Temporal Dynamism, Soil Processes and Niche Complementarity: Novel Approaches to Understanding Diversity-Function Relationships.

Schofield, Emily (2020) Temporal Dynamism, Soil Processes and Niche Complementarity: Novel Approaches to Understanding Diversity-Function Relationships. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

The temporal dynamics of key processes are a poorly understood yet potentially important factor in our understanding of plant coexistence in communities. Plants occupying the same spatial but differing temporal niches can coexist through niche differentiation, allowing coexistence in complex ecosystems. This thesis used barley as a model plant to investigate the temporal dynamics of plant and soil processes associated with nutrient uptake, and whether such dynamics might promote co-existence in competing plants. Through a series of lab-based studies I found that competition between barley cultivars can lead to a shift in the timing of peak nitrogen accumulation rate. However, estimates of peak nitrogen accumulation rate can be influenced by the experimental design, software program and statistical model used in these studies. At a molecular level, plant competition leads to temporally dynamic changes in the concentration of the plant hormone salicylic acid. There were also changes in gene expression depending on the identity of a neighbouring plant. I also explored the temporal dynamics of soil processes associated with plant nutrient uptake at a pot and root scale. At a pot scale, plant-plant competition did not lead to a significant shift in the temporal dynamics of soil carbon, nitrogen or microbial biomass. However, at a single root level, plant-plant competition led to a shift in the timing of peak activity of soil enzymes associated with nutrient turnover, indicating that the impact of plants on the soil microbial community might be one component of the mechanisms allowing temporally dynamic responses of plants to their neighbours. I also found that the ability to shift the timing of peak nitrogen accumulation rate in response to plant-plant competition has been conserved in modern cultivars of barley. This ability can be used in the development of greater complementarity in crop mixtures to improve crop yield stability. I demonstrated in this thesis that shifts in the temporal dynamics of plant nitrogen uptake in response to plant-plant competition involve both plant and soil components and can be inherited. These results contribute to our understanding of plant-plant competition dynamics and are applicable to both developing approaches for sustainable agriculture and for understanding coexistence in plant communities.