Responses of soil community structure to plant species and precipitation inputs: Linking soil biota to ecosystem carbon cycling.
Pavao-Zuckerman, Mitchell*,1, Cable, Jessica1, Yepez, Enrico2, Potts, Daniel1, Huxman, Travis1, Williams, David 2, 1 University of Arizona, Tucson2 University of Wyoming, Laramie
ABSTRACT- Despite the importance of soil carbon cycling to the response of water-limited ecosystems to global change, our understanding of this ecosystem component is still in its infancy. Adding to the complexity in knowledge building, ecosystems are exposed to simultaneous multiple shifts within global change scenarios. For example, semiarid grasslands in southern Arizona are currently undergoing encroachment by woody plants at the same time that climate change models predict increases in frequency and magnitude of precipitation inputs over the next 50 years. We investigated how the size of precipitation pulse events influences soil community structure and ecosystem C cycling. Large and small precipitation pulses were added to Sporobulus wrightii plots that were in canopy patches of Prosopis velutina, or in intercanopy areas. Plots influenced by Prosopis reflected increased quantity and quality of litter inputs to the soil component. Plant species influenced the response of soil microbial biomass to precipitation pulse size, with both the magnitude and duration of response being greater in the soils under Prosopis trees. Additionally, whole-soil phospholipid fatty acid (PLFA) analyses indicated that precipitation inputs shifted the composition of the soil microbial community. Nematode abundance also responded to pulse size, suggesting that larger precipitation events will bring more fauna out of cyptobiotic resting stages. These shifts in soil flora and fauna have important implications for ecosystem C-cycling via alterations of trophic dynamics, and the contribution of heterotrophic respiration to C efflux from ecosystems. These results suggest that plant litter inputs to the soil mediate the response of soil flora and fauna to size and frequency characteristics of precipitation regimes. Additionally, ecosystem response to precipitation may be related to the duration of different processes, rather than the maximum activity of those processes.
Key words: soil food webs, woody plant encroachment, carbon cycling, global change
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