Changes in CO2 Exchange and Influential Factors in an Apple Orchard Over Time

Apple orchards in Liaoning, a key apple-producing area in Bohai Bay, Northeast China, significantly affect carbon sinks, reports Natural Science. There is limited data on carbon flux variations and the factors affecting them in these orchards. To fill this gap, researchers from Shenyang Agricultural University conducted a study monitoring CO2 flux data during the entire apple growth seasons from April to November in 2017 and 2018. The research aimed to examine variations in net ecosystem exchange (NEE) over different time scales and its response to environmental factors.

The energy balance ratio, reflecting the equilibrium of incoming and outgoing energy within the ecosystem, was calculated for the orchard. The analysis revealed energy balance ratios of 0.74 in 2017 and 1.38 in 2018. These ratios illustrate how energy inputs and outputs are balanced in the orchard ecosystem.

The NEE, which measures the balance between CO2 absorbed via photosynthesis and CO2 released through respiration, showed general trends. Positive NEE values occurred in April and November, while negative values persisted from May to October. This outcome suggests that the apple orchard functions as a robust carbon sink during the growth season. The daily average NEE ranged from -0.103 to 0.094 mg m⁻² s⁻¹ in 2017 and -0.134 to 0.059 mg m⁻² s⁻¹ in 2018. The lowest values were recorded in June and July, indicating higher CO2 absorption in these peak growing months.

The study also indicated that NEE was negatively correlated with net radiation, atmospheric temperature, saturated vapor pressure deficit, and soil temperature. Increased levels of these environmental factors corresponded with lower NEE values, revealing enhanced CO2 uptake by the orchard.

These findings are consistent with earlier studies from different regions. Research on apple orchards in the Loess Plateau revealed negative NEE values (indicating a functioning carbon sink) during the same growth season. Furthermore, annual NEE results in that area were higher in 2016 than in 2017, with increased orchard CO2 uptake during the carbon sink period in 2016. Such studies highlight the critical roles of temperature and precipitation in regulating NEE during growth.

The current investigation by Shenyang Agricultural University builds on these earlier findings, offering important insights into carbon flux dynamics specific to the Liaoning region. By evaluating NEE variations and their environmental responses, this research adds valuable information for predicting carbon flux in orchard ecosystems, especially amid global climate change.

Apple orchards in Liaoning serve as significant carbon sinks throughout the growing season, as confirmed by NEE values indicating notable CO2 absorption. The study emphasizes the influence of environmental factors such as net radiation, atmospheric temperature, saturated vapor pressure deficit, and soil temperature on NEE. This understanding enhances knowledge of carbon dynamics in apple orchards and may help develop effective management strategies to boost their carbon sequestration potential.

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