Effects of elevated air temperature and CO2 concentration on soil CO2 dynamics in an apple orchard

Abstract

In this study, we conducted continuous monitoring of the soil moisture, temperature, and soil CO2 concentration at depths of 15 cm and 40 cm during the non-snowfall period, and the measurement of CO2 efflux from the soil surface in October in experimental greenhouses where apples were cultivated under the condition of elevated air temperature (+3 C) and atmospheric CO2 concentration (+0.02 %). The soil temperature at depth of 15 cm increased by approximately 3 ℃ accompanied by the rising air temperature. The soil CO2 concentration at depth of 15 cm and CO2 efflux from the soil surface was high in the order of (C) “elevated both air temperature and CO2 concentration” > (B) “elevated air temperature” > (A) “control” conditions. The CO2 efflux from the soil surface which was measured near an apple tree was larger than that away from a tree. The difference of the CO2 efflux from the soil surface among the three conditions ((A) ～ (C)) was more conspicuous when that was measured near a tree than away from a tree. In addition to elevated air temperature, high atmospheric CO2 concentration might result in increased biomass and both above- and under-ground dry matter weights of apple trees and undergrowth, thus accelerating the respiration rate or soil CO2 production rate of both plant roots and microorganisms.