Bottom-up and direct effects of water availability on an urban food web

Background/Question/Methods

Water resources can control terrestrial food webs via bottom-up effects on primary production, or via direct alterations of consumer stress and trophic interactions.  To date, both of these effects have been documented separately, but little to no research has examined the direct and indirect effects of water resources in a fully-crossed design.  Using urban brittlebush (Encelia farinosa) microcosms in Phoenix, AZ, we document how manipulations of belowground or aboveground water availability alter food web structure and belowground and aboveground primary production.

Results/Conclusions

As expected, we detected bottom-up effects of belowground irrigation on aboveground plant biomass and arthropod community structure.  We also observed changes in arthropod community structure with aboveground water availability.  This research highlights the direct importance of surface water availability in altering terrestrial animal communities.