Paddy field conversion to apple orchards reshapes soil nematode communities and ecosystem sustainability in the Kashmir valley

Abstract

The widespread transformation of paddy fields into apple orchards in the Kashmir Valley has prompted significant shifts in above-ground vegetation, which may, in turn, influence the below-ground soil biodiversity-a key indicator of soil health. In this study, we explored the impact of this land-use change on the community dynamics of soil nematodes. Composite soil samples from the surface layer (0–15 cm) were collected from paddy fields (PDF), high-density apple orchards (HDAO), and conventional apple orchards (CAO), with five replicates for each land-use type. From each soil samples 200 g of soil was used for extraction of nematodes by Baerman,s funnel technique. Post-extraction, nematode communities were analyzed based on total abundance, the abundance of five distinct trophic groups, diversity indices, functional indices, and metabolic footprints. A total 45 nematode genera were found to be associated with three land uses. The results revealed an increase in both total nematode density (per 100 g soil) and the density of all five trophic groups following the conversion of PDFs to HDAO and CAO. While alpha diversity at the generic and family levels exhibited homogenization, a decline in diversity was observed at the order level, particularly in CAO. The metabolic footprint analysis indicated enhanced carbon assimilation by nematodes in apple orchards, suggesting an alteration in the functional dynamics of these communities. The results stress that the structural and functional attributes of nematode populations are differentially impacted by the land-use transition. Although there is an increase in the ecosystem services provided by nematodes, the observed loss of diversity at certain taxonomic levels raises concerns. This study provides valuable insights into the impact of paddy field conversions to apple orchards on soil nematode communities, highlighting both structural and functional changes. The findings advance ecological understanding of soil biodiversity responses to land-use changes while offering practical tools for monitoring soil health through trophic and functional indicators. The observed trade-offs enhanced ecosystem services but reduced diversity at certain taxonomic levels emphasize the complexity of biodiversity-function relationships and the need for sustainable land management practices. These results serve as a foundation for guiding future research and informing policies aimed at balancing agricultural productivity with soil biodiversity conservation.