Birds are a key factor in the biological regeneration of forests, acting as the means of transportations of tree seeds through large distances. This is one of the conclusions reached by researchers of the University of Oviedo in a study conducted in collaboration with experts from Penn State University (USA) and the CONICET (National Council for Scientific and Technical Research of Argentina), in which a technique of seed marking was implemented for the first time.

The field work, which took place in the Cantabrian Mountains and was published by "Ecology", made use of a new technique of seed marking with heavy nitrogen

Researchers Daniel García and Daniel Martínez, from the Department of Organisms and Systems Biology and the Mixed Unit of Research in Biodiversity of the University of Oviedo, carried out a complex field work that has allowed them to prove that birds are key players for the potential expansion of the forest by carrying seeds through large distances. The renowned Ecology journal recently published as its cover article the results of the research conducted by the experts of the three institutions.

Daniel García stresses that the research may turn into "a compulsory reference in the field, since we provided empirical proof of natural process that, though logically inferable, nobody had proved before". The researcher from the University of Oviedo highlights the technical complexity of the field work they carried out and that "the whole project has been a magnificent example of how the collaboration between researchers from different countries translates positively in the quality of the scientific product".

Tracing the movement of the seeds required the implementation of a new technique: marking with heavy nitrogen. The researchers marked thousands of flowers and incipient fruits of holly and hawthorn from for sites in the Cantabrian Mountains. The trees of origin were marked during the spring, in order to follow the trace throughout the winter, when the birds eat the ripe fruits and defecate their seeds. During six months, the researchers collected thousands of seeds, among them those that had been marked with heavy nitrogen, at different distances from their trees of origin.

The analysis of that material in a mass spectrometer has allowed the researchers to precisely reconstruct the route the seeds had made and to define the influence that this spread has in recovering or expanding a forest.

The international research, coordinated by scientists from the three institutions, was conducted without any specific financial aid to the project. Starting with an initial hypothesis reached by the whole team, each member had a complementary role throughout the whole process of the research. The team from the University of Oviedo was in charge of the ecological aspect of the study. The experts from Penn State University contributed with the technique for marking seeds, while the Argentinian experts took part in the majority of the complex mathematical modeling.