Search

Tropical peatlands cycle and store large amounts of carbon in their soil and biomass1–5. Climate and land-use change alters greenhouse gas (GHG) fluxes of tropical peatlands, but the magnitude of these changes remains highly uncertain6–19. Here we measure net ecosystem exchanges of carbon dioxide, methane and soil nitrous oxide fluxes between October 2016 and May 2022 from Acacia crassicarpaplantation, degraded forest and intact forest within the same peat landscape, representing land-cover-change trajectories in Sumatra, Indonesia. This allows us to present a full plantation rotation GHG flux balance in a fibre wood plantation on peatland. We find that the Acaciaplantation has lower GHG emissions than the degraded site with a similar average groundwater level (GWL), despite more intensive land use. The GHG emissions from the Acaciaplantation over a full plantation rotation (35.2 ± 4.7 tCO2-eq ha−1year−1, average ± standard deviation) were around two times higher than those from the intact forest (20.3 ± 3.7 tCO2-eq ha−1year−1), but only half of the current Intergovernmental Panel on Climate Change (IPCC) Tier 1 emission factor (EF)20for this land use. Our results can help to reduce the uncertainty in GHG emissions estimates, provide an estimate of the impact of land-use change on tropical peat and develop science-based peatland management practices as nature-based climate solutions.

Global peatlands store more carbon than is naturally present in the atmosphere1,2. However, many peatlands are under pressure from drainage-based agriculture, plantation development and fire, with the equivalent of around 3 per cent of all anthropogenic greenhouse gases emitted from drained peatland3–5. Efforts to curb such emissions are intensifying through the conservation of undrained peatlands and re-wetting of drained systems6. Here we report eddy covariance data for carbon dioxide from 16 locations and static chamber measurements for methane from 41 locations in the UK and Ireland. We combine these with published data from sites across all major peatland biomes. We find that the mean annual effective water table depth (WTDe; that is, the average depth of the aerated peat layer) overrides all other ecosystem- and management-related controls on greenhouse gas fluxes. We estimate that every 10 centimetres of reduction in WTDecould reduce the net warming impact of CO2and CH4emissions (100-year global warming potentials) by the equivalent of at least 3 tonnes of CO2per hectare per year, until WTDeis less than 30 centimetres. Raising water levels further would continue to have a net cooling effect until WTDeis within 10 centimetres of the surface. Our results suggest that greenhouse gas emissions from peatlands drained for agriculture could be greatly reduced without necessarily halting their productive use. Halving WTDein all drained agricultural peatlands, for example, could reduce emissions by the equivalent of over 1 per cent of global anthropogenic emissions.

Terrestrial ecosystems remove about 30 per cent of the carbon dioxide (CO2) emitted by human activities each year1, yet the persistence of this carbon sink depends partly on how plant biomass and soil organic carbon (SOC) stocks respond to future increases in atmospheric CO2(refs. 2,3). Although plant biomass often increases in elevated CO2(eCO2) experiments4–6, SOC has been observed to increase, remain unchanged or even decline7. The mechanisms that drive this variation across experiments remain poorly understood, creating uncertainty in climate projections8,9. Here we synthesized data from 108 eCO2experiments and found that the effect of eCO2on SOC stocks is best explained by a negative relationship with plant biomass: when plant biomass is strongly stimulated by eCO2, SOC storage declines; conversely, when biomass is weakly stimulated, SOC storage increases. This trade-off appears to be related to plant nutrient acquisition, in which plants increase their biomass by mining the soil for nutrients, which decreases SOC storage. We found that, overall, SOC stocks increase with eCO2in grasslands (8 ± 2 per cent) but not in forests (0 ± 2 per cent), even though plant biomass in grasslands increase less (9 ± 3 per cent) than in forests (23 ± 2 per cent). Ecosystem models do not reproduce this trade-off, which implies that projections of SOC may need to be revised.

An X-ray survey of three high-energy γ-ray sources in the galactic anticentre region has been conducted using the large area sky survey (LASS) instrument on HEAO 1. The sensitivity of this survey ≲0.5 Uhuru flux units (UFU) is the highest yet reported. Although we do not confirm the recently published detection1of an X-ray source associated with γ195 + 5 (CG195+4); we report the detection of two, and possibly three, other X-ray sources found in its vicinity. Other than the supernova remnant, IC443, no other discrete X-ray sources have been detected near CG189+1, but there is evidence for diffuse emission or emission from unresolved sources in its vicinity. Three new X-ray sources have been discovered within a few degrees of CG176−7, but none overlaps the γ-ray error box. These results demonstrate that γ-ray sources like CG195+4 and CG176−7 have emission characteristics significantly different from the Crab pulsar, but may be similar to the Vela pulsar. Alternatively, the lack of a detectable X-ray flux suggests that the γ-ray emission arises from cosmic-ray interactions in dense interstellar clouds. An interesting feature of the new X-ray sources detected in this survey is that four of them may be associated with early-type stars which exhibit emission lines.

Consideration of the epidemiological evidence on radiogenic lung cancer in uranium miners and of the incidence of the disease generally leads to an upper estimate for the lifetime risk of 10−4cases per working level month for members of the general population.

Since the discovery of the intense bursts of γrays by Klebesadel et al.1in 1973, little progress has been made in the identification of the sources of the bursts. The initial observations provided directions to several sources with sufficient accuracy to establish the approximate isotropic distribution of the sources2, but not to provide a basis for association with any known objects, γ-ray burst astronomy entered a new phase in 1976 with the launch of Helios 2 and Solrad 11 containing the first experiments designed expressly for that purpose3,4. It then became possible to derive several error boxes that were very narrow in one dimension3,5. Using these data it was determined that the bursts are not associated with any type of object that has previously been recognized as a high energy astrophysical source—for example, X-ray sources. In 1978 a true interplanetary network of burst detectors was established with the launch of instruments on Pioneer Venus Orbiter6, ISEE 37–9and Venera 11 and 1210,11. With baseline separations that can exceed 1 AU, this network provides a basis for the location of the γburst sources with an accuracy sufficient for optical identifications. We briefly describe here one of these instruments, a joint Berkeley/Los Alamos experiment on the ISEE 3 spacecraft, and present some initial results from that experiment. These results are currently being combined with those from the other experiments to obtain accurate burst locations to be reported elsewhere.

THE large area survey instrument on HEAO 1 has observed that the galactic X-ray source GX339–4 (4U1658–48) varies on time scales from tens of milliseconds to hundreds of days. Its long term variability was known from measurements made by OSO 71and by Uhuru2but this is the first observation of aperiodic variability on time scales of tens of milliseconds to a few seconds. We show here that the overall characteristics of GX339–4 place it in the same class of X-ray sources as Cyg X–1 (ref. 3 summarises Cyg X–1) and Cir X–12,4–6

OCTOPAMINE, a biogenic amine, occurs widely in the nervous systems of vertebrates and invertebrates1–3. It has been found in single neurones in the central nervous system of the marine mollusc, Aplysia4and also in peripheral neurosecretory neurones in the lobster5,6from which a calcium-dependent release of octopamine has been demonstrated7,8. Specific octopamine receptors9and octopamine activated adenylate cyclases10have also been found in invertebrate nervous tissue. This has led to the suggestion of a neurotransmitter role for octopamine in invertebrates1,3. In the absence, however, of an example in which the effect of stimulating an identified octopamine containing neurone on its identified target or end organ is known, the true function of octopamine remains obscure. This paper aims to demonstrate that octopamine is the neurotransmitter of a single identified neurone in the locust Schistocerca americana gregaria. This neurone, which is shown to contain octopamine, innervates a muscle where it functions as a neuromodulator by potentiating the synaptic potential and tension produced by an identified motoneurone. That this function is mediated by the release of octopamine on stimulation is supported by the action of exogenously applied octopamine.

The formamidines are a structurally novel group of pesticides of growing importance in the control of mites, cattle ticks and certain orders of insects which have become resistant to conventional acaricides and insecticides. Their mode of action is complex with dose-dependent lethal and sublethal effects1–3. At sublethal levels they cause behavioural changes in the target pest species (for example in feeding and in mating behaviours), changes which are responsible for the protective effects on crops and livestock. Although many suggestions have been made for the underlying biochemical mechanism, including inhibition of monoamine oxidase activity, uncoupling of respiration and blockade of neuromuscular transmission1, no direct evidence has been presented. Another possibility is interaction with octopamine receptors in the central nervous system2,4,5. We report here that the formamidine acaricide/insecticide, chlordimeform (CDM), and its demethylated derivative can mimic the actions of octopamine at the locust neuromuscular junction. This gives the clearest evidence to date of the site of action of the formamidines and indicates a novel mode of action for these pesticides.

An unusual γ-ray burst event was observed on 5 March 1979 by nine different spacecraft1–5. The position of the event has been accurately determined1,2as α = 5h 25.95 min, δ = −66°07.1′ (epoch 1950.0), coincident with the location of the supernova remnant N49 in the Large Magellanic Cloud. The burst was of very high intensity, and if isotropic and located at the distance (∼55 kpc) of N49 had a peak luminosity of >1044erg s−1. Even more interesting is the obvious 8-s periodicity3–5of the event, following the initial very intense outburst. We report here the time history and power spectrum of this event as determined from the Pioneer Venus Orbiter (PVO) data.

A quiescent X-ray source detected with the Einstein X-ray Observatory in a location consistent with that of an intense γ-ray burst1–3is shown here to be also consistent with the location of the 1928 optical transient4, the likely optical counterpart of the γ-ray burst source GBS0117 – 29. The probable maximum X-ray luminosity is only ∼1031erg s−1and supports the hypothesis that either γ bursts are produced by accretion instabilities5,6or, if due to published models for a thermonuclear flash7, they recur with intervals \[gsims]50 yr. Such long recurrence times may be inconsistent with limits inferred from both the γ burst observations8and optical data4.

WE present here temporal and 0.2–2 MeV spectral data from two γ bursts observed on 12 June and 16 August 1976, by detectors on the Solrad 11A and 11B satellites. The 12 June burst showed evidence for structure on time scales down to ∼ 10 ms throughout its lifetime, whereas the 16 August burst varied only with characteristic times longer than a few tenths of a second. A search for both slow and fast spectral variability gave negative results. Accurate absolute burst times are, however, not yet available, but since both bursts were also observed by at least one Vela satellite, positions are calculable and will be reported.

The γ burst1of 5 March 1979 was observed by nine experiments2–6widely spaced on an interplanetary scale allowing an accurate position for a γ-burst source to be determined2,6for the first time. Spectral observations in the range 50–1,000 keV had sufficient time resolution to resolve spectral changes within the main burst. Early in the main burst, the typical photon energies declined from a spectrum similar to a 30 keV black body to that of a ∼26 keV black body. Thereafter, at the shoulder on the main burst the spectrum became harder (KT ∼31 keV). The γ burst apparently triggered an X-ray pulsar with a period of ∼8.0 s (refs 3–5,7) and with a softer spectrum (KT ≃ 12 keV). We show here that, although the source is probably a neutron star with an obliquely rotating magnetic field, simple cooling of residual hot spots does not completely explain the pulsations.

Absorption features near 40 keV in the spectra of several gamma-ray burst sources, first reported by Mazets et al., have been widely ascribed to cyclotron absorption, implying that a strongly magnetized neutron star is the cause of the bursts. Most interpretations of the spectra have been hampered by instrumental limitations: the absorption features are usually at the lower end of the energy range covered by the detector, making spectral unfolding unreliable. Here we report new observations by the gamma-ray burst detector on board the Ginga satellite, which has two well-calibrated detectors covering a wide energy range, 1.5 to 375 keV. The spectral features we find are consistent with first and second cyclotron harmonics, which we take as strong evidence for the magnetized neutron star model.

MAY I ask the hospitality of the columns of NATURE for an appeal to men of science throughout the world ?

PREVIOUS investigations have shown that gas–solid chromatography (GSC) on activated alumina is useful in separating paraffins and olefines from C1−C8(refs. 1–3). The physicochemical characteristics of the solute and its affinity for the adsorbent determine the efficiency and limitations of alumina GSC. The choice of carrier gas for adsorption chromatography has a marked effect on retention times and column efficiencies4. Solute characteristics that influence the degree of separation attained include differences in boiling points, molecular branching, and the presence of double and triple bonds.

A MULTICOMPONENT mixture of saturated and unsaturated hydrocarbons has been successfully separated on a single gas–solid chromatographic (GSC) column of activated alumina. This separation is remarkable when the extreme boiling-point range (−88.3° to +125.8° C) of the respective components is considered.

AFTER the ill-fated Scott expedition of 1910–13 a valuable suite of Antarctic rocks, collected by Sir Raymond Priestley, was donated to the University of Nottingham. In it was a specimen from the Beacon Sandstone series collected from Cape Royds. This we have investigated to see whether such a series might conceivably possess the properties of reservoir or source rocks for oil.

SEPARATION of oxygen, nitrogen and carbon dioxide by gas–solid chromatography has been accomplished on multiple columns of different adsorbents1,2. Greene et al.3almost achieved this separation on activated charcoal, but resolution of oxygen and nitrogen with this adsorbent was incomplete.

THE need to scan chromatographically the composition of natural oils and bacteriostatic extracts from rocks under precisely similar solvent-extraction conditions has led to the use of filter papers folded into cones. Many other fields of research require similar conditions, and it is suggested that this type of paper chromatography may have wider applications. From Fig. 1 it will be seen how simple is the equipment needed for this technique. Moreover, the apparatus enables one to obtain a solvent-saturated atmosphere very rapidly and even to work at reduced pressures. As a result of this the developing solvent rises rapidly, and at a remarkably uniform rate, so that the ingredients separate effectively into ever-narrowing zones as they ascend towards the apex of the cone (Fig. 2). These features of the technique have also proved particularly useful in concentrating antibacterial ingredients extracted from coal. The ever-narrowing front of the ascending column of ingredients results in the development of highly concentrated zones of the bacteriostatic substances, collectively known as ‘vitricin’1.