Determinants of cryptogam composition and diversity in Sphagnum-dominated peatlands: the importance of temporal, spatial and functional scales

• Published in: The Journal of ecology Vol. 97; no. 2; pp. 299 - 310
• Main Authors: Lang, Simone I, Cornelissen, Johannes H.C, Hölzer, Adam, ter Braak, Cajo J.F, Ahrens, Matthias, Callaghan, Terry V, Aerts, Rien
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.03.2009; Blackwell Publishing; Blackwell Publishing Ltd; Blackwell
• Subjects: alaskan arctic tundra; Animal and plant ecology; Animal, plant and microbial ecology; Biodiversity; Biological and medical sciences; bryophyte; Bryophytes; Bryopsida; Climate change; Climatology. Bioclimatology. Climate change; community structure; Correlation analysis; Cryptogams; Earth, ocean, space; Exact sciences and technology; External geophysics; Flowers & plants; functional type; Fundamental and applied biological sciences. Psychology; General aspects; global change; gradient; Human ecology; hylocomium-splendens; lichen; Lichens; Liverworts; Meteorology; Multivariate analysis; nutrient availability; peatland; Peatlands; physical gradients; Plant populations; Plant-Climate Interactions and Ecophysiology; Plants; response surfaces; scale; simulated environmental-change; species composition; Sphagnum; Subarctic; vascular plant; Vascular plants; Vegetation; warming experiment; western canada; Norway; Sweden; Warming; Composition; bryophyte; Diversity; gradient; peatland; Bryophyta; scale; lichen; Subarctic; Pteridophyta; warming experiment; Sphagnobrya; Peat bog; Sphagnum; functional type; Dynamical climatology; Fungi; vascular plant; Climate change; Lichenes; Spermatophyta
• ISSN: 0022-0477; 1365-2745
• DOI: 10.1111/j.1365-2745.2008.01472.x

1. Changing temperature regimes and precipitation patterns in the Subarctic will impact on vegetation composition and diversity including those of bryophyte and lichen communities, which are major drivers of high-latitude carbon and nutrient cycling and hydrology. 2. We investigated the relative importance of such impacts at different temporal, spatial and plant functional scales in subarctic Sphagnum fuscum-dominated peatlands, comprising both an in situ warming experiment and natural climatic and topographic gradients in northern Sweden and Norway. We applied multivariate analyses to investigate the relationships among cryptogam and vascular plant species composition and abiotic (temperature, moisture) and biotic (Sphagnum growth) regimes at various scales. 3. At the short-term temporal scale (4-year warming experiment), increased temperature yielded no clear effect on cryptogam or vascular plant species composition. Spatially, direct effects of temperature were decisive for overall species composition across regions (macro-scale) rather than within one region (meso-scale). Moisture and Sphagnum growth were drivers of species composition at all spatial scales, and Sphagnum growth itself depended on its position on the microtopographic gradient and on temperature. 4. Grouping of bryophytes and lichens at increasing scales of functional aggregation from species, growth form to the major higher taxon level (Sphagnum, other mosses, liverworts, lichens) revealed mostly increasing correlation with climate regimes and Sphagnum growth. Excluding liverworts from the analysis tended to reduce the correlation. 5. Abundances of lichens, liverworts, non-Sphagnum mosses and (to a lesser degree) vascular plants were negatively related to Sphagnum abundance. Few cryptogam and vascular plant species showed a positive relationship with Sphagnum abundance. Correspondingly, cryptogam species richness and Shannon Index on peatlands strongly declined as Sphagnum abundance increased, while indices for vascular plants showed no significant relationship. 6. Synthesis. Scale, be it spatial or functional, strongly determined which environmental drivers showed the clearest relationships with vegetation composition and diversity. Our findings will help to optimize predictions about long-term effects of climate on peatland vegetation composition, and subsequently its feedbacks to carbon and water cycles, at the regional scale.