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1. Phosphorus chemistry in plant charcoal: interplay between biomass composition and thermal condition

   https://doi.org/10.1071/WF23096  

   Wu, Yudi ; Pae, Lois M ; Huang, Rixiang ( January 2024 , International Journal of Wildland Fire)

   Background Vegetation fire may change Phosphorus (P) cycling in terrestrial ecosystems through converting biomass into fire residues. Aim The aim of this study was to understand the chemistry and mobility of P in fire residues to help reveal P thermochemistry during biomass burning and post-fire P cycling. Methods A combination of sequential extraction, liquid 31P NMR and P K-edge XANES was used to obtain quantitative P speciation and explain P solubilisation behaviours of charcoal. Key results Despite varying diverse P species existing in raw biomass, only two P structural moieties – orthophosphate and pyrophosphate – were identified in charcoal. However, relative abundance of pyrophosphate differs greatly among charcoal samples from different biomass types, ranging between 0 and 40% of total extractable P. Although P K-edge XANES data indicates abundant soluble phosphate minerals, most P (70–90%) is likely occluded physically in the charcoal. The bicarbonate-extractable P (the Olsen-P) varies significantly and cannot be explained by surface P concentration or elemental stoichiometry alone. Conclusion and implications The results suggest the importance of starting biomass P speciation (i.e. molecular structure and complexation environment) and thermal conditions in controlling P speciation and availability in charcoal. The different P chemistry between charcoal and ash suggests the importance of fire types and severity in disturbing the P cycle.

    

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2. Imbalance of global nutrient cycles exacerbated by the greater retention of phosphorus over nitrogen in lakes

   https://doi.org/10.1038/s41561-022-00958-7  

   Wu, Zhen ; Li, Jincheng ; Sun, Yanxin ; Peñuelas, Josep ; Huang, Jilin ; Sardans, Jordi ; Jiang, Qingsong ; Finlay, Jacques C. ; Britten, Gregory L. ; Follows, Michael J. ; et al ( June 2022 , Nature Geoscience)

   Imbalanced anthropogenic inputs of nitrogen (N) and phosphorus (P) have significantly increased the ratio between N and P globally, degrading ecosystem productivity and environmental quality. Lakes represent a large global nutrient sink, modifying the flow of N and P in the environment. It remains unknown, however, the relative retention of these two nutrients in global lakes and their role in the imbalance of the nutrient cycles. Here we compare the ratio between P and N in inflows and outflows of more than 5,000 lakes globally using a combination of nutrient budget model and generalized linear model. We show that over 80% of global lakes positively retain both N and P, and almost 90% of the lakes show preferential retention of P. The greater retention of P over N leads to a strong elevation in the ratios between N and P in the lake outflow, exacerbating the imbalance of N and P cycles unexpectedly and potentially leading to biodiversity losses within lakes and algal blooms in downstream N-limited coastal zones. The management of N or P in controlling lake eutrophication has long been debated. Our results suggest that eutrophication management that prioritizes the reduction of P in lakes—which causes a further decrease in P in outflows—may unintentionally aggravate N/P imbalances in global ecosystems. Our results also highlight the importance of nutrient retention stoichiometry in global lake management to benefit watershed and regional biogeochemical cycles. 

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3. High species richness in the lichen genus Peltigera (Ascomycota, Lecanoromycetes): 34 species in the dolichorhizoid and scabrosoid clades of section Polydactylon, including 24 new to science

   https://doi.org/10.3767/persoonia.2023.51.01  

   Magain, N. ; Miadlikowska, J. ; Goffinet, B. ; Goward, T. ; Pardo-De la Hoz, C.J. ; Jüriado, I. ; Simon, A. ; Mercado-Díaz, J.A. ; Barlow, T. ; Moncada, B. ; et al ( August 2023 , Persoonia - Molecular Phylogeny and Evolution of Fungi)

   Applying molecular methods to fungi establishing lichenized associations with green algae or cyanobacteria has repeatedly revealed the existence of numerous phylogenetic taxa overlooked by classical taxonomic approaches. Here, we report taxonomical conclusions based on multiple species delimitation and validation analyses performed on an eight-locus dataset that includes world-wide representatives of the dolichorhizoid and scabrosoid clades in section Polydactylon of the genus Peltigera . Following the recommendations resulting from a consensus species delimitation approach and additional species validation analysis (BPP) performed in this study, we present a total of 25 species in the dolichorhizoid clade and nine in the scabrosoid clade, including respectively 18 and six species that are new to science and formally described. Additionally, one combination and three varieties (including two new to science) are proposed in the dolichorhizoid clade. The following 24 new species are described: P. appalachiensis , P. asiatica , P. borealis , P. borinquensis , P. chabanenkoae , P. clathrata , P. elixii , P. esslingeri , P. flabellae , P. gallowayi , P. hawaiiensis , P. holtanhartwigii , P. itatiaiae , P. hokkaidoensis , P. kukwae , P. massonii , P. mikado , P. nigriventris , P. orientalis , P. rangiferina , P. sipmanii , P. stanleyensis , P. vitikainenii and P. willdenowii ; the following new varieties are introduced: P. kukwae var. phyllidiata and P. truculenta var. austroscabrosa ; and the following new combination is introduced: P. hymenina var. dissecta . Each species from the dolichorhizoid and scabrosoid clades is morphologically and chemically described, illustrated, and characterised with ITS sequences. Identification keys are provided for the main biogeographic regions where species from the two clades occur. Morphological and chemical characters that are commonly used for species identification in the genus Peltigera cannot be applied to unambiguously recognise most molecularly circumscribed species, due to high variation of thalli formed by individuals within a fungal species, including the presence of distinct morphs in some cases, or low interspecific variation in others. The four commonly recognised morphospecies: P. dolichorhiza , P. neopolydactyla , P. pulverulenta and P. scabrosa in the dolichorhizoid and scabrosoid clades represent species complexes spread across multiple and often phylogenetically distantly related lineages. Geographic origin of specimens is often helpful for species recognition; however, ITS sequences are frequently required for a reliable identification. 

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4. Aeolian dust deposition and the perturbation of phosphorus transformations during long-term ecosystem development in a cool, semi-arid environment

   https://doi.org/https://doi.org/10.1016/j.gca.2018.12.017  

   Gu, Chunhao ; Hart, Stephen C. ; Turner, Benjamin L. ; Hu, Yongfeng ; Meng, Yong ; Zhu, Mengqiang ( February 2019 , Geochimica et cosmochimica acta)

   Aeolian dust deposition is an important phosphorus (P) input to terrestrial ecosystems, but its influence on P dynamics during long-term ecosystem development remains poorly understood. In this study, we characterized P speciation using P K-edge XANES spectroscopy in surface soils (0–15 cm, A horizon) and contemporary aeolian dust collected at each site of a 3000-ky volcanic soil chronosequence in a cool, semi-arid environment. Phosphorus speciation in dust was dominated by calcium-bound P (Ca-P; 54–74%), with 11–23% iron and aluminum-bound P [(Fe + Al)-P] and 7–25% organic P (Po). In soils, Po contributed 1–23% of total P, being greater in older soils; however, the proportions of Ca-P (16–39%) and (Fe + Al)-P (48–82%) fluctuated with increasing weathering over the soil chronosequence. These soil fluctuations resulted from the accumulation and preservation of alkaline aeolian dust during pedogenesis in the semi-arid climate, which significantly increased soil Ca-P while decreasing the total amounts and relative abundances of soil (Fe + Al)-P. We suggest that the effects of an aeolian dust input on soil P transformations are functions of the relative magnitude and chemical composition of the dust input and the soil weathering intensity. For a given source of dust, when the net dust flux is greater than the weathering rate, dust accumulates and thus alters the pattern of P transformations during pedogenesis; otherwise, the dust influence on soil P transformations is negligible. By accurately identifying the chemical nature of P pools, our work highlights the advantage of P K-edge XANES spectroscopy over chemical extractions in examining soil P dynamics, and demonstrates how dust inputs can modify the Walker and Syers model of pedogenic P transformations in semi-arid environments. Overall, this work provides a foundation for understanding how dust influences P cycling during soil and ecosystem development, and indicates that dust inputs and composition, and the soil weathering rate, all must be considered for developing integrated climate-biogeochemical models with predictive power in terrestrial ecosystems. 

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5. Aeolian dust deposition and the perturbation of phosphorus transformations during long-term ecosystem development in a cool, semi-arid environment

   https://doi.org/doi.org/10.1016/j.gca.2018.12.017  

   Gu, Chunhao ; Hart, Stephen C. ; Turner, Benjamin L. ; Hu, Yongfeng ; Meng, Yong ; Zhu, Mengqiang ( February 2019 , Geochimica et cosmochimica acta)

   Aeolian dust deposition is an important phosphorus (P) input to terrestrial ecosystems, but its influence on P dynamics during long-term ecosystem development remains poorly understood. In this study, we characterized P speciation using P K-edge XANES spectroscopy in surface soils (0–15 cm, A horizon) and contemporary aeolian dust collected at each site of a 3000-ky volcanic soil chronosequence in a cool, semi-arid environment. Phosphorus speciation in dust was dominated by calcium-bound P (Ca-P; 54–74%), with 11–23% iron and aluminum-bound P [(Fe + Al)-P] and 7–25% organic P (Po). In soils, Po contributed 1–23% of total P, being greater in older soils; however, the proportions of Ca-P (16–39%) and (Fe + Al)-P (48–82%) fluctuated with increasing weathering over the soil chronosequence. These soil fluctuations resulted from the accumulation and preservation of alkaline aeolian dust during pedogenesis in the semi-arid climate, which significantly increased soil Ca-P while decreasing the total amounts and relative abundances of soil (Fe + Al)-P. We suggest that the effects of an aeolian dust input on soil P transformations are functions of the relative magnitude and chemical composition of the dust input and the soil weathering intensity. For a given source of dust, when the net dust flux is greater than the weathering rate, dust accumulates and thus alters the pattern of P transformations during pedogenesis; otherwise, the dust influence on soil P transformations is negligible. By accurately identifying the chemical nature of P pools, our work highlights the advantage of P K-edge XANES spectroscopy over chemical extractions in examining soil P dynamics, and demonstrates how dust inputs can modify the Walker and Syers model of pedogenic P transformations in semi-arid environments. Overall, this work provides a foundation for understanding how dust influences P cycling during soil and ecosystem development, and indicates that dust inputs and composition, and the soil weathering rate, all must be considered for developing integrated climate-biogeochemical models with predictive power in terrestrial ecosystems. 

   more » « less