Biology subjects

Woodborne, S.

Publications and source records attributed to Woodborne, S..

3 recordsLinked to original sources

bioRxiv2025

Baobab isotope records and rainfall forcing in southwest Madagascar over the last 700 years.

Highly resolved climate records for Madagascar are scarce but are essential for understanding of rainfall drivers over time and assessing the risks and likely trajectories of future climate change. We measured variation in the carbon isotopes of baobabs (Adansonia spp.) which reflect rainfall in southwest Madagascar. The record indicates a decreasing trend of rainfall over the last 700 years with high variability at a centennial-scale. The duration of wetter periods decreased over time with the wettest periods between 1350 - 1450 CE, after the onset of the Little Ice Age, while the driest period occurred between 1600 - 1750 CE, during the Maunder Minimum. The results suggest that decadal to centennial rainfall variability in southwest Madagascar is dominated by tropical forcing rather than subtropical forcing. Wetter periods are regulated by the movement and migration of easterly winds linked to the Intertropical Convergence Zone, while dry periods are influenced by the effect of the Pacific Decadal Oscillation linked to the El Nino Southern Oscillation and the sea surface temperature variation in the Southwestern Indian Ocean. The Southern Annular Mode is significantly correlated with the record, but its effect was only visible at the beginning of the record around 1300 CE. This evidence provides a new understanding of rainfall across southern Africa and the interaction of global forcing with regional factors. Further investigation is required to improve tree chronology from Southern Hemisphere and understand the migration of the westerlies and its potential future effect on the rainfall in Madagascar. Understanding the interplay between tropical and other rainfall forcings will be essential in assessing likely scenarios of resilience, and adaptive capacity of social-ecological systems in Madagascar.

ecology↗

bioRxiv2020

Nutrient parsimony shapes diversity and functionality in hyper-oligotrophic Antarctic soils

The balance of nutrients in soil is critical for microbial growth and function, and stoichiometric values below the Redfield ratio for C:N:P can negatively affect microbial ecosystem services. However, few studies have assessed the relationships between nutrient balance and biological productivity in extremely nutrient-poor habitats. The Mackay Glacier region of Eastern Antarctica is a hyper-oligotrophic ice-free desert and is an appropriate landscape to evaluate the effects of nutrient deficiency and imbalance on microbial community ecology. In a survey of multiple, widely dispersed soil samples from this region, we detected only low rates of microbial respiration, and observed that C:N:P ratios were well below those required for optimal activity. In silico metagenomic and soil isotopic ratio ({delta}15N) analyses indicated that the capacity for nitrogen fixation was low, but that soil microbial communities were enriched for soil nitrate assimilation processes, mostly associated with heterotrophic taxa.{delta} 13C isotope ratio data suggested that carbon dioxide was fixed principally via the Calvin cycle. Genes involved in this pathway were common to all metagenomes and were primarily attributed to members of the dominant soil bacterial phyla: Bacteroidetes and Acidobacteria. The identification of multiple genes encoding non-photoautotrophic RUBISCO and carbon dioxide dehydrogenase enzymes in both the metagenomic sequences and assembled MAGs is suggestive of a trace-gas scavenging physiology in members of these soil communities.

ecology↗

bioRxiv2019

Multi-proxy analyses of a mid-15th century Middle Iron Age Bantu-speaker palaeo-faecal specimen elucidates the configuration of the ancestral sub-Saharan African intestinal microbiome

The archaeological incidence of ancient human faecal material provides a rare opportunity to explore the taxonomic composition and metabolic capacity of the ancestral human intestinal microbiome (IM). Following the recovery of a single desiccated palaeo-faecal specimen from Bushman Rock Shelter in Limpopo Province, South Africa, we applied a multi-proxy analytical protocol to the sample. Our results indicate that the distal IM of the Neolithic Middle Iron Age (c. AD 1485) Bantu-speaking individual exhibits features indicative of a largely mixed forager-agro-pastoralist diet. Subsequent comparison with the IMs of the Tyrolean Iceman (Otzi) and contemporary Hadza hunter-gatherers, Malawian agro-pastoralists and Italians, reveals that this IM precedes recent adaptation to Western diets, including the consumption of coffee, tea, chocolate, citrus and soy, and the use of antibiotics, analgesics and also exposure to various toxic environmental pollutants. Our analyses reveal some of the causes and means by which current human IMs are likely to have responded to recent dietary changes, prescription medications and environmental pollutants, providing rare insight into human IM evolution following the advent of the Neolithic c. 12,000 years ago.

microbiology↗