In recent decades, increases in severe drought, heat extremes, and pest burden have contributed to increased global tree mortality. These risks are expected to be exacerbated under projected climate ...change. So far, observations of tree mortality are mainly based on manual field surveys with limited spatial coverage. The lack of accurate tree mortality data over large areas has limited the development and applications of tree mortality models. However, a combination of high-resolution remote sensing data, such as aerial imagery and automated imagery analysis, may provide a solution to this problem. In this study, we analysed the dynamics and drivers of forest canopy mortality in 117 366 ha of boreal forest in Southeast Finland, between 2017 and 2023. For this purpose, we first developed a fully convolutional semantic segmentation model to automatically segment forest canopy mortality from aerial imagery in 2017, 2020, and 2023 with a spatial resolution of 0.5 m. Secondly, we trained the model using a dataset consisting of 32555 canopy mortality segments manually delineated from aerial imagery from various geographic regions in Finland. The trained model showed high accuracy in detecting forest canopy mortality (with an F1 score of 0.86–0.93) when tested using an independent test set. To estimate standing deadwood volume, we combined the observed yearly forest canopy mortality with open forest resource information based on extensive field campaigns and airborne laser scanning. In our study area, forest canopy mortality increased from 23.4 ha (0.02 % of the study area) to 207.8 ha (0.18 %) between 2017 and 2023. Consequently, standing deadwood volume was estimated to increase from 5192 m3 (0.04 m3/ha) to 52800 m3 (0.45 m3/ha) during the study period. Both the volume of standing deadwood and the extent of forest canopy mortality increased exponentially. The majority of the forest canopy mortality occurred in Norway spruce-dominated forests (64.1–77.3 %) on relatively fertile soils (81.6–84.7 %) while 20–25 % of the forest canopy mortality occurred in Scots pine-dominated forests. The average age of stands where mortality was observed was between 60 and 70 years old (2017 = 69.7 years and 2023 = 62.6 years), indicating that mature forests were more susceptible to mortality than younger stands. Our findings highlight an exponential increase in forest canopy mortality over a relatively short time span (6 years). The increasing risk of tree mortality in boreal forests underlines the urgent need for large-scale and spatially accurate monitoring to keep up to date with fast-paced changes in boreal forest mortality. As climate change increases drought, extreme heat and bark beetle outbreaks, consistent canopy mortality mapping is essential for implementing timely risk management measures in forestry.
•Forest canopy mortality increased by 788 % between 2017 and 2023.•Distribution of canopy mortality shifted towards younger forest stands.•Forest canopy mortality detected with an F1-score of 0.86–0.93 from aerial imagery.
Information on forest structure is vital for sustainable forest management. Currently, airborne LiDAR remote sensing has been well established as an effective tool to characterize the structure of ...canopies and forest inventory variables. Radiometry and geometry are highly intertwined in LiDAR remote sensing of forest vegetation and phenology influences the geometric-optical properties of deciduous and evergreen trees causing seasonal variation in LiDAR observations. This variation may be considered as a nuisance or exploited in for example tree species identification. Airborne LiDAR data are also influenced by sensor functioning, acquisition settings, scan geometry and the atmosphere. Reliable estimation of subtle phenological effects calls for data in which the impact of the external factors is minimal. We experimented with such data and explored LIDAR waveforms (WFs) in boreal trees in winter, early summer and late summer. Our objectives were to i) assess the match of the multitemporal LiDAR data for observing true changes in vegetation; ii) quantify the influence of phenology in deciduous and evergreen trees; iii) study the effect of varying scan zenith angle (SZA) and canopy age on WF features in different phenostates; iv) assess the temporal feature correlation in individual living and dead standing trees. A WF-recording pulsed LiDAR sensor unit operating at the wavelength of 1550 nm was used in repeated acquisitions. WF attributes such as energy, peak amplitude and echo width were derived for each pulse and were localized vertically to crown, understory and ground components. Silver and downy birch, black alder, European aspen, Siberian larch, Scots pine, Norway spruce and dead standing spruce formed our strata. Results showed that phenology caused more variation in WF features of deciduous trees compared to evergreen conifers. Deciduous trees displayed substantial between-species variation that was linked with differences in branching pattern, leaf orientation and bark reflectance. Pine displayed a possible winter-early summer anomaly in canopy backscattering that may be linked with changes in foliage clumping or with the role of stamens in early summer trees. Trees displayed positive temporal correlation in WF features and correlations were the strongest in evergreen and deciduous conifers and decreased with time. SZA had minor influence on WF features whereas age exercised a strong effect on many features with parallel variation between species and phenostates. Structural changes following death, i.e. ‘aging’ changed the geometric WF features of dead standing trees. Our results provide new insights for enhancing tree species identification by using WF LiDAR and for LiDAR time-series analysis of vegetation.
•Multitemporal waveform (WF) LiDAR data with high radiometric and geometric match.•Effects of phenology on WF features at 1550 nm investigated.•Phenological effects are larger in deciduous than in evergreen trees.•WFs vary seasonally also in evergreen trees, but geometric WF features are stable.•WF features of dead standing trees change over time.
Tree mortality impacts biodiversity, carbon dynamics and the management of forests. Climate change is expected to increase tree mortality, but understanding of tree mortality rates and the underlying ...processes is limited; thus, more accurate and efficient tree mortality mapping methods are required. In this study, we investigated the feasibility of using airborne light detection and ranging (LiDAR) waveform (WF) features in detecting dead trees to monitor tree mortality and studied how the WF features of dead trees change over time. We used three consecutive LiDAR campaigns using fixed sensor and flight parameters in a boreal forest in Southern Finland (61.5°N, 24.2°E). The campaigns spanned four years and were carried out in 2011, 2013 and 2015. A Riegl LMS-Q680i LiDAR sensor, which operates at 1550 nm wavelength, provided return WF data to study the geometric-optical properties of living and dead trees and monitor mortality of Norway spruce (Picea abies H. Karst.). Our findings highlight the differences in radiometric and geometric WF features between living and dead trees. The return WFs from dead trees were consistently elongated and contained more backscattering energy. We also found that as a tree died, the canopy and branch structures became less dense and more irregular, leading to more complex return WFs. The WF features were used for binary classification of living and dead trees, resulting in classification accuracies between 94.7 and 98.5%, depending on the campaign. Distinguishing between living and dead trees is challenging for trees that have died recently when there are only minor defects in the crown and discoloration of foliage. Tree decay after death improved the discernability between living and dead trees as the geometric-optical properties of the crown change. The radiometric and geometric WF features and canopy mortality effects on the WF features are consistent across datasets implying intrinsic quality of information in the WF features. The within-class variance of WF features in dead trees is greater than that in living trees, indicating significant variations in the geometric and radiometric properties of trees between stages of decaying and dying. Our results imply that LiDAR WFs can be used for the accurate detection of dead trees to map tree mortality.
•Tree mortality mapping with multitemporal waveform (WF) LiDAR.•Geometric-optical traits of dead trees monitored over time.•Tree decay after death alters geometrical and optical properties of the crown.•WF signals from dead trees are elongated and have stronger backscattering.•Radiometric WF features perform well in classifying dead trees.
Tree species identification constitutes a bottleneck in remote sensing applications. Waveform LiDAR has been shown to offer potential over discrete-return observations, and we assessed if the ...combination of two-wavelength waveform data can lead to further improvements. A total of 2532 trees representing seven living and dead conifer and deciduous species classes found in Hyytiälä forests in southern Finland were included in the experiments. LiDAR data was acquired by two single-wavelength sensors. The 1064-nm and 1550-nm data were radiometrically corrected to enable range-normalization using the radar equation. Pulses were traced through the canopy, and by applying 3D crown models, the return waveforms were assigned to individual trees. Crown models and a terrain model enabled a further split of the waveforms to strata representing the crown, understory and ground segments. Different geometric and radiometric waveform attributes were extracted per return pulse and aggregated to tree-level mean and standard deviation features. We analyzed the effect of tree size on the features, the correlation between features and the between-species differences of the waveform features. Feature importance for species classification was derived using F-test and the Random Forest algorithm. Classification tests showed significant improvement in overall accuracy (74→83% with 7 classes, 88→91% with 4 classes) when the 1064-nm and 1550-nm features were merged. Most features were not invariant to tree size, and the dependencies differed between species and LiDAR wavelength. The differences were likely driven by factors such as bark reflectance, height growth induced structural changes near the treetop as well as foliage density in old trees.
•Trees affected by green attack were identified within a limited time window.•The detection rates increased from 0.3 to 0.8 two weeks before brood emergence began.•The highest separability was found ...in the green shoulder region (490–550 nm).•Green shoulder infection/curvature points shifted during vitality decline.•Indices were developed with higher accuracy and simplified with three bands.
Forest stress monitoring and in-time identification of forest disturbances are important to improve forest resilience to climate change. Fast-developing drone techniques and hyperspectral imagery provide tools for understanding the forest decline process under stress and contribute to focused monitoring. This study explored and developed hyperspectral drone imagery for early detection of forest stress caused by European spruce bark beetle Ips typographus (L.), before offspring emergence, which is crucial in controlling the spread but has been shown to be challenging.
This study challenges the highest possible detectability of infested trees using a hyperspectral drone system that provided images with very high spectral, spatial, and temporal resolutions in Southern Finland. Images were acquired bi-weekly, four times (T1, T2, T3, T4), covering 8 weeks from trees being attacked by the first filial generation (F1) to the beginning of second filial generation (F2) brood emergence. Very low separability was observed for the reflectance from healthy and attacked trees, but the first and second derivative reflectance captured vitality changes, with the green shoulder region (wavelengths 490–550 nm) exhibiting the highest separability of all wavelengths (400–1700 nm). We discovered that the peak and valley values of the first and second derivative curves in the green shoulder region consistently shifted with longer infestation time.
Based on this finding, we developed green shoulder indices. The detection rates were 0.24–0.31 and 0.76–0.83 for T3 and T4, higher than commonly used VIs such as the Photochemical Reflectance Index and the Red Edge Inflection Position, with detection rates of 0.69 and 0.34 for T4, respectively. We also proposed simplified green shoulder indices using the reflectance from three bands that can be used with multispectral cameras and satellite images for large area monitoring of forest health. We concluded that the detectability of infestations was very low for the first month after attack, and then rapidly increased before brood emergence. We highlighted the great potential of green shoulder indices in quantifying the photochemical functioning of the vegetation under stress. The methodology can potentially be applied for early identification of forests with declining vitality caused by various sources of forest stress and disturbances, such as infestations, diseases and drought.
Patients treated with deep brain stimulation (DBS) provide an opportunity to study affective processes in humans with “lesion on demand” at key nodes in the limbic circuitries, such as at the ...anterior thalamic nuclei (ANT). ANT has been suggested to play a role in emotional control with its connection to the orbitofrontal cortex and the anterior cingulate cortex. However, direct evidence for its role in emotional function in human subjects is lacking. Reported side effects of ANT–DBS in the treatment of refractory epilepsy include depression related symptoms. In line with these mood-related clinical side effects, we have previously reported that stimulating the anterior thalamus increased emotional interference in a visual attention task as indicated by prolonged reaction times due to threat-related emotional distractors. We used event-related potentials to investigate potential attentional mechanism behind this behavioural observation. We hypothesized that ANT–DBS leads to greater attention capture by threat-related distractors. We tested this hypothesis using centro-parietal N2–P3 peak-to-peak amplitude as a measure of allocated attentional resources. Six epileptic patients treated with deep brain stimulation at ANT participated in the study. Electroencephalography was recorded while the patients performed a computer based Executive-Reaction Time test with threat-related emotional distractors. During the task, either ANT or a thalamic control location was stimulated, or the stimulation was turned off. Stimulation of ANT was associated with increased centro-parietal N2–P3 amplitude and increased reaction time in the context of threat-related emotional distractors. We conclude that high frequency electric stimulation of ANT leads to greater attentional capture by emotional stimuli. This is the first study to provide direct evidence from human subjects with on-line electric manipulation of ANT for its role in emotion–attention interaction.
•DBS studies provide novel insight into into the neural circuits behind emotion.•Human anterior thalamic nuclei (ANT) are involved in emotion–attention interaction.•ANT–DBS has an effect on emotion–attention interaction.•ANT–DBS leads to greater attentional capture by threat-related emotional stimuli.•Emotional modulation of N2–P3 provides a biomarker for emotion–attention interplay.
Chronic subdural haematoma is a common surgically treated intracranial emergency. Burr-hole drainage surgery, to evacuate chronic subdural haematoma, involves three elements: creation of a burr hole ...for access, irrigation of the subdural space, and insertion of a subdural drain. Although the subdural drain has been established as beneficial, the therapeutic effect of subdural irrigation has not been addressed.
The FINISH trial was an investigator-initiated, pragmatic, multicentre, nationwide, randomised, controlled, parallel-group, non-inferiority trial in five neurosurgical units in Finland that enrolled adults aged 18 years or older with a chronic subdural haematoma requiring burr-hole drainage. Patients were randomly assigned (1:1) by computer-generated block randomisation with block sizes of four, six, or eight, stratified by site, to burr-hole drainage either with or without subdural irrigation. All patients and staff were masked to treatment assignment apart from the neurosurgeon and operating room staff. A burr hole was drilled at the site of maximum haematoma thickness in both groups, and the subdural space was either irrigated or not irrigated before inserting a subdural drain, which remained in place for 48 h. Reoperations, functional outcome, mortality, and adverse events were recorded for 6 months after surgery. The primary outcome was the reoperation rate within 6 months. The non-inferiority margin was set at 7·5%. Key secondary outcomes that were also required to conclude non-inferiority were the proportion of participants with unfavourable functional outcomes (ie, modified Rankin Scale score of 4–6, where 0 indicates no symptoms and 6 indicates death) and mortality rate at 6 months. The primary and key secondary analyses were done in both the intention-to-treat and per-protocol populations. The trial was registered with ClinicalTrials.gov (NCT04203550) and is completed.
From Jan 1, 2020, to Aug 17, 2022, we assessed 1644 patients for eligibility and 589 (36%) patients were randomly assigned to a treatment group and treated (294 assigned to drainage with irrigation and 295 assigned to drainage without irrigation; 165 28% women and 424 72% men). The 6-month follow-up period extended until Feb 14, 2023. In the intention-to-treat analysis, 54 (18·3%) of 295 participants required reoperation in the group assigned to receive no irrigation versus 37 (12·6%) of 294 in the group assigned to receive irrigation (difference of 6·0 percentage points, 95% CI 0·2–11·7; p=0·30; adjusted for study site). There were no significant between-group differences in the proportion of people with modified Rankin Scale score of 4–6 (37 13·1% of 283 in the no-irrigation group vs 36 12·6% of 285 in the irrigation group; p=0·89) or mortality rate (18 6·1% of 295 in the no-irrigation group vs 21 7·1% of 294 in the irrigation group; p=0·58). The findings of the primary intention-to-treat analysis were not materially altered in the per-protocol analysis. There were no significant between-group differences in the number of adverse events, and the most frequent severe adverse events were systemic infections (26 8·8% of 295 participants who did not receive irrigation vs 22 7·5% of 294 participants who received irrigation), intracranial haemorrhage (13 4·4% vs seven 2·4%), and epileptic seizures (five 1·7% vs nine 3·1%).
We could not conclude non-inferiority of burr-hole drainage without irrigation. The reoperation rate was 6·0 percentage points higher after burr-hole drainage without subdural irrigation than with subdural irrigation. Considering that there were no differences in functional outcome or mortality between the groups, the trial favours the use of subdural irrigation.
State Fund for University Level Health Research (Helsinki University Hospital), Finska Läkaresällskapet, Medicinska Understödsföreningen Liv och Hälsa, and Svenska Kulturfonden.
Mild traumatic brain injury (mTBI) may be associated with compromised executive functioning and altered emotional reactivity. Despite frequent affective and cognitive symptoms in mTBI, objective ...evidence for brain dysfunction is often lacking. Previously we have reported compromised performance in symptomatic mTBI patients in an executive reaction time (RT) test, a computer-based RT test engaging several executive functions simultaneously. Here, we investigated the cognitive control processes in mTBI in context of threat-related stimuli. We used behavioral measures and event-related potentials (ERP) to investigate attentional capture by task-relevant and task-irrelevant emotional stimuli during a Go-NoGo task requiring cognitive control. We also assessed subjective cognitive, somatic, and emotional symptoms with questionnaires. Twenty-seven subjects with previous mTBI and 17 controls with previous ankle injury participated in the study over 9 months post-injury. Electroencephalogram (EEG) was recorded while patients performed a modified executive RT-test. N2-P3 ERP component was used as a general measure of allocated attentional and executive processing resources. Although at the time of the testing, the mTBI and the control groups did not differ in symptom endorsement, mTBI patients reported having had more emotional symptoms overall since the injury than controls. The overall RT-test performance levels did not differ between groups. However, when threat-related emotional stimuli were used as Go-signals, the mTBI group was faster than the control group. In comparison to neutral stimuli, threat-related stimuli were associated with increased N2-P3 amplitude in all conditions. This threat-related enhancement of the N2-P3 complex was greater in mTBI patients than in controls in response to Go signals and NoGo signals, independent of relevance. We conclude that mTBI may be associated with enhanced attentional and executive resource allocation to threat-related stimuli. Along with behavioral evidence for enhanced attention allocation to threat stimuli, increased brain responses to threat were observed in mTBI. Enhanced attention capture by threat-related emotional stimuli may reflect inefficient top-down control of bottom-up influences of emotion, and might contribute to affective symptoms in mTBI.
Background: Deep brain stimulation (DBS) of anterior thalamic nuclei (ANT) is a novel promising therapeutic method for treating refractory epilepsy. Despite reports of subjective memory impairments ...and mood disturbances in patients with ANT-DBS, little is known of its effects on cognitive and affective processes. Hypothesis: The anterior thalamus has connections to prefrontal and limbic networks important for cognitive control and emotional reactivity. More specifically, anterior cingulate cortex (ACC), linked with ANT, has been assigned roles related to response inhibition and attention allocation to threat. Thus, we hypothesized ANT-DBS to influence executive functions, particularly response inhibition, and modulate emotional reactivity to threat. Method: Twelve patients having undergone ANT-DBS for intractable epilepsy participated in the study. Patients performed a computer-based executive reaction time (RT) test-that is, a go/no-go visual discrimination task with threat-related emotional distractors and rule switching, while the DBS was switched ON (5/5 mA constant current) and OFF every few minutes. Results: ANT-DBS increased the amount of commission errors-that is, errors where subjects failed to withhold from responding. Furthermore, ANT-DBS slowed RTs in context of threat-related distractors. When stimulation was turned off, threat-related distractors had no distinct effect on RTs. Conclusion: We found immediate objective effects of ANT-DBS on human cognitive control and emotion-attention interaction. We suggest that ANT-DBS compromised response inhibition and enhanced attention allocation to threat due to altered functioning of neural networks that involve the DBS-target, ANT, and the regions connected to it such as ACC. The results highlight the need to consider affective and cognitive side-effects in addition to the therapeutic effect when adjusting stimulation parameters. Furthermore, this study introduces a novel window into cognitive and affective processes by modulating the associative and limbic networks with direct stimulation of key nodes in the thalamus.
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BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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