Biology subjects

Adekanmbi, A. A.

Publications and source records attributed to Adekanmbi, A. A..

3 recordsLinked to original sources

bioRxiv2025

Forest biogeochemical monitoring indicates altered microbial communities, macronutrient availability, CO2 emissions and litter chemistry in root zone soil of oak trees with Acute Decline symptoms

Acute and Chronic Oak Decline (AOD & COD) widely impact oak woodlands across Europe. AOD is known to cause rapid decline in tree health in a short span of 3-5 years. However, the interactions between such oak decline and soil biogeochemical dynamics are not fully understood. We selected three oak trees for each of the three treatments for biogeochemical monitoring: 1. No symptoms (Healthy), 2. AOD & 3. COD symptoms, in Writtle woodlands, Essex, UK. The selected trees were used for quarterly root zone soil sampling (cores to depth of 40 cm), and monthly surface soil (0-10 cm), leaf litter and GHG emissions sampling over a year (2022-23). Soil samples were characterised for their physico-chemical properties, total nutrient content & availability. Leaf litter samples were sorted into branches, leaves, seeds and flowers, weighed and their chemistry characterised. Soil microbial communities were characterised using phospholipid fatty acid analyses. Almost all the measured properties showed significant changes with season and depth, indicating a strong temporal and depth effect on forest soil biogeochemical dynamics. Notably macro-nutrient contents of leaf litter were greater in the summer period, which resulted in increased soil nutrient availability in autumn. This pattern was particularly exaggerated in AOD trees, which had greater nutrient content in litterfall in summer and greater nutrient availability in root zone soil in autumn than those of COD and Healthy trees. We found that AOD root zone soil have altered microbial communities, decreased CO2 emissions and increased macronutrient availability. Taken together, our study shows poor physiological nutrient management by diseased AOD trees revealed by greater nutrient concentration in AOD leaf litter indicating the lack of nutrient resorption and re-allocation before leaf senescence, and less active root zone soil under AOD trees, shown by reduced soil CO2 emissions and increased nutrient availability in oak root influenced zones. Hence, we conclude that the biogeochemical dynamics of AOD root zone soils are significantly different to that of healthy and COD trees, however controlled experiments are needed alongside these field observations to disentangle the causes from effects in understanding the relationship between soil health and oak decline. HighlightsO_LIWe monitored forest soil biogeochemical dynamics under oak trees of different health status C_LIO_LIAcute Oak Decline (AOD) trees had greater macronutrient availability in root zone soils C_LIO_LIAOD trees had greater nutrient content in litter added to the root zone soil C_LIO_LIAOD root zone soils had altered microbial community structure & reduced CO2 emissions C_LIO_LIWe conclude that AOD trees have poor physiological nutrient management and less active rhizosphere compared to healthy trees. C_LI

ecology↗

bioRxiv2023

Legacy of warming and cover crops on the response of soil microbial function to repeated drying and rewetting cycles

The response of soils to extreme weather events will become increasingly important in the future as more frequent and severe floods and droughts are expected to subject soils to drying and rewetting cycles as a result of climate change. These extreme events will be experienced against a backdrop of overall warming. However, farmers are adopting cover cropping as a sustainable management practice to increase soil organic matter, benefit soil health, and to increase the resilience of soils to help mitigate the impacts of climate change. We examined the legacy of warming and cover crops on the response of soil microbial function to repeated drying and rewetting cycles. We introduced open top chambers to warm the soil surface of a field plot experiment in which cover crops (single species monocultures and 4-species polycultures) were grown over the summer after harvest and before planting of autumn sown cash crops in a cereal rotation. Soil samples were collected from warmed and ambient areas of the experimental plots in spring, before harvesting the cereal crop. We quantified respiration (a measure of soil microbial function) with high-frequency CO2 flux measurements after 0, 1, 2, 4, or 8 wet/dry cycles imposed in the laboratory and the addition of barley grass powder substrate at a ratio of 10 mg g-1 soil. Cover crop mixtures created a negative legacy effect in the soil which resulted in lower cumulative substrate induced respiration than expected from the average of the same species grown in monoculture. Repeated drying and rewetting cycles increased the cumulative substrate induced respiration rate observed, suggesting that repeated perturbations selected for a community adapted to processing the barley shoot powder more quickly. This adaptation may have resulted in a greater osmolyte production or reacquisition by microorganisms exposed to repeated drought events. Osmolytes are rapidly metabolised upon re-wetting and may have primed the decomposition of the barley shoot powder to a greater extent in soils previously exposed to drying and rewetting cycles. When we calculated the cumulative respiration after 8 wet/dry cycles, relative to cumulative respiration after 0 wet/dry cycles (which we infer represents the extent to which microbial communities adapted to repeated drying and rewetting cycles) our data revealed that the legacy of warming significantly reduced, but cover crops significantly increased, soil microbial community adaptation. This adaptation of the soil microbial community was positively correlated with the concentration of water extractable organic carbon in the soils prior to imposing the drying and rewetting cycles and/or adding the substrate. The availability of labile carbon may have mediated the ability of microorganisms to synthesise osmolytes in response to drought. We conclude that cover crops may enhance the ability of the soil microbial community to adapt to drought events and mitigate the impact of warming, possibly due to the provision of labile organic carbon for the synthesis of osmolytes.

microbiology↗

bioRxiv2021

Legacy effect of constant and diurnally oscillating temperatures on soil respiration and microbial community structure

1.0Laboratory incubation studies evaluating the temperature sensitivity of soil respiration often use measurements of respiration taken at a constant incubation temperature from soil that has been pre-incubated at the same constant temperature. However, such constant temperature incubations do not represent the field situation where soils undergo diurnal temperature oscillations. We investigated the effects of constant and diurnally oscillating temperatures on soil respiration and soil microbial community composition. A grassland soil from the UK was either incubated at a constant temperature of 5 {degrees}C, 10 {degrees}C, or 15 {degrees}C, or diurnally oscillated between 5 {degrees}C and 15 {degrees}C. Soil CO2 flux was measured by temporarily moving incubated soils from each of the abovementioned treatments to 5 {degrees}C, 10 {degrees}C or 15 {degrees}C, such that soils incubated at each temperature had CO2 flux measured at every temperature. We hypothesised that, irrespective of measurement temperature, CO2 emitted from the 5 {degrees}C to 15 {degrees}C oscillating incubation would be most similar to the soil incubated at 10 {degrees}C. The results showed that both incubation and measurement temperatures influence soil respiration. Incubating soil at a temperature oscillating between 5 {degrees}C and 15 {degrees}C resulted in significantly greater CO2 flux than constant incubations at 10 {degrees}C or 5 {degrees}C, but was not significantly different to the 15 {degrees}C incubation. The greater CO2 flux from soils incubated at 15 {degrees}C, or oscillating between 5 {degrees}C and 15 {degrees}C, coincided with a depletion of dissolved organic carbon and a shift in the phospholipid fatty acid profile of the soil microbial community, consistent with the thermal adaptation of microbial communities to higher temperatures. However, diurnal temperature oscillation did not significantly alter Q10. Our results suggest that daily maximum temperatures are more important than daily minimum or daily average temperatures when considering the response of soil respiration to warming.

microbiology↗