Food web structure in exotic eucalyptus plantations in Southern China: Stable isotope (δ13C, δ15N) analyses reveal the importance of understory and landscape-level planning

Abstract

Abstract Exotic eucalyptus (Eucalyptus spp.) has been planted widely as a fast-growing tree species in numerous tropical and subtropical countries. The expansion of eucalyptus plantations has caused several issues affecting biodiversity, such as loss of species within communities as well as alterations to ecosystem function. Previous studies of biodiversity in eucalyptus plantations have focused on single biological groups or trophic levels. How the whole biological community and trophic interactions within these plantations are affected is still poorly known. We conducted a comprehensive collection of primary producers and consumers from 42 eucalyptus plantations planted between one and 25 years ago. Primary producers, including plant materials and soil organic matter, showed significant differences in both δ13C and δ15N values. Values of δ13C and δ15N of consumers from eucalyptus plantations varied from −30.2‰ to −18.6‰ and from −1.9‰ to 8.4‰, respectively. Both δ13C and δ15N values of consumers differed among five trophic groups that we identified in eucalyptus plantations. Trophic levels in eucalyptus plantations were estimated from 1.4 to 4.4. Stable isotope evidence showed that leaves of both exotic eucalyptus, understory and adjacent sugarcane, contributed to the consumer food webs. Our results suggested food webs associated with eucalyptus plantations had complete trophic structure and depended on a suite of food sources. Nutrient inputs were typically also derived from adjacent areas indicating that maintaining diversity at the landscape level is needed to augment biodiversity and functioning of foodwebs in eucalyptus plantations.