![]() ![]() Thus, pine forests at low elevations are developing into oak forests with unknown consequences for these ecosystems and their goods and services. ![]() The main driving factors are found to be climatic variability, particularly drought, and variability in stand structure and topography. Our results thus suggest that an extended shift in species composition is actually occurring in the pine forests in the Valais. Although both species regenerated well at dry sites, pine regeneration was favoured at cooler sites at higher altitude and oak regeneration was more frequent at warmer sites, indicating a higher adaptation potential of oaks under future warming. Pine regeneration was low in comparison to its occurrence in the overstorey, whereas oak regeneration was comparably abundant. A generalized linear mixed-effects model indicated for the NFI data increased pine mortality on dryer sites with high stand competition, particularly for small-diameter trees. Annual variation in pine mortality was correlated with a drought index computed for the summer months prior to observed tree death. Pine mortality was found to be highest at low elevation (below 1000 m a.s.l.). To study variability in mortality and regeneration in these dry forests we analysed data from the Swiss national forest inventory (NFI) on a regular grid between 19, and combined it with annual mortality data from a monitoring site. However, it remains unclear whether this local change in species composition is part of a larger-scale vegetation shift. ![]() Cleveland State University is an equal opportunity educator and employer. Concurrently the sub-Mediterranean pubescent oak ( Quercus pubescens Willd.) has locally increased in abundance. ©2023 Cleveland State University 2121 Euclid Avenue, Cleveland, OH 44115-2214 (216) 687-2000. In the Swiss Rhone valley (Valais), one of the driest inner-Alpine regions, the species composition in low elevation forests is changing: The sub-boreal Scots pine ( Pinus sylvestris L.) dominating the dry forests is showing high mortality rates. An increasing number of studies have reported on forest declines and vegetation shifts triggered by drought. ![]()
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