We conducted a systematic meta-analysis of soil bulk, mineral-associated, and particulate organic carbon (SOC, MAOC, and POC) responses to global environmental changes using two databases, the Web of Science Core Collection and the ProQuest Agricultural and Environmental Science Database. Search terms used Boolean combinations of SOC terms and global change terms to target studies that employed both a global change experiment and SOC fractionation. Studies were limited to those in English. We considered nitrogen (N) fertilization, warming, elevated carbon dioxide (CO2), increased precipitation, and drought as global environmental changes. Studies that addressed multiple global change factors were retrieved from searches for individual global change factors. We included any soil depth, study environment (greenhouse, field, laboratory), and land cover type (cropland, grasslands, forests) to maximize the amount of data. We acknowledge that N fertilization is often integral to cropland management. However, we refer to N fertilization as a global change also in croplands since we evaluate SOC pool responses with and without N fertilization, such that the premise is the same, regardless of the system. With this search criteria, we retrieved 3,378 studies, which we then filtered in two ways. First, we analyzed abstracts of all studies and kept those that met the following criteria: (1) they were primary literature (not reviews, meta-analyses, or book chapters), (2) they appeared to measure SOC fractions that were physically separated as, or could be combined to, MAOC and POC, as explained below, (3) they measured the response of POC and/or MAOC and SOC to a global change factor with a control that was not treated with that global change factor, and (4) they were not duplicate studies. Following this initial study filtering we were left with 168 total studies which included data for 216 individual global change experiments (since some studies addressed multiple global change factors).
Following initial filtering of the abstracts, we downloaded full PDFs for all studies and performed a second filtering based on whether they met our quality criteria and MAOC and POC definitions, as follows. To be included in this study, SOC, MAOC, and/or POC needed to be measured for at least three replicates, to provide quality and robustness to our dataset. Soil had to be sieved to 2 mm or less and dispersed using either sonication, sodium hexametaphosphate, or shaking with glass beads such that aggregates would be adequately broken down. To be considered MAOC, the dispersed soil fraction had to be smaller than 50-63 μm, if separated by size, or heavier than 1.6-1.85 g cm-3, if separated by density. POC was defined as the complement to MAOC, such that dispersed soil fractions larger than 50-63 μm and lighter than 1.6-1.85 g cm-3 were considered POC. For more complex fractionations that still employed cutoffs for size and density defined above, fractions were summed to total MAOC and POC pools based on the above definitions. Heavy, coarse SOC fractions (i.e. greater than 1.6 g cm-3 and greater than 50-63 microm; typically less than 10% of total SOC) were added to the POC pool, due to their relatively fast turnover times that suggest lack of stabilization via mineral association.
We extracted data from tables using Tabula software (https://tabula.technology/) or from figures using the metaDigitize package in R. If crucial data were missing, we contacted authors and if no response was provided by May 2020 (after 2-3 attempts at contact) papers were removed from the analysis. If error type (standard deviation versus standard error) was not presented with the data, and the author did not respond, we assumed error type to be standard error, for more conservative error estimates. Following the second filtering, we were left with a final count of 605 observations from 98 total studies across the world ranging in publication years from 1994 to 2019, with 428 observations and 52 studies focusing on N fertilization, 42 observations and 15 studies on warming, 42 observations and 24 studies on elevated CO2, 18 observations and 5 studies on increased precipitation, and 57 observations and 17 studies that addressed multiple global change factors. For these final studies, we extracted data on soil organic matter C (SOC, MAOC, and POC; g C kg soil-1), global change factors (years under factor, level of factor, etc.), and environmental variables (soil type and depth, plant biomass, climate, etc.). Some data of interest, notably data for microbial activity and biomass, were not reported frequently enough to extract. Where only total soil C was reported and soil pH was below 7, we assumed inorganic carbon was negligible, and thus recorded total soil C as SOC. Two studies with soil pH above 7 did not clearly indicate separation of inorganic and organic C but these were not influential in our study, according to the sensitivity analysis. We only included reported fraction data and did not calculate fractions by difference (e.g. SOC-POC = MAOC), as this could produce errors due to incomplete or over-recovery during fractionation. Using only reported data led to different samples sizes for SOC, MAOC, and POC.
Data sources:
Allard V, Newton PCD, Lieffering M, Soussana JF, Carran RA, Matthew C (2005) Increased quantity and quality of coarse soil organic matter fraction at elevated CO2 in a grazed grassland are a consequence of enhanced root growth rate and turnover Plant and Soil 276:49-60 doi:10.1007/s11104-005-5675-9
Black CK, Davis SC, Hudiburg TW, Bernacchi CJ, DeLucia EH (2017) Elevated CO2 and temperature increase soil C losses from a soybean-maize ecosystem Global Change Biology 23:435-445 doi:10.1111/gcb.13378
Bock M, Glaser B, Millar N (2007) Sequestration and turnover of plant- and microbially derived sugars in a temperate grassland soil during 7 years exposed to elevated atmospheric pCO2 Global Change Biology 13:478-490 doi:http://dx.doi.org/10.1111/j.1365-2486.2006.01303.x
Borges BMMN, Mendes Coutinho EL, Silveira ML, Ricardo de Oliveira B (2019) Short-term impacts of high levels of nitrogen fertilization on soil carbon dynamics in a tropical pasture Catena 174:413-416 doi:http://dx.doi.org/10.1016/j.catena.2018.11.033
Bradford MA, Fierer N, Jackson RB, Maddox TR, Reynolds JF (2008a) Nonlinear root-derived carbon sequestration across a gradient of nitrogen and phosphorous deposition in experimental mesocosms Global Change Biology 14:1113-1124 doi:10.1111/j.1365-2486.2008.01564.x
Bradford MA, Fierer N, Reynolds JF (2008b) Soil carbon stocks in experimental mesocosms are dependent on the rate of labile carbon, nitrogen and phosphorus inputs to soils Functional Ecology 22:964-974 doi:10.1111/j.1365-2435.2008.01404.x
Bremer E, Janzen H, Ellert B, McKenzie R (2008) Soil organic carbon after twelve years of various crop rotations in an Aridic Boroll Soil Science Society of America Journal 72:970-974
Bremer E, Janzen HH, Johnston AM (1994) Sensitivity of total, light fraction and mineralizable organic matter to management practices in a Lethbridge soil Canadian Journal of Soil Science 74:131-138
Chen GT, Tu LH, Chen GS, Hu JY, Han ZL (2018) Effect of six years of nitrogen additions on soil chemistry in a subtropical Pleioblastus amarus forest, Southwest China Journal of Forestry Research 29:1657-1664 doi:10.1007/s11676-017-0587-0
Chen X, Liu J, Deng Q, Yan J, Zhang D (2012a) Effects of elevated CO2 and nitrogen addition on soil organic carbon fractions in a subtropical forest Plant and Soil 357:25-34 doi:http://dx.doi.org/10.1007/s11104-012-1145-3
Chen XM, Liu JX, Deng Q, Yan JH, Zhang DQ (2012b) Effects of elevated CO2 and nitrogen addition on soil organic carbon fractions in a subtropical forest Plant and Soil 357:25-34 doi:10.1007/s11104-012-1145-3
Cheng S, Fang H, Xu M, Geng J, He S, Yu G, Cao Z (2018) Regulation of plant-soil-microbe interactions to soil organic carbon in natural ecosystems under elevated nitrogen deposition: A review Shengtai Xuebao = Acta Ecologica Sinica:8285
Cheng X, Luo Y, Xu X, Sherry R, Zhang Q (2011) Soil organic matter dynamics in a North America tallgrass prairie after 9 yr of experimental warming Biogeosciences 8:1487
Coulter JA, Nafziger ED, Wander MM (2009) Soil Organic Matter Response to Cropping System and Nitrogen Fertilization Agronomy journal 101:592-599 doi:http://dx.doi.org/10.2134/agronj2008.0152x
Cui S et al. (2014) Carbon and nitrogen responses of three old world bluestems to nitrogen fertilization or inclusion of a legume Field Crops Research 164:45-53 doi:10.1016/j.fcr.2014.05.011
Cusack DF, Silver WL, Torn MS, McDowell WH (2011) Effects of nitrogen additions on above-and belowground carbon dynamics in two tropical forests Biogeochemistry 104:203-225
De Feudis M et al. (2019) Small altitudinal change and rhizosphere affect the SOM light fractions but not the heavy fraction in European beech forest soil Catena 181 doi:http://dx.doi.org/10.1016/j.catena.2019.104091
Dorodnikov M, Kuzyakov Y, Fangmeier A, Wiesenberg GLB (2011) C and N in soil organic matter density fractions under elevated atmospheric CO2: Turnover vs. stabilization Soil Biology & Biochemistry 43:579-589 doi:10.1016/j.soilbio.2010.11.026
Dou FG, Hons FM (2006) Tillage and nitrogen effects on soil organic matter fractions in wheat-based systems Soil Science Society of America Journal 70:1896-1905 doi:10.2136/sssaj2005.0229
Fang XM, Chen FS, Hu XF, Yuan PC, Li J, Chen X (2014) Aluminum and nutrient interplay across an age-chronosequence of tea plantations within a hilly red soil farm of subtropical China Soil Science and Plant Nutrition 60:448-459 doi:10.1080/00380768.2014.912950
Ferreira GWD, Oliveira FCC, Silva LOG, Souza J, Soares EMB, Araujo EF, Silva IR (2018) Nitrogen Alters Initial Growth, Fine-Root Biomass and Soil Organic Matter Properties of a Eucalyptus dunnii Maiden Plantation in a Recently Afforested Grassland in Southern Brazil Forests 9 doi:10.3390/f9020062
Finn D, Robertson F, Page K, Catton K, Kienzle M, Dalal R, Armstrong R (2016) Ecological stoichiometry controls the transformation and retention of plant-derived organic matter to humus in response to nitrogen fertilisation Soil biology & biochemistry 99:117-127 doi:http://dx.doi.org/10.1016/j.soilbio.2016.05.006
Frasier I, Noellemeyer E, Figuerola E, Erijman L, Permingeat H, Quiroga A (2016) High quality residues from cover crops favor changes in microbial community and enhance C and N sequestration Global Ecology and Conservation 6:242-256 doi:10.1016/j.gecco.2016.03.009
Garten CT, Classen AT, Norby RJ (2009) Soil moisture surpasses elevated CO2 and temperature as a control on soil carbon dynamics in a multi-factor climate change experiment Plant and Soil 319:85-94 doi:http://dx.doi.org/10.1007/s11104-008-9851-6
Griepentrog M, Eglinton TI, Hagedorn F, Schmidt MWI, Wiesenberg GLB (2015) Interactive effects of elevated CO2 and nitrogen deposition on fatty acid molecular and isotope composition of above- and belowground tree biomass and forest soil fractions Global change biology 21:473-486 doi:http://dx.doi.org/10.1111/gcb.12666
Guan S, Zhang J, An N, He N, Zong N, Shi P, He Y (2018) Climate warming impacts on soil organic carbon fractions and aggregate stability in a Tibetan alpine meadow Soil biology & biochemistry 116:224-236 doi:http://dx.doi.org/10.1016/j.soilbio.2017.10.011
Hagedorn F, Spinnler D, Siegwolf R (2003) Increased N deposition retards mineralization of old soil organic matter Soil Biology & Biochemistry 35:1683-1692 doi:10.1016/j.soilbio.2003.08.015
Haile-Mariam S, Cheng W, Johnson DW, Ball JT, Paul EA (2000) Use of carbon-13 and carbon-14 to measure the effects of carbon dioxide and nitrogen fertilization on carbon dynamics in ponderosa pine Soil Science Society of America journal 64:1984-1993
He NP, Chen QS, Han XG, Yu GR, Li LH (2012) Warming and increased precipitation individually influence soil carbon sequestration of Inner Mongolian grasslands, China Agriculture Ecosystems & Environment 158:184-191 doi:10.1016/j.agee.2012.06.010
Henry HAL, Juarez JD, Field CB, Vitousek PM (2005) Interactive effects of elevated CO2, N deposition and climate change on extracellular enzyme activity and soil density fractionation in a California annual grassland Global Change Biology 11:1808-1815 doi:10.1111/j.1365-2486.2005.001007.x
Hofmockel KS, Zak DR, Moran KK, Jastrow JD (2011) Changes in forest soil organic matter pools after a decade of elevated CO2 and O-3 Soil Biology & Biochemistry 43:1518-1527 doi:10.1016/j.soilbio.2011.03.030
Hoosbeek MR, Scarascia-Mugnozza GE (2009) Increased Litter Build Up and Soil Organic Matter Stabilization in a Poplar Plantation After 6 Years of Atmospheric CO(2) Enrichment (FACE): Final Results of POP-EuroFACE Compared to Other Forest FACE Experiments Ecosystems 12:220-239 doi:http://dx.doi.org/10.1007/s10021-008-9219-z
Insam H et al. (1999) Responses of the soil microbiota to elevated CO2 in an artificial tropical ecosystem Journal of Microbiological Methods 36:45-54 doi:10.1016/s0167-7012(99)00010-x
Iversen CM, Keller JK, Garten CT, Norby RJ (2012) Soil carbon and nitrogen cycling and storage throughout the soil profile in a sweetgum plantation after 11 years of CO2-enrichment Global Change Biology 18:1684-1697 doi:http://dx.doi.org/10.1111/j.1365-2486.2012.02643.x
Jantalia CP, Halvorson AD (2011) Nitrogen Fertilizer Effects on Irrigated Conventional Tillage Corn Yields and Soil Carbon and Nitrogen Pools Agronomy journal 103:871-878 doi:http://dx.doi.org/10.2134/agronj2010.0455
Jastrow J, Miller R, Owensby C (2000) Long-term effects of elevated atmospheric CO2 on below-ground biomass and transformations to soil organic matter in grassland Plant and Soil 224:85-97 doi:http://dx.doi.org/10.1023/A:1004771805022
Lagomarsino A, Grego S, Marhan S, Moscatelli MC, Kandeler E (2009) Soil management modifies micro-scale abundance and function of soil microorganisms in a Mediterranean ecosystem European Journal of Soil Science 60:2-12 doi:10.1111/j.1365-2389.2008.01113.x
Li Z, Li D, Ma L, Yu Y, Zhao B, Zhang J (2019) Effects of straw management and nitrogen application rate on soil organic matter fractions and microbial properties in North China Plain Journal of Soils and Sediments 19:618-628 doi:http://dx.doi.org/10.1007/s11368-018-2102-4
Liang CH, Yin Y, Chen Q (2014) Dynamics of Soil Organic Carbon Fractions and Aggregates in Vegetable Cropping Systems Pedosphere 24:605-612 doi:10.1016/s1002-0160(14)60046-1
Lichter J, Barron SH, Bevacqua CE, Finzi AC, et al. (2005) SOIL CARBON SEQUESTRATION AND TURNOVER IN A PINE FOREST AFTER SIX YEARS OF ATMOSPHERIC CO2 ENRICHMENT Ecology 86:1835-1847
Liebig MA, Varvel GE, Doran JW, Wienhold BJ (2002) Crop sequence and nitrogen fertilization effects on soil properties in the western corn belt Soil Science Society of America journal 66:596-601 doi:http://dx.doi.org/10113/7978
Link SO, Smith JL, Halvorson JJ, Bolton H, Jr. (2003) A reciprocal transplant experiment within a climatic gradient in a semiarid shrub-steppe ecosystem: effects on bunchgrass growth and reproduction, soil carbon, and soil nitrogen Global change biology 9:1097-1105 doi:http://dx.doi.org/10.1046/j.1365-2486.2003.00647.x;
Liu EK, Yan CR, Mei XR, Zhang YQ, Fan TL (2013a) Long-Term Effect of Manure and Fertilizer on Soil Organic Carbon Pools in Dryland Farming in Northwest China Plos One 8 doi:10.1371/journal.pone.0056536
Liu FR, Zhang YM, Luo JX (2018) The effects of experimental warming and CO2 concentration doubling on soil organic carbon fractions of a montane coniferous forest on the eastern Qinghai-Tibetan Plateau European Journal of Forest Research 137:211-221 doi:10.1007/s10342-018-1100-9
Liu L, Zhang T, Gilliam FS, Gundersen P, Zhang W, Chen H, Mo JM (2013b) Interactive Effects of Nitrogen and Phosphorus on Soil Microbial Communities in a Tropical Forest Plos One 8 doi:10.1371/journal.pone.0061188
Ma HL, Zhu JG, Xie ZB, Liu G, Zeng Q (2009) Effects of increased residue biomass under elevated CO2 on carbon and nitrogen in soil aggregate size classes (rice-wheat rotation system, China) Canadian Journal of Soil Science 89:567-577 doi:10.4141/cjss08049
Maillard E et al. (2015) Carbon accumulates in organo-mineral complexes after long-term liquid dairy manure application Agriculture Ecosystems & Environment 202:108-119 doi:10.1016/j.agee.2014.12.013
Malhi SS, Lemke R (2007) Tillage, crop residue and N fertilizer effects on crop yield, nutrient uptake, soil quality and nitrous oxide gas emissions in a second 4-yr rotation cycle Soil & Tillage Research 96:269-283 doi:10.1016/j.still.2007.06.011
Malhi SS, Nyborg M, Solberg ED, McConkey B, Dyck M, Puurveen D (2011) Long-term straw management and N fertilizer rate effects on quantity and quality of organic C and N and some chemical properties in two contrasting soils in Western Canada Biology and Fertility of Soils 47:785-800 doi:10.1007/s00374-011-0587-8
Malhi SS, Wang ZH, Schnitzer M, Monreal CM, Harapiak JT (2005) Nitrogen fertilization effects on quality of organic matter in a grassland soil Nutrient Cycling in Agroecosystems 73:191-199 doi:10.1007/s10705-005-1702-8
Moinet GYK, Cieraad E, Hunt JE, Fraser A, Turnbull MH, Whitehead D (2016) Soil heterotrophic respiration is insensitive to changes in soil water content but related to microbial access to organic matter Geoderma 274:68-78 doi:http://dx.doi.org/10.1016/j.geoderma.2016.03.027
Mujuru L, Rusinamhodzi L, Nyamangara J, Hoosbeek MR (2016) Effects of nitrogen fertilizer and manure application on storage of carbon and nitrogen under continuous maize cropping in Arenosols and Luvisols of Zimbabwe Journal of Agricultural Science 154:242-257 doi:http://dx.doi.org/10.1017/S0021859615000520
Niklaus PA, Glockler E, Siegwolf R, Korner C (2001a) Carbon allocation in calcareous grassland under elevated CO2: a combined 13C pulse-labeling/soil physical fractionation study Functional ecology 15:43-50 doi:http://dx.doi.org/10.1046/j.1365-2435.2001.00485.x
Niklaus PA, Wohlfender M, Siegwolf R, Korner C (2001b) Effects of six years atmospheric CO2 enrichment on plant, soil, and soil microbial C of a calcareous grassland Plant and Soil 233:189-202 doi:10.1023/a:1010389724977
Oliveira FCC, Silva IR, Ferreira GWD, Soares EMB, Silva SR, Silva EF (2018) Contribution of Eucalyptus Harvest Residues and Nitrogen Fertilization to Carbon Stabilization in Ultisols of Southern Bahia Revista Brasileira De Ciencia Do Solo 42 doi:10.1590/18069657rbcs20160340
Parker JL, Fernandez IJ, Rustad LE, Norton SA (2002) Soil organic matter fractions in experimental forested watersheds Water Air and Soil Pollution 138:101-121 doi:10.1023/a:1015516607941
Pendall E, Osanai YUI, Williams AL, Hovenden MJ (2011) Soil carbon storage under simulated climate change is mediated by plant functional type Global Change Biology 17:505-514 doi:http://dx.doi.org/10.1111/j.1365-2486.2010.02296.x
Peralta AL, Wander MM (2008) Soil organic matter dynamics under soybean exposed to elevated CO2 Plant and Soil 303:69-81 doi:10.1007/s11104-007-9474-3
Poeplau C, Thomas Kt, Leblans NIW, Sigurdsson BD (2017) Sensitivity of soil carbon fractions and their specific stabilization mechanisms to extreme soil warming in a subarctic grassland Global change biology 23:1316-1327 doi:http://dx.doi.org/10.1111/gcb.13491
Puissant J et al. (2017) Climate change effects on the stability and chemistry of soil organic carbon pools in a subalpine grassland Biogeochemistry 132:123-139 doi:http://dx.doi.org/10.1007/s10533-016-0291-8
Purakayastha TJ, Rudrappa L, Singh D, Swarup A, Bhadraray S (2008) Long-term impact of fertilizers on soil organic carbon pools and sequestration rates in maize-wheat.-cowpea cropping system Geoderma 144:370-378 doi:10.1016/j.geoderma.2007.12.006
Qi RM et al. (2016) Temperature effects on soil organic carbon, soil labile organic carbon fractions, and soil enzyme activities under long-term fertilization regimes Applied Soil Ecology 102:36-45 doi:10.1016/j.apsoil.2016.02.004
Rodriguez A, Lovett GM, Weathers KC, Arthur MA, Templer PH, Goodale CL, Christenson LM (2014) Lability of C in temperate forest soils: Assessing the role of nitrogen addition and tree species composition Soil Biology & Biochemistry 77:129-140 doi:10.1016/j.soilbio.2014.06.025
Schnecker Jr, Schindlbacher A, Werner B, Wanek W (2016) Little effects on soil organic matter chemistry of density fractions after seven years of forest soil warming Soil biology & biochemistry 103:300-307 doi:http://dx.doi.org/10.1016/j.soilbio.2016.09.003
Shahbaz M, Kuzyakov Y, Shafique M, Wendland M, Heitkamp F (2017) Decadal Nitrogen Fertilization Decreases Mineral-Associated and Subsoil Carbon: A 32-Year Study Land degradation & development 28:1463-1472 doi:http://dx.doi.org/10.1002/ldr.2667
Silveira ML, João MBV, Liu K, Sollenberger LE, Follett RF (2013) Short-term effects of grazing intensity and nitrogen fertilization on soil organic carbon pools under perennial grass pastures in the southeastern USA Soil biology & biochemistry 58:42-49 doi:http://dx.doi.org/10.1016/j.soilbio.2012.11.003
Singh AK, Rai A, Kushwaha M, Chauhan PS, Pandey V, Singh N (2019) Tree growth rate regulate the influence of elevated CO2 on soil biochemical responses under tropical condition Journal of environmental management 231:1211-1221 doi:http://dx.doi.org/10.1016/j.jenvman.2018.11.025
Six J, Carpentier A, van Kessel C, Merckx R, Harris D, Horwath WR, Lüscher A (2001) Impact of elevated CO2 on soil organic matter dynamics as related to changes in aggregate turnover and residue quality Plant and Soil 234:27-36 doi:http://dx.doi.org/10.1023/A:1010504611456
Song B, Niu SL, Li LH, Zhang LX, Yu GR (2014) Soil carbon fractions in grasslands respond differently to various levels of nitrogen enrichments Plant and Soil 384:401-412 doi:10.1007/s11104-014-2219-1
Song B, Niu SL, Zhang Z, Yang HJ, Li LH, Wan SQ (2012) Light and Heavy Fractions of Soil Organic Matter in Response to Climate Warming and Increased Precipitation in a Temperate Steppe Plos One 7 doi:10.1371/journal.pone.0033217
Stewart CE, Follett RF, Pruessner EG, Varvel GE, Vogel KP, Mitchell RB (2016) N fertilizer and harvest impacts on bioenergy crop contributions to SOC Gcb Bioenergy 8:1201-1211
Stewart CE, Halvorson AD, Delgado JA (2017) Long-term N fertilization and conservation tillage practices conserve surface but not profile SOC stocks under semi-arid irrigated corn Soil & Tillage Research 171:9-18 doi:10.1016/j.still.2017.04.003
Stewart CE, Roosendaal DL, Manter DK, Delgado JA, Del Grosso S (2018) Interactions of stover and nitrogen management on soil microbial community and labile carbon under irrigated no-till corn Soil Science Society of America Journal 82:323-331
Swanston C, Homann PS, Caldwell BA, Myrold DD, Ganio L, Sollins P (2004) Long-term effects of elevated nitrogen on forest soil organic matter stability Biogeochemistry 70:229-252 doi:http://dx.doi.org/10.1023/B:BIOG.0000049341.37579.86
Thaysen EM, Reinsch S, Larsen KS, Ambus P (2017) Decrease in heathland soil labile organic carbon under future atmospheric and climatic conditions Biogeochemistry 133:17-36 doi:10.1007/s10533-017-0303-3
Tian J, Lu SH, Fan MS, Li XL, Kuzyakov Y (2013) Integrated management systems and N fertilization: effect on soil organic matter in rice-rapeseed rotation Plant and Soil 372:53-63 doi:10.1007/s11104-013-1715-z
Van Groenigen KJ, Harris D, Horwath WR, Hartwig UA, Van Kessel C (2002) Linking sequestration of C-13 and N-15 in aggregates in a pasture soil following 8 years of elevated atmospheric CO2 Global Change Biology 8:1094-1108 doi:10.1046/j.1365-2486.2002.00527.x
Volk M, Bassin S, Lehmann MF, Johnson MG, Andersen CP (2018) C-13 isotopic signature and C concentration of soil density fractions illustrate reduced C allocation to subalpine grassland soil under high atmospheric N deposition Soil Biology & Biochemistry 125:178-184 doi:10.1016/j.soilbio.2018.07.014
Wang RZ et al. (2019a) Response of soil carbon to nitrogen and water addition differs between labile and recalcitrant fractions: Evidence from multi-year data and different soil depths in a semi-arid steppe Catena 172:857-865 doi:10.1016/j.catena.2018.08.034
Wang X, Jelinski NA, Toner B, Yoo K (2019b) Long-term agricultural management and erosion change soil organic matter chemistry and association with minerals Science of the Total Environment 648:1500-1510 doi:10.1016/j.scitotenv.2018.08.110
Xie ZB, Cadisch G, Edwards G, Baggs EM, Blum H (2005) Carbon dynamics in a temperate grassland soil after 9 years exposure to elevated CO2 (Swiss FACE) Soil Biology & Biochemistry 37:1387-1395 doi:10.1016/j.soilbio.2004.12.010
Xu Q, Tang C, Jin J, Armstrong R, Wang X (2019) Susceptibility of soil organic carbon to priming after long-term CO2 fumigation is mediated by soil texture Science of the total environment 657:1112-1120 doi:http://dx.doi.org/10.1016/j.scitotenv.2018.11.437
Yang K, Zhu JJ, Gu JC, Xu S, Yu LZ, Wang ZQ (2018) Effects of continuous nitrogen addition on microbial properties and soil organic matter in a Larix gmelinii plantation in China Journal of Forestry Research 29:85-92 doi:10.1007/s11676-017-0430-7
Yanni SF, Janzen HH, Gregorich EG, Ellert BH, Larney FJ, Olson BM, Zvomuya F (2016) Organic Carbon Convergence in Diverse Soils toward Steady State: A 21-Year Field Bioassay Soil Science Society of America Journal 80:1653-1662 doi:10.2136/sssaj2016.07.0214
Zak DR, Freedman ZB, Upchurch RA, Steffens M, Kogel-Knabner I (2017) Anthropogenic N deposition increases soil organic matteraccumulation without altering its biochemical composition Global Change Biology 23:933-944 doi:10.1111/gcb.13480
Zhang CH, Tang GY, Sun YY (2019) Asymmetric and Symmetric Warming Induced Stability of Organic Carbon in a Calcareous Soil Soil Science Society of America Journal 83:1200-1208 doi:10.2136/sssaj2018.11.0444
Zhong YQW, Yan WM, Shangguan ZP (2015) Soil carbon and nitrogen fractions in the soil profile and their response to long-term nitrogen fertilization in a wheat field Catena 135:38-46 doi:10.1016/j.catena.2015.06.018
