Pollen deposit along an environmental gradient in the Celtral Andes of Jujuy, NW Argentina

TORRES G, R.

Buenos Aires

Workshop; Humboldt Colloquium; 2018

Fundación Von Humboldt

The complex relief of mountain regions strongly affects atmospheric circulation generating local winds known as valley-mountain breeze. Knowing these systems can have an important effect and change the perspective of our understanding on the conditions in which the pollen is deposited. The relief configuration of the río Perico basin (Province of Jujuy, 24° 21?S, 65° 33? O) is a good scenario to study the behavior of the valley breeze and its importance to understand the processes affecting the pollen transport and deposit. The general aim of this work is to study the current mechanisms of pollen transport and deposit of Yungas´s species (Alnus acuminata, Juglans australis, Podocarpus palatorei, Celtis, among others) along an altitudinal gradient in order to comprise the changes found in surface palynologycal and Quaternary spectra in the Eastern Cordillera, Northwest Argentina (NWA). Sunny days with clear sky provide optimum conditions for the devolvement of breeze. The temperature and relative humidity record indicates that the anabatic wind become warmer and drier as daylight advance and the katabatic wind become colder and wetter according the hour advance from sunset to sunrise. Synoptic situations that favor the development of the breeze are related to the establishment of an axis or wedge front over the NWA or the post-frontal anticyclonic conditions. The conditions inhibiting the local system are linked to the establishment of troughs or cold fronts that extend over the region. It was also found that the breeze is active during the months of flowering and pollination of the tree species. Results of the study of deposition patterns of the arboreal pollen tracers (Alnus, Juglans and Myrtaceae) evidenced the effect of the anabatic wind in their upslope transport. The pollen dispersal of the Mountain Forest species occurs in late winter and the breeze during this season presents low relative humidity in the day. Therefore, the tracer transport is associated with dry wind. The sedimentary and pollen fossil record of the peatlands and lagoon Bauza allows inferring environmental changes on a centenary scale in the upper basin of río Perico during the last 2000 years. Current patterns of arboreal pollen transport and deposit support the explanation of frequency changes in the fossil record. Increases in tracer percentages respond to a higher frequency of mountain-valley breeze, while declines are associated with lower frequency of local wind circulation. In turn, the local wind frequency allows inferring environmental conditions during the winter in the past.