氮磷添加对黄土旱塬农田土壤线虫群落及能量结构的影响

为探究氮磷添加对黄土旱塬农田土壤线虫群落结构和微食物网中能量流动的影响,以中国科学院长武农业生态实验站长期施用氮磷肥农田土壤作为研究对象,选取6个处理,分别为:不施肥(CK),氮添加(N₁₂、N₂₄),磷添加(P₁₂、P₂₄),氮磷添加(N₁₂P₁₂),测定土壤理化性质,采用浅盘法分离线虫,分析线虫营养类群结构和生活史征,并计算线虫生态学指数,代谢足迹和食物网内部能量流动数值。结果表明:不同处理土壤的植物寄生线虫(Pp)比例显著高于其他类群(50.7%-66.4%),生活史为低营养级r策略者(cp2)的线虫类群比例也显著高于其他类群(68.1%-84.0%)。P₁₂处理的线虫丰度最高,为1147条/100 g干土,其次是P₂₄处理,为1100条/100 g干土。与CK相比,两种磷添加处理显著增加了香农多样性指数(H),提升了食真菌和捕食杂食线虫的代谢足迹,微食物网中拥有更高的能量通量,其余处理对线虫丰度和代谢足迹没有产生影响。与N₂₄处理相比,N₁₂处理显著增加了线虫群落的H,均匀度指数(J)和丰富度指数(SR)。N₁₂P₁₂处理增加了高营养级k策略者(cp4-5)的线虫数量,显著提高了结构指数(SI)。冗余分析表明,土壤中全磷和速效磷含量是影响线虫丰度和代谢足迹的主要环境因子。综上所述,适量氮添加提升了土壤线虫群落多样性和结构稳定性,过量氮添加会抵消这种积极影响。磷添加对线虫群落和代谢足迹产生积极影响并提高了土壤微食物网的能量通量,氮磷添加则为土壤线虫创造了适宜的生存环境。这一结果为黄土区农田土壤的施肥措施提供了科学依据。

Effects of nitrogen and phosphorus addition on soil nematode communities and energy structure in Loess Plateau farmland

To investigate the effects of nitrogen (N) and phosphorus (P) additions on the soil nematode community structure and energy flow within the micro food web in dryland farmland ecosystems of Loess Plateau, this study focused on the long-term application of N and P fertilizers at Changwu Agricultural Ecology Experimental Station of the Chinese Academy of Sciences. Six treatments were selected, including no fertilizer application (CK), N addition (N₁₂, N₂₄), P addition (P₁₂, P₂₄), and NP addition (N₁₂P₁₂). Soil physicochemical properties were measured, nematodes were isolated utilizing the shallow disc method, subsequent analysis encompassed the evaluation of nematode trophic taxa structure and life history traits. Additionally, the computation of nematode ecological indices, metabolic footprints, and internal energy flow within the food web were calculated. The results demonstrated that the proportion of plant parasitic nematodes (Pp) was significantly higher in different treated soils than other taxa (50.7%-66.4%). Furthermore, the proportion of nematode taxa with a life history of cp2 was also significantly higher than the other taxa (68.1%-84.0%). The highest nematode abundance was recorded in P₁₂ treatment with 1147 ind./100 g of dry soil followed by P₂₄ treatment with 1100 ind./100 g of dry soil. Compared to the CK treatment, two P addition treatments significantly increased the Shannon diversity index (H), enhancing the metabolic footprints of fungivorous and predatory-omnivorous nematodes. This resulted in a higher energy flux within the micro-food web, indicating an increased energy flow. The remaining treatments did not exhibit any significant effects on nematode abundance and metabolic footprints. In comparison with the N₂₄ treatment, the N₁₂ treatment showed a significant increase in the H of the nematode community, as well as the evenness index (J) and richness index (SR). Furthermore, the N₁₂P₁₂ treatment led to an increase in the number of nematodes in the cp4-5 category and significantly improved the structural index (SI). The redundancy analysis revealed that the total phosphorus and available phosphorus contents in the soil were the primary environmental factors influencing the abundance and metabolic footprints of nematodes. In summary, the moderate N addition enhances soil nematode community diversity and structural stability, while excessive N addition counteracts these beneficial effects. P addition positively influences both nematode communities and metabolic footprints, leading to an increase in energy flux within the soil micro food web. The NP addition creates a suitable habitat for soil nematodes. These findings provide a scientific basis for fertilizer management practices in agricultural soils of loess regions.