Humid Tropics Research Articles

First report of phyllode rust on Acacia crassicarpa outside its native range

AbstractAcacia crassicarpa is a tropical tree species native to Australia, West Papua and Papua New Guinea, which has been widely used to establish plantations in the lowland humid tropics of Sumatra and Kalimantan. These trees, able to grow on sites having relatively poor nutrition, have been relatively free of serious disease problems. A rust disease infecting the phyllodes of A. crassicarpa has recently been encountered in plantations in various areas of Indonesia and Malaysia where they are not native. In this study, the rust was collected and identified as Endoraecium violae‐faustiae using DNA sequence analysis based on the internal transcribed spacer (ITS) region of the rDNA. This is the first record of the rust outside its native range. Damage at present appears to be relatively mild but the pathogen could become important in the future.

Effects Of Lime And Poultry Manure On Soil Properties And Cucumber (Cucumis Sativum L) Performance In The Humid Tropics Of Southern Nigeria

Purpose: To investigate the effect of lime and organic fertilizer on soil properties and the performance of cucumber in Calabar.
 Method: Factorial combination of three levels of lime (0, 4 and 8 t/ha) and three levels of poultry manure (0, 3 and 6 t/ha), laid out in randomized complete block design (RCBD) with three replications. Data were collected on crop growth and yield indices, and soil properties (physical, chemical and biological) each year, then combined and analyzed. Fisher’s least significant difference (FLSD) at 5 % probability was used to compare the means.
 Results: There was increase in soil pH, total nitrogen, organic carbon, phosphorus, potassium, calcium and magnesium as well as the population of beneficial soil microorganisms. Lime, poultry manure (PM) and their interactions significantly (p <.0. 05) influenced the vegetative growth and fruit yield of cucumber. Cucumber treated with 8 t/ha lime had the highest vegetative growth and fruit yield (22.64 t/ha) values. Cucumber treated with 6 t/ha PM had superior growth and fruit yield (17.89 t/ha) than the control (14.27 t/ha). The interaction of 8 t/ha lime and 6 t/ha PM produced the highest values of vegetative growth and fruit yield of 25.66 t/ha and is therefore recommended for effective soil enhancement and optimum cucumber production in Calabar.
 

Thermal Stress Associated Serum Factors and the Influence of Weather Parameters in Crossbred Dairy Cows Under Humid Tropics

Assessment of the level of thermal stress (TS) in animals exposed to adverse weather helps to formulate and implement alleviation measures. Present study was to identify the presence and seasonal pattern of serum factors to be used as biological indicators for early detection of TS in animals. The year-round study involved eight cows each at a time, belonging 28 to 91 days postpartum, and replaced two cows every month. Analyzed the levels of Heat shock protein 70 (HSP 70) and cortisol in serum samples collected at weekly intervals and assessed the seasonal pattern and correlation with weather parameters. While minimum temperature (MnT) of the region varied significantly (P<0.01) between seasons (lowest mean 22.09±1.19 ºC), maximum temperature (MxT) was consistently high across seasons (yearly mean 33.64±0.77 ºC). Moderate to high (66 to 85 %) relative humidity (RH) was prevalent year-round, mainly contributed by the extended rainy season. Temperature-humidity index (THI) of the locality exceeded 78, exposing the animals to moderate to severe TS throughout the year. HSP 70 levels varied significantly (P<0.01) between seasons, with a significant hike (6.24±0.51 ng/mL) during summer (THI 83.20±0.53) and lesser elevation during other seasons of moderate THI, indicating its association with TS. Cortisol levels varied significantly (P<0.01) between seasons, however there was no significant correlation with THI and other weather parameters. To conclude, while cortisol forms a general indicator of physiological stress, HSP 70 appears more specific to TS, and its usefulness for early detection of TS needs further studies.

RESPUESTA DE TRES ESPECIES MADERABLES DE RÁPIDO CRECIMIENTO A DIFERENTES BIOCLIMAS EN ECUADOR

<p><strong>Background:</strong> The timber sector in Ecuador holds promising potential for growth and development. The intensive utilization of native taxa has depleted their genetic species pool, making them increasingly scarce in meeting the rising demand for wood. Consequently, there has been a growing exploration of new fast-growing forest species to serve as alternatives for lumber and biomass production. <strong>Objective: </strong>To assess the suitability of Andean bioclimatic conditions for the introduction of three tree species: <em>Paulownia elongata, P. fortunei</em>, and the hybrid <em>P. elongata x P. fortunei</em>. This work primarily focused in investigating whether plant density impacts the initial growth of individual tree growth and whether there is a co-dependence between site conditions and plant density in each of the three species. <strong>Methodology:</strong> The National Autonomous Institute of Farming Research (INIAP) imported 3000 seedlings, each about 10cm tall, of <em>Paulownia e</em>longata, <em>Paulownia fortunei</em>, and the hybrid <em>Paulownia elongata</em> x <em>Paulownia fortunei</em> from the World Paulownia Institute of Georgia - USA. Four experimental sites were selected in two regions of Ecuador: humid tropics (Quevedo and Santo Domingo de los Tsachilas), dry sub-peak (el Almendral) and Andes (Riobamba), each site is located at different altitudes. At each site, the experiment was set up in a spatial split-plot arrangement with randomized complete blocks. Three blocks were established, two planting frames (3x3 m and 4x4 m) and the three selected <em>Paulownia</em> species. The three blocks were laid off randomly in each experiment. The two planting frames were randomly placed within each block, and the three species were randomly planted within each planting frame. The experimental subjects (plant species) consisted of nine individuals. <strong>Results:</strong> Plants with higher height and diameter are located in areas with lower elevation, with hybrid Paulownia displaying better performance in high densities. All species showed a survival rate above 85% one-year post-establishment. However, the lowest survival is found in areas above 2000 m. <strong>Implications:</strong> High elevations restrict the individual growth of Paulownia in Andean conditions, but low altitudes enhance it. <strong>Conclusion:</strong> The three specimens performed reasonably well during one-year post-establishment. However, it is necessary to continue observing their growth until they reach their asymptotic point, determining their volumetric yield.</p>

Using RS and GIS Techniques to Assess and Monitor Coastal Changes of Coastal Islands in the Marine Environment of a Humid Tropical Region

Vypin, Vallarpadam, and Bolgatty are significant tropical coastal islands situated in the humid tropical Kerala region of India, notable for their environmental sensitivity. This study conducted a comprehensive assessment of shoreline alterations on these islands by integrating Remote Sensing (RS) and Geographic Information Systems (GIS) techniques. Utilizing satellite imagery from the LANDSAT series with a spatial resolution of 30 m, the analysis spanned the years from 1973 to 2019. The Digital Shoreline Analysis System (DSAS) tool, integrated into the ArcGIS software, was employed to monitor and analyze shoreline shifts, encompassing erosion and accretion. Various statistical parameters, including Net Shoreline Movement (NSM), End Point Rate (EPR), and Linear Regression Rate (LRR), were utilized to evaluate these changes. Additionally, the study aimed to discern the root causes of shoreline modifications in the study area, encompassing disturbances and the construction of new structures on these islands. The results conclusively demonstrated the substantial impact endured by these coastal islands, with accretion on both sides leading to the creation of new landmasses. This manuscript effectively illustrates that these islands have experienced marine transgression, notably evidenced by accretion. Anthropogenic activities were identified as the primary drivers behind the observed shoreline changes, underscoring the need for careful management and sustainable practices in these fragile coastal ecosystems.

Assessing the Impacts of Land Use, Land Cover, and Climate Change on the Hydrological Regime of a Humid Tropical Basin

Assessing the Impacts of Land Use, Land Cover, and Climate Change on the Hydrological Regime of a Humid Tropical Basin

Performance of Lower Ventilation Opening to Improve Air Change per Hour in Classroom at Tropical Humid Region (Case Study: Palembang City)

Fresh air circulation in a room had an impact on indoor air quality. In today’s pandemic, good fresh air circulation is one of the main strategies to prevent viruses from spreading through air molecules. A good ventilation opening design influences indoor air exchange. This research conducts a test on lower ventilation opening design that can maximize natural ventilation performance in a classroom. This test aimed at a recommendation for schools in the tropical humid region so they can hold offline learning with low virus spreads. Natural ventilation optimization should be a solution because not everyone can afford mechanical air filters or virus killers. This research used an experimental method. Computer simulation test variables were classroom openings consisting of existing openings, new outlets/openings, and lower ventilation opening. Parameters of observation are wind velocity, air circulation pattern, and air change per hour. This evaluation compares the experiment result to Air Change per Hour (ACH) threshold limit provision required in Indonesia. The result of the experiment shows outlet/opening addition provides a better impact on ACH escalation than with only existing classroom opening. And when the existing opening is closed, lower ventilation opening had good performance in achieving the ACH threshold limit provision requirements which were 9,8 ACH.

Variability of high dry matter orange‐fleshed sweetpotato [Ipomoea batatas (L.) Lam.] in later breeding stages and allocation of breeding resources in the humid tropics of Peru

AbstractOrange‐fleshed sweetpotato (OFSP) [Ipomoea batatas (L.) Lam] often lacks high dry matter (DM) in elite breeding material. The objectives were to examine the potential to combine yield with high root DM and high root β‐carotene (BC) content by variance‐covariance analysis and optimization of breeding scenarios for “OFSP dry and starchy,” which was exemplarily shown for the humid tropics of Peru. The trial series across seasons suggested a good chance to combine yield and quality (high DM and high BC). The unique data were used to estimate variance components and correlations among four yield traits and four quality traits. For the optimization of selections in our breeding program, we used the selection response by Cochran's approach and developed a small R script. Responses to selection were predicted for storage root yield and a modified Elston index aggregating eight traits. The differences between two‐ and three‐stage selection scenarios were small. For storage root yield, the recommended optimized two‐stage selection increased the response relative to the standard (one‐stage selection 100%) to 141.6% for 2268 plots and to 189.1% for 540 plots; the corresponding optimized three‐stage selection increased the response to 144.3% for 2268 plots and to 190.5% for 540 plots. A two‐stage selection is recommended with two to three locations at the first stage and 6–12 locations at the second stage, according to low‐ or high‐test capacity, respectively. Optimization of breeding schemes is much more important for smaller breeding programs than those with larger test capacity, and this allows testing even larger numbers of genotypes in a small breeding program.

Decolonizing Botany: Indonesia, UNESCO, and the Making of a Global Science.

Decolonization created new opportunities for international scientific research collaboration. In Indonesia this began in the late 1940s, as Indonesian scientists and officials sought to remake the formerly colonial botanical gardens in the city of Bogor into an international research center. Indonesia sponsored the Flora Malesiana project, a flora of all of island Southeast Asia. This project was formally centered in Bogor, Indonesia, with participation from tropical botanists from around the world. The international orientation of Indonesian science led to the establishment of one of UNESCO's Field Science Co-operation Offices in Jakarta, and to a period of close collaboration between Indonesian botanists and UNESCO. This paper examines the importance of UNESCO's Humid Tropics research program, which initiallyprovided further opportunities for Indonesian botanists to participate in international scientific networks. The paper concludes by showing that the Humid Tropics program led to the slow erosion of Indonesian agency and authority over tropical botany, and the assertion of Western control and management over tropical botany research.

Deep learning and automatic reference label harvesting for Sentinel-1 SAR-based rapid tropical dry forest disturbance mapping

The advent of temporally dense radar data such as the Sentinel-1 SAR have opened the door for rapid forest disturbance detection in the humid tropics. Tropical dry forest disturbance detection, however, were challenged by seasonality and more open canopy characteristics. In this manuscript, we proposed a Sentinel-1 SAR and deep learning based rapid forest disturbance detection approach for tropical dry forests. We demonstrated a weakly supervised method for reference label harvesting based on medium resolution globally available forest and forest disturbance maps. We trained a deep neural network model to derive forest and forest disturbance probabilities from Sentinel-1 images in the first step. We then implemented a probabilistic disturbance detection and refinement method to map forest disturbances in near real-time in two test regions in Paraguay and Mozambique. We mapped new forest disturbances in an emulated near real-time scenario for 2020 and 2021 and evaluated the spatial accuracy of the disturbance alerts by generating area adjusted precision, recall and F-1 score. We also evaluated the improvement in timeliness of disturbance detection by estimating mean time difference of disturbance events detection with that of Landsat-based GLAD alerts. The generated alerts in Paraguay and Mozambique achieved a precision, recall and F-1 score of 0.99, 0.61, 0.75 and 0.97, 0.51, 0.66, respectively. The proposed method detected disturbances with a mean of 21 days (± 18 days) earlier in Paraguay and 18 days (± 18 days) earlier in Mozambique than the Landsat-based GLAD alerts. These results demonstrated the efficacy of the proposed method and its viability to be used in an operational setting to generate large area rapid near real-time disturbance alerts in the dry tropics.

Urban green spaces and variation in cooling in the humid tropics: The case of Paramaribo

The urban climate affects more than half the world’s population, and urban green spaces are considered a nature-based solution to alleviate the urban heat island effect and adapt cities to climate change. Knowledge on urban green spaces cooling draws mostly on data from temperate climates, and similar research in humid tropical climates often focuses on the dry season. This study presents year-round temperature and humidity data for sixteen stationary sensors in Paramaribo, the capital of Suriname, and remotely sensed land surface temperatures for these locations. Analysis was done of diurnal and seasonal dynamics, the extent of urban green space cooling and the relation between locational characteristics and the micro-climate. Results show cooling up to 2.5 ºC with distinct seasonal patterns, and that locations exhibiting stronger cooling during the day have smaller temperature ranges of about 4 ºC at night compared to ranges of 5–7 ºC at other locations. Locations with more trees and complex vegetation structure have temperatures that are 1–5 ºC lower than other locations, but this cooling decreases when the ratio with impervious surfaces increases. Land surface temperature differences between more vegetated and built-up areas reach up to 2.5 ºC. High correlations found among micro-climate indicators imply easier comparison between studies when using any of these indicators, even if not the same ones. The longer term data collected in our study enables investigating urban green space cooling taking into account seasonality typical to the humid-tropics and finds that this cooling can help cities in the Caribbean region adapt to temperature extremes, despite high humidity. Our study further provides an example for overcoming data scarcity and contributes to developing strategies for mitigating increasing heat-related health risks in the humid tropics.

Forest resistance to drought in a humid tropical dipterocarp forest in the Western Ghats of India

AbstractDroughts are linked to tree die‐offs in the biodiverse humid tropics. We assessed drought response of a Dipterocarp Forest and found a marginal decrease in tree survival, indicating drought resistance. Understory and emergent species were sensitive to drought. Urgent focus is needed to understand drought impacts and plant physiological responses in South Asian forests.

A large‐scale survey reveals agro‐ecological factors influence spatio‐temporal distribution and epidemics of maize leaf blight: Implications for prioritizing sustainable management options

AbstractIntroductionProductivity of maize (Zea mays L.) is predominantly constrained by diseases, weeds, and insect pests. The northern leaf blight (NLB) disease, caused by Exserohilum turcicum, inflicts significant maize yield losses in the tropics and humid tropics, including Ethiopia. A large‐scale field survey was conducted to assess the spatio‐temporal distribution of maize NLB in southern Ethiopia, and to determine the association of maize farming practices and agro‐ecological factors with NLB epidemics during 2016–2019.Materials and MethodsA total of 814 maize farms were assessed in 12 major maize‐producing districts. During the assessment, data related to the disease, crop, farming practices and agro‐ecological factors were collected. The associations of disease severity with independent factors were determined using the ordinal logistic regression model.ResultsThe results showed that all studied districts and zones recorded high (≥85%) NLB prevalence over the 4 years, and the disease continues to be a major threat to maize production. Variable disease severity was recorded across districts/zones during the study periods. The highest (75.45%) mean severity was recorded from Boreda, followed by Konso (75.36%), Bonke (71.61%) and Derashe (71.30%), while Mihirab Abaya (33.25%) and Arba Minch (38.285%) districts recorded the lowest mean severity. In the multiple regression model, zone, altitude, cropping year, land preparation, NPS fertilization, weeding practice, growth stage and cropping system were highly significantly (p < 0.0001) associated with disease severity.ConclusionMaize cultivation at an altitude of ≤1500 m with intermediate to good weeding practices, recommended NPS (51–100 kg ha–1) fertilization, mixed‐ and intercropping systems, sparse plant (≤20 plants m‒2) population, and vegetative to blistering growth stages had significant relationships with low (≤25, 26%–50%) disease severity, and can be considered as management options to reduce NLB pressure and yield losses to sustainably ensure maize production and productivity.

Influence of Low Urea Fertilizer Rates on 1000-Seeds Weight of Maize (Zea mays L.) Varieties in a Tropical Humid Ecology

A field experiment was conducted from 2015 to 2018 at the Teaching and Research Farm of Federal College of Education (Technical), Omoku - Rivers State, Nigeria; to determine the influence of low urea fertilizer rates on 1000-seed weight of five maize (Zea mays L.) varieties. The experiment was laid-out in a RCBD with three replications. Treatment rates were 0, 30 and 60 kg N ha -1 . The maize varieties were Bende white, DMR-ESRY, Mangu white, Oba super II and Oba super 4. Soil and yield component data of 1000-seeds weights were collected and analyzed. Treatment means were separated using LSD at 5% (P < 0.05) probability level. The site had sandy soil texture with slightly acidic pH. Cations, organic C and total N were low except for Ca and Mg. Micronutrients were sufficient. The analyses presented in the seasons, showed that there was variation in seeds weights in accordance with the rates of urea applied. The minimum seed weight values were obtained in the control while the maximum weights were recorded at plots treated with 60kg N ha -1 . The 1000-seeds weight of Mangu white (208.03 g) was significantly different amongst the other varieties. All the maize varieties attained maximum weight gain at 60 kg N/ha. 60 kg/ha is preferable for Mangu white variety on the sandy soil of Omoku for low input maize production.

Effect of tree shade on behavior and haircoat temperature of grazing dual-purpose cows in a hot and humid tropical environment

We evaluated the behavior and skin temperature of dual-purpose cattle that grazed pastures having high (HC), low (LC), and no (NC) tree cover during the rainy and dry seasons in the hot and humid tropics of Mexico. We observed twenty-four adult cows (eight per treatment) over 24 days during each season, recording skin temperature and the time related to different daily activities. Across treatments, cows spent the same amount of time foraging during the rainy season (P > 0.05), but cows under HC spent less time during the dry season (P < 0.0001). During the rainy season, cows under HC showed more motivation to continue grazing than becoming restless or beginning rumination (P < 0.001) or roaming more than in other treatments (P < 0.001). During the dry season, cows under HC and LC also had less probability of initiating rest than NC (P < 0.001). Cows under HC had greater motivation to transition from grazing to roaming and less incentive to pass from rumination to rest than cows under LC and NC (P < 0.001). The frequency of water consumption was greater during the dry season (P < 0.001) and consistently high under NC (P < 0.0001). Skin temperature did not differ among treatments during the rainy season (P = 0.261), but during the dry season, it was greater under NC (P < 0.001). Tree cover improves cow behaviors by increasing the impetus to graze and perform daily activities, which contributes to reduced skin temperature during hotter seasons.

Insulin-like growth factor-1 (Igfi) gene polymorphism and its effect on egg quality traits of three chicken genotypes reared in hot humid tropics

A study was conducted on the effect of gene polymorphism of Insulin like Growth Factor-1 (IGFI) on egg quality traits in three chicken genotypes. A total of 250 chicken comprising 150 FUNAAB-Alpha (50 Normal feather, 50 Naked neck and 50 Frizzle feather), 50 Kuroiler and 50 Sasso were used for this experiment. At point of lay, 30 hens per genotype were selected and transferred into a battery cage of one unit per bird. Data was collected on the egg quality traits, 30 eggs for each genotype was collected. All collected data was subject to analysis of variance using a completely randomized design, of which genotype was the interest factor. At 16 weeks, 1ml of blood was collected from each hen and extraction of genomic DNA from the blood was done. PCR was conducted using the pair of primer and condition as described by Nagaraga, et al. (2000). The PCR amplicons were digested using PstI restriction enzymes following the manufacturer’s procedure. The resulting fragments were analyzed using GenAnalyzer (GenAlEx 6.502) was used for the genetic diversity of the IGFI locus. This data was subject to the PROC GLM of SAS 9.2. Results showed the chicken genotypes significantly (P&lt;0.05) affect all the egg-quality traits except the shell weight, yolk ratio and albumen ratio. The IGFI gene polymorphism had no significant effect (P&gt;0.05) on egg quality traits for except the egg length and egg width.&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; Une étude a été menée sur l’effet du polymorphisme génique du facteur de croissance analogue à l'insuline (IGFI) sur les caractéristiques de qualité des œufs chez trois génotypes de poulet. Un total de 250 poulets comprenant 150 FUNAAB-Alpha (50 plumes normales, 50 cou nu et 50 plumes Frizzle), 50 Kuroiler et 50 Sasso ont été utilisés pour cette expérience. Au moment de la ponte, 30 poules par génotype ont été sélectionnées et transférées dans une cage en batterie d'une unité par oiseau. Des données ont été collectées sur les traits de qualité des œufs, 30 œufs pour chaque génotype ont été collectés. Toutes les données recueillies ont fait l'objet d'une analyse de variance selon un design complètement randomisé, dont le génotype était le facteur d'intérêt. À 16 semaines, 1 ml de sang a été prélevé sur chaque poule et l'extraction de l'ADN génomique du sang a été effectuée. La PCR a été réalisée en utilisant la paire amorce et condition décrite par Nagaraga et al. (2000). Les amplicons PCR ont été digérés à l'aide d'enzymes de restriction PstI selon la procédure du fabricant. Les fragments résultants ont été analysés à l'aide de GenAnalyzer (GenAlEx 6.502) a été utilisé pour la diversité génétique du locus IGFI. Ces données ont été soumises au PROC GLM de SAS 9.2. Les résultats ont montré que les génotypes de poulet affectent de manière significative (P &lt;0,05) tous les caractères de qualité des œufs, à l'exception du poids de la coquille, du rapport de jaune et du rapport d'albumen. Le polymorphisme du gène IGFI n'a eu aucun effet significatif (P&gt;0,05) sur les caractères de qualité des œufs, sauf la longueur et la largeur des œufs.

A Comparative Study of the Performance of Noiler and Broiler Birds in Tropical Humid Zone (South-East Nigeria)

The purpose of this study was to evaluate the performance of broiler and noiler birds. A total of 36 (thirty-six) day old unsexed broiler (Casacada) and noiler birds were sourced from Ibadan, South-western and Amo Farm from Owerri, South-eastern Nigeria respectively. After brooding, the chicks were randomly divided into two treatment groups of eighteen birds each. They were replicated twice and were fed with equal amount of commercial broiler finisher. The feed intake, feed conversion ratio and body weight gain were determined. There was a significant difference (p&lt;0.05) between the two treatments with the highest weight gain in T2 at 1.885kg and the lowest weight gain in T1 at 1.237kg. There was a significant increase in the body weight gain, feed intake and feed conversion ratio of broiler birds across the treatments. It was therefore, concluded that broiler birds have better feed efficiency than the noilers. Keywords: Comparative, Study, Performance, Noiler, Broiler, Birds, Humid, Zone, Nigeria

Seasonal variation of arthropod diversity in agroforestry systems in the humid tropics of Mexico

Seasonal variation of arthropod diversity in agroforestry systems in the humid tropics of Mexico

Thermal Comfort in Humid Tropical Climate Areas (Case Study on Open Spaces and Shaded Spaces in Medan City)

Humid tropical climates are areas with high humidity temperature characteristics. This high temperature is partly due to sunlight which is always constant throughout the day, while high humidity is usually associated with relatively high rainfall. Because of this, in general, buildings in this area have a fairly wide canopy or what is often referred to as a shading element in architecture. This will ultimately affect the thermal comfort of buildings in the humid tropics. In this study the authors tried to look at the two main factors that shape thermal comfort, namely the level of temperature and humidity. The author will compare three types of outdoor spaces, namely sheltered outdoor spaces with walls on one side, shaded rooms without walls and outdoor spaces without shade. The research was conducted by measuring temperature and humidity simultaneously at the three locations. Measurements were carried out for two weeks, at five different times with an interval of two hours. The results obtained show that there are significant differences in temperature and humidity between open spaces and shaded spaces. Where the shaded room has lower temperature and humidity. As for other shaded rooms, it is known that shaded rooms without walls have lower temperature and humidity.

Variation in the Drought Tolerance of Tropical Understory Plant Communities across an Extreme Elevation and Precipitation Gradient.

Little is known about how differences in water availability within the "super humid" tropics can influence the physiology of understory plant species and the composition of understory plant communities. We investigated the variation in the physiological drought tolerances of hundreds of understory plants in dozens of plant communities across an extreme elevation and precipitation gradient. Specifically, we established 58 understory plots along a gradient of 400-3600 m asl elevation and 1000-6000 mm yr-1 rainfall in and around Manu National Park in southeastern Peru. Within the plots, we sampled all understory woody plants and measured three metrics of physiological leaf drought tolerance-turgor loss point (TLP), cuticular conductance (Gmin), and solute leakage (SL)-and assessed how the community-level means of these three traits related to the mean annual precipitation (MAP) and elevation (along the study gradient, the temperature decreases linearly, and the vapor pressure deficit increases monotonically with elevation). We did not find any correlations between the three metrics of leaf drought tolerance, suggesting that they represent independent strategies for coping with a low water availability. Despite being widely used metrics of leaf drought tolerance, neither the TLP nor Gmin showed any significant relationships with elevation or the MAP. In contrast, SL, which has only recently been developed for use in ecological field studies, increased significantly at higher precipitations and at lower elevations (i.e., plants in colder and drier habitats have a lower average SL, indicating greater drought tolerances). Our results illustrate that differences in water availability may affect the physiology of tropical montane plants and thus play a strong role in structuring plant communities even in the super humid tropics. Our results also highlight the potential for SL assays to be efficient and effective tools for measuring drought tolerances in the field.