Meitan xuebao (Jul 2023)
Soil respiration and its influencing factors in different land use types in desertification mining areas
Abstract
In-depth understanding of the diurnal variation of soil respiration and its influencing factors at different depths under different land use patterns in desertified open-pit mines is crucial to assessing the carbon cycle of ecosystems in ecologically fragile open-pit mines. Taking the Hongshaquan open-pit mine as the research object, the EGM-5 portable infrared gas observation system was used to monitor and obtain the diurnal respiration rate of soil at different depths under different land use types and obtain related influencing factors. Also, the variation law and characteristics, as well as their main influencing factors of soil respiration under different land use types were got. The results showed that: ① There are significant differences in diurnal soil respiration among the five representative types of land features. The daily average soil respiration rates at 10 and 30 cm depths are ordered as artificial forest > Hongshaquan > reclamation area of dump > tamarisk forest > southern line, at 10 cm depth are 5.72, 0.98, 0.34, 0.08 and −0.08 μmol/(m2·s), respectively, and at 30 cm depth are 5.14, 2.18, 0.77, 0.40 and −0.05 μmol/(m2·s), respectively. The southern line is carbon sink, and the other four types of land features are carbon sources. ② The diurnal variation of soil respiration rate is obvious. The diurnal variation of soil respiration in different soil layers and Hongshaquan at 10 cm depth in the reclamation area of the dump site shows a “double peak” trend. The diurnal variation of soil respiration at 10 and 30 cm depths in tamarisk forest shows a “multi-peak” trend. ③ On the diurnal scale, the soil respiration rate at 10 cm depth in the dump reclamation area, the artificial forest and Hongshaquan is significantly positively correlated with soil temperature (P < 0.05) and soil water content (P < 0.01). The diurnal respiration of soil in the forest and the southern line is weak, and the daytime soil temperature in the tamarisk forest and the southern line limits soil respiration, while the nighttime and early morning soil temperature promotes soil respiration. Soil temperature and soil water content can better explain the variation of soil respiration rate of 50.5%−97.3% for the five feature types in the mine area, while only 11.3% for 10 cm in the southern line. ④ There are differences in the relationship between soil respiration and soil carbon content in tamarisk forest and southern line, and the relationship between the soil respiration and soil carbon content of the other three types of land features. The tamarisk forest and southern line soil respiration have a significant negative correlation with inorganic carbon (SIC) (r=0.69, P < 0.01), the soil respiration rate is negative due to inorganic processes, and SIC is the key factor of soil carbon sink. However, the soil respiration in dump reclamation area, artificial forest and Hongshaquan all have a strong negative correlation with dissolved active organic carbon (DOC). The soil respiration in southern line and tamarisk forest also has a strong positive correlation with soil organic carbon (SOC). SOC and DOC are important factors of soil carbon sources. To sum up, the soil respiration rates of different types of land features and different depths in the Hongshaquan mining area are significantly different, and the responses of soil respiration to soil temperature and other environmental factors are different at different depths. It is preliminarily clarified that SIC is an important factor for soil carbon sinks, while SOC and DOC are important factors for soil carbon sources. The results can provide basic data for carbon emissions and carbon cycle in the mining area.
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