The study was led by Anne-Karine Boulet, researcher at the Centre for Natural Resources, Environment and Society (CERNAS) of the School of Agriculture of the Polytechnic Institute of Coimbra (IPC).
"The work carried out aimed to identify differences in the hydrological processes of two small forest basins with an area of less than one km2, one of them dominated by maritime pines [Pinus pinaster Aiton] aged over 20 years and the other dominated by eucalyptus [Eucalyptus globulus Labill] of various ages, and covers six years of study, from 2010 to 2016," says a statement from the IPC.
According to the note, the study was developed in basins with similar physical characteristics, located in the Caramulo Mountains, with a humid Mediterranean climate and schist mother rock.
"The continuous measurement of precipitation and stream flow allowed to calculate the water balance of the two basins and also to analyse their response to rainfall episodes, as well as to establish correlations between several parameters, namely precipitation characteristics, evapotranspiration rates, soil moisture, surface runoff and soil coverage," it is referred.
The source indicates that "the average annual evapotranspiration of the basin with a predominance of pine trees was 907 mm, higher than in the basin populated entirely with eucalyptus (739 mm), showing that pine stands with over 20 years consume more water than a mixture of eucalyptus stands of varying ages".
The Polytechnic of Coimbra states that over the six years of research, "the annual evapo-transpiration rates varied between 37 percent and 78 percent in pine forests and between 34 percent and 73 percent in eucalyptus forests, between the wettest and driest year", which, for Anne-Karine "raises concerns about the impact of climate change on water availability during drier periods in mountainous areas in regions with Mediterranean climates".
Given that the results obtained in the study contradict the preconceived idea that the eucalyptus consumes more water than the pine, the research coordinator alerts to the "importance of the type of forest", safeguarding, however, "that the results obtained were validated for very specific climate and soil conditions and cannot be generalised to the whole territory".
The conclusions of the study are contained in the article "Hydrological Processes in Eucalypt and Pine Forested Headwater Catchments within Mediterranean Region", published in the magazine Water 2021, special edition "Impact of Land-Use Changes on Surface Hydrology and Water Quality" (available at https://www.mdpi.com/2073-4441/13/10/1418).
The article is the result of the research carried out by Anne-Karine Boulet in the context of her PhD thesis, conducted at the University of Aveiro, under the guidance of Celeste Coelho and Jan Jacob Keizer (CESAM - Centre for Environment and Sea Studies) and António Dinis Ferreira (CERNAS-ESAC - Centre for Natural Resources, Environment and Society of the School of Agriculture of the Polytechnic of Coimbra).