Natural disturbance and treefalls in a pine-oak forest on the Peninsula of Baja California,Mexico

The magnitude of natural disturbances by treefalls and their spatial occurrence were studied in a pine-oak forest of Sierra de La Laguna, located at the southern part of the Peninsula of Baja California in Mexico.Twenty transects covering 4 ha, perpendicular to north- and south-facing slopes were sampled. The percentages of rocky outcrops, slope, orientation, and gap size created by treefalls were recorded. The mode of tree death, treefall direction, trunk length, and basal diameter were also measured. Data were analyzed using principal component analysis, one-way ANOVA, multiple comparison tests by contrasts, and chi-square independence tests.Results suggest that exogenous disturbances have an important effect in this community. A mean number of 80 gaps per ha was recorded comprising 18.1% of the observed area. Gap sizes were fitted to a lognormal distribution as 2.3±1.4 and patches were found to be created by single treefalls. Analysis of dead material shows that there are significant differences between numbers of fallen trees on N vs S facing slopes, and that forms of dead trees are significantly associated with species. Snapped trees represent 39.5% of treefalls, dead standing trees 26.4%, uprooted trees 20.5% and cut-down trees 0.9%. The frequency of occurrence of various forms of the dead trees suggests that the cause of mortality is primarily due to the high incidence of tropical hurricanes, and secondly to the combined effect of wind and natural fire which occurs during the rainy summer season.     

Dating lightning: Dendrochronological and magnetic analyses of lightning scars

Lightning impacts on forests and trees are still understudied from a tree-ring perspective. Lighting causes direct and indirect damages on forests and trees. Trees struck by lightning can show a growth reduction and lightning storms also trigger wildfires in seasonally dry areas such as Mediterranean mountains. Here we combined dendroecological and magnetic analyses to reconstruct and assess the impact of lightning on radial growth and the magnetic properties of wood in Scots pine (Pinus sylvestris) and Black pine (Pinus nigra) in two sites with a high density of lightning impacts located in eastern Spain. We dated several lightning scars, particularly in Scots pine, formed during 1982, when a wildfire was initiated by lightning during a dry summer storm. Growth was reduced during the year when the scar was formed in both pine species, albeit this effect could be masked or amplified by other disturbances (drought, outbreaks). However, despite that short-term growth reduction scarred trees showed higher growth rates than non-scarred trees in the case of Scots pine. The intensity of magnetization did not significantly differ in wood produced before and after the lightning scar was formed. This could be due to multiple lightning hits in the same or nearby stands affecting the magnetization of wood. Wood magnetic properties should be further explored as proxies of lightning impacts in sites where scars are not formed and tree-ring information is limited such as tropical forests. Further cross-disciplinary research is required to assess the impacts of lightning on tree growth and magnetism.     

Plant cytoplasm preserved by lightning

Usually only an organism with hard parts may be preserved in the fossil record. Cytoplasm, which is a physiologically active part of a plant, is rarely seen in the fossil record. Two Cretaceous plant fossils older than 100 million years with exceptional preservation of cytoplasm are reported here. Some cytoplasm is well preserved with subcellular details while other cytoplasm is highly hydrolyzed in the cortex of the same fossil even though both of preservations may be less than 2 microm away. The unique preservation pattern, sharp contrast of preservation in adjacent cells and the exceptional preservation of cytoplasm in the cortex suggest that lightning should play an important role in the preservation of cytoplasm and that cytoplasmic membranes may be more stable than the cell contents. Interpreting the preservation needs knowledge scattering in several formerly unrelated fields of science, including geophysics, botany, biophysics, cytology and microwave fixation technology. This new interpretation of fossilization will shed new light on preservation of cytoplasm and promote cytoplasm fossils from a position of rarity to a position of common research objects available for biological research. The importance of the identification of cytoplasm in fossil lies not in itself but in how much it influences the future research in paleobotany.     

Fire season affects size and architecture of Colophospermum mopane in southern African savannas

Wildfires may be started naturally by lightning or artificially by humans. In the savanna regions of southern Africa, lightning fires tend to occur at the start of the wet season, during October and November, while anthropogenic fires are usually started during the dry season, between July and August. A long-term field manipulation experiment initiated in the Kruger National Park in 1952 was used to explore whether this seasonal divergence affects tree abundance, spatial pattern, size and architecture. After 44 years of prescribed burning treatments that simulated the seasonal incidence of lightning and anthropogenic fires, mean densities of the locally-dominant shrub, Colophospermum mopane, were 638 and 500 trees ha^–1 respectively. Trees in burnt plots had aggregated distributions while trees in unburnt plots had random distributions. Significant differences (p < 0.001) were recorded in a range of morphological parameters including tree height, canopy diameter, mean stem circumference and number of stems. The incidence of resprouting also differed significantly between treatments, with burnt trees containing a high proportion of coppiced stems. The differences in tree size and architecture between the mid-dry season and early-wet season burning plots suggest that anthropogenic fires applied during July and August cannot substitute for a natural lightning fire regime. Anthropogenic fire yields a landscape that is shorter, more scrubby and populated by numerous coppiced shrubs than the landscape generated by natural lightning fire conditions.     

Spatial and temporal variation in lightning ignitions in Sweden

Abstract. Analysis of fire statistics revealed that there are steep gradients in the distribution of lightning-caused fire ignitions in Sweden. The highest ignition density was found in the southeastern provinces of Kalmar and Östergötland, ca. 0.23/10 000 ha/yr. From there, densities generally declined both to the north and to the west, with a density averaging ca. 0.05 in the six northernmost provinces, and an equally low density in the southwestern province of Halland. For both northern and southern Sweden, lightning ignitions peaked in early July, but in the south the season for ignitions started 2–3 weeks earlier and ended 2–3 weeks later. The geographical gradients in lightning ignition density correspond to the average precipitation during summer. The patterns of lightning ignition densities may also indicate gradients in natural fire frequencies. This hypothesis is supported by the distribution of certain fire-adapted plant species.     

Inverse planning in Gamma Knife radiosurgery: A comparative planning study

PurposeTo determine the advantages of inverse planning using a prerelease version of Leksell Gamma Knife® (LGK) Lightning (Elekta AB, Sweden) compared to manual forward planning.MethodsThirty-eight patients with metastases (MET, n = 15), vestibular schwannomas (VS, n = 11) and meningiomas (MEN, n = 12), treated with LGK Icon™ at our institution, were analyzed retrospectively. For each case, an inverse (inv) and inverse full coverage (fc) treatment plan was generated using LGK Lightning and compared to the clinical plans. Several dosimetry and efficiency characteristics were compared for each indication. The mean, median difference and interquartile range were reported and the significance was assessed with a paired-sample Wilcoxon test (significance level < 0.05). Further, the inter operator variability was analyzed for multiple users.ResultsInv and fc treatment plans show improved target coverage (up to 3.6%) for all analyzed paradigms. For inv plans, the selectivity is enhanced (MET: 2.9%; VS: 1.8%; MEN: 1%) and the organ at risk doses are significantly reduced (VS: up to 4.5%; MEN: up to 17.5%). For inv and fc plans, the beam on time (BOT) is shortened (MET: up to 7.9%; benign tumors: 49.5%). The inter operator variability analysis shows similar treatment plan quality with small differences in plan efficiency (difference in BOT: 1–3.3 min).ConclusionsLGK Lightning allows to generate improved LGK treatment plans regarding plan quality with reduced BOT compared to manual forward plans. The inter operator variability showed that multiple users with different experiences can generate similar treatment plan quality using LGK Lightning.     

The lightning heart: a case report and brief review of the cardiovascular complications of lightning injury

Lightning strike is a rare natural phenomenon, which carries a risk of dramatic medical complications to multiple organ systems and a high risk of fatality. The known complications include but are not limited to: myocardial infarction, arrhythmia, cardiac contusion, stroke, cutaneous burns, respiratory disorders, neurological disorders, acute kidney injury and death. We report a case of a healthy young man who suffered a lightning injury and discuss the cardiovascular complications of lightning injury, ranging from ECG changes to death. The patient in our case, a 27-year old previously healthy male, developed a syndrome of rhabdomyolysis and symptomatic cardiogenic pulmonary edema. Electrocardiographic findings included transient T-wave inversions, late transition shift and long QT. His clinical condition improved with supportive measures.Early recognition of lightning injury syndromes and anticipation of complications may help us improve outcomes for these patients. Evaluation of patients having experienced a lightning injury should include a minimum of a detailed history and physical examination, 12-lead ECG and drawing of baseline troponins. Prolonged electrocardiographical monitoring (for monitoring of ventricular arrhythmias) and assessment for signs and symptoms of hemodynamic compromise may be warranted.