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In order to test hypotheses about changes in the environment induced by man, including climatic change, ecologists are sampling portions of the environment repeatedly across time. This paper describes a method for testing a space-time interaction in repeated ecological survey data, when there is no replication at the level of individual sampling units (sites). This methodological development is important for the analysis of long-term monitoring data, including systems under anthropogenic influence. In these systems, an interaction may indicate that the spatial structure of community composition has changed in the course of time or that the temporal evolution is not the same at all sites. This paper describes ANOVA models corresponding to the steps leading to a solution to the problem, which is based on the representation of space and time by principal coordinates of neighbor matrices (PCNM eigenfunctions) in the ANOVA. Numerical simulations showed that ANOVA Model 5 was the model of choice for the analysis of the space-time interaction because it always had correct rates of Type I error, and its power was always equal to or higher than those of other possible models of analysis. If the hypothesis of absence of interaction is not rejected, one cannot conclude that a change has occurred in the spatial structure of the response data across time; one should follow the ordinary rules of two-way ANOVA if testing the significance of the main factors is of interest. If the hypothesis of absence of interaction is rejected, one should model the spatial structure of each time period in a separate way. One can also conduct a single test involving a separate model of the spatial structure for each time period. This paper presents two applications to real ecological data. [ABSTRACT FROM AUTHOR]

This paper estimates national methane emissions from solid waste disposal sites in Panama over the time period 1990-2020 using both the 2006 Intergovernmental Panel on Climate Change (IPCC) Waste Model spreadsheet and the default emissions estimate approach presented in the 1996 IPCC Good Practice Guidelines. The IPCC Waste Model has the ability to calculate emissions from a variety of solid waste disposal site types, taking into account country- or region-specific waste composition and climate information, and can be used with a limited amount of data. Countries with detailed data can also run the model with country-specific values. The paper discusses methane emissions from solid waste disposal; explains the differences between the two methodologies in terms of data needs, assumptions, and results; describes solid waste disposal circumstances in Panama; and presents the results of this analysis. It also demonstrates the Waste Model's ability to incorporate landfill gas recovery data and to make projections. The former default method methane emissions estimates are 25 Gg in 1994, and range from 23.1 Gg in 1990 to a projected 37.5 Gg in 2020. The Waste Model estimates are 26.7 Gg in 1994, ranging from 24.6 Gg in 1990 to 41.6 Gg in 2020. Emissions estimates for Panama produced by the new model were, on average, 8% higher than estimates produced by the former default methodology. The increased estimate can be attributed to the inclusion of all solid waste disposal in Panama (as opposed to only disposal in managed landfills), but the increase was offset somewhat by the different default factors and regional waste values between the 1996 and 2006 IPCC guidelines, and the use of the first-order decay model with a time delay for waste degradation in the IPCC Waste Model. [ABSTRACT FROM AUTHOR]

National, regional, and international actors can use a range of different policies to increase the demand for forest-based carbon sequestration. Demand for these services has, the potential to significantly impact the decisions of landowners, land managers, and private investors by increasing the incentives for creation or maintenance of forest ecosystems. The Kyoto process is at the center of discussions regarding the market for carbon services although it is not the only relevant source of demand. The authors recommend an approach to climate change regulation that requires actions beyond the current scope and term of the Kyoto Protocol. The four areas addressed in this paper are: (1) increasing regulation-based demand for carbon reductions by improved implementation and increasing coverage, (2) increasing voluntary demand for carbon reductions, (3) increasing the percentage of carbon reduction that derives from land use, land use change, and forestry, and (4) ways to stimulate demand for forest-based carbon sequestration generally by reducing transaction costs and contractual risks and in a particular country by recommending policy changes in Panama. [ABSTRACT FROM AUTHOR]

The eastern tropical Pacific is oceanographically unfavorable for coral-reef development. Nevertheless, reefs have persisted there for the last 7000 years. Rates of vertical accretion during the Holocene have been similar in the strong-upwelling Gulf of Panamá (GoP) and the adjacent, weak-upwelling Gulf of Chiriquí (GoC); however, seasonal upwelling in the GoP exacerbated a climate-driven hiatus in reef development in the late Holocene. The situation is now reversed and seasonal upwelling in the GoP currently buffers thermal stress, creating a refuge for coral growth. We developed carbonate budget models to project the capacity of reefs in both gulfs to keep up with future sea-level rise. On average, the GoP had significantly higher net carbonate production rates than the GoC. With an estimated contemporary reef-accretion potential (RAP) of 5.5 mm year−1, reefs in the GoP are projected to be able to keep up with sea-level rise if CO2 emissions are reduced, but not under current emissions trajectories. With an estimated RAP of just 0.3 mm year−1, reefs in the GoC are likely already unable to keep up with contemporary sea-level rise in Panamá (1.4 mm year−1). Whereas the GoP has the potential to support functional reefs in the near-term, our study indicates that their long-term persistence will depend on reduction of greenhouse gases. [ABSTRACT FROM AUTHOR]

Abstract: Increasing dominance of lianas in many tropical forests is considered a fingerprint of global environmental change. Despite the key role they play in ecosystem functioning, lianas remain one of the least studied life forms in tropical environments. This paper contrasts leaf traits and spectral properties (400–1100 nm) of liana and tree communities from a tropical dry forest and a tropical rainforest in Panama, Central America. Differences between lianas and tree leaf traits were analyzed using spectroscopy, leaf histology and pigment extractions. Results from this study indicate that many of the biochemical, structural, and optical properties of lianas and trees are different in the dry forest site but not in rainforest sites. In the dry forest site, liana leaves exhibited significantly lower chlorophyll and carotenoid contents and were thinner than the leaves of their host trees. Specific leaf area, dry to fresh mass ratio, and mean water content of liana leaves were significantly higher when compared with tree leaves. The differences observed in the tropical dry forest site indicate that lianas may have a higher rate of resource acquisition and usage, whereas trees tend to conserve acquired resources. We suggest that our results may be indicative of the presence of a liana syndrome related to water availability and thus best exhibited in tropical dry forests. Our findings have important implications for using remote sensing to accurately map the distribution of liana communities at regional scales and for the continued expansion of lianas in tropical environments as a result of global change. [Copyright &y& Elsevier]

A mechanistic understanding of how tropical-tree mortality responds to climate variation is urgently needed to predict how tropical-forest carbon pools will respond to anthropogenic global change, which is altering the frequency and intensity of storms, droughts, and other climate extremes in tropical forests. We used 5 years of approximately monthly drone-acquired RGB (red–green–blue) imagery for 50 ha of mature tropical forest on Barro Colorado Island, Panama, to quantify spatial structure; temporal variation; and climate correlates of canopy disturbances, i.e., sudden and major drops in canopy height due to treefalls, branchfalls, or the collapse of standing dead trees. Canopy disturbance rates varied strongly over time and were higher in the wet season, even though wind speeds were lower in the wet season. The strongest correlate of monthly variation in canopy disturbance rates was the frequency of extreme rainfall events. The size distribution of canopy disturbances was best fit by a Weibull function and was close to a power function for sizes above 25 m 2. Treefalls accounted for 74 % of the total area and 52 % of the total number of canopy disturbances in treefalls and branchfalls combined. We hypothesize that extremely high rainfall is a good predictor because it is an indicator of storms having high wind speeds, as well as saturated soils that increase uprooting risk. These results demonstrate the utility of repeat drone-acquired data for quantifying forest canopy disturbance rates at fine temporal and spatial resolutions over large areas, thereby enabling robust tests of how temporal variation in disturbance relates to climate drivers. Further insights could be gained by integrating these canopy observations with high-frequency measurements of wind speed and soil moisture in mechanistic models to better evaluate proximate drivers and with focal tree observations to quantify the links to tree mortality and woody turnover. [ABSTRACT FROM AUTHOR]

Photosynthetic carbon uptake by tropical forests is of critical importance in regulating the earth's climate, but rising temperatures threaten this stabilizing influence of tropical forests. Most research on how temperature affects photosynthesis focuses on fully sun-exposed leaves, and little is known about shade leaves, even though shade leaves greatly outnumber sun leaves in lowland tropical forests. We measured temperature responses of light-saturated photosynthesis, stomatal conductance, and the biochemical parameters V CMax (maximum rate of RuBP carboxylation) and J Max (maximum rate of RuBP regeneration, or electron transport) on sun and shade leaves of mature tropical trees of three species in Panama. As expected, biochemical capacities and stomatal conductance were much lower in shade than in sun leaves, leading to lower net photosynthesis rates. However, the key temperature response traits of these parameters—the optimum temperature (T Opt) and the activation energy—did not differ systematically between sun and shade leaves. Consistency in the J Max to V CMax ratio further suggested that shade leaves are not acclimated to lower temperatures. For both sun and shade leaves, stomatal conductance had the lowest temperature optimum (~25  ° C), followed by net photosynthesis (~30 °C), J Max (~34  ° C) and V CMax (~38  ° C). Stomatal conductance of sun leaves decreased more strongly with increasing vapor pressure deficit than that of shade leaves. Consistent with this, modeled stomatal limitation of photosynthesis increased with increasing temperature in sun but not shade leaves. Collectively, these results suggest that modeling photosynthetic carbon uptake in multi-layered canopies does not require independent parameterization of the temperature responses of the biochemical controls over photosynthesis of sun and shade leaves. Nonetheless, to improve the representation of the shade fraction of carbon uptake dynamics in tropical forests, better understanding of stomatal sensitivity of shade leaves to temperature and vapor pressure deficit will be required. [ABSTRACT FROM AUTHOR]

Summary: Tropical forests are increasingly being subjected to hotter, drier conditions as a result of global climate change. The effects of drought on forests along successional gradients remain poorly understood. We took advantage of the 2015–2016 El Niño event to test for differences in drought response along a successional gradient by measuring the sap flow in 76 trees, representing 42 different species, in 8‐, 25‐ and 80‐yr‐old secondary forests in the 15‐km2 ‘Agua Salud Project’ study area, located in central Panama. Average sap velocities and sapwood‐specific hydraulic conductivities were highest in the youngest forest. During the dry season drought, sap velocities increased significantly in the 80‐yr‐old forest as a result of higher evaporative demand, but not in younger forests. The main drivers of transpiration shifted from radiation to vapor pressure deficit with progressing forest succession. Soil volumetric water content was a limiting factor only in the youngest forest during the dry season, probably as a result of less root exploration in the soil. Trees in early‐successional forests displayed stronger signs of regulatory responses to the 2015–2016 El Niño drought, and the limiting physiological processes for transpiration shifted from operating at the plant–soil interface to the plant–atmosphere interface with progressing forest succession. [ABSTRACT FROM AUTHOR]

Background: High fidelity carbon mapping has the potential to greatly advance national resource management and to encourage international action toward climate change mitigation. However, carbon inventories based on field plots alone cannot capture the heterogeneity of carbon stocks, and thus remote sensing-assisted approaches are critically important to carbon mapping at regional to global scales. We advanced a high-resolution, national-scale carbon mapping approach applied to the Republic of Panama - one of the first UN REDD + partner countries. Results: Integrating measurements of vegetation structure collected by airborne Light Detection and Ranging (LiDAR) with field inventory plots, we report LiDAR-estimated aboveground carbon stock errors of ~10% on any 1-ha land parcel across a wide range of ecological conditions. Critically, this shows that LiDAR provides a highly reliable replacement for inventory plots in areas lacking field data, both in humid tropical forests and among drier tropical vegetation types. We then scale up a systematically aligned LiDAR sampling of Panama using satellite data on topography, rainfall, and vegetation cover to model carbon stocks at 1-ha resolution with estimated average pixel-level uncertainty of 20.5 Mg C ha-1 nationwide. Conclusions: The national carbon map revealed strong abiotic and human controls over Panamanian carbon stocks, and the new level of detail with estimated uncertainties for every individual hectare in the country sets Panama at the forefront in high-resolution ecosystem management. With this repeatable approach, carbon resource decision-making can be made on a geospatially explicit basis, enhancing human welfare and environmental protection. [ABSTRACT FROM AUTHOR]

Aim We examined and compared population genetic structure in a suite of four co-occurring Panamanian tree species and performed coalescent-based analyses of demographic history to evaluate hypotheses of tropical vegetation change during the Last Glacial Maximum ( LGM). Location Isthmus of Panama. Methods Nuclear microsatellite variation was assayed in multiple populations (1179 trees, 21 locations, 6-13 locations per species) in Jacaranda copaia (Bignoniaceae), Luehea seemannii (Malvaceae), Simarouba amara (Simaroubaceae) and Symphonia globulifera (Clusiaceae). Population structure was analysed using FST-based statistics and a Bayesian clustering approach ( baps). Bayesian coalescent methods ( msvar) were used to infer demographic histories. Results High levels of genetic diversity were found in all of the species ( HE range, 0.56-0.79). Jacaranda copaia and L. seemannii showed lower FST and fewer Bayesian clusters across similar spatial scales than did S. globulifera and Simarouba amara. For each species examined, the current effective population sizes ( Ne) are much lower than ancient Ne, within all inferred baps demes. In light-demanding pioneer species J. copaia, L. seemannii and S. amara, estimates of the number of generations since the bottleneck events overlap with the end of the LGM (median site posterior estimates ranged from 16 to 19 ka) while Symphonia globulifera estimates are consistent with earlier population declines (median 202 ka) in the early Pleistocene and late Pliocene. Main conclusions The wind-dispersed deciduous species J. copaia and L. seemannii showed lower FST and spatially extensive demes, while the animal-dispersed evergreen Symphonia globulifera and Simarouba amara showed spatially restrictive demes and higher FST. Each deme examined shows evidence of historical bottlenecks. For three of the four species which are also light-demanding pioneer species, the mean estimated time and 95% highest posterior density of the bottleneck events coincides with the end of the LGM. These results suggest that these species have undergone historical bottlenecks as a result of reduced forest cover during the Pleistocene and provide evidence of shared demographic histories among co-occurring tropical forest trees. [ABSTRACT FROM AUTHOR]

The emergence and closure of the Isthmus of Panama had regional and global impacts that were rivalled by few other Cenozoic geological events. The closure of the Central American Seaway and the rise of the Isthmus had dramatic affects on climate and air and oceanic currents worldwide. Formation of the Isthmus also drove terrestrial biotic interchange, ending the isolation of South America by permitting the mixing of its biota with that of North and Central America. A dated phylogenetic tree of a well-sampled clade of palms in the tribe Trachycarpeae ( Copernicia, Pritchardia and Washingtonia) was used to conduct biogeographical analyses. Examination of the timing of lineage dispersal from North into South America was performed and two contrasting temporal hypotheses of the Isthmus formation were tested: occurrence in the Pliocene ( c. 5 Mya to the present) or in the Miocene (prior to c. 5 Mya). Copernicia is inferred to have dispersed through the Isthmus of Panama region into South America and subsequently into the Caribbean, where it underwent a rapid radiation. Consistent with a geologically older age for the Isthmus than previously understood, our results support recent geological and palaeobiological data that suggest an early Oligocene to early Miocene model of evolution of the Isthmus of Panama. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, ••, ••-••. [ABSTRACT FROM AUTHOR]

It has been suggested that a "permanent" El Niño climate state has existed in the warm Pliocene. One of the main pieces of evidence of such conditions is the small eastwest sea surface temperature (SST) difference that is found in proxy temperature records of the equatorial Pacific. Using a coupled version of the Zebiak-Cane model of intermediate complexity for the tropical Pacific, we study the sensitivity of the time-mean Pacific background state and El Niño/Southern Oscillation (ENSO) variability to Pliocene climate changes. The parameters varied in this sensitivity study include changes in the trade wind strength due to a reduced equator-to-pole temperature gradient, higher global mean temperatures and an open Panama gateway. All these changes lead to a westward shift of the position of the cold tongue along the equator by up to 2000 km. This result is consistent with data from the PRISM3D Pliocene SST reconstruction. Our model further suggests that ENSO variability is present in the Pliocene climate with only slight changes as compared to today. A background climate that would resemble a "permanent" El Niño with weak to no east-west temperature difference along the equator is only found for very weak trade winds which seem unrealistic for the Pliocene climate. [ABSTRACT FROM AUTHOR]

We censused butterflies flying across the Panama Canal at Barro Colorado Island (BCI) for 16 years and butterfly hostplants for 8 years to address the question: What environmental factors influence the timing and magnitude of migrating Aphrissa statira butterflies? The peak migration date was earlier when the wet season began earlier and when soil moisture content in the dry season preceding the migration was higher. The peak migration date was also positively associated with peak leaf flushing of one hostplant ( Callichlamys latifolia) but not another ( Xylophragma seemannianum). The quantity of migrants was correlated with the El Niño Southern Oscillation, which influenced April soil moisture on BCI and total rainfall in the dry season. Both hostplant species responded to El Niño with greater leaf flushing, and the number of adults deriving from or laying eggs on those new leaves was greatest during El Niño years. The year 1993 was exceptional in that the number of butterflies migrating was lower than predicted by the El Niño event, yet the dry season was unusually wet for an El Niño year as well. Thus, dry season rainfall appears to be a primary driver of larval food production and population outbreaks for A. statira. Understanding how global climate cycles and local weather influence tropical insect migrations improves the predictability of ecological effects of climate change. [ABSTRACT FROM AUTHOR]

The impacts of global change on tropical forests remain poorly understood. We examined changes in tree growth rates over the past two decades for all species occurring in large (50-ha) forest dynamics plots in Panama and Malaysia. Stem growth rates declined significantly at both forests regardless of initial size or organizational level (species, community or stand). Decreasing growth rates were widespread, occurring in 24–71% of species at Barro Colorado Island, Panama (BCI) and in 58–95% of species at Pasoh, Malaysia (depending on the sizes of stems included). Changes in growth were not consistently associated with initial growth rate, adult stature, or wood density. Changes in growth were significantly associated with regional climate changes: at both sites growth was negatively correlated with annual mean daily minimum temperatures, and at BCI growth was positively correlated with annual precipitation and number of rainfree days (a measure of relative insolation). While the underlying cause(s) of decelerating growth is still unresolved, these patterns strongly contradict the hypothesized pantropical increase in tree growth rates caused by carbon fertilization. Decelerating tree growth will have important economic and environmental implications. [ABSTRACT FROM AUTHOR]

Although patterns of tree species distributions along environmental gradients have been amply documented in tropical forests, mechanisms causing these patterns are seldom known. Efforts to evaluate proposed mechanisms have been hampered by a lack of comparative data on species’ reactions to relevant axes of environmental variation. Here we show that differential drought sensitivity shapes plant distributions in tropical forests at both regional and local scales. Our analyses are based on experimental field assessments of drought sensitivity of 48 species of trees and shrubs, and on their local and regional distributions within a network of 122 inventory sites spanning a rainfall gradient across the Isthmus of Panama. Our results suggest that niche differentiation with respect to soil water availability is a direct determinant of both local- and regional-scale distributions of tropical trees. Changes in soil moisture availability caused by global climate change and forest fragmentation are therefore likely to alter tropical species distributions, community composition and diversity. [ABSTRACT FROM AUTHOR]