Low-cost autonomous chambers enable high spatial and temporal resolution monitoring of soil CO₂ exchange across landscapes

Jonathan Gewirtzman , Ashley Keiser, Matthew A Nieland, Corey Palmer, Vatsal Patel, Kelly Caylor, Elizabeth Forbes

1. Soil CO₂ flux is a critical component of ecosystem carbon cycling, but due to high cost and mechanistic constraints, existing measurement systems are often limited by trade-offs between resolution (temporal and spatial), and spatial coverage. These constraints hinder efforts to monitor soil fluxes across diverse, heterogeneous landscapes and environmental gradients.
2. We developed Fluxbot 2.0, a low-cost, autonomous chamber system capable of continuous, distributed soil CO₂ flux measurements without external power or infrastructure. To assess its capability to capture landscape-scale variability, we deployed two Fluxbot 2.0 arrays, one at each of two hemlock forest sites in Harvard Forest, Massachusetts, USA, and compared its estimates of flux to those from existing, well-established automated chamber arrays that rely on multiplexed chambers and high-accuracy CO2 analyzer units.
3. Fluxbots successfully captured site means, spatial variability, temporal patterns, and environmental responses, including temperature-driven flux dynamics. These measurements reflected differences in forest conditions between two sites and showed that distributed arrays of low-cost sensors can effectively capture both fine-scale variability and broader patterns across a landscape.
4. By enabling low-cost, autonomous monitoring of soil carbon flux in strategically distributed arrays, Fluxbot 2.0 addresses key gaps in existing soil CO₂ flux datasets. The system facilitates measurements across environmental gradients and heterogeneous landscapes, supporting research on soil carbon dynamics and biotic interactions that influence carbon cycling.