Intensive forest management affects bryophyte diversity in the western Pyrenean silver fir-beech forests

Understanding how bryophytes respond to management gradients in temperate forests is an important issue for their conservation and has major implications for forest management. This is especially true for western Pyrenean silver fir-beech forests, where high bryophyte turnover, as well as species loss, has been reported in the last 30 years. This study is the first to explore bryophyte diversity patterns across western Pyrenean silver fir-beech forests with different management intensities. Our specific aims were to determine the main drivers of bryophyte richness and turnover and explore which bryophyte species can be used as indicators of management intensity. The effect of management was assessed on the overall bryophyte diversity as well as on the bryophyte groups based on taxonomy, life cycle strategy, sensitivity to forest management intensity and habitat preference. Bryophyte diversity was analyzed by generalized linear mixed models and multiple regression analysis on distance matrices. The results suggest that bryophyte richness in the Pyrenean forests is decreasing with intensive forest management. The bryophyte richness decrease on highly disturbed stands can be attributed to a loss of suitable microhabitats, such as large trees. Elevational gradient, as a proxy of climatic factors, is also an important driver of bryophyte species richness in the studied area. Long-lived and epiphytic bryophytes decreased on steep slopes. Turnover was driven by elevation and percentage of large gaps, which might be linked with forest management. The results also suggest that Dierssen's classification of bryophytes regarding sensitivity to forest management is not suitable for the evaluation of the effects of forest management in the studied region. Our main recommendation for bryophyte conservation is to avoid intensive forest management and to minimize the forest practices in steep slopes which are prone to soil erosion.