate (BSG: 32.26 d(-1)) were observed in the Northern region (mean BP between 3.4 and 12.8 mu g C l(-1) h(-1); mean BSG between 1.98 and 6.67 day(-1)). These bacterial activity rates are among the highest recorded rates in estuarine and coastal waters, indicating that this system can be highly heterotrophic, due to high loads of allochthonous carbon (mainly derived from mangrove forest). Our results also showed that, despite that BP rates usually exceeded PP, in the Southern region BP may be partially supported (similar to 45%) by PP, since a significant regression was observed between BP and PP (r = 0.455, P < 0.001).

Tiller population density and tillering dynamics in marandu palisade grass subjected to strategies of rotational stocking management and nitrogen fertilization

The objective of this experiment was to evaluate tiller population density and the dynamics of the tillering process in marandu palisade grass subjected to strategies of rotational stocking management and nitrogen fertilization. Treatments corresponded to combinations between two targets of pre-grazing conditions (sward surface height of 25 and 35 cm) and two rates of nitrogen application (50 and 200 kg ha-1 year-1), and were allocated to experimental units according to a 2 x 2 factorial arrangement in a randomised complete block design, with four replications. The following response variables were studied: initial (TPDi), intermediate (TPDm) and final (TPDf) tiller population density as well as the rates of tiller appearance (TAR) and death (TDR) and the tiller population stability index (SI). TPDi was similar to all treatments, with differences in tiller population density becoming more pronounced as the experiment progressed, resulting in larger TPDf on swards managed at 25 cm pre-grazing height. Tiller death was larger on swards managed at 35 cm, with differences in tiller appearance being recorded only from February 2010 onwards. Stability of tiller population was higher on swards managed at 25 cm pre-grazing height. Overall, there was no effect of nitrogen on the studied variables, and the most adequate grazing strategy corresponded to the pre-grazing height of 25 cm, regardless of the nitrogen application rate used.

Interactions between physical forcing, water circulation and phytoplankton dynamics in a microtidal estuary

Eliminadas las páginas en blanco

Phylogeny and population dynamics in European Reticulitermes and Kalotermes genera (Insecta, Isoptera)

The aim of this thesis is to detect the phylogeny and the population dynamics of the European termites of the genera Reticulitermes and Kalotermes, by the use of different mitochondrial (16S, COI/tRNA/COII, CR) and nuclear (microsatellites and Inter-SINE) molecular markers. In the phylogenetic analyses, the obtained results have well defined the cladogenetic events that generated the nowadays species biodiversity of the genus Reticulitermes, while the analysis of the Kalotermes flavicollis taxon showed the presence of at least four genetic clades, defined on the basis of the geographical distance. The second part of the thesis is centred on the population dynamics of two species: Reticulitermes urbis and Kalotermes flavicollis. The first species, native of the Balkans, is known to be present in some cities of Italy and France. I’ve analyzed the colony genetic structure of the introduced population of Bagnacavallo (RA, Italy), using nine microsatellite loci. The obtained results are in accordance with those obtained from another population in France: this species in fact confirms its invasive and infestation capacities. The analysis of the natural population of K. flavicollis, performed with a combination of mitochondrial (control region) and nuclear (microsatellites and I-SINE) markers, clearly evidenced the presence of two genetic lineages that coexist in the same area. Moreover, results clearly indicate that the cross-breeding is allowed. Finally, the whole results are discussed in a comparative view to better understand the differences in ecology, evolutionary dynamics and colony social structure between these two genera.

Soil application of Meliaceae derivatives: effect on carbon and nitrogen dynamics in the soil-plant system

The effect of soil incorporation of 7 Meliaceae derivatives (6 commercial neem cakes and leaves of Melia azedarach L.) on C and N dynamics and on nutrient availability to micropropagated GF677 rootstock was investigated. In a first laboratory incubation experiment the derivatives showed different N mineralization dynamics, generally well predicted by their C:N ratio and only partly by their initial N concentration. All derivatives increased microbial biomass C, thus representing a source of C for the soil microbial population. Soil addition of all neem cakes (8 g kg-1) and melia leaves (16 g kg-1) had a positive effect on plant growth and increased root N uptake and leaf green colour of micropropagated plants of GF677. In addition, the neem cakes characterized by higher nutrient concentration increased P and K concentration in shoot and leaves 68 days after the amendment. In another experiment, soil incorporation of 15N labeled melia leaves (16 g kg-1) had no effect on the total amount of plant N, however the percentage of melia derived-N of treated plants ranged between 0.8% and 34% during the experiment. At the end of the growing season, about 7% of N added as melia leaves was recovered in plant, while 70% of it was still present in soil. Real C mineralization and the priming effect induced by the addition of the derivatives were quantified by a natural 13C abundance method. The real C mineralization of the derivatives ranged between 22% and 40% of added-C. All the derivatives studied induced a positive priming effect and, 144 days after the amendment, the amount of C primed corresponded to 26% of added-C, for all the derivatives. Despite this substantial priming effect, the C balance of the soil, 144 days after the amendment, always resulted positive.

Age, Sex, and Telomere Dynamics in a Long-Lived Seabird with Male-Biased Parental Care

The examination of telomere dynamics is a recent technique in ecology for assessing physiological state and age-related traits from individuals of unknown age. Telomeres shorten with age in most species and are expected to reflect physiological state, reproductive investment, and chronological age. Loss of telomere length is used as an indicator of biological aging, as this detrimental deterioration is associated with lowered survival. Lifespan dimorphism and more rapid senescence in the larger, shorter-lived sex are predicted in species with sexual size dimorphism, however, little is known about the effects of behavioral dimorphism on senescence and life history traits in species with sexual monomorphism. Here we compare telomere dynamics of thick-billed murres (Uria lomvia), a species with male-biased parental care, in two ways: 1) cross-sectionally in birds of known-age (0-28 years) from one colony and 2) longitudinally in birds from four colonies. Telomere dynamics are compared using three measures: the telomere restriction fragment (TRF), a lower window of TRF (TOE), and qPCR. All showed age-related shortening of telomeres, but the TRF measure also indicated that adult female murres have shorter telomere length than adult males, consistent with sex-specific patterns of ageing. Adult males had longer telomeres than adult females on all colonies examined, but chick telomere length did not differ by sex. Additionally, inter-annual telomere changes may be related to environmental conditions; birds from a potentially low quality colony lost telomeres, while those at more hospitable colonies maintained telomere length. We conclude that sex-specific patterns of telomere loss exist in the sexually monomorphic thick-billed murre but are likely to occur between fledging and recruitment. Longer telomeres in males may be related to their homogamous sex chromosomes (ZZ) or to selection for longer life in the care-giving sex. Environmental conditions appeared to be the primary drivers of annual changes in adult birds.

Species mobility and frequency dynamics in a Swiss limestone grassland

Community dynamics in a calcareous grassland (Mesobrometum) in Egerkingen (Jura mountains, Switzerland) were investigated for 53 non-woody species in 25 1-m2 plots over 6 years. 50 0.0 1-m2 subplots per plot were recorded. The derived variables were spatial frequency, temporal frequency, frequency fluctuation, turnover, and cumulative frequency (each species), and cumulative species richness (all species). Spectra for 53 species of all variables were different for the two investigated spatial scales (0.0 1 m2, 1 m2). The comparison with other investigations of similar grass lands showed that the behaviour of some species is specific for this type of vegetation in general (e.g. Achillea millefolium, Arrhenatherum elatius, Bromus erectus ), but most species behaved in a stand-specific way, i.e. they may play another (similar or completely different) role in another grassland stand. Six spatio-temporal patterns were defined across species. To understand community dynamics, not only the dynamics of mobility but also of frequency fluctuations and spatial distribution of the species are fundamental. In addition, the understanding of temporal behaviour of all species present should be included. Averages always hide important information of vegetation dynamics, as was shown by the present investigation.

Transient simulations of the carbon and nitrogen dynamics in northern peatlands: from the Last Glacial Maximum to the 21st century

The development of northern high-latitude peatlands played an important role in the carbon (C) balance of the land biosphere since the Last Glacial Maximum (LGM). At present, carbon storage in northern peatlands is substantial and estimated to be 500 ± 100 Pg C (1 Pg C = 1015 g C). Here, we develop and apply a peatland module embedded in a dynamic global vegetation and land surface process model (LPX-Bern 1.0). The peatland module features a dynamic nitrogen cycle, a dynamic C transfer between peatland acrotelm (upper oxic layer) and catotelm (deep anoxic layer), hydrology- and temperature-dependent respiration rates, and peatland specific plant functional types. Nitrogen limitation down-regulates average modern net primary productivity over peatlands by about half. Decadal acrotelm-to-catotelm C fluxes vary between −20 and +50 g C m−2 yr−1 over the Holocene. Key model parameters are calibrated with reconstructed peat accumulation rates from peat-core data. The model reproduces the major features of the peat core data and of the observation-based modern circumpolar soil carbon distribution. Results from a set of simulations for possible evolutions of northern peat development and areal extent show that soil C stocks in modern peatlands increased by 365–550 Pg C since the LGM, of which 175–272 Pg C accumulated between 11 and 5 kyr BP. Furthermore, our simulations suggest a persistent C sequestration rate of 35–50 Pg C per 1000 yr in present-day peatlands under current climate conditions, and that this C sink could either sustain or turn towards a source by 2100 AD depending on climate trajectories as projected for different representative greenhouse gas concentration pathways.

Scent-marking behaviour and social dynamics in a wild population of Eurasian lynx Lynx lynx.

Scent-marking is widespread among mammals and has been observed in many felid species. Although the behaviour is well-described, little is known about its function in wild felid populations. We investigated patterns of scent-marking and its role in intra- and intersexual communication among resident and non-resident Eurasian lynx Lynx lynx by observing interactions among wild lynx at natural marking sites by means of infrared camera traps. Marking activity of resident animals showed a peak during the mating season and was lowest during the time when females gave birth and lactated. Both sexes scent-marked, but male lynx visited marking sites much more often than females and marked relatively more often when visiting a site. Most visits to marking sites were by residents but we also observed scent-marking by non-residents. Juveniles were never observed marking. We found no evidence of lynx regularly renewing scent-marks after a certain 'expiry date' but the presence of a strange scent-mark triggered over-marking. Males responded similarly to the presence of another individual's scent-mark, irrespective of whether it was the top- or the underlying scent-mark in a mixture of scent-marks they encountered. Our results suggest that marking sites could serve as 'chemical bulletin boards', where male lynx advertise their presence and gain information on ownership relationships in a given area. Females placed their urine marks on top of the ones left by resident males, but further studies are needed to explain the functions of over-marking in females.

Financial Liberalization and Inflationary Dynamics in the Context of a Small Open Economy

The paper develops a short-run model of a small open financially repressed economy characterized by unorganized money markets, capital good imports, capital mobility, wage indexation, and flexible exchange rates. The analysis shows that financial liberalization, in the form of an increased rate of interest on deposits and tight monetary policy, unambiguously and unconditionally causes deflation. Moreover, the results do not depend on the degree of capital mobility and structure of wage setting. The paper recommends that a small open developing economy should deregulate interest rates and tighten monetary policy if reducing inflation is a priority. The pre-requisite for such a policy, however, requires the establishment of a flexible exchange rate regime.

Trade, Exchange Rates, and Macroeconomic Dynamics in East Asia: Why the Electronics Cycle Matters

Against the background of increasing regional trade and investment, there is growing interest in monetary and macroeconomic policy coordination in East Asia. Although there is a sizable literature on macroeconomic linkages among East Asian countries and the potential merit of policy coordination in the region, the existing studies tend to examine these issues exclusively in terms of macroeconomic variables and do not consider how these aggregate variables are influenced by one prominent feature of a number of East Asian economies: their heavy dependence on the electronics industry. Although active engagement in the global electronics industry has been a powerful growth engine for the Asian countries, it has also left their economies vulnerable to cyclical fluctuations in the world electronics market. As the cycle of the global electronics industry exerts profound impacts on the medium-term dynamics of the Asian economies, it is imperative to take an explicit account of its influence when studying the way in which the regional economies are linked to one another and how this relationship can be altered by a specific policy initiative. We illustrate the importance of this point by examining recent studies on: (1) trade competition between China andother Asian countries and the role of the Chinese renminbi therein; and (2) the effect offluctuations in the yen/dollar exchange rate on the regional economies.