The conversion of tropical rainforests into agricultural land, driven primarily by the expansion of commodity crops like oil palm and rubber, poses a significant threat to global biodiversity. While biodiversity loss in terrestrial ecosystems is well-documented across various biomes and trophic levels, the functional and energetic consequences of these transformations, particularly within the complex web of interactions in tropical ecosystems, remain largely unknown. This study addresses this knowledge gap by focusing on the energetic consequences of rainforest conversion, aiming to understand how land-use change alters energy flow and distribution across aboveground and belowground food webs. The research is crucial because energy, as the fundamental currency of life, directly impacts the number of species an ecosystem can support and how biodiversity is distributed across different trophic levels and ecosystem compartments. Previous studies have shown correlations between biodiversity loss and energy flux changes in various ecosystems, but the complex interactions between aboveground and belowground components in tropical systems require more integrated analysis. This study hypothesizes that key energetic roles shift between rainforest and plantations, resulting in distinct energy allocations across different strata, trophic levels, and resource types, with consequences at the ecosystem level. Understanding these changes is vital for designing effective strategies for restoring ecosystem functioning and conserving biodiversity in transformed tropical landscapes.

Existing literature extensively documents biodiversity losses due to land-use change, particularly in tropical ecosystems. Studies have shown cascading effects of agricultural monocultures, resulting in drastic declines in plant diversity and subsequent impacts on higher trophic levels, including invertebrates and vertebrates. The mechanistic understanding of these impacts, however, often lacks a detailed analysis of food web dynamics across multiple trophic levels and ecosystem compartments. Several studies have explored the relationship between biodiversity loss and energy flux, revealing that in some systems, biodiversity decline correlates with reduced total energy flux, while in others, it's associated with energy redistribution across the food web. The energy flux approach provides a valuable metric for quantifying the flow of energy through ecological networks and its impact on biodiversity. This study builds upon previous work by explicitly integrating aboveground and belowground food webs in tropical ecosystems, providing a more comprehensive understanding of the energetic consequences of land-use change.

The study quantified energy fluxes across earthworms, birds, and arthropods in soil and canopies of Sumatran rainforests and plantations. The research design included 32 sites representing rainforests and three types of plantations: jungle rubber (selectively logged rainforest with rubber trees), rubber monoculture, and oil palm monoculture. To estimate animal abundance and biomass, researchers employed various methods: insecticide fogging for canopy arthropods, audio recorders and point counts for birds, and high-gradient heat extraction from soil cores for soil arthropods and earthworms. Data on body mass and biomass were linked to literature data on feeding preferences and traits to define 62 trophic guilds and reconstruct food-web topologies at each site. Steady-state food-web modeling was used, assuming that the energetic demands of each guild are compensated by energy uptake from lower trophic levels. Metabolic rates were estimated from body masses using metabolic regressions and multiplied by observed biomasses. The resulting energy fluxes were used as quantitative measures for energy distribution and consumption of different resources (living plants, litter, bacteria, fungi, soil organic matter, and other animals). A validation survey was conducted four years after the main survey (except for jungle rubber sites) to verify the generality of the findings. The study utilized statistical analyses including generalized linear mixed-effects models to analyze the data and draw conclusions about the impact of land-use change on the energy fluxes and food web structure.

The study revealed several key findings: 1. **Energetic Dominance of Belowground Food Webs in Rainforests:** Rainforests channel most energy belowground; total belowground energy flux was 14 times higher than aboveground flux. 2. **Keystone Group Shifts in Plantations:** Plantations exhibit similar or higher total energy flux than rainforests but drastically alter energy distribution. Earthworms become dominant energy channels (60-79% of energy flux), replacing the diverse arthropod communities of the rainforest. 3. **Aboveground vs. Belowground Responses to Land-Use Change:** Land-use change caused a 75-79% decline in aboveground energy flux but relatively little change in belowground energy flux. This resulted in an even greater disparity in energy distribution between aboveground and belowground compartments in plantations. 4. **Predation Decline in Plantations:** Predation-to-primary consumption ratios decreased significantly across both aboveground and belowground food webs, except for a surprising high predation in rubber canopies, possibly associated with abundant blood-sucking insects. 5. **Changes in Belowground Carbon Cycling:** Land-use change altered energy distribution at the base of belowground food webs. Bacterivory and soil feeding increased while herbivory and fungivory decreased, indicating a shift towards faster energy channeling and potentially accelerated carbon depletion, reflected in decreased faeces production to soil consumption ratio. The bacteria/fungi energy flux ratio increased 3.2 to 4.4 times in plantations. 6. **Validation Survey:** A follow-up survey partially confirmed the main findings but also showed the potential for partial restoration of certain trophic links over time.

The study's findings provide compelling evidence for the profound energetic consequences of rainforest transformation. The shift from arthropod-dominated to earthworm-dominated belowground food webs in plantations highlights the substantial functional restructuring associated with land-use change. The decrease in predation and increase in herbivory suggests a reduction in natural pest control mechanisms, possibly increasing vulnerability to pest outbreaks. The altered carbon cycling, with a shift towards faster bacterial pathways and decreased faeces production, is consistent with observations of soil carbon depletion in these systems. The differences in responses between aboveground and belowground systems emphasize the need for integrated management strategies that address both compartments. While plantations may maintain similar or even higher total energy flux, this energy is disproportionately allocated to basal trophic levels, supporting far less biodiversity than rainforests.

This research provides a crucial energetic perspective on the impacts of tropical land-use change, revealing profound shifts in food web structure, energy distribution, and carbon cycling. The findings underscore the need for more integrated and compartment-specific restoration strategies that go beyond merely focusing on increasing total energy flux. Future research should explore the long-term effects of land-use change, the effectiveness of various restoration techniques on food web structure and function, and the potential for restoring the energetic balance across aboveground and belowground compartments.

The study focuses on a specific region in Sumatra, Indonesia, and the results may not be fully generalizable to other tropical regions. The study's food web reconstruction relies on existing literature data on trophic interactions, which might include uncertainties. While a validation survey was conducted, the time frame of the study might not fully capture long-term ecosystem dynamics and the recovery of certain trophic links over time.