Letter to H.B. Stenzel from E.R. Eller on 1947-02-03

Jackson School of Geoscience

Nitrogen concentration and physical properties are key drivers of woody tissue respiration

Background and Aims: Despite the critical role of woody tissues in determining net carbon exchange of terrestrial ecosystems, relatively little is known regarding the drivers of sapwood and bark respiration. Methods: Using one of the most comprehensive wood respiration datasets to date (82 species from Australian rainforest, savanna and temperate forest), we quantified relationships between tissue respiration rates (Rd) measured in vitro (i.e. ‘respiration potential’) and physical properties of bark and sapwood, and nitrogen concentration (Nmass) of leaves, sapwood and bark. Key Results: Across all sites, tissue density and thickness explained similar, and in some cases more, variation in bark and sapwood Rd than did Nmass. Higher density bark and sapwood tissues had lower Rd for a given Nmass than lower density tissues. Rd–Nmass slopes were less steep in thicker compared with thinner-barked species and less steep in sapwood than in bark. Including the interactive effects of Nmass, density and thickness significantly increased the explanatory power for bark and sapwood respiration in branches. Among these models, Nmass contributed more to explanatory power in trunks than in branches, and in sapwood than in bark. Our findings were largely consistent across sites, which varied in their climate, soils and dominant vegetation type, suggesting generality in the observed trait relationships. Compared with a global compilation of leaf, stem and root data, Australian species showed generally lower Rd and Nmass, and less steep Rd–Nmass relationships. Conclusions: To the best of our knowledge, this is the first study to report control of respiration–nitrogen relationships by physical properties of tissues, and one of few to report respiration–nitrogen relationships in bark and sapwood. Together, our findings indicate a potential path towards improving current estimates of autotrophic respiration by integrating variation across distinct plant tissues

Ordovician polychaeturid polychaetes: Taxonomy, distribution and palaeoecology

The fossil polyclinic family Polychaeturidae is considered as monogeneric and comprises four species of the genus Pteropelta. Pteropelta, originally established on isolated scolecodonts (the carriers), is revised and the apparatus-based Polychaetura is shown to be a junior synonym of Pteropelta. In addition to Pteropelta gladiata and Pteropelta kielanae. Pteropelta huberti sp. nov., and Pteropelta sp. A are herein described from the Upper Ordovician of Estonia and Sweden. Polychaeturids include some of the most common and characteristic scolecodont-bearing polychaetes in the Ordovician of Baltoscandia. They first appeared in the early Darriwilian (Mid Ordovician), flourished in the Late Ordovician and disappeared in the early Silurian. The distribution patterns of individual polychaeturid species infer regional biostratigraphical potential. Polychaeturids were geographically widespread during the Ordovician and have been recorded from at least three palaeocontinents

An atypical intra-platform environment and biota from the Silurian of Gotland, Sweden

A condensed shale from the middle Silurian of Gotland (Sweden) is herein described with regard to its biotic and environmental significance. The fauna is characterised by an overall low diversity and anomalous abundance patterns, notably a mass-occurrence of scolecodonts. Other elements include abundant chitinozoans, dendroid and graptoloid graptolites, conodonts, eurypterids, and the brachiopod Lingula. An unusually good collection of the rare, minute conodont Aldridgeodus minimus gen. et sp. nov., was recovered and is therefore formally described herein. The conspicuous faunal composition and palaeogeographical position of the shale in the interior area of a carbonate platform is unique for any stratum of Gotland and may represent a rarely preserved environment for the lower Palaeozoic