Variación geográfica de la distribución altitudinal de Kageneckia angustifolia (D.Don): Uso de Google Earth como herramienta de muestreo
The treeline corresponds to the altitude that marks the separation between two vegetational formations: Native forest and alpine vegetation, with the temperature the main factor that explains this transition zone. Because de latitudinal variation of temperature, the altitude that define the treeline decreases with increasing latitude. Kageneckia angustifolia, a tree species native to Central Chile, which marks the tree line in the Mediterranean Andes together with other species, constitute an adequate model to proof this prediction. The characterization of geographical distribution of a specie is difficult to perform only through field work. In this case, to characterize the treeline of K. angustifolia, which inhabits in remote areas with difficult access, it is a challenging and expensive task if only field work is considered. Fortunately, these issues can be solved using remote sensing and geographical information systems, who have played an important role on modelling and visualisation of species distribution patterns. First, to characterize the treeline distribution of this species along its latitudinal gradient, Google Earth was used to measure the treeline through a set of transects. Second, with the information of each transect, HOF models were built to estimate the treeline. In third place, through remote sensors, temperature values and continentality index associated with the treeline, were obtained to evaluate the correlation between those variables and this ecotone. The main result of this study is the existence of a no-linear relation between treeline and latitude, being higher in the central zone of the distribution range of the species, and then decreasing towards the south of its distribution; this result is slightly different than expected, however, it opens the possibility to analyse the implications of this result in terms of there being no identical pattern for the altitudinal limit of trees, with behaviour varying according to species, topography and climate. The statistical model constructed reaffirms what is described in the literature on the behaviour of the treeline as a function of latitude (p-value < 0.05), however, it was not possible to establish a robust statistical correlation between this ecotone, temperature and continentality (p-value > 0.05), in contrast to the literature, and what was suggested about this last factor, which could explain part of the complexity of the responses in our country. The findings highlight the need to consider geographical latitude in the determination of altitudinal limits for tree species. The integrated use of Google Earth together with remote sensing may be suitable for studying such large-scale spatial phenomena, thus contributing to a powerful approach to understanding the causes shaping the distribution of tree species around their altitudinal limit.
Kageneckia angustifolia (D.Don), Google Earth, Olivillo
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