Biology subjects

Timmusk, S.

Publications and source records attributed to Timmusk, S..

5 recordsLinked to original sources

bioRxiv2025

Soil Carbon Sequestration in Nothofagus obliqua Forests with Different Canopy Cover Levels under Silvopastoral Management

Agroforestry contributes to slowing deforestation, favouring ecosystem regeneration and improving land use sustainability. In this study, we evaluated the effect of agroforestry on the recovery of degraded soils in a native forest and its capacity to capture and stabilize carbon (C) and nitrogen (N) in the soil. We conducted the study in a native forest of Nothofagus obliqua (oak) located in Ranchillo Alto (37{degrees}04'52'' S, 71{degrees}39'14'' W), in the Nuble region, Chile. This site includes three silvopastoral systems with different levels of forest degradation: open (Op), semi- open (SOp) and semi-closed (SC), together with a control treatment without silvopastoral treatment (Ctr). The analysis was conducted at four soil depths (0-10, 10-20, 20-30 and 30-60 cm). To evaluate carbon and nitrogen sequestration and fixation in relation to the different forest cover treatments, we performed chemical, physical and biological soil analyses. We also included a physical fractionation by particle size to separate soil organic matter (SOM) into meaningful fractions with different characteristics and dynamics: particulate organic matter (POM) and organic matter associated with the mineral matrix (MAOM). Our results indicated that Op, despite being the most degraded condition, showed the highest values of C, N and non- oxidizable carbon (Cnox). This condition could be associated with the history of potato burning in this sector, which generates stable pyrogenic carbon in the soil. Analyses of C and N, as well as Cnox in the MAOM fraction, and C stock revealed that the three silvopastoral systems showed higher values than the control treatment without silvopastoral treatment. This suggests that the adoption of silvopastoral practices can improve soil quality and contribute to long-term carbon sequestration. These results support the application of sustainable practices to mitigate soil degradation and enhance carbon sequestration in degraded ecosystems.

ecology↗

bioRxiv2024

Comparative analysis of microbial communities of soils under contrasting microclimates

Understanding how microbiomes influence the life cycle and fitness of crops, and how global change drivers disrupt this network, is pivotal for an understanding of the crop as a holobiont, and of how to provide solutions for Nordic agricultural crop resilience under climate change. Despite decades of use of plant growth-promoting rhizobacteria (PGPR), there is an intrinsic problem with their applications, as it has become evident that their functionality and performance rely on interactions with the environment and with other microorganisms. The synthetic crop-promoting rhizobacterial community strains are being outcompeted by native communities, or their colonisation and active principles are being reduced to ineffective levels. This is the result of the communities being selected on taxonomic criteria rather than qualitative analysis of the microbiome-associated plant phenotypes. In this context there in an urgent need for an approach studying the microbial community and plant complementarity traits from indigenous communities. Here we report the pattern of bacterial distributions at the Evolution Canyon (EC) in Israel to gain insight into microbiomes exposed to contrasting microclimates at the North Facing Slope (NFS) and South Facing Slope (SFS) sun and shade areas using high-throughput sequencing. While the NFS and SFS shaded areas bacterial distribution didnt differ, our results show significant differences between the NFS and the SFS sunny areas. The families Geodermatophilaceae, Beijerinckiaceae, and Pseudonocardiaceae are dominant in the NFS sun area, and the families Rubrobacteriaceae, unclassified Solirubrobacterales bacterium 67-14, unclassified Actinobacteriota, class Gaiellales dominate at the SFS sun area. Likewise, both Shannon and inverse Simpsons diversity indices are higher at the NFS sun area compared to the NFS shaded area. There was no substantial difference between diversity indices in SFS sun and shaded area. Our results advance our understanding of the bacterial distributions at what is in effect a natural laboratory of ecosystems that probably evolved 5-7 million years ago. The data are an important step towards using transcriptomics, metabolomic profiles and selective plating for figuring out key strains and the supporter strains that strengthen the ecological functions of the key strains. Collectively, this will enable us to assemble redundant and stable synthetic PGPR communities consisting of key and supporter strains for promoting plant health and stress tolerance under changing climates.

microbiology↗

bioRxiv2023

The species richness of the Salix viminalis rhizosphere at the Stebnyk tailings storages dependent on supplementation from the Salicornia europaea rhizosphere

Manipulating the rhizosphere microbiome to enhance plant stress tolerance is an environmentally friendly technology and a renewable resource to restore degraded environments. Here we considered the Salicornia europaea rhizosphere community, and the ability of the phytoremediation plant Salix viminalis to recruit its beneficial microbiome to mediate the pollution stress at the Stebnyk mine tailings storage. The tailings contain large amounts of brine salts and heavy metals that contaminate the ground water and surrounding areas, changing soil biogeochemistry and causing increased erosion. The species richness of the endophytic bacterial community of S. viminalis roots was assessed based on observed OTUs, Shannon-InvSimpson, and evenness index. Our results show that biodiversity was decreased across the contamination zones and that S. europaea supplementation significantly increased the species richness. Our results also indicate that the number of dominating OTUs was not changed across zones in both S. europaea-treated and untreated bacterial populations, and that the decrease in richness was mainly caused by the low abundance of OTUs. The importance of engineering microbial communities that support the genetic diversity of degraded environments and the challenges with high throughput metabarcoding databases are discussed.

microbiology↗

bioRxiv2021

Biodegradation of naphthalene mediated by the plant growth promoting rhizobacteria

We compared the ability of two bacterial strains, Paenibacillus polymyxa A26 and P. polymyxa A26Sfp, for biodegradation of naphthalene (NAP). The studies were performed under simulated laboratory conditions, in liquid medium and soil with different carbon sources, pH and salt contents. Changes in the luminescence inhibition of Aliivibrio fischeri, as an indicator of the baseline toxicity, were observed in degradation mixtures during 7 days of incubation. While both strains expressed the best growth and NAP degradation ability in the minimal salt medium containing sucrose and 5% NaCl at pH 8, the mutant strain remained effective even under extreme conditions. A26Sfp was found to be an efficient and potentially industrially important polycyclic aromatic hydrocarbon degradation strain. Its extracellular polysaccharide production is 30% and glucan production twice that of the wild type A 26. The surface tension reduction ability was ascertained as 25-30% increased emulsification ability.

microbiology↗

bioRxiv2020

Silica particles trigger the production of exopolysaccharides in harsh environment plant growth-promoting rhizobacteria and increase their ability to enhance drought tolerance

In coming decades drought is expected to expand globally owing to increased evaporation and reduced rainfall. In order to reduce the vulnerability of agricultural systems we need to understand the crop plant growth environment. Understanding, predicting and controlling the rhizosphere has potential to harness plant microbe interactions, improve plant responses to environmental stress and mitigate effects of climate change. Our plant growth-promoting rhizobacteria (PGPR) are isolated from the natural laboratory Evolution Canyon Israel (EC). The endophytic rhizobacteria from the wild progenitors of cereals have been co-habituated with their hosts for long periods of time. The study revealed that silica particles (SN) triggered the PGPR production of exopolysaccharides (EPS) containing D-glucuronate (D-GA). This leads to increased plant biomass accumulation in drought-stressed growth environments. The PGPR increased EPS content increases the water holding capacity (WHC) and osmotic pressure of the biofilm matrix. Light- and electron-microscopic studies show that in the presence of SN particles, bacterial morphology is changed, indicating that SNs are associated with significant reprogramming in bacteria. The results here show that the production of EPS containing D-GA is induced by SN treatment. The findings encourage formulation of cells considering microencapsulation with materials that ensure higher WHC and hyperosmolarity under field conditions. Our results illustrate the importance of considering natural soil nanoparticles in the application of PGPR. Osmotic pressure involvement of holobiont cohabitation is discussed.

microbiology↗