ALBERT

Description: Industrial emissions play a major role in the global methane budget. The Permian basin is thought to be responsible for almost half of the methane emissions from all U.S. oil- and gas-producing regions, but little is known about individual contributors, a prerequisite for mitigation. We use a new class of satellite measurements acquired during several days in 2019 and 2020 to perform the first regional-scale and high-resolution survey of methane sources in the Permian. We find an unexpectedly large number of extreme point sources (37 plumes with emission rates 〉500 kg hour−1), which account for a range between 31 and 53% of the estimated emissions in the sampled area. Our analysis reveals that new facilities are major emitters in the area, often due to inefficient flaring operations (20% of detections). These results put current practices into question and are relevant to guide emission reduction efforts.

Description: One of the most fundamental questions in ecology is how many species inhabit the Earth. However, due to massive logistical and financial challenges and taxonomic difficulties connected to the species concept definition, the global numbers of species, including those of important and well-studied life forms such as trees, still remain largely unknown. Here, based on global ground-sourced data, we estimate the total tree species richness at global, continental, and biome levels. Our results indicate that there are ∼73,000 tree species globally, among which ∼9,000 tree species are yet to be discovered. Roughly 40% of undiscovered tree species are in South America. Moreover, almost one-third of all tree species to be discovered may be rare, with very low populations and limited spatial distribution (likely in remote tropical lowlands and mountains). These findings highlight the vulnerability of global forest biodiversity to anthropogenic changes in land use and climate, which disproportionately threaten rare species and thus, global tree richness.

Description: Over the past decade, several global maps of above-ground biomass (AGB) have been produced, but they exhibit significant differences that reduce their value for climate and carbon cycle modelling, and also for national estimates of forest carbon stocks and their changes. The number of such maps is anticipated to increase because of new satellite missions dedicated to measuring AGB. Objective and consistent methods to estimate the accuracy and uncertainty of AGB maps are therefore urgently needed. This paper develops and demonstrates a framework aimed at achieving this. The framework provides a means to compare AGB maps with AGB estimates from a global collection of National Forest Inventories and research plots that accounts for the uncertainty of plot AGB errors. This uncertainty depends strongly on plot size, and is dominated by the combined errors from tree measurements and allometric models (inter-quartile range of their standard deviation (SD) = 30–151 Mg ha−1). Estimates of sampling errors are also important, especially in the most common case where plots are smaller than map pixels (SD = 16–44 Mg ha−1). Plot uncertainty estimates are used to calculate the minimum-variance linear unbiased estimates of the mean forest AGB when averaged to 0.1∘. These are used to assess four AGB maps: Baccini (2000), GEOCARBON (2008), GlobBiomass (2010) and CCI Biomass (2017). Map bias, estimated using the differences between the plot and 0.1∘ map averages, is modelled using random forest regression driven by variables shown to affect the map estimates. The bias model is particularly sensitive to the map estimate of AGB and tree cover, and exhibits strong regional biases. Variograms indicate that AGB map errors have map-specific spatial correlation up to a range of 50–104 km, which increases the variance of spatially aggregated AGB map estimates compared to when pixel errors are independent. After bias adjustment, total pantropical AGB and its associated SD are derived for the four map epochs. This total becomes closer to the value estimated by the Forest Resources Assessment after every epoch and shows a similar decrease. The framework is applicable to both local and global-scale analysis, and is available at https://github.com/arnanaraza/PlotToMap. Our study therefore constitutes a major step towards improved AGB map validation and improvement.

Description: Planted forests are critical to climate change mitigation and constitute a major supplier of timber/non-timber products and other ecosystem services. Globally, approximately 36% of planted forest area is located in East Asia. However, reliable records of the geographic distribution and tree species composition of these planted forests remain very limited. Here, based on extensive in situ and remote sensing data, as well as an ensemble modeling approach, we present the first spatial database of planted forests for East Asia, which consists of maps of the geographic distribution of planted forests and associated dominant tree genera. Of the predicted planted forest areas in East Asia (948,863 km2), China contributed 87%, most of which is located in the lowland tropical/subtropical regions, and Sichuan Basin. With 95% accuracy and an F1 score of 0.77, our spatially-continuous maps of planted forests enable accurate quantification of the role of planted forests in climate change mitigation. Our findings inform effective decision-making in forest conservation, management, and global restoration projects.

Description: Possible mode conversion from kinetic Alfvén wave to modified electron acoustic wave is examined based on a multi-fluid model involving two electron populations. The mode conversion transpires when a kinetic Alfvén wave propagates through a transition between a hot-electron-dominant region and a cold-electron-dominant region. It is shown that the mode conversion and the kinetic Alfvén wave reflection depend strongly on the hot electron inertial length, the hot electron temperature, and the perpendicular wavelength. The results suggest that such conversion is ubiquitous whenever a steep gradient of electron temperature exists, for example, in the planetary auroral acceleration regions or at the boundary of the solar corona.

Description: The evolution of the local stress field of faults under tectonic stresses is crucial to predict earthquakes. In this study, we investigated the stress sensitivity of an analogue fault model with dimensions of 2 m × 1 m × 1 m, prepared from cement, gypsum, river sand, putty powder, and borax mixture. The angle between the fault strike and the maximum stress direction was varied, and the variation in the stress near the analogue fault (area 1200 × 400 mm; width 5 mm) was determined. The crack growth law of the analogue fault was found to be consistent with a simple Riedel shear model. A main strike-displacement zone was formed, and its direction was parallel to that of the analogue fault. Fault development was described by three stages based on stress–strain relationships: a nucleus stage, a stable growth, and an unstable growth stage. The deflection angle (the deflection angle of the local principal stresses) range of the local stress field was (− 45°, 45°), and it varied most significantly in the nucleus stage. The closer to the fault, the greater the variation range in the deflection angle. The variation range was greater in the fault compression quadrants than in the dilatation quadrants. The correlation between the deflection angle and the relative deformation velocity of the fault was stronger in the stable growth stage than in the other stages. In this stage, the angle–deformation–velocity correlation could be well fitted using a logistic trend model. These findings can be of importance to better understand the nucleation and mechanisms of fault slip-induced earthquakes under varying fault-strike-stress conditions.

Description: Correction to: Rock Mechanics and Rock Engineering https://doi.org/10.1007/s00603-023-03714-4 In the original publication, the “Funding Information” and “Acknowledgements” were mistakenly swapped.