Disturbance Intensity Research Articles

Sensitivity of Sentinel-1 Backscatter to Management-Related Disturbances in Temperate Forests

The rapid and accurate detection of forest disturbances in temperate forests has become increasingly crucial as policy demands and climate pressure on these forests rise. The cloud-penetrating Sentinel-1 radar constellation provides frequent and high-resolution observations with global coverage, but few studies have assessed its potential for mapping disturbances in temperate forests. This study investigated the sensitivity of temporally dense C-band backscatter data from Sentinel-1 to varying management-related disturbance intensities in temperate forests, and the influence of confounding factors such as radar backscatter signal seasonality, shadow, and layover on the radar backscatter signal at a pixel level. A unique network of 14 experimental sites in the Netherlands was used in which trees were removed to simulate different levels of management-related forest disturbances across a range of representative temperate forest species. Results from six years (2016–2022) of Sentinel-1 observations indicated that backscatter seasonality is dependent on species phenology and degree of canopy cover. The backscatter change magnitude was sensitive to medium- and high-severity disturbances, with radar layover having a stronger impact on the backscatter disturbance signal than radar shadow. Combining ascending and descending orbits and complementing polarizations compared to a single orbit or polarization was found to result in a 34% mean increase in disturbance detection sensitivity across all disturbance severities. This study underlines the importance of linking high-quality experimental ground-based data to dense satellite time series to improve future forest disturbance mapping. It suggests a key role for C-band backscatter time series in the rapid and accurate large-area monitoring of temperate forests and, in particular, the disturbances imposed by logging practices or tree mortality driven by climate change factors.

Assessment of ecosystem stability in the agro-pastoral transitional zone for local sustainable management: A case study in Duolun County, northern China

Assessing the ecosystem stability and the influencing factors in the fragile ecosystem of the agro-pastoral transitional zone of Northern China (APTZNC) is essential for the sustainable provision of multiple ecosystem services and adaptive ecosystem management. In this study, we selected Duolun County in the APTZNC as the study area. The ecosystem stability was assessed in terms of resistance and resilience, and the factors influencing the spatial distribution of stability were explored. The results showed that the mean value of ecosystem resistance in the study area was 0.61 (at a medium–high level), while the mean values of resilience and stability were 0.38 and 0.36, respectively, (at a medium–low level) in the past 21 years. The spatial patterns of ecosystem resistance, resilience, and stability showed significant spatial heterogeneity. Temperature and elevation were both negatively correlated with ecosystem resistance. At the same time, human activities and socioeconomics are the key factors which influence the distribution of stability indicators. The population density and gross domestic product show a correlation with stability, and the stability also varies across different land uses. Forest ecosystems showed high stability compared to croplands and grasslands when exposed to the same climate change perturbations; cropland ecosystems with a high intensity of human disturbance showed a loss of stability, while grassland ecosystems showed a gradual improvement in stability. These findings can provide effective information for sustainable management of different regions or ecosystem types in the context of climate change and intensified human activities.

Response of Soil Physicochemical Properties and Microbial Community Composition in Larix olgensis Plantations to Disturbance by a Large Outbreak of Bark Beetle

Forests are affected by a wide range of disturbances globally, resulting in the decline or death of large areas of them. There is a lack of comparative studies on how soil properties change in forests that die under the influence of disturbances, especially considering different levels of disturbance. For this study, we took Larix olgensis—a major plantation forest species in northeast China—as the research object, one in which a large outbreak of bark beetle led to large-scale forest death, and set up fixed sample plots characterized by different disturbance intensities. We investigated the responses of soil physicochemical properties and microbial community compositions to different disturbance intensities through the determination of soil nutrient indices and high-throughput sequencing. The results show that there were significant differences (p < 0.05) in the effects of different disturbance intensities on soil physicochemical properties, where the soil moisture content, total nitrogen, total carbon, and total phosphorus in the control group were significantly higher than those in the disturbed groups. The soil pH was highest under low-intensity disturbance and the soil total potassium content was highest under high-intensity disturbance. At different disturbance intensities, the highest soil moisture content was found in the high-intensity group. Proteobacteria, Actinobacteria, Verrucomicrobia, Acidobacteria, Candidatus_Rokubacteria, Chloroflexi, Gemmatimonadetes, and Thaumarchaeota were the dominant populations with higher abundances; meanwhile, the relative abundance of Bacteroidetes, Tenericutes, and a tentatively unclassified fungus differed significantly (p < 0.05) across disturbance intensities. Among the dominant microbial populations, Acidobacteria showed a significant negative correlation with soil pH and a significant positive correlation with total potassium content, Thaumarchaeota showed significant positive correlations with soil moisture content and total nitrogen content, and Firmicutes and Gemmatimonadetes showed significant negative correlations with total carbon content in the soil. Furthermore, soil total nitrogen content was the key factor driving changes in microbial communities. The results of this study provide a scientific basis for the study of the long-term effects of tree mortality caused by insect pests on soil microbial communities and their response mechanisms, which is of great theoretical value for the establishment of scientific and effective methods for woodland restoration.

Disturbance intensity shapes the soil micro-food web compositions and energy fluxes during seven-year land use changes

Soil micro-food webs play an important role in ecosystem functions through energy flow; they are strongly influenced by land use types. Previous studies have typically utilized the space-for-time substitution or single-time sampling method to reflect the land-use change effects by comparing differences among existing land-use types. These methods would increase random error. Research on how synchronized land-use change (starting at the same time and place) influences soil ecological processes and functions is urgently needed. Based on a controlled field experiment and seven years of observations, this study explored the effects of land-use change from natural shrubland to cropland (maize), forage land (tall-grass forage), and economic forest land (walnut plantation) on the community structure and energy dynamics of the soil micro-food webs. Cropland simplified the complexity of the soil food webs compared to the other three land-uses. Forage grassland maintained the highest biomasses of soil total microbes, fungi, and arbuscular mycorrhizal fungi. In addition, economic forest land improved the flow uniformity of the micro-food web by increasing energy transfer from resources to bacterivores, fungivores, and herbivores while decreasing herbivore energy flow to omnivores-predators. Omnivore abundance and nematode diversity were important predictors of total energy flux and flow uniformity of the soil micro-food webs, respectively. In addition, omnivores maintained the complexity of soil micro-food webs by promoting interactions among trophic groups through top-down control. Soil organisms are sensitive to the response of agricultural management and planting time, and it may take several years or more to reach a dynamic equilibrium. Different types and levels of ecosystem disturbance (e.g., tillage and no-tillage, fertilizer rates, aboveground biomass removal intensity) may be the major drivers of soil community during land use change. Our findings highlight the importance of conservation agriculture in maintaining soil food web structure and energy flow for future sustainable land uses, and that promoting omnivore abundance is essential for food web complexity and stability.

Promoting plant diversity and habitat heterogeneity through vineyard terracing

AbstractQuestionsViticulture on steep slopes has shaped the landscape and biodiversity in many regions, but insufficient profitability has led to management cessation and shrub encroachment. A solution to maintain economically viable cultivation could be vineyard terracing. We aimed to identify the potential of terracing to enhance plant diversity and habitat heterogeneity in vineyards, analyze effects of management intensity on vineyard vegetation, and assess how plant communities change after vineyard abandonment.LocationWine‐growing region of the Upper Middle Rhine Valley in Hesse (50.042342° N, 7.814533° E) and Rhineland‐Palatinate (50.119139° N, 7.719275° E), Germany.MethodsWe recorded vascular plant species and local vineyard parameters in vertically oriented vineyards with vegetated and tilled open inter‐rows, in terraced vineyards with tilled terrace inter‐rows and extensively managed embankments, and in vineyard fallows in a total of 45 study sites. We used plant species richness, Ellenberg indicator values and Grime's strategy types to describe how traits and ecological requirements respond to distinct vineyard management.ResultsPlant species richness and composition were determined by management‐derived disturbance intensities. Extensively managed embankments had a distinct plant community, the highest plant species richness, more perennial and indicator species, and lower nitrogen indicator values compared with inter‐rows. By contrast, highly disturbed open and terrace inter‐rows revealed plant communities associated with annuals and ruderals, but species richness did not differ between terrace inter‐rows and embankments. The plant communities of fallows were completely different with lower plant diversity.ConclusionsOur results highlight the potential of terraced vineyards for plant diversity with nutrient poor, extensively managed embankments providing conditions that have become rare in modern agricultural systems. A long environmental gradient from terrace inter‐rows to embankments created habitat heterogeneity within a narrow space. By contrast, intensive inter‐row management in vertically oriented vineyards hampers high plant diversity and abandonment fosters the spread of woody species at the expanse of plant diversity.

Quasi‐synchronization for complex networks under deception attacks via saturated impulsive control

AbstractThis paper addresses the issue of saturated impulsive control for a class of dynamical networks with hybrid delays and unknown bounded disturbances that are susceptible to deception attacks. Achieving local exponential quasi‐synchronization is the objective. Physical networks are often restricted by saturation, making them more vulnerable to cyberattacks that can disrupt network performance. Unlike previous studies on saturated impulsive control, this paper fully considers the effect of deception attacks on saturated impulse by proposing a new constraint of set inclusion. Criteria for the local quasi‐synchronization problem are established using the Lyapunov method and the comparison principle of impulsive systems. Our results demonstrate that the error bounds for quasi‐synchronization are closely linked to the impulsive interval, time‐delay, intensity of external disturbances, and deception attacks. Finally, numerical simulations are conducted to validate the effectiveness of our proposed approach.

Manic episode with psychotic symptoms in a patient with Pseudologia Fantastica of years of evolution. A case report

Introduction Pseudologia Fantastica (PF) also called “mythomania” is a disorder centred on the tendency of the sufferer to distort reality through constant lies. These patients find it difficult to moderate their sense of self and their self-esteem. Therefore, they display significant grandiosity, which seems to defend them from intense psychological disturbance, pretending to counteract deep feelings of unworthiness, emptiness and alienation.Notable characteristics include: normal or above average IQ, absence of formal thought disorder, poor sense of identity, poor sexual adjustment, low frustration tolerance, strong dependency needs and narcissism. The phenomenon of “imposture” (the person’s claim of achievement or having connections to famous or influential people) is frequent. The patient’s history often shows that one or both parents were experienced as rejecting figures. They are more likely to be involved in legal problems and 20% receive some form of psychiatric treatment.The aetiology and pathogenesis of this disorder requires consideration of developmental disturbances, personal history and current life stressors.ObjectivesA case of a patient with PF is presented followed by a theoretical review on the topic.MethodsA case is presented with a bibliographic review.Results We admitted a 47-year-old man to the Acute Hospitalisation Unit for a suspected “psychotic episode with clinical mania”. He presented manic and psychotic symptoms, with delusional ideation of months of evolution, megalomaniacal and fantastic discourse, centred on his work with high-ranking government officials and other implausible events. Multiple academic, work and personal life failures, with a diagnosis of depression 15 years earlier.During admission, he constantly confirms his history. He tends to present a rationalising discourse and a minimising attitude towards behavioural alterations. He appears cooperative and docile at certain times, while at others he is irritable, complaining and threatening.As for medication, olanzapine was initially prescribed at a dose of 20 mg per day, which was reduced to 10 mg given the psychopathological improvement and the difficulties of adherence.On discharge, the presumptive diagnosis was “delusional disorder and probable personality disorder with narcissistic traits, with a history of PF, which in recent months has presented a manic episode with psychotic symptoms”.ConclusionsTheir management poses challenges in terms of engaging with treatment and building a therapeutic alliance. It is important to assess the social and legal implications. Ensuring that they have stable relationships and adequate social supports is essential for successful treatment. Further exploration and research into this disorder is needed to better understand its manifestations and psychiatric consequences.Disclosure of InterestNone Declared

Observations of Mesospheric Gravity Waves Generated by Geomagnetic Activity

AbstractGravity waves (GWs) play an important role in the dynamics and energetics of the mesosphere. Geomagnetic activity is a known source of GWs in the upper atmosphere. However, how deep the effects of geomagnetic activity induced GWs penetrate into the mesosphere remains an open question. We use temperature measurements from the SABER/TIMED instrument between 2002 and 2018 to study the variations of mesospheric GW activity following intense geomagnetic disturbances identified by AE and Dst indices. By considering several case studies, we show for the first time that the GWs forced by geomagnetic activity can propagate down to about 80 km in the high latitude mesosphere. Only regions above 55° latitudes show a clear response. The fraction of cases in which there is an unambiguous enhancement in GW activity following the onset of geomagnetic disturbance is smaller during summer than other seasons. Only about half of the events show an unambiguous increase in GW activity during non‐summer periods and about one quarter of the events in summer show an enhancement in GWs. In addition, we also find that the high latitude mesopause is often seen to descend in altitude following onset of geomagnetic activity in the non‐summer high latitude region.

基于EDEM软件的气压式精量排种器充种性能模拟与试验

In order to study the effect of population disturbance on the filling performance of the seed metering device, this paper uses the pneumatic precision seed metering device as the model, and uses EDEM software to simulate the population movement of three different seed metering devices. The bench test was carried out at different pressures at 12 km/h and at different speeds at 3.5 kPa. The results show that the designed seed disk with grooves has the most intense disturbance and the highest qualified rate. In order to verify the performance of the disk, full factor tests are carried out on the air pressure and speed, The test results show that when the operating speed is 10~12 km/h and the positive pressure is 3~3.5 kPa, the leakage rate is no higher than 5.42%, the replay rate is no higher than 0.42%, and the qualified rate is no lower than 94.58%. When the operating speed is 14 ~ 16 km/h and the positive pressure is 3.5~4 kPa, the leakage rate is not higher than 6.7%, the replay rate is not higher than 1.04%, and the pass rate is not lower than 93.12%. All the indicators are better than the national standard.

Effect of Forest Fires on the Alpha and Beta Diversity of Soil Bacteria in Taiga Forests: Proliferation of Rare Species as Successional Pioneers

Forest fires are among the most influential drivers of changes in forest soil bacterial diversity. Nevertheless, little is known regarding the effects of forest fires on maintaining the complex interactions that preserve forest ecosystem stability. Therefore, this study characterized alterations in soil bacterial community composition and diversity within taiga forests subjected to varying disturbance intensities. Particularly, this study examined the bacterial community within a Larix gmelinii fire-burnt site in Daxinganling, analyzing the changes in bacterial community structure and function across light, moderate, and heavy fire-burnt sites, as well as a control sample site, utilizing Illumina MiSeq technology. Through an assessment of bacterial community diversity and soil physicochemical properties (moisture content (MC), pH, microbial biomass carbon (MBC), organic carbon (SOC), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), and available potassium (AP)), we explored the influence of the soil microenvironment on the soil bacterial community structure at the burnt site under different disturbance intensities. Our findings demonstrated that (1) there was no significant change in the Chao index of soil bacteria in the burnt site under different disturbance intensities, whereas the Shannon index decreased significantly (p < 0.05) and the Simpson index increased significantly (p < 0.05) in the burnt site under light and moderate disturbance. (2) The relative abundance of dominant phyla, such as Proteobacteria, Proteobacteria, and Actinobacteriota, did not change significantly in the fire-burnt site under different disturbance intensities, whereas rare species, such as Acidipila, Occallatibacter, and Acidibacter, experienced a significant increase in relative abundance at the genus level. (3) The results of principal coordinates analysis (PCoA) and canonical correlation analysis (CCA) revealed significant differences in the Beta diversity of soil bacteria in the fire-burnt site under varying interference intensities. The Beta diversity of soil bacteria exhibited significant differences (p = 0.001), with MC, pH, TN, AN, and AK identified as significant influencing factors. (4) FAPROTAX functional prediction analyses were conducted to assess the changes in soil bacteria involved in Cellulolysis, Chemoheterotrophy, and Aerobic_Chemoheterotrophy in the fire-burnt site, with the relative abundance of bacteria involved in Chemoheterotrophy being significantly increased (p < 0.05) under different disturbance intensities. Collectively, our findings demonstrated that different disturbance intensities caused by fires significantly affected the Alpha diversity, Beta diversity, and functional abundance of soil bacterial communities in taiga forests, with MC, pH, TN, AN, and AK being identified as key influencing factors. Additionally, the presence of numerous rare species suggests their role as pioneer communities in the succession of soil bacterial communities.

Seepage disturbance mechanism and interface force of cylindrical barrier in fracture

The fluid flow in the crack is disturbed by the contact area. The parallel-plate model with a circular cylindrical contact area is regarded as an idealization of the real contact fracture, and a computational fluid dynamics simulation is performed on it to analyze the interaction between the contact area and the flow around it. The size of the contact area controls the disturbance intensity to the flow velocity magnitude and the disturbance range to the velocity direction. Due to the existence of viscosity, the flow near the wall has a larger shear rate. The intermediate transition region is located between the contact area and the fracture lateral wall and does not contain the region with strong viscous friction caused by the wall. The flow velocity magnitude in the intermediate transition zone changes exponentially in space and has a peak value near the contact area. After the flow bypasses the contact area, the inertial effect caused by the increase in flow velocity magnitude in the local flow channel controls the generation and development of the low-velocity region and the asymmetric degree of the velocity direction distribution. Both the mechanical aperture and the inlet flow velocity affect the stress distribution on the surface of the contact area. The occurrence of the nonlinear flow behavior of fracture seepage and nonlinear change trend of logarithmic drag coefficient curve can be predicted with the same critical Reynolds number. These results provide a useful guide for further exploring the local flow and the surface stress distribution of the local interior geometric property in a single rough-walled fracture on the mesoscopic scale.

Using Lidar to Find the Southeast's Remnant Rivercane

abstract: The floodplains of the Southeast's stream network once hosted immense brakes of rivercane ( Arundinaria gigantea ), a disturbance-dependent native bamboo with both cultural and ecological significance. Ecologically, rivercane alters its local environments, boosts biodiversity and biomass, and protects streambanks from erosion and storm damage. Indigenous peoples of the Southeast have used rivercane for millennia, for material and cultural purposes, and formerly maintained its health and extent through harvesting and fire. Settler-colonial incursions largely destroyed rivercane, through the more intense disturbance of different land management practices, and brakes now exist mainly in relatively small areas. While numerous rivercane restoration projects are in process throughout its natural range, no comprehensive inventory of living rivercane exists. In this paper, we present both human context and the results of LiDAR analysis that identifies canebrakes based on the physical characteristics of the plant and brake. In our study area on the Little Tennessee River in western North Carolina, we found rivercane on about 9 percent of the floodplain area, based on QL1 LiDAR data available from the state of North Carolina. The technique can be applied in any part of rivercane's range, and the resulting inventory used in support of both cultural and ecological goals.

Consequences of plateau pika disturbance on plant-soil carbon and nitrogen in alpine meadows.

The presence of burrowing mammals can have extensive effects on plants and soils, creating bare soil patches in alpine meadows and potentially altering plant-soil carbon (C) and nitrogen (N). This study focuses on the plateau pika (Ochotona curzoniae) to examine the responses of plant-soil C and N to a small burrowing mammal from quadrat scale to plot scale. The density of active burrow entrances in disturbed plots was used as an indicator of the disturbance intensity of plateau pikas. The study found that the below-ground biomass (BGB) and its C and N, as well as soil C and N concentrations were significantly lower in bare soil areas than in vegetated areas and undisturbed plots. This shows that the quadrat scale limited the estimation of the C and N sequestration potential. Therefore, further research on the plot scale found that the disturbance by plateau pika significantly reduced plant biomass and BGB carbon stock. However, plateau pika did not affect soil C and N stocks or ecosystem C and N stocks. These findings suggest the bare soil patches formed by plateau pika caused plant and soil heterogeneity but had a trade-off effect on plant-soil C and N stocks at the plot scale. Nevertheless, moderate disturbance intensity increased the C and N sequestration potential in grassland ecosystems. These results provide a possible way to estimate how disturbance by small burrowing mammals affects C and N cycling in grassland ecosystems while accurately assessing the effects of small burrowing mammal densities on C and N in grassland ecosystems.

The influence of supersonic spatial-temporal coupling disturbance on detonation in an expanded chamber

At present, the most researches on perturbed detonation only considers single factor effects, and there are few studies on the impact of multi-factor coupled perturbations on detonation. In order to match the complex inflow conditions in real situation, the initiation and propagation process of detonation disturbed by spatial-temporal coupling have been studied. This study adopts an adaptive mesh refinement program. It can dynamically capture the structure change of detonation and reduce the total calculation amount. The N-S (Navier-Stokes) equation and single-step reaction model was used in this study. The calculation model is the classic expansion channel that can enhance thrust. After analyze the effects of disturbance amplitudes and disturbance stratification, the results indicates that the stratification phenomenon of disturbance has different effects on the characteristics of flow field. The expansion wall can weaken the disturbance intensity, but its effect is limited. It can only achieve good results when the disturbance on the straight wall side is weak, but the weakening effect of expansion wall also exacerbates the instability of wave. On the other hand, the stability of detonation waves under spatial stratification is stronger, which helps to maintain the intensity of detonation wave.

Disturbance can slow down litter decomposition, depending on severity of disturbance and season: an example from Mount Kilimanjaro

Abstract. Deforestation and land-use change affect ecosystem processes such as carbon cycling. Here, we present results from a litter decomposition experiment in six natural and six disturbed vegetation types along an elevation gradient of 3600 m on the southern slopes of Mount Kilimanjaro, Tanzania. We exposed litter bags with a standard material for up to 12 weeks each in two seasons. In the cold wet season we sampled the full elevation gradient and in the warm wet season we repeated the sampling in the lower part of the elevation gradient. Though we found significantly negative effects of disturbance in forest ecosystems, this was only due to differences between natural and burned Podocarpus forests. Disturbance characterized by a more open vegetation structure in many of the studied vegetation types had no general effect when we studied the full elevation gradient; this also included non-forest vegetation types. Land-use intensity had a significant negative effect on decomposition rates but only in the warm wet season, not in the cold wet season. Temperature and humidity were the most important drivers of decomposition overall and for all subsets of vegetation types and seasons. Our study shows that negative effects of disturbance or land-use intensity on decomposition depended on the severity of disturbance and on the season. Nevertheless, climate was generally the most relevant driver of decomposition. Therefore, vegetation types with moderate levels of disturbance can retain high functionality in regards to carbon cycling over short periods of time. More and longer decomposition studies are necessary to better predict consequences of land-use change for carbon cycling in the Afrotropics.

Biochar Utilization as a Forestry Climate-Smart Tool

Carbon (C) in gaseous form is a component of several greenhouse gases emitted during the combustion of fossil fuels. C movement between the atmosphere, land (biosphere and lithosphere), and ocean (hydrosphere) alters the total amount in each pool. Human activities accelerate C movement into the atmosphere, causing increases in temperature. This shift from terrestrial and oceanic C pools to the atmosphere causes an increase in the intensity, frequency, and duration of catastrophic climate disturbances. Although society hears and reads about C emissions, there is a lack of understanding of its importance and the need to decrease it in the atmospheric pool to avoid exacerbating climate change. Forests and biochar are two biological methods to retain C in the terrestrial pool for a long time and at a very low cost. However, forest harvesting, the use of woody biomass as a source of renewable C for different applications, and the relationship with decreasing C emissions have created a highly controversial topic among governments, the scientific community, society in general, and social groups. The main objective of this review is to highlight the importance of C, forests, and biochar, including the benefits of C sequestration to decrease the impacts of climate change and promote sustainable forests and healthy soils in the future. The main findings show strong evidence that climate-smart forest management practices are an efficient option for managing C and increasing C stocks. This review suggests that forest management mitigation actions are another efficient C management approach with high potential. The findings show that biochar is a climate-smart tool that contributes to climate change mitigation by increasing soil carbon sequestration and reducing soil GHG emissions, including other associated benefits.

Acoustic mechanisms and tonal noise control of contra-rotating ducted fan by rotating speed regulation

The contra-rotating ducted fan (CRDF) involves more tonal noise modes compared with rotor/stator and single-rotor ducted fans. According to the present experiment on small-scale CRDF the dominant tone is concentrated at the harmonics of blade passing frequencies of front-rotor and rear-rotor as the modes of (m,0) and (0,n), as well as the modes (m,m) respectively. To investigate the flow mechanisms and sound propagation characteristics of these three types of tonal noise, unsteady three-dimensional numerical simulation was implemented under different rotational speed matching for CRDF and isolated rotor. Steady load and thickness noise were systematically analyzed using Hanson model. And the generation mechanisms of wake interaction noise and their contribution ratios were analyzed utilizing the duct sound model.It was indicated that tonal noise at the mode of (m,0) (0,n) of CRDF is primarily determined by the blade thickness and steady load. Compared with the single-rotor, the contra-rotating rotors could improve the load allocation between the front and rear rotor, resulting in the forward noise reduction with the constant thrust. Increasing the rear rotor speed enhances the contribution of potential flow interaction noise from the front rotor. Subsequently the front rotor load and wake interference are weakened, leading to noise reduction of approximately 0.3 dB for the rear rotor. However, the potential flow disturbance is intensified which causes noise increase by approximately 3.5 dB on the front rotor. But, increasing the front rotor speed will strengthen both the potential flow interference intensity on the pressure surface of the front rotor blade and the wake disturbance intensity on the leading edge of the rear rotor blade. This generates approximately 3 dB and 3.5 dB noise level increases for the front and rear rotors, respectively. As a result, appropriately raising the rear rotor speed can achieve a reasonable load allocation, and balance the potential flow interaction and wake interaction to realize the whole noise reduction without thrust loss.

LiteTransNet: An interpretable approach for landslide displacement prediction using transformer model with attention mechanism

Accurate landslide displacement prediction is crucial for effective early warning systems to mitigate hazards. The importance of historical information varies with time during prediction due to the underlying landslide deformation mechanism. Despite advances in dynamic machine learning models like Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU), they struggle to fully capture and interpret the varying importance of historical information during prediction, resulting in decreased accuracy and limited understanding of landslide physical mechanisms. Additionally, these approaches rely on manual feature selection, which is independent of the learning process and therefore is prone to estimation errors. To address these challenges, we propose LiteTransNet, a Lightweighted Transformer Network tailored for landslide displacement prediction. Built on the revolutionary Transformer model for sequential data, LiteTransNet leverages localized self-attention to selectively focus on relevant timestamps and provides interpretable results through its attention heatmap. Furthermore, LiteTransNet performs end-to-end time series modeling without extensive feature engineering. We validate LiteTransNet on two landslides in China's Three Gorges Reservoir Area and demonstrate its improved accuracy over recurrent baselines utilizing feature selection methods. Notably, the attention heatmap generated by LiteTransNet provides interpretable insights into the model's temporal dependency learning. It uncovers the varying importance of historical information at different timestamps, showcasing how LiteTransNet's attention aligns with specific periods of the external environment that cause significant disruptions in the landslide system. Our findings reveal that these disruptions continuously impact displacement prediction until their effects fade or are replaced by subsequent intense disturbances, which traditional recurrent methods are unable to capture. Further experiment shows that LiteTransNet enhances efficiency through its streamlined architecture and its parallelization capability. Overall, LiteTransNet innovates landslide prediction by providing accuracy, interpretability, and efficiency, enhancing understanding of deformation mechanisms to facilitate effective early warning systems.

Multiple processes jointly determine ecological uniqueness across forest plant life‐forms in Northeast China

AbstractAimEcological uniqueness is an essential component of biodiversity. However, the mechanisms underlying patterns of ecological uniqueness remain unresolved. This study aims to assess the relative importance as well as interactive roles of four hypothesized processes (regional climate filtering, local environmental filtering, biotic heterogeneity and disturbance intensity [DI]) in shaping ecological uniqueness across three forest plant life‐forms (trees, shrubs and herbs) in a large temperate forest region.LocationNortheast China.MethodsWe quantified ecological uniqueness as abundance and incidence‐based local relative contributions to beta diversity (i.e. LCBD indices) in the study region. Multiple beta regression analyses and piecewise structural equation models were used to determine the relative direct and interactive effects of four processes in shaping ecological uniqueness across forest plant life‐forms.ResultsThe southern area of the region exhibited consistently greater LCBD values across plant life‐forms, highlighting its importance for conservation. All four processes jointly affected ecological uniqueness but their relative importance varied across plant life‐forms. Generally, regional climate had the dominant effect on tree LCBD while biotic heterogeneity was the most important process driving shrub and herb LCBDs. Local environmental filtering was less important in driving LCBD of all life‐forms. The significant direct effect of DI was only found in the herb group. Despite its weak direct effect, DI could indirectly shape tree and shrub LCBDs via biotic heterogeneity.Main ConclusionsOur study suggests that current patterns of ecological uniqueness (i.e. LCBD) across forest plant life‐forms result from multiple processes, with regional climate filtering and biotic heterogeneity having the strongest effects on uniqueness patterns across all life‐forms. Meanwhile, DI is more critical for shaping ecological uniqueness of herbs than trees or shrubs. We highlight the interactive roles of biotic and abiotic filtering in shaping biologically distinct communities important for biodiversity conservation.

Successional changes in bacterial phyllosphere communities are plant-host species dependent.

Leaf surface microbiomes have the potential to influence agricultural and ecosystem productivity. We assessed their stability by determining composition, functional resistance, and resilience. Resistance is the degree to which communities remain unchanged as a result of disturbance, and resilience is the ability of a community to recover to pre-disturbance conditions. By understanding the mechanisms of community assembly and how they relate to the resistance and resilience of microbial communities under common environmental stresses such as drought, we can better understand how communities will adapt to a changing environment and how we can promote healthy agricultural microbiomes. In this study, phyllosphere compositional stability was highly related to plant host species phylogeny and, to a lesser extent, known stress tolerances. Phyllosphere community assembly and stability are a result of complex interactions of ecological processes that are differentially imposed by host species.