J. Antonio Guzmán Q.Harvard University | Harvard · Department of Organismic and Evolutionary Biology
J. Antonio Guzmán Q.
Doctor of Philosophy
About
49
Publications
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Introduction
My interests are associated with plant physiology and remote sensing; and their application to understanding the dynamics of ecosystems, the environmental management, and the improvement in production.
Additional affiliations
September 2016 - February 2021
January 2010 - August 2015
Publications
Publications (49)
Protecting the future of forests relies on our ability to observe changes in forest health. Thus, developing tools for sensing diseases in a timely fashion is critical for managing threats at broad scales. Oak wilt - a disease caused by a pathogenic fungus (Bretziella fagacearum) - is threatening oaks, killing thousands yearly while negatively impa...
1 Fractals have been widely used to determine bifurcation patterns in trees or to analyze the homeostasis of the development of plants to different environments. In a few instances, fractals have been used to predict tree or stand metrics. Here we explore the use of fractal geometry based on the voxel‐counting method (VC) to predict tree and stands...
Increases in liana abundance in tropical forests are pervasive threats to the current and future forest carbon stocks. Never before has the need been more evident for new approaches to detect the presence of liana in ecosystems, given their significance as fingerprints of global environmental change. In this study, we explore the use of longwave in...
Predicting leaf traits using models based on spectroscopic data can provide essential information to advance ecological research and future Earth system models. Most current models are based on Partial Least Squares Regression (PLSR) algorithms that attempt to predict a set of leaf traits of several plant groups using leaf spectra. However, PLSR mo...
Clouds are critical to the biodiversity and function of Tropical Montane Cloud Forests (TMCF) as they control water regimes and sunlight that can be perceived by plants. These ecosystems provide a key role in ecosystem services to humanity and are considered hotspots of endemism, given that the number of species is restricted to their microclimates...
We introduce a new “ecosystem‐scale” experiment at the Cedar Creek Ecosystem Science Reserve in central Minnesota, USA to test long‐term ecosystem consequences of tree diversity and composition. The experiment—the largest of its kind in North America—was designed to provide guidance on forest restoration efforts that will advance carbon sequestrati...
We introduce a new “low-density” tree diversity experiment at the Cedar Creek Ecosystem Science Reserve in central Minnesota, USA aimed at testing long-term ecosystem consequences of tree diversity and composition. The experiment was designed to provide guidance on forest restoration efforts that will simultaneously advance carbon sequestration goa...
The stability of forest productivity over time is a widely studied parameter often associated with benefits of forest diversity. Yet, the structural stability ( SS ) through the season of forest communities and its relationship to diversity, composition, and productivity remains poorly understood. Using a large-scale (10 ha) young tree diversity ex...
Tree mortality due to global change—including range expansion of invasive pests and pathogens— is a paramount threat to forest ecosystems. Oak forests are among the most prevalent and valuable ecosystems both ecologically and economically in the United States. There is increasing interest in monitoring oak decline and death due to both drought and...
The stability of forest productivity over time is a widely studied parameter often associated with benefits of forest diversity. Yet, the structural stability (SS) through the season of forest communities and its relationship to diversity, composition, and productivity remains poorly understood. Using a large-scale young tree diversity experiment,...
Clouds are critical to the biodiversity and function of Tropical Montane Cloud Forests (TMCF). These ecosystems provide vital services to humanity and are considered hotspots of endemism, given that the number of species is restricted to their microclimates. Cloudiness (e.g., the fraction of low-clouds) in these ecosystems is projected to decline o...
Protecting the future of forests relies on our ability to observe changes in forest health. Thus, developing tools for sensing diseases in a timely fashion is critical for managing threats at broad scales. Oak wilt -a disease caused by a pathogenic fungus (Bretziella fagacearum)- is threatening oaks, killing thousands yearly while negatively impact...
Spectroscopy imagery from spaceborne sensors has long been recognized as a key tool for the future mapping of tree species and forest communities. However, the feasibility of mapping forest communities at large spatial extents from spaceborne data is not yet clear. Unlike species mapping using airborne spectroscopy, spaceborne spectroscopy faces ec...
Detection of oak wilt using Sentinel-2
Lianas are a key growth form in tropical forests. Their lack of self-supporting tissues and their vertical position on top of the canopy make them strong competitors of resources. A few pioneer studies have shown that liana optical traits differ on average from those of colocated trees. Those trait discrepancies were hypothesized to be responsible...
Lianas, woody vines acting as structural parasites of trees, have profound effects on the composition and structure of tropical forests, impacting tree growth, mortality, and forest succession. Remote sensing offers a powerful tool for quantifying the scale of liana infestation, provided the availability of robust detection methods. We analyze the...
The leaf economic spectrum describes a comprehensive framework of how the surrounding environment modulates leaf functional traits (LFT) and how these are associated between them. This framework has traditionally focused on physiological, chemical, and biomass assignation traits, but rarely in leaf anatomical traits. Here we compare leaf anatomical...
Lianas are woody thick-stemmed climbers that use host trees to reach the forest canopy. Studies have shown a remarkable increase in liana abundance in the last two decades, while others have shown that liana abundance is associated with detrimental effects on forest dynamics. Liana abundance presents peaks in highly seasonal forests such as the Tro...
Lianas are a key growth form in tropical forests. Their lack of self-supporting tissues and their vertical position on top of the canopy make them strong competitors of resources. A few pioneer studies have shown that liana optical traits differ on average from those of colocated tree. Those trait discrepancies were hypothesized to be responsible f...
Tropical dry forests (TDFs) worldwide have an environment-sensitive phenological signal, which easily marks their response to the changing climatic conditions, especially precipitation and temperature. Using TDF phenological characteristics as a proxy, this study aims to evaluate their current continental response to climate change across the Ameri...
Living walls are important vertical greening systems with modular prevegetated structures. Studies have suggested that living walls have many social benefits as an ecological engineering technique with notable potential for reconciliation ecology. Despite these benefits, there are currently no mature workflows or technologies for monitoring the hea...
The optical properties of lichens have been traditionally explored in the context of geological mapping where the encrustation of lichens on rocks may influence the detection of minerals of interest. As of today, few studies have looked into the potential of using the optical properties of lichens to classify them; however, none has investigated th...
The Normalized Difference Vegetation Index (NDVI) is widely used to monitor vegetation phenology and productivity around the world. Over the last few decades, phenology monitoring at large scales has been possible due to the information and metrics derived from satellite sensors such as the Moderate Resolution Imaging Spectroradiometer (MODIS) or t...
The fractal dimension is a spatial metric that describes the geometry and complexity of natural objects such as rivers or trees. Specifically, this metric has been widely used to describe the architecture and the biomass allocation of trees. However, few studies have been conducted to describe the fractal dimension of the trees using Terrestrial La...
Leaf temperature (Tleaf) influences photosynthesis and respiration. Currently, there is a growing interest in including lianas in productivity models due to their increasing abundance and their detrimental effects in the carbon stock of tropical ecosystems. Therefore, understanding the differences of Tleaf between lianas and trees is important for...
Normalized difference vegetation index (NDVI) is a parameter extensibility used in studies of vegetation to describe phenological processes, monitoring the crop health or detect drought anomalies associated with climatic events. Currently, the NDVI can be obtained from several satellite sensors which represent a common tool for vegetation monitorin...
Tropical dry forests (TDFs) present strong seasonal greenness signals ideal for tracking phenology and primary productivity using remote sensing techniques. The tightly synchronized relationship these ecosystems have with water availability offer a valuable natural experiment for observing the complex interactions between the atmosphere and the bio...
The fields of tropical biology and conservation face significant transformations due to rapid technological developments in remote sensing. Other fields (e.g. Archeology) are experiencing this momentous change even more rapidly. In this article, we review some of the challenges that the fields of tropical biology and conservation face during the fi...
Tropical dry forests (TDFs) are ecosystems with long drought periods, a mean temperature of 25 ∘C, a mean annual precipitation that ranges from 900 to 2000 mm, and that possess a high abundance of deciduous species (trees and lianas). What remains of the original extent of TDFs in the Americas remains highly fragmented and at different levels of ec...
The determination of favorable light habitat conditions per species and life stage is transcendental, for both ex situ and in situ conservation strategies of endangered forest tree species, and for their utilization as plantation trees. This becomes especially important when planting material is scarce. We studied the multivariate responses in biom...
• Background and Aims. Plant design refers to the construction of the plant body or its constituent parts in terms of form and function. Although neighbourhood structure is recognized as a factor that limits plant survival and species coexistence, its relative importance on plant design is not well understood. We conducted field research to analyse...
Although plant competition is recognized as a fundamental factor that limits survival and species coexistence, its relative importance on light capture efficiency and carbon gain is not well understood. Here, we propose a new framework to explain the effects of neighborhood structures and light availability on plant attributes and their effect on p...
Changes in land use are mainly a consequence of anthropogenic actions. The current agricultural and urban transformations in Costa Rica have raised questions about the effectiveness of conservation and restoration within protected areas. Herein we analyzed the patterns of land use change between three periods: 1997, 2005 and 2010 in terms of magnit...
Aunque la competencia asimétrica entre plantas es reconocida como un factor fundamental para la sobrevivencia y la coexistencia de las especies, su importancia sobre la eficiencia de la captura de luz y la ganancia de carbón no está bien comprendida. Aquí, yo pongo un nuevo marco de trabajo donde explico el efecto de la competencia asimétrica sobre...
Leaf heteroblasty is a plant phenomenon related to leaf development that describes substantial differences between temporally separated plant stages. This study explores the ecological advantage of leaf heteroblasty in the herb Costus pulverulentus C.Presl and analyzes its possible adaptive value. Heteroblasty was studied using leaf morphology anal...
Los estudios de las implicaciones de la heterostilia floral en las especies se encuentran ligados a poblaciones puntuales, sin tomar en cuenta las variaciones de los rasgos heterostílicos en poblaciones que se encuentran en ambientes con contrastante estado de regeneración natural. El objetivo de este estudio fue determinar si existen diferencias e...
Environmental heterogeneity mostly dominated by differing light regimes affects the expression of phenotypic plasticity, which is important for plant growth and survival, especially in the forest understory. The knowledge about these responses to this heterogeneity is a key factor for forest restoration initiatives. In this study, we determine seve...
Los cambios en el uso del suelo en términos de magnitud, direccionalidad y velocidad, corresponden principalmente a alteraciones antropogénicas sobre los terrenos. Dentro esta investigación se analizan los distintos patrones de cambio del uso del suelo entre 1997, 2005 y 2010 por medio de elaboración de mapas categóricos a raíz de la fotointerpreta...
Heretophylly is the production of leaves of different size or shape along the longitudinal axis, whose variation may be under genetic control or the phenotypic plasticity in response to environmental conditions. I used different methodological approaches to study the function of heterophylly along the main axis of Costus pulverulestus and its possi...
Genetic diversity loss due to forest fragmentation and selective logging has caused the disappearing of several populations of native trees. Knowledge about their growth and environmental conditions for the recovery of threatened species is needed to ensure adequate conservation and reforestation practices. We studied how light responses and biomas...
La heterogeneidad lumínica ambiental incide en el desarrollo y crecimiento de las plantas, las cuales responden de múltiples maneras, permitiéndoles establecerse en la diversidad de microambientes de los ecosistemas naturales. Actualmente, el conocimiento sobre las preferencias microambientales y la capacidad de respuesta de las miles de especies c...
El alto grado de dinamismo de los bosques tropicales provoca que los microambientes lumínicos cambien continuamente durante los periodos del establecimiento de las plantas. Esta heterogeneidad ambiental incide en la plasticidad fenotípica que puede desarrollar una planta, y se convierte en un factor determinante de su sobrevivencia, especialmente e...
Questions
Questions (5)
Dear all,
I am trying to fit sigmoidal curves to describe the relative growth rate (RGR) according to the plant competition (PC). I am implementing three types of models to describe the RGR: i) a competition-dependent model (IND), ii) a competition-dependent model with species-specific parameters (SP), and iii) competition-dependent model based on the life form (LF). The first one can be considered as the null model, because the all individuals can have the same growth rate, regardless of species. The second model the growth model parameters are species-specific, meaning that each species has its own growth trajectory. And the third model the growth model parameters are life form -specific, meaning that each functional group has its own growth trajectory. I am using non-linear fixed and mixed effect regression with nls and nlme in R to describe these model, but I have problems with the syntax of the models in R and the way of how to choose the best model.
For example,
I have the three parameter sigmoid curve describe by this function sigmoid()
- sigmoid <- function(x, a, b, c){
- a/(1+exp(-(x-c)/b))
- }
in where x is PC, a is the asymptote of the RGR (the maximum RGR), b is the curve shape, and c is the inflection point.
From this initial parameters a=0.3, b=240, c=9, I can extract the three models
Model i by nls)
model.ind <- nls(RGR ~ sigmoid(PC, a, b, c), data = data, start = c(a=0.3, b=240, c=9))
Model ii by nlme)
model.sp <- nls(RGR ~ sigmoid(PC, a, b, c), data = data, fixed = a + b + c ~ 1, random = a +b +c ~ 1|SP, start = c(a=0.3, b=240, c=9))
Model iii by nlme)
model.lf <- nls(RGR ~ sigmoid(PC, a, b, c), data = data, fixed = a + b + c ~ 1, random = a +b +c ~ 1|LF, start = c(a=0.3, b=240, c=9))
The question that I have is: Are the models syntax correct? Is correct use “a +b +c ~ 1|SP” or “a +b +c ~ 1|LF” as random values into the models to describe the goal ii and iii?
What variable allows me to choose the best model between these? AIC, BCI, Log-Likelihood, or RMSR? Why?
How I can perform the model in nlme without random effects?
Thank you very much for your help and time
Hello everyone,
I recently had a conflict of ideas to use the best concepts for describe the local process of changes in plant traits within a study. In this study I measured different plants traits in a natural environment within two forest types at a time “X”. When I compare the plant traits by type of forest at this time "X", I find that there is a variation according to the type of forest. However what is the best concept (word) to describe this variation: phenotypic plasticity, acclimation, acclimatization or adaptation?
Many of these concepts can be linked into this process of local variation, but what is the best concepts to describe this variation?, why?
To work in groups or individually in R, what is a suitable repository: GitHub, bitbucket or gitorious? and why?
Game theory can explain the interaction and the possible scenarios of many games. Recently this theory is introduced to explain the interactions in ecological processes. There is a book that focuses on game theory and plant ecology?
I need to calculate the importance value index of some trees in a plot, does anyone know about any function or package in R?
