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[AGE27-P11] Effects of elevated air temperature and CO2 concentration on soil CO2 dynamics in an apple orchard
Keywords:Soil carbon dioxide, Global warming, Apple orcahrd
As global warming mitigation, carbon capture and storage by soil has been recognized as a function of agricultural field, and capacity of carbon storage in arable land has been discussed. Therefore, it is important to understand the soil CO2 dynamics which results in soil CO2 profile and CO2 efflux from the surface in agricultural lands for maintaining carbon storage by proper agricultural practices. Increase of air temperature and atmospheric CO2 concentration will affect soil environment such as soil moisture, temperature and the distribution of soil organic matter. In apple orchards, not only apple trees but also undergrowth weeds are distributed and thus soil organic matters are often input by cultivation management such as undergrowth mowing and branch pruning, thus changes in soil environment under global warming will be complex. The objective of this study is to evaluate the changes in soil CO2 dynamics under elevated air temperature and CO2 concentration in an apple orchard.
This study was conducted in Fujisaki Farm of Hirosaki University, Fujisaki Town, Aomori, northeast Japan. Three plastic greenhouses of 17m-long, 7m-wide, 5m-high were used for the experiment. In each house 16, 5-year-old apple trees were cultivated. Atmospheric condition of each house was regulated as follows; (A) Control (both sides opened), (B) High temperature (3℃ higher than ambient), (C) High temperature and high CO2 (3℃ and 200 ppm higher than ambient). Irrigation of 4 ~ 7 mm/day was conducted twice a week and additional 50 mm/day irrigation was also conducted once in two months in accordance with average rainfall pattern of the study site. In each greenhouse, soil CO2 concentrations at depths of 15 cm and 40 cm from the soil surface were continuously monitored by using CO2 probes (GMP 252, Vaisala Co., Ltd.), which were connected with datalogger, and the data was collected every 30 minutes from April 2020 to November 2020. Soil gas samples at depths of 15 cm and 40 cm were also obtained with gas samplers (DIK-5212, Daiki Rika Kogyo Co., Ltd.) once or twice a month and CO2 concentrations of the sampled soil gas were analyzed with gas chromatography. Soil moisture and temperature at depths of 15 cm and 40 cm from the soil surface were measured every 30 minutes by using 5TE sensors (METER Co., Ltd). Soil respiration rate, or CO2 efflux from the surface, was measured with automated open/closed chamber system on Oct. 2020.
Under all three conditions, soil CO2 concentrations at depth of 15 cm was lower than that at depth of 40 cm since the gas at the shallower layer were easily diffused to the soil surface. Monitored soil CO2 concentrations increased from April to August accompanied with rise of soil temperature and then gradually decreased from autumn to winter.
Soil temperature of (B) “High temperature” and (C) “High temperature and CO2” were two to three ℃ higher than that of (A) “Control” during the whole experiment period. The soil CO2 concentration at depth of 15 cm of (C) was the highest and that of (A) was the lowest among three conditions. Soil respiration rate was also the highest at (C) and the lowest at (A) ((A) 520.5, (B) 606.2 and (C) 643.3 mg CO2 m-2 hour-1). The difference of soil respiration rate among three condition at a distance of 50 cm from a tree ( (A) 650.5, (B) 889.2 and (C) 979.3 mg CO2 m-2 hour-1) was more conspicuous than that away from the trees at a distance of 150 cm from a tree ( (A) 307.3, (B) 323.1 and (C) 347.2 mg CO2 m-2 hour-1). Under high temperature and CO2 condition, increase of dry matter production of both undergrowth and apple trees was confirmed in 2019. Therefore, increase of soil temperature as well as increase of soil carbon input such as mown grass might affect the soil CO2 production rate by plant roots and microorganisms.
Acknowledgement: This work was supported by JSPS KAKENHI Grant Numbers JP18H03964 and JP19K15934.
This study was conducted in Fujisaki Farm of Hirosaki University, Fujisaki Town, Aomori, northeast Japan. Three plastic greenhouses of 17m-long, 7m-wide, 5m-high were used for the experiment. In each house 16, 5-year-old apple trees were cultivated. Atmospheric condition of each house was regulated as follows; (A) Control (both sides opened), (B) High temperature (3℃ higher than ambient), (C) High temperature and high CO2 (3℃ and 200 ppm higher than ambient). Irrigation of 4 ~ 7 mm/day was conducted twice a week and additional 50 mm/day irrigation was also conducted once in two months in accordance with average rainfall pattern of the study site. In each greenhouse, soil CO2 concentrations at depths of 15 cm and 40 cm from the soil surface were continuously monitored by using CO2 probes (GMP 252, Vaisala Co., Ltd.), which were connected with datalogger, and the data was collected every 30 minutes from April 2020 to November 2020. Soil gas samples at depths of 15 cm and 40 cm were also obtained with gas samplers (DIK-5212, Daiki Rika Kogyo Co., Ltd.) once or twice a month and CO2 concentrations of the sampled soil gas were analyzed with gas chromatography. Soil moisture and temperature at depths of 15 cm and 40 cm from the soil surface were measured every 30 minutes by using 5TE sensors (METER Co., Ltd). Soil respiration rate, or CO2 efflux from the surface, was measured with automated open/closed chamber system on Oct. 2020.
Under all three conditions, soil CO2 concentrations at depth of 15 cm was lower than that at depth of 40 cm since the gas at the shallower layer were easily diffused to the soil surface. Monitored soil CO2 concentrations increased from April to August accompanied with rise of soil temperature and then gradually decreased from autumn to winter.
Soil temperature of (B) “High temperature” and (C) “High temperature and CO2” were two to three ℃ higher than that of (A) “Control” during the whole experiment period. The soil CO2 concentration at depth of 15 cm of (C) was the highest and that of (A) was the lowest among three conditions. Soil respiration rate was also the highest at (C) and the lowest at (A) ((A) 520.5, (B) 606.2 and (C) 643.3 mg CO2 m-2 hour-1). The difference of soil respiration rate among three condition at a distance of 50 cm from a tree ( (A) 650.5, (B) 889.2 and (C) 979.3 mg CO2 m-2 hour-1) was more conspicuous than that away from the trees at a distance of 150 cm from a tree ( (A) 307.3, (B) 323.1 and (C) 347.2 mg CO2 m-2 hour-1). Under high temperature and CO2 condition, increase of dry matter production of both undergrowth and apple trees was confirmed in 2019. Therefore, increase of soil temperature as well as increase of soil carbon input such as mown grass might affect the soil CO2 production rate by plant roots and microorganisms.
Acknowledgement: This work was supported by JSPS KAKENHI Grant Numbers JP18H03964 and JP19K15934.