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:... 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.
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.
Research Interests:
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... 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.