Global change and arctic ecosystems: is lichen decline a function of increases in vascular plant biomass?

Abstract

Summary 1Macrolichens are important for the functioning and biodiversity of cold northern ecosystems and their reindeer-based cultures and economies. 2 We hypothesized that, in climatically milder parts of the Arctic, where ecosystems have relatively dense plant canopies, climate warming and/or increased nutrient availability leads to decline in macrolichen abundance as a function of increased abundance of vascular plants. In more open high-arctic or arctic-alpine plant communities such a relationship should be absent. To test this, we synthesized cross-continental arctic vegetation data from ecosystem manipulation experiments simulating mostly warming and increased nutrient availability, and compared these with similar data from natural environmental gradients. 3 Regressions between abundance or biomass of macrolichens and vascular plants were consistently negative across the subarctic and mid-arctic experimental studies. Such a pattern did not emerge in the coldest high-arctic or arctic-alpine sites. The slopes of the negative regressions increased across 10 sites as the climate became milder (as indicated by a simple climatic index) or the vegetation denser (greater site above-ground biomass). 4 Seven natural vegetation gradients in the lower-altitude sub-and mid-arctic zone confirmed the patterns seen in the experimental studies, showing consistent negative relationships between abundance of macrolichens and vascular plants. 5 We conclude that the data supported the hypothesis. Macrolichens in climatically milder arctic ecosystems may decline if and where global changes cause vascular plants to increase in abundance. 6 However, a refining of our findings is needed, for instance by integrating other abiotic and biotic effects such as reindeer grazing feedback on the balance between vascular plants and lichens.

Four Decades of Plant Community Change in the Alpine Tundra of Southwest Yukon, Canada

“…The greatest observed change was on the southwest aspect where moss increased and lichens and Dryas octopetala declined significantly in relative importance. This pattern was consistent with observations reported by Hudson and Henry (2009) who reported a shift toward increasing bryophyte dominance and a decrease in lichens at Alexandria Fiord, Nunavut, and those of Cornelissen et al (2001) who documented a decline in lichen abundance at several Arctic and alpine sites. In the latter case, this change was hypothesized to be a response to increases in the abundance of vascular plants.…”

Alien species in a warmer world: risks and opportunities

“…Such species appear to have responded to the changed climatic conditions of the recent past, which enabled them to reproduce and establish in the presence of resident species. Simultaneously, native species have also exhibited marked natural poleward movements from warmer regions, sometimes at the expense of local resident species that are adapted to colder climates [56][57][58][59]. For example, the annual numbers of migratory lepidopteran species in southern Britain are increasing, and are linked to positive temperature anomalies in spring and summer.…”

Nitrogen deposition and soil carbon content affect nitrogen mineralization during primary succession in acid inland drift sand vegetation

“…In Campylopus introflexus dominated vegetations, however, but also in lichen-dominated vegetation, an ectorganic layer is formed by the basal part of the mat-forming acrocarpous moss plant. As bryophytes and lichens have no root system, the ectorganic layer could provide a substrate for mineralization and interception of atmospheric deposition, which is readily available for the upper living part of the plant (Cornelissen et al 2001;Crittenden 1991;Sipman 1978).…”