Life strategies of nematodes determine energy patterns of food webs over 100 Years of primary succession in a salt marsh chronosequence

Understanding nematode community dynamics along succession gradients is critical for predicting ecosystem responses to environmental changes. However, studies on the dynamics of nematode communities and their associated food webs along chronosequences remain limited. We sampled soils along a well-established salt marsh chronosequence that spans more than a century of natural succession, and quantified nematode communities. The result showed that total nematode abundances exhibited a curved relationship with the stage of succession, peaking at intermediate stages. However, the abundance of different trophic and life strategy groups showed different responses to succession due to their specific responses to soil and plant properties. Bacterivores dominated in the early stage, while fungivores and herbivores dominated in the middle stage. Omnivores-carnivores only showed a significant increase in year-7, with no differences across other stages possibly due to high soil salinity suppressing top-down trophic regulation. K-strategist nematodes were more influenced by the stage of succession than r-strategist, correlating strongly with network stability, while r-strategists were more crucial for enhancing network complexity. Additionally, energy flow uniformity, rather than energy flux, in the nematode food webs was significantly correlated with the stage of succession. r-strategists contributed more to energy flux, whereas K-strategists were more essential for flow uniformity. These findings highlight the value of using nematodes as bioindicators to predict ecosystem stability and functions, emphasize the crucial role of nematode life strategists in shifting energy dynamics within nematode food webs during primary succession, and offer valuable guidance for the conservation and management of ecosystems undergoing natural succession.