文献信息：
Wu Shuqi1, He Tangqing1, Hu Zhengkun, Li Mingqi, Wang Xiaodong, Zhao Yexin, Cao Xinxin, Song Qiulai, Wu Di, Shen Qingsong, Zhang Pei, Tian Liming, Mipam Tserang Donko, Zhang Yi, Gong Zhenping*, Yan Chao*, Qiu Yunpeng*, Hu Shuijin. Soil organic carbon and pH interactions mediate N impacts on nematode abundance and composition. Global Change Biology, 2026, 32(6): e70963. https://doi.org/10.1111/gcb.70963Global Change Biology最新（2024年）影响因子：12.0
近日，国际生态学领域重要期刊《Global Change Biology》发表了南京农业大学草业学院胡水金教授团队研究论文《Soil organic carbon and pH interactions mediate N impacts on nematode abundance and composition》。该研究依托东北黑土区长期定位田间试验，并结合全球尺度整合分析，揭示了土壤有机碳（SOC）与pH协同调控氮输入影响土壤线虫群落的关键机制，为理解全球变化背景下农田地下生态系统响应规律以及黑土地保护与可持续管理提供了新的理论依据。
土壤线虫是土壤食物网中数量丰富、功能多样的重要后生动物类群之一，广泛参与有机质分解、养分循环和土壤健康维持，被视为指示地下生态系统变化的重要生物类群。随着全球变化和农业集约化进程加快，活性氮输入持续增加，正在深刻改变土壤酸碱环境、资源供给状况及地下食物网结构。然而，氮输入如何影响土壤线虫群落，以及不同土壤条件下线虫群落为何呈现差异化响应，其关键调控机制仍缺乏系统认识。
针对这一科学问题，研究团队依托东北黑土区长期田间试验平台，设置不同SOC水平和氮添加梯度，系统分析了植物生长、土壤理化性质、微生物群落及线虫功能类群对氮输入的响应特征。同时，研究整合全球相关研究数据，从局部生态过程与全球变化格局两个层面解析氮输入影响土壤线虫群落的驱动机制。
研究结果表明，氮输入对土壤线虫群落的影响并非简单的促进或抑制，而是受到SOC和pH的协同调控。在低SOC土壤中，氮添加更容易加剧土壤酸化，压缩线虫适宜生存空间，从而降低其丰度和活性，而在中高SOC土壤中，较充足的资源供给和较强的酸化缓冲能力能够减轻氮输入的不利影响，维持线虫群落稳定。进一步分析发现，土壤pH决定了线虫群落生存的环境边界，而土壤SOC则为土壤食物网提供资源基础并增强其生态稳定性。
基于上述发现，研究团队提出了SOC-pH双重调控框架（图1），系统阐释了不同SOC和pH条件下氮输入对线虫群落影响存在显著差异的原因。研究还发现，持续氮输入可能推动土壤食物网向细菌能量通道主导的方向转变，并伴随食物网结构简化的潜在风险。该研究从资源供给与环境过滤协同作用的视角，构建了氮输入影响土壤食物网的新理论框架，深化了对农田地下生态过程响应机制的认识。研究结果提示，在农业生产实践中，应统筹氮肥投入管理、有机碳提升与土壤酸化调控，通过有机培肥、秸秆还田和酸化改良等措施增强土壤缓冲能力，维持土壤生物多样性与生态系统功能，为黑土地保护和农业绿色发展提供科学支撑。
南京农业大学草业学院博士后吴书琦为论文第一作者，青年研究员何堂庆为共同第一作者。南京农业大学仇云鹏教授和东北农业大学龚振平教授、闫超教授为共同通讯作者，南京农业大学胡水金教授对本研究给予重要指导。该研究由南京农业大学、东北农业大学、黑龙江省农业科学院、中国科学院沈阳应用生态研究所、中国农业大学三亚研究院、中国科学院东北地理与农业生态研究所、四川大学和西南民族大学等单位合作完成。研究得到国家重点研发计划、国家自然科学基金、江苏省自然科学基金和四川省自然科学基金等项目资助。
FIGURE 1 Effects of N addition on plant biomass in the LOM, MOM and HOM soils. (a) shoot biomass; (b) root biomass.Bars indicate mean ± standard error (SE) (n = 3). Data were analyzed using two-way ANOVA to test the main effects of soil type, N input rate, and their interaction. Within each soil type, treatment effects were further evaluated using one-way ANOVA followed by Fisher's least significant difference (LSD) test for pairwise comparisons. Different lowercase letters denote significant differences among treatments (p < 0.05). Statistics for the fitted regression models relating each dependent variable to N input rate are also shown. Model form (linear vs. quadratic) was selected based on AIC within each soil type (**p < 0.01; ***p < 0.001). LOM, MOM, and HOM denote low-, medium-, and high-organic-matter soils, respectively. Different colors indicate soil types: White, LOM-soil; light gray, MOM-soil; gray, HOM-soil.
FIGURE 2 Effects of N addition on soil dissolved inorganic N (DIN), nitrification potential rate and pH in the LOM, MOM and HOM soils. (a) DIN; (b) nitrification rate; (c) soil pH. Bars indicate mean ± standard error (SE) (n = 3). Data were analyzed using two-way ANOVA to test the main effects of soil type, N input rate, and their interaction. Within each soil type, treatment effects were further evaluated using one-way ANOVA followed by Fisher's least significant difference (LSD) test for pairwise comparisons. Different lowercase letters denote significant differences among treatments (p < 0.05). Statistics for the fitted regression models relating each dependent variable to N input rate are also shown. Model form (linear vs. quadratic) was selected based on AIC within each soil type (*p < 0.05; **p < 0.01; ***p < 0.001). LOM, MOM, and HOM denote low-, medium-, and high-organic-matter soils, respectively. Different colors indicate soil types: White, LOM-soil; light gray, MOM-soil; gray, HOM-soil.
FIGURE 3 Effects of N addition on soil nematodes in the LOM, MOM and HOM soils (a) and relationships between soil nematodes and SOC or pH (b, c). Bars indicate mean ± standard error (SE) (n = 3). Data were analyzed using two-way ANOVA to test the main effects of soil type, N input rate, and their interaction. Within each soil type, treatment effects were further evaluated using one-way ANOVA followed by Fisher's least significant difference (LSD) test for pairwise comparisons. In (c), A second-order polynomial fit described the hump-shaped relationship between pH and coarse nematode abundance (nematode = −4.328 pH2 + 54.388 pH −165.846) which reached its maximum at pH = 6.28. Different lowercase letters denote significant differences among treatments (p < 0.05). Statistics for the fitted regression models relating each dependent variable to N input rate are also shown. Model form (linear vs. quadratic) was selected based on AIC within each soil type (*p < 0.05; **p < 0.01; ***p < 0.001). LOM, MOM, and HOM denote low-, medium-, and high-organic-matter soils, respectively. Different colors indicate soil types: White, LOM-soil; light gray, MOM-soil; gray, HOM-soil.
FIGURE 4 Effects of N addition on soil nematode community composition in the LOM, MOM and HOM soils. (a) Bacterivores; (b) Herbivores; (c) Fungivores; (d) Omnivore-carnivores. Bars indicate mean ± standard error (SE) (n = 3). Data were analyzed using two-way ANOVA to test the main effects of soil type, N input rate, and their interaction. Within each soil type, treatment effects were further evaluated using one-way ANOVA followed by Fisher's least significant difference (LSD) test for pairwise comparisons. Different lowercase letters denote significant differences among treatments (p < 0.05). Statistics for the fitted regression models relating the dependent variables to N input rates are also shown; model form (linear vs. quadratic) was selected based on AIC within each soil type (†p < 0.1; *p < 0.05; **p < 0.01; ***p < 0.001). LOM, MOM, and HOM denote low-, medium-, and high-organic-matter soils, respectively. Different colors indicate soil types: White, LOM-soil; light gray, MOM-soil; gray, HOM-soil.
FIGURE 5 Partial least square structural equation model (PLS-SEM) (a, b) showing the effects of N addition on nematode communities under different SOC level. The model goodness-of-fit (GoF) indicated good overall model performance, with values of 0.83 and 0.77 for panels (a) and (b), respectively. The black and red arrows indicate significant positive and negative effects (p < 0.05), respectively, whereas dashed arrows indicate nonsignificant relationships. Values adjacent to arrows represent standardized path coefficients. R2 denotes the proportion of variance explained. *, **, and *** represent significant differences at p ≤ 0.05, p ≤ 0.01, and p ≤ 0.001. Asterisks indicate the significance levels of individual standardized path coefficients, not significant differences among groups.
FIGURE 6 Geographic locations of sites included in the meta-analysis (a). Relationships between soil pH and raw nematode abundance (b) or pH-increment–averaged (ΔpH = 0.1) nematode abundance (c), and relationships between SOC and raw (individual-observation) nematode abundance (d) or soil pH (e). A second-order polynomial fit described the hump-shaped relationship between pH and coarse nematode abundance (b, nematode = −0.901 pH2 + 10.7 pH-21.7) or averaged nematode abundance at each pH increment (c, nematode = −0.932 pH2 +11.1 pH-22.6), which reached its maximum at pH = 5.94 (b) or 5.95 (c), respectively. Linear regression model with two-sided test was used for the statistical analysis (n = 480 in b; n = 51 in c; n = 487 in d; n = 445 in e). The error bands (shaded areas) in (b–e) represent the 95% confidence intervals around the best-fit regression line, and the red solid line indicates a significant relationship. Statistics (R2 and p-values) for polynomial regression are indicated. The exact p-values: p < 0.001 in (b–e).
FIGURE 7 Conceptual model illustrating that how soil organic carbon (SOC) and pH interaction mediates the effects of N addition on nematode community composition and abundance. (a) In low-SOC soils, N addition increased root biomass and belowground C allocation but also induced soil acidification. The negative effect of acidification likely outweighed the positive effect of increased C inputs on nematodes, resulting in shifts in nematode community composition and an overall decline in nematode abundance. (b) In high-SOC soils, N addition similarly enhanced root biomass and belowground C allocation while causing soil acidification. However, the high SOC and its strong buffering capacity offset the negative impact of acidification, leading to an overall increase in nematode abundance. The direction of each arrow indicates the change in the corresponding variable (upward = increase; downward = decrease), while red and blue lines represent negative and positive effects, respectively. Some elements of this figure were created in BioRender. B, A. (2025) https://BioRender.com/i51j856.
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