The importance of niche vs. neutral assembly mechanisms in structuring tropical tree communities remains an important unsettled question in community ecology Bell G (2005) Ecology 86:1757-1770. There ...is ample evidence that species distributions are determined by soils and habitat factors at landscape (<10⁴ km²) and regional scales. At local scales (<1 km²), however, habitat factors and species distributions show comparable spatial aggregation, making it difficult to disentangle the importance of niche and dispersal processes. In this article, we test soil resource-based niche assembly at a local scale, using species and soil nutrient distributions obtained at high spatial resolution in three diverse neotropical forest plots in Colombia (La Planada), Ecuador (Yasuni), and Panama (Barro Colorado Island). Using spatial distribution maps of >0.5 million individual trees of 1,400 species and 10 essential plant nutrients, we used Monte Carlo simulations of species distributions to test plant-soil associations against null expectations based on dispersal assembly. We found that the spatial distributions of 36-51% of tree species at these sites show strong associations to soil nutrient distributions. Neutral dispersal assembly cannot account for these plant-soil associations or the observed niche breadths of these species. These results indicate that belowground resource availability plays an important role in the assembly of tropical tree communities at local scales and provide the basis for future investigations on the mechanisms of resource competition among tropical tree species.
Background.
The main reason for dose reduction of afatinib is gastrointestinal toxicity (GT). In a phase II study, we analyzed anthropometrical, nutritional, and biochemical factors associated with ...GT induced by afatinib.
Materials and Methods.
Patients diagnosed with non‐small cell lung cancer who progressed to prior chemotherapy received 40 mg of afatinib. Malnutrition was determined by Subjective Global Assessment, and lean body mass (LBM) was determined by computed tomography scan analysis using a pre‐established Hounsfield unit threshold. Toxicity was obtained during four cycles by Common Terminology Criteria for Adverse Events.
Results.
Eighty‐four patients were enrolled. Afatinib was administered as the second, third, and fourth line of treatment in 54.8%, 38.1%, and 7.12% of patients, respectively. Severe diarrhea, mucositis, and overall severe GT were present in 38.9%, 28.8%, and 57.5%, respectively. Of the patients, 50% developed dose‐limiting toxicity (DLT). Patients with malnutrition have higher risk for severe GT. Patients with lower LBM and body mass index developed more DLT (71.4% vs. 18.8%).
Conclusion.
Malnutrition is associated with a higher risk of severe GT induced by afatinib. Determination of nutritional status and body composition are helpful in identifying patients at higher risk of severe GT and could allow initiating treatment with lower doses according to tolerance.
Implications for Practice:
Body composition analysis, specifically lean body mass quantification, and nutritional status assessment are significant clinical variables to take into account when assessing oncological patients. This study on patients with non‐small cell lung cancer treated with afatinib showed the important impact that malnutrition and low lean body mass have on the risk for developing dose‐limiting toxicity and severe gastrointestinal toxicity. Still more research needs to be done to explore dose adjustment according to lean body mass, especially in drugs that are given at fixed doses, such as afatinib. However, this study presents evidence for the clinical oncologist to have a closer follow‐up with malnourished patients and even to consider a lower starting dose until therapeutic dose is achieved.
This phase II study analyzed anthropometrical, nutritional, and biochemical factors associated with gastrointestinal toxicity (GT) induced by afatinib. Malnutrition is associated with a higher risk of severe GT induced by afatinib. Therefore determination of nutritional status and body composition could identify patients at higher risk of severe GT and allow treatment with lower doses according to tolerance.
Among the local processes that determine species diversity in ecological communities, fluctuation‐dependent mechanisms that are mediated by temporal variability in the abundances of species ...populations have received significant attention. Higher temporal variability in the abundances of species populations can increase the strength of temporal niche partitioning but can also increase the risk of species extinctions, such that the net effect on species coexistence is not clear. We quantified this temporal population variability for tree species in 21 large forest plots and found much greater variability for higher latitude plots with fewer tree species. A fitted mechanistic model showed that among the forest plots, the net effect of temporal population variability on tree species coexistence was usually negative, but sometimes positive or negligible. Therefore, our results suggest that temporal variability in the abundances of species populations has no clear negative or positive contribution to the latitudinal gradient in tree species richness.
We quantified temporal population variability for tree species in 21 large forest plots and found much greater variability for higher latitude plots with fewer tree species. In addition, we used a fitted mechanistic model to show that among the forest plots, the net effect of temporal population variability on tree species coexistence was usually negative, but sometimes positive or negligible. Therefore, our results suggest that temporal population variability has no clear negative or positive contribution to the latitudinal gradient in tree species richness.
Este artículo de investigación implicando el lente teórico luhmanniano (teoría de sistemas de tercera generación, teoría de autoproducción, con su concepto clave de autopoiesis), en el marco del ...objetivo general que dice: “complejizar el proceso de decisiones que deciden en los empresarios la creación y la perdurabilidad de las empresas”, a partir de historias de empresarios, registradas a través de entrevistas semiestructuradas y tratadas con la herramienta de análisis cualitativo software NVivo, distinguió como metapautas los lenguajes: “construcción de futuro”, “desafiantes-tenacidad-persistencia-insistencia” e “irritación permanente como constitutiva de estado de confort”. El artículo contribuye a la construcción de dominio de la teoría, para tratarla con respeto, pero también con irreverencia, en el sentido de ejercer un pensamiento crítico, extrañándola después de otear sus profundas y elevadas abstracciones, para que en algún momento sea alcanzada una independencia teórica, con posibilidades de enfrentar la importación acrítica de teorías allende las fronteras de Colombia.
Symbiotic nitrogen (N)‐fixing trees can provide large quantities of new N to ecosystems, but only if they are sufficiently abundant. The overall abundance and latitudinal abundance distributions of ...N‐fixing trees are well characterised in the Americas, but less well outside the Americas.
Here, we characterised the abundance of N‐fixing trees in a network of forest plots spanning five continents, ~5,000 tree species and ~4 million trees. The majority of the plots (86%) were in America or Asia. In addition, we examined whether the observed pattern of abundance of N‐fixing trees was correlated with mean annual temperature and precipitation.
Outside the tropics, N‐fixing trees were consistently rare in the forest plots we examined. Within the tropics, N‐fixing trees were abundant in American but not Asian forest plots (~7% versus ~1% of basal area and stems). This disparity was not explained by mean annual temperature or precipitation. Our finding of low N‐fixing tree abundance in the Asian tropics casts some doubt on recent high estimates of N fixation rates in this region, which do not account for disparities in N‐fixing tree abundance between the Asian and American tropics.
Synthesis. Inputs of nitrogen to forests depend on symbiotic nitrogen fixation, which is constrained by the abundance of N‐fixing trees. By analysing a large dataset of ~4 million trees, we found that N‐fixing trees were consistently rare in the Asian tropics as well as across higher latitudes in Asia, America and Europe. The rarity of N‐fixing trees in the Asian tropics compared with the American tropics might stem from lower intrinsic N limitation in Asian tropical forests, although direct support for any mechanism is lacking. The paucity of N‐fixing trees throughout Asian forests suggests that N inputs to the Asian tropics might be lower than previously thought.
Inputs of nitrogen to forests depend on symbiotic nitrogen fixation, which is constrained by the abundance of N‐fixing trees. By analysing a large dataset of ~4 million trees, we found that N‐fixing trees were consistently rare in the Asian tropics as well as across higher latitudes in Asia, America and Europe. The rarity of N‐fixing trees in the Asian tropics compared with the American tropics might stem from lower intrinsic N limitation in Asian tropical forests, although direct support for any mechanism is lacking. The paucity of N‐fixing trees throughout Asian forests suggests that N inputs to the Asian tropics might be lower than previously thought.
Los bosques secos tropicales (BST) son uno de los ecosistemas más amenazados de Colombia, con remanentes de estos concentrados en bosques riparios. Este trabajo estudió la vegetación de un bosque ...ripario ubicado dentro de un remanente de BST en la cuenca alta del río Magdalena mediante el uso de transectos en tres estaciones a lo largo del arroyo La Avería (Paicol, Huila, Colombia). Se encontraron 199 individuos distribuidos en 47 especies. La composición florística fue semejante a la de otros BST, mientras que el número de individuos fue menor. Fabaceae fue la familia más representada y Zygia longifolia y Guadua angustifolia las especies con mayor Índice de Valor de Importancia (IVI). Se concluyó que el bosque ha sido sometido a perturbaciones antrópicas y se encuentra en una etapa sucesional temprana. Además, se encontraron diferencias en el grado de conservación del bosque entre las tres estaciones muestreadas.
Palm Management in South America Bernal, Rodrigo; Torres, Claudia; García, Néstor ...
The Botanical review,
12/2011, Volume:
77, Issue:
4
Journal Article
Peer reviewed
We reviewed information on management of useful palms in South America. We documented management for 96 species, from incidental activities intended to increase populations of wild palms to the ...inclusion of palms in complex agroforestry systems. Two species, Bactris gasipaes and Parajubaea cocoides, are domesticated. Managed species are remarkably fewer than species used in the region, which suggests that harvesters often disregard the fate of the species they use. The best way of managing palms is to employ harvest methods that do not decimate the populations. Although a variety of harvesting techniques have been documented, overharvest is common, and mismanagement prevails - unnecessary felling of palms in order to harvest leaves or fruits is a widespread practice. Research should focus on assessing production in response to management practices, but eradicating the habit of destructive harvest is an obvious priority. Research on palm management must be combined with actions addressed to all stakeholders of the palm/humans system.
•We studied the effect of palm heart extraction from the palm Euterpe oleracea.•We constructed population matrix models and simulated different harvest scenarios.•Current harvest regimes result in ...dramatic demographic changes.•Current harvesting reducing by more than 90% supply of palm, beyond recovery.•Sustainable scenarios involve annual harvests between 50% and 75% of all stems.
Palm heart is an important non-timber forest product obtained from various palm species in tropical forests. We studied the effect of four decades of palm heart extraction from the clonal palm Euterpe oleracea at the southern Pacific coast of Colombia. We monitored populations that had been subject to a range of harvest intensities and used measured vital rates (survival, growth, sexual and clonal reproduction) to construct population matrix models. We then used these models to simulate several harvest scenarios and to project the population dynamics for the next 50years. Our projections suggest that the currently implemented intensive harvest regimes – which involve up to four harvests per year – result in dramatic demographic changes, primarily affecting seedlings and adults. In addition, current harvest regimes affect the future supply of palm heart, which is projected to drop sharply during the first years following harvest and fails to recover unless a number of stems are spared. Our simulations indicate that the most sustainable scenarios involve annual harvest between 50% and 75% of all harvestable stems, without any removal of small shoots from the clumps. Implementation of this regime must be accompanied by other management practices, including planning harvestable areas, marking the stems to be cut during subsequent harvests, assigning harvesters to specific areas, and leaving harvest residues as mulch around clumps. The degradation of populations of E. oleracea directly affects livelihoods of local people, by reducing cash income from palm heart sales and by reducing availability of palm fruits, a locally important food resource.
In Amazonian tropical forests, recent studies have reported increases in aboveground biomass and in primary productivity, as well as shifts in plant species composition favouring fast-growing species ...over slow-growing ones. This pervasive alteration of mature tropical forests was attributed to global environmental change, such as an increase in atmospheric CO2 concentration, nutrient deposition, temperature, drought frequency, and/or irradiance. We used standardized, repeated measurements of over 2 million trees in ten large (16-52 ha each) forest plots on three continents to evaluate the generality of these findings across tropical forests. Aboveground biomass increased at seven of our ten plots, significantly so at four plots, and showed a large decrease at a single plot. Carbon accumulation pooled across sites was significant (+0.24 MgC ha(-1) y(-1), 95% confidence intervals 0.07, 0.39 MgC ha(-1) y(-1)), but lower than reported previously for Amazonia. At three sites for which we had data for multiple census intervals, we found no concerted increase in biomass gain, in conflict with the increased productivity hypothesis. Over all ten plots, the fastest-growing quartile of species gained biomass (+0.33 0.09, 0.55 % y(-1)) compared with the tree community as a whole (+0.15 % y(-1)); however, this significant trend was due to a single plot. Biomass of slow-growing species increased significantly when calculated over all plots (+0.21 0.02, 0.37 % y(-1)), and in half of our plots when calculated individually. Our results do not support the hypothesis that fast-growing species are consistently increasing in dominance in tropical tree communities. Instead, they suggest that our plots may be simultaneously recovering from past disturbances and affected by changes in resource availability. More long-term studies are necessary to clarify the contribution of global change to the functioning of tropical forests.
Abstract
We describe and discuss palm heart production from wild Euterpe oleracea in Colombia and analyse the social, ecological and trade aspects determining its sustainability. Palm heart is ...harvested on communal lands by Afro-descendants, who receive US$0.1 per stem. To obtain an income corresponding to a minimum wage, a harvester would have to fell 167 stems per day, i.e. one palm stem every 3 min non-stop over 8 h of work. The pressure of this system leads to over-exploitation of the palm stands, causing local exhaustion of the resource, thus depriving communities of the palm fruit, a vital component of their diet. We evaluated in two harvest scenarios on non-harvested palm populations (annual harvest of either 75 or 50% of the stems), the availability of palm hearts, the number of harvesters per hectare and their net income. We also considered the possibility of doubling or tripling the income of primary producers without affecting the palm stands or increasing the harvesters’ effort. The low market retail price of the final product precludes an improvement in the pay of harvesters or their work conditions. Today many consumers would pay a higher price if it were clear that the product they buy is being produced in a way that is environmentally friendly and socially fair. This information should be provided on the product label and it should be part of communication and education strategies. An alliance of supermarket chains and non-governmental organizations could positively influence attitudes toward the value of this product and help to make consumers aware of their responsibility regarding the fate of the palm and the fairness of its harvest.
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