Drivers of treeline shift in different European mountains

Abstract

A growing body of evidence suggests that processes of upward treeline expansion and shifts in vegetation zones may occur in response to climate change. However, such shifts can be limited by a variety of non-climatic factors, such as nutrient availability, soil conditions, landscape fragmentation and some species-specific traits. Many changes in species distributions have been observed, although no evidence of complete community replacement has been registered yet. Climatic signals are often confounded with the effects of human activity, for example, forest encroachment at the treeline owing to the coupled effect of climate change and highland pasture abandonment. Data on the treeline ecotone, barriers to the expected treeline or dominant tree species shifts due to climate and land use change, and their possible impacts on biodiversity in 11 mountain areas of interest, from Italy to Norway and from Spain to Bulgaria, are reported. We investigated the role of environmental conditions on treeline ecotone features with a focus on treeline shift. The results showed that treeline altitude and the altitudinal width of the treeline ecotone, as well as the significance of climatic and soil parameters as barriers against tree species shift, significantly decreased with increasing latitude. However, the largest part of the commonly observed variability in mountain vegetation near the treeline in Europe seems to be caused by geomorphological, geological, pedological and microclimatic variability in combination with different land use history and present socio-economic relations.

Sensitivity to environmental change of the treeline ecotone and its associated biodiversity in European mountains

“…This is also indicated in reports from the present SENSFOR study (Sarkki et al 2016, Cudlín et al 2017, Kyriazopoulos et al 2017.…”

“…3). These pasture management methods Lowland species, including anthropocores, brought to the treeline ecotone areas by these cultivation practices might cause an anomalous increase in species diversity in an area, at least locally and for a short period (Cudlín et al 2017). However, these non-alpine species could linger in the area and become invasive in future favorable environmental conditions (Crooks & Soulé 1999).…”

“…However, the change in reflectance caused by vegetation is a slow process, as the rate of forest migration is low due to the multitude of interacting and counteracting abiotic and biotic environmental factors. The typical advance rate for the warming periods since the late 19th century has been less than 1 m yr −1 altitudinally (Kullman & Öberg 2009, Kharuk et al 2010, Mathisen et al 2014, Cudlín et al 2017) and some 10s m yr −1 latitudinally (Hofgaard et al 2013). These empirically based rate estimates represents less than onetenth of model-based rate estimates (Hofgaard et al 2013), and it is essential to consider this mismatch when discussing magnitude and time frame of potential threats to alpine biodiversity.…”

“…Biodiversity Norway. Photography by A. Hofgaard may increase at the early stages of recolonization of former alpine pasture (Strebel & Bühler 2015, Cudlín et al 2017), but then decrease at later stages due to growing tree and shrub populations outcompeting alpine pasture species (Holtmeier & Broll 2017) (Fig. 5).…”

Assessment and mapping the dynamics of soil properties in selected forest stands from the region of Central Balkan National Park in the context of ecosystem services

“…In landscape-ecological terms, the area is characterised by rich forest biodiversity dominated by broad-leaved forests of Querqus cerris, Querqus frainetto, Fagus sylvatica and mixed forest patches with Pinus sylvestris (Cudlín et al 2017). About 70% of the ecosystems are natural.…”