Mapping soil health from microbial genes
Figure 1. Extracting and analysing DNA from samples collected for soil quality assessment can provide information on the variation, abundance and diversity of microbial genes that provide vital ecosystem services.
Soil scientists from regionals councils (Northland RC, Auckland Council, Waikato RC, Hawke’s Bay RC, Greater Wellington RC, Tasman District Council, Marlborough District Council, Environment Canterbury and Environment Southland), the University of Auckland (Dr Gavin Lear) and Landcare Research (Dr Bryan Stevenson) have joined together to take soil quality monitoring to a higher level.
Using soil that regional councils annually collect from different land uses and soil types throughout New Zealand, a soil microbial component is being trialled in addition to the standard suite of sampling analyses, as an indicator of soil quality. The intention is to record variation in the abundance and diversity of microbial genes that are known to provide vital ecosystem services, including nutrient storage and cycling. Our research is intended to provide substantial added value to regional councils’ soil quality monitoring programmes that to date have focused on soil physicochemical data such as measures of organic carbon, total nitrogen, pH, Olsen P, macroporosity, and trace elements.
The inclusion of a microbial component to monitoring may provide advances over traditional strategies used by councils to report on the long-term status of New Zealand’s natural soil resource. Importantly, the delayed response of soil physicochemical measures to land-use change means current soil monitoring strategies can overlook the onset of serious soil degradation. In contrast, bacterial communities respond very rapidly to environmental change, allowing declines in soil health and fertility to be detected at a far earlier stage, before degradation is severe or perhaps irreversible. Modern molecular (DNA) methods allow us to reliably target specific ecosystem processes for inclusion in monitoring networks (e.g. targeting genes of particular interest, such as those involved in the nitrogen cycle, or originating from particular soil pathogens). Furthermore, microbial measures may provide a relevant bioindicator of soil status compared with standard chemical measures. This is because, similar to plant roots, soil microorganisms respond to bioavailable fractions of contaminants or nutrients.
What this means for the future is that we’ll be able to inform land managers and landowners more quickly about the status of their soil resource and what they can do in terms of land management practice. Further, the information collected will also inform policy and science direction in regional councils, which will help maintain and improve soil health around New Zealand. Without the collaboration and coordination of the regional councils, the University of Auckland and Landcare Research, this project would not be possible. It demonstrates the importance of using the resources different parties can offer.
Fiona Curran-Cournane – Auckland Council
P: 09 301 0101 E: Fiona.Curran-Cournane@aucklandcouncil.govt.nz
Bryan Stevenson – Landcare Research
P: 07 859 3797 E: stevensonb@landcareresearch.co.nz
Gavin Lear – Auckland University
P: 09 373 7599 E: g.lear@auckland.ac.nz