Abstract
In the Pyrenees low temperature and scarce precipitation limit radial growth at treeline. The climatic drivers of treeline formation in mid-latitude mountains are temperature and also moisture variability. Alpine treelines are often induced by a threshold of minimum temperatures above which tree growth is generally not possible anymore. However, this worldwide pattern may not account for more drought-prone mountains, where changes in precipitation can also affect ecosystem functioning and productivity at higher elevations. Here, we aim to determine if tree-ring formation in ecotones along the Pyrenees indeed primarily depends on temperature means or also reflects hydroclimatic changes. The mean duration of the growing season at Pyrenean treelines was 177 days, lasting from mid-May to early November, which corresponds to a mean root-zone temperature of 8.2 °C. Temperatures during the early and late growing season were most critical for mountain pine growth at highest elevations, and above average spring temperatures also contributed to radial enlargement of tracheids. Sites showing more similar soil temperatures also presented more similar long-term growth trends indicating that local conditions trace regional influences on growth. Nevertheless, more wet conditions in summer enhanced growth at treelines subjected to more Mediterranean influence and therefore having a higher summer water deficit. A broader perspective reveals that soil moisture availability during spring and summer, however, also influence ring width formation at other treelines located in mid-latitude mountains separating temperate and semi-arid biomes. Our results suggest re-evaluating the idea of purely temperature-limited treelines, especially in mid-latitude mountains that experience moisture seasonality or where precipitation decreases with increasing elevation.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.