Growth responses of Pleurozium schreberi to temperature and precipitation : A comparison of natural and artificial markers

Sammanfattning

Feathermosses play an important role in carbon cycling in boreal and subarctic ecosystems, and their growth is influenced by climatic variables such as precipitation and temperature. Reliable methods for measuring growth of feathermosses remain limited, and artificial marker methods may underestimate growth. This study investigated the relationship between vertical growth of Pleurozium schreberi and variations in precipitation and temperature under subarctic conditions, while also evaluating whether natural markers can be used as an alternative to artificial markers. In 2011–2014 and 2018, vertical growth was measured with artificial wire markers at eight sites along a precipitation gradient in the Torneträsk catchment area, Sweden. Annual growth was compared with precipitation and temperature data, and between ‘wet’ and ‘dry’ sites. Natural marker measurements were performed on shoots from three selected sites by measuring internode lengths of branches, buds and scars, which were then used to estimate annual growth. Regression analyses of wire-based measurements indicated a positive trend between precipitation and growth, but no relationship between growth and temperature. Neither did growth between ‘wet’ and ‘dry’ sites differ significantly. Mean internode lengths from natural markers were generally longer at ‘wet’ sites, and two sites differed significantly when only branch internodes were included. However, annual growth estimates reconstructed from internode patterns did not correspond to either climate variables or wire-based measurements. The results suggest that precipitation potentially influences vertical growth of P. schreberi more than temperature. The natural marker method explored did not provide reliable annual growth estimates, but further development is possible.