The subalpine forest was 200 meters higher 5,700 years ago
The subalpine forest was 200 meters higher 5,700 years ago
5,700 years ago, the subalpine forest was more extensive and was at least 200 meters higher than at present. This is one of the main conclusions of an international study, led by researchers from the Higher Council for Scientific Research (CSIC) (Spain), which reconstructs for the first time the altitudinal variations of trees in the central Pyrenees between 5,700 and 2,200 years ago. The results, published in the Journal of Ecology, point to warmer summers as a main cause than current ones.
Scientists have reached these conclusions after analyzing a record of fossil ice with plant remains found in the Ice Cave A-294, located in the central Pyrenees within the Armeña circus, in the Cotiella massif, at 2,238 meters above sea level. sea.
"This record represents the oldest transformation ice (snow that transforms into ice inside a cave) found to date. It is an extraordinary natural archive that preserves fossil pollen and plant macrofossils in a very good state of conservation ", explains María Leunda, researcher at the CSIC at the Pyrenean Institute of Ecology, in Zaragoza.
The identification of these plant remains has allowed us to study the dynamics of the vegetation on a millennial scale and investigate the changes that have occurred in the mountain landscape. Leunda precises: "The vegetal macrofossils found show that the altitudinal variations in the forest boundary are very linked to changes in the summer temperature".
Record of ice found in the Ice Cave A-294, in the central Pyrenees. July 2015. (Photo: María Leunda)
Specifically, researchers have observed that 5,700 years ago, black pine (Pinus uncinata) formations coexisted with birches (Betula spp.) In the vicinity of the cave. Today, the maximum altitude reached by the arboreal pine limit in the area is 2,000 meters above sea level.
Approximately 4,200 years ago, there was a progressive decline of the forest and alpine meadows were established, dominated by herbaceous plants such as Dryas octopetala, all in response to a cold phase, with a progressive decrease in temperatures, known as the Neoglacial period. "Approximately 1,000 years later the forest boundary rose again until reaching the altitude of the cave, but 2,200 years ago the ice deposit ceased and with it the record of the variations of the forest limits in this area," adds Penelope González-Sampériz , also researcher of the CSIC in the Pyrenean Institute of Ecology.
The existing landscape today shows a very different aspect from the one it had in the past. Currently it is only possible to find herbaceous alpine vegetation. According to the scientists who lead the work, during the last 2,000 years, due to both climatic and human disturbances, the pines would have descended to their current limit in the surroundings of the Armeña circus.
"The sensitivity that has been detected in these subalpine ecosystems suggests that the current temperature increase, together with the abandonment of traditional land uses, will cause the pines and possibly the birches to expand to higher altitudes, thus replacing alpine species, as happened in the past, "says Graciela Gil-Romera, a researcher at the University of Aberystwyth (United Kingdom).
This work, which has also had the collaboration of scientists from the University of Zaragoza and the University of Bern (Switzerland), lays the foundations to carry out forest management and species conservation that takes into account the impact of global change on a millennial scale.
"These frozen files, however, are severely threatened and in danger of disappearing due to the increase in temperatures that we live today. Therefore, we ask that further research be carried out, since all the paleoenvironmental information contained in these ice records can contribute to an improvement in the future predictions of the alpine ecosystems ", concludes Leunda. (Source: CSIC / DICYT)
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