COS 2-5 - CANCELLED - Yearly shifts in nematode community diversity and composition in lakes, shorelines, and prairies depend on precipitation-associated factors

Abstract: Global climate change threatens belowground communities but the extent to which this occurs is not well understood. An overlooked and understudied impact of climate change is the modification of soil and sediment pH and biogeochemistry due to changes in precipitation. Soil and sediment microfauna communities (e.g., bacteria, fungi, nematodes) play important roles in ecosystem functioning and are strongly influenced by pH. Predicting their responses to climate driven changes in pH has important implications on ecosystem management (e.g., restoration and conservation) efforts. Nematodes can be used as a model belowground community to address questions about the effects of modified precipitation on soil biodiversity because of their ubiquity, abundance, and diversity. The goal of this study was to examine nematode community diversity and composition in response to reduced precipitation in the Western Nebraska Sandhills, a model system for future global change scenarios. To address our goal, we collected soil and sediment samples from three distinct habitat types (prairies, shorelines, and lakes) from five lake basins spanning an alkalinity gradient (pH 7-11) over three years. Samples were processed and analyzed for: 1. nematode communities via microscopy and 18S rDNA metabarcoding and 2. precipitation-associated factors such as alkalinity, lake level, and NDVI (i.e., primary productivity) in prairies. To determine the potential effects of shifts in precipitation on nematode community alpha diversity and composition, we used correlations, general linear models, and pairwise comparisons.

Here we show that as precipitation decreased, diversity of nematode communities declined in lakes and shorelines, primarily via receded lake water levels and elevated alkalinity. In contrast, diversity in prairies was not tied to soil moisture, alkalinity, nor primary productivity. Compositionally, nematode communities were distinct among different habitats. However, despite these habitat specific differences, they all responded to yearly shifts of precipitation-associated factors. In lakes and shorelines, composition was driven primarily by changes in lake level and alkalinity, while in prairies by alkalinity and primary productivity. Lastly, the impact of all precipitation-associated factors on composition was strongest in the lakes, followed by shorelines and prairies, respectively. In conclusion, this study suggests that the mechanism and magnitude of nematode diversity response to climate driven changes in precipitation and soil/sediment chemistry is dependent on habitat type.