A New Sensor System Tracks Carbon Emissions From Bamboo Stems and Soil in Real Time
Bamboo may look like a rapid carbon-storage machine, but measuring exactly how much carbon moves through a bamboo forest is surprisingly difficult. Carbon does not enter or leave an ecosystem through leaves alone: living stems respire, roots exchange gases with soil, microbes break down organic matter, and weather can cause emissions to surge or fall within minutes. A study published in Plant Methods reports a new monitoring system designed to capture two of these processes simultaneously—the release of carbon dioxide from bamboo culms and from the surrounding soil. Tested in a stand of Lei bamboo (Phyllostachys praecox) at Zhejiang A&F University in China, the system uses an open-path gas-exchange chamber, ambient-air stabilization and an adaptive algorithm that adjusts airflow according to changing CO₂ concentrations. Over 22 days, the researchers found that the method produced substantially fewer outliers than conventional approaches, potentially offering a more dependable way to observe carbon cycling continuously rather than through occasional snapshots.
The challenge begins with the nature of carbon flux itself. In ecosystem science, a flux is the rate at which a substance crosses a defined area over time. For a bamboo culm, the relevant signal is largely associated with respiration by living tissues, in which stored organic carbon is converted into energy and released as CO₂. Soil flux combines root respiration with microbial decomposition and other biological processes. These rates are often expressed in micromoles of CO₂ per square metre per second, a unit that captures both the quantity of gas and the speed of its movement. Because the signals vary with temperature, moisture, plant growth, oxygen availability and physical disturbance, a measurement made at midday may not represent the rate occurring overnight or after rainfall. Continuous measurements are therefore essential for identifying short-lived peaks and distinguishing biological patterns from instrumental noise.
Existing chamber systems can struggle when they are asked to measure these rapidly changing flows for long periods. In a typical open-path arrangement, a chamber surrounds part of a stem or a patch of soil while air passes through it. Sensors then track the difference in CO₂ concentration between incoming and outgoing air, and the gas flux is calculated from that concentration change and the air-flow rate. The approach avoids some limitations of closed chambers, which can allow CO₂ to accumulate and alter the conditions being measured. Yet open-path systems are sensitive to unstable flow, abrupt environmental changes and imperfect mixing inside the chamber. If the airflow remains fixed while the true biological emission changes, the concentration signal may become too weak, too noisy or systematically biased. Conversely, a flow rate that is too low can permit excessive accumulation, while one that is too high can dilute the signal and make small changes difficult to detect.
The system developed by Junjie Jiang, Junguo Hu and colleagues addresses this problem by linking gas-flow control directly to the concentration being measured. Its central component is a concentration-feedback adaptive controller described by the researchers as a logarithmic proportional-integral, or log-PI, control algorithm. A proportional-integral controller continuously compares a measured value with a desired target and adjusts an actuator—in this case, the air-handling system—to reduce the difference. The proportional component responds to the current error, while the integral component accumulates error over time and helps eliminate persistent offsets. The logarithmic treatment changes how the controller responds across different concentration ranges, allowing it to regulate changes without applying the same absolute correction to every signal. In principle, this enables the chamber to remain within a useful operating range while adapting to fluctuations in the carbon flux itself.
An ambient-air stabilization unit provides a second layer of control. Outdoor air is not chemically or physically constant: wind, temperature and nearby biological activity can alter the air entering a chamber. By stabilizing the incoming air before it reaches the measurement region, the system aims to reduce fluctuations that might otherwise be mistaken for changes in stem or soil respiration. The chamber and control algorithm work together rather than treating airflow as a fixed experimental setting. The researchers call the resulting platform the ACM system, for synchronous measurement of bamboo culm and soil carbon fluxes. Its purpose is not simply to collect more readings, but to make each reading less vulnerable to disturbances that can accumulate during unattended monitoring.
The team evaluated the ACM system during a 22-day observation from 10 February to 3 March 2026, comparing its performance with two other arrangements. One was a conventional fixed-flow system, referred to as NCM, in which the airflow is not dynamically adjusted in response to the concentration signal. The other was a non-steady-state intermittent monitoring system, or NSM, which samples at intervals rather than maintaining continuous observation. The test was conducted in a Lei bamboo stand at Zhejiang A&F University. The study did not present the new platform as a universal replacement for every carbon-flux method; instead, it examined whether adaptive flow regulation could improve stability and data quality under field conditions. That distinction matters because instruments can perform well in a controlled trial yet behave differently across seasons, soil types, bamboo ages and weather regimes.
Across the monitoring period, the ACM system measured a daily mean CO₂ flux from bamboo culms of 0.079 ± 0.018 micromoles per square metre per second. The corresponding daily mean soil flux was 1.196 ± 0.145 micromoles per square metre per second. The soil value was therefore much larger than the culm value in this experiment, reflecting the combined activity of roots and soil organisms across the measured surface. The figures are averages with associated variability, not fixed physiological constants: they describe the conditions and observation window of this particular bamboo stand. Even so, measuring both fluxes at the same time provides information that a single measurement stream cannot. A forest may absorb carbon rapidly through photosynthesis while simultaneously returning some of it to the atmosphere through stem and soil respiration. Separating those pathways is necessary for building a meaningful carbon budget rather than treating the ecosystem as a single undifferentiated source or sink.
The most striking performance result concerned outliers. In the ACM data, outlying observations represented just 0.1 per cent of bamboo-culm flux measurements and 0.2 per cent of soil-flux measurements. The researchers report that these proportions were significantly lower than those recorded by both the fixed-flow NCM system and the intermittent NSM approach. Outliers matter because a small number of erroneous values can distort daily averages, obscure biological responses and create false evidence of sudden carbon release. Adaptive regulation appears to have helped by preventing the chamber from drifting into conditions where concentration changes were either overwhelmed by high-frequency noise or distorted by unstable gas exchange. The system’s ability to suppress rapid fluctuations is particularly relevant for long-term deployments, when there may be no technician present to identify a blocked line, a changing wind pattern or a mismatch between flow and emission rate.
The findings could make bamboo forests easier to include in broader assessments of terrestrial carbon cycling, but important questions remain. The experiment covered only 22 days and one species at one location, during a winter-to-early-spring interval. Bamboo culms, soils and atmospheric conditions may behave differently during summer heat, monsoon rainfall, drought or periods of rapid shoot growth. The study also focuses on measurement reliability rather than demonstrating how the new data change estimates of annual carbon storage. Future tests would need to examine sensor drift, maintenance requirements, power consumption, chamber effects on the enclosed tissue or soil, and performance across different stem diameters and forest structures. The authors nonetheless suggest that the approach could be adapted to stems of other woody plants. If its low-outlier performance can be reproduced across those settings, flow-adaptive monitoring could provide a valuable bridge between brief chamber measurements and the continuous, high-frequency records needed to understand how forests exchange carbon with the atmosphere.
Subject of Research: A flow-adaptive synchronous monitoring system for measuring carbon dioxide fluxes from bamboo culms and soil
Subject of Research: Agriculture
Article Title: Bamboo culm and soil carbon flux synchronous measurement system: a continuous monitoring technique incorporating flow adaptive algorithms
Article References: Jiang, J., Hu, J., Cui, Y. et al. “Bamboo culm and soil carbon flux synchronous measurement system: a continuous monitoring technique incorporating flow adaptive algorithms.” Plant Methods (2026). Original research article Original publication
Image Credits: AI Generated
DOI: 10.1186/s13007-026-01589-4
Keywords: bamboo carbon flux, soil respiration, culm respiration, open-path gas-exchange chamber, flow-adaptive algorithm, log-PI control, continuous monitoring, terrestrial carbon cycle
Tags: adaptive gas-exchange chamber technologyadaptive sensor system for ecosystem carbon trackingbamboo carbon flux monitoringcarbon emission dynamics in bamboo ecosystemscarbon flux variability in bamboo ecosystemscontinuous carbon cycling in bamboo forestscontinuous carbon cycling observation in bamboo forestsenvironmental sensor systems for climate change researchenvironmental sensors for greenhouse gas monitoringhigh-frequency carbon emission data collectionimpact of weather variability on carbon flux measurementsinnovative methods for ecosystem carbon assessmentinnovative methods for ecosystem carbon budget assessmentlong-term monitoring of terrestrial carbon exchangesmicrobial decomposition of organic matter in soilmicroclimate influence on carbon emissionsopen-path gas sensors for ecosystem studiesopen-path gas-exchange chambers for carbon monitoringplant-microbe-soil interactions in carbon cyclingreal-time soil and bamboo stem CO2 emission measurementsoil respiration and plant respiration measurementsoil respiration and plant respiration measurement techniques
