A Recent and Distinct Pine (Pinus sylvestris L.) Reproduction Upsurge at the Treeline in the Swedish Scandes

Abstract

Demographic monitoring of Pinus sylvestris in the treeline ecotone of the southern Swedish Scandes, has been conducted in permanent plots since 1973. Prior reports of the population evolution were published by the present author 1993, 2007, 2014a. Here, results from the most recent survey period, 2013 to 2018, are presented and analyzed. This particular interval stands out with an unprecedented reproductive upswing, relative to the situation prevailing for some decades prior to 1995. Accordingly, the incidence of winter desiccation injury to needles/shoots and associated individual mortality has decreased. In addition seed viability increased significantly after about year 2000. Apparently, treeline performance of Pinus sylvestris is tightly related to air and ground temperatures, during both summer and winter. The obtained results are relevant the in the context of a hypothetical novel biogeographic zonation pattern, lending relevance to a notion that Pinus sylvestris may gradually increase its prominence as a treeline species in a potentially warmer future.