Data Sheet 1_Mixed seeding with sheep manure amendment alters soil nematode network complexity in a sandy grassland.docx

Introduction<p>Soil nematodes are key bioindicators of terrestrial ecosystem functions, yet how restoration practices affect their community and interactions remains unclear.</p>Methods<p>A one-year field experiment in an alpine grassland tested three treatments: bare sandy soil, mixed seeding of Avena sativa L. and Festuca arundinacea, and mixed seeding with sheep manure amendment at 1.75 kg m^-². Notably, the experimental design did not include a sheep-manure-only treatment; therefore, the specific contribution of manure independent of vegetation reconstruction cannot be disentangled.</p>Result<p>High-throughput sequencing and co-occurrence network analysis revealed that mixed seeding with manure significantly enhanced plant biomass, soil organic carbon, electrical conductivity, and nematode richness (Chao1 index) by 26.36-31.58% (p < 0.05).

Mixed seeding alone increased the relative abundance of predator/omnivore nematodes by 17.46%, whereas mixed seeding with sheep manure shifted the community toward opportunistic bacterivores such as Acrobeloides and reduced predators/omnivores by 15.74% (p < 0.05). Available nitrogen showed the strongest marginal association with community composition (Monte Carlo test, p = 0.065). Network analysis indicated that mixed seeding promoted the key genus Aporcelaimellus, while adding manure shifted the network architecture toward bacterivores dominance.</p>Discussion<p>Both the mixed seeding treatment and the mixed seeding combined with manure treatment enhanced network complexity but increased competition over cooperation, reflecting altered interaction patterns.