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Background and Objective: Non-invasive methods for postural assessment are tools used for tracking and monitoring the progression of postural deviations. Different computer-based methods have been used to assess human posture, including mobile applications based on images and sensors. However, such solutions still require manual identification of anatomical points. This study aims to present and validate the NLMeasurer, a mobile application for postural assessment. This application takes advantage of the PoseNet, a solution based on computer vision and machine learning used to estimate human pose and identify anatomical points. From the identified points, NLMeasurer calculates postural measures., Methods: Twenty participants were photographed in front view while using surface markers over anatomical landmarks. Then, the surface markers were removed, and new photos were taken. The photos were analyzed by two examiners, and six postural measurements were computed with NLMeasurer and a validated biophotogrammetry software. One-sample t-test and Bland Altman procedure were used to assess agreement between the methods, and Intraclass Correlation Coefficient (ICC) was used to assess inter- and intra-rater reliability., Results: Postural measurements calculated using the NLMeasurer were in agreement with the biophotogrammetry software. Furthermore, there was good inter- and intra-rater reliability for most photos without surface markers., Conclusions: NLMeasurer demonstrated to be a valid tool method to assess postural measurements in the frontal view. The use of surface markers on specific anatomical landmarks (i.e., ears, iliac spines and ankles) can facilitate the digital identification of these landmarks and improve the reliability of the postural measurements performed with NLMeasurer., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Introduction: The Pilates method is an approach to body and mind exercises that has as its foundation the gain of stability, strength and flexibility, and the work of muscular control, posture and breathing, which can generate repercussions on oxidative stress and ROS production, it is expected that Pilates can satisfactorily influence glycemic and oxidative stress reduction in elderly diabetes., Aim: To analyze the effect of a Pilates protocol on variables indicative of metabolic control and oxidative stress in patients with Type 2 Diabetes Mellitus., Method: Randomized clinical trial in type 2 diabetics enrolled in Hiperdia Parnaíba. A Pilates protocol was performed for 8 weeks, with 2 weekly consultations. The tested variables were: blood glucose, glycated hemoglobin, lipid profile, C-reactive protein and malondialdehyde. ANOVA tests, correlation of Wilcoxon, Friedman and Spearman, were used, with a significance level of 5%., Results: 44 diabetics participated in the study (intervention group: 22; control: 22), with a mean age of 61.23 ± 8.49years, the majority being female (77.3%), married (59.1%), literate (31.8%), with an average BMI of 26.96 ± 4.35 kg/m 2 . When analyzing the effects of the protocol, there was a significant reduction in glycated hemoglobin (p = 0.002) and oxidative stress (p = 0.004) in the intervention group, however, there were no differences in fasting glucose (p = 0.055) and in the profile lipid, expressed by the total cholesterol (p = 0.654), HDL (p = 0.591), LDL (p = 0.564) and triglycerides (0.192). There was a moderate positive correlation between oxidative stress and glycated hemoglobin (r = 0.44, p = 0.000)., Conclusion: The exercise protocol based on the Pilates method produced a reduction in glycated hemoglobin and oxidative stress., Competing Interests: Declaration of competing interest The authors declare that there are no conflicts of interest, according to the attached document., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Plant traits are increasingly being used to improve prediction of plant function, including plant demography. However, the capability of plant traits to predict demographic rates remains uncertain, particularly in the context of trees experiencing a changing climate. Here we present data combining 17 plant traits associated with plant structure, metabolism and hydraulic status, with measurements of long-term mean, maximum and relative growth rates for 176 trees from the world's longest running tropical forest drought experiment. We demonstrate that plant traits can predict mean annual tree growth rates with moderate explanatory power. However, only combinations of traits associated more directly with plant functional processes, rather than more commonly employed traits like wood density or leaf mass per area, yield the power to predict growth. Critically, we observe a shift from growth being controlled by traits related to carbon cycling (assimilation and respiration) in well-watered trees, to traits relating to plant hydraulic stress in drought-stressed trees. We also demonstrate that even with a very comprehensive set of plant traits and growth data on large numbers of tropical trees, considerable uncertainty remains in directly interpreting the mechanisms through which traits influence performance in tropical forests., (© 2020 The Authors New Phytologist ©2020 New Phytologist Trust.)

Human posture and Range of Motion (ROM) are important components of a physical assessment and, from the collected data, it is possible to identify postural deviations such as scoliosis or joint and muscle limitations, hence identifying risks of more serious injuries. Posture assessment and ROM measures are also necessary metrics to monitor the effect of treatments used in the motor rehabilitation of patients, as well as to monitor their clinical progress. These evaluation processes are more frequently performed through visual inspection and manual palpation, which are simple and low cost methods. These methods, however, can be optimized with the use of tools such as photogrammetry and goniometry. Mobile solutions have also been developed to help health professionals to capture more objective data and with less risk of bias. Although there are already several systems proposed for assessing human posture and ROM in the literature, they have not been able to automatically identify and mark Anatomical and Segment Points (ASPs). The hypothesis presented here considers the development of a mobile application for automatic identification of ASPs by using machine learning algorithms and computer vision models associated with technologies embedded in smartphones. From ASPs identification, it will be possible to identify changes in postural alignment and ROM. In this context, our view is that an application derived from the hypothesis will serve as an additional tool to assist in the physical assessment process and, consequently, in the diagnosis of disorders related to postural and movement changes., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The fate of tropical forests under future climate change is dependent on the capacity of their trees to adjust to drier conditions. The capacity of trees to withstand drought is likely to be determined by traits associated with their hydraulic systems. However, data on whether tropical trees can adjust hydraulic traits when experiencing drought remain rare. We measured plant hydraulic traits (e.g. hydraulic conductivity and embolism resistance) and plant hydraulic system status (e.g. leaf water potential, native embolism and safety margin) on >150 trees from 12 genera (36 species) and spanning a stem size range from 14 to 68 cm diameter at breast height at the world's only long-running tropical forest drought experiment. Hydraulic traits showed no adjustment following 15 years of experimentally imposed moisture deficit. This failure to adjust resulted in these drought-stressed trees experiencing significantly lower leaf water potentials, and higher, but variable, levels of native embolism in the branches. This result suggests that hydraulic damage caused by elevated levels of embolism is likely to be one of the key drivers of drought-induced mortality following long-term soil moisture deficit. We demonstrate that some hydraulic traits changed with tree size, however, the direction and magnitude of the change was controlled by taxonomic identity. Our results suggest that Amazonian trees, both small and large, have limited capacity to acclimate their hydraulic systems to future droughts, potentially making them more at risk of drought-induced mortality., (© 2020 John Wiley & Sons Ltd.)

The absorption of atmospheric water directly into leaves enables plants to alleviate the water stress caused by low soil moisture, hydraulic resistance in the xylem and the effect of gravity on the water column, while enabling plants to scavenge small inputs of water from leaf-wetting events. By increasing the availability of water, and supplying it from the top of the canopy (in a direction facilitated by gravity), foliar uptake (FU) may be a significant process in determining how forests interact with climate, and could alter our interpretation of current metrics for hydraulic stress and sensitivity. FU has not been reported for lowland tropical rainforests; we test whether FU occurs in six common Amazonian tree genera in lowland Amazônia, and make a first estimation of its contribution to canopy-atmosphere water exchange. We demonstrate that FU occurs in all six genera and that dew-derived water may therefore be used to "pay" for some morning transpiration in the dry season. Using meteorological and canopy wetness data, coupled with empirically derived estimates of leaf conductance to FU (k fu ), we estimate that the contribution by FU to annual transpiration at this site has a median value of 8.2% (103 mm/year) and an interquartile range of 3.4%-15.3%, with the biggest sources of uncertainty being k fu and the proportion of time the canopy is wet. Our results indicate that FU is likely to be a common strategy and may have significant implications for the Amazon carbon budget. The process of foliar water uptake may also have a profound impact on the drought tolerance of individual Amazonian trees and tree species, and on the cycling of water and carbon, regionally and globally., (© 2019 John Wiley & Sons Ltd.)

Aim: To evaluate (i) the in vitro activity of eugenol (EUG) and three derivatives against Mycobacterium tuberculosis (Mtb), nontuberculous mycobacteria (NTM) and other bacteria, (ii) the EUG and antituberculosis drugs combinatory effect and (iii) the EUG and its derivatives cytotoxicity., Materials & Methods: Minimum inhibitory concentration of the compounds were determined by resazurin microtiter or broth microdilution assay and the drug interaction between EUG and antituberculosis drugs by resazurin drug combination microtiter. The cytotoxicity was carried out in macrophages, HeLa and VERO cells. Results: EUG and derivatives displayed activity and synergic effect of EUG combined with rifampicin, isoniazid, ethambutol, and pyrazinamide in Mtb including multidrug-resistant isolates, with more selectivity to bacillus than macrophages, HeLa and VERO cells (selective index from 0.65 to 31.4). EUG derivatives (4-allyl-2-methoxyphenyl acetate, 4-allyl-2-methoxyphenyl benzoate, and 4-allyl-2-methoxyphenyl 4-nitrobenzoate) were more active against nontuberculous mycobacteria than EUG. EUG and derivatives exhibited low activity in other Gram-positive and -negative bacteria., Conclusion: EUG and its derivatives show activity against Mycobacterium spp. and synergic effect of EUG combined with antituberculosis drugs against Mtb.

Piperine, a bioactive compound from Piper nigrum and Piper longum, has shown promising activity as efflux pump (EP) inhibitor and as adjunct in treatment of tuberculosis (TB). The present systematic review investigated scientific studies of the activity of piperine against mycobacteria, with a focus on its mechanism of action, drug interactions, and antimycobacterial activity. A broad and rigorous literature search of three electronic databases (PubMed, Web of Knowledge, and LILACS) was performed according to the PRISMA statement. We considered studies that were published up to December 1, 2017. Google Scholar was also searched to increase the number of publications. We searched for articles using the search terms "piperine" and "Mycobacterium spp." The search yielded a total of 225 articles. After removing duplicate publications, 208 publications remained. Of these, we evaluated the full text of 13 articles. After applying the inclusion criteria, eight studies were included in the present systematic review. The results of the systematic review showed that piperine has promising anti-TB activity, mainly when combined with antimicrobials, and plays an important role as an EP inhibitor.

Setting: The increase of multidrug and extensively drug resistant Mycobacterium tuberculosis strains turns the search for new tuberculosis (TB) treatment options of paramount importance., Objective: In this sense, the present study evaluates the in vitro activity of isoniazid (INH)/rifampicin (RIF)/levofloxacin (LVX) and INH/RIF/linezolid (LNZ) combinations in resistant M. tuberculosis., Design: The activities of the combinations were evaluated with M. tuberculosis H 37 Rv, susceptible and 10 resistant clinical isolates by three-dimensional checkerboard. LVX and LNZ were used as the third drug at fixed ½ and ¼ minimum inhibitory concentration (MIC). INH and RIF were tested at concentrations ranging from 0.0009 μg/mL to 50 μg/mL and 0.0009 μg/mL to 800 μg/mL, respectively. The combinatorial effects were determined by the Fractional Inhibitory Concentration Index (FICI). FICI values ≤ 0.75, 0.75-4 and ≥4 were considered as synergism, indifferent and antagonism, respectively., Results: MIC ranged from 0.03 - 6.25 μg/mL for INH, 0.008-100 μg/mL for RIF, 0.12-0.25 μg/mL for LVX and 0.25-0.5 μg/mL for LNZ in the H 37 Rv and all clinical isolates. INH/RIF/LVX and INH/RIF/LNZ synergisms were observed in 40 and 50% of the resistant M. tuberculosis clinical isolates and better observed for INH and RIF combined to LVX or LNZ at ¼ MIC., Conclusion: The present study calls attention for the potential use of INH/RIF/LVX and INH/RIF/LNZ combinations in the treatment of resistant TB., (Copyright © 2018. Published by Elsevier Ltd.)

Tuberculosis (TB) is an important public health problem worldwide and the emergence of multidrug-resistant (MDR) TB and extensively drug-resistant (XDR) TB worsened the global context. The resistance in Mycobacterium tuberculosis, the causative agent of TB, can partially derive from efflux pumps (EPs) activity in plasma membrane. Due to the recent discovery of piperine (PIP), an organic alkaloid compound, increasing the bioavailability of various drugs, the current assay evaluated the combined activity of PIP and anti-TB drugs in susceptible and resistant M. tuberculosis clinical isolates. The minimum inhibitory concentrations for isoniazid, rifampicin, ethambutol, streptomycin and PIP were determined by resazurin microtiter assay and the combined effects of anti-TB drugs with PIP determined by resazurin drug combination microtiter assay and time-kill curve. The efflux pump inhibitor activity of PIP was determined by bromide accumulation assay and cytotoxicity carried out in VERO cells and J774. A1 macrophages. PIP showed to have EPI activity and RIF + PIP and SM + PIP combinations showed synergistic effect, but low effect in enhancing the killing in M. tuberculosis H 37 Rv and in the clinical isolates studied, which had different resistance profiles. Future studies are needed to further clarify the importance of PIP as an adjunctive drug in the therapy against TB., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

CO 2 efflux from stems (CO 2_stem ) accounts for a substantial fraction of tropical forest gross primary productivity, but the climate sensitivity of this flux remains poorly understood. We present a study of tropical forest CO 2_stem from 215 trees across wet and dry seasons, at the world's longest running tropical forest drought experiment site. We show a 27% increase in wet season CO 2_stem in the droughted forest relative to a control forest. This was driven by increasing CO 2_stem in trees 10-40 cm diameter. Furthermore, we show that drought increases the proportion of maintenance to growth respiration in trees > 20 cm diameter, including large increases in maintenance respiration in the largest droughted trees, > 40 cm diameter. However, we found no clear taxonomic influence on CO 2_stem and were unable to accurately predict how drought sensitivity altered ecosystem scale CO 2_stem , due to substantial uncertainty introduced by contrasting methods previously employed to scale CO 2_stem fluxes. Our findings indicate that under future scenarios of elevated drought, increases in CO 2_stem may augment carbon losses, weakening or potentially reversing the tropical forest carbon sink. However, due to substantial uncertainties in scaling CO 2_stem fluxes, stand-scale future estimates of changes in stem CO 2 emissions remain highly uncertain., (© 2018 The Authors New Phytologist © 2018 New Phytologist Trust.)

Aim: Evaluating carvacrol, derivatives and carvacrol plus anti-TB (anti-tuberculous) drug combination activities in Mycobacterium tuberculosis as well as carvacrol cytotoxicity, efflux pump inhibitor activity and morphological changes in M. tuberculosis H 37 Rv., Methods: Carvacrol (CAR) and derivatives' activities were determined by resazurin microtiter assay and drug interaction by resazurin drug combination microtiter. Carvacrol cytotoxicity in VERO cells and efflux pumps inhibitor activity by ethidium bromide assay were determined and scanning electron microscopy performed., Results: Carvacrol MIC ranged from 19 to 156 μg/ml and carvacrol plus rifampicin combination showed synergistic effect in clinical isolates. No anti-M. tuberculosis activity improvement was observed with carvacrol derivatives. Carvacrol showed to be selective for M. tuberculosis, to have efflux pumps activity and to induce rough bacillary and agglomerates., Conclusion: Carvacrol shows good anti-M. tuberculosis activity and synergism with rifampicin.

Transpiration from the Amazon rainforest generates an essential water source at a global and local scale. However, changes in rainforest function with climate change can disrupt this process, causing significant reductions in precipitation across Amazonia, and potentially at a global scale. We report the only study of forest transpiration following a long-term (>10 year) experimental drought treatment in Amazonian forest. After 15 years of receiving half the normal rainfall, drought-related tree mortality caused total forest transpiration to decrease by 30%. However, the surviving droughted trees maintained or increased transpiration because of reduced competition for water and increased light availability, which is consistent with increased growth rates. Consequently, the amount of water supplied as rainfall reaching the soil and directly recycled as transpiration increased to 100%. This value was 25% greater than for adjacent nondroughted forest. If these drought conditions were accompanied by a modest increase in temperature (e.g., 1.5°C), water demand would exceed supply, making the forest more prone to increased tree mortality., (© 2017 John Wiley & Sons Ltd.)

Purpose: Vulvovaginal candidiasis (VVC) is one of the most frequent female genital disorders and Candida glabrata is the second most common agent. Current study was aimed to study the susceptibility to antifungal agents of C. glabrata isolated from vaginal samples and some virulence attributes in order to better understand why this species is emerging as the main VVC agents., Methods: A total of 60 C. glabrata vaginal isolates were included in this study. Firstly they were screened by susceptibility tests to antifungal agents. The isolates that showed sensitivity or resistance to fluconazole were evaluated for their virulence potential, including ability to adhere to polystyrene and vaginal ring, cell surface hydrophobicity (CSH) and capacity to form biofilm., Results: Candida glabrata isolates varied significantly in adherence capacity, biofilm formation and CSH. However, it was possible to observe that isolates resistant to fluconazole adhered more efficiently to the vaginal ring and were statistically more able to form biofilm., Conclusion: These results allow hypothesizing that C. glabrata is an emergent agent in VVC probably because the treatment with fluconazole selects this species. But once adhered, yeasts remain on biotic or abiotic surfaces causing colonization or VVC symptomatology.

Dry periods are predicted to become more frequent and severe in the future in some parts of the tropics, including Amazonia, potentially causing reduced productivity, higher tree mortality and increased emissions of stored carbon. Using a long-term (12 year) through-fall exclusion (TFE) experiment in the tropics, we test the hypothesis that trees produce leaves adapted to cope with higher levels of water stress, by examining the following leaf characteristics: area, thickness, leaf mass per area, vein density, stomatal density, the thickness of palisade mesophyll, spongy mesophyll and both of the epidermal layers, internal cavity volume and the average cell sizes of the palisade and spongy mesophyll. We also test whether differences in leaf anatomy are consistent with observed differential drought-induced mortality responses among taxa, and look for relationships between leaf anatomy, and leaf water relations and gas exchange parameters. Our data show that trees do not produce leaves that are more xeromorphic in response to 12 years of soil moisture deficit. However, the drought treatment did result in increases in the thickness of the adaxial epidermis (TFE: 20.5 ± 1.5 µm, control: 16.7 ± 1.0 µm) and the internal cavity volume (TFE: 2.43 ± 0.50 mm 3 cm -2 , control: 1.77 ± 0.30 mm 3 cm -2 ). No consistent differences were detected between drought-resistant and drought-sensitive taxa, although interactions occurred between drought-sensitivity status and drought treatment for the palisade mesophyll thickness (P = 0.034) and the cavity volume of the leaves (P = 0.025). The limited response to water deficit probably reflects a tight co-ordination between leaf morphology, water relations and photosynthetic properties. This suggests that there is little plasticity in these aspects of plant anatomy in these taxa, and that phenotypic plasticity in leaf traits may not facilitate the acclimation of Amazonian trees to the predicted future reductions in dry season water availability., (© The Author 2016. Published by Oxford University Press.)

The tropics are predicted to become warmer and drier, and understanding the sensitivity of tree species to drought is important for characterizing the risk to forests of climate change. This study makes use of a long-term drought experiment in the Amazon rainforest to evaluate the role of leaf-level water relations, leaf anatomy and their plasticity in response to drought in six tree genera. The variables (osmotic potential at full turgor, turgor loss point, capacitance, elastic modulus, relative water content and saturated water content) were compared between seasons and between plots (control and through-fall exclusion) enabling a comparison between short- and long-term plasticity in traits. Leaf anatomical traits were correlated with water relation parameters to determine whether water relations differed among tissues. The key findings were: osmotic adjustment occurred in response to the long-term drought treatment; species resistant to drought stress showed less osmotic adjustment than drought-sensitive species; and water relation traits were correlated with tissue properties, especially the thickness of the abaxial epidermis and the spongy mesophyll. These findings demonstrate that cell-level water relation traits can acclimate to long-term water stress, and highlight the limitations of extrapolating the results of short-term studies to temporal scales associated with climate change., (© 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.)

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.

Determining climate change feedbacks from tropical rainforests requires an understanding of how carbon gain through photosynthesis and loss through respiration will be altered. One of the key changes that tropical rainforests may experience under future climate change scenarios is reduced soil moisture availability. In this study we examine if and how both leaf photosynthesis and leaf dark respiration acclimate following more than 12 years of experimental soil moisture deficit, via a through-fall exclusion experiment (TFE) in an eastern Amazonian rainforest. We find that experimentally drought-stressed trees and taxa maintain the same maximum leaf photosynthetic capacity as trees in corresponding control forest, independent of their susceptibility to drought-induced mortality. We hypothesize that photosynthetic capacity is maintained across all treatments and taxa to take advantage of short-lived periods of high moisture availability, when stomatal conductance (gs ) and photosynthesis can increase rapidly, potentially compensating for reduced assimilate supply at other times. Average leaf dark respiration (Rd ) was elevated in the TFE-treated forest trees relative to the control by 28.2 ± 2.8% (mean ± one standard error). This mean Rd value was dominated by a 48.5 ± 3.6% increase in the Rd of drought-sensitive taxa, and likely reflects the need for additional metabolic support required for stress-related repair, and hydraulic or osmotic maintenance processes. Following soil moisture deficit that is maintained for several years, our data suggest that changes in respiration drive greater shifts in the canopy carbon balance, than changes in photosynthetic capacity., (© 2015 John Wiley & Sons Ltd.)

[Purpose] Stretching using proprioceptive neuromuscular facilitation involve physiological reflex mechanisms through submaximal contraction of agonists which activate Golgi organ, promoting the relaxation reflex. The aim of this study was to evaluate the effects of proprioceptive neuromuscular facilitation alone and with prior application of cryotherapy and thermotherapy on hamstring stretching. [Subjects and Methods] The sample comprised of 32 young subjects with hamstring retraction of the right limb. The subjects were randomly allocated to four groups: the control, flexibility PNF, flexibility PNF associated with cryotherapy, flexibility PNF in association with ultrasound therapy. [Results] After 12 stretching sessions, experimental groups showed significant improvements compared to the control group. Moreover, we did not find any significant differences among the experimental groups indicating PNF stretching alone elicits similar results to PNF stretching with prior administration of cryotherapy or thermotherapy. [Conclusion] PNF without other therapy may be a more practical and less expensive choice for clinical care.

*Fine root dynamics is widely recognized as an important biogeochemical process, but there are few data on fine root growth and its response to soil resource availability, especially for tropical forests. *We evaluated the response of fine root dynamics to altered availability of soil water and nutrients in a 20-yr-old forest regrowth in eastern Amazonia. In one experiment the dry season reduction in soil moisture was alleviated by irrigation. In the other experiment, nutrient supply was reduced by litter removal. We used the ingrowth core technique to measure fine root mass growth, length growth, mortality and specific root length. *Dry-season irrigation had no significant effect on mass and length of live and dead roots, whereas litter removal reduced mass and length of live roots. For both irrigation and litter removal experiments, root growth was significantly greater in the dry season than in the wet season. *Increased root growth was associated with decreased soil water availability. However, root growth did not increase in response to nutrient reduction in litter removal plots. Overall, our results suggest that belowground allocation may differ according to the type of soil resource limitation.

Despite research demonstrating that water and nutrient availability exert strong effects on multiple ecosystem processes in tropical forests, little is known about the effect of these factors on the demography and population dynamics of tropical trees. Over the course of 5 years, we monitored two common Amazonian secondary forest species-Lacistema pubescens and Myrcia sylvatica-in dry-season irrigation, litter-removal and control plots. We then evaluated the effects of altered water and nutrient availability on population demography and dynamics using matrix models and life table response experiments. Our results show that despite prolonged experimental manipulation of water and nutrient availability, there were nearly no consistent and unidirectional treatment effects on the demography of either species. The patterns and significance of observed treatment effects were largely dependent on cross-year variability not related to rainfall patterns, and disappeared once we pooled data across years. Furthermore, most of these transient treatment effects had little effect on population growth rates. Our results suggest that despite major experimental manipulations of water and nutrient availability-factors considered critical to the ecology of tropical pioneer tree species-autogenic light limitation appears to be the primary regulator of tree demography at early/mid successional stages. Indeed, the effects of light availability may completely override those of other factors thought to influence the successional development of Amazonian secondary forests.

Analyses of the effects of drought stress on Amazonian regrowth stands are lacking. We measured leaf gas exchange and leaf water potential of Miconia ciliata (Melastomataceae) in a dry-season irrigation experiment in 14-yr-old regrowth. In the dry season, irrigated plants maintained significantly higher leaf water potentials, photosynthetic capacity at light saturation (A(max)), stomatal conductance (g(s)), internal CO(2) concentration (C(i)), and lower A(max)/g(s) than control plants. The degree of dry-season down-regulation of control plant A(max), along with its fast recovery following rain, reveals the importance of occasional dry-season rains to the carbon budget of M. ciliata. During the wet season, we observed higher A(max) for control plants than for plants that had been irrigated during the dry season. We hypothesize that reduced drought constraints on photosynthesis of irrigated plants advanced the flowering and fruiting phenology of irrigated plants into the dry season. Flowers and fruits of control plants developed later, during the wet season, potentially stimulating a compensatory reproductive photosynthesis response in nearby leaves. The relative drought intolerance of M. ciliata may be a deciding factor in its ability to survive through the dynamic successional development of the regrowth stand studied.