Alvaro Duque | Universidad Nacional de Colombia Sede Medellin (original) (raw)

Papers by Alvaro Duque

The future trajectory of global forests is closely intertwined with tree demography, and a major ... more The future trajectory of global forests is closely intertwined with tree demography, and a major fundamental goal in ecology is to understand the key mechanisms governing spatial-temporal patterns in tree population dynamics. While historical research has made substantial progress in identifying the mechanisms individually, their relative importance among forests remains unclear mainly due to practical limitations. One approach is to group mechanisms according to their shared effects on the variability of tree vital rates and to quantify patterns therein. We developed a conceptual and statistical framework (variance partitioning of Bayesian multilevel models) that attributes the variability in tree growth, mortality, and recruitment to variation in species, space, and time, and their interactions, categories we refer to asorganising principles(OPs). We applied the framework to data from 21 forest plots covering more than 2.9 million trees of approximately 6,500 species. We found tha...

Nature, 2018

Global warming is forcing many species to shift their distributions upward, causing consequent ch... more Global warming is forcing many species to shift their distributions upward, causing consequent changes in the compositions of species that occur at specific locations. This prediction remains largely untested for tropical trees. Here we show, using a database of nearly 200 Andean forest plot inventories spread across more than 33.5° latitude (from 26.8° S to 7.1° N) and 3,000-m elevation (from 360 to 3,360 m above sea level), that tropical and subtropical tree communities are experiencing directional shifts in composition towards having greater relative abundances of species from lower, warmer elevations. Although this phenomenon of 'thermophilization' is widespread throughout the Andes, the rates of compositional change are not uniform across elevations. The observed heterogeneity in thermophilization rates is probably because of different warming rates and/or the presence of specialized tree communities at ecotones (that is, at the transitions between distinct habitats, such as at the timberline or at the base of the cloud forest). Understanding the factors that determine the directions and rates of compositional changes will enable us to better predict, and potentially mitigate, the effects of climate change on tropical forests.

Frontiers in Forests and Global Change, 2020

Due to global warming, many species will face greater risks of thermal stress, which can lead to ... more Due to global warming, many species will face greater risks of thermal stress, which can lead to changes in performance, abundance, and/or geographic distributions. In plants, high temperatures above a species-specific critical thermal maximum will permanently damage photosystem II, leading to decreased electron transport rates, photosynthetic failure, and eventual leaf and plant death. Previous studies have shown that plant thermal tolerances vary with latitude, but little is known about how they change across smaller-scale thermal gradients (i.e., with elevation) or about how these thermal tolerances relate to species' local performances and geographic distributions. In this study, we assess the maximum photosynthetic thermal tolerances (T 50) of nearly 200 tropical tree species growing in 10 forest plots distributed across a >2,500 m elevation gradient (corresponding to a 17 • C temperature gradient) in the northern Andes Mountains of Colombia. Using these data, we test the relationships between species' thermal tolerances and (1) plot elevations and temperatures, (2) species' largescale geographic distributions, and (3) changes in species' abundances through time within the plots. We found that species' T 50 do in fact decrease with plot elevation but significantly slower than the corresponding adiabatic lapse rate (−0.4 vs. −5.7 • C km −1) and that there remains a large amount of unexplained variation in the thermal tolerances of co-occurring tree species. There was only a very weak association between species' thermal tolerances and their large-scale geographic distributions and no significant relationships between species' thermal tolerances and their changes in relative abundance through time. A potential explanation for these results is that thermal tolerances are adaptations to extreme leaf temperatures that can be decoupled from regional air temperatures due to microclimatic variations and differences in the species' leaf thermoregulatory properties.

Science, 2013

Introduction Recent decades have seen a major international effort to inventory tree communities ... more Introduction Recent decades have seen a major international effort to inventory tree communities in the Amazon Basin and Guiana Shield (Amazonia), but the vast extent and record diversity of these forests have hampered an understanding of basinwide patterns. To overcome this obstacle, we compiled and standardized species-level data on more than half a million trees in 1170 plots sampling all major lowland forest types to explore patterns of commonness, rarity, and richness. Methods The ~6-million-km 2 Amazonian lowlands were divided into 1° cells, and mean tree density was estimated for each cell by using a loess regression model that included no environmental data but had its basis exclusively in the geographic location of tree plots. A similar model, allied with a bootstrapping exercise to quantify sampling error, was used to generate estimated Amazon-wide abundances of the 4962 valid species in the data set. We estimated the total number of tree species in the Amazon by fitting t...

Biogeosciences, Jul 25, 2012

High-resolution mapping of tropical forest carbon stocks can assist forest management and improve... more High-resolution mapping of tropical forest carbon stocks can assist forest management and improve implementation of large-scale carbon retention and enhancement programs. Previous high-resolution approaches have relied on field plot and/or light detection and ranging (LiDAR) samples of aboveground carbon density, which are typically upscaled to larger geographic areas using stratification maps. Such efforts often rely on detailed vegetation maps to stratify the region for sampling, but existing tropical forest maps are often too coarse and field plots too sparse for highresolution carbon assessments. We developed a top-down approach for high-resolution carbon mapping in a 16.5 million ha region (> 40 %) of the Colombian Amazon-a remote landscape seldom documented. We report on three advances for large-scale carbon mapping: (i) employing a universal approach to airborne LiDAR-calibration with limited field data; (ii) quantifying environmental controls over carbon densities; and (iii) developing stratification-and regression-based approaches for scaling up to regions outside of LiDAR coverage. We found that carbon stocks are predicted by a combination of satellite-derived elevation, fractional canopy cover and terrain ruggedness, allowing upscaling of the LiDAR samples to the full 16.5 million ha region. LiDAR-derived carbon maps have 14 % uncertainty at 1 ha resolution, and the regional map based on stratification has 28 % uncertainty in any given hectare. High-resolution approaches with quantifiable pixel-scale uncertainties will provide the most confidence for monitoring changes in tropical forest carbon stocks. Improved confidence will allow resource managers and decision makers to more rapidly and effectively implement actions that better conserve and utilize forests in tropical regions.

Nature Ecology & Evolution

Making forest data fair and open Data on tropical forests are in high demand. But ground forest m... more Making forest data fair and open Data on tropical forests are in high demand. But ground forest measurements are hard to sustain and the people who make them are extremely disadvantaged compared to those who use them. We propose a new approach to forest data that focuses on the needs of data originators, and ensures users and funders contribute properly.

New Phytologist, 2022

Summary Tree size shapes forest carbon dynamics and determines how trees interact with their envi... more Summary Tree size shapes forest carbon dynamics and determines how trees interact with their environment, including a changing climate. Here, we conduct the first global analysis of among‐site differences in how aboveground biomass stocks and fluxes are distributed with tree size. We analyzed repeat tree censuses from 25 large‐scale (4–52 ha) forest plots spanning a broad climatic range over five continents to characterize how aboveground biomass, woody productivity, and woody mortality vary with tree diameter. We examined how the median, dispersion, and skewness of these size‐related distributions vary with mean annual temperature and precipitation. In warmer forests, aboveground biomass, woody productivity, and woody mortality were more broadly distributed with respect to tree size. In warmer and wetter forests, aboveground biomass and woody productivity were more right skewed, with a long tail towards large trees. Small trees (1–10 cm diameter) contributed more to productivity an...

Global Change Biology, 2022

The growth and survival of individual trees determine the physical structure of a forest with imp... more The growth and survival of individual trees determine the physical structure of a forest with important consequences for forest function. However, given the diversity of tree species and forest biomes, quantifying the multitude of demographic strategies within and across forests and the way that they translate into forest structure and function remains a significant challenge. Here, we quantify the demographic rates of 1961 tree species from temperate and tropical forests and evaluate how demographic diversity (DD) and demographic composition (DC) differ across forests, and how these differences in demography relate to species richness, aboveground biomass (AGB), and carbon residence time. We find wide variation in DD and DC across forest plots, patterns that are not explained by species richness or climate variables alone. There is no evidence that DD has an effect on either AGB or carbon residence time. Rather, the DC of forests, specifically the relative abundance of large statur...

This third volume of the annual report on biodiversity in Colombia continues the editorial line t... more This third volume of the annual report on biodiversity in Colombia continues the editorial line that begun in 2014. Using novel analytical and graphic proposals, these reports have the goal of communicating the contents to a broad public, making it available for discussion without sacrificing the quality of information. The challenge of communication continues to be a major part of the institutional project, and the new languages with which we are learning to communicate with society and other institutions are an experiment that we expect to be increasingly gratifying. The report for 2017 is already under construction and it counts on new digital technologies so the power of a colombian vital connection may be entirely expressed. The included content evidences that we are still far away from having a systematic follow-up about most of the topics related to the management of biodiversity and ecosystem services, which is the only way to evaluate the effectiveness of policies and investments made by society. In fact, a limitation that is recognized is that of identifying positive or negative changes that affect different levels of organization of life on this planet; therefore, our global navigation route of the Aichi targets is still to be verified. An additional purpose of this process includes the invitation of all Colombians to contribute in constructing and maintaining basic monitoring indicators for management since it is impossible to identify long-term trends of flora and fauna in the country without the support of institutions, researchers, and citizens. This challenge is immense in a megadiverse country such as Colombia. For this reason, the report will continue to open its pages to experts, and even indigenous peoples or local communities, for them to present their perspectives about environmental change and its effects on biodiversity in a systematic and documented manner. This has the objective of stimulating the commitment of everyone in the management of biodiversity and ecosystem services. The only way of overcoming the risk of extinction is through the active process of social learning in which all sectors assume a part of the complex responsibility in protecting the forms of life of the country, a roughly counted tenth of all creatures on Earth. I thank all the people that contributed in this Report, those who have supported us in the phases of production, and all readers and users, who are the ultimate judges of its utility.Bogotá, D. C

Journal of Biogeography, 2019

This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Biotropica, 2019

We test for evidence of the Tropical Niche Conservatism or the Out of The Tropics hypotheses in s... more We test for evidence of the Tropical Niche Conservatism or the Out of The Tropics hypotheses in structuring patterns of tree community composition along a 2000 + meter elevational gradient in the northern tropical Andes. By collecting and integrating data on the presence–absence of tree species within plots with phylogenetic information, we analyzed the following: (a) patterns of phylogenetic dispersion and species diversity along the elevational gradient based on indexes of net relatedness, nearest taxon relatedness, and species richness (α‐diversity); and (b) the replacement of lineages along the gradient using the PhyloSorensen metric (β‐diversity). More specifically, we established 20 0.25‐ha permanent tree inventory plots between 750 and 2,802 m asl where all individuals with diameter at breast height (DBH) ≥ 10 cm were measured and identified. We then used a series of linear models to test for changes in α and β diversity between plots in relation to elevation. Neither the net...

Environmental Science & Policy, 2017

After more than 50-years of armed conflict, Colombia is now transitioning to a more stable social... more After more than 50-years of armed conflict, Colombia is now transitioning to a more stable social and political climate due to a series of peace agreements between the government and different armed groups. Consequences of these socioeconomic and political changes on ecosystems are largely uncertain, but there is growing concern about derived increases in environmental degradation. Here, we review the capacity of Colombia to monitor the state of its ecosystems and their rate of change over time. We found several important programs currently set in place by different institutions as well as by independent groups of scientists that address different aspects of environmental monitoring. However, most of the current initiatives could be improved in terms of data coverage, quality and access, and could be better articulated among each other. We propose a set of activities that would increase the capacity of Colombia to monitor its ecosystems, provide useful information to policy makers, and facilitate scientific research. These include: 1) the establishment of a national center for ecological synthesis that focuses on analyzing existing information; 2) the establishment of an ecological observatory system that collects new information, integrates remote sensing products, and produces near real-time products on key ecological variables; and 3) the creation of new platforms for dialog and action within existing scientific and policy groups.

Science (New York, N.Y.), Mar 3, 2017

The extent to which pre-Columbian societies altered Amazonian landscapes is hotly debated. We per... more The extent to which pre-Columbian societies altered Amazonian landscapes is hotly debated. We performed a basin-wide analysis of pre-Columbian impacts on Amazonian forests by overlaying known archaeological sites in Amazonia with the distributions and abundances of 85 woody species domesticated by pre-Columbian peoples. Domesticated species are five times more likely than nondomesticated species to be hyperdominant. Across the basin, the relative abundance and richness of domesticated species increase in forests on and around archaeological sites. In southwestern and eastern Amazonia, distance to archaeological sites strongly influences the relative abundance and richness of domesticated species. Our analyses indicate that modern tree communities in Amazonia are structured to an important extent by a long history of plant domestication by Amazonian peoples.

Biogeosciences Discussions, 2014

Biodiversidad 2015. Estado y tendencias de la biodiversidad continental de Colombia, 2016

Tropical mountain forests provide an exceptional opportunity to evaluate the patterns of variatio... more Tropical mountain forests provide an exceptional opportunity to evaluate the patterns of variation of carbon stocks along elevational gradients that correspond to well-defined temperature gradients. We predicted that carbon stored in live aboveground biomass, aboveground necromass, and soil components of forests on the eastern flank of the Colombian Andes would change with elevation along this gradient extending from 750 to 2800 m above sea level. The rationale was that the corresponding change in temperature (14°C to 26°C) would influence tree growth and decomposition of organic matter. To address this hypothesis, we examined the carbon stored in these three components using data from 20 0.25-ha plots located along this elevational gradient. The mean total carbon stock found in the study region was 241.3±37.5 Mg C/ha. Aboveground carbon stocks decreased with elevation (p =0.001), as did necromass carbon stocks (p =0.016). Although soil organic carbon stocks did not differ significantly along the gradient (p =0.153), they contributed proportionately more at higher than at lower elevations, counterbalancing the opposite trends in aboveground carbon and necromass carbon stocks. As such, total carbon stocks did not vary significantly along the elevational gradient (p =0.576)

Forest Ecology and Management, 2016

Abstract Emission factors are essential in order to accurately account and report land use and la... more Abstract Emission factors are essential in order to accurately account and report land use and land use change emissions due to deforestation at a national level, in accordance with the United Nations Framework Convention on Climate Change reporting guidelines. Nonetheless, in many tropical countries its availability is still scarce, especially in Colombia where a National Forest Inventory is lacking. Here, we estimate the amount of carbon stored in the live aboveground biomass of the forests of Colombia, using data from 4981 sampling forest plots of various sizes established between 1990 and 2014. Our study included an analysis of the influence of the choice of allometric model and the carbon density estimation method employed in the estimation. We found that the most conservative total mean value for the entire country was 226.9 ± 4.5 Mg ha−1, obtained by using a previous set of allometric equations developed for the natural forest of Colombia and an inverse-variance weighting that accounts for the variation in plot size, which represents a potential stock of 6.44 ± 0.13 Pg of carbon. Thus, our study provides a method to utilize existing sample data to assess forest carbon stocks at national level, make available conservative carbon stocks estimates for the natural forests of Colombia, and reports enhanced and adequate information subject to national capabilities and policies in the context of results-based payments for reducing emissions from deforestation and forest degradation and the conservation.

Frontiers of Biogeography, 2016