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Plant-plant competition influences temporal dynamism of soil microbial enzyme activity

Competition between plants can cause a change in the timing of key processes including nutrient uptake. But we don’t know the effect this has on the temporal dynamics i.e. the timing and rate of soil microbial activity. In newly published research, Rowntree-lab PhD student Emily Schofield used zymography to investigate the effect of plant-plant competition on the activity of the soil microbial community using barley (Hordeum vulgare) as a model plant. Zymography is a technique to look at soil enzyme activity using fluorescently labelled substrate. Enzymes produced by soil microbes break down the substrate, exposing the fluorescent tag. Schofield et al. (2019) chose two enzyme classes to measure, both involved in nutrient turnover. Cellulase is involved in cellulose breakdown and leucine aminopeptidase in the mineralisation of nitrogen.

Schofield sampled enzyme activity surrounding barley roots weekly for the first month of growth of barley grown in isolation, inter- and intra- cultivar competition. There was a delay of seven days in peak cellulase activity when barley was in competition compared to plants in isolation. However, there was only a significant delay in leucine aminopeptidase activity when barley was in intra-cultivar competition, not inter-cultivar competition. Plant-plant competition therefore impacted the two soil enzyme classes differently. The plants may have influenced the timing of nutrient availability by altering the quantity and composition of root exudates, an exciting avenue for future work. This work contributes to our understanding of coexistence in complex plant communities, and may also be important when designing crop mixtures to maximise fertiliser application efficiency.

Schofield, E. J., Brooker, R. W., Rowntree, J. K., Price, E. A. C., Brearly, F. Q., Paterson, E. (2019) Plant-plant competition influences temporal dynamism of soil microbial enzyme activity. Soil Biology and Biochemistry 139: 107615

Image © E. J. Schofield 2019. False colour images showing the sampling location and intensity of enzyme activity (leucine aminopeptidase) surrounding Proctor barley roots in competition with its own variety (intra-cultivar competition). The brighter colours show a greater intensity of enzyme activity and darker colours less intense enzyme activity.

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