title: Summer dry-down modulates the isotopic composition of soil CO2 production in snow-dominated landscapes

authors: Riveros-Iregui, Diego A.

abstract: In mountainous landscapes, soil moisture is highly dynamic due to the effects of topography and the temporal variability imposed by seasonal precipitation, including rainfall and snow. Soil moisture is known to affect ecosystem carbon exchange both aboveground and belowground, as well as the stable isotopic composition of exchanged CO 2 . In this study we used an extensive suite of measurements to examine the effects of seasonal changes in soil moisture on the isotopic composition of soil CO 2 production at the landscape level. We show that the seasonal decline in soil moisture (i.e., summer dry-down) appeared to impose a trend in the δ 13 C of soil CO 2 production (δ P ) with more negative δ P early in the growing season when soils were wet, and more positive δ P as the growing season progressed and soils dried out. This seemingly generalizable pattern for a snow-dominated watershed is likely to represent the variability of recently assimilated C, tracked through the plant-soil system and imprinted in the respired CO 2 . Thus, our observations suggest that, at least for mountainous environments, seasonal changes in δ P are largely mediated by soil moisture and their spatial variability is partially organized by topography.

text: Summer dry-down modulates the isotopic composition of soil CO2 production in snow-dominated landscapes In mountainous landscapes, soil moisture is highly dynamic due to the effects of topography and the temporal variability imposed by seasonal precipitation, including rainfall and snow. Soil moisture is known to affect ecosystem carbon exchange both aboveground and belowground, as well as the stable isotopic composition of exchanged CO 2 . In this study we used an extensive suite of measurements to examine the effects of seasonal changes in soil moisture on the isotopic composition of soil CO 2 production at the landscape level. We show that the seasonal decline in soil moisture (i.e., summer dry-down) appeared to impose a trend in the δ 13 C of soil CO 2 production (δ P ) with more negative δ P early in the growing season when soils were wet, and more positive δ P as the growing season progressed and soils dried out. This seemingly generalizable pattern for a snow-dominated watershed is likely to represent the variability of recently assimilated C, tracked through the plant-soil system and imprinted in the respired CO 2 . Thus, our observations suggest that, at least for mountainous environments, seasonal changes in δ P are largely mediated by soil moisture and their spatial variability is partially organized by topography.

year: 2018

title: Crystal structure of an inferred ancestral bacterial pyruvate decarboxylase

authors: Buddrus, Lisa

subjects: Science & Technology

abstract: Pyruvate decarboxylase (PDC; EC 4.1.1.1) is a key enzyme in homofermentative metabolism where ethanol is the major product. PDCs are thiamine pyrophos­phate- and Mg2+ ion-dependent enzymes that catalyse the non-oxidative decarboxylation of pyruvate to acetaldehyde and carbon dioxide. As this enzyme class is rare in bacteria, current knowledge of bacterial PDCs is extremely limited. One approach to further the understanding of bacterial PDCs is to exploit the diversity provided by evolution. Ancestral sequence reconstruction (ASR) is a method of computational molecular evolution to infer extinct ancestral protein sequences, which can then be synthesized and experimentally characterized. Through ASR a novel PDC was generated, designated ANC27, that shares only 78% amino-acid sequence identity with its closest extant homologue (Komagataeibacter medellinensis PDC, GenBank accession No. WP_014105323.1), yet is fully functional. Crystals of this PDC diffracted to 3.5 Å resolution. The data were merged in space group P3221, with unit-cell parameters a = b = 108.33, c = 322.65 Å, and contained two dimers (two tetramer halves) in the asymmetric unit. The structure was solved by molecular replacement using PDB entry 2wvg as a model, and the final R values were Rwork = 0.246 (0.3671 in the highest resolution bin) and Rfree = 0.319 (0.4482 in the highest resolution bin). Comparison with extant bacterial PDCs supports the previously observed correlation between decreased tetramer interface area (and number of interactions) and decreased thermostability.

text: Crystal structure of an inferred ancestral bacterial pyruvate decarboxylase Pyruvate decarboxylase (PDC; EC 4.1.1.1) is a key enzyme in homofermentative metabolism where ethanol is the major product. PDCs are thiamine pyrophos­phate- and Mg2+ ion-dependent enzymes that catalyse the non-oxidative decarboxylation of pyruvate to acetaldehyde and carbon dioxide. As this enzyme class is rare in bacteria, current knowledge of bacterial PDCs is extremely limited. One approach to further the understanding of bacterial PDCs is to exploit the diversity provided by evolution. Ancestral sequence reconstruction (ASR) is a method of computational molecular evolution to infer extinct ancestral protein sequences, which can then be synthesized and experimentally characterized. Through ASR a novel PDC was generated, designated ANC27, that shares only 78% amino-acid sequence identity with its closest extant homologue (Komagataeibacter medellinensis PDC, GenBank accession No. WP_014105323.1), yet is fully functional. Crystals of this PDC diffracted to 3.5 Å resolution. The data were merged in space group P3221, with unit-cell parameters a = b = 108.33, c = 322.65 Å, and contained two dimers (two tetramer halves) in the asymmetric unit. The structure was solved by molecular replacement using PDB entry 2wvg as a model, and the final R values were Rwork = 0.246 (0.3671 in the highest resolution bin) and Rfree = 0.319 (0.4482 in the highest resolution bin). Comparison with extant bacterial PDCs supports the previously observed correlation between decreased tetramer interface area (and number of interactions) and decreased thermostability.

year: 2018

title: Te Kāhui a Kiwa—Advancing Indigenous self determination and wellbeing through trade and can the CPTPP help

authors: Mika, Jason

abstract: This report provides an interim account of a conference held in Hamilton on 28-29 June 2023 called Te Kāhui a Kiwa—Advancing Indigenous self-determination and wellbeing through trade and can the CPTPP help. The conference was hosted by the University of Waikato, working collaboratively with Ngā Toki Whakarururanga, with funding from the Ministry of Foreign Affairs and Trade (Manatū Aorere). University kaumātua (elder) Koro Taki Turner gifted the conference its name. Kāhui refers to an assembly of stars or in this case, people, while Kiwa is short for Te Moana nui a Kiwa—the great ocean of Kiwa, the Pacific Ocean.

text: Te Kāhui a Kiwa—Advancing Indigenous self determination and wellbeing through trade and can the CPTPP help This report provides an interim account of a conference held in Hamilton on 28-29 June 2023 called Te Kāhui a Kiwa—Advancing Indigenous self-determination and wellbeing through trade and can the CPTPP help. The conference was hosted by the University of Waikato, working collaboratively with Ngā Toki Whakarururanga, with funding from the Ministry of Foreign Affairs and Trade (Manatū Aorere). University kaumātua (elder) Koro Taki Turner gifted the conference its name. Kāhui refers to an assembly of stars or in this case, people, while Kiwa is short for Te Moana nui a Kiwa—the great ocean of Kiwa, the Pacific Ocean.

year: 2023-07-13