Seasonal and land-use impact on the stable isotopic signatures of termites

Abstract

Stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes are valuable tools for elucidating termite trophic positions within soil food webs. However, the impact of land-use changes on these signatures of termites has seldom been explored. Here, we collected termites (Odontotermes mathuri) and their food resources to assess the effects of season and land-use type on the stable isotopic signatures of termites. Land-use type significantly influenced the δ¹³C signatures of termites, particularly in workers. For termite δ¹⁵N signatures, we found significantly higher values during the dry season compared to the rainy season. Furthermore, δ¹⁵N values were significantly higher in monoculture rubber plantations and primary rainforest sites than in jungle rubber agroforests, representing different land-use types. These differences are likely attributed to seasonal and land-use driven changes in food sources and their nutritional quality. This was further validated by positive correlation between δ¹⁵N values of termites and their food resources (woody debris and litter). There was no significant difference between the δ¹³C and δ¹⁵N signatures of termite soldiers and workers because the workers initiated trophallactic exchanges with soldiers. Our findings indicate that both season and land-use type influence termite δ¹⁵N signatures by altering the availability and composition of food resources. These results underscore the importance of incorporating stable isotope analyses in assessments of land-use change impacts on soil fauna and trophic interactions.