Energy fluxes and ecological functions as influenced by land-use change
Land-use change influenced energy flux through canopy arthropod communities (for individual land-use systems see Supplementary Fig. S7). Total energy fluxes in tree canopies differed significantly between land-use systems (F3,59 = 9.22, p < 0.0001). They were highest in rainforest (1160 ± 1088 kJ ha-1year-1) and jungle rubber (747 ± 586 kJ ha-1 year-1), but significantly lower in rubber and oil palm plantations (293 ± 247 and 342 ± 382 kJ ha-1 year-1, respectively). Importantly, energy fluxes within different trophic groups (algae-microbivores, herbivores and predators), as indicators of different ecological functions, also differed significantly between land-use systems (significant trophic group ⨯ land-use interaction; F6,116 = 6.14, p < 0.0001; Fig. 5). In general, algae-microbivory and herbivory were the dominant feeding strategies in rainforest, jungle rubber and oil palm plantations. Algae-microbivory, indicated by low Δ15N signatures, was highest in rainforest (643 ± 904 kJ ha-1year-1), even exceeding herbivory (306 ± 268 kJ ha-1 year-1). In jungle rubber, herbivory and algae-microbivory were of equal importance, whereas in oil palm plantations herbivory dominated. Interestingly, predation was dominant in rubber plantations, with similarly high fluxes as in jungle rubber, but considerably lower fluxes to herbivory and algae-microbivory. The ratio between herbivory and predation differed between the land-use systems (F3,48 = 7.61, p = 0.0003); it was significantly greater in oil palm (10.9 ± 20.2) than in rainforest, jungle rubber and rubber (3.5 ± 6.3, 3.6 ± 6.3 and 1.9 ± 5.3, respectively). For variations in energy fluxes with landscape and season see Supplementary Chapter S1 and Supplementary Fig. S8.