Unraveling the influence of litter identity, diversity and rhizodeposition on nematode communities

Delving into the regulation of soil biota and function by plants provides a comprehensive understanding of ecosystem processes, offering insights into nutrient dynamics, soil food web dynamics, soil health, and the overall functioning. However, many aspects regarding the influence of plant roots, litter identity, and diversity on nematode diversity and communities, as well as the relative contributions of plant litter and roots resources to nematode diversity and community dynamics, remain poorly understood.

To address these knowledge gaps, we conducted two interconnected experiments. Firstly, we collected litter from eight different vascular plant species and performed a pot experiment to examine the effects of litter identity on nematode diversity and community composition. Subsequently, using a subset of these species, we established litter diversity gradients with five treatments: control (litter removed), 1 species, 2 species, 4 species and 6 species mixtures in a field experiment to investigate the impacts of litter diversity and rhizodeposition (which includes root abscissions and exudates) on nematode diversity and communities. Through high-throughput sequencing and sequence alignment, nematodes were identified at the family level. Based on nematode count data, sequence relative abundances were converted into absolute nematode quantities for diversity and community analyses.

Our results revealed that the removal of litter led to a significant reduction in total soil organic carbon (TOC), whereas rhizodeposition significantly increased TOC and NH₄⁺ levels. Rhizodeposition and litter addition both positively influenced nematode abundance, primarily by regulating bacterial-feeding and plant-feeding nematode populations. Additionally, nematode diversity showed significant responses to rhizodeposition, litter identity, and diversity. Excluding rhizodeposition resulted in significant reductions in the diversity of all nematode trophic taxa groups, except for fungal-feeding nematodes. Furthermore, our findings indicated that plant litter identity had a distinct effect on nematode communities, with Alchornea davidii and Rhododendron simsii emerging as the most impactful plant species for shaping these distinct nematode communities. In addition, both litter diversity and rhizodeposition exerted significant effects on nematode communities. Notably, the dissimilarity in nematode communities was significantly greater between rhizodeposition and without rhizodeposition than among different litter diversity treatments, indicating rhizodeposition had a notably stronger impact than litter diversity.

Overall, the findings highlight the dominant role of plant roots and litter identity over litter diversity in shaping nematode communities, providing new insights into how plants sustain complex and highly diverse soil biota.