High aboveground carbon stock of African tropical montane forests

Tropical forests store 40-50 per cent of terrestrial vegetation carbon(1). However, spatial variations in aboveground live tree biomass carbon (AGC) stocks remain poorly understood, in particular in tropical montane forests(2). Owing to climatic and soil changes with increasing elevation(3), AGC stocks are lower in tropical montane forests compared with lowland forests(2). Here we assemble and analyse a dataset of structurally intact old-growth forests (AfriMont) spanning 44 montane sites in 12 African countries. We find that montane sites in the AfriMont plot network have a mean AGC stock of 149.4 megagrams of carbon per hectare (95% confidence interval 137.1-164.2), which is comparable to lowland forests in the African Tropical Rainforest Observation Network(4) and about 70 per cent and 32 per cent higher than averages from plot networks in montane(2,5,6) and lowland(7) forests in the Neotropics, respectively. Notably, our results are two-thirds higher than the Intergovernmental Panel on Climate Change default values for these forests in Africa(8). We find that the low stem density and high abundance of large trees of African lowland forests(4) is mirrored in the montane forests sampled. This carbon store is endangered: we estimate that 0.8 million hectares of old-growth African montane forest have been lost since 2000. We provide country-specific montane forest AGC stock estimates modelled from our plot network to help to guide forest conservation and reforestation interventions. Our findings highlight the need for conserving these biodiverse(9,10) and carbon-rich ecosystems. The aboveground carbon stock of a montane African forest network is comparable to that of a lowland African forest network and two-thirds higher than default values for these montane forests.Peer reviewe

Gaia Early Data Release 3: The celestial reference frame (Gaia-CRF3)

Context. Gaia-CRF3 is the celestial reference frame for positions and proper motions in the third release of data from the Gaia mission, Gaia DR3 (and for the early third release, Gaia EDR3, which contains identical astrometric results). The reference frame is defined by the positions and proper motions at epoch 2016.0 for a specific set of extragalactic sources in the (E)DR3 catalogue. Aims. We describe the construction of Gaia-CRF3 and its properties in terms of the distributions in magnitude, colour, and astrometric quality. Methods. Compact extragalactic sources in Gaia DR3 were identified by positional cross-matching with 17 external catalogues of quasi-stellar objects (QSO) and active galactic nuclei (AGN), followed by astrometric filtering designed to remove stellar contaminants. Selecting a clean sample was favoured over including a higher number of extragalactic sources. For the final sample, the random and systematic errors in the proper motions are analysed, as well as the radio-optical offsets in position for sources in the third realisation of the International Celestial Reference Frame (ICRF3). Results. Gaia-CRF3 comprises about 1.6 million QSO-like sources, of which 1.2 million have five-parameter astrometric solutions in Gaia DR3 and 0.4 million have six-parameter solutions. The sources span the magnitude range G = 13-21 with a peak density at 20.6 mag, at which the typical positional uncertainty is about 1 mas. The proper motions show systematic errors on the level of 12 μas yr-1 on angular scales greater than 15 deg. For the 3142 optical counterparts of ICRF3 sources in the S/X frequency bands, the median offset from the radio positions is about 0.5 mas, but it exceeds 4 mas in either coordinate for 127 sources. We outline the future of Gaia-CRF in the next Gaia data releases. Appendices give further details on the external catalogues used, how to extract information about the Gaia-CRF3 sources, potential (Galactic) confusion sources, and the estimation of the spin and orientation of an astrometric solution

Gaia focused product release: radial velocity time series of long-period variables

Stars and planetary system

Relações metionina mais cistina digestível: lisina digestível em dietas suplementadas com ractopamina para suínos em terminação Digestible methionine plus cystine to digestible lysine ratio in diets supplemented with ractopamine for finishing pigs

O experimento foi realizado com o objetivo de determinar a relação metionina+cistina digestível:lisina digestível (met+cis:lis) para suínos machos castrados, selecionados geneticamente para deposição de carne magra na carcaça, sob suplementação com ractopamina (RAC) na fase de terminação. Foram utilizados 64 suínos com peso inicial de 84,68 ± 1,34 kg, distribuídos em delineamento experimental de blocos ao acaso. Os tratamentos consistiram de quatro dietas com relações de 0,54; 0,58; 0,62 e 0,66 de met+cis:lis suplementadas com RAC, oito repetições e dois animais por unidade experimental, durante um período de 28 dias. As relações met+cis:lis não influenciaram o consumo de ração, o ganho de peso diário, a conversão alimentar, a espessura de toucinho, a quantidade de carne magra, o peso da carcaça, a porcentagem de carne magra e o rendimento de carcaça dos suínos. As relações met+cis:lis influenciaram de forma quadrática as concentrações de colesterol total no lombo e de forma linear as concentrações de colesterol no toucinho. O menor teor de colesterol total foi observado nos suínos alimentados com a dieta com relação 0,66 met+cis:lis. Em suínos de 85 a 109 kg sob suplementação com ractopamina, a relação 0,54 met+cis:lis atende às exigências para melhor desempenho e melhores características de carcaça, enquanto, para menores níveis de colesterol no lombo e no toucinho, a relação é de 0,66 met+cis:lis.<br>The experiment was carried out to determine digestible methionine + cystine: digestible lysine (Met + Cys/Lys) ratio for barrows selected for deposition of lean meat in the carcass supplemented with ractopamine (RAC) in the finishing phase. Sixty-four barrows with 84.68 ± 1.34 kg BW was allotted to an experimental randomized block design, fed diets containing four Met + Cys/Lys ratio (0.54, 0.58, 0.62 and 0.66) supplemented with ractopamine, eight replications, during a period of 28 days. Met + Cys/Lys did not affect feed intake, average daily gain, feed conversion, fat thickness, lean meat amount, carcass weight, lean meat percentage and carcass yield of pigs. Met + Cys/Lys ratio influence quadraticaly the concentrations of total cholesterol in the loin and linearly the cholesterol concentrations in the subcutaneous fat. The lowest levels of total cholesterol were observed in pigs fed diet with 0.66 Met + Cys/Lys ratio. In pigs from 85 to 109 kg supplemented with ractopamine, the 0.54 Met + Cys/Lys ratio meets the requirement for better performance and better carcass traits, while to lower the cholesterol levels in the loin and subcutaneous fat the requirement is 0.66 Met + Cys/Lys ratio

Assessing costs of carrying geolocators using feather corticosterone in two species of aerial insectivores

Despite benefits of using light-sensitive geolocators to track animal movements and describe patterns of migratory connectivity, concerns have been raised about negative effects of these devices, particularly in small species of aerial insectivore.Geolocators may act as handicaps that increase energetic expenditure, which could explain reported effects of geolocators on survival.We tested this \u2018Energetic Expenditure Hypothesis\u2019 in 12 populations of tree swallows (Tachycineta bicolor) and barn swallows (Hirundo rustica) from North America and Europe, usingmeasurements of corticosterone from feathers (CORTf) grown after deployment of geolocators as a measure of physiology relevant to energetics. Contrary to predictions, neither among- (both species) nor within-individual (tree swallows only) levels of CORTf differed with respect to instrumentation. Thus, to the extent that CORTf reflects energetic expenditure, geolocators apparently were not a strong handicap for birds that returned post-deployment. While this physiological evidence suggests that information about migration obtained from returning geolocator-equipped swallows is unbiased with regard to levels of stress, we cannot discount the possibility that corticosterone played a role in reported effects of geolocators on survival in birds, and suggest that future studies relate corticosterone to antecedent factors, such as reproductive history, and to downstream fitness costs

Pregnancy and its role in breast cancer

Abstract Early full-term pregnancy is the only recognized factor able to prevent breast cancer. There are several hypotheses to explain the mechanisms of this protection, namely an altered hormonal milieu, a differentiation process or a switch in stem cell properties. To explore them, authors have been using animal models, mainly in rodents. Hormonal administration with estrogen and progesterone was the most widely used process to mimic the mammary changes during pregnancy. We have recently proposed that this enigmatic protective role of a full-term birth in breast cancer is carried out by tumor inhibition mediated by differentiated mammary epithelial cells. This explanation may give a new perspective of breast cancer prevention and treatment