Temporal and spatial variations of soil nematode assemblages across distinct forest ecosystems

Environmental variables such as soil moisture and phosphorus (P) might influence above- and below-ground biodiversity. In this study, we investigated the rarely reported individual and interactive multifactor effects of soil moisture and phosphorus addition with the type of above-ground tree species (biological interactions) on the soil nematode community structure. We established a completely randomized experimental design with two plant types (N2-fixer and non-nitrogen fixer) and different combinations of water treatments and P additions (i.e., water with P addition, water only, drought with P addition, and drought only) in a greenhouse and investigated their effects on the soil chemical properties and nematode community. Soil samples were collected at the end of the experiment and were analyzed for soil moisture content (SM), available phosphorus (aP), nitrate nitrogen (NO3−–N), ammonium nitrogen (NH4+–N), dissolved organic carbon (DOC), dissolved organic nitrogen (DON), and nematode community. The following trophic groups were assigned to the nematodes: bacterivores (Ba), fungivores (Fu), omnivores–predators (Op), and plant parasites (PP). The channel index (CI), enrichment index (EI), maturity index (MI), genus richness (GR), and Simpson dominance (Ig) were adopted to indicate the indices of the nematode food web. Phosphorus addition and its interaction with water treatments had no statistically significant effects on the soil nematode community, but there were significant decreasing (p < 0.05) effects of P addition on the total density of nematodes of the N2-fixing tree under optimum water treatment. There were no significant interactive effects of P addition and water treatments on all the trophic groups, but plant type, water treatments, and their interactions significantly affected the density of most nematode trophic groups. The total nematode abundances of bacterivores, plant parasitic, omnivores, and enrichment index were significantly higher in the N2-fixers than in the non-nitrogen-fixing tree. Soil nematode abundance and community composition were more affected by the plant type than by the P addition and its interaction with water treatments. Drought exerted adverse effects on the total density of soil nematodes, the dominant genera, and the trophic groups. This study demonstrated that the rate of drought impact hinges more on the type of tree and that N2-fixing tree could still maintain the soil food web structure irrespective of the environmental changes.

Community composition, diversity and metabolic footprints of soil nematodes in differently-aged temperate forests

Influences of different tillage and residue management systems on soil nematode community composition and diversity in the tropics

Long-term application of chemical fertilizer poses an environmental threat to belowground ecosystems. However, the impact of nitrogen (N) or phosphorus (P) fertilizers on soil biodiversity and the conditions of soil food web remains largely unknown. Soil nematodes are the most abundant multicellular soil animals and serve as excellent bioindicators of soil. Here, we investigated soil nematode communities and food web structure in a long-term experiment with different application rates of N and P fertilizers in northeast China. The application of N and P fertilizers increased the abundance of bacterivores but suppressed the abundance of omnivores and predators. The abundance of bacterivores exhibited an increasing trend, while that of omnivores and predators showed a decreasing trend with increasing rates of N and P fertilizers. Plant parasites displayed a decreasing trend in response to N fertilizer, but not to P fertilizer. N and P fertilizers also altered nematode functional guild composition, with N fertilizer increasing the abundance of Ba1, and P fertilizer increasing the abundance of Fu2 and Ba3. Nonmetric multidimensional scaling (NMDS) analysis revealed apparent successions of nematode communities from no fertilizer soils to high rates of N or P fertilizer soils at both the genus and functional guild levels. Furthermore, N and P fertilizers resulted in different nematode communities. In terms of nematode food web indices, N fertilizer increased the enrichment index (EI) but reduced the channel index (CI) and structure index (SI), whereas P fertilizer only reduced the SI value. High rates of N and P fertilizers increased the respired carbon of bacterivores but reduced the respired carbon of predators. Mantel tests revealed significant correlations between soil properties and the community composition of both fungivores and omnivores. Among all soil properties, available phosphorus (AP) had the greatest influence on the community structure of soil nematodes. Our findings indicate that N fertilizer has a powerful effect on nematode food web structure, while P fertilizer exerts a stronger effect on soil nematode community composition.

Soils are extremely rich in biodiversity, and soil organisms play pivotal roles in supporting terrestrial life, but the role that individual plants and plant communities play in influencing the diversity and functioning of soil food webs remains highly debated. Plants, as primary producers and providers of resources to the soil food web, are of vital importance for the composition, structure, and functioning of soil communities. However, whether natural soil food webs that are completely open to immigration and emigration differ underneath individual plants remains unknown. In a biodiversity restoration experiment we first compared the soil nematode communities of 228 individual plants belonging to eight herbaceous species. We included grass, leguminous, and non-leguminous species. Each individual plant grew intermingled with other species, but all plant species had a different nematode community. Moreover, nematode communities were more similar when plant individuals were growing in the same as compared to different plant communities, and these effects were most apparent for the groups of bacterivorous, carnivorous, and omnivorous nematodes. Subsequently, we analyzed the composition, structure, and functioning of the complete soil food webs of 58 individual plants, belonging to two of the plant species, Lotus corniculatus (Fabaceae) and Plantago lanceolata (Plantaginaceae). We isolated and identified more than 150 taxa/groups of soil organisms. The soil community composition and structure of the entire food webs were influenced both by the species identity of the plant individual and the surrounding plant community. Unexpectedly, plant identity had the strongest effects on decomposing soil organisms, widely believed to be generalist feeders. In contrast, quantitative food web modeling showed that the composition of the plant community influenced nitrogen mineralization under individual plants, but that plant species identity did not affect nitrogen or carbon mineralization or food web stability. Hence, the composition and structure of entire soil food webs vary at the scale of individual plants and are strongly influenced by the species identity of the plant. However, the ecosystem functions these food webs provide are determined by the identity of the entire plant community.

PDF HTML阅读 XML下载 导出引用 引用提醒 模拟氮沉降对温带森林土壤线虫群落组成和代谢足迹的影响 DOI: 10.5846/stxb201606231225 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31170484） Effects of simulated nitrogen deposition on temperate forest soil nematode communities and their metabolic footprints Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:已有研究表明氮沉降可显著影响土壤线虫群落组成和多样性。然而，目前大多数研究集中在无机氮沉降的影响，而对于不同氮素形态对土壤线虫群落影响的研究还不是很清楚。利用运行5年的模拟氮沉降试验平台，开展了4个氮添加处理即对照（无氮添加，CK）、无机氮（硝酸铵，IN），有机氮（尿素和甘氨酸1：1混合，ON）和混合氮（无机氮和有机氮7：3混合，MN）添加对温带森林土壤线虫群落组成和多样性的影响研究，采用浅盘法分离线虫，土壤性质如pH、含水量、全碳全氮分别采用电位法、烘干法和元素分析仪法进行测定，应用营养类群组成、区系分析和代谢足迹分析不同形态氮沉降下土壤线虫群落结构特征。共分离线虫50个属，其中在CK样地中共发现29个属，在IN，ON和MN处理中分别发现线虫属37个，34个和29个，盘旋属Rotylenchus和大节片属Macroposthonia在所有处理中均为优势属。结果表明，与CK相比，IN处理、ON处理和MN处理均显著增加了土壤硝态氮含量。与无机氮相比，混合氮处理显著降低了食真菌线虫数量，有机氮处理显著增加了捕食杂食性线虫数量。与对照相比，无机氮处理显著增加了线虫多样性指数（H'），IN处理的均匀度指数（J）显著高于CK和MN处理，混合氮处理对应的优势度指数（λ）显著高于其他3个处理。在CK和ON处理，线虫的结构指数（SI）较高，富集指数（EI）较低，表明这两个处理的土壤受干扰程度较小，食物网处于结构化状态。在IN和MN处理，土壤线虫富集指数和结构指数均较高（>50），表明食物网稳定成熟。食真菌线虫代谢足迹和生物量碳在无机氮处理最高。有机氮和混合氮处理显著增加了捕食杂食性线虫代谢足迹和生物量碳。以上结果表明，不同氮素形态不仅对土壤线虫群落组成产生了影响，而且其代谢足迹也发生了显著的变化，这一结果有助于揭示温带森林对氮沉降的响应机制。 Abstract:Previous studies have shown that nitrogen deposition has a significant effect on the composition and diversity of soil nematode community. However, most studies focused on the effect of inorganic nitrogen, and the influences of different forms of N on soil nematode communities remained unclear. Based on the five-year simulated N-deposition experiment, we investigated the effects of N deposition on soil nematode communities. Four treatments, including the control (no nitrogen addition; CK), inorganic N (NH4NO3; IN), organic N (urea and glycine 1:1; ON), and mixed nitrogen (inorganic and organic N at the ratio of 7:3, MN), were studied. The soil nematodes were collected using the shallow basin method. The soil chemical properties, such as pH, potentiometry, soil water content (oven drying method) and elemental composition, were tested. The trophic composition, funnel analysis, and metabolic footprints were analyzed to understand the effect of different forms of N on soil nematode functional diversity. A total of 50 genera were classified. Of these 29, 37, 34, and 29 genera were included in the CK, IN, MN, and ON treatments, respectively. Rotylenchus and Macroposthonia were the dominant groups in all treatments. The results showed that IN, ON, and MN significantly increased the content of nitrate nitrogen compared with CK. The total numbers of nematodes in all treatments were not significantly different. MN significantly decreased the abundance of fungivores compared with IN, while ON increased that of omnivores-predators. Compared with CK, the IN treatment increased the diversity index (H') of soil nematodes. Furthermore, IN significantly increased the evenness index (J') compared with CK and MN. The dominance index (λ) was the highest in the MN treatment, and the nematode channel ratios in all treatments were more than 0.75, indicating that the process of soil decomposition occurs mainly through a bacterial-based energy channel. The results of the nematode funnel analysis indicated that the structure index in the CK and ON treatments was high, while the enrichment index was low, showing that the degree of interference was low and the soil food-web tended to be structured. The enrichment and structure indices of nematode communities in the ON and MN treatments were more than 50, indicating the stability of food web in the soil. The metabolic footprint and biomass carbon of fungivores were the highest in the IN treatments among all treatments. ON and MN significantly increased the metabolic footprint and biomass carbon of omnivores-predators. All results indicated that N deposition with different forms of nitrogen fertilization affected not only the composition of a soil nematode community, but also its metabolic footprints. Our findings contribute to understanding the response mechanism of temperate forests to nitrogen deposition. 参考文献 相似文献 引证文献

Strong impacts of belowground tree inputs on soil nematode trophic composition

Effects of tillage and residue management on soil nematode communities in North China

Soil nematode community composition and stability under different nitrogen additions in a semiarid grassland

Changes in the soil nematode community among climate zones do not keep pace with changes in plant communities

Elevated O3 has stronger effects than CO2 on soil nematode abundances but jointly inhibits their diversity in paddy soils

Success of invasive non-native plant species management is usually measured as changes in the abundance of the invasive plant species or native plant species following invader management, but more complex trophic responses to invader removal are often ignored or assumed. Moreover, the effects of invader removal at different stages of the invasion process is rarely evaluated, despite a growing recognition that invader impacts are density or stage-dependent. Therefore, the effectiveness of invasive species management for restoring community structure and function across trophic levels remains poorly understood. We determined how soil nematode diversity and community composition respond to removal of the globally invasive tree species Pinus contorta at different stages of invasion by reanalysing and expanding an earlier study including uninvaded vegetation (seedlings removed continuously), early invader removal (saplings removed), late removal (trees removed), and no removal (invaded). These treatments allowed us to evaluate the stage-dependent belowground trophic responses to biological invasion and removal. We found that invaded plots had half the nematode taxa richness compared to uninvaded plots, and that tree invasion altered the overall composition of the nematode community. Differences in nematode community composition between uninvaded nematode communities and those under the tree removal strategy tended to dilute higher up the food chain, whereas the composition of uninvaded vs. sapling removal strategies did not differ significantly. Conversely, the composition of invaded compared to uninvaded nematode communities differed across all trophic levels, altering the community structure and function. Specifically, invaded communities were structurally simplified compared to uninvaded communities, and had a higher proportion of short life cycle nematodes, characteristic of disturbed environments. We demonstrate that a shift in management strategies for a globally invasive tree species from removing trees to earlier removal of saplings is needed for maintaining the composition and structure of soil nematode communities to resemble uninvaded conditions.

Success of invasive non-native plant species management is usually measured as changes in the abundance of the invasive plant species or native plant species following invader management, but more complex trophic responses to invader removal are often ignored or assumed. Moreover, the effects of invader removal at different stages of the invasion process is rarely evaluated, despite a growing recognition that invader impacts are density or stage-dependent. Therefore, the effectiveness of invasive species management for restoring community structure and function across trophic levels remains poorly understood. We determined how soil nematode diversity and community composition respond to removal of the globally invasive tree species Pinus contorta at different stages of invasion by reanalysing and expanding an earlier study including uninvaded vegetation (seedlings removed continuously), early invader removal (saplings removed), late removal (trees removed), and no removal (invaded). These treatments allowed us to evaluate the stage-dependent belowground trophic responses to biological invasion and removal. We found that invaded plots had half the nematode taxa richness compared to uninvaded plots, and that tree invasion altered the overall composition of the nematode community. Differences in nematode community composition between uninvaded nematode communities and those under the tree removal strategy tended to dilute higher up the food chain, whereas the composition of uninvaded vs. sapling removal strategies did not differ significantly. Conversely, the composition of invaded compared to uninvaded nematode communities differed across all trophic levels, altering the community structure and function. Specifically, invaded communities were structurally simplified compared to uninvaded communities, and had a higher proportion of short life cycle nematodes, characteristic of disturbed environments. We demonstrate that a shift in management strategies for a globally invasive tree species from removing trees to earlier removal of saplings is needed for maintaining the composition and structure of soil nematode communities to resemble uninvaded conditions.

Effects of different carbon inputs on soil nematode abundance and community composition

Soil biodiversity plays an important role in both agricultural productivity and ecosystem functions. Cover crop species influence the primary productivity of the ecosystem and basal resources. However, it remains poorly understood how different cover crop treatments influence the community of soil nematodes in an orchard ecosystem. In this study, field experiments were conducted to investigate the effects of cover crop treatments with different species numbers, i.e., no cover crop (CK), two cover crop species (C2), four cover crop species (C4), and eight cover crop species (C8), on weed biomass, together with composition, abundance, and metabolic footprint of soil nematode community in a kiwifruit orchard. As compared to the CK group, the groups of cover crop treatments had lower weed biomass, which decreased with the increase of the cover crop diversity. Moreover, for the abundance of total nematodes, fungivores exhibited higher levels in C4 and C8 treatments than that in CK, bacterivores had a higher abundance in C4 treatment, and plant parasites had a higher abundance in C2 and C8 treatments. Cover crop treatments also changed the structure of nematode community and enhanced the nematode interactions and complexity of nematode community network. In addition, C4 increased the Wasilewska index but decreased the plant-parasite index. The metabolic footprints of fungivores were higher in cover crop treatments compared with CK, and C4 and C8 also increased the functional metabolic footprint of nematode. Soil nematode faunal analysis based on nematode metabolic footprints showed that C8 improved the soil nutrient status and food wed stability. Mantel test and redundancy analysis showed that soil microbial biomass nitrogen and carbon, organic carbon, nitrate nitrogen, moisture content, pH, and cover crop biomass were the main factors that affect soil nematode community. In conclusion, cover crop treatments with four or eight plant species displayed a positive role in weed control, improvement of soil health, and promotion of energy flow in the soil food web through the increase in the metabolic footprints of nematodes in kiwifruit orchard.