02375nas a2200145   4500008004100000245016300041210006900204300001500273490000700288520181600295653002202111100001602133700001802149856006202167       2015                        eng d00aAnnual burning of a tallgrass prairie inhibits C and N cycling in soil, increasing recalcitrant pyrogenic organic matter storage while reducing N availability0 aAnnual burning of a tallgrass prairie inhibits C and N cycling i  a2321 -23330 v213 a<p>Grassland ecosystems store an estimated 30% of the world&#39;s total soil C and are frequently disturbed by wildfires or fire management. Aboveground litter decomposition is one of the main processes that form soil organic matter (SOM). However, during a fire biomass is removed or partially combusted and litter inputs to the soil are substituted with inputs of pyrogenic organic matter (py-OM). Py-OM accounts for a more recalcitrant plant input to SOM than fresh litter, and the historical frequency of burning may alter C and N retention of both fresh litter and py-OM inputs to the soil. We compared the fate of these two forms of plant material by incubating 13C- and 15N-labeled Andropogon gerardii litter and py-OM at both an annually burned and an infrequently burned tallgrass prairie site for 11 months. We traced litter and py-OM C and N into uncomplexed and organo-mineral SOM fractions and CO2 fluxes and determined how fire history affects the fate of these two forms of aboveground biomass. Evidence from CO2 fluxes and SOM C:N ratios indicates that the litter was microbially transformed during decomposition while, besides an initial labile fraction, py-OM added to SOM largely untransformed by soil microbes. Additionally, at the N-limited annually burned site, litter N was tightly conserved. Together, these results demonstrate how, although py-OM may contribute to C and N sequestration in the soil due to its resistance to microbial degradation, a long history of annual removal of fresh litter and input of py-OM infers N limitation due to the inhibition of microbial decomposition of aboveground plant inputs to the soil. These results provide new insight into how fire may impact plant inputs to the soil, and the effects of py-OM on SOM formation and ecosystem C and N cycling.</p>10atallgrass prairie1 aSoong, J.L.1 aCotrufo, M.F.  uhttps://onlinelibrary.wiley.com/doi/abs/10.1111/gcb.1283202223nas a2200253   4500008004100000022001400041245009500055210006900150260001600219300001400235490000600249520143500255653002001690653002801710653002801738100001801766700002401784700002301808700002601831700001501857700002001872700002401892856005301916       2015                        eng d  a1752-089400aFormation of soil organic matter via biochemical and physical pathways of litter mass loss0 aFormation of soil organic matter via biochemical and physical pa  cJul-09-2015  a776 - 7790 v83 aSoil organic matter is the largest terrestrial carbon pool1. The pool size depends on the balance between formation of soil organic matter from decomposition of plant litter and its mineralization to inorganic carbon. Knowledge of soil organic matter formation remains limited2 and current C numerical models assume that stable soil organic matter is formed primarily from recalcitrant plant litter3. However, labile components of plant litter could also form mineral-stabilized soil organic matter4. Here we followed the decomposition of isotopically labelled above-ground litter and its incorporation into soil organic matter over three years in a grassland in Kansas, USA, and used laboratory incubations to determine the decay rates and pool structure of litter-derived organic matter. Early in decomposition, soil organic matter formed when non-structural compounds were lost from litter. Soil organic matter also formed at the end of decomposition, when both non-structural and structural compounds were lost at similar rates. We conclude that two pathways yield soil organic matter efficiently. A dissolved organic matter–microbial path occurs early in decomposition when litter loses mostly non-structural compounds, which are incorporated into microbial biomass at high rates, resulting in efficient soil organic matter formation. An equally efficient physical-transfer path occurs when litter fragments move into soil.10aBiogeochemistry10aEnvironmental chemistry10aStable isotope analysis1 aCotrufo, M.F.1 aSoong, Jennifer, L.1 aHorton, Andrew, J.1 aCampbell, Eleanor, E.1 aHaddix, L.1 aWall, Diana, H.1 aParton, William, J.  uhttp://www.nature.com/doifinder/10.1038/ngeo252003187nas a2200301   4500008004100000245014300041210006900184300001100253490000700264520225800271653003102529653001002560653001402570653000902584653001602593653002202609100001802631700001402649700002402663700001502687700001402702700001502716700001802731700002002749700001802769700001502787856008302802       2014                        eng d00aNaphthalene addition to soil surfaces: A feasible method to reduce soil micro-arthropods with negligible direct effects on soil C dynamics0 aNaphthalene addition to soil surfaces A feasible method to reduc  a21 -290 v743 a<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>10aFauna manipulation methods10aMites10aNematodes10aPLFA10aSpringtails10aStable C isotopes1 aCotrufo, M.F.1 aSoong, J.1 aVandegehuchte, M.L.1 aNgryen, T.1 aDenef, K.1 aShaw, E.A.1 aSylvain, Z.A.1 aTomasel, C.M.D.1 aNielsen, U.N.1 aWall, D.H.  uhttps://www.sciencedirect.com/science/article/pii/S0929139313002400?via%3Dihub