Intra- and interspecific facilitation in mangroves may increase resilience to climate change threats

Mangroves are intertidal ecosystems that are particularly vulnerable to climate change. At the low tidal limits of their range, they face swamping by rising sea levels; at the high tidal limits, they face increasing stress from desiccation and high salinity. Facilitation theory may help guide mangrove management and restoration in the face of these threats by suggesting how and when positive intra- and interspecific effects may occur: such effects are predicted in stressed environments such as the intertidal, but have yet to be shown among mangroves. Here, we report the results of a series of experiments at low and high tidal sites examining the effects of mangrove density and species mix on seedling survival and recruitment, and on the ability of mangroves to trap sediment and cause surface elevation change. Increasing density significantly increased the survival of seedlings of two different species at both high and low tidal sites, and enhanced sediment accretion and elevation at the low tidal site. Including Avicennia marina in species mixes enhanced total biomass at a degraded high tidal site. Increasing biomass led to changed microenvironments that allowed the recruitment and survival of different mangrove species, particularly Ceriops tagal.     

GGA Autoinhibition Revisited

The cytosolic adaptors GGA1‐3 mediate sorting of transmembrane proteins displaying a C‐terminal acidic dileucine motif (DXXLL) in their cytosolic domain. GGA1 and GGA3 contain similar but intrinsic motifs that are believed to serve as autoinhibitory sites activated by the phosphorylation of a serine positioned three residues upstream of the DXXLL motif. In the present study, we have subjected the widely acknowledged concept of GGA1 autoinhibition to a thorough structural and functional examination. We find that (i) the intrinsic motif of GGA1 is inactive, (ii) only C‐terminal DXXLL motifs constitute active GGA binding sites, (iii) while aspartates and phosphorylated serines one or two positions upstream of the DXXLL motif increase GGA1 binding, phosphoserines further upstream have little or no influence and (iv) phosphorylation of GGA1 does not affect its conformation or binding to Sortilin and SorLA. Taken together, our findings seem to refute the functional significance of GGA autoinhibition in particular and of intrinsic GGA binding motifs in general.     

Determination of PCR efficiency in chelex-100 purified clinical samples and comparison of real-time quantitative PCR and conventional PCR for detection of Chlamydia pneumoniae

Background  

Chlamydia pneumoniae infection has been detected by serological methods, but PCR is gaining more interest. A number of different PCR assays have been developed and some are used in combination with serology for diagnosis. Real-time PCR could be an attractive new PCR method; therefore it must be evaluated and compared to conventional PCR methods.     

The phytogeography of Denmark revisited

Patterns of vascular plant diversity in Denmark are examined, based on the most recently published Danish Flora. The highest diversity is found on the major isles of Sjælland, Møn, Falster and Bornholm, but many rare taxa occur in Jylland. Two different cluster analyses suggest a division of Denmark into six phytogeographical regions, which only partly supports earlier, more subjective divisions of Denmark. Our results suggest that north- and northwestern Jylland and the isles of Læsø and Anholt belong to the boreo-nemoral phytogeographical region, due to their high number of northern taxa, which clearly differentiate them from the rest of Denmark, despite the lack of typical boreo-nemoral tree species, such as Pinus sylvestris.Because the tree component of vegetation often has been changed by man, the classical division of Scandinavia based on a few woody species is inappropriate. We conclude that tree-species oriented approaches are invalid for phytogeographical classifications.Classification, based on the whole flora, and if possible also involving environmental information, is likely to be more successful and should be addressed in future phytogeographical studies.     

Tree development in structural soil – an empirical below-ground in-situ study of urban trees in Copenhagen,Denmark

Aims

The purpose of this study is to evaluate root and stem growth, nutrient status and soil properties of a tree planting in structural soil.

Methods

Root and stem growth were measured at an 10-year-old urban planting of Tilia x europaea L. ‘Pallida’ established in structural soil on a paved square in Copenhagen, Denmark.Root abundance was quantified and soil profiles were established at three different distances from 10 trees (1.0, 1.9, and 2.9 m). Soil and leaf samples were analysed for nutrient concentrations.

Results

Abundant root presence was measured across the entire profile of structural soil (160?×?60 cm) at all distances, provided that structural soil layers were constructed correctly. Erroneously constructed structural soil layers however, resulted in impaired tree and root growth. Coarse root morphology was affected by the confined growing space in the voids of the stone matrix. The soil was relatively alkaline with an average pH (CaCl₂) of 7.3. Foliar analysis revealed deficiencies of K and Mn. These deficiencies might be due to a combined effect of high pH and low soil concentrations of these nutrients.

Conclusions

The study documents that correctly constructed structural soils allow and encourage root growth in load bearing layers.

     

Methane oxidation in contrasting soil types: responses to experimental warming with implication for landscape‐integrated CH4 budget

Arctic ecosystems are characterized by a wide range of soil moisture conditions and thermal regimes and contribute differently to the net methane (CH₄) budget. Yet, it is unclear how climate change will affect the capacity of those systems to act as a net source or sink of CH₄. Here, we present results of in situ CH₄ flux measurements made during the growing season 2014 on Disko Island (west Greenland) and quantify the contribution of contrasting soil and landscape types to the net CH₄ budget and responses to summer warming. We compared gas flux measurements from a bare soil and a dry heath, at ambient conditions and increased air temperature, using open‐top chambers (OTCs). Throughout the growing season, bare soil consumed 0.22 ± 0.03 g CH₄‐C m^?2 (8.1 ± 1.2 g CO₂‐eq m^?2) at ambient conditions, while the dry heath consumed 0.10 ± 0.02 g CH₄‐C m^?2 (3.9 ± 0.6 g CO₂‐eq m^?2). These uptake rates were subsequently scaled to the entire study area of 0.15 km², a landscape also consisting of wetlands with a seasonally integrated methane release of 0.10 ± 0.01 g CH₄‐C m^?2 (3.7 ± 1.2 g CO₂‐eq m^?2). The result was a net landscape sink of 12.71 kg CH₄‐C (0.48 tonne CO₂‐eq) during the growing season. A nonsignificant trend was noticed in seasonal CH₄ uptake rates with experimental warming, corresponding to a 2% reduction at the bare soil, and 33% increase at the dry heath. This was due to the indirect effect of OTCs on soil moisture, which exerted the main control on CH₄ fluxes. Overall, the net landscape sink of CH₄ tended to increase by 20% with OTCs. Bare and dry tundra ecosystems should be considered in the net CH₄ budget of the Arctic due to their potential role in counterbalancing CH₄ emissions from wetlands – not the least when taking the future climatic scenarios of the Arctic into account.     

Effect of neurotensin and neurotensin fragments on gastric acid secretion in man

The effect of intravenous infusion of neurotensin (NT) and NT-fragments on pentagastrin stimulated gastric acid secretion was investigated in healthy subjects. Neurotensin was infused in three doses (72, 144 and 288 pmol/kg per h). An N-terminal fragment (NT 1-8), a C-terminal fragment (NT 8-13) and an NT-analogue, substituted at the C-terminal tyrosine residue (Phe11-NT) were infused in two doses (72 and 144 pmol/kg per h). Concentrations of the infused peptides were measured in peripheral venous blood by radioimmunoassay. Plasma levels of NT 1-13, NT 1-8 and Phe11-NT increased in a dose-dependent manner; NT 1-13 to 50 (34-69), 78 (54-113) and 143 (112-242) pmol/l (medians and range) at 72, 144 and 288 pmol/kg per h, NT 1-8 to 405 (340-465) and 1215 (915-1300) pmol/l, and Phe11-NT to 200 (110-245) and 390 (250-410) pmol/l at 72 and 144 pmol/kg per h, respectively. Increases in plasma levels of NT 8-13 could not be detected during the infusion, suggesting that the fragment is rapidly metabolized in man. Neurotensin 1-13 inhibited gastric acid secretion in a dose-dependent manner and the decrease in gastric acid secretion was linearly related to plasma levels of NT 1-13. Neurotensin 1-8 and NT 8-13 inhibited gastric acid secretion only at 144 pmol/kg per h, while the analogue Phe11-NT had no effect. The results showed that the inhibition of gastric acid secretion produced by NT was dose-dependent and linearly related to circulating levels of NT, and that under physiological conditions this effect presumably is elicited by the C-terminal part of the peptide.     

To boldly go: individual differences in boldness influence migratory tendency

Partial migration, whereby only a fraction of the population migrates, is thought to be the most common type of migration in the animal kingdom, and can have important ecological and evolutionary consequences. Despite this, the factors that influence which individuals migrate and which remain resident are poorly understood. Recent work has shown that consistent individual differences in personality traits in animals can be ecologically important, but field studies integrating personality traits with migratory behaviour are extremely rare. In this study, we investigate the influence of individual boldness, an important personality trait, upon the migratory propensity of roach, a freshwater fish, over two consecutive migration seasons. We assay and individually tag 460 roach and show that boldness influences migratory propensity, with bold individuals being more likely to migrate than shy fish. Our data suggest that an extremely widespread personality trait in animals can have significant ecological consequences via influencing individual-level migratory behaviour.     

Variable individual consistency in timing and destination of winter migrating fish

Migration is an important event in the life history of many animals, but there is considerable variation within populations in the timing and final destination. Such differential migration at the population level can be strongly determined by individuals showing different consistencies in migratory traits. By tagging individual cyprinid fish with uniquely coded electronic tags, and recording their winter migrations from lakes to streams for 6 consecutive years, we obtained highly detailed long-term information on the differential migration patterns of individuals. We found that individual migrants showed consistent site fidelities for over-wintering streams over multiple migratory seasons and that they were also consistent in their seasonal timing of migration. Our data also suggest that consistency itself can be considered as an individual trait, with migrants that exhibit consistent site fidelity also showing consistency in migratory timing. The finding of a mixture of both consistent and inconsistent individuals within a population furthers our understanding of intrapopulation variability in migration strategies, and we hypothesize that environmental variation can maintain such different strategies.     

Regime shifts in shallow lakes: the importance of seasonal fish migration

Shallow eutrophic lakes commonly exist in two alternative stable states: a clear-water state and a turbid water state. A number of mechanisms, including both abiotic and biotic processes, buffer the respective states against changes, whereas other mechanisms likely drive transitions between states. Our earlier research shows that a large proportion of zooplanktivorous fish populations in shallow lakes undertake seasonal migrations where they leave the lake during winter and migrate back to the lake in spring. Based on our past research, we propose a number of scenarios of how feedback processes between the individual and ecosystem levels may affect stability of alternative stable states in shallow lakes when mediated by fish migration. Migration effects on shallow lakes result from processes at different scales, from the individual to the ecosystem. Our earlier research has shown that ecosystem properties, including piscivore abundance and zooplankton productivity, affect the individual state of zooplanktivorous fish, such as growth rate or condition. Individual state, in turn, affects the relative proportion and timing of migrating zooplanktivorous fish. This change, in turn, may stabilize states or cause runaway processes that eventually lead to state shifts. Consequently, such knowledge of processes coupled to seasonal migration of planktivorous fish should increase our understanding of shallow lake dynamics.