Modeling CO2 exchange and meteorological factors of an apple orchard using partial least square regression
2020
Yang, Jianfeng | Duan, Yumin | Yang, Xiaoni | Awasthi, Mukesh Kumar | Li, Huike | Zhang, Linsen
The eddy covariance (EC) technique was used to measure variations of orchard-atmosphere CO₂ exchange, as a function of meteorological variables in an apple orchard in 2016–2017. The annual average CO₂ exchange rate was 2.295 kg m⁻². Excavations and biomass assessments demonstrated that the orchard stored close to 20.6 tC ha⁻¹ as plant C over a 15-year period. Seasonally, high rates of CO₂ uptake and low CO₂ emissions occurred between May and August and December and March, respectively. The maximum rates of monthly CO₂ exchange were 144.44 and 153.61 gC m⁻² month⁻¹ in August 2016 and June 2017, respectively. Partial least squares (PLS) regressions were used to analyze the influence of meteorological factors to on CO₂ exchange rates. Temperature and photosynthetic active radiation (PAR) were observed to exert the largest influence on driving variation in CO₂ exchange. The main meteorological factors affecting CO₂ exchange on daily and monthly time scales were soil temperature (Tₛₒᵢₗ), air temperature (Tₐ), PAR, below canopy CO₂ concentration (BCC), vapor pressure deficit (VPD), and soil water content at 50 cm (SWC₅₀cₘ). The regression model equation describing CO₂ exchange included Tₐ, VPD, precipitation (PPT), and sunshine duration (SD), as significant variables. This model curve fitting explains over 80% of the variation in CO₂ exchange. This study provides CO₂ exchange characteristics and a model equation capable of predicting CO₂ exchange of an apple orchard. Graphical Abstract
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