Decomposition of coarse woody debris in a long-term litter manipulation experiment: A focus on nutrient availability

The majority of above-ground carbon in tropical forests is stored in wood, which is returned to the atmosphere during decomposition of coarse woody debris. However, the factors controlling wood decomposition have not been experimentally manipulated over time scales comparable to the length of this process.We hypothesized that wood decomposition is limited by nutrient availability and tested this hypothesis in a long-term litter addition and removal experiment in a lowland tropical forest in Panama. Specifically, we quantified decomposition using a 15-year chronosequence of decaying boles, and measured respiration rates and nutrient limitation of wood decomposer communities.The long-term probability that a dead tree completely decomposed was decreased in plots where litter was removed, but did not differ between litter addition and control treatments. Similarly, respiration rates of wood decomposer communities were greater in control treatments relative to litter removal plots; litter addition treatments did not differ from either of the other treatments. Respiration rates increased in response to nutrient addition (nitrogen, phosphorus, and potassium) in the litter removal and addition treatments, but not in the controls.Established decreases in concentrations of soil nutrients in litter removal plots and increased respiration rates in response to nutrient addition suggest that reduced rates of wood decomposition after litter removal were caused by decreased nutrient availability. The effects of litter manipulations differed directionally from a previous short-term decomposition study in the same plots, and reduced rates of bole decomposition in litter removal plots did not emerge until after more than 6 years of decomposition. These differences suggest that litter-mediated effects on nutrient dynamics have complex interactions with decomposition over time

Rapid evolution in response to introduced predators I: rates and patterns of morphological and life-history trait divergence

BACKGROUND: Introduced species can have profound effects on native species, communities, and ecosystems, and have caused extinctions or declines in native species globally. We examined the evolutionary response of native zooplankton populations to the introduction of non-native salmonids in alpine lakes in the Sierra Nevada of California, USA. We compared morphological and life-history traits in populations of Daphnia with a known history of introduced salmonids and populations that have no history of salmonid introductions. RESULTS: Our results show that Daphnia populations co-existing with fish have undergone rapid adaptive reductions in body size and in the timing of reproduction. Size-related traits decreased by up to 13 percent in response to introduced fish. Rates of evolutionary change are as high as 4,238 darwins (0.036 haldanes). CONCLUSION: Species introductions into aquatic habitats can dramatically alter the selective environment of native species leading to a rapid evolutionary response. Knowledge of the rates and limits of adaptation is an important component of understanding the long-term effects of alterations in the species composition of communities. We discuss the evolutionary consequences of species introductions and compare the rate of evolution observed in the Sierra Nevada Daphnia to published estimates of evolutionary change in ecological timescales

Pre-surgical Caregiver Burden and Anxiety Are Associated with Post-Surgery Cortisol over the Day in Caregivers of Coronary Artery Bypass Graft Surgery Patients.

BACKGROUND: The relationship between pre-surgical distress and diurnal cortisol following surgery has not been investigated prospectively in caregivers of coronary artery bypass graft (CABG) patients before. We aimed to examine the relationship between pre-surgical anxiety and caregiver burden and diurnal cortisol measured 2 months after the surgery in the caregivers of CABG patients. METHOD: We used a sample of 103 caregivers of elective CABG patients that were assessed 28.86 days before and 60.94 days after patients' surgery. Anxiety and caregiver burden were assessed using the anxiety subscale of the Hospital Anxiety and Depression Scale and the Oberst Burden Scale respectively. Saliva samples were collected to measure cortisol area under the curve with respect to ground (AUCg) and diurnal cortisol slope. Anxiety and caregiver burden were entered into linear regression models simultaneously. RESULTS: While high levels of pre-surgical anxiety were positively associated with increased follow-up levels of AUCg (β = 0.30, p = 0.001), greater pre-surgery perceived burden score was associated with steeper cortisol slope (β = 0.27, p = 0.017) after controlling for a wide range of covariates. CONCLUSION: These outcomes support the utility of psychological interventions aimed to increase the awareness of caregiving tasks and demands in informal caregivers

Timed Artificial Insemination: Pregnancy Rates in Sokoto Gudali Cattle Treated with Prostaglandin F2 Alpha at a Private Dairy Farm in Nigeria.

Pregnancy rates (PR) resulting from timed artificial insemination (TAI) with frozen semen were investigated in 192 Sokoto Gudali (SG) cattle following estrus synchronization under 11- and 12- day treatment intervals with prostaglandin F2 alpha (Estrumate®). Two-point inseminations at 60 h and 72 h post Estrumate® treatments were used. All cattle were randomly allocated to 2 groups i.e. A and B, such that each sub-group of A1, A2, B1 and B2 had sixteen (16) cows and thirty two (32) heifers. Furthermore, cattle in Groups A and B were administered double Estrumate® injections at 11- and 12-day intervals, respectively. Cattle in sub-groups A1 and B1 were inseminated at 60 h post second Estrumate® injection while A2 and B2 were inseminated at 72 h. Pregnancy was diagnosed using the 60-day non return to estrus and confirmed via rectal palpation at 90 days post insemination. The results showed the following PR: 33%, 83%, 33% and 33% for cattle in sub-groups A1, A2, B1 and B2, respectively. It is concluded therefore that timed artificial insemination at 72 h in SG cattle treated with double Estrumate® injections at 11-day interval produced the best pregnancy rate. These findings raises hope on the future application of TAI in breeding the SG cattle with prostaglandin F2 alpha as single agent of estrus synchronization

Of CP and other Gauge Symmetries in String Theory

We argue that \CP is a gauge symmetry in string theory. As a consequence, \CP cannot be explicitly broken either perturbatively or non-pertubatively; there can be no non-perturbative \CP-violating parameters. String theory is thus an example of a theory where all $\theta$ angles arise due to spontaneous \CP violation, and are in principle calculable.Comment: 8 page

Mutator Dynamics on a Smooth Evolutionary Landscape

We investigate a model of evolutionary dynamics on a smooth landscape which features a ``mutator'' allele whose effect is to increase the mutation rate. We show that the expected proportion of mutators far from equilibrium, when the fitness is steadily increasing in time, is governed solely by the transition rates into and out of the mutator state. This results is a much faster rate of fitness increase than would be the case without the mutator allele. Near the fitness equilibrium, however, the mutators are severely suppressed, due to the detrimental effects of a large mutation rate near the fitness maximum. We discuss the results of a recent experiment on natural selection of E. coli in the light of our model.Comment: 4 pages, 3 figure

Asymptotic generators of fermionic charges and boundary conditions preserving supersymmetry

We use a covariant phase space formalism to give a general prescription for defining Hamiltonian generators of bosonic and fermionic symmetries in diffeomorphism invariant theories, such as supergravities. A simple and general criterion is derived for a choice of boundary condition to lead to conserved generators of the symmetries on the phase space. In particular, this provides a criterion for the preservation of supersymmetries. For bosonic symmetries corresponding to diffeomorphisms, our prescription coincides with the method of Wald et al. We then illustrate these methods in the case of certain supergravity theories in $d=4$. In minimal AdS supergravity, the boundary conditions such that the supercharges exist as Hamiltonian generators of supersymmetry transformations are unique within the usual framework in which the boundary metric is fixed. In extended ${\mathcal N}=4$ AdS supergravity, or more generally in the presence of chiral matter superfields, we find that there exist many boundary conditions preserving ${\mathcal N}=1$ supersymmetry for which corresponding generators exist. These choices are shown to correspond to a choice of certain arbitrary boundary ``superpotentials,'' for suitably defined ``boundary superfields.'' We also derive corresponding formulae for the conserved bosonic charges, such as energy, in those theories, and we argue that energy is always positive, for any supersymmetry-preserving boundary conditions. We finally comment on the relevance and interpretation of our results within the AdS-CFT correspondence.Comment: 45 pages, Latex, no figures, v2: extended discussion of positive energy theorem and explicit form of fermionic generators, references adde

Brane Boxes, Anomalies, Bending and Tadpoles

Certain classes of chiral four-dimensional gauge theories may be obtained as the worldvolume theories of D5-branes suspended between networks of NS5-branes, the so-called brane box models. In this paper, we derive the stringy consistency conditions placed on these models, and show that they are equivalent to anomaly cancellation of the gauge theories. We derive these conditions in the orbifold theories which are T-dual to the elliptic brane box models. Specifically, we show that the expression for tadpoles for unphysical twisted Ramond-Ramond 4-form fields in the orbifold theory are proportional to the gauge anomalies of the brane box theory. Thus string consistency is equivalent to worldvolume gauge anomaly cancellation. Furthermore, we find additional cylinder amplitudes which give the $\beta$-functions of the gauge theory. We show how these correspond to bending of the NS-branes in the brane box theory.Comment: 14 pages, 3 epsf figures. Minor changes, references adde

Distinct Frontal Ablation Processes Drive Heterogeneous Submarine Terminus Morphology

An edited version of this paper was published by AGU. Copyright 2019 American Geophysical Union.Calving and submarine melt drive frontal ablation and sculpt the ice face of marine‐terminating glaciers. However, there are sparse observations of submarine termini, which limit estimates of spatially varying submarine melt. Here we present a detailed survey of a west Greenland glacier to reveal heterogeneity in submarine terminus morphology. We find that the majority of the terminus (~77%) is undercut, driven by calving in the upper water column and submarine melting at depth. The remaining ~23% of the terminus is overcut, driven by calving alone. We use observations of six subglacial discharge outlets, combined with a plume model, to estimate spatially varying discharge fluxes. While small discharge fluxes (<43 m3/s) feed numerous, deeply undercut outlets with subsurface plumes, ~70% of the net subglacial flux emerges at the terminus center, producing a vigorous, surface‐reaching plume. This primary outlet drives large, localized seasonal retreat that exceeds calving rates at secondary outlets