University of Natural Resources and Life Sciences, Vienna (BOKU) - Research portal
Gewählte Master / Diploma Thesis:
Greta Schmidt
(2019):
The influence of rock age and altitude on texture and water holding capacity of undisturbed soils from the Galápagos Islands.
Master / Diploma Thesis - Institut für Bodenforschung (IBF),
BOKU-Universität für Bodenkultur,
pp 129.
UB BOKU
obvsg
- Abstract:
- Since Charles Darwin visited the Galápagos Islands in 1835, the islands inspired researchers across the globe. While flora, fauna and geology of the islands have been subject to numerous studies, soils are rather poorly understood, even less so their physical properties. This thesis aims at filling in some of these knowledge gaps by providing data on soil texture and water holding capacity in a systematic way. To this end, a chronosequence and an elevation sequence were studied. The chronosequence consists of soil samples from the islands Isabela, Floreana, Santa Cruz and San Cristóbal covering an age span of 0.97 to 1070 ka, with an additional comparison between different moisture conditions (humid vs. dry and very dry). The samples of the elevation sequence (47 – 866 m a.s.l.) represent an arid, humid or very humid climate formed on either scoria or lava. Water holding capacity was analysed with the pressure plate apparatus and grain size distribution by sieving and sedigraph measurements. The Galápagos soils developed a finer texture and higher plant available water holding capacity with increasing age. Over time, soil profiles became deeper and developed more horizons. Clay accumulation zones were found deeper down in soils as they matured. Moisture regime had a strong effect on texture and water holding capacity, as very dry conditions limited soil development. Weathering seemed to increase with elevation but due to the complexity of parent material types, different soil age and a lack of meteorological data, it was challenging to single out the effect of elevation and climatic changes. Nevertheless, the analysis showed that scoria was more prone to weathering than lava bedrock, likely due to the higher porosity of scoria. The diversity of environmental factors creates a very heterogeneous distribution of soils on the Galápagos archipelago. More research is needed to better understand the role of soils in this unique natural ecosystem.
- Beurteilende(r): Zehetner Franz