Death from drought in tropical forests is triggered by hydraulics not carbon starvation.

Drought threatens tropical rainforests over seasonal to decadal timescales, but the drivers of tree mortality following drought remain poorly understood. It has been suggested that reduced availability of non-structural carbohydrates (NSC) critically increases mortality risk through insufficient carbon supply to metabolism ('carbon starvation'). However, little is known about how NSC stores are affected by drought, especially over the long term, and whether they are more important than hydraulic processes in determining drought-induced mortality. Using data from the world's longest-running experimental drought study in tropical rainforest (in the Brazilian Amazon), we test whether carbon starvation or deterioration of the water-conducting pathways from soil to leaf trigger tree mortality. Biomass loss from mortality in the experimentally droughted forest increased substantially after >10 years of reduced soil moisture availability. The mortality signal was dominated by the death of large trees, which were at a much greater risk of hydraulic deterioration than smaller trees. However, we find no evidence that the droughted trees suffered carbon starvation, as their NSC concentrations were similar to those of non-droughted trees, and growth rates did not decline in either living or dying trees. Our results indicate that hydraulics, rather than carbon starvation, triggers tree death from drought in tropical rainforest.

Drought impact on forest carbon dynamics and fluxes in Amazonia.

In 2005 and 2010 the Amazon basin experienced two strong droughts, driven by shifts in the tropical hydrological regime possibly associated with global climate change, as predicted by some global models. Tree mortality increased after the 2005 drought, and regional atmospheric inversion modelling showed basin-wide decreases in CO2 uptake in 2010 compared with 2011 (ref. 5). But the response of tropical forest carbon cycling to these droughts is not fully understood and there has been no detailed multi-site investigation in situ. Here we use several years of data from a network of thirteen 1-ha forest plots spread throughout South America, where each component of net primary production (NPP), autotrophic respiration and heterotrophic respiration is measured separately, to develop a better mechanistic understanding of the impact of the 2010 drought on the Amazon forest. We find that total NPP remained constant throughout the drought. However, towards the end of the drought, autotrophic respiration, especially in roots and stems, declined significantly compared with measurements in 2009 made in the absence of drought, with extended decreases in autotrophic respiration in the three driest plots. In the year after the drought, total NPP remained constant but the allocation of carbon shifted towards canopy NPP and away from fine-root NPP. Both leaf-level and plot-level measurements indicate that severe drought suppresses photosynthesis. Scaling these measurements to the entire Amazon basin with rainfall data, we estimate that drought suppressed Amazon-wide photosynthesis in 2010 by 0.38 petagrams of carbon (0.23-0.53 petagrams of carbon). Overall, we find that during this drought, instead of reducing total NPP, trees prioritized growth by reducing autotrophic respiration that was unrelated to growth. This suggests that trees decrease investment in tissue maintenance and defence, in line with eco-evolutionary theories that trees are competitively disadvantaged in the absence of growth. We propose that weakened maintenance and defence investment may, in turn, cause the increase in post-drought tree mortality observed at our plots.

The sensitivity of wood production to seasonal and interannual variations in climate in a lowland Amazonian rainforest.

Understanding climatic controls on tropical forest productivity is key to developing more reliable models for predicting how tropical biomes may respond to climate change. Currently there is no consensus on which factors control seasonal changes in tropical forest tree growth. This study reports the first comprehensive plot-level description of the seasonality of growth in a Peruvian tropical forest. We test whether seasonal and interannual variations in climate are correlated with changes in biomass increment, and whether such relationships differ among trees with different functional traits. We found that biomass increments, measured every 3 months on the two plots, were reduced by between 40 and 55% in the peak dry season (July-September) relative to peak wet season (January-March). The seasonal patterns of biomass accumulation are significantly (p < 0.01) associated with seasonal patterns of rainfall and soil water content; however, this may reflect a synchrony of seasonal cycles rather than direct physiological controls on tree growth rates. The strength of the growth seasonality response among trees is significantly correlated to functional traits: consistent with a hypothesised trade-off between maximum potential growth rate and hydraulic safety, tall and fast-growing trees with broad stems had the most strongly seasonal biomass accumulation, suggesting that they are more productive in the wet season, but more vulnerable to water limitation in the dry season.

Small understorey trees have greater capacity than canopy trees to adjust hydraulic traits following prolonged experimental drought in a tropical forest.

Future climate change predictions for tropical forests highlight increased frequency and intensity of extreme drought events. However, it remains unclear whether large and small trees have differential strategies to tolerate drought due to the different niches they occupy. The future of tropical forests is ultimately dependent on the capacity of small trees (<10 cm in diameter) to adjust their hydraulic system to tolerate drought. To address this question, we evaluated whether the drought tolerance of neotropical small trees can adjust to experimental water stress and was different from tall trees. We measured multiple drought resistance-related hydraulic traits across nine common neotropical genera at the world's longest-running tropical forest throughfall-exclusion experiment and compared their responses with surviving large canopy trees. Small understorey trees in both the control and the throughfall-exclusion treatment had lower minimum stomatal conductance and maximum hydraulic leaf-specific conductivity relative to large trees of the same genera, as well as a greater hydraulic safety margin (HSM), percentage loss of conductivity and embolism resistance, demonstrating that they occupy a distinct hydraulic niche. Surprisingly, in response to the drought treatment, small trees increased specific hydraulic conductivity by 56.3% and leaf:sapwood area ratio by 45.6%. The greater HSM of small understorey trees relative to large canopy trees likely enabled them to adjust other aspects of their hydraulic systems to increase hydraulic conductivity and take advantage of increases in light availability in the understorey resulting from the drought-induced mortality of canopy trees. Our results demonstrate that differences in hydraulic strategies between small understorey and large canopy trees drive hydraulic niche segregation. Small understorey trees can adjust their hydraulic systems in response to changes in water and light availability, indicating that natural regeneration of tropical forests following long-term drought may be possible.

The sensitivity of tropical leaf litter decomposition to temperature: results from a large-scale leaf translocation experiment along an elevation gradient in Peruvian forests.

• We present the results from a litter translocation experiment along a 2800-m elevation gradient in Peruvian tropical forests. The understanding of the environmental factors controlling litter decomposition is important in the description of the carbon and nutrient cycles of tropical ecosystems, and in predicting their response to long-term increases in temperature. • Samples of litter from 15 species were transplanted across all five sites in the study, and decomposition was tracked over 448 d. • Species' type had a large influence on the decomposition rate (k), most probably through its influence on leaf quality and morphology. When samples were pooled across species and elevations, soil temperature explained 95% of the variation in the decomposition rate, but no direct relationship was observed with either soil moisture or rainfall. The sensitivity of the decay rate to temperature (κ(T)) varied seven-fold across species, between 0.024 and 0.169 °C⁻¹, with a mean value of 0.118 ± 0.009 °C⁻¹ (SE). This is equivalent to a temperature sensitivity parameter (Q10) for litter decay of 3.06 ± 0.28, higher than that frequently assumed for heterotrophic processes. • Our results suggest that the warming of approx. 0.9 °C experienced in the region in recent decades may have increased decomposition and nutrient mineralization rates by c. 10%.

Shifts in plant respiration and carbon use efficiency at a large-scale drought experiment in the eastern Amazon.

*The effects of drought on the Amazon rainforest are potentially large but remain poorly understood. Here, carbon (C) cycling after 5 yr of a large-scale through-fall exclusion (TFE) experiment excluding about 50% of incident rainfall from an eastern Amazon rainforest was compared with a nearby control plot. *Principal C stocks and fluxes were intensively measured in 2005. Additional minor components were either quantified in later site measurements or derived from the available literature. *Total ecosystem respiration (R(eco)) and total plant C expenditure (PCE, the sum of net primary productivity (NPP) and autotrophic respiration (R(auto))), were elevated on the TFE plot relative to the control. The increase in PCE and R(eco) was mainly caused by a rise in R(auto) from foliage and roots. Heterotrophic respiration did not differ substantially between plots. NPP was 2.4 +/- 1.4 t C ha(-1) yr(-1) lower on the TFE than the control. Ecosystem carbon use efficiency, the proportion of PCE invested in NPP, was lower in the TFE plot (0.24 +/- 0.04) than in the control (0.32 +/- 0.04). *Drought caused by the TFE treatment appeared to drive fundamental shifts in ecosystem C cycling with potentially important consequences for long-term forest C storage.

Estimates and relationships between aboveground and belowground resource exchange surface areas in a Sitka spruce managed forest.

Our knowledge of the nature of belowground competition for moisture and nutrients is limited. In this study, we used an earth impedance method to determine the root absorbing area of Sitka spruce (Picea sitchensis (Bong.) Carr.) trees, making measurements in stands of differing density (2-, 4- and 6-m inter-tree spacing). We compared absorbing root area index (RAI(absorbing); based on the impedance measure) with fine root area index (RAI(fine); based on estimates of total surface area of fine roots) and related these results to investment in conductive roots. Root absorbing area was a near-linear function of tree stem diameter at 1.3 m height. At the stand level, RAI(absorbing), which is analogous to and scaled with transpiring leaf area index (maximum stomatal pore area per unit ground area; LAI(transpiring)), increased proportionally with basal area across the three stands. In contrast, RAI(fine) was inversely propotional to basal area. The ratio of RAI(absorbing) to LAI(transpiring) ranged from 7.7 to 17.1, giving an estimate of the relative aboveground versus belowground resource exchange areas. RAI(absorbing) provides a way of characterizing ecosystem functioning as a physiologically meaningful index of belowground absorbing area.

Chemical burns: our 10-year experience.

A review of 173 patients with chemical burns admitted to our burn unit was carried out during the years 1976-85. Most burns were work related (83 per cent). The majority of patients were men aged 21-50 years (mean age = 29.6 years). The mean total body surface area involved was 3.6 per cent (range = 1-30 per cent). The mean length of stay in hospital was 6.3 days (range = 1-52 days). The extremities were involved in 68 per cent of the patients. The more common aetiological agents were bromine and its compounds (36 per cent), then acids (21 per cent), alkalis and organic substances (14.5 per cent each). The severest burns were caused by the inorganic substances. Delayed admission was most characteristic of the bromine and alkali burns. Complications included local infection (19 cases), systemic infection (two cases), inhalation injury (two cases), tissue necrosis (one case) and corneal erosion (one case). There were no deaths. Increased awareness of the hazardous potential of chemicals should help reduce the incidence of chemical burns.

Suicide attempts by self-immolation--our experience.

Of 5934 patients admitted to our Burns' Unit at the Soroka University Hospital, Beer-Sheva, Israel between the years 1965 and 1986, 22 had attempted suicide by fire (0.37 per cent). Seventeen of them (77 per cent) died from their burns. The use of flammable liquids was the most common method of immolation. Fifty per cent of the victims were known to have previous mental disorders.

The cost of an extensive burn survival.

A 17-year-old male sustained 95 per cent body surface area burns (87 per cent full thickness skin loss). He was hospitalized in the Department of Plastic Surgery that also treats burns. After 232 days he was discharged home when he was functionally independent. He had 16 surgical procedures for excision of burn eschar and skin grafting; received a total of 128 units of blood; 899 units of fresh frozen plasma and had enteral hyperalimentation for 175 days. About 1000 physician-hours, 3000 nurse-hours, 1000 physiotherapy and occupational therapy-hours and about 250 dietician-hours were needed for his treatment. More than 1850 laboratory tests and 120 X-rays were performed, and more than 600 kg of ointment and creams were used, as well as half a ton of topical antimicrobial solutions. Ten different antibiotics were used for a total of 85 treatment days. Some 8500 m of dressing were applied with more than 6000 pieces of petroleum jelly gauze dressing. Hospitalization costs were found to be US$141,750, only 37.5 per cent of which were salaries. An analysis of these costs is given.

Phosphorous pentachloride chemical burn--a slowly healing injury.

A 51-year-old chemical engineer sustained phosphorous pentachloride partial skin thickness burns over 20 per cent of his body surface area. Although macroscopically and microscopically the wound seemed to be superficial, the course of clinical healing of this injury was very slow and painful. Retrospectively this burn should have been treated by early excision and grafting.

Superoxide dismutase (SOD) for mustard gas burns.

Mustard gas (MS) has been used in chemical warfare since World War I. The blistering skin lesions are slow to heal. Secondary inflammation might occur, as well as damage to organs distant from the original wound. Presently there is no specific antidote for burns and poisoning by MS. This study examined treatment modalities with free oxygen radical scavengers, copper-zinc, and manganese superoxide dismutase (SOD), for MS skin burns in an experimental guinea pig model. Each of the SOD compounds reduced dramatically burn lesion area when administered intraperitoneally/intralesionally (i.p./i.l.) before wound infliction. The protective action of the SODs was also evident in the significantly higher histopathological score of biopsies obtained on day 7 from local tissue, caused with the lower dose of MS. When the SOD compounds were administered i.p. 1 hour after burn infliction, and repeated daily for 7 days, no protective effect could be detected under the present experimental conditions.

Oro-maxillofacial skeletal deformities resulting from burn scar contractures of the face and neck.

The deforming forces of the scar contracture associated with burns of the head and neck region involve primarily the skin and secondarily the facial musculoskeletal structures. A case of severe face and neck burn accompanied by extreme facial skeletal deformity is reported. Best results are obtained in patients treated properly and promptly by a team including plastic and maxillofacial surgeons as well as orthodontists.

Full skin thickness burns caused by contact with the pavement in a heat-stroke victim.

A 70-year-old woman, with a previous history of heat-stroke, suffered another heat-stroke on a hot summer day (air temperature 43 degrees C (109 degrees F)). She presented the rare complication of a heat-stroke plus deep burns sustained while lying unconscious on the pavement. In addition to age, obesity, previous illness, incidental fever, drugs, dehydration and physical effort, a previous history of heat-stroke is probably an important risk factor for a second heat-stroke. Burns from contact with the pavement are uncommon but possible, especially if the patient is obese, immobile and poorly insulated.

Maqua (therapeutic burn) as an indicator of underlying disease.

The origin and nature of the maqua (the Arabic therapeutic burn) is presented together with our clinical experience of patients previously treated by this traditional method. Maquas are small deep burns inflicted in areas either in proximity to a diseased organ or in points related traditionally to the original basic problem. These relationships may be rooted in historical ties between old Arab medicine and traditional Oriental, antique Egyptian, and Greco-Roman medicines. Maquas alone only rarely present a threat to the patient, but in many cases they may serve as an indicator of the original underlying disease. This and other folklore treatment modalities, together with the healers themselves, should be acknowledged by us, as markers for health problems or maybe for potential healing methods and doctor-patient relationships.

Anal stenosis with megarectum: an unusual complication of a perineal burn.

A case of a 3-year-old boy with anal stricture and megarectum is described. Overflow incontinence and soiling were corrected by local flaps and skin graft and were maintained by frequent dilatations after downward traction of the whole anus was performed. The options of immediate and late treatment of such burns and the colostomy procedure are discussed.

[Epidural extraskeletal Ewing's sarcoma: the tenth case]. / Sarcome d'Ewing extra-osseux épidural: le dixième cas.

The 10th case of a primary epidural extraskeletal Ewing's sarcoma is presented. The treatment and the relevant literature are reviewed.

[A decade of experience in craniofacial surgery].

Our craniofacial surgery team includes experts from the following fields: plastic surgery, neurosurgery, ophthalmology, genetics, neurology, orthodontics, pedodontics, facial rehabilitation, psychiatry, social work, anesthesiology and intensive care. Craniofacial surgery became to a large extent pediatric surgery, following evidence that careful, early surgery does not impair growth and that development following surgery is almost normal. The malformations that were repaired included those of the Crouzon and Apert syndromes, requiring frontal remodelling and advancement of the middle third of the facial skeleton; hypertelorism in which orbits were moved to the midline; large craniofacial clefts in which the hemiface from either side was moved to the midline; and different types of craniostenosis in which frontal advancement and remodelling with reconstruction of the vault was performed. The series consisted of 78 patients who presented between 1979-1989. 3 illustrative cases are described.