The terminal Paleozoic fungal event: evidence of terrestrial ecosystem destabilization and collapse.

Abstract

Because of its prominent role in global biomass storage, land vegetation is the most obvious biota to be investigated for records of dramatic ecologic crisis in Earth history. There is accumulating evidence that, throughout the world, sedimentary organic matter preserved in latest Permian deposits is characterized by unparalleled abundances of fungal remains, irrespective of depositional environment (marine, lacustrine, fluviatile), floral provinciality, and climatic zonation. This fungal event can be considered to reflect excessive dieback of arboreous vegetation, effecting destabilization and subsequent collapse of terrestrial ecosystems with concomitant loss of standing biomass. Such a scenario is in harmony with predictions that the Permian-Triassic ecologic crisis was triggered by the effects of severe changes in atmospheric chemistry arising from the rapid eruption of the Siberian Traps flood basalts.

Extinction and recovery patterns of the vegetation across the Cretaceous–Palaeogene boundary — a tool for unravelling the causes of the end-Permian mass-extinction

“…Disparate studies have reported abundant fungal remains at the Permian-Triassic boundary in both marine and terrestrial successions (Eshet et al, 1995;Retallack, 1995;Utting and Piasecki, 1995;Visscher et al, 1996;Looy et al, 2001;Steiner et al, 2003; Table 2). However, some workers regard these fossils (Reduviasporonites and its synonyms) as algal affiliates based on morphological and biochemical characteristics (Afonin et al, 2001;Foster et al, 2002).…”

“…Whether Reduviasporonites represents a fungus or alga, its great abundance coincident with global decline of dominant woody plants, suggests that it favoured aberrant environmental conditions (reduced herbivory/competition or conditions favourable to saprotrophism). If Reduviasporonites is a fungus (saprotroph), then its global success and the decline of woody plants may have been favoured by a dramatic spike in atmospheric CO 2 , acidification, reduced insolation, or ozone depletion (Visscher et al, 1996). None of these environmental scenarios is yet strongly supported by independent evidence although high CO 2 emissions might be expected from the eruption of the Siberian flood basalts and from the oxidation of methane hydrates released from continental shelf areas (Benton and Twitchett, 2003).…”

Life in the end-Permian dead zone

“…The low spore͞pollen ratio confirms a limited role of herbaceous lycopsids and ferns. Although underrepresented in the percentage diagram, the consistent presence of fungal remains (Reduviasporonites) points to excessive decomposition of woody plant tissue (29,30) and͞or pathogenic fungal infection (14). Parallel to the disappearance of marine invertebrate macrofauna, palynological data at the top of the Schuchert Dal Formation indicate a conspicuous dominance decline among woody plants (Fig.…”

“…In conjunction with the end-Permian ecological crisis, extinction among dominant gymnosperms appears to be a global event that dramatically affected terrestrial ecosystems. Justified by worldwide changes in vegetation structure and soil characteristics, as well as by strongly increased fungal activity, dieback of woody vegetation caused an unparalleled loss of standing biomass irrespective of floral provinciality and climatic zonation (29)(30)(31)(32)(33)(34). However, because of the condensed or otherwise incomplete nature of most end-Permian palynological records, vegetation development at the climax of ecological crisis could be inferred only in very general terms.…”

The Siberian Traps and the End-Permian mass extinction: a critical review

“…This is testable, because we would anticipate (a) greater effects in Northern Hemisphere ecosystems (where the volcanism occurred); (b) that if the control is primarily light occlusion, then the effects may be greater in the polar and near-polar regions, and upon marine plant species; (c) that if the control is primarily temperature reduction, this may affect tropical and subtropical terrestrial plant species to a greater extent. Either way, we would expect a progressive reduction in the range of plant types; the worst case scenario may be the wholesale destruction of plant systems, and their temporary replacement by non-photosynthetic ecosystems and the production of the characteristic 'fungal spike' [95] . The recovery of these systems after individual eruptions would depend on the survival of plants in refugios, and the viability of seeds, spores and root systems.…”