Tree demographic strategies largely overlap across succession in Neotropical wet and dry forest communities

Secondary tropical forests play an increasingly important role in carbon budgets and biodiversity conservation. Understanding successional trajectories is therefore imperative for guiding forest restoration and climate change mitigation efforts. Forest succession is driven by the demographic strategies-combinations of growth, mortality and recruitment rates-of the tree species in the community. However, our understanding of demographic diversity in tropical tree species stems almost exclusively from old-growth forests. Here, we assembled demographic information from repeated forest inventories along chronosequences in two wet (Costa Rica, Panama) and two dry (Mexico) Neotropical forests to assess whether the ranges of demographic strategies present in a community shift across succession. We calculated demographic rates for >500 tree species while controlling for canopy status to compare demographic diversity (i.e., the ranges of demographic strategies) in early successional (0-30 years), late successional (30-120 years) and old-growth forests using two-dimensional hypervolumes of pairs of demographic rates. Ranges of demographic strategies largely overlapped across successional stages, and early successional stages already covered the full spectrum of demographic strategies found in old-growth forests. An exception was a group of species characterized by exceptionally high mortality rates that was confined to early successional stages in the two wet forests. The range of demographic strategies did not expand with succession. Our results suggest that studies of long-term forest monitoring plots in old-growth forests, from which most of our current understanding of demographic strategies of tropical tree species is derived, are surprisingly representative of demographic diversity in general, but do not replace the need for further studies in secondary forests.

Soil resistance and recovery during neotropical forest succession

The recovery of soil conditions is crucial for successful ecosystem restoration and, hence, for achieving the goals of the UN Decade on Ecosystem Restoration. Here, we assess how soils resist forest conversion and agricultural land use, and how soils recover during subsequent tropical forest succession on abandoned agricultural fields. Our overarching question is how soil resistance and recovery depend on local conditions such as climate, soil type and land-use history. For 300 plots in 21 sites across the Neotropics, we used a chronosequence approach in which we sampled soils from two depths in old-growth forests, agricultural fields (i.e. crop fields and pastures), and secondary forests that differ in age (1-95 years) since abandonment. We measured six soil properties using a standardized sampling design and laboratory analyses. Soil resistance strongly depended on local conditions. Croplands and sites on high-activity clay (i.e. high fertility) show strong increases in bulk density and decreases in pH, carbon (C) and nitrogen (N) during deforestation and subsequent agricultural use. Resistance is lower in such sites probably because of a sharp decline in fine root biomass in croplands in the upper soil layers, and a decline in litter input from formerly productive old-growth forest (on high-activity clays). Soil recovery also strongly depended on local conditions. During forest succession, high-activity clays and croplands decreased most strongly in bulk density and increased in C and N, possibly because of strongly compacted soils with low C and N after cropland abandonment, and because of rapid vegetation recovery in high-activity clays leading to greater fine root growth and litter input. Furthermore, sites at low precipitation decreased in pH, whereas sites at high precipitation increased in N and decreased in C : N ratio. Extractable phosphorus (P) did not recover during succession, suggesting increased P limitation as forests age. These results indicate that no single solution exists for effective soil restoration and that local site conditions should determine the restoration strategies. This article is part of the theme issue 'Understanding forest landscape restoration: reinforcing scientific foundations for the UN Decade on Ecosystem Restoration'.

Strong floristic distinctiveness across Neotropical successional forests

Forests that regrow naturally on abandoned fields are important for restoring biodiversity and ecosystem services, but can they also preserve the distinct regional tree floras? Using the floristic composition of 1215 early successional forests (≤20 years) in 75 human-modified landscapes across the Neotropic realm, we identified 14 distinct floristic groups, with a between-group dissimilarity of 0.97. Floristic groups were associated with location, bioregions, soil pH, temperature seasonality, and water availability. Hence, there is large continental-scale variation in the species composition of early successional forests, which is mainly associated with biogeographic and environmental factors but not with human disturbance indicators. This floristic distinctiveness is partially driven by regionally restricted species belonging to widespread genera. Early secondary forests contribute therefore to restoring and conserving the distinctiveness of bioregions across the Neotropical realm, and forest restoration initiatives should use local species to assure that these distinct floras are maintained.

Multidimensional tropical forest recovery

[Figure: see text].

Functional recovery of secondary tropical forests

One-third of all Neotropical forests are secondary forests that regrow naturally after agricultural use through secondary succession. We need to understand better how and why succession varies across environmental gradients and broad geographic scales. Here, we analyze functional recovery using community data on seven plant characteristics (traits) of 1,016 forest plots from 30 chronosequence sites across the Neotropics. By analyzing communities in terms of their traits, we enhance understanding of the mechanisms of succession, assess ecosystem recovery, and use these insights to propose successful forest restoration strategies. Wet and dry forests diverged markedly for several traits that increase growth rate in wet forests but come at the expense of reduced drought tolerance, delay, or avoidance, which is important in seasonally dry forests. Dry and wet forests showed different successional pathways for several traits. In dry forests, species turnover is driven by drought tolerance traits that are important early in succession and in wet forests by shade tolerance traits that are important later in succession. In both forests, deciduous and compound-leaved trees decreased with forest age, probably because microclimatic conditions became less hot and dry. Our results suggest that climatic water availability drives functional recovery by influencing the start and trajectory of succession, resulting in a convergence of community trait values with forest age when vegetation cover builds up. Within plots, the range in functional trait values increased with age. Based on the observed successional trait changes, we indicate the consequences for carbon and nutrient cycling and propose an ecologically sound strategy to improve forest restoration success.

Forest cover mediates large and medium-sized mammal occurrence in a critical link of the Mesoamerican Biological Corridor

Connectivity of natural areas through biological corridors is essential for ecosystem resilience and biodiversity conservation. However, robust assessments of biodiversity in corridor areas are often hindered by logistical constraints and the statistical challenges of modeling data from multiple species. Herein, we used a hierarchical community occupancy model in a Bayesian framework to evaluate the status of medium and large-sized mammals in a critical link of the Mesoamerican Biological Corridor (MBC) in Costa Rica. We used camera traps deployed from 2013-2017 to detect 18 medium (1-15 kg) and 6 large (>15 kg) mammal species in a portion of two Jaguar Conservation Units (JCUs) and the Corridor linking them. Camera traps operated for 16,904 trap nights across 209 stations, covering an area of 880 km2. Forest cover was the most important driver of medium and large-sized mammal habitat use, with forest specialists such as jaguars (Panthera onca) and pumas (Puma concolor) strongly associated with high forest cover, while habitat generalists such as coyotes (Canis latrans) and raccoons (Procyon lotor) were associated with low forest cover. Medium and large-sized mammal species richness was lower in the Corridor area ([Formula: see text] = 9.78±1.84) than in the portions evaluated of the two JCUs ([Formula: see text] = 11.50±1.52). Puma and jaguar habitat use probabilities were strongly correlated with large prey species richness (jaguar, r = 0.59, p<0.001; puma, r = 0.72, p<0.001), and correlated to a lesser extent with medium prey species richness (jaguar, r = 0.36, p = 0.003; puma, r = 0.23, p = 0.064). Low estimated jaguar habitat use probability in one JCU (Central Volcanic Cordillera: [Formula: see text] = 0.15±0.11) suggests that this is not the jaguar stronghold previously assumed. In addition, the western half of the Corridor has low richness of large mammals, making it necessary to take urgent actions to secure habitat connectivity for mammal populations.

TRY plant trait database - enhanced coverage and open access

Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.

Disturbance and the elevation ranges of woody plant species in the mountains of Costa Rica

AIM

To understand how disturbance-here defined as a transient reduction in competition-can shape plant distributions along elevation gradients. Theory suggests that disturbance may increase elevation ranges, especially at the lower range limits, through reduced competitive exclusion. Nevertheless, to date this relationship remains unclear.

LOCATION

Mountains of Costa Rica.

METHODS

We compared the elevation range of woody stems over 10 cm dbh ("trees") observed in plots along two transects spanning a range of elevations in secondary (regrowth) and old-growth forest (409 and 249 species, respectively). We also estimated these elevation ranges using nationwide data. In addition, we examined the influence of stem size and plot scale basal area (as a measure of competition) on species elevation range limits in the two gradients.

RESULTS

In general, tree species ranges increased with elevation. Species in the secondary forest had broader elevation ranges (100-318 m broader than species in the old-growth forest; Wilcoxon: p-value <.001). Also, in the secondary transect, individuals with greater diameters had broader elevation ranges than those observed as smaller trees (137 m broader; Kruskal-Wallis: p-value = .03). The lower range limit of species occurred more frequently in plots with lower (vs. higher) basal area than expected by chance in both forest types. We also observed higher elevation upper limits in old growth, but not in secondary forests, with lower (vs. higher) basal area.

MAIN CONCLUSION

Disturbance relaxes the constraints imposed by competition and extends effective elevation ranges of species, particularly those in secondary forest, to warmer and cooler climates (minimum increase equivalent to about 0.6-1.4°C). Thus, suitable disturbance may assist species persistence under climate change. We believe this is the first study indicating a consistent relation between disturbance and woody plant species distributions along elevation gradients.

Drivers of tropical rainforest composition and alpha diversity patterns over a 2,520 m altitudinal gradient

AIM

We sought to determine the relationship of forest composition and alpha diversity (the species diversity of a local assemblage) to altitude, soil, and spatial factors over a 440-2,950 m a.s.l gradient.

LOCATION

Altitudinal gradient on the Caribbean slope of the Talamanca Cordillera, Costa Rica.

TAXON

Angiosperm and gymnosperm trees, palms, and tree ferns.

METHODS

We measured and identified all stems ≥10 cm dbh in 32 0.25-ha undisturbed rain forest plots over the gradient. We determined compositional patterns using Non-Metric Multidimensional Scaling (NMS) ordination, and used linear regressions to explore the relationship between four alpha diversity metrics and altitude. With variation partitioning (VARPART), we determined the compositional variation explained by altitude, soil, and spatial variables quantified using Principle Components of Neighbor matrices.

RESULTS

We identified 425 species. NMS axis 1 separated a lowland zone (440-1,120 m asl) from a transitional one dominated by holarctic Oreomunnea mexicana (1,400-1,600 m asl) and Quercus-dominated forests at altitudes >2,100 m asl. The lowland zone was separated into two clusters of plots on NMS axis 2, the first in the 430-620 m asl range and the second at 1,000-1,120 masl. Regressions showed that all alpha diversity metrics were strongly negatively related to altitude (R 2 > 0.78). Overall, adjusted R 2 from VARPART was 0.43, with 0.30, 0.21, and 0.17 for altitude, soil, and space respectively. The respective adjusted R 2 of individual matrices, on controlling for the other two, was 0.06, 0.05 and 0.09 (p < 0.001).

MAIN CONCLUSIONS

There are two well-defined forest compositional zones on this gradient-lowlands 430-1,120 m asl and montane forests >2,150 m asl-with a transitional zone at 1,400-1,600 m asl, where lowland tropical and montane holarctic species are found together. Montane forests are very distinct in their composition and low alpha diversity. Vegetation and soil respond to altitude, and therefore temperature, as an integrated system, a model that goes beyond niche assembly as shown by the significant effect of space in the VARPART.

Biodiversity recovery of Neotropical secondary forests

Old-growth tropical forests harbor an immense diversity of tree species but are rapidly being cleared, while secondary forests that regrow on abandoned agricultural lands increase in extent. We assess how tree species richness and composition recover during secondary succession across gradients in environmental conditions and anthropogenic disturbance in an unprecedented multisite analysis for the Neotropics. Secondary forests recover remarkably fast in species richness but slowly in species composition. Secondary forests take a median time of five decades to recover the species richness of old-growth forest (80% recovery after 20 years) based on rarefaction analysis. Full recovery of species composition takes centuries (only 34% recovery after 20 years). A dual strategy that maintains both old-growth forests and species-rich secondary forests is therefore crucial for biodiversity conservation in human-modified tropical landscapes.

Comparative landscape genetics of two frugivorous bats in a biological corridor undergoing agricultural intensification

Agricultural intensification in tropical landscapes poses a new threat to the ability of biological corridors to maintain functional connectivity for native species. We use a landscape genetics approach to evaluate impacts of expanding pineapple plantations on two widespread and abundant frugivorous bats in a biological corridor in Costa Rica. We hypothesize that the larger, more mobile Artibeus jamaicensis will be less impacted by pineapple than the smaller Carollia castanea. In 2012 and 2013, we sampled 735 bats in 26 remnant forest patches surrounded by different proportions of forest, pasture, crops and pineapple. We used 10 microsatellite loci for A. jamaicensis and 16 microsatellite loci for C. castanea to estimate genetic diversity and gene flow. Canonical correspondence analyses indicate that land cover type surrounding patches has no impact on genetic diversity of A. jamaicensis. However, for C. castanea, both percentage forest and pineapple surrounding patches explained a significant proportion of the variation in genetic diversity. Least-cost transect analyses (LCTA) and pairwise G″st suggest that for A. jamaicensis, pineapple is more permeable to gene flow than expected, while as expected, forest is the most permeable land cover for gene flow of C. castanea. For both species, LCTA indicate that development may play a role in inhibiting gene flow. The current study answers the call for landscape genetic research focused on tropical and agricultural landscapes, highlights the value of comparative landscape genetics in biological corridor design and management and is one of the few studies of biological corridors in any ecosystem to implement a genetic approach to test corridor efficacy.

Successional dynamics in Neotropical forests are as uncertain as they are predictable

Although forest succession has traditionally been approached as a deterministic process, successional trajectories of vegetation change vary widely, even among nearby stands with similar environmental conditions and disturbance histories. Here, we provide the first attempt, to our knowledge, to quantify predictability and uncertainty during succession based on the most extensive long-term datasets ever assembled for Neotropical forests. We develop a novel approach that integrates deterministic and stochastic components into different candidate models describing the dynamical interactions among three widely used and interrelated forest attributes--stem density, basal area, and species density. Within each of the seven study sites, successional trajectories were highly idiosyncratic, even when controlling for prior land use, environment, and initial conditions in these attributes. Plot factors were far more important than stand age in explaining successional trajectories. For each site, the best-fit model was able to capture the complete set of time series in certain attributes only when both the deterministic and stochastic components were set to similar magnitudes. Surprisingly, predictability of stem density, basal area, and species density did not show consistent trends across attributes, study sites, or land use history, and was independent of plot size and time series length. The model developed here represents the best approach, to date, for characterizing autogenic successional dynamics and demonstrates the low predictability of successional trajectories. These high levels of uncertainty suggest that the impacts of allogenic factors on rates of change during tropical forest succession are far more pervasive than previously thought, challenging the way ecologists view and investigate forest regeneration.

Concepts and a methodology for evaluating environmental services from trees of small farms in Chiapas, México

We propose a methodology to estimate the environmental service (ES) value of small farms in Chiapas, Mexico, involving trained farmers-promoters in field sampling. We considered the ways in which the landscape's principal organisms, the trees, contribute to ES. We proposed a species functional value (FV) index based on their functional traits and key ecological characteristics, and estimated each site's ES value using FV weighted by the dimensions and abundance of individuals in different land uses (LU). Tree contribution to carbon storage (C) was defined using species wood density and biodiversity conservation value (BD) using food and habitat provision for wildlife and species existence (non-use) value (EX). Many species and individuals had high C, as wind-dispersed species with dense wood were common, but low BD prevailed, with high BD species common only in riparian forests. Few species and fewer individuals had high EX conferred by dense wood, large size, harvesting pressure and animal dispersal, among others. High variance in value within LU types, suggested that LU is a poor estimator of ES value, and that the measurement of species FV and tree dimensions is essential. This tool accurately reflects the ecological values of farm tree cover, allowing negotiation of compensation for environmental services. This methodology could be implemented combining open-access regional traits databases and field sampling by local people, and can easily be adapted for the measurement of other ES, and to other ecological and cultural contexts.

Pattern and process in neotropical secondary rain forests: the first 100 years of succession

More and more areas of deforested wet tropical lands are being handed back to nature as their erstwhile owners abandon attempts to farm them. The resulting secondary successions offer hope that some of the unique characteristics of the original rain forests may be recovered and conserved. However, most of our understanding of what secondary tropical rain forests are and how and why they develop is limited to the first decade of a process that may last for centuries. A longer-term view indicates that the causes of change in neotropical secondary successions are similar to those operating in temperate forests, but yields sobering conclusions for conservation.

[Tropical forest restoration in Costa Rica: the effect of several strategies on litter production, accumulation and decomposition]

Tropical forest restoration strategies have the potential to accelerate the recovery of the nutrient cycles in degraded lands. Litter production and its decomposition represent the main transfer of organic material and nutrients into the soil substrate. We evaluated litter production, accumulation on the forest floor, and its decomposition under three restoration strategies: plantation (entire area planted with trees), island (trees planted in patches of three different sizes) and control (natural regeneration) plots. We also compared restoration strategies to young secondary forest (7-9 yr). Restoration treatments were established in 50 x 50m plots in June 2004 at six sites in Southern Costa Rica. Planted tree species included two native timber species (Terminalia amazonia and Vochysia guatemalensis) interplanted with two N fixers (Erythrina poeppigiana and Inga edulis). Litter was collected every 15 days between September 2008 and August 2009 in 12 0.25m2 litter traps distributed within each plot; litter that accumulated on the soil surface was collected at four locations (0.25m2 quadrats) within each plot in February and May 2009. Total litter production in plantation (6.3Mg/ha) and secondary forest (7.3Mg/ha) did not differ, but were greater than in islands (3.5Mg/ha) and control (1.4 Mg/ha). Plantation had greatest accumulation of litter on the soil surface (10.6 Mg/ha) as compared to the other treatments (SF = 7.2; I = 6.7; C = 4.9). Secondary forest was the only treatment with a greater annual production of litter than litter accumulation on the soil surface. Carbon storage in litter was similar between plantation and secondary forest, and significantly greater than the other treatments. No differences were found for carbon concentration and storage in the soil among treatments. There was also high variability in the production and accumulation of litter and carbon among sites. Active restoration treatments accelerated the production of litter and carbon storage in comparison to areas under natural recovery. However, the nutrient cycle has not necessarily been restored under these conditions, as high litter accumulation on the soil surface indicates a low decomposition rate, which slows nutrient return to the soil.

A novel statistical method for classifying habitat generalists and specialists

We develop a novel statistical approach for classifying generalists and specialists in two distinct habitats. Using a multinomial model based on estimated species relative abundance in two habitats, our method minimizes bias due to differences in sampling intensities between two habitat types as well as bias due to insufficient sampling within each habitat. The method permits a robust statistical classification of habitat specialists and generalists, without excluding rare species a priori. Based on a user-defined specialization threshold, the model classifies species into one of four groups: (1) generalist; (2) habitat A specialist; (3) habitat B specialist; and (4) too rare to classify with confidence. We illustrate our multinomial classification method using two contrasting data sets: (1) bird abundance in woodland and heath habitats in southeastern Australia and (2) tree abundance in second-growth (SG) and old-growth (OG) rain forests in the Caribbean lowlands of northeastern Costa Rica. We evaluate the multinomial model in detail for the tree data set. Our results for birds were highly concordant with a previous nonstatistical classification, but our method classified a higher fraction (57.7%) of bird species with statistical confidence. Based on a conservative specialization threshold and adjustment for multiple comparisons, 64.4% of tree species in the full sample were too rare to classify with confidence. Among the species classified, OG specialists constituted the largest class (40.6%), followed by generalist tree species (36.7%) and SG specialists (22.7%). The multinomial model was more sensitive than indicator value analysis or abundance-based phi coefficient indices in detecting habitat specialists and also detects generalists statistically. Classification of specialists and generalists based on rarefied subsamples was highly consistent with classification based on the full sample, even for sampling percentages as low as 20%. Major advantages of the new method are (1) its ability to distinguish habitat generalists (species with no significant habitat affinity) from species that are simply too rare to classify and (2) applicability to a single representative sample or a single pooled set of representative samples from each of two habitat types. The method as currently developed can be applied to no more than two habitats at a time.

Rates of change in tree communities of secondary Neotropical forests following major disturbances

Rates of change in tree communities following major disturbances are determined by a complex set of interactions between local site factors, landscape history and structure, regional species pools and species life histories. Our analysis focuses on vegetation change following abandonment of agricultural fields or pastures, as this is the most extensive form of major disturbance in Neotropical forests. We consider five tree community attributes: stem density, basal area, species density, species richness and species composition. We describe two case studies, in northeastern Costa Rica and Chiapas, Mexico, where both chronosequence and annual tree dynamics studies are being applied. These case studies show that the rates of change in tree communities often deviate from chronosequence trends. With respect to tree species composition, sites of different ages differ more than a single site followed over time through the same age range. Dynamic changes in basal area within stands, on the other hand, generally followed chronosequence trends. Basal area accumulation was more linked with tree growth rates than with net changes in tree density due to recruitment and mortality. Stem turnover rates were poor predictors of species turnover rates, particularly at longer time-intervals. Effects of the surrounding landscape on tree community dynamics within individual plots are poorly understood, but are likely to be important determinants of species accumulation rates and relative abundance patterns.

A phase II dose-response study of hemoglobin raffimer (Hemolink) in elective coronary artery bypass surgery

BACKGROUND

We performed this study to determine the dose-response of hemoglobin raffimer administered in conjunction with intraoperative autologous donation in patients undergoing coronary artery bypass grafting surgery. A secondary objective was to evaluate hemoglobin raffimer for reducing the incidence of allogeneic red blood cell transfusions.

METHODS

This was a phase II, single-blind, multicenter, placebo-controlled, open-label study. Patients undergoing coronary artery bypass grafting with cardiopulmonary bypass and intraoperative autologous donation were randomized to receive a single dose of hemoglobin raffimer or control (10% pentastarch). Patients were sequentially enrolled in a dose block of 250, 500, 750, and 1000 mL.

RESULTS

Sixty patients received hemoglobin raffimer (n = 30) or control (n = 30). Hemoglobin raffimer was well tolerated. Most (98%) adverse events were mild or moderate in severity. There was an expected dose-dependent increase in the incidence of blood pressure increases and jaundice in hemoglobin raffimer-treated patients. In a dose-pooled analysis of hemoglobin raffimer versus control, increased blood pressure (43% vs 17%), nausea (37% vs 33%), and atrial fibrillation (37% vs 17%) were the most frequently reported adverse events. All serious adverse events were considered unrelated or unlikely to be related to study drug. No hemoglobin raffimer-treated patient required an intraoperative allogeneic red blood cell transfusion, compared with 5 (17%) pentastarch-treated patients (P =.052). This advantage of hemoglobin raffimer was maintained at 24 hours after surgery (7% vs 37%; P =.010) and up to 5 days after surgery (10% vs 47%; P =.0034).

CONCLUSIONS

Hemoglobin raffimer was not associated with any serious adverse events in patients undergoing primary coronary artery bypass grafting with cardiopulmonary bypass and intraoperative autologous donation in a dose-response study up to 1000 mL. Hemoglobin raffimer was effective in facilitating decreased exposure or avoidance of allogeneic red blood cell transfusions when used in conjunction with intraoperative autologous donation.

The efficacy and resource utilization of remifentanil and fentanyl in fast-track coronary artery bypass graft surgery: a prospective randomized, double-blinded controlled, multi-center trial

We compared (a) the perioperative complications; (b) times to eligibility for, and actual time of the following: extubation, less intense monitoring, intensive care unit (ICU), and hospital discharge; and (c) resource utilization of nursing ratio for patients receiving either a typical fentanyl/isoflurane/propofol regimen or a remifentanil/isoflurane/propofol regimen for fast-track cardiac anesthesia in 304 adults by using a prospective randomized, double-blinded, double-dummy trial. There were no differences in demographic data, or perioperative mortality and morbidity between the two study groups. The mini-mental status examination at postoperative Days 1 to 3 were similar between the two groups. The eligible and actual times for extubation, less intense monitoring, ICU discharge, and hospital discharge were not significantly different. Further analyses revealed no differences in times for extubation and resource utilization after stratification by preoperative risk scores, age, and country. The nurse/patient ratio was similar between the remifentanil/isoflurane/propofol and fentanyl/isoflu-rane/propofol groups during the initial ICU phase and less intense monitoring phase. Increasing preoperative risk scores and older age (>70 yr) were associated with longer times until extubation (eligible), ICU discharge (eligible and actual), and hospital discharge (eligible and actual). Times until extubation (eligible and actual) and less intense monitoring (eligible) were significantly shorter in Canadian patients than United States' patients. However, there was no difference in hospital length of stay in Canadian and United States' patients. We conclude that both anesthesia techniques permit early and similar times until tracheal extubation, less intense monitoring, ICU and hospital discharge, and reduced resource utilization after coronary artery bypass graft surgery.

IMPLICATIONS

An ultra-short opioid technique was compared with a standard fast-track small-dose opioid technique in coronary artery bypass graft patients in a prospective randomized, double-blinded controlled study. The postoperative recovery and resource utilization, including stratification of preoperative risk score, age, and country, were analyzed.

Respiratory mucus from asymptomatic smokers is better hydrated and more easily cleared by mucociliary action

We compared the physical and transport properties of tracheal mucus collected from 16 asymptomatic smokers and from 18 nonsmokers. The smokers produced a larger volume of mucus (wet weight 18.6 versus 11.2 mg; p = 0.04) with a lower solids content (11.5 versus 16.3%; p = 0.02) and a lower modulus of rigidity (log G* 2.37 versus 2.62; p = 0.04). Although the smokers mucus had a 40% faster mucociliary transport rate on the frog palate (p = 0.04), the cough clearability was nearly identical to the mucus from nonsmokers. The differences are similar to those observed in rats or dogs chronically exposed to cigarette smoke. These data suggest both a quantitative and a qualitative difference in the composition of mucus from asymptomatic smokers. The increased volume of a watery mucus with increased mucociliary clearability may help to protect the airways from the injurious effects of inhaled smoke.

General anesthesia does not alter the viscoelastic or transport properties of human respiratory mucus

Observations that mucus transport rates (MTR) are depressed in anesthetized animals and humans have led to speculation that general anesthesia depresses ciliary activity or adversely alters the physical properties of the respiratory mucus (RM). We investigated the possibility that anesthesia changes the physical properties of RM in such a way as to depress ciliary transport. We collected 33 samples of RM from the endotracheal tubes (ETTs) of 25 people aged 1 to 79 years undergoing elective surgery who had no clinical evidence of lung disease. We measured the rigidity, viscoelasticity, spinnability, and the percentage of solid composition of these specimens as well as the transport of the collected RM across the mucus-depleted frog palate. These physical properties were not significantly different from RM collected from awake volunteers using the bronchoscopy brush collection technique. Differences in spinnability, transportability, and solid content of paired mucus samples from the inside and outside of the ETTs are suggestive of altered RM hydration, but this requires further study. The decrease in MTR during general anesthesia is probably due to mechanisms other than alterations in the physical properties of mucus.

Collection and analysis of respiratory mucus from subjects without lung disease

We collected the respiratory mucus coating the endotracheal tubes used during short surgical procedures in 27 patients with no clinical evidence of respiratory disease. Twelve were male and 15 were female, and they ranged from 1 to 64 yr of age (mean, 28.7 yr). The viscoelastic properties, frog palate transport rate, and percent solid composition were in the normal range reported for both canine and human mucus collected using the bronchoscopy brush technique. There were no significant differences noted between male and female patients, and there were no changes in mucus or transport properties seen with aging. Mucus was also collected separately from the inside of the tube exposed to constant gas flow (13 patients), and from the outside of the endotracheal tubes in 25 patients. Although there were no significant differences in viscoelastic properties between inside and outside mucus, there was a greater thread formation (filance, 45 versus 26 mm; p less than 0.005) and a higher percentage of solids in mucus from the inside of the endotracheal tube (15.9 versus 11.4%; p less than 0.05), which is compatible with reduced hydration. The duration of anesthesia ranged from 25 to 195 min (mean, 85 min). There was no effect of duration of anesthesia on any of the measured mucus properties. This technique for mucus collection allows us to study alterations in mucus properties in patients with and without pulmonary disease at the time of incidental surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Crecimiento y mortalidad en juveniles de siete especies arbóreas en un bosque muy húmedo tropical intervenido de Costa Rica

Se estudiaron por un período de cuatro años los patrones de crecimiento en diámetro y altura, así como la mortalidad de brinzales (individuos e 0.30 m altura y < 1.5m altura) y latizales (individuos e1.5 m altura y £ 9.9 cm DAP) en un bosque sometido a dos tipos de intervención. El estudio se basa en mediciones anuales de individuos de las dos categorías de tamaño, marcados un año después de la aplicación del aprovechamiento. Siete especies arbóreas fueron estudiadas: Cecropia (dos especies) Cecropia insignis y Cecropia obtusifolia, Laetia procera, Rollinia pittieri, Apeiba membranacea, Virola koschnyi. y Virola sebifera. A nivel de brinzal las especie que presentaron el mayor crecimiento en diámetro y en altura fueron las especies del género Cecropia, mientras que en la categoría de latizal, fue L. Procera. El crecimiento en diámetro y en altura se correlacionó significativamente con el índice de iluminación de copa, únicamente en el caso de las dos especies de Cecropia y V. sebifera. Las tasas de mortalidad más altas se encontraron en los brinzales.