Vegetation responses to late Holocene climate changes in an Andean forest
By Klaas Land (currently studying MSc Biological Sciences (Ecology & Evolution) at the University of Amsterdam.
The discussion during the APC meeting on the 19th of March was on the paper by Schiferl et al. (2018), a very recent study on the climatic shifts in the late Holocene and their effects on the South American tropics. The study had analysed a core going back about 3800 years from Lake Palotoa, which was in the Andean foothills (1370m elevation). They found that subtle changes to the fossil pollen record could be identified around the estimated periods for the Little Ice Age (LIA) and Medieval Climate Anomaly (MCA). The focus in the paper was set on the results concerning the Hedyosmum and Sloanea species, which increased in abundance during the MCA. Both species were also abundant during the LIA, but Hedyosmum dipped in abundance between the two periods, while Sloanea stayed abundant up to modern times. Both these species are characteristic of wet soils, and thus it was theorised that there must have been an increase in moisture in the atmosfeer. Another interesting trend in these periods, was the decrease in abundance of the Dictyocaryum palm, a species that prefers to have its head in the clouds but is otherwise out-competed by a closely related palm species, Iriartea (Henderson, 1990). The discussion that followed was mostly about how Dictyocaryum could be used to directly identify the spatial movement of the cloud layer, based on the appearance and abundance of the palm. Since pollen are known to show a regional signal, it might be interesting to look at the vegetation on a more local scale, using phytoliths. It just so happens that Dictyocaryum produces a particular kind of phytolith (Huisman et al., 2018) that can be identified and counted fairly easily. A core from a mid-elevation Andean lake could give valuable insight into the abundance of Dictyocaryum and other cloud immersion dependant species, and in turn show the effects of climatic shifts on the cloud forests of the Andes.
- Henderson, A. (1990). Arecaceae. Part I. Introduction and the Iriarteinae. Flora Neotropica, 1-100. Jstor link
- Huisman, S.N., Bush, M.B. & McMichael, C.N.H. (2019) Four centuries of vegetation change in the mid-elevation Andean forests of Ecuador. Vegetation History and Archaeobotany. DOI: 10.1007/s00334-019-00715-8
- Schiferl, J. D., Bush, M. B., Silman, M. R., & Urrego, D. H. (2018). Vegetation responses to late Holocene climate changes in an Andean forest. Quaternary Research, 89(1), 60-74. DOI: 10.1017/qua.2017.64