Microbial respiration and diversity in response to previous landuse

Soil health places emphasis on the living component of the soil, and its contribution to soil processes and functions underpinning the delivery of ecosystem services. Various measures can be used to assess the soil biological community and its activity. However, few measures have targets for optimal populations or the knowledge to manage these, limiting the potential biological indicators available.

Microbial respiration and the addition of different carbon substrates can be used to indicate the activity and potential changes of a microbial community, as well as implications for soil functioning. We used MicroResp methods to investigate how microbial activity and diversity changed in response to previous management on a Lismore stony silt loam in Canterbury. The site was previously under Pinus radiata and was converted to irrigated dairy pasture in 2016. We also explored whether differences in respiration rates are predictable through time.

Initial data shows basal respiration rates were not different between sites under existing P. radiata in comparison to recently converted pastures. Although there were some differences in respiration rates with carbon substrates observed in relation to time since forestry, this did not necessarily align with patterns of bacterial and fungal diversity. The greatest differences in respiration rates were observed between samples collected in spring compared to autumn. We discuss the implications of these results and investigate factors driving changes in biological measures. Continuing to assess the microbial activity and diversity through time will improve our understanding of soil biological health.