Abstract
To explore the characteristics of the spatial and temporal variation in soil respiration (SR) in orchard ecosystems in different regions of the Loess Plateau of Shaanxi Province and to distinguish the controlling factors, representative orchards were studied from April to October 2019. We conducted SR measurements in five locations, including Mizhi dangta (MZ), Ansai Liuzhuang (AS), Luochuan houzitou (LC), Fuping meijiaping (FP), and Yangling Wuquan (YL). The results indicated that the SR of each orchard showed clear seasonal variation. The SR increased with the distance from the trunk at the tree scale, while gradually increasing from north to south on the regional scale (p < 0.05). The soil temperature and soil moisture were the main factors controlling the seasonal changes in SR in the orchards. On the tree scale, the fine root biomass was the main factor causing the tree-scale spatial variability. At the regional scale, SR was mainly influenced by the differences in the soil temperature, soil moisture, soil organic carbon, soil bulk density and pH. In agricultural management practices, the cumulative soil respiration was higher with irrigated treatment than with non-irrigated (NI) treatment (p < 0.05). In addition, traditional surface drip irrigation (SDI) and root injection irrigation (RII) showed great differences in soil respiration in the early and late stages of irrigation (p < 0.05), and the soil moisture was the main controlling factor. Compared with no tillage (NI), green cover (GC), deep tillage (DT), and shallow tillage (ST) increased the SR by 57%, 36% and 14%, respectively (p < 0.05). Due to the great temporal and spatial variation in the SR in our study area, we determined that the soil respiration in the orchards was affected not only by environmental factors but also by agricultural measures. Therefore, greater attention should be paid to human factors when exploring SR to ensure that orchard management can promote the economic benefits of the orchards without greatly impacting the environment.
Highlights
Soil respiration (SR) is the main mechanism by which terrestrial ecosystems releaseCO2 to the atmosphere
The regression coefficients in Mizhi dangta (MZ), Ansai Liuzhuang (AS), and Luochuan houzitou (LC) were higher those that in Fuping meijiaping (FP) and Yangling Wuquan (YL), which showed that the relationship between the SR and soil moisture in MZ, AS, and LC was stronger than that relationship in FP and YL (p < 0.05)
The results showed that the soil temperature, soil moisture, soil organic carbon and soil bulk density were positively correlated with the SR, whereas the pH was negatively correlated with the SR on the regional scale (Figure 9)
Summary
Soil respiration (SR) is the main mechanism by which terrestrial ecosystems release. CO2 to the atmosphere. Wang et al [9] studied the temporal and spatial variability in soil respiration at the tree scale This is of great significance for the accurate estimation of carbon emissions. Our study aimed to reveal the soil respiration mechanism of apple orchards in different regions and evaluate the effects of natural and human factors on soil carbon release through high-frequency monitoring of the soil respiration process on the Loess Plateau. Comparative studies of SR can fully reveal the differences in the soil respiration in different regions [37,38,39], and quantifying the temporal and spatial variation in the SR and its controlling factors can provide an SR theoretical basis for the carbon emission estimation of apple orchards ecosystems.
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