|
Descripción
|
|
|---|---|
| Canary Island pine has been living in areas suffering volcanic eruptions for at least 13.5 My. Among the most widespread damages during volcanic eruptions are those caused by toxic element emissions such as mercury, deposition and accumulation of ashes (which cause defoliation, branch loss and burial of vegetation), and the impact of pyroclats (which remove crowns and damage stems). Canary island pine can cope with such damages thanks to its ability to resprout and form dense traumatic heartwood around stem wounds. In the first place, I approached the study of the medium- and long-term effects of harmful mercury emissions as well as the defoliation and trauma of tree stem. For this purpose, four individuals that had survived the 1949 eruption in the native pine stand surrounding Hoyo Negro crater, La Palma Island (Canary Islands, Spain) were located and transverse slices were extracted. Mercury concentrations were determined and both dendrochronological and carbon and oxygen stable isotopes analyses were performed to study the potential entry of mercury and the anatomical and physiological responses to volcanic disturbance. In addition, 8 year old trees were subjected to experimental defoliation and stem damages with the aim of studying the use of reserves and new photoassimilates in the short term recovery process immediately after eruptive damages. To this end, non structural carbohydrates were measured in different tissues and carbon stable isotopes were determined. Samples were taken at different recovery stages during a year in needles stem and roots. Complementarily, radial growth and water use efficiency measurements were performed. The study results allowed for understanding the recovery process from the disturbance to the tree complete recovery. After the eruption damages Canary Island pine trees: i) ceased their radial growth for a period between 3 and 16 years, avoiding carbon utilization on an unnecessary activity on crown-less trees; ii) covered the open wounds with resin and formed traumatic heartwood around them in order to avoid water losses, xylophagous insect and fungus infections; iii) mobilized carbon reserves which are mostly found in the roots (probably due to the lower underground damages caused by eruptions). During the growth cessation period, the carbohydrates were invested in the recovery of crowns, allowing the restoration of the photosynthetic activity and the recovery of the used reserves. Once a certain crown volume was recovered, the individual also restored its growth. Post-eruptive ring growths showed no differences with pre-eruptive ones, and no physiological changes were observed. Likewise, mercury concentrations were similar in pre and post-eruptive wood, although a one-off contribution was recorded in the year of the eruption on the trunk wounds. Canary Island pine adaptations to volcanic eruptions included a series of structures and mechanisms: resprout, dense traumatic heartwood, axial parenchyma, radial growth cessation and reserve storage in roots, among others. These traits seem to allow Pinus canariensis to survive volcanic eruptions where other species would fail to do so. | |
|
Internacional
|
Si |
|
ISBN
|
|
|
Tipo de Tesis
|
Doctoral |
|
Calificación
|
Sobresaliente |
|
Fecha
|
26/09/2017 |