For the 2018-2019 Harward Lecture, Randy Dahlgren (Professor, University of California, Davis) will be presenting "Biogeochemistry in California Oak Woodland-Annual Grassland Rangelands."

Oak woodland-annual grasslands in California often exist at the interface between urban, wild and agricultural lands and are used extensively for livestock grazing, wildlife habitat and surface water supply.  Strong gradients in biogeochemical processes occur in time and space owing to differences in vegetation (tree vs open grassland) and seasonal changes within the Mediterranean climate. Oak trees create islands of enhance soil quality beneath their canopy through a variety of nutrient-cycling processes. Seasonal rainfall patterns create a temporal discoupling of nutrient cycles owing to sharply contrasting differences between biological demand and seasonal rainfall patterns. Understanding biogeochemical processes at the ecosystem scale provides insights to enhance management activities for various ecosystem services.