Enrico Yepez | Instituto Tecnológico de Sonora (original) (raw)

Papers by Enrico Yepez

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data... more This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site MX-Tes Tesopaco, secondary tropical dry forest. This is the FLUXNET version of the carbon flux data for the site MX-Tes Tesopaco, secondary tropical dry forest produced by applying the standard ONEFlux (1F) software. Site Description - This tower was located in the "Ejido la Estrella" where the eddy covariance tower is located 7.5 km east of the town Rosario de Tesopaco, in southeastern Sonora, Mexico. The tower was positioned in the center of a homogeneous flat terrain at the foothills of the Madre Occidental. This ecosystem lies in a highly seasonal region under the influence of the North American Monsoon that brings about 70% of the rains from July to September. The site is dominated by leguminous trees. Some of the dominant species are Lysiloma divaricatum, Ipomoea arborescens, Acacia cochliacantha, Haematoxylum brasiletto, and Celtis reticulata. The mean basa...

Journal of Geophysical Research: Biogeosciences, 2015

Due to their large extent and high primary productivity, tropical dry forests (TDF) are important... more Due to their large extent and high primary productivity, tropical dry forests (TDF) are important contributors to atmospheric carbon exchanges in subtropical and tropical regions. In northwest Mexico, a bimodal precipitation regime that includes winter precipitation derived from Pacific storms and summer precipitation from the North American monsoon (NAM) couples water availability with ecosystem processes. We investigated the net ecosystem production of a TDF ecosystem using a 4.5 year record of water and carbon fluxes obtained from the eddy covariance method complemented with remotely sensed data. We identified a large CO 2 efflux at the start of the summer season that is strongly related to the preceding winter precipitation and greenness. Since this CO 2 efflux occurs prior to vegetation green-up, we infer that respiration is mainly due to decomposition of soil organic matter accumulated from the prior growing season. Overall, ecosystem respiration has an important effect on the net ecosystem production but can be overwhelmed by the strength of the primary productivity during the NAM. Precipitation characteristics during NAM have significant controls on sustaining carbon fixation in the TDF into the fall season. We identified that a threshold of~350 to 400 mm of monsoon precipitation leads to a switch in the annual carbon balance in the TDF ecosystem from a net source (+102 g C/m 2 /yr) to a net sink (À249 g C/m 2 /yr). This monsoonal precipitation threshold is typically exceeded one out of every 2 years. The close coupling of winter and summer periods with respect to carbon fluxes suggests that the annual carbon balance is dependent on precipitation amounts in both seasons in TDF ecosystems.

Background/Question/Methods Bark beetles found in piñons in New Mexico form symbiotic relationshi... more Background/Question/Methods Bark beetles found in piñons in New Mexico form symbiotic relationships with Ophiostomatoid fungi. Recent findings indicate that bark beetles and their fungal symbionts are also associated with bacteria that may act as neutralizing agents against antagonistic fungi and thereby facilitate bark-beetle-fungal pathogenesis. Our goal was to identify some of the common bacteria associated with Ophiostomatoid fungi and bark beetles. Ophiostoma cultures were isolated from bark beetles, tree cores, and fruiting bodies from infected piñons on experimental drought plots at the Sevilleta Long Term Ecological Research site in New Mexico. Bacteria were isolated from Ophiostomatoid isolates and DNA was extracted, amplified, and sequenced using 16S rDNA primers. Results/Conclusions Ophiostomatoid fungi were highly colonized by a large number of bacteria. Among common bacterial isolates were close relatives of Erwinia, a plant pathogen within the family Enterobacteriaceae...

Ecology and Evolution, 2015

Plant hydraulic conductance (k s) is a critical control on whole-plant water use and carbon uptak... more Plant hydraulic conductance (k s) is a critical control on whole-plant water use and carbon uptake and, during drought, influences whether plants survive or die. To assess long-term physiological and hydraulic responses of mature trees to water availability, we manipulated ecosystem-scale water availability from 2007 to 2013 in a piñon pine (Pinus edulis) and juniper (Juniperus monosperma) woodland. We examined the relationship between k s and subsequent mortality using more than 5 years of physiological observations, and the subsequent impact of reduced hydraulic function and mortality on total woody canopy transpiration (E C) and conductance (G C). For both species, we observed significant reductions in plant transpiration (E) and k s under experimentally imposed drought. Conversely, supplemental water additions increased E and k s in both species. Interestingly, both species exhibited similar declines in k s under the imposed drought conditions, despite their differing stomatal responses and mortality patterns during drought. Reduced whole-plant k s also reduced carbon assimilation in both species, as leaf-level stomatal conductance (g s) and net photosynthesis (A n) declined strongly with decreasing k s. Finally, we observed that chronically low whole-plant k s was associated with greater canopy dieback and mortality for both piñon and juniper and that subsequent reductions in woody canopy biomass due to mortality had a significant impact on both daily and annual canopy E C and G C. Our data indicate that significant reductions in k s precede drought-related tree mortality events in this system, and the consequence is a significant reduction in canopy gas exchange and carbon fixation. Our results suggest that reductions in productivity and woody plant cover in piñon-juniper woodlands can be expected due to reduced plant hydraulic conductance and increased mortality of both piñon pine and juniper under anticipated future conditions of more frequent and persistent regional drought in the southwestern United States.

Proyecto académico sin fines de lucro, desarrollado bajo la iniciativa de acceso abierto

Atmósfera, 2013

Para entender los procesos de los ecosistemas desde un punto de vista funcional es fundamental en... more Para entender los procesos de los ecosistemas desde un punto de vista funcional es fundamental entender las relaciones entre la variabilidad climática, los ciclos biogeoquímicos y las interacciones superficie-atmósfera. En las últimas décadas se ha aplicado de manera creciente el método de covarianza de flujos turbulentos (EC, por sus siglas en inglés) en ecosistemas terrestres, marinos y urbanos para medir los flujos de gases de invernadero (p. ej., CO 2 , H 2 O) y energía (p. ej., calor sensible y latente). En diversas regiones se han establecido redes de sistemas EC que han aportado información científica para el diseño de políticas ambientales y de adaptación. En este contexto, el presente trabajo delimita el marco conceptual y técnico para el establecimiento de una red regional de medición de flujos de gases de efecto invernadero en México, denominada MexFlux, cuyo objetivo principal es mejorar nuestra comprensión de la forma en que la variabilidad climática y la transformación ambiental influye en la dinámica de los ecosistemas mexicanos ante los factores de cambio ambiental global. En este documento se analiza primero la importancia del intercambio de CO 2 y vapor de agua entre los ecosistemas terrestres y la atmósfera. Después se describe brevemente la técnica de covarianza de flujos turbulentos para la medición de éstos, y se presentan ejemplos de mediciones en dos ecosistemas terrestres y uno urbano en México. Por último, se describen las bases conceptuales y operativas a corto, mediano y largo plazo para la continuidad de la red MexFlux.

Water Resources Research, 2014

Seasonal vegetation changes during the North American monsoon play a major role in modifying wate... more Seasonal vegetation changes during the North American monsoon play a major role in modifying water, energy, and momentum fluxes. Nevertheless, most models parameterize plants as a static component or with averaged seasonal variations that ignore interannual differences and their potential impact on evapotranspiration (ET) and its components. Here vegetation parameters derived from remote sensing data were coupled with a hydrologic model at two eddy covariance (EC) sites with observations spanning multiple summers. Sinaloan thornscrub (ST) and Madrean woodland (MW) sites, arranged at intermediate and high elevations along mountain fronts in northwest Mexico, occupy specific niches related to climate conditions and water availability that are poorly understood. We found that simulations with a dynamic representation of vegetation greening tracked well the seasonal evolution of observed ET and soil moisture (SM). A switch in the dominant component of ET from soil evaporation (E) to plant transpiration (T) was observed for each ecosystem depending on the timing and magnitude of vegetation greening that is directly tied to rainfall characteristics. Differences in vegetation greening at the ST and MW sites lead to a dominance of transpiration at ST (T/ET 5 57%), but evaporation-dominant conditions at MW (T/ET 5 19%). Peak transpiration occurred at 5 and 20 days after the full canopy development in the ST and MW sites, respectively. These results indicate that evapotranspiration timing and partitioning varies considerably in the two studied ecosystems in accordance with different modes of vegetation greening. Intermediateelevation ecosystems follow an intensive water use strategy with a rapid and robust transpiration response to water availability. In contrast, higher elevation sites have delayed and attenuated transpiration, suggesting an extensive water use strategy persisting beyond the North American monsoon.

CHAPTER 1. INTRODUCTION…………………………………………………….. 14 CHAPTER 2. PRECIPITATION PULSES AND ECOSYSTEM CA... more CHAPTER 1. INTRODUCTION…………………………………………………….. 14 CHAPTER 2. PRECIPITATION PULSES AND ECOSYSTEM CARBON AND WATER EXCHANGE IN ARID AND SEMIARID ENVIRONMENTS ………… 17 INTRODUCTION……………………………………………………………………… 17 Vegetation effects on ecosystem carbon and water interaction. ………………. 19 Short-term ecosystem response to pulsed precipitation.……………………….. 22 Evapotranspiration partitioning ………………………………………………. 28 BOX 1…………………………………………………………………………..……… 31 CHAPTER 3. DYNAMICS OF TRANSPIRATION AND EVAPORATION FOLLOWING A MOISTURE PULSE IN SEMIARID GRASSLAND: A CHAMBER-BASED ISOTOPE METHOD FOR PARTITIONING FLUX COMPONENTS.………………………………………………………………………. 41 ABSTRACT ……………………………………………………………………………. INTRODUCTION ……………………………………………………………………... 43 MATERIALS AND METHODS ………………………………………………………. Experimental grassland plots and irrigation …………………………………... Evapotranspiration measurements …………………………………………….. 46 Evapotranspiration flux partitioning …………………………………………... 47 Vapor collection for Keeling plot analysis …………………………….. 47 Isotopic composition of transpiration ………………………………….. Isotopic composition of the soil evaporation flux ……………………… Isotope analysis…………………………………………………………………. Grass water relations and leaf-to-canopy scaling ……………………………... 6 TABLE OF CONTENTS-Continued RESULTS ……………………………………………………………………… 55 Soil water budget and evapotranspiration ……….…………………….. 55 Plant responses to the irrigation pulse ………………………………… 56 Isotopic composition of sources contributing to ET …………………… 57 Partitioning of ET based on Keeling plots of water vapor …………….. 58 Method validation ……………………………………………………… 60 DISCUSSION …………………………………….……………………………. 61 Method assumptions …………………………………………………… 63 CONCLUSION ………………………………………………………………… 67 CHAPTER 4. INTRASEASONAL VARIATION IN WATER AND CARBON DIOXIDE FLUX COMPONENTS IN A SEMIARID RIPARIAN WOODLAND …………………………………………………………………………………………... 82 ABSTRACT ……………………………………………………………………………. 82 INTRODUCTION ……………………………………………………………………... 84 MATERIALS AND METHODS……………………………………………………….. 88 Site description………………………………………………………………….. 88 Cover of understory plants……………………………………………………… 89 Flux and micrometeorological measurements …………………………………. 89 ET partitioning ……….…………………………..…………………………….. 90 RESULTS ……………………………………………………………………………… 97 Environmental conditions during field campaigns …………………………….. 97 ET partitioning …………………………………………………………………. 98 Seasonal trend of ET and NEE components ………………………………….. 101 DISCUSSION ………………………………………………………………………….103 Factors controlling the coupling of GEP and R eco during wet and dry periods …………………………………………………………………………………..103 Relationship between ET components and carbon dioxide exchange………….107 7 TABLE OF CONTENTS-Continued CHAPTER 5. EVAPOTRANSPIRATION AND CARBON DIOXIDE EXCHANGE IN THE UNDERSTORY OF FLOODPLAIN WOODLAND FOLLOWING EXPERIMENTAL WATER ADDITIONS ………………………………………...

Contrasting foliar responses to experimental drought and rainfall addition in co-occurring piñon ... more Contrasting foliar responses to experimental drought and rainfall addition in co-occurring piñon and juniper trees. Jean-Marc Limousin 1 , Christopher P. Bickford 1 , Jessica L. Osuna 1 , Robert E. Pangle 1 , Enrico A. Yepez ...

Extended drought and ensuing tree mortality has been observed in Southwest piñon pine (Pinus edul... more Extended drought and ensuing tree mortality has been observed in Southwest piñon pine (Pinus edulis) and juniper (Juniperus monosperma) woodlands (PJ woodland) in recent years. In an effort to assess the response of these two species to extended drought, a ...

Drought induced tree mortality has become conspicuous in mid-latitude regions of the Earth. But, ... more Drought induced tree mortality has become conspicuous in mid-latitude regions of the Earth. But, the causes and consequences of this phenomenon remain largely unknown. Several interrelated factors have been proposed to explain tree mortality following drought eg failure to water ...

This is the AmeriFlux version of the carbon flux data for the site MX-Tes Tesopaco, secondary tro... more This is the AmeriFlux version of the carbon flux data for the site MX-Tes Tesopaco, secondary tropical dry forest.

Los matorrales y pastizales xerofilos presentan de relativamente bajo a moderado contenido de car... more Los matorrales y pastizales xerofilos presentan de relativamente bajo a moderado contenido de carbono en la biomasa y el suelo, pero pueden tener un efecto significativo para contrarrestar el cambio climatico al absorber las emisiones de CO2 de la atmosfera, ya que ocupan mas de un tercio de la superficie terrestre global y mas de la mitad de Mexico. Con el objetivo de evaluar la contribucion de los matorrales y pastizales xerofilos al secuestro y emision de carbono, se compilo una base de datos con 68 estudios con informacion sobre los almacenes y flujos de carbono en publicaciones indizadas, no indizadas, tesis, capitulos de libro e informes tecnicos. Los estudios se organizaron en los temas: biomasa, productividad primaria, produccion de hojarasca, respiracion del suelo y descomposicion. Todos los estudios localizados se realizaron entre 1980 y 2018 y mas del 80% se produjo en el presente siglo. Mas de 70% de los estudios fueron articulos revisados por pares y realizados en las U...

Soil moisture is an essential measurement to manage water and improve crop production. However, a... more Soil moisture is an essential measurement to manage water and improve crop production. However, agricultural research in the Yaqui Valley (in northwestern Mexico) with extensive wheat fields (Triti...

This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data... more This is the AmeriFlux Management Project (AMP) created FLUXNET-1F version of the carbon flux data for the site MX-Tes Tesopaco, secondary tropical dry forest. This is the FLUXNET version of the carbon flux data for the site MX-Tes Tesopaco, secondary tropical dry forest produced by applying the standard ONEFlux (1F) software. Site Description - This tower was located in the "Ejido la Estrella" where the eddy covariance tower is located 7.5 km east of the town Rosario de Tesopaco, in southeastern Sonora, Mexico. The tower was positioned in the center of a homogeneous flat terrain at the foothills of the Madre Occidental. This ecosystem lies in a highly seasonal region under the influence of the North American Monsoon that brings about 70% of the rains from July to September. The site is dominated by leguminous trees. Some of the dominant species are Lysiloma divaricatum, Ipomoea arborescens, Acacia cochliacantha, Haematoxylum brasiletto, and Celtis reticulata. The mean basa...

Journal of Geophysical Research: Biogeosciences, 2015

Due to their large extent and high primary productivity, tropical dry forests (TDF) are important... more Due to their large extent and high primary productivity, tropical dry forests (TDF) are important contributors to atmospheric carbon exchanges in subtropical and tropical regions. In northwest Mexico, a bimodal precipitation regime that includes winter precipitation derived from Pacific storms and summer precipitation from the North American monsoon (NAM) couples water availability with ecosystem processes. We investigated the net ecosystem production of a TDF ecosystem using a 4.5 year record of water and carbon fluxes obtained from the eddy covariance method complemented with remotely sensed data. We identified a large CO 2 efflux at the start of the summer season that is strongly related to the preceding winter precipitation and greenness. Since this CO 2 efflux occurs prior to vegetation green-up, we infer that respiration is mainly due to decomposition of soil organic matter accumulated from the prior growing season. Overall, ecosystem respiration has an important effect on the net ecosystem production but can be overwhelmed by the strength of the primary productivity during the NAM. Precipitation characteristics during NAM have significant controls on sustaining carbon fixation in the TDF into the fall season. We identified that a threshold of~350 to 400 mm of monsoon precipitation leads to a switch in the annual carbon balance in the TDF ecosystem from a net source (+102 g C/m 2 /yr) to a net sink (À249 g C/m 2 /yr). This monsoonal precipitation threshold is typically exceeded one out of every 2 years. The close coupling of winter and summer periods with respect to carbon fluxes suggests that the annual carbon balance is dependent on precipitation amounts in both seasons in TDF ecosystems.

Background/Question/Methods Bark beetles found in piñons in New Mexico form symbiotic relationshi... more Background/Question/Methods Bark beetles found in piñons in New Mexico form symbiotic relationships with Ophiostomatoid fungi. Recent findings indicate that bark beetles and their fungal symbionts are also associated with bacteria that may act as neutralizing agents against antagonistic fungi and thereby facilitate bark-beetle-fungal pathogenesis. Our goal was to identify some of the common bacteria associated with Ophiostomatoid fungi and bark beetles. Ophiostoma cultures were isolated from bark beetles, tree cores, and fruiting bodies from infected piñons on experimental drought plots at the Sevilleta Long Term Ecological Research site in New Mexico. Bacteria were isolated from Ophiostomatoid isolates and DNA was extracted, amplified, and sequenced using 16S rDNA primers. Results/Conclusions Ophiostomatoid fungi were highly colonized by a large number of bacteria. Among common bacterial isolates were close relatives of Erwinia, a plant pathogen within the family Enterobacteriaceae...

Ecology and Evolution, 2015

Plant hydraulic conductance (k s) is a critical control on whole-plant water use and carbon uptak... more Plant hydraulic conductance (k s) is a critical control on whole-plant water use and carbon uptake and, during drought, influences whether plants survive or die. To assess long-term physiological and hydraulic responses of mature trees to water availability, we manipulated ecosystem-scale water availability from 2007 to 2013 in a piñon pine (Pinus edulis) and juniper (Juniperus monosperma) woodland. We examined the relationship between k s and subsequent mortality using more than 5 years of physiological observations, and the subsequent impact of reduced hydraulic function and mortality on total woody canopy transpiration (E C) and conductance (G C). For both species, we observed significant reductions in plant transpiration (E) and k s under experimentally imposed drought. Conversely, supplemental water additions increased E and k s in both species. Interestingly, both species exhibited similar declines in k s under the imposed drought conditions, despite their differing stomatal responses and mortality patterns during drought. Reduced whole-plant k s also reduced carbon assimilation in both species, as leaf-level stomatal conductance (g s) and net photosynthesis (A n) declined strongly with decreasing k s. Finally, we observed that chronically low whole-plant k s was associated with greater canopy dieback and mortality for both piñon and juniper and that subsequent reductions in woody canopy biomass due to mortality had a significant impact on both daily and annual canopy E C and G C. Our data indicate that significant reductions in k s precede drought-related tree mortality events in this system, and the consequence is a significant reduction in canopy gas exchange and carbon fixation. Our results suggest that reductions in productivity and woody plant cover in piñon-juniper woodlands can be expected due to reduced plant hydraulic conductance and increased mortality of both piñon pine and juniper under anticipated future conditions of more frequent and persistent regional drought in the southwestern United States.

Proyecto académico sin fines de lucro, desarrollado bajo la iniciativa de acceso abierto

Atmósfera, 2013

Para entender los procesos de los ecosistemas desde un punto de vista funcional es fundamental en... more Para entender los procesos de los ecosistemas desde un punto de vista funcional es fundamental entender las relaciones entre la variabilidad climática, los ciclos biogeoquímicos y las interacciones superficie-atmósfera. En las últimas décadas se ha aplicado de manera creciente el método de covarianza de flujos turbulentos (EC, por sus siglas en inglés) en ecosistemas terrestres, marinos y urbanos para medir los flujos de gases de invernadero (p. ej., CO 2 , H 2 O) y energía (p. ej., calor sensible y latente). En diversas regiones se han establecido redes de sistemas EC que han aportado información científica para el diseño de políticas ambientales y de adaptación. En este contexto, el presente trabajo delimita el marco conceptual y técnico para el establecimiento de una red regional de medición de flujos de gases de efecto invernadero en México, denominada MexFlux, cuyo objetivo principal es mejorar nuestra comprensión de la forma en que la variabilidad climática y la transformación ambiental influye en la dinámica de los ecosistemas mexicanos ante los factores de cambio ambiental global. En este documento se analiza primero la importancia del intercambio de CO 2 y vapor de agua entre los ecosistemas terrestres y la atmósfera. Después se describe brevemente la técnica de covarianza de flujos turbulentos para la medición de éstos, y se presentan ejemplos de mediciones en dos ecosistemas terrestres y uno urbano en México. Por último, se describen las bases conceptuales y operativas a corto, mediano y largo plazo para la continuidad de la red MexFlux.

Water Resources Research, 2014

Seasonal vegetation changes during the North American monsoon play a major role in modifying wate... more Seasonal vegetation changes during the North American monsoon play a major role in modifying water, energy, and momentum fluxes. Nevertheless, most models parameterize plants as a static component or with averaged seasonal variations that ignore interannual differences and their potential impact on evapotranspiration (ET) and its components. Here vegetation parameters derived from remote sensing data were coupled with a hydrologic model at two eddy covariance (EC) sites with observations spanning multiple summers. Sinaloan thornscrub (ST) and Madrean woodland (MW) sites, arranged at intermediate and high elevations along mountain fronts in northwest Mexico, occupy specific niches related to climate conditions and water availability that are poorly understood. We found that simulations with a dynamic representation of vegetation greening tracked well the seasonal evolution of observed ET and soil moisture (SM). A switch in the dominant component of ET from soil evaporation (E) to plant transpiration (T) was observed for each ecosystem depending on the timing and magnitude of vegetation greening that is directly tied to rainfall characteristics. Differences in vegetation greening at the ST and MW sites lead to a dominance of transpiration at ST (T/ET 5 57%), but evaporation-dominant conditions at MW (T/ET 5 19%). Peak transpiration occurred at 5 and 20 days after the full canopy development in the ST and MW sites, respectively. These results indicate that evapotranspiration timing and partitioning varies considerably in the two studied ecosystems in accordance with different modes of vegetation greening. Intermediateelevation ecosystems follow an intensive water use strategy with a rapid and robust transpiration response to water availability. In contrast, higher elevation sites have delayed and attenuated transpiration, suggesting an extensive water use strategy persisting beyond the North American monsoon.

CHAPTER 1. INTRODUCTION…………………………………………………….. 14 CHAPTER 2. PRECIPITATION PULSES AND ECOSYSTEM CA... more CHAPTER 1. INTRODUCTION…………………………………………………….. 14 CHAPTER 2. PRECIPITATION PULSES AND ECOSYSTEM CARBON AND WATER EXCHANGE IN ARID AND SEMIARID ENVIRONMENTS ………… 17 INTRODUCTION……………………………………………………………………… 17 Vegetation effects on ecosystem carbon and water interaction. ………………. 19 Short-term ecosystem response to pulsed precipitation.……………………….. 22 Evapotranspiration partitioning ………………………………………………. 28 BOX 1…………………………………………………………………………..……… 31 CHAPTER 3. DYNAMICS OF TRANSPIRATION AND EVAPORATION FOLLOWING A MOISTURE PULSE IN SEMIARID GRASSLAND: A CHAMBER-BASED ISOTOPE METHOD FOR PARTITIONING FLUX COMPONENTS.………………………………………………………………………. 41 ABSTRACT ……………………………………………………………………………. INTRODUCTION ……………………………………………………………………... 43 MATERIALS AND METHODS ………………………………………………………. Experimental grassland plots and irrigation …………………………………... Evapotranspiration measurements …………………………………………….. 46 Evapotranspiration flux partitioning …………………………………………... 47 Vapor collection for Keeling plot analysis …………………………….. 47 Isotopic composition of transpiration ………………………………….. Isotopic composition of the soil evaporation flux ……………………… Isotope analysis…………………………………………………………………. Grass water relations and leaf-to-canopy scaling ……………………………... 6 TABLE OF CONTENTS-Continued RESULTS ……………………………………………………………………… 55 Soil water budget and evapotranspiration ……….…………………….. 55 Plant responses to the irrigation pulse ………………………………… 56 Isotopic composition of sources contributing to ET …………………… 57 Partitioning of ET based on Keeling plots of water vapor …………….. 58 Method validation ……………………………………………………… 60 DISCUSSION …………………………………….……………………………. 61 Method assumptions …………………………………………………… 63 CONCLUSION ………………………………………………………………… 67 CHAPTER 4. INTRASEASONAL VARIATION IN WATER AND CARBON DIOXIDE FLUX COMPONENTS IN A SEMIARID RIPARIAN WOODLAND …………………………………………………………………………………………... 82 ABSTRACT ……………………………………………………………………………. 82 INTRODUCTION ……………………………………………………………………... 84 MATERIALS AND METHODS……………………………………………………….. 88 Site description………………………………………………………………….. 88 Cover of understory plants……………………………………………………… 89 Flux and micrometeorological measurements …………………………………. 89 ET partitioning ……….…………………………..…………………………….. 90 RESULTS ……………………………………………………………………………… 97 Environmental conditions during field campaigns …………………………….. 97 ET partitioning …………………………………………………………………. 98 Seasonal trend of ET and NEE components ………………………………….. 101 DISCUSSION ………………………………………………………………………….103 Factors controlling the coupling of GEP and R eco during wet and dry periods …………………………………………………………………………………..103 Relationship between ET components and carbon dioxide exchange………….107 7 TABLE OF CONTENTS-Continued CHAPTER 5. EVAPOTRANSPIRATION AND CARBON DIOXIDE EXCHANGE IN THE UNDERSTORY OF FLOODPLAIN WOODLAND FOLLOWING EXPERIMENTAL WATER ADDITIONS ………………………………………...

Contrasting foliar responses to experimental drought and rainfall addition in co-occurring piñon ... more Contrasting foliar responses to experimental drought and rainfall addition in co-occurring piñon and juniper trees. Jean-Marc Limousin 1 , Christopher P. Bickford 1 , Jessica L. Osuna 1 , Robert E. Pangle 1 , Enrico A. Yepez ...

Extended drought and ensuing tree mortality has been observed in Southwest piñon pine (Pinus edul... more Extended drought and ensuing tree mortality has been observed in Southwest piñon pine (Pinus edulis) and juniper (Juniperus monosperma) woodlands (PJ woodland) in recent years. In an effort to assess the response of these two species to extended drought, a ...

Drought induced tree mortality has become conspicuous in mid-latitude regions of the Earth. But, ... more Drought induced tree mortality has become conspicuous in mid-latitude regions of the Earth. But, the causes and consequences of this phenomenon remain largely unknown. Several interrelated factors have been proposed to explain tree mortality following drought eg failure to water ...

This is the AmeriFlux version of the carbon flux data for the site MX-Tes Tesopaco, secondary tro... more This is the AmeriFlux version of the carbon flux data for the site MX-Tes Tesopaco, secondary tropical dry forest.

Los matorrales y pastizales xerofilos presentan de relativamente bajo a moderado contenido de car... more Los matorrales y pastizales xerofilos presentan de relativamente bajo a moderado contenido de carbono en la biomasa y el suelo, pero pueden tener un efecto significativo para contrarrestar el cambio climatico al absorber las emisiones de CO2 de la atmosfera, ya que ocupan mas de un tercio de la superficie terrestre global y mas de la mitad de Mexico. Con el objetivo de evaluar la contribucion de los matorrales y pastizales xerofilos al secuestro y emision de carbono, se compilo una base de datos con 68 estudios con informacion sobre los almacenes y flujos de carbono en publicaciones indizadas, no indizadas, tesis, capitulos de libro e informes tecnicos. Los estudios se organizaron en los temas: biomasa, productividad primaria, produccion de hojarasca, respiracion del suelo y descomposicion. Todos los estudios localizados se realizaron entre 1980 y 2018 y mas del 80% se produjo en el presente siglo. Mas de 70% de los estudios fueron articulos revisados por pares y realizados en las U...

Soil moisture is an essential measurement to manage water and improve crop production. However, a... more Soil moisture is an essential measurement to manage water and improve crop production. However, agricultural research in the Yaqui Valley (in northwestern Mexico) with extensive wheat fields (Triti...