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

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 rainforests featured high levels of both herbivory and algae-microbiology, 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.All statistical analyses were conducted with R version 4.1.0 (2021-05-18) "Camp Pontanezen". Funding provided by: Deutsche ForschungsgemeinschaftCrossref Funder Registry ID: http://dx.doi.org/10.13039/501100001659Award Number: 192626868–SFB 990Study region and experimental design Canopy arthropods were collected from research plots (n =32) of the EFForTS (Ecological and Socioeconomic Functions of Tropical Lowland Rainforest Transformation Systems) project in the lowlands of Jambi Province, Sumatra, Indonesia (Supplementary Fig. S1; Drescher et al. 2016), a region dominated by smallholder cash crop agriculture (Clough et al. 2016). Eight 50 m ⨯ 50 m plots each were established in three of the most dominant agricultural land-use systems in Jambi Province, i.e. monocultures of rubber (Hevea brasiliensis), oil palm (Elaeis guineensis), and jungle rubber (rubber agroforest system in gradually degrading rainforest remnants; Rembold et al. 2017), as well as in lowland rainforest as control habitat (Supplementary Fig. S2). The 32 research plots were located within and around two lowland rainforest reserves, i.e. the Bukit Duabelas National Park and the Harapan Rainforest, which are covered by degraded primary rainforest (Margono et al. 2014). The plots inside and near Bukit Duabelas National Park are referred to as belonging to the "Bukit Duabelas landscape", while the research plots inside and near Harapan rainforest are affiliated to the "Harapan landscape" (Drescher et al. 2016). Sampling and analyses of canopy arthropods and leaves Arthropods were collected by canopy fogging, using the SwingFog® SN50 fogger (Swingtec GmbH, Germany) to apply a mixture of 50 mL DECIS 25 EC® (Bayer Crop Science, deltamethrine 25g/L) and four litres petroleum white oil to tree and palm canopies (Fig. 1). Three target canopies were fogged per 50 m ⨯ 50 m plot, located randomly but >20 m apart from each other; fallen trees and canopy gaps were avoided. Canopy fogging was conducted twice in the dry and rainy seasons of 2013 and 2013/14, respectively. Fogging was conducted in dry conditions and took about 20 min for each ~4L mix of while oil with insecticide. It began no later than 7:00 am for the first within-plot replicate and stopped before 9:00 am for the third replicate to avoid turbulences caused by rising daytime temperature above the canopy. Sixteen 1 m x 1 m fogging trays were arranged around a central tree or palm in a circle which was within 1 m from the trunk with its inner edge (Fig. S2 A, B). Each tray was fitted with a 250 mL plastic bottle containing 100 mL 96% EtOH (Fig. S2 C, D). Insecticide coverage was optimized by the person operating the fogger with the assistance from two observers on opposing sides of the target canopy. This ensured complete coverage of the canopy in rubber and oil palm; coverage in jungle rubber and rainforest was lower due to the insecticide plume dissolving with increased height. Typically, the fogging tray circles were underneath one oil palm, 2–3 in rubber trees and >5 trees in jungle rubber and rainforest. Two hours after fogging, stunned or dead arthropods were collected from the fogging trays, cleaned from debris, the EtOH exchanged and the samples stored at -20°C. Collected arthropods were sorted to orders, of which we used the 12 major ones in this study: Acarina, Araneae, Blattodea (without termites), Coleoptera, Collembola, Diptera, Hemiptera, Hymenoptera (Formicidae, Braconidae), Lepidoptera, Orthoptera, Psocoptera and Thysanoptera. Other, large-bodied arthropod taxa (e.g., Myriapoda, Mantodea, Phasmatodea, Scorpiones) were excluded from the analysis due to inefficiency of the insecticide (J. Drescher, pers. obs.). Termites were not included as their highly patchy distribution (0 – 66,084 individuals per plot across the two seasons) reflects that they were inadequately sampled (Jones & Eggleton 2000). Hymenoptera in this study are represented by Formicidae (ants) and Braconidae (a dominating family of parasitoid wasps; Azhar et al. 2022). Within Coleoptera, the four most abundant families Chrysomelidae, Curculionidae, Elateridae and Staphylinidae (Kasmiatun et al. 2022), which contract in feeding strategies, were separately analysed from 'other Coleoptera'. Average body length and width were measured for 15 (or if <15 in the sample as many as present) randomly selected individuals from each order/family at plot-level in the dry and rainy season. Biomasses (fresh weight) per square metre were calculated using taxon-specific regressions (Supplementary Table S1). To calibrate stable isotope measurements of canopy arthropods to their potential basal resource, five randomly selected leaves per plot at head height were collected. In rainforest, leaves were from five tree species; in jungle rubber, two were from rubber trees and three from other tree species. In rubber, one leaf each was collected from the five rubber trees closest to the plot centre. In oil palm, we collected 40 cm2 leaf material from five different oil palms closest to the plot centre. Stable isotope ratios of carbon and nitrogen (13C/12C and 15N/14N), and C-to-N ratios were measured for pooled leaves from each plot (Supplementary Table S2) and for 15 (or if