Spatial patterns of net greenhouse gas balance and intensity in Chinese orchard system

Fruit production has been expanding due to the pursuit of healthier lifestyles in China. Determining the greenhouse gas (GHG) emissions status of the orchard system could contribute to adopting appropriate measures to alleviate climate change pressure from the growing fruit production. In this study, the net GHG balance and GHG intensity (GHGI) in the Chinese fruit production were estimated at the regional level using a meta-analysis based on databases compiled from relevant publications during 2000-2019, including soil nitrous oxide (N₂O) and methane (CH₄) emissions or uptake, upstream carbon dioxide (CO₂) emissions related to farm practices, and the change of soil organic carbon (SOC) storage from the life cycle perspective. Results showed that the net GHG balance and GHGI varied among six regions, with ranges of 6.4 ± 0.3 to 10.0 ± 0.6 Mg CO₂e ha^-1 yr^-1, and 2.2 ± 0.2 to 3.0 ± 0.2 kg CO₂e kg^-1, respectively. Synthetic nitrogen (N) fertilization was the largest source of overall GHG emissions from fruit production throughout China, accounting for 46% and ranging from 43% to 55% in the six fruit production regions. Fertilizer-induced N₂O emissions were responsible for 22-31% of the total GHG emissions, and the N₂O-N emission factor was identified as 0.7%. Also, power use for irrigation contributed a non-negligible 17% to the emissions on a national level, yet with large regional variations. In addition, fruit production in North, Northeast, Central, and East, and South China have relatively lower GHGIs than in Northwest and Southwest China. The estimated total GHG emissions from the Chinese fruit production were 102 Tg CO₂e, with the contribution of SOC change to a decrease by 11% for the year 2018. Our results highlight an urgency to lower fruit production-related carbon emissions by extending optimized N fertilization and irrigation modes in China's orchard system.