Linking soil nematode communities to plant- and microbial-derived carbon in a 15-year field experiment

Abstract

Soil nematodes show the highest abundance among animals on Earth, which can affect plant residue decomposition by influencing plant roots and soil microbes, thus affecting plant- and microbial-derived carbon (C) sequestration. However, the relationships between soil nematodes, plant- and microbial-derived C under long-term fertilization remain unclear. The present work performed a 15-year field fertilization experiment (including four treatments: (1) no fertilizer (CK); (2) nitrogen, phosphorus, and potassium fertilizers (NPK); (3) NPK with straw (SNPK); and (4) NPK with pig manure (MNPK)) for investigating how soil nematodes affected soil plant- and microbial-derived C by determining soil nematode, bacterial, and fungal abundances as well as amino sugar and lignin phenol contents (their biomarkers), and their associated relationships. The results revealed that SNPK treatment increased the abundances of soil bacterivores and bacteria as well as the bacterial necromass C (BNC) content. As revealed by partial least squares path modeling (PLS-PM), bacterivores showed indirect and positive impacts on BNC through influencing the abundance of bacteria. Moreover, SNPK treatment increased fungal abundance and fungal necromass C (FNC) content but did not alter fungivore abundance. FNC was significantly and positively correlated with fungal abundance and bacterivore abundance. PLS-PM revealed that BNC indirectly influenced FNC by affecting fungal abundance; thus, bacterivores play an important role in affecting FNC by affecting BNC. Moreover, all the fertilization treatments increased the lignin phenol content, which was significantly and positively correlated with the bacterivore and plant parasite abundances, indicating that the elevated bacterivore and plant parasite abundances during fertilization may contribute to the formation of plant-derived C. Overall, these findings provide insights for developing fertilization strategies that utilize nematode-mediated C pathways to enhance soil C sequestration in agricultural systems.

Graphical abstract

Keywords

soil nematodes / soil organic C / microbial necromass / fertilization

Highlight

	● Fertilization boosts bacterivores, enhancing plant- and microbial-derived C formation.
	● Fungal necromass C is influenced by bacterivores rather than fungivores.
	● Plant-derived C was positively correlated with bacterivores and plant parasites.

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