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

Abstract

Summary 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.

Growth responses of Sphagnum hollows to a growing season lengthening manipulation in Alaskan Arctic tundra

“…This result is consistent with the absence of a significant interaction between treatment and DOY for SGR (Table 3). In both treated and untreated plots, Sphagnum growth was stimulated by elevated soil temperatures and dry conditions, a result that has been documented previously (Skre and Oechel 1981;Sonesson et al 2002;Dorrepaal et al 2004Dorrepaal et al , 2006Gunnarsson 2005;Breeuwer et al 2008;Lang et al 2009). However, we did not see a significant difference in soil moisture between treatments.…”

“…Whereas most existing studies have examined the relationships between growth and climate on an annual time scale and/or have substituted space for time by comparing different sites (i.e., Backeus 1988;Callaghan et al 1997;Gunnarsson 2005;Lang et al 2009), we conducted, to our knowledge, the first multi-year analysis on a seasonal time scale at the same site. Lang et al (2009) demonstrated that spatial and temporal scales strongly determined which environmental drivers correlated most with vegetation composition and diversity.…”

“…Lang et al (2009) demonstrated that spatial and temporal scales strongly determined which environmental drivers correlated most with vegetation composition and diversity. In that study, only meso-environmental controls of growth were considered on plots located on comparable microsites.…”

Cephalozia macrostachyaKaal. indicateur de l'état de conservation d'une tourbière en Sologne (Cher, France); son utilité dans la problématique de gestion

“…La relative rareté de l'espè-ce sur sphaignes dynamiques, localement en Sologne ou dans l'ensemble de l'aire nationale de l'espèce, trouve vraisemblablement son origine dans les effets allélopathiques exercés par les sphaignes (Duckett & Clymo, 1988) ainsi que dans des effets de compéti-tion pour les ressources. De façon paradoxale, les tourbières où les sphaignes présentent une croissance soutenue sont plus pauvres en microhépatiques que celles où celles-ci sont moins dynamiques (Lang et al, 2009). Les perturbations modérées favorisent donc les microhépatiques au détriment des sphaignes, qui, dans certaines situations, ne laissent pratiquement aucun espace pour la colonisation d'autres bryophytes.…”

Bryophytes and lichens in peatlands and <em>Tepualia stipularis</em> swamp forests of Isla Grande de Chiloé (Chile)

“…Due to wetness levels and the often meager vascular plant cover, peatlands bring favorable conditions to bryophytes and contribute to a large extent to the diversity of moss and liverwort species, particularly in regions where peatlands are abundant (Minayeva, 2008). Also, in the Northern Hemisphere, the role of peatlands in the upkeep of lichenic diversity is very important (Lang & al., 2009). Nevertheless, Minayeva (2008) reported that the species number of lichens present is quite low compared to the non-peatland lichen flora for any given region.…”