Changes in soil free-living nematode communities and their trophic composition along a climatic gradient

Abstract

Ambiguity exists concerning the effects of cli- mate on soil nematode-community composition. In this study, we examined the free-living nema- tode communities in soil along a climatic gra- dient representing humid-Mediterranean, Medi- terranean, semi-arid, and arid climate types. The relationships between abiotic soil characteris- tics (organic carbon, soil moisture (SM), wa- ter-holding capacity) and nematode parameters, such as abundance, trophic group composition, and diversity indices, were explored in the con- text of climate and seasonality. Nematode abun- dance was lowest at the arid site. At the humid- Mediterranean and Mediterranean locations, ne- matode abundance reached its peak in winter, while at the semi-arid and arid sites, an almost opposite trend was observed, with lowest abun- dances in winter, presumably due to a nutrient washout from the soil profile during the rainy season. On the trophic level, one trophic group demonstrated a positive correlation with SM and one trophic group demonstrated a negative one at each location, while the other two groups remained constant. Fungi-feeding nematodes were found to be unaffected by SM at the humid- Mediterranean and Mediterranean locations, while at the semi-arid and arid sites their proportion increased in correlation with decreasing SM. Bacteria-feeders increased with SM at the arid site, were unaffected at the semi-arid location, and decreased with SM at the humid-Mediter- ranean and Mediterranean sites. Plant-parasites were associated with SM only at the humid- Mediterranean site. Omnivores-predators were positively affected by SM at the two middle locations, staying constant at the humid-Medi- terranean and arid sites. These findings point to the strong linkage existing between nematode trophic behavior and climatic factors, demonstrating distinctive communal fingerprints for each climate type.