Some of the researchers: From left to right, Vicente Ferrer, Javier Peralta, Jesús Álvarez, Rosa María Canals, Leire Múgica, María Durán, Leticia San Emeterio, Esther Rupérez, Ana Juaristi, Rubén Gutiérrez and Javier Pedro.

When agricultural land use and grazing pressure on soil diminish, a natural process of scrubland formation takes place, with the subsequent appearance of woodland, thus recuperating to forest covering somewhat. Nevertheless, in certain zones of the Navarre Pyrenees there has been an aggressive spread of an autochthonous graminea plant (Brachypodium pinnatum); not only successfully establishing itself on extensive slopes, but also other autochthonous species have done the same, degrading the pastureland and causing loss of biodiversity and functionality. Aware of this situation, researchers from the Fitotecnia Group at the Public University of Navarre (UPNA) are working on a project to identify the factors giving rise to this invasive behaviour and thus enable establishing effective control mechanisms.

This environmental problem is not just of local interest, given that, over recent decades, the same process with the same plant has been observed in other European countries (England, Holland, Switzerland, Italy, etc.). Rosa María Canals, permanent lecturer at the Department of Agricultural Production of the UPNA and the person responsible for the project, states: “Invasive behaviour of native gramínea Brachypodium pinnatum: analysis of factors and processes for the control of its spread in the north of the Peninsula”. This involves work over a four-year period, terminating in December 2014.

The researcher previously participated in drawing up land-use plans for various Navarre common grazing lands in the Aezkoa Valley “We were particularly struck by the scale of expansion of Brachypodium pinnatum (alka in Basque), forming extensive coverings that animal herds rejected, for its degree of thickening and its low forage quality”.

This graminea plant is present on pastures and scrubland in temperate Europe. “We cannot describe it as an invasive plant as this concept is only applicable to non-autochthonous species; this is why we talk of aggressive expansion. For specific reasons, which we will attempt to analyse, this plant which, under normal conditions, forms part of diverse plant communities, ends up completely dominating the grazing land, impeding the proliferation of other plants and causing a loss in the diversity and functionality of the plant community”.

Agricultural burning and scant presence of animal herds

Slopes covered with Brachypodium pinnatum (brown colour). Aezkoa Valley

The zone most affected in Navarre belongs to the Puertos Grandes common pastureland (1,700 hectares), in the northern sector of the Aezkoa Valley. The three questions to which the research team is trying to find the answers are: to what extent is the plant spreading throughout the Pyrenees? What factors trigger this species to becoming the dominant one and to eliminate other species? What mechanism does the plant use to maintain itself and not allow the development of the pastureland?

To respond to the first question, the expansion of Brachypodium pinnatum is being studied using images obtained by satellite. “First the plant communities on the terrain are identified through field work, and then these compared with information from satellite images. Once we manage to correctly identify the coverings of Brachypodium pinnatum from satellite images, we will be able to quantify the progress of this graminea in time and space in Puertos Grandes over recent decades, and also be able to study the patterns of expansion on a landscape level.”

As regards the factors that might result in the expansion and establishment of this plant, the researchers are focusing on studying the effects of the traditional burning off of the land at plot level. “The winter burning off of vegetative cover in order to control the brushwood and improve the grazing land is something that herders have been traditionally undertaking in mountainous zones and many of them believe that there is a relation between the burnings and the spread of the graminea”, pointed out Ms. Canals. The work team has investigated the effects of winter controlled burnings over recent years, both on the soil and on the mountain pasture vegetation. “The winter controlled burnings for improving grazing pastures are permitted by the Administration. This why it is essential to know precisely the environmental effects of the burnings, in order to decide if it is an advisable practice or not, and in any case, to provide correct guidelines about how to carry it out and on effectiveness in the control of brushwood and the establishment of diverse grazing land.”

Greater absorption of nutrients

Brachypodium pinnatum

The research undertaken to date indicate that one of the mineral nutrients that most changes in the soil is ammonia and it has been shown that Brachypodium pinnatum is capable of absorbing it better than other species common to pastureland. “We believe that this better capacity for absorption could be one of the factors that trigger its expansion after several burnings. Then other factors such as the lack of heavy grazing pressure which controls the growth of the plant could be important.”

Thus, Rosa María Canals points out, one of the problems may be the recurrence of the burnings: “because it is true that the burnings favour the mineralisation of important nutrients for plant growth but, if it is undertaken continuously, we believe that they can end up impoverishing the quality of the soil. The theme of recurrent burnings merits longer-term research in order to obtain relevant conclusions.”

Finally, as regards the mechanisms that the Brachypodium pinnatum uses to maintain itself and impede the development of grazing pasture, researchers put forward the hypothesis that “the plant, in a certain manner, acts independently of the soil: its rhizome accumulates sufficient nutrients and translocates them in spring; i.e. it has a rhizome capable of storing the nutrients that are the basis of growth of the plant for the following season”. After an intense summer of sampling in the Aezkoa common pasturelands, the research is at the point of discarding or accepting the hypothesis proposed.

The researchers underlined the cooperation from the local authorities (Junta de Valle de Aezkoa), participating actively in the research with the temporary leasing of plots for the trials. “Without this help from the Valley, and the interest shown throughout, this research could not have been undertaken. We hope to treat the information collected in these past few years in order to disseminate it and draw practical conclusions. In any case, this kind of research is long-term; it requires much work and many years to answer all the questions arising. If we achieve further funding, we will be able to do it; we do not lack motivation, although we are living in difficult times”, pointed out Doctor Canals.

* Elhuyar translation, published in www.basqueresearch.com