Identification of typical eco-hydrological behaviours using InSAR allows landscape-scale mapping of peatland condition

Better tools for rapid and reliable assessment of global peatland extent and condition are urgently needed to support action to prevent their further decline. Peatland surface motion is a response to changes in the water and gas content of a peat body regulated by the ecology and hydrology of a peatland system. Surface motion is therefore a sensitive measure of ecohydrological condition but has traditionally been impossible to measure at the landscape scale. Here we examine the potential of surface motion metrics derived from InSAR satellite radar to map peatland condition in a blanket bog landscape. We show that the timing of maximum seasonal swelling of the peat is characterized by a bimodal distribution. The first maximum is typical of steeper topographic gradients, peatland margins, degraded peatland and more often associated with ‘shrub’-dominated vegetation communities. The second maximum is typically associated with low topographic gradients often featuring pool systems, and Sphagnum dominated vegetation communities. Specific conditions associated with ‘Sphagnum’ and ‘shrub’ communities are also determined by the amplitude of swelling and average multiannual motion. Peatland restoration currently follows a re-wetting strategy, however our approach highlights that landscape setting appears to determine the optimal endpoint for restoration. Aligning expectation for restoration outcomes with landscape setting might optimise peatland stability and carbon storage. Importantly, deployment of this approach, based on surface motion dynamics, could support peatland mapping and management on a global scale.

Assessing soil redistribution of forest and cropland sites in wet tropical Africa using ^239+240Pufallout radionuclides

Due to the rapidly growing population in tropical Africa, a substantial rise in food demand is predicted in upcoming decades, which will result in higher pressure on soil resources. However, there is limited knowledge on soil redistribution dynamics following land conversion into arable land in tropical Africa that is partly caused by infrastructure limitations for long-term landscape-scale monitoring. In this study, fallout radionuclides 239+240Pu are used to assess soil redistribution along topographic gradients at two cropland sites and at three nearby pristine forest sites located in the DR Congo, Uganda and Rwanda. In the study area, a 239+240Pu baseline inventory is found that is higher than typically expected for tropical regions (mean forest inventory 41 Bq m−2). Pristine forests show no indication of soil redistribution based on 239+240Pu along topographical gradients. In contrast, soil erosion and sedimentation on cropland reached up to 37 cm (81 Mg ha−1 yr−1) and 40 cm (87 Mg ha−1 yr−1) within the last 55 years, respectively. Cropland sites show high intra-slope variability with locations showing severe soil erosion located in direct proximity to sedimentation sites. This study shows the applicability of a valuable method to assess tropical soil redistribution and provides insight into soil degradation rates and patterns in one of the most socio-economically and ecologically vulnerable regions of the world.

Atypical neural topographies underpin dysfunctional pattern separation in temporal lobe epilepsy

Episodic memory is the ability to accurately remember events from our past. The process of pattern separation is hypothesized to underpin this ability and is defined as the ability to orthogonalize memory traces, to maximize the features that make them unique. Contemporary cognitive neuroscience suggests that pattern separation entails complex interactions between the hippocampus and the neocortex, where specific hippocampal subregions shape neural reinstatement in the neocortex. To test this hypothesis, the current work studied both healthy controls and patients with temporal lobe epilepsy (TLE) who present with hippocampal structural anomalies. In all participants, we measured neural activity using functional magnetic resonance imaging (fMRI) while they retrieved memorized items compared to lure items which share features with the target. Behaviorally, TLE patients were less able to exclude lures than controls, and showed a reduction in pattern separation. To assess the hypothesized relationship between neural patterns in the hippocampus and the neocortex, we identified topographic gradients of intrinsic connectivity along neocortical and hippocampal subfield surfaces and identified the topographic profile of the neural activity accompanying pattern separation. In healthy controls, pattern separation followed a graded pattern of neural activity, both along the hippocampal long axis (and peaked in anterior segments that are more heavily engaged in transmodal processing) and along the neocortical hierarchy running from unimodal to transmodal regions (peaking in transmodal default mode regions). In TLE patients, however, this concordance between task-based functional activations and topographic gradients was markedly reduced. Furthermore, person specific measures of concordance between task-related activity and connectivity gradients in patients and controls related to inter-individual differences in behavioral measures of pattern separation and episodic memory, highlighting the functional relevance of the observed topographic motifs. Our work is consistent with an emerging understanding that successful discrimination between memories with similar features entails a shift in the locus of neural activity away from sensory systems, a pattern that is mirrored along the hippocampal long axis and with respect to neocortical hierarchies. More broadly, our study establishes topographic profiling using intrinsic connectivity gradients captures the functional underpinnings of episodic memory processes in manner that is sensitive to their reorganization in pathology.

Hydrodynamic modelling of outburst flood hazard in the Pokhara Valley, Nepal

<p>In May 2012, a sudden outburst flood along the Seti Khola river caused 72 fatalities and damaged infrastructure in the northern Pokhara Valley, Nepal. This destructive event raised concerns about possible future landslide- or glacier-surge-related outburst floods from the Higher Himalayas. The Seti Khola runs along one of the steepest topographic gradients in this mountain belt. The river is fed by the debris-covered Sabche glacier, Nepal’s only observed surging glacier, below the flanks of Annapurna III (c. 7500 m asl) and reaches Pokhara, the country’s second largest city, at about 850 m asl. Over a course of some 40 km, the Seti Khola shaped the Pokhara Valley’s distinctive landscape of unpaired, several tens of meters to >100-m high alluvial terraces that alternate with deep slot gorges of <1 km length, all mostly cut into deposits of medieval and earlier outburst and outwash deposits. These abrupt changes in channel cross section provide many potential locations of hydraulic ponding during floods. We present a reanalysis of the 2012 Seti Khola outburst flood, and combine field-based surveys of valley geometry, flood markers, and surface roughness (i.e. Manning’s n value estimates) with landform mapping from high-resolution satellite images and digital elevation models. These components form the input for a one-dimensional steady flow simulation in HEC-RAS that allows us to reconstruct the dynamics, stage height, and runout from the 2012 Seti Khola flood. Validated by both this recent and the catastrophic historic events, we use our model to simulate future scenarios of inundation by these infrequent but potentially highly destructive outburst floods and compare them to the Pokhara Valley’s recurring monsoonal floods.</p>

Explicit landslide characterization using high-resolution and multi-trajectory airborne UAVSAR data

<p>The spatial resolution and deformation-mapping capability of SAR remote sensing fit into the scope of scientific investigations of landslides that move slowly at millimeters to meters per year. The SAR technique has become an efficient tool to detect, monitor and characterize slow-moving landslides. However, north-south motions are nearly unresolvable for the present-day, spaceborne, polar-orbiting and side-looking Interferometric SAR (InSAR) line-of-sight (LOS) mapping systems, and unstable slopes may often not face favorable directions of SAR satellites. In addition, a complete 3D displacement field cannot be obtained with only two distinct InSAR LOS measurements from ascending and descending satellite orbits. Arbitrary assumptions such as simply no north-south motions or constraints imposed by topographic gradients can provide a quasi-3D displacement estimate, yet this is subject to large bias. The Uninhabited Aerial Vehicle SAR (UAVSAR) is an airborne SAR system deployed by NASA/JPL that can acquire measurements along user-specified flight paths. UAVSAR operates with an L-band wavelength (0.24 m) and the single-look pixel spacings along the azimuth and the range directions are as small as 0.6 m and 1.67 m, respectively. Here we will focus on the contributions of UAVSAR and satellite SAR systems to studying the Slumgullion landslide in Colorado, USA with persistent movements at 1-2 cm/day, and even slower-moving landslides (cm to m per year) in the San Francisco East Bay Hills and the Eel River catchment in California, USA. As a complement to InSAR LOS measurements, the high-resolution UAVSAR data and appreciable velocity at a level of m/yr (e.g., Slumgullion landslide and numerous Eel River landslides) make it possible to extract motions by tracking pixel offsets in both azimuth and LOS directions. The flexible trajectory of the aircraft and the additional information from UAVSAR’s sub-meter resolution and multiple flight trajectories allows for an optimal 3D displacement solution, which can be further used for quantitative analysis of the formation of morphological structures, landslide-fault interactions, inferring rheology, understanding slope channel modulation, and capturing the spatiotemporally dependent sensitivity to hydroclimatic variability. New knowledge gained on the precipitation thresholds, landslide volume, and the identification of potential nucleation zones of slope failures will directly assist landslide hazard mitigation and reduction.</p>

Short-term occupations at high elevation during the Middle Paleolithic at Kalavan 2 (Republic of Armenia)

The Armenian highlands encompasses rugged and environmentally diverse landscapes and is characterized by a mosaic of distinct ecological niches and large temperature gradients. Strong seasonal fluctuations in resource availability along topographic gradients likely prompted Pleistocene hominin groups to adapt by adjusting their mobility strategies. However, the role that elevated landscapes played in hunter-gatherer settlement systems during the Late Pleistocene (Middle Palaeolithic [MP]) remains poorly understood. At 1640 m above sea level, the MP site of Kalavan 2 (Armenia) is ideally positioned for testing hypotheses involving elevation-dependent seasonal mobility and subsistence strategies. Renewed excavations at Kalavan 2 exposed three main occupation horizons and ten additional low densities lithic and faunal assemblages. The results provide a new chronological, stratigraphical, and paleoenvironmental framework for hominin behaviors between ca. 60 to 45 ka. The evidence presented suggests that the stratified occupations at Kalavan 2 locale were repeated ephemerally most likely related to hunting in a high-elevation within the mountainous steppe landscape.

Assessing soil erosion of forest and cropland sites in wet tropical Africa using ^239+240Pu fallout radionuclides

Due to the rapidly growing population in tropical Africa, a substantial rise in food demand is predicted in upcoming decades, which will result in higher pressure on soil resources. However, there is limited knowledge on soil redistribution dynamics following land conversion to arable land in tropical Africa that is partly caused by challenging local conditions for long-term landscape scale monitoring. In this study, fallout radionuclides 239+240Pu are used to assess soil redistribution along topographic gradients at two cropland sites and at three nearby pristine forest sites located in the DR Congo, Uganda and Rwanda. In the study area, a relatively high 239+240Pu baseline inventory is found (mean forest inventory 41 Bq m−2). Pristine forests show no indication for soil redistribution based on 239+240Pu along topographical gradients. In contrast, soil erosion and sedimentation on cropland reached up to 37 and 40 cm within the last 55 years, respectively. Cropland sites show high intra-slope variability with locations showing severe soil erosion located in direct proximity to sedimentation sites. This study shows the applicability of a valuable method to assess tropical soil redistribution and provides insight on soil degradation rates and patterns in one of the most vulnerable regions of the World.

Topographic gradients of intrinsic dynamics across neocortex

The intrinsic dynamics of neuronal populations are shaped by both microscale attributes and macroscale connectome architecture. Here we comprehensively characterize the rich temporal patterns of neural activity throughout the human brain. Applying massive temporal feature extraction to regional haemodynamic activity, we systematically estimate over 6000 statistical properties of individual brain regions’ time-series across the neocortex. We identify two robust spatial gradients of intrinsic dynamics, one spanning a ventromedial-dorsolateral axis and dominated by measures of signal autocorrelation, and the other spanning a unimodal-transmodal axis and dominated by measures of dynamic range. These gradients reflect spatial patterns of gene expression, intracortical myelin and cortical thickness, as well as structural and functional network embedding. Importantly, these gradients are correlated with patterns of meta-analytic functional activation, differentiating cognitive versus affective processing and sensory versus higher-order cognitive processing. Altogether, these findings demonstrate a link between microscale and macroscale architecture, intrinsic dynamics, and cognition.