Location: Agroecosystem Management ResearchTitle: Mortality hotspots: nitrogen cycling in forest soils during vertebrate decomposition
|Keenan, Sarah - University Of Tennessee|
|Schaeffer, Sean - University Of Tennessee|
|Debruyn, Jennifer - University Of Tennessee|
Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2018
Publication Date: 3/20/2018
Citation: Keenan, S.W., Schaeffer, S.M., Jin, V.L., Debruyn, J.M. 2018. Mortality hotspots: nitrogen cycling in forest soils during vertebrate decomposition. Soil Biology and Biochemistry. 121:165-176.
Interpretive Summary: Animal mortality is an integral part of all ecosystems, and decomposing carcasses provide significant inputs of nutrients to the environment. These temporary patches stimulate local communities, resulting in enhanced cycling of nutrients, including carbon. Despite the fact that all animals die, the processes in these decomposition hotspots are poorly understood. Here we document the changes in soils during decomposition, revealing three distinct phases of biogeochemical activity. This work demonstrates the profound effects of mortality hotspots on C and N cycling a forest ecosystem, provides new insights into N biogeochemical processes, and highlights the dynamic nature of stable isotopes during decay.
Technical Abstract: Decomposing plants and animals fundamentally transform their surrounding environments, and serve as a critical source of limiting nutrients for macro- and micro-fauna. Animal mortality hotspots alter soil biogeochemical cycles, and these natural ephemeral nutrient patches are important for maintaining landscape heterogeneity and enriching local biodiversity. Soil nitrogen (N) enrichment associated with decomposing animals has been documented, but to date an integrated systems-level understanding of the fate and rates of N compound transformations is lacking. The goal of this study was to develop a holistic view of N biogeochemical cycling during vertebrate decay. Vertebrate decomposition significantly altered soil N cycling, and was divided into three main biogeochemical phases based on soil chemistry. Phase one included initial and early decay, distinguished by oxic soils with background C and N cycling rates. Fluid release and insect colonization during active and advanced decay, defined as phase two, stimulated soil microbial communities, particularly those able to degrade phospholipids and nucleic acids, resulting in anaerobic soils, [NH4+] 250 times greater and [CO2] ten times greater than background, and the highest 15N-enrichment rates. The final biogeochemical phase, encompassing the early and late skeletal decay stages, was characterized by enhanced nitrification and denitrification as evidenced by significantly enriched NO3-, dissolved organic nitrogen, and enhanced N2O release. As a result of decay and multiple synchronous processes, soil d15N was enriched by 6 to 10 ‰ above background, demonstrating the influence of decay on soil isotopic signatures. This work provides the first systems-level synthesis of N redistribution during animal decay and has significant implications for our understanding of nutrient turnover rates and dynamics in terrestrial ecosystems.