Influence of burning and mechanical clearing on the provision of Gentiana lutea L. in the Iberian Peninsula

Abstract

Overexploitation, land-use change, and climate warming are compromising the conservation of many plant species across the globe, as well as the benefits they provide to people. The yellow gentian (Gentiana lutea L.) is a hemicryptophyte used for pharmacological and food industries harvested in the mountain systems of Southern Europe, which may be subject of management measures. Here we identify the influence of two common management strategies, burning and clearing, on G. lutea populations, and provide insights on the role of burning on seed germination by analyzing the effect of thermal shocks from a populational approach. To achieve these goals, we selected areas affected by low intensity burning and mechanical clearing over the short term (1–2 years) and over the medium term (6–8 years) in the Cantabrian Mountains (NW Iberian Peninsula), where we sampled the number of basal rosettes, fertile stems and cover of G. lutea, and the total cover of woody species. Likewise, we collected seeds from three populations, which were used to quantify several seed traits and to analyze the germination dynamics after heat shocks alone and combined with a dormancy break treatment (gibberellic acid). Results showed decreases in G. lutea population variables immediately after burning and a full recovery over the medium term. On the contrary, clearing did not show effects over the short-term but largely increased all population variables over the medium term. Among other factors, management effects are mediated by their influence on woody species cover, which constrains G. lutea populational growth. Thermal shocks did not break the dormancy of G. lutea seeds, and thermal shocks combined with forced dormancy break revealed no clear effects of heating. Populational differences in the germinative response were detected, as heavier and less moist seeds require longer time to germinate. Based on our results, we propose mechanical clearing as a suitable management strategy to sustain G. lutea populations in NW Iberian Peninsula, but we recommend further analysis to extrapolate our advice to sites with distinct environmental conditions.