2021
Díaz-Álvarez, E. A.; de la Barrera, E.
Influence of land-use on the C and N status of a C4 invasive grass in a semi-arid region: implications for biomonitoring Journal Article
In: Plants, vol. 10, pp. 942, 2021.
Abstract | Links | BibTeX | Tags: atmospheric pollution, biomonitoring, buffel grass, carbon, global ecology, invasive species, nitrogen, pollution, Sonora, stable isotopes
@article{Díaz-Álvarez2021bb,
title = {Influence of land-use on the C and N status of a C4 invasive grass in a semi-arid region: implications for biomonitoring},
author = {E. A. Díaz-Álvarez and E. de la Barrera },
url = {https://www.mdpi.com/2223-7747/10/5/942},
doi = {10.3390/plants10050942},
year = {2021},
date = {2021-05-09},
journal = {Plants},
volume = {10},
pages = {942},
abstract = {Biomonitoring of atmospheric pollution is an increasingly accepted practice. However, most existing biomonitors are usually epiphytic species from mesic environments. This work assessed the suitability of buffelgrass (Cenchrus ciliaris), an invasive C4 grass in northwestern Mexico, as a biomonitor, by means of the spatial distribution of the carbon and nitrogen content and isotopic signatures for grass samples collected from urban, agricultural, and natural areas throughout the state of Sonora. We found the highest tissue carbon content of 45.6% (on a dry weight basis) and highest nitrogen content of 3.31% for buffelgrass from the Yaqui Valley. We also found the lowest δ13C of −15.9‰, and the highest δ15N of 16.7‰ in the same region. In contrast, the lowest carbon and nitrogen content of 39.4 and 1.49% were found for Bahía de Kino and Río Sonora mountains, respectively. The lowest δ15N of 2.18‰ and the highest δ13C of −13.7‰ were measured for two remote locations. These results show the influence that pollutant emissions, including agriculture and transportation, have on elemental and isotopic composition of vegetation. Buffelgrass is most adequate for tracking carbon and nitrogen emissions in arid environments and for determining alterations on nitrogen soil reactions, as a first approximation for saturation.},
keywords = {atmospheric pollution, biomonitoring, buffel grass, carbon, global ecology, invasive species, nitrogen, pollution, Sonora, stable isotopes},
pubstate = {published},
tppubtype = {article}
}
Biomonitoring of atmospheric pollution is an increasingly accepted practice. However, most existing biomonitors are usually epiphytic species from mesic environments. This work assessed the suitability of buffelgrass (Cenchrus ciliaris), an invasive C4 grass in northwestern Mexico, as a biomonitor, by means of the spatial distribution of the carbon and nitrogen content and isotopic signatures for grass samples collected from urban, agricultural, and natural areas throughout the state of Sonora. We found the highest tissue carbon content of 45.6% (on a dry weight basis) and highest nitrogen content of 3.31% for buffelgrass from the Yaqui Valley. We also found the lowest δ13C of −15.9‰, and the highest δ15N of 16.7‰ in the same region. In contrast, the lowest carbon and nitrogen content of 39.4 and 1.49% were found for Bahía de Kino and Río Sonora mountains, respectively. The lowest δ15N of 2.18‰ and the highest δ13C of −13.7‰ were measured for two remote locations. These results show the influence that pollutant emissions, including agriculture and transportation, have on elemental and isotopic composition of vegetation. Buffelgrass is most adequate for tracking carbon and nitrogen emissions in arid environments and for determining alterations on nitrogen soil reactions, as a first approximation for saturation.
2019
Díaz-Álvarez, E. A.; de la Barrera, E.; Arciga-Pedraza, A.; Arróniz-Crespo, M.
Bryophyte enzymatic responses to atmospheric nitrogen deposition: A field validation for potential biomonitors Journal Article
In: The Bryologist, vol. 122, no. 3, pp. 396-403, 2019.
Abstract | Links | BibTeX | Tags: atmospheric pollution, biomonitors, moss, pollution, urban ecology
@article{Díaz-Álvarez2019b,
title = {Bryophyte enzymatic responses to atmospheric nitrogen deposition: A field validation for potential biomonitors},
author = {E. A. Díaz-Álvarez and E. de la Barrera and A. Arciga-Pedraza and M. Arróniz-Crespo},
doi = {10.1639/0007-2745-122.3.396},
year = {2019},
date = {2019-08-19},
journal = {The Bryologist},
volume = {122},
number = {3},
pages = {396-403},
abstract = {The monitoring of atmospheric nitrogen deposition is necessary considering that this kind of environmental pollution is among the leading causes of global biodiversity loss. However, deploying and operating monitoring networks can be cost-prohibitive; the use of naturally occurring biomonitors can be a viable alternative for characterizing such nitrogenous pollution, with bryophytes being of particular promise. For instance, a previous dose-response greenhouse experiment evaluating potential biomonitors of different life-forms revealed that the activities of the enzymes phosphomonoesterase and nitrate reductase respond linearly to simulated nitrogen deposition for the generalist neotropical moss Braunia secunda. The present work is the field validation of B. secunda and Leptodontium pungens, a specialist of oak forests, as biomonitors of nitrogen deposition. Moss samples were collected during the 2009 dry and rainy seasons from fir and oak forests at ‘‘low-pollution’’ or ‘‘high-pollution’’ sites within the Valley of Mexico, where the megalopolis of Mexico City is located, and transported to the laboratory for colorimetric determinations of enzymatic activity. The phosphomonoesterase activity was consistently higher for both mosses from the high-pollution sites than for the low-pollution sites, while the nitrate reductase had a lower activity for the plants collected from the high-pollution sites. These results suggest that the proposed biomonitors are appropriate for the region of study.},
keywords = {atmospheric pollution, biomonitors, moss, pollution, urban ecology},
pubstate = {published},
tppubtype = {article}
}
The monitoring of atmospheric nitrogen deposition is necessary considering that this kind of environmental pollution is among the leading causes of global biodiversity loss. However, deploying and operating monitoring networks can be cost-prohibitive; the use of naturally occurring biomonitors can be a viable alternative for characterizing such nitrogenous pollution, with bryophytes being of particular promise. For instance, a previous dose-response greenhouse experiment evaluating potential biomonitors of different life-forms revealed that the activities of the enzymes phosphomonoesterase and nitrate reductase respond linearly to simulated nitrogen deposition for the generalist neotropical moss Braunia secunda. The present work is the field validation of B. secunda and Leptodontium pungens, a specialist of oak forests, as biomonitors of nitrogen deposition. Moss samples were collected during the 2009 dry and rainy seasons from fir and oak forests at ‘‘low-pollution’’ or ‘‘high-pollution’’ sites within the Valley of Mexico, where the megalopolis of Mexico City is located, and transported to the laboratory for colorimetric determinations of enzymatic activity. The phosphomonoesterase activity was consistently higher for both mosses from the high-pollution sites than for the low-pollution sites, while the nitrate reductase had a lower activity for the plants collected from the high-pollution sites. These results suggest that the proposed biomonitors are appropriate for the region of study.
Osuna-Vallejo, V.; Sáenz-Romero, C.; Escalera-Vázquez, L.; de la Barrera, E.; Lindig-Cisneros, R.
Total mercury in plant tissue from a mining landscape in Western Mexico Journal Article
In: Bulletin of Environmental Contamination & Toxicology, vol. 102, no. 1, pp. 19-24, 2019.
Abstract | Links | BibTeX | Tags: agriculture, biomonitors, conifers, pollution, temperate forest, tropical forest
@article{Osuna-Vallejo2019,
title = {Total mercury in plant tissue from a mining landscape in Western Mexico},
author = {V. Osuna-Vallejo and C. Sáenz-Romero and L. Escalera-Vázquez and E. de la Barrera and R. Lindig-Cisneros},
doi = {10.1007/s00128-018-2488-0},
year = {2019},
date = {2019-01-15},
journal = {Bulletin of Environmental Contamination & Toxicology},
volume = {102},
number = {1},
pages = {19-24},
abstract = {Environmental impacts of mining activities are well known, particularly on-site degradation, but long term effects are less known. Mercury content from vegetation samples from a mine dump and surrounding forests was quantified for understanding the fate of this element in the local the environment. The study area, Tlalpujahua, Michoacán, México, has a mining history going back more than 400 years. Including gold and silver extraction by means of mercury amalgamation for 352 years (1554–1906). Mercury was present in all sampled materials. The highest values correspond to wood samples from the mine dump (13.84 ± 3.88 ppm), while wood samples from adjacent forests had 4.3 ± 2.4 ppm, almost twice as much as coniferous needles, shrub leaves and corn seeds (2.2 ± 0.34 ppm). The highest concentration was found for J. deppeana wood (16.05 ± 2.3 ppm). The capacity of accumulating mercury by Juniperus trees when growing on the mine dumps suggests that this species has a potential to be used for biosequestration purposes.},
keywords = {agriculture, biomonitors, conifers, pollution, temperate forest, tropical forest},
pubstate = {published},
tppubtype = {article}
}
Environmental impacts of mining activities are well known, particularly on-site degradation, but long term effects are less known. Mercury content from vegetation samples from a mine dump and surrounding forests was quantified for understanding the fate of this element in the local the environment. The study area, Tlalpujahua, Michoacán, México, has a mining history going back more than 400 years. Including gold and silver extraction by means of mercury amalgamation for 352 years (1554–1906). Mercury was present in all sampled materials. The highest values correspond to wood samples from the mine dump (13.84 ± 3.88 ppm), while wood samples from adjacent forests had 4.3 ± 2.4 ppm, almost twice as much as coniferous needles, shrub leaves and corn seeds (2.2 ± 0.34 ppm). The highest concentration was found for J. deppeana wood (16.05 ± 2.3 ppm). The capacity of accumulating mercury by Juniperus trees when growing on the mine dumps suggests that this species has a potential to be used for biosequestration purposes.
2018
Díaz-Álvarez, E. A.; de la Barrera, E.
Characterization of nitrogen deposition in a megalopolis by means of atmospheric biomonitors Journal Article
In: Scientific Reports, vol. 8, pp. 13569, 2018.
Abstract | Links | BibTeX | Tags: biomonitors, epiphytes, Mexico, mosses, nitrogen, pollution, stable isotopes, Tillandsia, urban ecology
@article{Díaz-Álvarez2018b,
title = {Characterization of nitrogen deposition in a megalopolis by means of atmospheric biomonitors},
author = {E. A. Díaz-Álvarez and E. de la Barrera },
url = {https://rdcu.be/6jWU},
doi = {10.1038/s41598-018-32000-5},
year = {2018},
date = {2018-09-11},
journal = {Scientific Reports},
volume = {8},
pages = {13569},
abstract = {An increase of nitrogen deposition resulting from human activities is not only a major threat for global biodiversity, but also for human health, especially in highly populated regions. It is thus important and in some instances legally mandated to monitor reactive nitrogen species in the atmosphere. The utilization of widely distributed biological species suitable for biomonitoring may be a good alternative. We assessed the suitability of an ensemble of atmospheric biomonitors of nitrogen deposition by means of an extensive sampling of a lichen, two mosses, and a bromeliad throughout the Valley of Mexico, whose population reaches 30 million, and subsequent measurements of nitrogen metabolism parameters. In all cases we found significant responses of nitrogen content, C:N ratio and the δ15N to season and site. In turn, the δ15N for the mosses responded linearly to the wet deposition. Also, the nitrogen content (R2 = 0.7), the C:N ratio (R2 = 0.6), and δ15N (R2 = 0.5) for the bromeliad had a linear response to NOx. However, the bromeliad was not found in sites with NOx concentrations exceeding 80 ppb, apparently of as a consequence of exceeding nitrogen. These biomonitors can be utilized in tandem to determine the status of atmospheric nitrogenous pollution in regions without monitoring networks for avoiding health problems for ecosystems and humans.},
keywords = {biomonitors, epiphytes, Mexico, mosses, nitrogen, pollution, stable isotopes, Tillandsia, urban ecology},
pubstate = {published},
tppubtype = {article}
}
An increase of nitrogen deposition resulting from human activities is not only a major threat for global biodiversity, but also for human health, especially in highly populated regions. It is thus important and in some instances legally mandated to monitor reactive nitrogen species in the atmosphere. The utilization of widely distributed biological species suitable for biomonitoring may be a good alternative. We assessed the suitability of an ensemble of atmospheric biomonitors of nitrogen deposition by means of an extensive sampling of a lichen, two mosses, and a bromeliad throughout the Valley of Mexico, whose population reaches 30 million, and subsequent measurements of nitrogen metabolism parameters. In all cases we found significant responses of nitrogen content, C:N ratio and the δ15N to season and site. In turn, the δ15N for the mosses responded linearly to the wet deposition. Also, the nitrogen content (R2 = 0.7), the C:N ratio (R2 = 0.6), and δ15N (R2 = 0.5) for the bromeliad had a linear response to NOx. However, the bromeliad was not found in sites with NOx concentrations exceeding 80 ppb, apparently of as a consequence of exceeding nitrogen. These biomonitors can be utilized in tandem to determine the status of atmospheric nitrogenous pollution in regions without monitoring networks for avoiding health problems for ecosystems and humans.
Díaz-Álvarez, E. A.; Lindig-Cisneros, R.; de la Barrera, E.
Biomonitors of atmospheric nitrogen deposition: potential uses and limitations Journal Article
In: Conservation Physiology, vol. 6, pp. coy011, 2018.
Abstract | Links | BibTeX | Tags: biomonitors, ecosystem saturation, epiphytes, nitrogen, pollution, stable isotopes, urban ecology
@article{Díaz-Álvarez2018,
title = {Biomonitors of atmospheric nitrogen deposition: potential uses and limitations},
author = {E. A. Díaz-Álvarez and R. Lindig-Cisneros and E. de la Barrera },
doi = {10.1093/conphys/coy011},
year = {2018},
date = {2018-03-13},
journal = {Conservation Physiology},
volume = {6},
pages = {coy011},
abstract = {Atmospheric nitrogen deposition is the third largest cause of global biodiversity loss, with rates that have more than doubled over the past century. This is especially threatening for tropical regions where the deposition may soon exceed 25 kg of N ha–1 year–1, well above the threshold for physiological damage of 12-20 kg of N ha–1 year–1, depending on plant species and nitrogenous compound. It is thus urgent to monitor these regions where the most diverse biotas occur. However, most studies have been conducted in Europe, the USA, and recently in China. This review presents the case for the potential use of biological organisms to monitor nitrogen deposition, with emphasis on tropical plants. We first present an overview of atmospheric chemistry and the nitrogen metabolism of potential biomonitors, followed by a framework for monitoring nitrogen deposition based on the simultaneous use of various functional groups. In particular, the tissue nitrogen content responds to the rate of deposition, especially for mosses, whose nitrogen content increases by 1% per kilogram of N ha-1 year-1. The isotopic signature, δ15N, is a useful indicator of the nitrogen source, as the slightly negative values (e.g., 5‰) of plants from natural environments can become very negative (–11.2‰) in sites with agricultural and husbandry activities, but very positive (13.3‰) in urban environments with high vehicular activity. Mosses are good biomonitors for wet deposition and atmospheric epiphytes for dry deposition. In turn, the nitrogen saturation of ecosystems can be monitored with trees whose isotopic values increase with saturation. Although given ecophysiological limitations of different organisms, particular studies should be conducted in each area of interest to determine the most suitable biomonitors. Overall, biomonitors can provide an integrative approach for characterizing nitrogen deposition in regions where the deployment of automated instruments or passive monitoring is not feasible or can be complementary.
},
keywords = {biomonitors, ecosystem saturation, epiphytes, nitrogen, pollution, stable isotopes, urban ecology},
pubstate = {published},
tppubtype = {article}
}
Atmospheric nitrogen deposition is the third largest cause of global biodiversity loss, with rates that have more than doubled over the past century. This is especially threatening for tropical regions where the deposition may soon exceed 25 kg of N ha–1 year–1, well above the threshold for physiological damage of 12-20 kg of N ha–1 year–1, depending on plant species and nitrogenous compound. It is thus urgent to monitor these regions where the most diverse biotas occur. However, most studies have been conducted in Europe, the USA, and recently in China. This review presents the case for the potential use of biological organisms to monitor nitrogen deposition, with emphasis on tropical plants. We first present an overview of atmospheric chemistry and the nitrogen metabolism of potential biomonitors, followed by a framework for monitoring nitrogen deposition based on the simultaneous use of various functional groups. In particular, the tissue nitrogen content responds to the rate of deposition, especially for mosses, whose nitrogen content increases by 1% per kilogram of N ha-1 year-1. The isotopic signature, δ15N, is a useful indicator of the nitrogen source, as the slightly negative values (e.g., 5‰) of plants from natural environments can become very negative (–11.2‰) in sites with agricultural and husbandry activities, but very positive (13.3‰) in urban environments with high vehicular activity. Mosses are good biomonitors for wet deposition and atmospheric epiphytes for dry deposition. In turn, the nitrogen saturation of ecosystems can be monitored with trees whose isotopic values increase with saturation. Although given ecophysiological limitations of different organisms, particular studies should be conducted in each area of interest to determine the most suitable biomonitors. Overall, biomonitors can provide an integrative approach for characterizing nitrogen deposition in regions where the deployment of automated instruments or passive monitoring is not feasible or can be complementary.
2016
Díaz-Álvarez, E. A.
¿Qué tanto es tantito? Una breve historia del nitrógeno en la era industrial Online
Morelia, UNAM Campus (Ed.): 2016.
Links | BibTeX | Tags: ecophysiology, nitrogen, pollution, urban ecology
@online{Díaz-Álvarez2016,
title = {¿Qué tanto es tantito? Una breve historia del nitrógeno en la era industrial},
author = {E. A. Díaz-Álvarez},
editor = {UNAM Campus Morelia},
url = {http://agro.mx/wp-content/uploads/2017/08/diazalvarez-2016-BUM.pdf},
year = {2016},
date = {2016-12-31},
journal = {Boletín UNAM Morelia (BUM)},
volume = {64},
keywords = {ecophysiology, nitrogen, pollution, urban ecology},
pubstate = {published},
tppubtype = {online}
}
Díaz-Álvarez, E. A.; Reyes-García, C.; de la Barrera, E.
A δ15N assessment of nitrogen deposition for the endangered epiphytic orchid Laelia speciosa from a city and an oak forest in Mexico Journal Article
In: Journal of Plant Research, vol. 129, pp. 863–872, 2016.
Abstract | Links | BibTeX | Tags: conservation physiology, global change, moss, Neo-volcanic axis, nitrogen, orchid, pollution, stable isotopes, urban ecology
@article{Díaz-Álvarez2016b,
title = {A δ15N assessment of nitrogen deposition for the endangered epiphytic orchid Laelia speciosa from a city and an oak forest in Mexico},
author = {E. A. Díaz-Álvarez and C. Reyes-García and E. de la Barrera },
url = {http://rdcu.be/npd1
http://agro.mx/wp-content/uploads/2016/06/039-Diaz-Alvarez-laelia-rv3.pdf
http://link.springer.com/article/10.1007/s10265-016-0843-y},
doi = {10.1007/s10265-016-0843-y},
year = {2016},
date = {2016-06-09},
journal = {Journal of Plant Research},
volume = {129},
pages = {863–872},
abstract = {Atmospheric nitrogen deposition poses a major threat to global biodiversity. Tropical epiphytic plants are especially at risk given their reliance on atmospheric sources of nutrients. The leaf, pseudobulb, and root carbon and nitrogen content, C:N ratio, as well as the nitrogen isotopic composition were studied for individuals of Laelia speciosa from a city and from an oak forest in Mexico. The nitrogen content of leaves was similar between the city and the oak forest, reaching 1.3 ± 0.2 % (dry mass). The δ15N of leaves, pseudobulbs, and roots reached 5.6 ± 0.2 ‰ in the city, values found in sites exposed to industrial and vehicular activities. The δ15N for plant from the oak forest amounted to –3.1 ± 0.3 ‰, which is similar to values measured from sites with low industrial activities. Some orchids such as Laelia speciosa produce a single pseudobulb per year, i.e., a water and nutrient storage organ, so the interannual nitrogen deposition was studied by considering the ten most recent pseudobulbs for plants from either site formed between 2003 and 2012. The C:N ratio of the ten most recent pseudobulbs from the oak forest, as well as that of the pseudobulbs formed before 2010 for plants in the city were indistinguishable from each other, averaging 132.4 ± 6.5, while it was lower for the two most recent pseudobulbs in the city. The δ15N values of pseudobulbs from the oak forest averaged ‒4.4 ± 0.1 ‰ for the entire series. The δ15N ranged from 0.1 ± 1.6 ‰ for the oldest pseudobulb to 4.7 ± 0.2 ‰ for the pseudobulb formed in the city from 2008 onwards. Isotopic analysis and the C:N ratio for L. speciosa revealed that rates of nitrogen deposition were higher in the city than in the forest. The δ15N values of series of pseudobulbs showed that it is possible to track nitrogen deposition over multiple years.},
keywords = {conservation physiology, global change, moss, Neo-volcanic axis, nitrogen, orchid, pollution, stable isotopes, urban ecology},
pubstate = {published},
tppubtype = {article}
}
Atmospheric nitrogen deposition poses a major threat to global biodiversity. Tropical epiphytic plants are especially at risk given their reliance on atmospheric sources of nutrients. The leaf, pseudobulb, and root carbon and nitrogen content, C:N ratio, as well as the nitrogen isotopic composition were studied for individuals of Laelia speciosa from a city and from an oak forest in Mexico. The nitrogen content of leaves was similar between the city and the oak forest, reaching 1.3 ± 0.2 % (dry mass). The δ15N of leaves, pseudobulbs, and roots reached 5.6 ± 0.2 ‰ in the city, values found in sites exposed to industrial and vehicular activities. The δ15N for plant from the oak forest amounted to –3.1 ± 0.3 ‰, which is similar to values measured from sites with low industrial activities. Some orchids such as Laelia speciosa produce a single pseudobulb per year, i.e., a water and nutrient storage organ, so the interannual nitrogen deposition was studied by considering the ten most recent pseudobulbs for plants from either site formed between 2003 and 2012. The C:N ratio of the ten most recent pseudobulbs from the oak forest, as well as that of the pseudobulbs formed before 2010 for plants in the city were indistinguishable from each other, averaging 132.4 ± 6.5, while it was lower for the two most recent pseudobulbs in the city. The δ15N values of pseudobulbs from the oak forest averaged ‒4.4 ± 0.1 ‰ for the entire series. The δ15N ranged from 0.1 ± 1.6 ‰ for the oldest pseudobulb to 4.7 ± 0.2 ‰ for the pseudobulb formed in the city from 2008 onwards. Isotopic analysis and the C:N ratio for L. speciosa revealed that rates of nitrogen deposition were higher in the city than in the forest. The δ15N values of series of pseudobulbs showed that it is possible to track nitrogen deposition over multiple years.
2015
Díaz-Álvarez, E. A.; Lindig-Cisneros, R.; de la Barrera, E.
Responses to simulated nitrogen deposition by the neotropical epiphytic orchid Laelia speciosa Journal Article
In: PeerJ, vol. 3, pp. e1021, 2015.
Abstract | Links | BibTeX | Tags: acid rain, biodiversity, CAM, conservation physiology, d15N, global change, Laelia, neotropical, nitrogen, orchid, plant nutrition, pollution, stable isotopes
@article{Díaz-Álvarez2015,
title = {Responses to simulated nitrogen deposition by the neotropical epiphytic orchid Laelia speciosa},
author = {E. A. Díaz-Álvarez and R. Lindig-Cisneros and E. de la Barrera},
url = {https://peerj.com/articles/1021/
http://agro.mx/wp-content/uploads/2015/06/031-Díaz-Alvarez-et-al-2015-PeerJ-Laelia.pdf},
doi = {10.7717/peerj.1021},
year = {2015},
date = {2015-06-18},
journal = {PeerJ},
volume = {3},
pages = {e1021},
abstract = {Potential ecophysiological responses to nitrogen deposition, which is considered to be one of the leading causes for global biodiversity loss, were studied for the endangered endemic Mexican epiphytic orchid, Laelia speciosa, via a shadehouse dose-response experiment (doses were 2.5, 5, 10, 20, 40, and 80 kg N ha-1 yr-1) in order to assess the potential risk facing this orchid given impending scenarios of nitrogen deposition. Lower doses of nitrogen of up to 20 kg N ha yr–1, the dose that led to optimal plant performance, acted as fertilizer. For instance, the production of leaves and pseudobulbs were respectively 35% and 36% greater for plants receiving 20 kg N ha yr–1 than under any other dose. Also, the chlorophyll content and quantum yield peaked at 0.66 ± 0.03 g m-2 and 0.85 ± 0.01, respectively, for plants growing under the optimum dose. In contrast, toxic effects were observed at the higher doses of 40 and 80 kg N ha yr–1. The δ13C for leaves averaged –14.7 ± 0.2‰ regardless of the nitrogen dose. In turn, δ15N decreased as the nitrogen dose increased from 0.9 ±0.1‰ under 2.5 kg N ha-1 yr-1 to – 3.1 ± 0.2 ‰ under 80 kg N ha-1 yr-1, indicating that orchids preferentially assimilate NH4+ rather than NO3– of the solution under higher doses of nitrogen. Laelia speciosa showed a clear response to inputs of nitrogen, thus, increasing rates of atmospheric nitrogen deposition can pose an important threat for this species.},
keywords = {acid rain, biodiversity, CAM, conservation physiology, d15N, global change, Laelia, neotropical, nitrogen, orchid, plant nutrition, pollution, stable isotopes},
pubstate = {published},
tppubtype = {article}
}
Potential ecophysiological responses to nitrogen deposition, which is considered to be one of the leading causes for global biodiversity loss, were studied for the endangered endemic Mexican epiphytic orchid, Laelia speciosa, via a shadehouse dose-response experiment (doses were 2.5, 5, 10, 20, 40, and 80 kg N ha-1 yr-1) in order to assess the potential risk facing this orchid given impending scenarios of nitrogen deposition. Lower doses of nitrogen of up to 20 kg N ha yr–1, the dose that led to optimal plant performance, acted as fertilizer. For instance, the production of leaves and pseudobulbs were respectively 35% and 36% greater for plants receiving 20 kg N ha yr–1 than under any other dose. Also, the chlorophyll content and quantum yield peaked at 0.66 ± 0.03 g m-2 and 0.85 ± 0.01, respectively, for plants growing under the optimum dose. In contrast, toxic effects were observed at the higher doses of 40 and 80 kg N ha yr–1. The δ13C for leaves averaged –14.7 ± 0.2‰ regardless of the nitrogen dose. In turn, δ15N decreased as the nitrogen dose increased from 0.9 ±0.1‰ under 2.5 kg N ha-1 yr-1 to – 3.1 ± 0.2 ‰ under 80 kg N ha-1 yr-1, indicating that orchids preferentially assimilate NH4+ rather than NO3– of the solution under higher doses of nitrogen. Laelia speciosa showed a clear response to inputs of nitrogen, thus, increasing rates of atmospheric nitrogen deposition can pose an important threat for this species.