General Information
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| Title: | Interaction of soil fauna and plant litter composition on decomposition processes across the litter-soil interface |
| Identifier: | bball.3.3 |
| Abstract: |
Plant chemical composition and the soil community are known to influence litter and soil organic matter decomposition. Although these two factors are likely to interact, their mechanisms and outcomes of interaction are not well understood. Studies of their interactive effects are rare and usually focus on carbon dynamics of litter, while nutrient dynamics in the underlying soil have been ignored. Further, litter and soil are considered to constitute a decomposition continuum, but whether litter and soil ecosystems respond to litter identity and mixing in the same manner is unsure. In a field experiment utilizing 5 litter species spanning wide ranges of multiple quality parameters and their mixture, we investigated whether the effects of litter identity and mixing on mass loss, nutrient dynamics, and decomposer communities are consistent across the litter-soil interface. We restricted the access of larger soil animals to the soils underlying these litters to investigate the role of soil fauna (meso, macro) in determining the effect of surface-litter chemical composition on nitrogen mineralization and on the microfood web in mineral soils. Over six months we assessed litter mass and nitrogen loss, nitrogen mineralization rates in the soil, and litter and soil microbes and micro- and mesofauna. We found evidence that the structure of the soil community can alter the effect of surface litter chemical composition on nitrogen dynamics in the mineral soil, contribute to evidence demonstrating that soil fauna shape plant litter effects on ecosystem function. Decomposer communities and N dynamics did not respond similarly to the litter mixture across the litter-soil interface, demonstrate that processes associated with decomposition are decoupled for litter and soil, particularly in that litter showed non-additivity in mass loss, N release and decomposer community, but soil responses were largely additive.
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| Keywords: |
- Litter mixtures
- Litter quality
- Decomposition
- Decomposer community
- Soil fauna
- Mineralization
- Litter-soil continuum
- Nitrogen
- PLFA
- Bacteria
- Fungi
- Nematodes
- Microarthropods
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Involved Parties
Data Set Creators
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Individual: | Dr. Yolima Carrillo |
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Organization: | Department of Environmental Sciences, Faculty of Agriculture and Environment, University of Sydney |
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Individual: | Dr. Becky Ball |
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Organization: | School of Mathematical and Natural Sciences, Arizona State University at the West Campus |
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Address: |
| 4701 W. Thunderbird Rd., |
| Glendale, AZ 85306 USA |
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Email Address:
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Data Set Contacts
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Individual: | Dr. Yolima Carrillo |
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Organization: | Department of Environmental Sciences, Faculty of Agriculture and Environment, University of Sydney |
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Individual: | Dr. Becky Ball |
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Organization: | School of Mathematical and Natural Sciences, Arizona State University at the West Campus |
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Address: |
| 4701 W. Thunderbird Rd., |
| Glendale, AZ 85306 USA |
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Email Address:
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Data Set Characteristics
| Geographic Region: |
| Geographic Description: | The field study was conducted in a previously abandoned conventional farm in the Piedmont region of Athens, Georgia, USA. |
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Bounding Coordinates:
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| West: | -83.3167 degrees
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| East: | -83.2333833 degrees
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| North: | 33.95 degrees
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| South: | 33.95 degrees
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| Taxonomic Range: |
| Classification: |
| Rank Name: | Class |
| Rank Value: | Arachnida |
| Classification: |
| Rank Name: | Order |
| Rank Value: | Araneae |
| Common Name: | Spiders |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Arachnida |
| Classification: |
| Rank Name: | Order |
| Rank Value: | Oribatida |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Arachnida |
| Classification: |
| Rank Name: | Order |
| Rank Value: | Prostigmata |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Arachnida |
| Classification: |
| Rank Name: | Subclass |
| Rank Value: | Acarina |
| Classification: |
| Rank Name: | Order |
| Rank Value: | Mesostigmata |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Hexapoda |
| Classification: |
| Rank Name: | Family |
| Rank Value: | Isopoda |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Hexapoda |
| Classification: |
| Rank Name: | Family |
| Rank Value: | Sminthuridae |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Hexapoda |
| Classification: |
| Rank Name: | Order |
| Rank Value: | Collembola |
| Classification: |
| Rank Name: | Family |
| Rank Value: | Entomobryidae |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Hexapoda |
| Classification: |
| Rank Name: | Order |
| Rank Value: | Collembola |
| Classification: |
| Rank Name: | Family |
| Rank Value: | Onychiuridae |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Hexapoda |
| Classification: |
| Rank Name: | Order |
| Rank Value: | Collembola |
| Classification: |
| Rank Name: | Family |
| Rank Value: | Tomoceridae |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Hexapoda |
| Classification: |
| Rank Name: | Order |
| Rank Value: | Diptera |
| Common Name: | Flies |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Hexapoda |
| Classification: |
| Rank Name: | Order |
| Rank Value: | Protura |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Hexapoda |
| Classification: |
| Rank Name: | Subclass |
| Rank Value: | Insecta |
| Classification: |
| Rank Name: | Order |
| Rank Value: | Coleoptera |
| Common Name: | Beetles |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Hexapoda |
| Classification: |
| Rank Name: | Subclass |
| Rank Value: | Insecta |
| Classification: |
| Rank Name: | Order |
| Rank Value: | Hemiptera |
| Classification: |
| Rank Name: | Suborder |
| Rank Value: | Stemorryncha |
| Common Name: | Hoppers |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Hexapoda |
| Classification: |
| Rank Name: | Subclass |
| Rank Value: | Insecta |
| Classification: |
| Rank Name: | Order |
| Rank Value: | Hymenoptera |
| Common Name: | Wasps |
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| Classification: |
| Rank Name: | Class |
| Rank Value: | Hexapoda |
| Classification: |
| Rank Name: | Subclass |
| Rank Value: | Insecta |
| Classification: |
| Rank Name: | Order |
| Rank Value: | Hymenoptera |
| Classification: |
| Rank Name: | Family |
| Rank Value: | Formicidae |
| Common Name: | Ants |
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| Classification: |
| Rank Name: | Kingdom |
| Rank Value: | Fungi |
| Common Name: | Fungi |
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| Classification: |
| Rank Name: | Kingdom |
| Rank Value: | Monera |
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| Classification: |
| Rank Name: | Phylum |
| Rank Value: | Nematoda |
| Common Name: | Nematodes |
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Sampling, Processing and Quality Control Methods
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Step by Step Procedures
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| Step 1: |
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Description:
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Litter mass loss
Litter mass loss dynamics were assessed using the litterbag approach. Nylon mesh litterbags, 13 cm x 15 cm in size and consisting of 2-mm mesh, were filled with 3 g of the same litter type assigned to the plot. During the packaging of the litter care was taken to avoid breaking the material. For the mixed litter treatment, component litter species were equally represented by mass to total 3 g litter. To ensure that larger fauna could access litter in the bags placed in the 5-cm mesh sub-plots, ten 4-mm dia. holes were added to the litterbags. Three litterbags were placed in each box at the same time litter species were added to the 4 m2 plots, and were placed even with the litter. Following field exposure for 21, 91 or 165 days, one litterbag was removed per time point from each box and picked-free of foreign material adhering to the decomposing litter. Following air-drying, litter sub-samples were placed for 3 h at 500°C to determine ash free dry mass (AFDM).
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| Step 2: |
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Description:
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Litter nematodes
Approximately half of the litter was taken from each sample bag and used in gravimetric extraction of nematodes in water via Baermann funnels for 48 h. Nematodes were harvested and preserved in 4% formaldehyde and later identified to feeding group. Abundance of each group was expressed as number of individuals per g ash-free dry mass (AFDM).
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| Step 3: |
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Description:
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Litter microarthropods
Remaining litter in bags was placed on Tullgren funnels for five days for dry heat and light extraction of microarthropods and other mesofauna; those mesofauna (and some small macrofauna) collected were preserved in 70% ethanol. Due to a large number of litterbags and a limited number of Tullgren funnels, reps I & II and reps III & IV of each treatment were placed on one Tullgren funnel and the mesofauna collected together. Mesofauna were identified to the order level, or lower when possible, and expressed as number per g ash-free dry mass (AFDM). Additionally, taxa richness were recorded and relative diversity calculated using the Shannon Index.
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| Step 4: |
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Description:
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Litter C:N
Dry samples of the plant litter were ground to fine powder prior to chemical analyses. Carbon (C) and nitrogen (N) were analyzed on a 4 mg subsample on a Carlo Erba Elemental Analyzer and are reported as %C and %N by dry mass.
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Instrument(s):
| Carlo Erba Elemental Analyzer |
| Step 5: |
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Description:
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Litter P
Phosphorus (P) was measured from 0.5 g of ground litter that was ashed, extracted in aqua regia acid and analyzed on an automated Alpkem Analyzer and is reported as %P by dry mass.
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Instrument(s):
| Alpkem Rapid Flow Analyzer (300 Series, Alpkem, Clackamas, USA) |
| Step 6: |
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Description:
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Litter fiber
Cellulose, hemicellulose, and lignin concentrations were measured from 0.5 g of each sample using sequential neutral detergent/acid detergent digestion on an Ankom A200 fiber analyzer.
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Instrument(s):
| Ankom A200 fiber analyzer |
| Step 7: |
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Description:
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Litter PLFA
PLFAs were extracted from 1 g freeze-dried, ground litter. (Tests demonstrated that 1 g was the smallest sample possible for maximum extraction efficiency, and ground litter is more efficiently extracted than un-ground.) Samples were shaken for 2 h in a methanol-chloroform-phosphate buffer (2:1:0.8 in volume, using 28.5 ml g-1 sample to maintain an aqueous solution with ground litter). The organic phase was fractionated with an activated silica gel column (BondElut; Varian, Palo Alto, USA). Mild alkaline methanolysis was used to produce fatty acid methyl esters (FAMEs). FAMEs were purified with NH2 aminopropyl columns (BondElut; Varian, Palo Alto, USA) and analyzed with a Hewlett-Packard (HP, Palo Alto, USA) 6890 series GC with a flame ionization detector and a 30 meter DB-5 column (film thickness = 0.25 μm, internal dia. 0.32 mm; Agilent, Santa Clara, USA). Individual PLFAs were quantified in relation to an internal standard (20:0 ethyl ester). Compounds were identified by comparison of their retention times with those of a prepared standard mixture containing 36 FAMES (Matreya, USA; Sigma-Aldrich, USA; Nu-Chek, USA), though many unidentified FAMEs were also detected. To estimate relative bacteria:fungi ratio, the sum of the concentration of the following microbial PLFA markers were used for bacteria: cy17:0, cy19:0, 18:1ω7c, 18:1ω9c; 14:0, i15:0, a15:0, 15:0, i16:0, i17:0, a17:0, and 17:0; while 18:2ω6,9c were used for fungi.
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Instrument(s):
| Hewlett-Packard (HP, Palo Alto, USA) 6890 series GC with a flame ionization detector and a 30 meter DB-5 column (film thickness = 0.25 μm, internal dia. 0.32 mm; Agilent, Santa Clara, USA) |
| Step 8: |
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Description:
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Soil gravimetric moisture content
Soils were dried at 105°C to constant mass.
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| Step 9: |
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Description:
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Nitrogen mineralization
We determined net N mineralization (or immobilization) rates from the litters and soils in the boxes by summing two separate measurements. The first measurement was based on the accumulation of inorganic N in resin bags (see below) buried beneath the soil boxes. The second measurement estimated the net release or immobilization of inorganic N within the soils of the litter boxes by assessing changes in their extractable inorganic N values across measurement periods. For the resin bag approach, nylon bags containing anion and cation exchange resins were buried immediately beneath the boxes to retain NO3- and NH4+ leached from the litter and soil above (Binkley and Matson 1983). Each nylon bag measured 4.5-cm dia. by 1-cm tall and contained 24 g of an even mixture of Na-saturated cation and Cl-saturated anion exchange resins (Sybron Ionac C-250 and ASB-1P, Sybron Chemicals, Birmingham, USA). Only one nylon bag was buried beneath each box immediately before litter application to the plots. The bag was removed on the first sampling date (July-August incubation period) and replaced by a new one for the next incubation period (August-October). The procedure was repeated for the final incubation period (October -February). Resins were extracted in 2 M KCl for 1 h (20 ml for the soils and 60 ml for the resin bags). Extracts were analyzed for NO3- and NH4+ using an Alpkem Continuous Flow Analyzer. The NO3- and NH4+ that accumulated in the resin over each incubation period was converted to μg N g-1 soil using an average bulk density value of 1.1 g cm-3 for the site.
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Instrument(s):
| Alpkem Continuous Flow Analyzer |
| Step 10: |
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Description:
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Soil mineral N (NO3 and NH4)
Soils (4 g) were extracted and analyzed in the same manner as resins and concentrations of mineral N in extracts were brought to μg N g-1 soil.
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Instrument(s):
| Alpkem Continuous Flow Analyzer |
| Step 11: |
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Description:
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Soil PLFA
Soil samples (approximately 50 g) were obtained by collecting and compositing three sub-samples. To assess abundance of total live microbial, fungal, bacterial and protozoan biomass, we used a phospholipid fatty acid (PLFA) approach. PLFA were extracted from 5 g of 2-mm sieved and freeze-dried soils from each box. Samples were shaken for 2 h in a mixture of methanol-chloroform-phosphate buffer (2:1:0.8 in volume). The organic phase was fractionated with an activated silica gel column (BondElut; Varian, Palo Alto, USA). Mild alkaline methanolysis was used to produce fatty acid methyl esters (FAMEs). FAMEs were purified with NH2 aminopropyl columns (BondElut; Varian, Palo Alto, USA) and analyzed with a GC. Individual PLFAs were quantified in relation to an internal standard (20:0 ethyl ester). Compounds were identified by comparison of their retention times with those of a prepared mixture standard containing 36 FAMES (Matreya, USA; Sigma-Aldrich, USA; Nu-Chek, USA). Fatty acid notation used follows that in (Frostegard and Baath 1996). Microbial group PLFA markers were: cy17:0, cy19:0, 18:1ω7c and 18:1ω9c for Gram-negative bacteria; 14:0, i15:0, a15:0, 15:0, i16:0, i17:0 and a17:0 for Gram-positive bacteria; i15:0, a15:0, 15:0, i16:0, cy17:0, 17:0, 18:1 ω7c and cy19:0 for all bacteria; 18:2ω6,9c for fungi and 10Me16:0, 10Me17:0 and 10Me18:0 for the actinobacteria. 20:2ω6,9c; 20:3ω6,9,12c and 20:4ω6,9,12,15c were used as indicators of protozoan abundance.
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Instrument(s):
| Hewlett-Packard (HP, Palo Alto, USA) 6890 series GC with a flame ionization detector and a 30 meter DB-5 (film thickness = 0.25 μm, internal dia. 0.32 mm; Agilent, Santa Clara, USA) |
| Step 12: |
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Description:
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Soil nematodes
Nematodes were extracted from approx. 6 g of fresh soil with the Baermann funnel method for 72 h and preserved in 5% formaldehyde. Total nematode counts to the level of trophic group were performed for each sample.
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| Step 13: |
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Description:
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Soil microarthropods
Microarthropods were extracted from approx. 25 g of fresh soil for 5 days on modified Tullgren-type extractors.
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Sampling Area And Frequency:
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Temporal extent: June 2005-July 2005: site preparation and treatment application. Litter sampling was carried out 21, 91 and 193 days (in August 2005, October 2005, and February 2006, respectively) following litter application.
Spatial extent: 100 m2 plot
Taxonomic extent: microbial PLFA, nematodes to functional-feeding group, microarthropods to Order or lower
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Sampling Description:
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In June 2005, standing vegetation (consisting of grasses and forbs) was pulled from a 100-m2 site. The site was kept vegetation-free throughout the duration of the study by periodically weeding all sprouting plants. The site was divided into 24 plots of 4 m2 and sheets of aluminum flashing were buried to 4-5 cm around each plot. Soil from the top 5 cm of two areas of 25 × 50 cm within each plot was collected, mixed and sieved to 4 mm. Care was taken to allow at least 20-cm distance between these two areas and between their edges and the edge of the plot. Collected soil was frozen at -80°C for 72 h to kill soil-dwelling fauna. Post thawing, soil was placed back in the field in metallic wire frames (25 cm × 50 cm × 5 cm, henceforth referred to as 'boxes') that fit into the previously dug collection areas, with the outer rim of the box remaining 1-2 cm above the surrounding soil surface. Soil under and around the sides of the boxes was relocated as necessary to ensure that there was contact between soil inside and outside the box. The bottom and the sides of the boxes were lined with mesh of either 40-μm or 5-mm diameter; the smaller mesh was to restrict re-colonization of larger-bodied fauna into the boxes. Soil was added to boxes to a depth of approx. 4 cm to allow room for the addition of litter. The boxes were open on top so that the mesh restricted access to mineral soil dwellers but not mobile (jumping) litter fauna. Soil was left bare for 6 weeks to permit re-colonization by fauna and to dissipate the nutrient flush associated with disturbance. Litter treatments consisting of leaf litter from five different plant species and an equal mixture of them (six litter types) were randomly assigned to four of the 4-m2 plots and were surface applied at a rate of 327 g m-2 (air dry weight) both to the inside and to the outside of the boxes within each plot. Substrates applied were green litter of cereal rye (Secale cereale L), crimson clover (Trifolium incarnatum L.) and false indigo (Amorpha fruticosa L.); wheat straw (Triticum aestivum L.), pine needles (Pinus taeda L), and an even mixture of all the above by mass. Sampling was carried out 21, 91 and 165 days (August, October and February) following litter application. Each treatment was replicated 4 times.
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Data Set Usage Rights
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