Papers by Alejandra Vovides
Key Message: Morphological plasticity helps plants to
cope to environmental conditions. Allometri... more Key Message: Morphological plasticity helps plants to
cope to environmental conditions. Allometric responses
of the mangrove Avicennia germinans to increasing
salinity are easily detectable when focusing on the top
height trees.
Abstract: Several studies show that mangrove trees possess
high species- and site-related trait allometry, suggesting
large morphological plasticity that might be related to
environmental conditions, but the causes of such variation
are not clearly understood and systematic quantification is
still missing. Both aspects are essential for a mechanistic
understanding of the development and functioning of forests.
We analyzed the role of salinity in the allometric
relations of the mangrove Avicennia germinans, using: (1)
the top height trees (trees with the largest diameters at
breast height, which reflect forest properties at the maximum
use of resources); (2) the slenderness coefficient
(which indicates competition and environmental conditions);
and (3) the crown to DBH ratio. These standard tools
for forest scientists dealing with terrestrial forests are suitable
to analyze the plastic responses of mangroves to
salinity. First, the top height trees help to recognize structural
forest properties that are not detectable when studying
the whole stand. Second, we found that at salinities above
55 %, trees are less slender and develop wider crowns in
relation to DBH than when growing at lower salinities. Our
results suggest a significant change in allometric traits in
relation to salinity, and reflect the plastic responses of tree
traits in response to environmental variation. Understanding
the plastic responses of plants to their environment can help
to better model, predict, and manage forests in changing
environments.
Biology and Fertility of Soils, 2011
Microbial processes are key elements in determining the productivity of mangroves, and reductions... more Microbial processes are key elements in determining the productivity of mangroves, and reductions in these processes reflect the loss of microbial biodiversity and function due to fabricated disturbances. Because nitrogen is a major limiting nutrient for the productivity of these ecosystems, the goal of this study was to determine profiles of inorganic nitrogen combined with several environmental parameters, all in relation to the degree of long-term hydraulic impairment of a tropical, monospecific black mangrove (Avicennia germinans) forest that showed degradation ranging from total loss of mangrove cover to no disturbance. N2-fixation, oxygen levels, and nitrite contents decreased significantly with the severity of the disturbance, and almost null levels were reached in the completely degraded zone, whereas salinity achieved very high values. Concomitantly, total N, ammonium, and P contents and ammonia volatilization increased significantly. Pore-water temperature and pH increased moderately. Other soil physical properties (sand, silt, clay, organic matter, and total C), which varied among the sampling sites, were not correlated with the level of disturbance. Principal component analyses, including environmental and biological parameters, suggested that the most significant finding was the considerable loss of N2-fixation with increasing impairment, which was concomitant with significant increases in volatilization of ammonia and salinity. The results show that microbial N-cycling processes are highly sensitive to salinity and to man-made disturbances that modify the water level and flow.
Ecological Modelling, 2014
This study presents mesoFON, an individual-based mangrove forest dynamics model that advances bey... more This study presents mesoFON, an individual-based mangrove forest dynamics model that advances beyond current models by describing crown plasticity of mangrove trees. The crown plasticity routines take advantage of the fields-of-neighborhood (FON) approach and account for the trunk bending and the differential side branch growth mechanism. Competition for above-/below-ground resources is dealt with separately in this model. Offspring production depends on tree growth and rises with tree ontogeny.
Models based on allometric responses to competing neighbours and environmental conditions in mang... more Models based on allometric responses to competing neighbours and environmental conditions in mangrove forests are increasingly available. However, the improvement of these models requires a mechanistic understanding of how individual trees allocate biomass. This study introduces a new tree model (BETTINA) focusing on this issue. It is designed to investigate the response of trees in terms of biomass allocation patterns to environmental conditions. Additionally, it is suitable as a component of an individual-based mangrove stand model. BETTINA describes the plasticity of trees in growth patterns depending on their below-ground resource uptake. In contrast to the existing mangrove stand models, BETTINA focusses explicitly on the processes leading to variation in resource availability. Based on the physical principle of osmotic potential of solutions, the direct influence of salinity on plant water availability is considered. Allometric model parameters are not restricted to only the above-ground measures of trees' traits (such as stem diameter and height), but also characterize below-ground biomass. Within BETTINA these measures are not limited to predefined empirical maximum values, but are the result of and depend on environmental conditions. The model is suitable to explain allometric measures and relations in dependence on total plant size and environmental conditions (for now salinity and light), and has a great potential for a physiologically and physically based improvement of plant component related biomass estimations.
Trees, 2014
Key Message Morphological plasticity helps plants to cope to environmental conditions. Allometric... more Key Message Morphological plasticity helps plants to cope to environmental conditions. Allometric responses of the mangrove Avicennia germinans to increasing salinity are easily detectable when focusing on the top height trees. Abstract Several studies show that mangrove trees possess high species-and site-related trait allometry, suggesting large morphological plasticity that might be related to environmental conditions, but the causes of such variation are not clearly understood and systematic quantification is still missing. Both aspects are essential for a mechanistic understanding of the development and functioning of forests. We analyzed the role of salinity in the allometric relations of the mangrove Avicennia germinans, using: (1) the top height trees (trees with the largest diameters at breast height, which reflect forest properties at the maximum use of resources); (2) the slenderness coefficient (which indicates competition and environmental conditions); and (3) the crown to DBH ratio. These standard tools for forest scientists dealing with terrestrial forests are suitable to analyze the plastic responses of mangroves to salinity. First, the top height trees help to recognize structural forest properties that are not detectable when studying the whole stand. Second, we found that at salinities above 55 %, trees are less slender and develop wider crowns in relation to DBH than when growing at lower salinities. Our results suggest a significant change in allometric traits in relation to salinity, and reflect the plastic responses of tree traits in response to environmental variation. Understanding the plastic responses of plants to their environment can help to better model, predict, and manage forests in changing environments.
Restoration Ecology, 2011
Although several damaged mangrove ecosystems have been restored worldwide, so far, it has not bee... more Although several damaged mangrove ecosystems have been restored worldwide, so far, it has not been established whether a restored mangrove system regains all the functional properties of preserved mangroves. This study measured nitrogen fixation as an indicator of whether disturbed mangroves that were reforested or naturally regenerated fully recovered from this disturbance at a functional level. Rates of nitrogen fixation were measured for one year in impaired, preserved, reforested, and naturally regenerated mangroves dominated by the black mangrove (Avicennia germinans). There was no significant difference in rates of nitrogen fixation among preserved and adjacent reforested and naturally regenerated mangroves, but a significant reduction occurred in an impaired mangrove. Nitrogen fixation was mainly controlled by pH, salinity, and temperature. The highest rates of nitrogen fixation occurred in summer at pH values less than 6.4, whereas the impaired mangrove had higher pH and salinity and had very low nitrogen fixation activity. These results suggest that nitrogen fixation can be used as an ecological indicator of the success of reforestation and as a sensitive measure of perturbations in mangroves.
Biology and Fertility of Soils, 2011
Microbial processes are key elements in determining the productivity of mangroves, and reductions... more Microbial processes are key elements in determining the productivity of mangroves, and reductions in these processes reflect the loss of microbial biodiversity and function due to fabricated disturbances. Because nitrogen is a major limiting nutrient for the productivity of these ecosystems, the goal of this study was to determine profiles of inorganic nitrogen combined with several environmental parameters, all in relation to the degree of long-term hydraulic impairment of a tropical, monospecific black mangrove (Avicennia germinans) forest that showed degradation ranging from total loss of mangrove cover to no disturbance. N 2 -fixation, oxygen levels, and nitrite contents decreased significantly with the severity of the disturbance, and almost null levels were reached in the completely degraded zone, whereas salinity achieved very high values. Concomitantly, total N, ammonium, and P contents and ammonia volatilization increased significantly. Pore-water temperature and pH increased moderately. Other soil physical properties (sand, silt, clay, organic matter, and total C), which varied among the sampling sites, were not correlated with the level of disturbance. Principal component analyses, including environmental and biological parameters, suggested that the most significant finding was the considerable loss of N 2 -fixation with increasing impairment, which was concomitant with significant increases in volatilization of ammonia and salinity. The results show that microbial N-cycling processes are highly sensitive to salinity and to man-made disturbances that modify the water level and flow.
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Papers by Alejandra Vovides
cope to environmental conditions. Allometric responses
of the mangrove Avicennia germinans to increasing
salinity are easily detectable when focusing on the top
height trees.
Abstract: Several studies show that mangrove trees possess
high species- and site-related trait allometry, suggesting
large morphological plasticity that might be related to
environmental conditions, but the causes of such variation
are not clearly understood and systematic quantification is
still missing. Both aspects are essential for a mechanistic
understanding of the development and functioning of forests.
We analyzed the role of salinity in the allometric
relations of the mangrove Avicennia germinans, using: (1)
the top height trees (trees with the largest diameters at
breast height, which reflect forest properties at the maximum
use of resources); (2) the slenderness coefficient
(which indicates competition and environmental conditions);
and (3) the crown to DBH ratio. These standard tools
for forest scientists dealing with terrestrial forests are suitable
to analyze the plastic responses of mangroves to
salinity. First, the top height trees help to recognize structural
forest properties that are not detectable when studying
the whole stand. Second, we found that at salinities above
55 %, trees are less slender and develop wider crowns in
relation to DBH than when growing at lower salinities. Our
results suggest a significant change in allometric traits in
relation to salinity, and reflect the plastic responses of tree
traits in response to environmental variation. Understanding
the plastic responses of plants to their environment can help
to better model, predict, and manage forests in changing
environments.
cope to environmental conditions. Allometric responses
of the mangrove Avicennia germinans to increasing
salinity are easily detectable when focusing on the top
height trees.
Abstract: Several studies show that mangrove trees possess
high species- and site-related trait allometry, suggesting
large morphological plasticity that might be related to
environmental conditions, but the causes of such variation
are not clearly understood and systematic quantification is
still missing. Both aspects are essential for a mechanistic
understanding of the development and functioning of forests.
We analyzed the role of salinity in the allometric
relations of the mangrove Avicennia germinans, using: (1)
the top height trees (trees with the largest diameters at
breast height, which reflect forest properties at the maximum
use of resources); (2) the slenderness coefficient
(which indicates competition and environmental conditions);
and (3) the crown to DBH ratio. These standard tools
for forest scientists dealing with terrestrial forests are suitable
to analyze the plastic responses of mangroves to
salinity. First, the top height trees help to recognize structural
forest properties that are not detectable when studying
the whole stand. Second, we found that at salinities above
55 %, trees are less slender and develop wider crowns in
relation to DBH than when growing at lower salinities. Our
results suggest a significant change in allometric traits in
relation to salinity, and reflect the plastic responses of tree
traits in response to environmental variation. Understanding
the plastic responses of plants to their environment can help
to better model, predict, and manage forests in changing
environments.