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Interactions between earthworms and mesofauna has no significant effect on emissions of CO2 and N2O from soil
Soil Biology & Biochemistry 88 (2015) 294e297
Contents lists available at ScienceDirect
Soil Biology & Biochemistry journal homepage: www.elsevier.com/locate/soilbio
Short communication
Interactions between earthworms and mesofauna has no significant effect on emissions of CO2 and N2O from soil Haitao Wu*, Mingzhu Lu, Xianguo Lu, Qiang Guan, Xinhua He* Key Laboratory of Wetland Ecology and Environment, Institute of Northeast Geography and Agroecology, Chinese Academy of Sciences, Changchun, Jilin 130012, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 8 January 2015 Received in revised form 1 May 2015 Accepted 1 June 2015 Available online 17 June 2015
Soil fauna can significantly affect soil CO2 and N2O emissions, but little is known about interactions between faunal groups and their relative contribution to such emissions. Over a 64-day microcosm incubation, we studied the effects of an epigeic earthworm (Eisenia fetida), mesofauna (Collembola plus oribatid mites) and their combinations on soil CO2 and N2O emissions under two faunal densities. Earthworms significantly enhanced soil CO2 and N2O emissions, while mesofauna only increased N2O emissions. Soil CO2 and N2O emissions were significantly affected by earthworm density, but not by mesofauna density. No significant interactive effects between earthworms and mesofauna were found on soil CO2 and N2O emissions. Our results indicate that earthworms probably play the dominant roles in determining soil CO2 and N2O emissions where they coexist with soil mesofauna. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Carbon Greenhouse gas Interaction Nitrogen cycling Soil fauna
Soils act as important sources or sinks for carbon dioxide (CO2) and nitrous oxide (N2O), both well-known greenhouse gases. Globally, ~20% of CO2 and 62% of N2O emissions originate from soils (Rastogi et al., 2002; IPCC, 2007). Soil fauna can either suppress, delay, increase or accelerate soil CO2 and N2O emissions depending on the group through their effects on the processes of decomposition, nitrification and denitrification (Frouz et al., 2007; Kuiper et al., 2013; Wu et al., 2013). Numerous studies have confirmed that earthworms affect soil CO2 and N2O emissions (Rizhiya et al., 2007; Chapuis-Lardy et al., 2010; Giannopoulos et al., 2010; Lubbers et al., 2013; Frouz et al., 2014), through their direct and indirect impacts on the soil environment, the quality of resources and microbial processes (Drake and Horn, 2006; Speratti and Whalen, 2008; Nebert et al., 2011; Lubbers et al., 2013). A small number of studies have also shown effects of mesofauna, such as Collembola and Acarina, on soil CO2 emissions (Fox et al., 2006; Wickings and Grandy, 2011), but very few studies measured N2O emissions. Little information is available on the interactive effects among soil faunal groups on soil CO2 and N2O emissions (Collison et al., 2013; Kuiper et al., 2013; Thakur et al., 2014). The objectives of this study
* Corresponding authors. 4888 Shengbei Street, Changchun, Jilin 130012, China. Tel.: þ86 431 85542272; fax: þ86 431 85542298. E-mail addresses: [email protected] (H. Wu), [email protected] (M. Lu), luxg@ iga.ac.cn (X. Lu), [email protected] (Q. Guan), [email protected] (X. He). http://dx.doi.org/10.1016/j.soilbio.2015.06.005 0038-0717/© 2015 Elsevier Ltd. All rights reserved.
were to assess the individual effects of earthworms and soil mesofauna, as well as their interactions on soil CO2 and N2O emissions, in a laboratory-based incubation experiment. Soil (Gleysol, FAO taxonomy, 3% sand, 48% silt, 49% clay, pH (CaCl2) 6.0; see Table 3), adult epigeic earthworms (Eisenia fetida, 0.9 ± 0.04 g fresh weight) and mesofauna (oribatid mites plus Collembola, see their extraction from Frouz et al., 2007) were collected in June 2010 from their natural community in an uninundated scrub-shrub wetland at the Sanjiang Mire Wetland Station (471300 500 N, 1331300100 E), Heilongjiang, China. Earthworms were voided for 48 h to clean their guts before introductions to microcosms (see Dalby et al., 1996). The Collembola genera included Ceratophysella, Friesea, Hypogastrura and Isotomurus, while the oribatid mite genera were Areozetes, Ceratozetes, Damaeus. and Scheloribates. A microcosm experiment modeled after Thakur et al. (2014) was conducted between June and August 2010. Sieved (2 mm) soils were defaunated (heated for 24 h at 65 C) (Kaneda and Kaneko, 2011) and then filled into Kilner jars (500 mL) with 104 g of airdried soil and packed to a bulk density of 0.52 g cm3. Soils were then adjusted to 60% water filled pore space (WFPS). Soil microcosms were pre-incubated at 20 C and 60% humidity for 3 days (maintained by distilled water every 2 days) to facilitate microbial colonization in an environment-controlled chamber. Then, earthworms, mites and Collembola were added to the soils (Table 1) with
H. Wu et al. / Soil Biology & Biochemistry 88 (2015) 294e297 Table 1 Introduction density of fauna in treatments after soil pre-incubation in microcosms. E, earthworm of Eisenia fetida; Meso, mesofauna as oribatid mites (Acari: Oribatid) plus springtails (Collembola). Treatment
Faunal density Mite þ Springtail
Earthworm
Control E1 E3 Meso1 Meso3 E1 þ Meso1 E3 þ Meso3
# microcosm1
# m2
# microcosm1
# m2
e 1 3 e e 1 3
e 52 156 e e 52 156
e e
e e
80 þ 60 240 þ 180 80 þ 60 240 þ 180
4160 þ 3120 12480 þ 9360 4160 þ 3120 12480 þ 9360
seven replicates per treatment (three for gas flux, and four for faunal extractions and soil analyses). Seven treatments were included as showed in Table 1. Microcosms were incubated under the same conditions with pre-incubation over 64 days. The septum seals in Kilner jar lids were kept open between sampling dates, and microcosms were covered with woven black cloth to allow gaseous exchange while preventing faunal escape. No food was added to the microcosm system over the incubation (64 days). Extracted CO2 and N2O were analyzed using gas chromatography (Agilent 4890, California, USA) accorded to Wu et al. (2015). Fluxes were calculated by assuming a linear increase of CO2 and N2O within a jar during the closing period. Cumulative CO2 and N2O emissions were estimated assuming linear changes between subsequent flux measurements (Giannopoulos et al., 2010). Analyses of soil total C, total N, NO 3,
295
NHþ 4 , DOC, microbial biomass carbon (MBC) and nitrogen (MBN) were as per Wu et al. (2015). The faunal contributions to N2O and CO2 fluxes were taken as the differences between a faunal treatment minus the control. Data (means ± SE, n ¼ 3 or 4) were subjected to ANOVA and significant differences between treatments were compared with the Tukey test at P ¼ 0.05 with the SPSS 21.0 package. The interactive effects between earthworm and mesofauna on CO2 and N2O emissions were analyzed using a two-way ANOVA with the presence of earthworms or mesofauna as two independent factors. No dead or newly hatched earthworms were observed and fresh earthworm biomass decreased by 19.4e22.3% after 64-days incubation. Abundances of oribatid mites and collembolans decreased by 28.6e30.8% and 11.4e17.5%, respectively. However, no significant differences were found for the changing percentages for earthworm weight losses and mesofauna density decreases between treatments. Earthworms significantly enhanced both soil CO2 (F ¼ 29.5, P < 0.01) and N2O (F ¼ 21.2, P < 0.01) emission rates, while mesofauna only increased N2O emissions (F ¼ 14.8, P < 0.05), compared with the control (Table 2). The contributions to CO2 and N2O emissions were generally greater for earthworms than for mesofauna (Table 2). The earthworm-induced increases in CO2 fluxes (38.2e106%, Table 2) were comparable to other studies (ChapuisLardy et al., 2010; Paul et al., 2012; Crumsey et al., 2013). However, the 139e386% enhancements to soil N2O emissions were higher than previous studies (Giannopoulos et al., 2010; Lubbers et al., 2013), which was probably due to the relatively high N concentration (6.1 g kg1 DW) in our soils (Table 3). In agreement with Kuiper et al. (2013), no significant effects of mesofauna on CO2
Table 2 Effects of fauna on mean CO2 and N2O emission rates over a 64-day microcosm incubation. Fauna effect is the difference between the mean gas emission rates of the fauna treatment and control. Values (means ± SE, n ¼ 36) followed by the same letter within a column are not statistically different at P < 0.05. Abbreviations see treatment details in Table 1. CO2 (mg C kg soil1 h1)
Treatment
Control E1 E3 Meso1 Meso3 E1 þ Meso1 E3 þ Meso3 ANOVA (One-way) ANOVA (Two-way): Earthworm Mesofauna Earthworm Mesofauna
N2O (mg N kg soil1 h1)
CO2 mean flux
Fauna-induced increase (%)
N2O mean flux
Fauna-induced increase (%)
2.92 ± 0.26c 4.01 ± 0.38b 5.98 ± 0.65a 3.22 ± 0.30c 3.25 ± 0.28c 4.25 ± 0.33b 6.19 ± 0.69a <0.001***
e 38.2 ± 5.91b 106 ± 12.5a 9.67 ± 3.46c 10.2 ± 2.01c 48.0 ± 5.44b 114 ± 14.2a <0.001***
0.34 ± 0.09e 0.81 ± 0.16c 1.66 ± 0.31b 0.51 ± 0.11d 0.59 ± 0.12d 0.95 ± 0.17c 1.94 ± 0.38a <0.001***
e 139 ± 23.6b 386 ± 53.5a 60.6 ± 8.99c 73.5 ± 15.0c 179 ± 33.5b 469 ± 46.3a <0.001***
<0.001*** 0.052 0.712
Levels of significance: *<0.05;
**
<0.01;
***
<0.001*** <0.001*** 0.595
<0.001.
Table 3 Soil chemical properties in microcosms on day 1 and 64. Values (means ± SE, n ¼ 4) followed by the same letter within a column are not statistically different at P < 0.05.
Day 1 Day 64 Control E1 E3 Meso1 Meso3 E1 þ Meso1 E3 þ Meso3 ANOVA
TC (%)
DOC (mg kg1)
TN (g kg1)
1 NO 3 (mg kg )
1 NHþ ) 4 (mg kg
MBC (mg kg1)
MBN (mg kg1)
7.5 ± 0.1
472 ± 16
6.1 ± 0.2
55 ± 1
11.2 ± 0.2
nd
nd
247 ± 346 ± 319 ± 360 ± 356 ± 303 ± 305 ± <0.05
6.0 5.8 5.9 6.1 6.0 5.8 6.4 ns
± ± ± ± ± ± ±
118 ± 193 ± 283 ± 190 ± 174 ± 208 ± 275 ± <0.05
9.6 ± 0.4d 11.3 ± 0.1c 27.0 ± 3.1b 12.2 ± 0.9c 11.5 ± 1.0c 11.4 ± 0.1c 53.9 ± 9.1a <0.05
519 ± 549 ± 604 ± 800 ± 822 ± 643 ± 648 ± <0.05
7.1 7.3 7.4 7.1 7.2 7.2 7.4 ns
± ± ± ± ± ± ±
0.1 0.1 0.5 0.0 0.1 0.3 0.1
5c 20a 1a 11a 8a 2b 9b
0.1 0.1 0.2 0.2 0.2 0.2 0.1
11c 15b 18a 35b 40b 10b 7a
27c 13c 21b 76a 47a 17b 12b
65.1 ± 2.7d 76.9 ± 3.8c 86.4 ± 8.7c 89.3 ± 9.1c 123 ± 4.3b 321 ± 7.8a 331 ± 2.2a <0.05
Abbreviations: DOC, dissolved organic carbon; MBC, microbial biomass carbon; MBN, microbial biomass nitrogen; nd, not determined; ns, statistically not significant; TC, total carbon, TN, total nitrogen. See treatment details in Table 1.
296
-1
CO2 cumulative emissions (mg CO2-C kg soil)
(A)
H. Wu et al. / Soil Biology & Biochemistry 88 (2015) 294e297
8000
Control E1 E3 Meso1 Meso3 E1+Meso1 E3+Meso3
7000 6000 5000
-1
N2O cumulative emissions (μg N2O-N kg soil)
b b c c c
4000 3000 2000
ANOVA (Two-way) *** Earthworm < 0.001
1000
Mesofauna 0.051 Earthworm × Mesofauna 0.450
Acknowledgments
0 0
(B)
effects on soil physicochemical characters (especially soil DOC, NO 3 and NHþ availabilities) and microbial activities (Table 3; 4 Blagodatsky and Smith, 2012; Kuiper et al., 2013; Thakur et al., 2014). Little is known about the interactive effects between earthworms and other soil fauna on soil gas emissions (Blouin et al., 2013). Our results suggested that interactions between earthworm and mesofauna has no significant effect on soil CO2 and N2O emissions, and that earthworm probably play the dominant roles in determining soil CO2 and N2O emissions where the groups coexist. These findings might thus indicate that the belowground process was indeed mainly driven by species identity among soil fauna (Heemsbergen et al., 2004; Collison et al., 2013).
a a
2100
1800
10
20
30
40
50
60
70
ANOVA (Two-way) *** Earthworm < 0.001 *** Mesofauna < 0.001
a
Earthworm × Mesofauna 0.444
b
This study was supported by projects from the National Natural Science Foundation of China (41171047 and 41371261), the Key Research Program of the Chinese Academy of Sciences (KZZD-EWTZ-16), and the Science and Technology Development Program of Jilin Province, China (20140101004JC). We thank Dr. Darold Batzer, Lynette Abbott, and two anonymous reviewers for their valuable comments and the assistances from all staff in the Sanjiang Mire Wetland Station.
1500
1200 c
References
900 c 600
d d e
300
0 0
10
20
30
40
50
60
70
Incubation days Fig. 1. Cumulative CO2 (A) and N2O (B) emissions over a 64-day microcosm incubation. Significance of the different fauna and their interactions are listed (*<0.05; **<0.01; *** <0.001). Values (means ± SE, n ¼ 3) on day 64 followed by the same letter are not statistically different at P < 0.05. Abbreviations see treatment details in Table 1.
efflux were observed, which might be attributed to their relatively low biomass (Filser, 2002). The 29.8e42.4% enhancement range of N2O emissions by mesofauna (Table 2) was consistent with those roles of mesofauna on soil N mineralization rates (Kaneda and Kaneko, 2011). The cumulative soil CO2 emissions from the earthworm þ mesofauna treatments were similar with those from earthworms alone, at the two densities (Fig. 1A). The cumulative N2O emissions from the earthworm þ mesofauna treatments were similar with those from earthworms alone at low densities (Fig. 1B). At high densities, the cumulative N2O emissions from the earthworm þ mesofauna treatments (E3 þ Meso3; 1.97 mg N kg1 DW soil) were significantly lower than the sum of earthworms alone (E3; 1.72 mg N kg1 DW soil) and mesofauna alone (Meso3; 0.59 mg N kg1 DW soil), although slightly higher than those under E3 (Fig. 1B). However, two-way ANOVA demonstrated no significant interactive effects existed between earthworms and mesofauna on soil CO2 and N2O emissions (Table 2, Fig. 1). The cumulative CO2 (F ¼ 22.3, P < 0.01) and N2O (F ¼ 18.9, P < 0.01) emissions were significantly affected by earthworm density, but not mesofauna density (Fig. 1). The differences among earthworms, mesofauna and their combinations on soil CO2 and N2O emissions probably resulted from their functional dissimilarities (Heemsbergen et al., 2004; Fox et al., 2006), and their different
Blagodatsky, S., Smith, P., 2012. Soil physics meets soil biology: towards better mechanistic prediction of greenhouse gas emissions from soil. Soil Biology & Biochemistry 47, 78e92. Blouin, M., Hodson, M.E., Delgado, E.A., Baker, G., Brussaard, L., Butt, K.R., Dai, J., Dendooven, L., Peres, G., Tondoh, J.E., Cluzeau, D., Brun, J.J., 2013. A review of earthworm impact on soil function and ecosystem services. European Journal of Soil Science 64, 161e182. Chapuis-Lardy, L., Brauman, A., Bernard, L., Pablo, A.L., Toucet, J., Mano, M.J., Weber, L., Brunet, D., Razafimbelo, T., Chotte, J.L., Blanchart, E., 2010. Effect of the endogeic earthworm Pontoscolex corethrurus on the microbial structure and activity related to CO2 and N2O fluxes from a tropical soil (Madagascar). Applied Soil Ecology 45, 201e208. Collison, E.J., Riutta, T., Slade, E.M., 2013. Macrofauna assemblage composition and soil moisture interact to affect soil ecosystem functions. Acta Oecologica 47, 30e36. Crumsey, J.M., Le Moine, J.M., Capowiez, Y., Goodsitt, M.M., Larson, S.C., Kling, G.W., Nadelhoffer, K.J., 2013. Community-specific impacts of exotic earthworm invasions on soil carbon dynamics in a sandy temperate forest. Ecology 94, 2827e2837. Dalby, P.R., Baker, G.H., Smith, S.E., 1996. ‘Filter paper method’ to remove soil from earthworm intestines and to standardise the water content of earthworm tissue. Soil Biology & Biochemistry 28, 685e687. Drake, H.L., Horn, M.A., 2006. Earthworms as a transient heaven for terrestrial denitrifying microbes: a review. Engineering in Life Sciences 6, 261e265. Filser, J., 2002. The role of Collembola in carbon and nitrogen cycling in soil. Pedobiologia 46, 234e245. Fox, O., Vetter, S., Ekschmitt, K., Wolters, V., 2006. Soil fauna modifies the recalcitrance-persistence relationship of soil carbon pools. Soil Biology & Biochemistry 38, 1353e1363. ova , A., Fri , K., Bartuska, M., 2014. The effect of earthworms Frouz, J., Spaldo n cova (Lumbricus rubellus) and simulated tillage on soil organic carbon in a long-term microcosm experiment. Soil Biology & Biochemistry 78, 58e64. , D., Pi Frouz, J., Elhottova zl, V., Tajovský, K., Sourkov a, M., Picek, T., Malý, S., 2007. The effect of litter quality and soil faunal composition on organic matter dynamics in post-mining soil: a laboratory study. Applied Soil Ecology 37, 72e80. Giannopoulos, G., Pulleman, M.M., Van Groenigen, J.W., 2010. Interactions between residue placement and earthworm ecological strategy affect aggregate turnover and N2O dynamics in agricultural soil. Soil Biology & Biochemistry 42, 618e625. Heemsbergen, D.A., Berg, M.P., Loreau, M., van Hal, J.R., Faber, J.H., Verhoef, H.A., 2004. Biodiversity effects on soil processes explained by interspecific functional dissimilarity. Science 306, 1019e1020. IPCC, 2007. In: Core Writing Team, Pachauri, R.K., Reisinger, A. (Eds.), Climate Change 2007: Synthesis Report. Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC, Geneva, Switzerland, 104 pp. Kaneda, S., Kaneko, N., 2011. Influence of Collembola on nitrogen mineralization varies with soil moisture content. Soil Science and Plant Nutrition 57, 40e49. Kuiper, I., De Deyn, G.B., Thakur, M.P., Van Groenigen, J.W., 2013. Soil invertebrate fauna affect N2O emissions from soil. Global Change Biology 19, 2814e2825.
H. Wu et al. / Soil Biology & Biochemistry 88 (2015) 294e297 Lubbers, I.M., van Groenigen, K.J., Fonte, S.J., Six, J., Brussaard, L., Van Groenigen, J.W., 2013. Greenhouse-gas emissions from soils increased by earthworms. Nature Climate Change 3, 187e194. Nebert, L.D., Bloem, J., Lubbers, I.M., Van Groenigen, J.W., 2011. Association of earthworm-denitrifier interactions with increased emission of nitrous oxide from soil mesocosms amended with crop residue. Applied and Environmental Microbiology 77, 4097e4104. Paul, B.K., Lubbers, I.M., Groenigen, J.W., 2012. Residue incorporation depth is a controlling factor of earthworm-induced nitrous oxide emissions. Global Change Biology 18, 1141e1151. Rastogi, M., Singh, S., Pathak, H., 2002. Emission of carbon dioxide from soil. Current Science 82, 510e518. Rizhiya, E., Bertora, C., Van Vliet, P.C.J., Kuikman, P.J., Faber, J.H., Van Groenigen, J.W., 2007. Earthworm activity as a determinant for N2O emission from crop residue. Soil Biology & Biochemistry 39, 2058e2069.
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Speratti, A.B., Whalen, J.K., 2008. Carbon dioxide and nitrous oxide fluxes from soil as influenced by anecic and endogeic earthworms. Applied Soil Ecology 38, 27e33. Thakur, M.P., Van Groenigen, J.W., Kuiper, I., De Deyn, G.B., 2014. Interactions between microbial-feeding and predatory soil fauna trigger N2O emissions. Soil Biology & Biochemistry 70, 256e262. Wickings, K., Grandy, A.S., 2011. The oribatid mite Scheloribates moestus (Acari: Oribatida) alters litter chemistry and nutrient cycling during decomposition. Soil Biology and Biochemistry 43, 351e358. Wu, H.T., Lu, X.G., Tong, S.Z., Batzer, D.P., 2015. Soil engineering ants increase CO2 and N2O emissions by affecting mound soil physicochemical characteristics from a marsh soil: a laboratory study. Applied Soil Ecology 87, 19e26. Wu, H.T., Lu, X.G., Wu, D.H., Song, L.H., Yan, X.M., Liu, J., 2013. Ant mounds alter spatial and temporal patterns of CO2, CH4 and N2O emissions from a marsh soil. Soil Biology & Biochemistry 57, 884e891.
Contents lists available at ScienceDirect
Soil Biology & Biochemistry journal homepage: www.elsevier.com/locate/soilbio
Short communication
Interactions between earthworms and mesofauna has no significant effect on emissions of CO2 and N2O from soil Haitao Wu*, Mingzhu Lu, Xianguo Lu, Qiang Guan, Xinhua He* Key Laboratory of Wetland Ecology and Environment, Institute of Northeast Geography and Agroecology, Chinese Academy of Sciences, Changchun, Jilin 130012, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 8 January 2015 Received in revised form 1 May 2015 Accepted 1 June 2015 Available online 17 June 2015
Soil fauna can significantly affect soil CO2 and N2O emissions, but little is known about interactions between faunal groups and their relative contribution to such emissions. Over a 64-day microcosm incubation, we studied the effects of an epigeic earthworm (Eisenia fetida), mesofauna (Collembola plus oribatid mites) and their combinations on soil CO2 and N2O emissions under two faunal densities. Earthworms significantly enhanced soil CO2 and N2O emissions, while mesofauna only increased N2O emissions. Soil CO2 and N2O emissions were significantly affected by earthworm density, but not by mesofauna density. No significant interactive effects between earthworms and mesofauna were found on soil CO2 and N2O emissions. Our results indicate that earthworms probably play the dominant roles in determining soil CO2 and N2O emissions where they coexist with soil mesofauna. © 2015 Elsevier Ltd. All rights reserved.
Keywords: Carbon Greenhouse gas Interaction Nitrogen cycling Soil fauna
Soils act as important sources or sinks for carbon dioxide (CO2) and nitrous oxide (N2O), both well-known greenhouse gases. Globally, ~20% of CO2 and 62% of N2O emissions originate from soils (Rastogi et al., 2002; IPCC, 2007). Soil fauna can either suppress, delay, increase or accelerate soil CO2 and N2O emissions depending on the group through their effects on the processes of decomposition, nitrification and denitrification (Frouz et al., 2007; Kuiper et al., 2013; Wu et al., 2013). Numerous studies have confirmed that earthworms affect soil CO2 and N2O emissions (Rizhiya et al., 2007; Chapuis-Lardy et al., 2010; Giannopoulos et al., 2010; Lubbers et al., 2013; Frouz et al., 2014), through their direct and indirect impacts on the soil environment, the quality of resources and microbial processes (Drake and Horn, 2006; Speratti and Whalen, 2008; Nebert et al., 2011; Lubbers et al., 2013). A small number of studies have also shown effects of mesofauna, such as Collembola and Acarina, on soil CO2 emissions (Fox et al., 2006; Wickings and Grandy, 2011), but very few studies measured N2O emissions. Little information is available on the interactive effects among soil faunal groups on soil CO2 and N2O emissions (Collison et al., 2013; Kuiper et al., 2013; Thakur et al., 2014). The objectives of this study
* Corresponding authors. 4888 Shengbei Street, Changchun, Jilin 130012, China. Tel.: þ86 431 85542272; fax: þ86 431 85542298. E-mail addresses: [email protected] (H. Wu), [email protected] (M. Lu), luxg@ iga.ac.cn (X. Lu), [email protected] (Q. Guan), [email protected] (X. He). http://dx.doi.org/10.1016/j.soilbio.2015.06.005 0038-0717/© 2015 Elsevier Ltd. All rights reserved.
were to assess the individual effects of earthworms and soil mesofauna, as well as their interactions on soil CO2 and N2O emissions, in a laboratory-based incubation experiment. Soil (Gleysol, FAO taxonomy, 3% sand, 48% silt, 49% clay, pH (CaCl2) 6.0; see Table 3), adult epigeic earthworms (Eisenia fetida, 0.9 ± 0.04 g fresh weight) and mesofauna (oribatid mites plus Collembola, see their extraction from Frouz et al., 2007) were collected in June 2010 from their natural community in an uninundated scrub-shrub wetland at the Sanjiang Mire Wetland Station (471300 500 N, 1331300100 E), Heilongjiang, China. Earthworms were voided for 48 h to clean their guts before introductions to microcosms (see Dalby et al., 1996). The Collembola genera included Ceratophysella, Friesea, Hypogastrura and Isotomurus, while the oribatid mite genera were Areozetes, Ceratozetes, Damaeus. and Scheloribates. A microcosm experiment modeled after Thakur et al. (2014) was conducted between June and August 2010. Sieved (2 mm) soils were defaunated (heated for 24 h at 65 C) (Kaneda and Kaneko, 2011) and then filled into Kilner jars (500 mL) with 104 g of airdried soil and packed to a bulk density of 0.52 g cm3. Soils were then adjusted to 60% water filled pore space (WFPS). Soil microcosms were pre-incubated at 20 C and 60% humidity for 3 days (maintained by distilled water every 2 days) to facilitate microbial colonization in an environment-controlled chamber. Then, earthworms, mites and Collembola were added to the soils (Table 1) with
H. Wu et al. / Soil Biology & Biochemistry 88 (2015) 294e297 Table 1 Introduction density of fauna in treatments after soil pre-incubation in microcosms. E, earthworm of Eisenia fetida; Meso, mesofauna as oribatid mites (Acari: Oribatid) plus springtails (Collembola). Treatment
Faunal density Mite þ Springtail
Earthworm
Control E1 E3 Meso1 Meso3 E1 þ Meso1 E3 þ Meso3
# microcosm1
# m2
# microcosm1
# m2
e 1 3 e e 1 3
e 52 156 e e 52 156
e e
e e
80 þ 60 240 þ 180 80 þ 60 240 þ 180
4160 þ 3120 12480 þ 9360 4160 þ 3120 12480 þ 9360
seven replicates per treatment (three for gas flux, and four for faunal extractions and soil analyses). Seven treatments were included as showed in Table 1. Microcosms were incubated under the same conditions with pre-incubation over 64 days. The septum seals in Kilner jar lids were kept open between sampling dates, and microcosms were covered with woven black cloth to allow gaseous exchange while preventing faunal escape. No food was added to the microcosm system over the incubation (64 days). Extracted CO2 and N2O were analyzed using gas chromatography (Agilent 4890, California, USA) accorded to Wu et al. (2015). Fluxes were calculated by assuming a linear increase of CO2 and N2O within a jar during the closing period. Cumulative CO2 and N2O emissions were estimated assuming linear changes between subsequent flux measurements (Giannopoulos et al., 2010). Analyses of soil total C, total N, NO 3,
295
NHþ 4 , DOC, microbial biomass carbon (MBC) and nitrogen (MBN) were as per Wu et al. (2015). The faunal contributions to N2O and CO2 fluxes were taken as the differences between a faunal treatment minus the control. Data (means ± SE, n ¼ 3 or 4) were subjected to ANOVA and significant differences between treatments were compared with the Tukey test at P ¼ 0.05 with the SPSS 21.0 package. The interactive effects between earthworm and mesofauna on CO2 and N2O emissions were analyzed using a two-way ANOVA with the presence of earthworms or mesofauna as two independent factors. No dead or newly hatched earthworms were observed and fresh earthworm biomass decreased by 19.4e22.3% after 64-days incubation. Abundances of oribatid mites and collembolans decreased by 28.6e30.8% and 11.4e17.5%, respectively. However, no significant differences were found for the changing percentages for earthworm weight losses and mesofauna density decreases between treatments. Earthworms significantly enhanced both soil CO2 (F ¼ 29.5, P < 0.01) and N2O (F ¼ 21.2, P < 0.01) emission rates, while mesofauna only increased N2O emissions (F ¼ 14.8, P < 0.05), compared with the control (Table 2). The contributions to CO2 and N2O emissions were generally greater for earthworms than for mesofauna (Table 2). The earthworm-induced increases in CO2 fluxes (38.2e106%, Table 2) were comparable to other studies (ChapuisLardy et al., 2010; Paul et al., 2012; Crumsey et al., 2013). However, the 139e386% enhancements to soil N2O emissions were higher than previous studies (Giannopoulos et al., 2010; Lubbers et al., 2013), which was probably due to the relatively high N concentration (6.1 g kg1 DW) in our soils (Table 3). In agreement with Kuiper et al. (2013), no significant effects of mesofauna on CO2
Table 2 Effects of fauna on mean CO2 and N2O emission rates over a 64-day microcosm incubation. Fauna effect is the difference between the mean gas emission rates of the fauna treatment and control. Values (means ± SE, n ¼ 36) followed by the same letter within a column are not statistically different at P < 0.05. Abbreviations see treatment details in Table 1. CO2 (mg C kg soil1 h1)
Treatment
Control E1 E3 Meso1 Meso3 E1 þ Meso1 E3 þ Meso3 ANOVA (One-way) ANOVA (Two-way): Earthworm Mesofauna Earthworm Mesofauna
N2O (mg N kg soil1 h1)
CO2 mean flux
Fauna-induced increase (%)
N2O mean flux
Fauna-induced increase (%)
2.92 ± 0.26c 4.01 ± 0.38b 5.98 ± 0.65a 3.22 ± 0.30c 3.25 ± 0.28c 4.25 ± 0.33b 6.19 ± 0.69a <0.001***
e 38.2 ± 5.91b 106 ± 12.5a 9.67 ± 3.46c 10.2 ± 2.01c 48.0 ± 5.44b 114 ± 14.2a <0.001***
0.34 ± 0.09e 0.81 ± 0.16c 1.66 ± 0.31b 0.51 ± 0.11d 0.59 ± 0.12d 0.95 ± 0.17c 1.94 ± 0.38a <0.001***
e 139 ± 23.6b 386 ± 53.5a 60.6 ± 8.99c 73.5 ± 15.0c 179 ± 33.5b 469 ± 46.3a <0.001***
<0.001*** 0.052 0.712
Levels of significance: *<0.05;
**
<0.01;
***
<0.001*** <0.001*** 0.595
<0.001.
Table 3 Soil chemical properties in microcosms on day 1 and 64. Values (means ± SE, n ¼ 4) followed by the same letter within a column are not statistically different at P < 0.05.
Day 1 Day 64 Control E1 E3 Meso1 Meso3 E1 þ Meso1 E3 þ Meso3 ANOVA
TC (%)
DOC (mg kg1)
TN (g kg1)
1 NO 3 (mg kg )
1 NHþ ) 4 (mg kg
MBC (mg kg1)
MBN (mg kg1)
7.5 ± 0.1
472 ± 16
6.1 ± 0.2
55 ± 1
11.2 ± 0.2
nd
nd
247 ± 346 ± 319 ± 360 ± 356 ± 303 ± 305 ± <0.05
6.0 5.8 5.9 6.1 6.0 5.8 6.4 ns
± ± ± ± ± ± ±
118 ± 193 ± 283 ± 190 ± 174 ± 208 ± 275 ± <0.05
9.6 ± 0.4d 11.3 ± 0.1c 27.0 ± 3.1b 12.2 ± 0.9c 11.5 ± 1.0c 11.4 ± 0.1c 53.9 ± 9.1a <0.05
519 ± 549 ± 604 ± 800 ± 822 ± 643 ± 648 ± <0.05
7.1 7.3 7.4 7.1 7.2 7.2 7.4 ns
± ± ± ± ± ± ±
0.1 0.1 0.5 0.0 0.1 0.3 0.1
5c 20a 1a 11a 8a 2b 9b
0.1 0.1 0.2 0.2 0.2 0.2 0.1
11c 15b 18a 35b 40b 10b 7a
27c 13c 21b 76a 47a 17b 12b
65.1 ± 2.7d 76.9 ± 3.8c 86.4 ± 8.7c 89.3 ± 9.1c 123 ± 4.3b 321 ± 7.8a 331 ± 2.2a <0.05
Abbreviations: DOC, dissolved organic carbon; MBC, microbial biomass carbon; MBN, microbial biomass nitrogen; nd, not determined; ns, statistically not significant; TC, total carbon, TN, total nitrogen. See treatment details in Table 1.
296
-1
CO2 cumulative emissions (mg CO2-C kg soil)
(A)
H. Wu et al. / Soil Biology & Biochemistry 88 (2015) 294e297
8000
Control E1 E3 Meso1 Meso3 E1+Meso1 E3+Meso3
7000 6000 5000
-1
N2O cumulative emissions (μg N2O-N kg soil)
b b c c c
4000 3000 2000
ANOVA (Two-way) *** Earthworm < 0.001
1000
Mesofauna 0.051 Earthworm × Mesofauna 0.450
Acknowledgments
0 0
(B)
effects on soil physicochemical characters (especially soil DOC, NO 3 and NHþ availabilities) and microbial activities (Table 3; 4 Blagodatsky and Smith, 2012; Kuiper et al., 2013; Thakur et al., 2014). Little is known about the interactive effects between earthworms and other soil fauna on soil gas emissions (Blouin et al., 2013). Our results suggested that interactions between earthworm and mesofauna has no significant effect on soil CO2 and N2O emissions, and that earthworm probably play the dominant roles in determining soil CO2 and N2O emissions where the groups coexist. These findings might thus indicate that the belowground process was indeed mainly driven by species identity among soil fauna (Heemsbergen et al., 2004; Collison et al., 2013).
a a
2100
1800
10
20
30
40
50
60
70
ANOVA (Two-way) *** Earthworm < 0.001 *** Mesofauna < 0.001
a
Earthworm × Mesofauna 0.444
b
This study was supported by projects from the National Natural Science Foundation of China (41171047 and 41371261), the Key Research Program of the Chinese Academy of Sciences (KZZD-EWTZ-16), and the Science and Technology Development Program of Jilin Province, China (20140101004JC). We thank Dr. Darold Batzer, Lynette Abbott, and two anonymous reviewers for their valuable comments and the assistances from all staff in the Sanjiang Mire Wetland Station.
1500
1200 c
References
900 c 600
d d e
300
0 0
10
20
30
40
50
60
70
Incubation days Fig. 1. Cumulative CO2 (A) and N2O (B) emissions over a 64-day microcosm incubation. Significance of the different fauna and their interactions are listed (*<0.05; **<0.01; *** <0.001). Values (means ± SE, n ¼ 3) on day 64 followed by the same letter are not statistically different at P < 0.05. Abbreviations see treatment details in Table 1.
efflux were observed, which might be attributed to their relatively low biomass (Filser, 2002). The 29.8e42.4% enhancement range of N2O emissions by mesofauna (Table 2) was consistent with those roles of mesofauna on soil N mineralization rates (Kaneda and Kaneko, 2011). The cumulative soil CO2 emissions from the earthworm þ mesofauna treatments were similar with those from earthworms alone, at the two densities (Fig. 1A). The cumulative N2O emissions from the earthworm þ mesofauna treatments were similar with those from earthworms alone at low densities (Fig. 1B). At high densities, the cumulative N2O emissions from the earthworm þ mesofauna treatments (E3 þ Meso3; 1.97 mg N kg1 DW soil) were significantly lower than the sum of earthworms alone (E3; 1.72 mg N kg1 DW soil) and mesofauna alone (Meso3; 0.59 mg N kg1 DW soil), although slightly higher than those under E3 (Fig. 1B). However, two-way ANOVA demonstrated no significant interactive effects existed between earthworms and mesofauna on soil CO2 and N2O emissions (Table 2, Fig. 1). The cumulative CO2 (F ¼ 22.3, P < 0.01) and N2O (F ¼ 18.9, P < 0.01) emissions were significantly affected by earthworm density, but not mesofauna density (Fig. 1). The differences among earthworms, mesofauna and their combinations on soil CO2 and N2O emissions probably resulted from their functional dissimilarities (Heemsbergen et al., 2004; Fox et al., 2006), and their different
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