COS 101-5 - Influence of fungicide and nematicide on plant responses to drought and rainfall variability

Background/Question/Methods

Because increased drought and rainfall variability are affecting natural environments in the Midwest and across the globe, it is imperative to study how plant interactions with other organisms influence drought tolerance. Microbial organisms, such as fungi and nematodes, can have both symbiotic and pathogenic interactions with plants. However, we do not yet understand how these microbial interactions influence plants under drought stress. For this REU project we leveraged a new large-scale rainout shelter experiment with fungicide and nematicide manipulations to see 1. how fungi and nematode abundance alters plant growth and flowering and 2. how fungi and nematode abundance alters plant growth during drought and rainfall variability. For this new experiment set up, we wanted to see how variation in plant communities differs across treatments. We took plant measurements in control, fungicide and nematicide treatments in irrigated, drought, and variable rainfall shelters on early successional vegetation at two time points. We measured percent ground cover and percent flower cover for the whole plant community. In the same plots we also recorded plant height, specific leaf area and leaf dry matter content (LDMC) on Red Clover (Trifolium pratense) and Goldenrod (Solidago canadensis).

Results/Conclusions

For the community measurements, we found that between the two sampling times percent flower cover decreased in fungicide subplots more than nematicide subplots (p=0.04). Early in the experiment, soon after pesticide application, we found that LDMC for red clover was lower in nematicide subplots than in fungicide subplots (p=0.02). Later in the experiment, after rainout shelters were added, we saw the effects of precipitation treatments. We observed that LDMC increased under drought compared to irrigated and variable rainfall treatments (p< 0.001). Rainfall treatments and biocide treatments had no significant effects on percent ground cover, plant height, and specific leaf area. We showed that fungi and nematode abundance altered plant phenology and physiology in ways that could influence plant drought tolerance. With the addition of data analysis from later collection times, we will be able to further test the impact of fungi and nematode abundance on plant drought tolerance.