The effect of drought on soil microbial community dynamics in Norway spruce seed orchards

Ing. Dagmar Zádrapová

Doctoral thesis

Abstract:

Climate change profoundly impacts both abiotic and biotic environmental factors in forest ecosystems. Rising temperatures and shifting precipitation patterns alter soil moisture content, which in turn influences the diversity, abundance, and functions of soil microbial communities. However, research on the long-term effects of precipitation variability on forest soil microfauna remains surprisingly limited. In this study, we investigated the impact of long-term precipitation variation on soil quality parameters and microbial community dynamics in the two Norway Spruce (Picea abies) clonal seed orchards: Lipová Lhota (L-site) and Prenet (P-site). Over three decades, precipitation data revealed that the P-site received nearly twice the amount of rainfall compared to the L-site. We analysed the effects of precipitation on both rhizospheric soil and the surrounding bulk soil. By integrating traditional methods with modern multi-omics approaches, we aimed to assess soil texture, physicochemical properties (pH, EC), biochemical parameters (total organic carbon (TOC), total nitrogen (TN)), phospholipid fatty acid (PLFA) content, extracellular enzyme activities, metabolic profiles, along with microbial community structure in the two forest soils. Our results revealed a positive correlation between TOC, TN, extracellular enzyme activities, and phospholipid fatty acid (PLFA) content in the soil with increased precipitation, while microbial diversity exhibited an opposite trend. The soil metabolite profiles showed distinct variations between the two sites, with a higher abundance of metabolite at the P-site, which receives greater precipitation. Additionally, the rhizospheric soul at the P-site had elevated levels of Aluminium (Al), Iron (Fe), Phosphorus (P), and Sulphur (S) compared to the L-site. Variance partitioning canonical correspondence analysis (VPA) further demonstrated that TOC and TN played a greater role in shaping soil microbial communities compared to soil pH and electrical conductivity. Clear microbiome differences were also observed between the sites. The P-site rhizospheric soil exhibited a higher abundance of Proteobacteria, Acidobacteriota, Ascomycota, and Mortierellomycota, while the L-site showed a higher prevalence of Bacteroidota, Actinobacteria, Chloroflexi, Firmicutes, Gemmatimonadota, and Basidiomycota. A higher clustering coefficient in the P-site rhizospheric soil microbial network indicated a more interconnected and closely clustered microbial community structure. Overall, our study unveiled the impact of precipitation variability on microbial communities and functions in bulk soil and the rhizospheric microbial associations of two Norway spruce stands. The generated field data provided valuable insights for modelling the effects of long-term precipitation changes on forest ecosystems, offering new perspectives for understanding how the global climate change affects soil microbial associations in forest tree species.

Keywords

precipitation, climate change, bacterial diversity, fungal diversity, microbiome, amplicon sequencing, PLFA analysis, soil metabolites, rhizosphere, bulk soil

Language used: English

Date on which the thesis was submitted / produced: 4. 10. 2024

Thesis defence

• Supervisor: doc. Ing. Ivana Tomášková, Ph.D.
• Reader: Marketa Marečková, doc. RNDr., Ph.D., Jolanta Behnke-Borowczyk, externi, Sandeep Kushwaha, externi

Czech University of Life Sciences Prague

Faculty of Forestry and Wood Sciences

Doctoral programme / field:
Forestry Engineering / Forest Biology