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Residue mulching has been adopted to improve soil organic carbon and to prevent soil erosion and degradation, which in turn promote the sustainable development of soil ecosystems. Nematode metabolic footprints provide information about the responses of nematodes to resources and also help in quantifying the contributions of nematodes to ecosystem functions and services. However, how production and respiration components of nematode metabolic footprints vary in different mulching amounts is less clear. Therefore, to explore the impact of different mulching amounts on the production and respiration of nematode trophic groups, soil samples were collected from four mulching treatments (without mulching, with 33%, 67%, and 100% mulching of the stover remaining at harvest) at the depths of 0–5 cm and 5–10 cm in a 12‐year long no‐tillage system. Our results proved that the mulching effect on the production and respiration of fungivores was significant, and the production was 71.8%, 62.7%, 71.5% higher and respiration was 67.7%, 61.9%, 70% higher in 100% mulching treatment than without mulching, 33% and 67% mulching, respectively. More basal C flowed into the fungal decomposition pathways and fungivores contributed more to soil carbon sequestration through the decomposition of recalcitrant nutrients from residue at the end of crop growth. There was higher production than respiration in bacterivores and an opposite trend was observed in fungivores. Residue mulching increased the metabolic footprints of nematode communities and carbon use efficiency of fungivores and omnivores and predators and then enhanced the potential of soil carbon sequestration through the metabolic process of different nematode trophic groups. [ABSTRACT FROM AUTHOR]

Effect of crop row spacing on the belowground ecosystem, especially at an aggregate scale, remains unexplored. To explore how row spacing influenced nematode community and ecosystem function at the aggregate scale, four row spacings i.e. equidistant-row (ER, 50 cm-inter-row distance, 33 cm-intra-row between plants in each row) and non-equidistant-row including NR1 (100 cm + 50 cm row distance and 22 cm intra-row), NR2 (100 cm + 50 cm inter-row and 25 cm intra-row), and NR3 (60 cm + 40 cm inter-row and 33 cm intra-row) were compared, and four soil aggregate fractions i.e. >2 mm, 1–2 mm, 0.25–1 mm and <0.25 mm were separated. Row spacing did not impact C and N, but significantly influenced P. The regulation effect of acid phosphatase on soil available P was aggregate-scale dependent. Nematode faunal analysis indicated that NR3 within 0.25–1 mm was less disturbed or relatively undisturbed environments. Structural equation model showed row spacing pattern directly affected multifunctionality, while aggregate fractions indirectly contributed to multifunctionality mainly by regulating the richness of total nematodes and trophic groups. It was concluded that NR3 had potential to construct more stable food web, and therefore was possibly the suitable planting pattern. [ABSTRACT FROM AUTHOR]

The structure of soil nematode assemblages was assessed in field plots in the San Joaquin Valley of California which have 16-year management system histories. Attributes of the ecosystem functions of the assemblages were determined in laboratory studies. The four agricultural management systems were no tillage (minimum tillage) with cover crops in the intervals between economic crops, standard tillage with cover crops, minimum tillage without cover crops and standard tillage without cover crops. The economic crops were sorghum and garbanzo beans. A soil column system was used in laboratory studies to evaluate the nitrogen mineralization ecosystem service associated with nematode assemblages in soils from the four management systems compared to that in defaunated soil. In an additional comparison, defaunated soil was amended with mineral fertilizer solution for comparison with the mineralization service of the soil fauna. Management systems using cover crops, which created a continuity of both photosynthetic production and roots in the soil, strongly enhanced the nematode assemblages in the field soil. Management systems with cover crops had greater total abundance, measured as numbers, biomass and metabolic footprints, of nematodes, and also of the functional guilds of nematodes considered important in soil fertility and as prey for predators. Leachates from soil columns with intact nematode assemblages had greater total mineral nitrogen and supported greater plant growth than those from defaunated columns. Soil carbon levels in field plots were strongly affected by the management systems. The biomass and diversity-weighted footprint of bacterivore and microbivore (bacterivores plus fungivores) nematodes, in turn, were correlated with levels of soil carbon. [ABSTRACT FROM AUTHOR]

Vegetation restoration plays an important role in controlling desertification. The effects of vegetation restoration on aboveground biodiversity are well known. However, the effects of vegetation restoration on the belowground biotic communities in sand land are still highly important and need to be explored. We examined soil nematode community composition under Caragana microphylla of dominant native vegetation with 0- (the drifting sand dunes), 13-, 18- and 29-year sand-fixation and natural vegetation communities in Horqin Desert, China. The result showed that total nematodes, bacterivores, fungivores and omnivores-predators were all significantly affected by sand-fixation years, with their highest values being in 29-year sand-fixation. The conversion of drifting sand dunes to shrub land resulted in significant changes in r -strategists with cp -2 and K -strategists with cp -4 of soil nematodes. Nematode genera in different sand-fixation years were clearly separated by redundancy analysis and the preference of different nematode genera to habitat was discriminative. The effect of C. microphylla on soil abiotic properties and nematode communities was time-dependent. The significant variation of soil abiotic properties appeared from 18-year sand-fixation, and soil nematodes increased significantly after 13-year sand-fixation. The plantation of C. microphylla improved nematode diversity, with markedly higher values in the later sandy land stabilization stage than the drifting sand dunes. Furthermore, it can be concluded that soil nematode communities as bioindicators reflect the progressive restoration process of the sandy ecosystems. [ABSTRACT FROM AUTHOR]

Abstract: Soil nematode abundance, community composition and biomass were determined in the Fengqiu State Key Agro-Ecological Experimental Station, North China, in order to evaluate the effects of tillage system (conventional tillage and no-tillage) and residue management (0, 50% and 100% wheat residue incorporation/coverage) on the nematode communities. Two kinds of indicators (descriptive and evaluative) were categorized. Of the descriptive indicators, residue management had a significant effect on the total nematode abundance, biomass and trophic groups except for bacterivores. Of the evaluative indicators, Shannon diversity (H′), generic richness (GR), nematode channel ratio (NCR) and enrichment index (EI) significantly increased with increasing residue quantity, whereas dominance (λ), basal index (BI) and channel index (CI) exhibited an opposite trend. Significant tillage effects were observed on the trophic diversity (TD), EI, CI and carbon production (P). The responses of nematodes to tillage and residue were genus-dependent. Canonical correspondence analysis indicated that tillage explained 4.9% and 15.4%, and residue management explained 5.2% and 13.1% of the variations in soil nematode abundance and biomass, respectively. Different metabolic footprint characteristics of the food web were demonstrated graphically by enrichment and structure footprints. The evaluative indicators, such as EI and CI, were sensitive to both tillage and residue management. The descriptive indicators could be used to obtain an intuitive answer to the effect of residue management and the evaluative indicators were more comprehensive for interpreting the structure and function of the soil food web under different tillage and residue management regimes. [Copyright &y& Elsevier]

• Nematode metabolic footprints, respiration and C use efficiency were calculated. • Plant belowground inputs favored higher nematode abundance than aboveground inputs. • Plant aboveground inputs promoted the formation of nematode fungal feeding channel. • Soil nematode structure footprint was driven by plant belowground inputs. • Belowground inputs caused higher nematode C use efficiency than aboveground inputs. Soil nematodes are key components of soil food web and, through their metabolic activities, play a crucial role in soil carbon (C) cycling. Aboveground and belowground plant C inputs can directly, or indirectly via soil microbes, modify nematode abundance and community composition. Aboveground and belowground C inputs differ in chemical composition, amounts, and frequency, so we hypothesized that the two input pathways affect nematode communities differently. To assess the relative contributions of aboveground versus belowground inputs to nematode community composition and activity, we subjected grassland soils to four plant input pathways over two consecutive years: no input, only aboveground input (+A), only belowground input (+B), and both aboveground and belowground inputs (+A + B). Nematode metabolic footprints, as estimates of C used in growth/reproduction and C lost by respiration, and C use efficiency (C used/(C used + C lost)) were calculated. We predicted that soils with belowground inputs, which are more directly linked to the soil biota, and which contain a more labile blend of molecules, would support richer and more complex nematode communities, and also favor a bacterial-driven decomposition channel. Accordingly, we showed that + B soils supported higher nematode numbers than + A soils, and that the bacterial decomposition channel was dominant in + B soils, while the fungal decomposition channel dominated in + A soils. Compared with + A soils, +B input system increased nematode structure footprints (the metabolic footprints of nematodes in upper functional guilds) rather than enrichment footprints (the metabolic footprints of enrichment opportunistic nematodes). Moreover, we observed that, compared to + A soils, +B soils had higher growth and respiration rates of bacterivores, omnivores-predators, and total nematodes. Finally, we found higher C use efficiency values for omnivores-predators and total nematodes in + B than in + A soils. We thus conclude that belowground plant-derived resources, by changing the ratio between fungivores and bacterivores, induce a faster carbon turnover rate, and higher metabolic activity of soil nematodes within soil food web, ultimately spurring richer and more efficient soil food web than aboveground inputs. [ABSTRACT FROM AUTHOR]

Abstract: Soil processes are driven by soil organisms and their interactions with plants and soil abiotic conditions. Climate changes may directly or indirectly alter soil processes and the organisms mediating these processes. Although aboveground influences of ozone have been studied widely on agroecosystems, the effects on belowground processes are poorly understood. This study aimed to investigate the effects of elevated ozone concentration [O3] on the components of soil microbial food webs and compare their responses between ozone-sensitive and ozone-tolerant wheat cultivars. The responses of soil biota to elevated [O3] varied between the two wheat cultivars. Fungal PLFA and the fungi to bacteria ratio decreased following elevated [O3], especially in the rhizospheric soil of ozone-tolerant wheat. Nematode functional guilds were sensitive to elevated [O3] and cultivar effects. At wheat jointing stage, bacterivores belonging to K-strategies decreased following elevated [O3], while fungivores exhibited a reverse trend. The abundance of flagellates decreased in ozone-tolerant wheat, but increased in ozone-sensitive wheat following elevated [O3]. However, an opposite trend was found in the bacterivores belonging to r-strategies. In conclusion, wheat cultivars play an important role in determining the effects of elevated [O3] on soil food web. The responses of soil biota to elevated [O3] were greater in ozone-tolerant wheat than in ozone-sensitive wheat, which may in turn have influenced soil organic matter decomposition and nutrient turnover. [Copyright &y& Elsevier]

Abstract: Nematode faunal response to the long-term (20-year) application of nitrogen fertilizer and organic manure was monitored in a Hapli-Udic Cambosol of Northeast China, where no fertilizer (C), nitrogen fertilizer (N), organic manure (M) and nitrogen fertilizer plus organic manure (N+M) treatments were compared. The obtained results showed that total nematode abundance responded positively to the M and N+M treatments. The numbers of Acrobeloides increased in the M and N+M treatments at maize jointing and booting stages, and those of Aphelenchoides were higher in the N+M treatment than in the N treatment at maize ripening stage. Early in the growing season, the numbers of bacterivores of cp-1 (cp, colonizer–persister) and cp-2 guilds were higher in the M and N+M treatments than in the N treatment, while those of bacterivores and fungivores of cp-4 guilds were higher in the C treatment than in the N, M and N+M treatments. Except at maize seedling stage, the numbers of fungivores of cp-2 and herbivores of cp-3 guilds were higher in the N+M treatment than in the C treatment. Ratios of the weighted abundance of representatives of specific functional guilds were used as indicators of food web structure, enrichment and decomposition channels. Values of the enrichment index (EI) at maize seedling and jointing stages were higher in the M and N+M treatments than in the C and N treatments, while an opposite trend was observed in the channel index (CI). Higher EI and lower CI suggest an enriched soil food web dominated with bacterial decomposition channels in the M and N+M treatments. [Copyright &y& Elsevier]

Elevated ozone threatens the sustainability of soil ecosystems by negatively affecting underground ecological processes. Crop residue, as an energy source with a low risk of environmental influence, can alleviate the negative impacts caused by climate change. However, little knowledge is comprehended about the influences of crop residue input on soil nematode metabolic activities and microfood-web under elevated ozone. Soil microfood-web consisting of microorganisms and nematodes plays a significant role in the underground processes such as energy flow and nutrient turnover. Thus, the objectives of this study were to explore the responses of soil nematode metabolic activities and microfood-web to different elevated ozone levels and crop residue application managements. The pot experiment was a split-plot design with elevated ozone system as main plot and residue addition treatment as subplot utilizing the open-top chambers. Elevated ozone systems included three levels (control, 45 ± 5 ppb; lower elevated ozone level, 80 ± 10 ppb and higher elevated ozone level, 110 ± 10 ppb). Residue addition treatments were soil without residue addition and soil with residue addition. The results showed that elevated ozone generated negative influences on soil microorganisms and nematodes by decreasing their biomass carbon. Crop residue input practice increased the functional metabolic footprints of nematodes under elevated ozone. The carbon utilization of soil biological communities shifted from soil organic carbon to extractable organic carbon after crop residue incorporation. Soil nitrate-nitrogen was the main supplier to meet the nitrogen demand of soil biota. The analysis of structural equation modeling revealed that the system under elevated ozone without crop residue addition was predominated by a bacterial decomposition channel. While the application of crop residue into soils also made a contribution to the fungal decomposition pathway. Consequently, it can be concluded that organic input practice strengthens the cooperation of soil microfood-web channels, which plays an important role in alleviating the negative effects of elevated ozone on the stability of soil microfood-web. • Elevated O 3 decreased the biomass carbon of soil microorganisms and nematodes. • Crop residue application drove soil nematode metabolic activity under elevated O 3. • Organic input shaped the fungal channel to alleviate O 3 damage on microfood-web. [ABSTRACT FROM AUTHOR]