分类： 地球科学 >> 地理学 提交时间： 2021-02-10 合作期刊: 《干旱区科学》
摘要： The distribution of binding agents (i.e., soil organic carbon (SOC) and glomalin-related soil protein (GRSP)) in soil aggregates was influenced by many factors, such as plant characteristics and soil properties. However, how these factors affect binding agents and soil aggregate stability along a climatic gradient remained unclear. We selected the Robinia pseudoacacia L. forests from semi-arid to semi-humid of the Loess Plateau, China to analyze the plant biomass, soil physical-chemical properties, SOC and GRSP distribution in different sized soil aggregates. We found that from semi-arid to semi-humid forests: (1) the proportion of macro-aggregates (>0.250 mm) significantly increased (P<0.05), whereas those of micro-aggregates (0.250–0.053 mm) and fine materials (<0.053 mm) decreased and soil aggregate stability was increased; (2) the contents of SOC and GRSP in macro-aggregates and micro-aggregates significantly increased, and those in fine materials decreased; (3) the contribution of SOC to soil aggregate stability was greater than those of total GRSP and easily extractable GRSP; (4) soil properties had greater influence on binding agents than plant biomass; and (5) soil aggregate stability was enhanced by increasing the contents of SOC and GRSP in macro-aggregates and soil property was the important part during this process. Climate change from semi-arid to semi-humid forests is important factor for soil structure formation because of its positive effect on soil aggregates.
分类： 地球科学 >> 地理学 提交时间： 2021-01-15 合作期刊: 《干旱区科学》
摘要： Corn straw return to the field is a vital agronomic practice for increasing soil organic carbon (SOC) and its labile fractions, as well as soil aggregates and organic carbon (OC) associated with water-stable aggregates (WSA). Moreover, the labile SOC fractions play an important role in OC turnover and sequestration. The aims of this study were to determine how different corn straw returning modes affect the contents of labile SOC fractions and OC associated with WSA. Corn straw was returned in the following depths: (1) on undisturbed soil surface (NTS), (2) in the 0–10 cm soil depth (MTS), (3) in the 0–20 cm soil depth (CTS), and (4) no corn straw applied (CK). After five years (2014–2018), soil was sampled in the 0–20 and 20–40 cm depths to measure the water-extractable organic C (WEOC), permanganate oxidizable C (KMnO4-C), light fraction organic C (LFOC), and WSA fractions. The results showed that compared with CK, corn straw amended soils (NTS, MTS and CTS) increased SOC content by 11.55%–16.58%, WEOC by 41.38%–51.42%, KMnO4-C and LFOC by 29.84%–34.09% and 56.68%–65.36% in the 0–40 cm soil depth. The LFOC and KMnO4-C were proved to be the most sensitive fractions to different corn straw returning modes. Compared with CK, soils amended with corn straw increased mean weight diameter by 24.24%–40.48% in the 0–20 cm soil depth. The NTS and MTS preserved more than 60.00% of OC in macro-aggregates compared with CK. No significant difference was found in corn yield across all corn straw returning modes throughout the study period, indicating that adoption of NTS and MTS would increase SOC content and improve soil structure, and would not decline crop production.
分类： 地球科学 >> 地理学 提交时间： 2019-08-30 合作期刊: 《干旱区科学》
摘要： Soil tillage and straw retention in dryland areas may affect the soil aggregates and the distribution of total organic carbon. The aims of this study were to establish how different tillage and straw retention practices affect the soil aggregates and soil organic carbon (SOC) and total nitrogen (TN) contents in the aggregate fractions based on a long-term (approximately 15 years) field experiment in the semi-arid western Loess Plateau, northwestern China. The experiment included four soil treatments, i.e., conventional tillage with straw removed (T), conventional tillage with straw incorporated (TS), no tillage with straw removed (NT) and no tillage with straw retention (NTS), which were arranged in a complete randomized block design. The wet-sieving method was used to separate four size fractions of aggregates, namely, large macroaggregates (LA, >2000 μm), small macroaggregates (SA, 250–2000 μm), microaggregates (MA, 53–250 μm), and silt and clay (SC, <53 μm). Compared to the conventional tillage practices (including T and TS treatments), the percentages of the macroaggregate fractions (LA and SA) under the conservation tillage practices (including NT and NTS treatments) were increased by 41.2%–56.6%, with the NTS treatment having the greatest effect. For soil layers of 0–5, 5–10 and 10–30 cm, values of the mean weight diameter (MWD) under the TS and NTS treatments were 10.68%, 13.83% and 17.65%, respectively. They were 18.45%, 19.15% and 14.12% higher than those under the T treatment, respectively. The maximum contents of the aggregate-associated SOC and TN were detected in the SA fraction, with the greatest effect being observed for the NTS treatment. The SOC and TN contents were significantly higher under the NTS and TS treatments than under the T treatment. Also, the increases in SOC and TN levels were much higher in the straw-retention plots than in the straw-removed plots. The macroaggregates (including LA and SA fractions) were the major pools for SOC and TN, regardless of tillage practices, storing 3.25–6.81 g C/kg soil and 0.34–0.62 g N/kg soil. Based on the above results, we recommend the NTS treatment as the best option to boost soil aggregates and to reinforce carbon and nitrogen sequestration in soils in the semi-arid western Loess Plateau of northwestern China.
分类： 地球科学 >> 地球科学史 提交时间： 2018-09-18 合作期刊: 《干旱区科学》
摘要： Soil acidification is a major global issue of sustainable development for ecosystems. The increasing soil acidity induced by excessive nitrogen (N) fertilization in farmlands has profoundly impacted the soil carbon dynamics. However, the way in which changes in soil pH regulating the soil carbon dynamics in a deep soil profile is still not well elucidated. In this study, through a 12-year field N fertilization experiment with three N fertilizer treatments (0, 120, and 240 kg N/(hm2•a)) in a dryland agroecosystem of China, we explored the soil pH changes over a soil profile up to a depth of 200 cm and determined the responses of soil organic carbon (SOC) and soil inorganic carbon (SIC) to the changed soil pH. Using a generalized additive model, we identified the soil depth intervals with the most powerful statistical relationships between changes in soil pH and soil carbon dynamics. Hierarchical responses of SOC and SIC dynamics to soil acidification were found. The results indicate that the changes in soil pH explained the SOC dynamics well by using a non-linear relationship at the soil depth of 0–80 cm (P=0.006), whereas the changes in soil pH were significantly linearly correlated with SIC dynamics at the 100–180 cm soil depth (P=0.015). After a long-term N fertilization in the experimental field, the soil pH value decreased in all three N fertilizer treatments. Furthermore, the declines in soil pH in the deep soil layer (100–200 cm) were significantly greater (P=0.035) than those in the upper soil layer (0–80 cm). These results indicate that soil acidification in the upper soil layer can transfer excess protons to the deep soil layer, and subsequently, the structural heterogeneous responses of SOC and SIC to soil acidification were identified because of different buffer capacities for the SOC and SIC. To better estimate the effects of soil acidification on soil carbon dynamics, we suggest that future investigations for soil acidification should be extended to a deeper soil depth, e.g., 200 cm.
分类： 地球科学 >> 地球科学史 提交时间： 2017-12-18 合作期刊: 《干旱区科学》
摘要： Labile organic carbon (LC) and recalcitrant organic carbon (RC) are two major fractions of soil organic carbon (SOC) and play a critical role in organic carbon turnover and sequestration. The aims of this study were to evaluate the variations of LC and RC in a semi-arid soil (Inner Mongolia, China) under plastic mulch and drip irrigation after the application of organic materials (OMs), and to explore the effects of OMs from various sources on LC and RC by probing the decomposition characteristics of OMs using in-situ nylon mesh bags burying method. The field experiment included seven treatments, i.e., chicken manure (CM), sheep manure (SM), mushroom residue (MR), maize straw (MS), fodder grass (FG), tree leaves (TL) and no OMs as a control (CK). Soil LC and RC were separated by Huygens D’s method (particle size-density), and the average soil mass recovery rate and carbon recovery rate were above 95%, which indicated this method was suitable for carbon pools size analysis. The LC and RC contents significantly (P<0.01) increased after the application of OMs. Moreover, LC and RC contents were 3.2%–8.6% and 5.0%–9.4% higher in 2016 than in 2015. The applications of CM and SM significantly increased (P<0.01) LC content and LC/SOC ratio, whereas they were the lowest after the application of TL. However, SOC and RC contents were significantly higher (P<0.01) after the applications of TL and MS. The correlation analysis indicated the decomposition rate of OMs was positively related with LC content and LC/SOC ratio. In addition, lignin, polyphenol, WOM (total water-soluble organic matter), WHA (water-soluble humic acid), HSL (humic-like substance) and HAL (humic acid-like) contents in initial OMs played important roles in SOC and RC. In-situ nylon mesh bags burying experiment indicated the decomposition rates of CM, SM and MS were significantly higher than those of MR, FG, and TL. Furthermore, MS could result in more lignin derivatives, WHA, and HAL polymers in shorter time during the decomposition process. In conclusion, the application of MS in the semi-arid soil under a long-term plastic mulch and drip irrigation condition could not only improve soil fertility, but also enhance soil carbon sequestration.
分类： 地球科学 >> 地理学 提交时间： 2017-11-07 合作期刊: 《干旱区科学》
摘要： Soil carbon pools could become a CO2 source or sink, depending on the directions of land use/cover changes. A slight change of soil carbon will inevitably affect the atmospheric CO2 concentration and consequently the climate.
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