@phdthesis {KNZ001651,
	title = {Moving beyond mass loss: advancing understanding about the fate of decomposing leaf litter and pyrogenic organic matter in the mineral soil},
	volume = {PhD Dissertation},
	year = {2014},
	school = {Colorado State University},
	type = {Ph.D. Thesis},
	address = {Fort Collins, CO},
	abstract = {<p>Leaf litter decomposition recycles the energy and nutrients fixed by plants during net primary productivity back to the soil and atmosphere from where they came. Traditionally, leaf litter decomposition studies have focused on litter mass loss rates, without consideration for where that mass ends up in the ecosystem. However, during litter decomposition by soil microbes a fraction of the litter mass lost is truly lost to the ecosystem as respired CO2, while another fraction remains in the ecosystem stored in the soil as soil organic matter (SOM). SOM is heterogeneous in composition, with various SOM pools remaining stored in the soil for time spans ranging from days to millennia depending on their biochemical and physical properties. Pyrogenic organic matter (py-OM) is the partially combusted plant residue left behind by fires, and has been found to contribute to long term SOM pools. SOM accounts for the largest terrestrial pool of carbon (C) in the global C cycle and stores nitrogen (N) and other nutrients for plant productivity. Therefore the formation of SOM during litter decomposition is critical to terrestrial C and N cycling and its feedback to global biogeochemical cycles. The focus of my dissertation is the study of leaf litter and py-OM decomposition, and quantitatively tracing how much decomposing litter and py-OM is used by soil microbes, how much is lost as CO2, and how much remains in the soil and contributes to SOM formation under different conditions. In order to best address my research questions, I first studied the methods of leaching of dissolved organic carbon (DOC) and 13C and 15N isotope labeling of plant material in the laboratory. Then, I conducted a laboratory incubation where I found that the amount of hot water extractable C and the lignocellulose index (Lignin/(lignin+cellulose)) can be used to predict DOM leaching, and the partitioning of C loss between DOC and CO2 from leaves and py-OM during decomposition. I also conducted two field studies using 13C and 15N labeled Andropogon gerardii leaf litter and py-OM to trace the fate of C and N losses during their decomposition in a fire affected tallgrass prairie, and understand the role of soil microarthropods in this process. I found that soil microarthropods increase the amount of leaf litter C that contributes to stabilized SOM formation during litter decomposition, by increasing litter inputs to the soil where they can be utilized by soil microbes. Finally, I found that frequent inputs of py-OM, rather than litter, due to annual burning of the tallgrass prairie alters the SOM formation process by removing relatively labile litter inputs to the soil and replacing it with py-OM that is unusable by soil microbes. Overall, my dissertation has focused on taking a mechanistic approach to understanding the process of litter and py-OM decomposition, and how their decomposition contributes to SOM formation and ecosystem CO2 fluxes. My results have helped to improve our understanding of terrestrial biogeochemistry, and the processes that control SOM formation during litter decomposition.</p>},
	keywords = {LTER-KNZ},
	url = {http://hdl.handle.net/10217/83819},
	author = {Soong, J.}
}
@article {KNZ001605,
	title = {Naphthalene addition to soil surfaces: A feasible method to reduce soil micro-arthropods with negligible direct effects on soil C dynamics},
	journal = {Applied Soil Ecology},
	volume = {74},
	year = {2014},
	pages = {21 -29},
	abstract = {<p>Soil fauna are a key component of soil biodiversity and a driver of soil functioning. While the importance of soil fauna is well recognized, quantitative estimates of the role of soil fauna on soil biogeochemical processes, such as plant litter decomposition, are limited by methodological constraints. The addition of naphthalene, a polycyclic aromatic hydrocarbon (C10H8), to suppress soil fauna has been used for decades in decomposition experiments, but its efficacy remains questioned. In fact, we lack a rigorous field assessment of the efficacy of naphthalene additions for soil fauna suppression and potential non-target effects on the soil microbial community and carbon cycling. We added naphthalene at a high rate (477 g m\&minus;2) monthly for 23 months on the bare soil surface of a tallgrass prairie. We determined the effect of such additions on the abundance of nematodes and micro-arthropods along the soil profile to a depth of 20 cm at 11, 16 and 23 months after initiating naphthalene application. We used the variation in the natural 13C abundance of the naphthalene (δ13C \&ndash; 25.5\&permil;) as compared to the native soil (δ13C \&sim; \&minus;17\&permil;) to quantify naphthalene contribution to soil CO2 efflux and microbial biomarkers (PLFA). Naphthalene addition significantly reduced the abundance of oribatid mites (\&minus;45\%), predatory mites (\&minus;52\%) and springtails (\&minus;49\%), but did not affect nematode abundance. The 13C abundance of a few Gram-negative (cy17:0, 18:1ω7c, 16:1ω7c), Gram-positive (a15:0, i15:0) and Actinobacteria (10Me-16:0, 10Me-18:0) PLFA markers decreased significantly in naphthalene treated plots, indicating bacterial utilization of naphthalene-derived C. Mixing models showed this contribution to be highly variable, with the highest naphthalene-C incorporation for Gram negative bacteria. Naphthalene-C was not incorporated in fungal PLFAs. This microbial utilization did not affect overall microbial abundance, community structure or activity, estimated as soil respiration. This experiment proves that naphthalene addition is a feasible method to reduce soil micro-arthropods in the field, with negligible direct effects on soil nematodes, microbial abundance and C dynamics.</p>},
	keywords = {LTER-KNZ, Fauna manipulation methods, Mites, Nematodes, PLFA, Springtails, Stable C isotopes},
	doi = {10.1016/j.apsoil.2013.09.008},
	url = {https://www.sciencedirect.com/science/article/pii/S0929139313002400?via\%3Dihub},
	author = {Cotrufo, M.F. and Soong, J. and Vandegehuchte, M.L. and Ngryen, T. and Denef, K. and Shaw, E.A. and Sylvain, Z.A. and Tomasel, C.M.D. and Nielsen, U.N. and Wall, D.H.}
}
