Rainforest conversion to plantations fundamentally alters energy fluxes and functions in canopy arthropod food webs

Abstract

Tropical rainforests around the world are rapidly being converted into cash crop agricultural systems. The associated massive losses of plant and animal species lead to changes in arthropod food webs and the energy fluxes therein. These changes are poorly understood, in particular in the extremely biodiverse canopies of tropical ecosystems. Using canopy fogging followed by stable isotope and energy flux analyses, we show that land‐use conversion from rainforest to rubber and oil palm plantations not only causes a drastic reduction in energy fluxes of up to 75%, but also shifts fluxes among trophic groups. While rainforest featured high levels of both herbivory and algae‐microbivory, and a balanced ratio of herbivory to predation, relative fluxes were shifted towards predation in rubber and towards herbivory in oil palm plantations, indicating profound shifts in ecosystem functioning. Our results highlight that the ongoing loss of animal biodiversity and biomass in tropical canopies degrades animal‐driven functions and restructures canopy food webs.

Tree species identity, canopy structure and prey availability differentially affect canopy spider diversity and trophic composition

“…High ∆ 13 C values indicate that the food web is fueled by detrital resources (“detrital shift”; Potapov et al 2019 ), whereas low ∆ 13 C values indicate a rather herbivore-fueled food web (Krause et al 2021 ; Wildermuth et al 2023 ). This suggests that prey organisms in conifer canopies predominantly consume decaying material, microbes and fungi, while prey in beech stands mostly consume living leaves (Pollierer et al 2023 ). However, the observed ∆ 13 C patterns may also reflect different feeding strategies of tree species specific herbivore communities, such as the selective use of easy to digest plant compounds with high ∆ 13 C (Pollierer et al 2023 ).…”

“…This suggests that prey organisms in conifer canopies predominantly consume decaying material, microbes and fungi, while prey in beech stands mostly consume living leaves (Pollierer et al 2023 ). However, the observed ∆ 13 C patterns may also reflect different feeding strategies of tree species specific herbivore communities, such as the selective use of easy to digest plant compounds with high ∆ 13 C (Pollierer et al 2023 ). High ∆ 15 N values in beech stands hint toward an additional trophic level compared to coniferous stands (Scheu and Falca 2000 ), likely reflecting more pronounced intra-guild predation in beech (Wildermuth et al 2023 ).…”

“…5 d). Such a top-heavy food web as in beech may be explained by the phenology of deciduous trees, which do not provide resources for herbivores during winter (Pollierer et al 2023 ). This also indicates that pest control provided by spiders may be more pronounced in beech than in coniferous stands, even though spiders are more abundant in conifers.…”

Four new species of Utivarachna Kishida, 1940 (Araneae: Trachelidae) from Sumatra

“…Using canopy fogging, 48 Utivarachna specimens were collected in Jambi Province, Sumatra, Indonesia, in the dry season of 2013. The specimens were found in a collection of more than half a million canopy arthropods (Pollierer et al, 2023), stemming from 96 individual canopy fogging events in 32 permanent research plots of the EFForTS project (Drescher et al, 2016). Research plots were evenly distributed among four land-use systems: lowland rainforest, "jungle rubber" (extensively managed rubber agroforest), and smallholder monocultures of (H. brasiliensis) and oil palm (E. guineensis).…”

“…Overall, more than 10,000 spider individuals from more than 30 families and at least 400 species were found among the more than half million canopy arthropods (Ramos et al 2022). More details on the plot design and the EFForTS research framework is given in Drescher et al (2016), on the canopy fogging method in Pollierer et al (2023), and on biodiversity patterns of the collected canopy spider community in Ramos et al (2022).…”