Components of Soil Respiration and Its Temperature Sensitivity in Four Reconstructed Soils

seasonal changes characteristics in the respiration of four reconstructed soils Abstract: seasonal changes characteristics in the respiration of four reconstructed soil masses 9 in a barren gravel land were monitored using soil carbon flux measurement system. The 10 results showed that (1) The seasonal changes in soil respiration and heterotrophic respiration 11 of four reconstructed soils of meteorite, shale, sand and soft rock were the same as the 12 seasonal change in soil temperature. Soil respiration and heterotrophic respiration increased 13 with soil temperature. It was gradually increasing, reaching the maximum in summer and 14 decreasing to the minimum in winter. Among the four reconstructed soils, the average annual 15 soil respiration of reconstructed soil with sand was 4.87 μmol•m –2 •s –1 , which was 16 significantly higher than the other reconstructed soils (p<0.05).(2) The autotrophic respiration 17 of four reconstructed soils showed obvious seasonal dynamic changes. The maximum and 18 minimum values appeared in August 2018 and January 2018, respectively. In the whole year, 19 The variation range of the annual average soil autotrophic respiration in the total respiration 20 of the reconstituted soil with addtion of meteorite, shale, sand and soft rock were 12.5-38.0%, 21 9.5-42.0%, 7.7-41.2%, and 5.0-39.3%, respectively.(3) Soil temperature was the main factor 22 affecting soil respiration. The four reconstructed respiration had a very significant correlation 23 with soil temperature (p<0.01). The relationship between reconstructed soils respiration and 24 soil temperature can be indexed function characterization. The 90% to 93% changes in soil 25 respiration of reconstructed soils were caused by soil temperature. The order of Q 10 in soils 26 respiration of four reconstructed was as follows: Sand> shale> soft rock > meteorite.

Numerically Simulated Water Movement in Reclaimed Multi-Layered Soil Backfilled with Yellow River Sediments

The Yellow River interlayer filling reclamation technology can effectively improve the quality of destroyed cultivated land in the condition of limited soil resources. However, it is a conundrum to choose the appropriate sandwich strategy according to the amount of soil that can be backfilled. This study using the Hydrus-1D model to simulate water movement in reclaimed multiple-layered soils were to understand the mechanism of interlayer, and predict the optimal profile for reclaimed with Yellow River sediments. Simulations were performed on 18 soil profiles that were divided into a control check (CK) and two general scenarios that the total thickness of soil were 50 and 60 cm. Treatments in both scenarios exhibited interaction of different positions and thicknesses of soil interlayer. Results showed that removing part of the subsoil overlying the sediment placed it between sediment layers will improve the infiltration character of the conventional reconstructed soil profiles (T50-0 and T60-0). Moreover, changing the thickness of the interlayers affected infiltration character and soil water-holding capacity more than changes in the position of the layers for same total thickness of native soil. The optimal reconstructed soil profiles for scenarios 1 and 2 were T50-6 (interlayer thickness of 20 cm and located at a position of 30 cm) and T60-9 (interlayer thickness of 30 cm and located at a position of 30 cm), which could have a better infiltration character that were more closed to the native farmland.

Soil Water Movement of Mining Waste Rock and the Effect on Plant Growth in Arid, Cold Regions of Xinjiang, China

Understanding the water movement in reconstructed soil and its efficacy on local vegetation is critical for the ecological reclamation of mine lands. This study employed field experiments and a numerical model to investigate the water movement in reconstructed soil and evaluate the effects of mining waste rock on plant growth in an arid and cold region of Xinjiang. Water contents and matrix potentials were monitored over 1-year period. A numerical model was established based on the observed data to calculate soil water balance and irrigation demand. The results show that the soil water content at a shallow depth could be more vulnerable to the climate variability in uncompacted and compacted soil. The water content at the depth of 50 cm with 30 cm-thick covering soil was the lowest; meanwhile, the barrels with 50 cm- and 70 cm-thick covering soil without compaction had the highest water content. Moreover, the water content of the uncompacted soil could be lower than that of the counterpart attributed to the variation in soil porosity. To maintain the water content as an optimized value to grow a certain plant species in the long run, irrigation could be implemented according to the water balance over time in mine lands.

Optimum of interlayers in reconstructed soil with Yellow River sediment for restoring subsided coal mined land to farmland

Underground coal mining causes land subsidence, a large area of cultivated land is destroyed. The Yellow River interlayer filling reclamation technology is the powerful way to restore cultivated land. Understanding the mechanism of action of interlayers in reconstructed soil filled with Yellow River sediments is essential to achieving sustainable land management in the Yellow River regions. Column experiments and Field experiments were conducted to optimum of interlayers in reconstructed soil with Yellow River sediment for restoring subsided coal mined land. Our findings show that the inclusion of interlayers in the sediment reduced water leakage and moisture evaporation, and improved the water-holding capacity of the material in comparison to conventional reconstructed soil profile (Ck2). When the 30 cm thickness of interlayer, putting 2 interlayers in sediment (T6) was the optimal profile with the highest water-holding capacity. In comparison to CK2, the migration rate of wet front decreases by 32.16%, the cumulative evaporation decreases by 16.29%, the volumetric water content of filling layer (θ_fl) increases by 121.56%, and the water-holding coefficient (CWR) increases by 59.47%. It is also proved by field experiments. The wheat and maize yields of T6 improved 51.84% and 54.80%, respectively, as compared with CK2, that closer to undisturbed farmland (CK1). This study provides a valuable framework for subsided land reclamation regarding the method of placing interlayers into Yellow River sediment for enhancing water retention and productivity.

Water Distribution in Reconstructed Soil of Nonmetal Mines and the Ecological Effect in Xinjiang, China

Because of the arid climate and fragile ecological environment in Xinjiang, China, land reclamation should be carried out after mining. The core of land reclamation is the water content of the surface covering soil. In this paper, the law of water distribution in reclamation reconstructed soil of nonmetal mines in Xinjiang was studied. In order to obtain the law of water distribution in reconstructed soil, we set up an observation system of the neutron probe and tensiometer. The neutron probe was used to monitor the soil water content. The tensiometers were used to obtain the matrix potential of soil for verifying the water distribution in reconstructed soil. Volumetric water content and matrix potential of reconstructed soil during 1-year period of management and irrigation were obtained by long-term monitoring. After one year’s field in situ test, 2424 sets of neutron probe data and 1368 sets of tensiometer data were obtained. By studying the above parameters, we summarized the law of water distribution in reconstructed soil of variable thickness and degree of compaction with nonmetallic waste rock filling. The results showed that covering soil was helpful to retain water content. Whether the soil was compacted or uncompacted, the soil water content at the depth of 10 cm was less than that at other depth of reconstructed soil because it was greatly affected by meteorological factors. The water content of reconstructed soil at 30 cm depth was greater than that at other depths. Under the influence of factors such as the thickness and compaction of the soil, the response time of soil water content and matrix potential to each irrigation infiltration was different. According to the characteristics of reclamation-vegetation such as alfalfa growth in Xinjiang, the thickness of surface reconstructed soil should be not less than 50 cm. Over time, soil that was compacted once was better for the vegetation. The research results could provide a reference for the land reclamation of nonmetallic mines in Xinjiang, China.