Lung growth after experimental pulmonary transplantation

Replacement of the heart and both lungs or single lung transplantation has been performed in a few cases of terminal (cardio) pulmonary disease in childhood. It remains unclear whether pulmonary allografts will meet the demands of a growing organism. Six domestic pigs (mean body weight, 24 kg) underwent left lung transplantation from donors of equal weight. Immunosuppression consisted of cyclosporine, azathioprine, and corticosteroids. After the pigs doubled their body weight, growth of the lung was assessed by bronchography and pulmonary angiography. In transplant animals it took 11 weeks (normal animals, 6 weeks) for their weight to double. At that time, the bronchial tree showed similar growth when compared with nontransplant animals of equal weight. The diameter of the left lower lobe bronchus (9.2 +/- 0.4 mm) was significantly greater than that of animals of 24 kg body weight (7.5 +/- 0.3 mm; p less than 0.01) but comparable to that of normal pigs of similar weight (9.0 +/- 0.5 mm). The same applied for length of the left lower lobe bronchus (transplants, 95 +/- 6.7 mm; controls 24 kg, 67 +/- 2 mm [p less than 0.01]; controls 48 kg, 93 +/- 3 mm). Similar growth tendencies were observed in the pulmonary vascular tree. The diameter of the left lower lobe artery was 9.4 +/- 98 mm in 48 kg transplant pigs, compared with 9.7 +/- 1.2 mm in 24 kg control pigs and 8.5 +/- 0.8 mm in 48 kg control pigs. In one case of recurrent severe pulmonary rejection, the lung did not grow. We conclude from this study that growth is retarded by immunosuppression.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth of lung allografts after experimental transplantation

Heart and lung transplantation has been performed in cases of end-stage cardiopulmonary disease in infants. Nevertheless, it still remains unclear whether lung allografts adjust to a growing organism. In 6 young domestic pigs unilateral left lung allotransplantation was performed. Immunosuppression consisted of a triple drug therapy including cyclosporine, azathioprine, and corticosteroids. Lung growth was studied by using bronchography, pulmonary angiography, and lung histology. After 11 weeks the transplanted animals had doubled their body weight from 24 kg to 48 kg. Non-transplanted animals in contrast doubled their weight within only 6 weeks. The growth retardation was attributed to the immunosuppressive therapy. The bronchial tree and pulmonary vasculature of lung allografts showed a similar growth potential to non-transplanted lungs in animals of equivalent body weight. In one case of recurrent severe rejection of the lung no growth was observed. Therefore it was concluded that lung allografts grow adequately according to the development of the recipient organism. Lung transplantation in children does not seem to be restricted by a limited growth potential of the graft.

Buttress form of the central African rain forest tree Microberlinia bisulcata, and its possible role in nutrient acquisition

Buttressing is a trait special to tropical trees but explanations for its occurrence remain inconclusive. The two main hypotheses are that they provide structural support and/or promote nutrient acquisition. Studies of the first are common but the second has received much less attention. Architectural measurements were made on adult and juvenile trees of the ectomycorrhizal species Microberlinia bisulcata, in Korup (Cameroon). Buttressing on this species is highly distinctive with strong lateral extension of surface roots of the juveniles leading to a mature buttress system of a shallow spreading form on adults. This contrasts with more vertical buttresses, closer to the stem, found on many other tropical tree species. No clear relationship between main buttress and large branch distribution was found. Whilst this does not argue against the essential structural role of buttresses for these very large tropical trees, the form on M. bisulcata does suggest a likely second role, that of aiding nutrient acquisition. At the Korup site, with its deep sandy soils of very low phosphorus status, and where most nutrient cycling takes place in a thin surface layer of fine roots and mycorrhizas, it appears that buttress form could develop from soil-surface root exploration for nutrients by juvenile trees. It may accordingly allow M. bisulcata to attain the higher greater competitive ability, faster growth rate, and maximum tree size that it does compared with other co-occurring tree species. For sites across the tropics in general, the degree of shallowness and spatial extension of buttresses of the dominant species is hypothesized to increase with decreasing nutrient availability.

Plurality of tree species responses to drought perturbation in Bornean tropical rain forest

Drought perturbation driven by the El Niño Southern Oscillation (ENSO) is a principal stochastic variable determining the dynamics of lowland rain forest in S.E. Asia. Mortality, recruitment and stem growth rates at Danum in Sabah (Malaysian Borneo) were recorded in two 4-ha plots (trees ≥ 10 cm gbh) for two periods, 1986–1996 and 1996–2001. Mortality and growth were also recorded in a sample of subplots for small trees (10 to <50 cm gbh) in two sub-periods, 1996–1999 and 1999–2001. Dynamics variables were employed to build indices of drought response for each of the 34 most abundant plot-level species (22 at the subplot level), these being interval-weighted percentage changes between periods and sub-periods. A significant yet complex effect of the strong 1997/1998 drought at the forest community level was shown by randomization procedures followed by multiple hypothesis testing. Despite a general resistance of the forest to drought, large and significant differences in short-term responses were apparent for several species. Using a diagrammatic form of stability analysis, different species showed immediate or lagged effects, high or low degrees of resilience or even oscillatory dynamics. In the context of the local topographic gradient, species’ responses define the newly termed perturbation response niche. The largest responses, particularly for recruitment and growth, were among the small trees, many of which are members of understorey taxa. The results bring with them a novel approach to understanding community dynamics: the kaleidoscopic complexity of idiosyncratic responses to stochastic perturbations suggests that plurality, rather than neutrality, of responses may be essential to understanding these tropical forests. The basis to the various responses lies with the mechanisms of tree-soil water relations which are physiologically predictable: the timing and intensity of the next drought, however, is not. To date, environmental stochasticity has been insufficiently incorporated into models of tropical forest dynamics, a step that might considerably improve the reality of theories about these globally important ecosystems.

Tree species and diversity effects on soil water seepage in a tropical plantation

Plant diversity has been shown to influence the water cycle of forest ecosystems by differences in water consumption and the associated effects on groundwater recharge. However, the effects of biodiversity on soil water fluxes remain poorly understood for native tree species plantations in the tropics. Therefore, we estimated soil water fluxes and assessed the effects of tree species and diversity on these fluxes in an experimental native tree species plantation in Sardinilla (Panama). The study was conducted during the wet season 2008 on plots of monocultures and mixtures of three or six tree species. Rainfall and soil water content were measured and evapotranspiration was estimated with the Penman-Monteith equation. Soil water fluxes were estimated using a simple soil water budget model considering water input, output, and soil water and groundwater storage changes and in addition, were simulated using the physically based one-dimensional water flow model Hydrus-1D. In general, the Hydrus simulation did not reflect the observed pressure heads, in that modeled pressure heads were higher compared to measured ones. On the other hand, the results of the water balance equation (WBE) reproduced observed water use patterns well. In monocultures, the downward fluxes through the 200 cm-depth plane were highest below Hura crepitans (6.13 mm day−1) and lowest below Luehea seemannii (5.18 mm day−1). The average seepage rate in monocultures (±SE) was 5.66 ± 0.18 mm day−1, and therefore, significantly higher than below six-species mixtures (5.49 ± 0.04 mm day−1) according to overyielding analyses. The three-species mixtures had an average seepage rate of 5.63 ± 0.12 mm day−1 and their values did not differ significantly from the average values of the corresponding species in monocultures. Seepage rates were driven by the transpiration of the varying biomass among the plots (r = 0.61, p = 0.017). Thus, a mixture of trees with different growth rates resulted in moderate seepage rates compared to monocultures of either fast growing or slow growing tree species. Our results demonstrate that tree-species specific biomass production and tree diversity are important controls of seepage rates in the Sardinilla plantation during the wet season.

Growth response to climate and drought change along an aridity gradient in the southernmost Pinus nigra relict forests

Tree populations at the rear edge of species distribution are sensitive to climate stress and drought. However, growth responses of these tree populations to those stressors may vary along climatic gradients. To analyze growth responses to climate and drought using dendrochronology in rear-edge Pinus nigra populations located along an aridity gradient. Tree-ring width chronologies were built for the twentieth century and related to monthly climatic variables, a drought index (Standardized Precipitation-Evapotranspiration Index), and two atmospheric circulation patterns (North Atlantic and Western Mediterranean Oscillations). Growth was enhanced by wet and cold previous autumns and warm late winters before tree-ring formation. The influence of the previous year conditions on growth increased during the past century. Growth was significantly related to North Atlantic and Western Mediterranean Oscillations in two out of five sites. The strongest responses of growth to the drought index were observed in the most xeric sites. Dry conditions before tree-ring formation constrain growth in rear-edge P. nigra populations. The comparisons of climate-growth responses along aridity gradients allow characterizing the sensitivity of relict stands to climate warming.

Counting scars on tree stems to assess rockfall hazards: A low effort approach, but how reliable?

Rockfall is a widespread and hazardous process in mountain environments, but data on past events are only rarely available. Growth-ring series from trees impacted by rockfall were successfully used in the past to overcome the lack of archival records. Dendrogeomorphic techniques have been demonstrated to allow very accurate dating and reconstruction of spatial and temporal rockfall activity, but the approach has been cited to be labor intensive and time consuming. In this study, we present a simplified method to quantify rockfall processes on forested slopes requiring less time and efforts. The approach is based on a counting of visible scars on the stem surface of Common beech (Fagus sylvatica L.). Data are presented from a site in the Inn valley (Austria), where rocks are frequently detached from an ~ 200-m-high, south-facing limestone cliff. We compare results obtained from (i) the “classical” analysis of growth disturbances in the tree-ring series of 33 Norway spruces (Picea abies (L.) Karst.) and (ii) data obtained with a scar count on the stem surface of 50 F. sylvatica trees. A total of 277 rockfall events since A.D. 1819 could be reconstructed from tree-ring records of P. abies, whereas 1140 scars were observed on the stem surface of F. sylvatica. Absolute numbers of rockfalls (and hence return intervals) vary significantly between the approaches, and the mean number of rockfalls observed on the stem surface of F. sylvatica exceeds that of P. abies by a factor of 2.7. On the other hand, both methods yield comparable data on the spatial distribution of relative rockfall activity. Differences may be explained by a great portion of masked scars in P. abies and the conservation of signs of impacts on the stem of F. sylvatica. Besides, data indicate that several scars on the bark of F. sylvatica may stem from the same impact and thus lead to an overestimation of rockfall activity.

Precipitation over the past four centuries in the Dieshan Mountains as inferred from tree rings: An introduction to an HHT-based method

To improve our understanding of the Asian monsoon system, we developed a hydroclimate reconstruction in a marginal monsoon shoulder region for the period prior to the industrial era. Here, we present the first moisture sensitive tree-ring chronology, spanning 501 years for the Dieshan Mountain area, a boundary region of the Asian summer monsoon in the northeastern Tibetan Plateau. This reconstruction was derived from 101 cores of 68 old-growth Chinese pine (Pinus tabulaeformis) trees. We introduce a Hilbert–Huang Transform (HHT) based standardization method to develop the tree-ring chronology, which has the advantages of excluding non-climatic disturbances in individual tree-ring series. Based on the reliable portion of the chronology, we reconstructed the annual (prior July to current June) precipitation history since 1637 for the Dieshan Mountain area and were able to explain 41.3% of the variance. The extremely dry years in this reconstruction were also found in historical documents and are also associated with El Niño episodes. Dry periods were reconstructed for 1718–1725, 1766–1770 and 1920–1933, whereas 1782–1788 and 1979–1985 were wet periods. The spatial signatures of these events were supported by data from other marginal regions of the Asian summer monsoon. Over the past four centuries, out-of-phase relationships between hydroclimate variations in the Dieshan Mountain area and far western Mongolia were observed during the 1718–1725 and 1766–1770 dry periods and the 1979–1985 wet period.

Declining pine growth in Central Spain coincides with increasing diurnal temperature range since the 1970s

Growing evidence suggests environmental change to be most severe across the semi-arid subtropics, with past, present and projected drying of the Mediterranean Basin posing a key multidisciplinary challenge. Consideration of a single climatic factor, however, often fails to explain spatiotemporal growth dynamics of drought-prone ecosystems. Here, we present annually resolved and absolutely dated ring width measurements of 871 Scots pines (Pinus sylvestris) from 18 individual plot sites in the Central Spanish Pinar Grande forest reserve. Although comprising tree ages from 6 to 175 years, this network correlates surprisingly well with the inverse May–July diurnal temperature range (r = 0.84; p < 0.00011956–2011). Ring width extremes were triggered by pressure anomalies of the North Atlantic Oscillation, and the long-term growth decline coincided with Iberian-wide drying since the mid-1970s. Climate model simulations not only confirm this negative trend over the last decades but also project drought to continuously increase over the 21st century. Associated ecological effects and socio-economic consequences should be considered to improve adaptation strategies of agricultural and forest management, as well as biodiversity conservation and ecosystem service.

Site- and species-specific responses of forest growth to climate across the European continent

Aim To evaluate the climate sensitivity of model-based forest productivity estimates using a continental-scale tree-ring network. Location Europe and North Africa (30–70° N, 10° W–40° E). Methods We compiled close to 1000 annually resolved records of radial tree growth for all major European tree species and quantified changes in growth as a function of historical climatic variation. Sites were grouped using a neural network clustering technique to isolate spatiotemporal and species-specific climate response patterns. The resulting empirical climate sensitivities were compared with the sensitivities of net primary production (NPP) estimates derived from the ORCHIDEE-FM and LPJ-wsl dynamic global vegetation models (DGVMs). Results We found coherent biogeographic patterns in climate response that depend upon (1) phylogenetic controls and (2) ambient environmental conditions delineated by latitudinal/elevational location. Temperature controls dominate forest productivity in high-elevation and high-latitude areas whereas moisture sensitive sites are widespread at low elevation in central and southern Europe. DGVM simulations broadly reproduce the empirical patterns, but show less temperature sensitivity in the boreal zone and stronger precipitation sensitivity towards the mid-latitudes. Main conclusions Large-scale forest productivity is driven by monthly to seasonal climate controls, but our results emphasize species-specific growth patterns under comparable environmental conditions. Furthermore, we demonstrate that carry-over effects from the previous growing season can significantly influence tree growth, particularly in areas with harsh climatic conditions – an element not considered in most current-state DGVMs. Model–data discrepancies suggest that the simulated climate sensitivity of NPP will need refinement before carbon-cycle climate feedbacks can be accurately quantified.

Climatic drivers of hourly to yearly tree radius variations along a 6°C natural warming gradient

Climate affects the timing, rate and dynamics of tree growth, over time scales ranging from seconds to centuries. Monitoring how a tree's stem radius varies over these time scales can provide insight into intra-annual stem dynamics and improve our understanding of climate impacts on tree physiology and growth processes. Here, we quantify the response of radial conifer stem size to environmental fluctuations via a novel assessment of tree circadian cycles. We analyze four years of sub-hourly data collected from 56 larch and spruce trees growing along a natural temperature gradient of ∼6 °C in the central Swiss Alps. During the growing season, tree stem diameters were greatest at mid-morning and smallest in the late evening, reflecting the daily cycle of water uptake and loss. Along the gradient, amplitudes calculated from the stem radius cycle were ∼50% smaller at the upper site (∼2200 m a.s.l.) relative to the lower site (∼800 m a.s.l.). We show changes in precipitation, temperature and cloud cover have a substantial effect on typical growing season diurnal cycles; amplitudes were nine times smaller on rainy days (>10 mm), and daily amplitudes are approximately 40% larger when the mean daily temperature is 15–20 °C than when it is 5–10 °C. We find that over the growing season in the sub-alpine forests, spruce show greater daily stem water movement than larch. However, under projected future warming, larch could experience up to 50% greater stem water use, which may severely affect future growth on already dry sites. Our data further indicate that because of the confounding influences of radial growth and short-term water dynamics on stem size, conventional methodology probably overstates the effect of water-linked meteorological variables (i.e. precipitation and relative humidity) on intra-annual tree growth. We suggest future studies use intra-seasonal measurements of cell development and consider whether climatic factors produce reversible changes in stem diameter. These study design elements may help researchers more accurately quantify and attribute changes in forest productivity in response to future warming.

Spontaneous peristaltic airway contractions propel lung liquid through the bronchial tree of intact and fetal lung explants

Spontaneous contractions of the fetal airways are a well recognized but poorly characterized phenomenon. In the present study spontaneous narrowing of the airways was analyzed in freshly isolated lungs from early to late gestation in fetal pigs and rabbits and in cultured fetal mouse lungs. Propagating waves of contraction traveling proximal to distal were observed in fresh lungs throughout gestation which displaced the lung liquid along the lumen. In the pseudoglandular and canalicular stages (fetal pigs) the frequency ranged from 2.3 to 3.3 contractions/min with a 39 to 46% maximum reduction of lumen diameter. In the saccular stage (rabbit) the frequency was 10 to 12/min with a narrowing of approximately 30%. In the organ cultures the waves of narrowing started at the trachea in whole lungs, or at the main bronchus in lobes (5.2 +/- 1.5 contractions/min, 22 +/- 8% reduction of lumen diameter), and as they proceeded distally along the epithelial tubes the luminal liquid was shifted toward the terminal tubules, which expanded the endbuds. As the tubules relaxed the flow of liquid was reversed. Thus the behavior of airway smooth muscle in the fetal lung is phasic in type (like gastrointestinal muscle) in contrast to that in postnatal lung, where it is tonic. An intraluminal positive pressure of 2.33 +/- 0.77 cm H(2)O was recorded in rabbit fetal trachea. It is proposed that the active tone of the smooth muscle maintains the positive intraluminal pressure and acts as a stimulus to lung growth via the force exerted across the airway wall and adjacent parenchyma. The expansion of the compliant endbuds by the fluid shifts at the airway tip may promote their growth into the surrounding mesenchyme.

Herbivores differentially limit the seedling growth and sapling recruitment of two dominant rain forest trees

Resource heterogeneity may influence how plants are attacked and respond to consumers in multiple ways. Perhaps a better understanding of how this interaction might limit sapling recruitment in tree populations may be achieved by examining species’ functional responses to herbivores on a continuum of resource availability. Here, we experimentally reduced herbivore pressure on newly established seedlings of two dominant masting trees in 40 canopy gaps, across c. 80 ha of tropical rain forest in central Africa (Korup, Cameroon). Mesh cages were built to protect individual seedlings, and their leaf production and changes in height were followed for 22 months. With more light, herbivores increasingly prevented the less shade-tolerant Microberlinia bisulcata from growing as tall as it could and producing more leaves, indicating an undercompensation. The more shade-tolerant Tetraberlinia bifoliolata was much less affected by herbivores, showing instead near to full compensation for leaf numbers, and a negligible to weak impact of herbivores on its height growth. A stage-matrix model that compared control and caged populations lent evidence for a stronger impact of herbivores on the long-term population dynamics of M. bisulcata than T. bifoliolata. Our results suggest that insect herbivores can contribute to the local coexistence of two abundant tree species at Korup by disproportionately suppressing sapling recruitment of the faster-growing dominant via undercompensation across the light gradient created by canopy disturbances. The functional patterns we have documented here are consistent with current theory, and, because gap formations are integral to forest regeneration, they may be more widely applicable in other tropical forest communities. If so, the interaction between life-history and herbivore impact across light gradients may play a substantial role in tree species coexistence.

Modeling tree water deficit from microclimate: an approach to quantifying drought stress

Tree water deficit estimated by measuring water-related changes in stem radius (DeltaW) was compared with tree water deficit estimated from the output of a simple, physiologically reasonable model (DeltaW(E)), with soil water potential (Psi(soil)) and atmospheric vapor pressure deficit (VPD) as inputs. Values of DeltaW were determined by monitoring stem radius changes with dendrometers and detrending the results for growth, We followed changes in DeltaW and DeltaW(E) in Pinus sylvestris L. and Quercus pubescens Willd. over 2 years at a dry site (2001-2002; Salgesch, Wallis) and in Picea abies (L.) Karst. for 1 year at a wet site (1998; Davos, Graubuenden) in the Swiss Alps. The seasonal courses of DeltaW in deciduous species and in conifers at the same site were similar and could be largely explained by variation in DeltaW(E). This finding strongly suggests that DeltaW, despite the known species-specific differences in stomatal response to microclimate, is mainly explained by a combination of atmospheric and soil conditions. Consequently, we concluded that trees are unable to maintain any particular DeltaW. Either Psi(soil) or VPD alone provided poorer estimates of AWthan a model incorporating both factors. As a first approximation of DeltaW(E), Psi(soil) can be weighted so that the negative mean Psi(soil) reaches 65 to 75% of the positive mean daytime VPD over a season (Q. pubescens: similar to65%, P abies: similar to70%, P sylvestris: similar to75%). The differences in DeltaW among species can be partially explained by a different weighting of Psi(soil) against VPD. The DeltaW of P. sylvestris was more dependent on Psi(soil) than that of Q. pubescens, but less than that of P. abies, and was less dependent on VPD than that of P. abies and Q. pubescens. The model worked well for P. abies at the wet site and for Q. pubescens and P. sylvestris at the dry site, and may be useful for estimating water deficit in other tree species.