Project Spotlight: Oliver Denny – Using nematodes as bioindicators

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Ponderosa Pine/Bluebunch wheatgrass Reference Site at Kenna Cartwright Park

Overview:

Ponderosa Pine/Bluebunch wheatgrass ecosystems are threatened by multiple stressors, including the spread of invasive species, and it can be difficult to prioritize sites for restoration treatments. Soil nematode communities respond to ecosystem disturbances, which allows us to use nematodes as bioindicators. My study links the observed nematode community with established indices, allowing nematode analysis to be used as a tool for assessing ecosystem health.

Study site:

My project takes place in Kenna Cartwright Park, located in Kamloops B.C. The park is within the PPhx zone, classified as a very dry and very hot climate with Ponderosa Pine and Bluebunch wheatgrass as the dominant vegetation. It is a beautiful park and heavily used for hiking, mountain biking, and horseback riding. Much of the park ecosystem is dominated by big sage (Artemeisia tridentata) and bluebunch wheatgrass (Pseudoroegeneria spicata), however the southernmost part of the park is disturbed by the presence of invasive plants spotted knapweed (Centaurea stoebe) and dalmatian toadflax (L. dalmatica). The director of Kenna Cartwright park has expressed interest in finding efficient and novel methods to limit the spread of invasive species throughout the park.

Background:

My experiment uses nematodes extracted from the soil from invaded and undisturbed test sites as bioindicators of ecosystem health, and resilience to invasion. Four of every five multicellular animals on the planet are nematodes; they occupy every  niche with available organic carbon and vary in sensitivity to pollutants and other disturbances. Traditionally nematodes have been studied in the field of agriculture as many nematode species are plant parasitic and destroy crops. Nematodes are now further understood as a complex part of the soil food web and various groups are be classified as “beneficial” or “detrimental” to specific crops.

Recently several indices have been developed that use the responses of nematode taxa to disturbances as a basis to analyze soil health and further assess the environmental system.  My experiment uses the Maturity Index (MI) and the Colonizer- Persister scale, or c-p scale. Once nematodes are extracted from a sample they are analyzed with a compound microscope. I count the total nematode community and categorize each species group. Then each group is given a value based on the appropriate index scale, for example a Dorylaimina nematode, a K strategist, is generally ranked 5 c-p.

Some challenges I have encountered in my data collection have been buggy (pun intended) equipment: it can be difficult to get consistent accurate soil moisture readings with soil probes. Also, using a hand auger to drill holes in hard clay/rock is time consuming, and tough work in the sun! In my experience, an expert is needed for learning how to identify and differentiate each nematode species, reading from a book can only go so far and finding guidance from someone with technical experience is a must.

Field Tools: Auger, soil probe, GPS, and field notebook

Preliminary results:

So far, I have found that sites disturbed by invasive plants spotted knapweed and dalmatian toadflax have less diverse nematode communities. These sites are dominated by ‘colonizer’ type nematode species. Comparatively, undisturbed bluebunch wheatgrass ecosystems have a similar abundance of nematodes, but nematode diversity is higher than disturbed sites. Furthermore, nematode communities in undisturbed sites are dominated by ‘persitor’ type species.

Restoration applications:

With the completion of my project, Kenna Cartwright Park could use nematode analysis to rank areas in the park by susceptibility to invasion: areas with ‘colonizer type’ species may be less resilient to invasive species than those with ‘persistor types’. This would let Kenna Cartwright Park to prioritize sites for restoration treatments (such as hand pulling, mowing, or fire) in the ecosystem.

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