Biology subjects

Bradford, M. A.

Publications and source records attributed to Bradford, M. A..

3 recordsLinked to original sources

bioRxiv2025

Low quality evidence dominates discussion of carbon benefits of alternative grazing strategies

There is enormous interest in utilizing alternative grazing strategies to improve rangeland condition, increase profitability and decrease the carbon footprint of livestock production via soil organic carbon (SOC) sequestration. Here we present a systematic review and meta-analysis of the literature on alternative grazing strategies and their impact on SOC. Most studies (47 out of 70) failed multiple quality criteria. The 10 studies with 27 observations that met all inclusion criteria showed no change in SOC. Further dividing these observations by study design (controlled small-plot experiment versus observational paired site study) or grazing management style (adaptive or prescribed) or by aridity class or by grassland type failed to reveal any trends. Gains in SOC were only found for a secondary group of 13 studies with 25 observations, primarily composed of paired comparisons where there were unresolved questions about the quality of the site pairings for supporting causal inference. This divergence in results between primary and secondary studies highlights that low-quality evidence dominates the discussion around the climate benefits of alterative grazing strategies, underscoring a critical need for stronger evidence before asserting climate change mitigation benefits from alternative grazing practices. For submission toCommunications Earth & Environment

ecology↗

bioRxiv2025

Tree microbiomes and methane emissions in upland forests

RationaleUpland forest trees emit CH , but whether emissions derive from internal microbial production or soil-derived transport remains debated. Methanogens have been detected in heartwood of several species, yet the prevalence of wood-associated methanogenesis, its metabolic basis, and its relationship to co-occurring methanotrophy are poorly understood. MethodsWe measured 1,148 stem fluxes and 276 soil fluxes, sampled internal stem gases including {delta}{superscript 1}3CH , quantified methanogens and methanotrophs via ddPCR in 564 samples, characterized communities via 16S rRNA sequencing, and upscaled fluxes. Key resultsMethanogens were detected in 97% of heartwood samples (up to 10 copies g {superscript 1}) at concentrations exceeding soil by [~]2 orders of magnitude; methane consumers were likewise near-ubiquitous across forest compartments. Wood harbored distinct microbial communities dominated by hydrogenotrophic Methanobacteriaceae, corroborated by depleted {delta}{superscript 1}3CH . Vertical flux profiles indicated soil transport only in wet microsites, with uniform emissions across height consistent with internal production across most upland species. Species-level methanogen:methanotroph ratios predicted emissions (R{superscript 2} = 0.51), indicating net flux reflects the balance between production and oxidation. Main conclusionMethane-cycling microbes are widespread in upland trees, and net methane flux reflects the species-level balance between production and consumption. Internal methanogenesis contributes widely to upland tree emissions; resolving ecosystem-scale magnitude requires improved quantification of woody surface area and vertical flux variability.

ecology↗

bioRxiv2024

A diverse and distinct microbiome inside living trees

Despite significant advances in microbiome research across various environments1, the microbiome of Earths largest biomass reservoir- the wood of living trees2- remains largely unexplored. This oversight neglects a critical aspect of global biodiversity and potentially key players in tree health and forest ecosystem functions. Here we illuminate the microbiome inhabiting and adapted to wood, and further specialized to individual host species. We demonstrate that a single tree can host approximately a trillion microbes in its aboveground internal tissues, with microbial communities partitioned between heartwood and sapwood, each maintaining a distinct microbiome with minimal similarity to other plant tissues or nearby ecosystem components. Notably, the heartwood microbiome emerges as a unique ecological niche, distinguished in part by endemic archaea and anaerobic bacteria that drive consequential biogeochemical processes. Our research supports the emerging idea of a plant as a "holobiont"3,4--a single ecological unit comprising host and associated microorganisms--and parallels human microbiome research in its implications for host health, disease, and functionality5. By mapping the structure, composition, and potential sources and functions of the tree internal microbiome, our findings pave the way for novel insights into tree physiology and forest ecology, and establish a new frontier in environmental microbiology.

ecology↗