Climate models forecast an intensification of the global hydrological cycle. The distribution, structure, composition, and diversity of plant populations and communities will be affected by altered precipitation regimes, having long reaching consequences for ecosystems. Plant response to precipitation changes is of the utmost importance for an ecosystem because varied precipitation can have an effect on a significant plant interaction, herbivory. Belowground plant parasitic nematodes (PPN) directly impact plant productivity and survivorship as well as indirectly affect many rhizosphere interactions, playing an integral role in soil food webs. However, the response of PPN to changes in precipitation are little known, especially in grasslands where maintaining plant productivity for grazing livestock is central to local economies. To test how shifts in precipitation may affect grassland ecosystems, specifically plant interactions with PPN, a large-scale field experiment was set up across three biomes, representing a gradient of precipitation from arid desert to mesic grasslands: Jornada Desert grassland, NM, Shortgrass steppe, CO, and Tallgrass prairie, KS. A manipulative experiment with additions and reductions of precipitation during two consecutive years was used to test PPN responses to changing precipitation patterns via rainout shelter systems.
Results/Conclusions
The cross-biome experiment showed an overall trend of the plant parasitic nematode genera diversity increasing along the spatial water-availability gradient, having the greatest number of genera groups in the mesic site, Tallgrass prairie. Although precipitation treatments did not affect the generic composition of PPN communities, differences among dry and wet years in relation to the long-term average were significant at all three sites (npMANOVA Jornada: df = 2, F = 42.4, r2 = 0.36, P = 0.01; Shortgrass df = 2, F = 20.98, r2 = 0.21, P = 0.01; Konza: df = 2, F = 23.80 r2 = 0.23, P = 0.01). When considering the feeding habits of PPN more complex patterns and differences among sites emerge; as the Shortgrass Steppe had the greatest ratio of endoparasitic to ectoparasitic plant parasites. The divergent changes in PPN composition in response to inter-annual variation in precipitation across a regional biome gradient provides novel insights into the possible response of plants to herbivory to varied precipitation with climate change.