8 research outputs found
The Taxonomy, Reproduction, and Distribution of Rare Plants: A Study of Magnolia sp. in the Río Zuñac Reserve, Ecuador
Ecuadorian cloud forests are biodiversity hotspots and centers of unprecedented levels of endemism, but they are also under-researched and under-protected. This study took place in the Río Zuñac Reserve, which is a reserve of about 850 ha located in the Tungurahua province of Ecuador, and is home to at least 20 endemic plant species. Three new species of Magnolia have been discovered in this reserve in the past five years: Magnolia llanganates, Magnolia vargasiana, and one species that has yet to be formally described. This study dealt with accurately locating and describing new individuals of these species over the course of three weeks. Twelve individuals of M. vargasiana were discovered, increasing the total number of registered individuals to 18. Seven new individuals of the newly discovered species were found, raising the total number to nine. Nine juvenile individuals were found, two of which were identified as being of the new species and five of which were M. vargasiana. A map of the distributions of the three species was created using GoogleEarth, which can be used by a drone to locate the individuals for remote research. The elevation range of M. llanganatensis was significantly lower than the other two species, which both overlap in their elevation ranges almost entirely. Visually, the leaf shapes of the three species are markedly different, which was supported by leaf ratio measurements of length to width. Flowers provide better data for comparison between Magnolia sp., but this study took place outside of the peak flowering season for all three species. Five flowers/buds were collected from the newly discovered species and observational comparisons were made between these and flower statistics of the other two species. Herbivory on magnolias between two of the ridges sampled from was significantly different and was also significantly higher in M. vargasiana than in the other two species.
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Los bosques nublados de Ecuador son áreas de alta biodiversidad y de niveles altos de endemismo de especies, pero a pesar de eso hay una falta de investigaciones científicas y de protección. Este estudio tuvo lugar en la Reserva Río Zuñac, la cual es una reserva de alrededor de 850 ha ubicada en Tungurahua, Ecuador y habitada por por lo menos 20 especies endémicas de plantas. Tres especies de Magnolia han sido descubiertas en los últimos cinco años: Magnolia llanganatensis, Magnolia vargasiana, y una especie que todavía no ha sido descrita. El estudio se ocupó de ubicar y describir individuos nuevos de estas tres especies durante tres semanas. Diez individuos de M. vargasiana fueron descubiertos, y ahora hay un total de 16 individuos registrados. Se encontraron siete individuos de la especie nueva para hacer un total de nueve individuos registrados. Nueve juveniles fueron descubiertos, de los cuales dos son de la nueva especie y cinco de M. vargasiana. Un mapa de la distribución de las tres especies fue creado con GoogleEarth, el cual puede ser usado por un drone para ubicar los individuos para hacer investigaciones remotas. La distribución de elevación de M. llanganatensis fue significativamente más baja que las otras dos especies, estas casi totalmente se sobreponen. Visualmente, las formas de las hojas de las tres especies son marcadamente diferentes, y esto es comprobado por las medidas del ratio de largo y ancho de las hojas. Sus flores proveen datos mejores para comparar entre las especies., pero este estudio ocurrió fuera de la estación de florecimiento de todas las especies. Cinco flores/botones fueron recolectados de la especie nueva y comparaciones observacionales fueron hechas entre estas flores y las estadísticas en cuanto a las flores de las otras especies. El nivel de herbivoría en las magnolias entre dos cuchillos en la reserva fue significativamente diferente y también fue significativamente más alta en M. vargasiana que en las otras dos especies
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Acclimation of Trees to Elevated Growing Temperatures: From Concrete Jungles to Boiling Rivers
Plant performance is modulated by temperature. Individual plants may respond morphologically, physiologically, and/or behaviorally to changes in temperature to maintain homeostasis. While we know that plants are broadly adapted to the climate in their regions of origin, our understanding of how plants are responding physiologically to climate warming at the individual level remains relatively limited, especially at low latitudes. This knowledge gap is alarming, considering (1) the rapid pace of anthropogenic climate change, which primarily necessitates individual level acclimation to change rather than adaptation or range shifting for the survival of species, and (2) the hypothesized reduced phenotypic plasticity and acclimatory capabilities of low latitude species due to their evolution under generally relatively stable conditions. Furthermore, our lack of understanding surrounding subtropical and tropical plant acclimation precludes accurate predictions of how forests and other terrestrial ecosystems in these major global regions will be affected by climate change. To address this gap, I investigated the acclimation of trees to elevated growing temperatures along steep thermal gradients in Miami, Florida, USA and in the Amazon region of Peru. In Chapter 2, I estimated the leaf thermal safety margins (TSMs) of street tree species that are planted in Miami to assess their thermal vulnerability to projected future climate change, focusing especially on differences between native and exotic species pools and on species’ resilience to multiple abiotic stressors. For Chapters 3 and 4, I investigated acclimation of thermal and photosynthetic leaf traits in street trees across Miami’s urban heat island. Finally, in Chapter 5 I assessed the acclimation of thermal leaf traits in tree species native to the lowland Amazon along a natural thermal gradient at the Boiling River, Peru. My findings provide insight into the vulnerability of low latitude trees to climate warming and how individual-level plasticity may play a role in their responses to climate change.</p
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Limited acclimation of leaf traits and leaf temperatures in a subtropical urban heat island
The consequences of rising temperatures for trees will vary between species based on their abilities to acclimate their leaf thermoregulatory traits and photosynthetic thermal tolerances. We tested the hypotheses that adult trees in warmer growing conditions (1) acclimate their thermoregulatory traits to regulate leaf temperatures and (2) acclimate their thermal tolerances such that tolerances are positively correlated with leaf temperature, and that (3) species with broader thermal niche breadths have greater acclimatory abilities. To test these hypotheses, we measured leaf traits and thermal tolerances of seven focal tree species across steep thermal gradients in Miami's urban heat island. We found that some functional traits varied significantly across air temperatures within species. For example, leaf thickness increased with maximum air temperature in three species, and leaf mass per area and leaf reflectance both increased with air temperature in one species. Only one species was marginally more homeothermic than expected by chance due to acclimation of its thermoregulatory traits, but this acclimation was insufficient to offset elevated air temperatures. Thermal tolerances acclimated to higher maximum air temperatures in two species. As a result of limited acclimation, leaf Thermal Safety Margins (TSMs) were narrower for trees in hotter areas. We found some support for our hypothesis that species with broader thermal niches are better at acclimating in order to maintain more-stable TSMs across the temperature gradients. These findings suggest that trees have limited abilities to acclimate to high temperatures and that thermal niche specialists may be at a heightened risk of thermal stress as global temperatures continue to rise
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Urban Heat Islands and What They Can Teach Us About Climate Change
Urban areas typically get much hotter than rural or natural areas. The higher temperatures in cities are caused by the presence of lots of buildings and streets, which heat up in the sun because they are made of materials that can not hold much water. In hot urban areas, called urban heat islands, people and animals stay cool by sweating, panting, and staying in shady areas. Even urban trees can stay cool by transpiring, which is like sweating. In fact, trees transpire so much that they can cool down the air and reduce the urban heat effect—like natural air conditioning. Although the urban heat effect is typically viewed as a problem, scientists can study the plants and animals living in urban heat islands to understand the effects that rising temperatures due to climate change will have on these species in their natural habitats
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Thermal optimum of photosynthesis is controlled by stomatal conductance and does not acclimate across an urban thermal gradient in six subtropical tree species
Modelling the response of plants to climate change is limited by our incomplete understanding of the component processes of photosynthesis and their temperature responses within and among species. For ≥20 individuals, each of six common subtropical tree species occurring across steep urban thermal gradients in Miami, Florida, USA, we determined rates of net photosynthesis (A
), maximum RuBP carboxylation, maximum RuBP regeneration and stomatal conductance, and modelled the optimum temperature (T
) and process rate of each parameter to address two questions: (1) Do the T
of A
(T
) and the maximum A
(A
) of subtropical trees reflect acclimation to elevated growth temperatures? And (2) What limits A
in subtropical trees? Against expectations, we did not find significant acclimation of T
, A
or the T
of any of the underlying photosynthetic parameters to growth temperature in any of the focal species. Model selection for the single best predictor of A
both across leaf temperatures and at T
revealed that the A
of most trees was best predicted by stomatal conductance. Our findings are in accord with those of previous studies, especially in the tropics, that have identified stomatal conductance to be the most important factor limiting A
, rather than biochemical thermal responses
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Tropical Trees Will Need to Acclimate to Rising Temperatures—But Can They?
For tropical forests to survive anthropogenic global warming, trees will need to avoid rising temperatures through range shifts and “species migrations” or tolerate the newly emerging conditions through adaptation and/or acclimation. In this literature review, we synthesize the available knowledge to show that although many tropical tree species are shifting their distributions to higher, cooler elevations, the rates of these migrations are too slow to offset ongoing changes in temperatures, especially in lowland tropical rainforests where thermal gradients are shallow or nonexistent. We also show that the rapidity and severity of global warming make it unlikely that tropical tree species can adapt (with some possible exceptions). We argue that the best hope for tropical tree species to avoid becoming “committed to extinction” is individual-level acclimation. Although several new methods are being used to test for acclimation, we unfortunately still do not know if tropical tree species can acclimate, how acclimation abilities vary between species, or what factors may prevent or facilitate acclimation. Until all of these questions are answered, our ability to predict the fate of tropical species and tropical forests—and the many services that they provide to humanity—remains critically impaired
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Leaf thermal safety margins decline at hotter temperatures in a natural warming 'experiment' in the Amazon
The threat of rising global temperatures may be especially pronounced for low-latitude, lowland plant species that have evolved under stable climatic conditions. However, little is known about how these species may acclimate to elevated temperatures. Here, we leveraged a strong, steep thermal gradient along a natural geothermal river to assess the ability of woody plants in the Amazon to acclimate to elevated air temperatures. We measured leaf traits in six common tropical woody species along the thermal gradient to investigate whether individuals of these species: acclimate their thermoregulatory traits to maintain stable leaf temperatures despite higher ambient temperatures; acclimate their photosynthetic thermal tolerances to withstand hotter leaf temperatures; and whether acclimation is sufficient to maintain stable leaf thermal safety margins (TSMs) across different growth temperatures. Individuals of three species acclimated their thermoregulatory traits, and three species increased their thermal tolerances with growth temperature. However, acclimation was generally insufficient to maintain constant TSMs. Notwithstanding, leaf health was generally consistent across growth temperatures. Acclimation in woody Amazonian plants is generally too weak to maintain TSMs at high growth temperatures, supporting previous findings that Amazonian plants will be increasingly vulnerable to thermal stress as temperatures rise