[Water holding characteristics of litters of typical forest in loess area of Western Shanxi Province, China]. / æ™‹è¥¿é»„åœŸåŒºå ¸åž‹æž—åˆ†æž¯è½ç‰©æŒæ°´ç‰¹æ€§.

It is of great significance to investigate the volume and water holding characteristics of litters for the accurate evaluation of forest water conservation function. With Pinus tabuliformis, Robinia pseudoacacia, Populus davidiana, Quercus wutaishanica and Platycladus orientalis as the research objects in the Loess Plateau of Western Shanxi Province, we analyzed the thickness of undecomposed layer and semi-decomposed layer, the volume of litter, and the relationship between the litter water-holding characteristics and the immersion time for different stands by the combination of sample survey and indoor immersion test. The results showed that the total thickness of litter layer was 4.06-5.12 cm, with the thickest layer in R. pseudoacacia forest and the thinnest in P. tabuliformis forest. The storage volume of litter was the largest in Q. wutaishanica (24.39 t·hm-2), followed by P. davidiana (23.64 t·hm-2), P. orientalis (22.51 t·hm-2), and R. pseudoacacia (22.48 t·hm-2), and the smallest in P. tabuliformis (20.42 t·hm-2). The volume in the undecomposed layer was less than that in the semi-decomposed layer. The maximum water holding of litter was 40.41-79.56 t·hm-2, with the highest of Q. wutaishanica and the lowest of P. tabuliformis. The effective interception rate of litter was 108%-188%. The changes of water capacity and water absorption rate of litter were most rapid in Q. wutaishanica, P. davidiana and R. pseudoacacia, and the changes were faster in the semi-decomposed layer than in the undecomposed layer. The water-holding capacity of litter in five forests was following an order of Q. wutaishanica>P. davidiana>R. pseudoacacia>P. orientalis>P. tabuliformis.

Succession law and model of reconstructed soil quality in an open-pit coal mine dump of the loess area, China.

Studying the change laws of reconstructed soil quality and constructing succession models are the main components and tools of reconstructed soil quality evaluation for the supervision and management of reconstructed soil. However, the evaluation and management system of reconstructed soil quality suitable for the loess area needs to be improved. This paper aimed to clarify the succession law of reconstructed soil in an open-pit coal dump in the loess area on the temporal scale and to construct a succession model of reconstructed soil quality to evaluate and manage reconstructed soil. The Pingshuo coal mine, a representative open-pit coal mine in the loess area, is the study area. Field investigation and sampling, time-space substitution, and the combination of qualitative and quantitative research methods were used. The reconstructed soil quality succession model was constructed based on the soil quality index method. Results: (1) As the reclamation period increased, the physical and chemical properties of reconstructed soil significantly improved, and reconstructed soil quality generally reached the quality of the original landform after approximately 15 years of reclamation. However, after long-term reclamation, soil physical properties still limited the improvement of reconstructed soil quality to a certain extent. (2) After long-term reclamation, the difference in reconstructed soil quality between layers gradually decreased, and the reconstructed soil condition of the 0-10 cm soil layer was obviously better than that of the other layers. (3) We quantitatively constructed and verified the reconstructed soil quality succession model that is suitable for the loess area, which can be used in conjunction with adaptive management for the evaluation and management of reconstructed soil in the loess area. In conclusion, this study is of great significance to meet the real needs of dynamic evaluation and management of reconstructed soil quality in the loess area and to enrich the soil evaluation and management system at home and abroad.

Effect of rainfall gradient and vegetation restoration on gully initiation under a large-scale extreme rainfall event on the hilly Loess Plateau: A case study from the Wuding River basin, China.

As the most serious form of soil erosion, gully erosion can be triggered by individual high-intensity rainfall events. In this study, a total of 369 small catchments in 24 sites were sampled to investigate the relationship between rainfall and gully erosion on hillslopes and to study the impacts of vegetation restoration following heavy rainstorms in the central Loess Plateau, China. A total of 280 newly formed gullies on hillslopes were identified by comparing pre-storm Google Earth images and post-storm unmanned aerial vehicle (UAV) images. The results showed that the dimensions and density of gullies increased significantly with rainfall gradient increasing from the periphery to the storm center. When the rainfall amount exceeded 200 mm, gully volumetric density reached up to 928.39 m3/km2 and the mean gully volume was 15.74 m3, 12.8 times and 2.3 times the mean gully volume for rainfall amounts of 106 and 150 mm, respectively. In the sampled small catchments, where cropland was dominant, the relationships between the gully densities and rainfall amount could be fitted with exponential functions. Vegetation restoration was found to reduce the densities and dimensions of gullies on hillslopes. Compared to those in cropland-dominated catchments, the density of gullies in grassland-dominated catchments was found to be lower by > 60%, while the individual gully volume was found to be 1.6 times higher. In small catchments, no new hillslope gullies were observed when the rainfall amount fell below 106.7 mm. Therefore, the rainfall thresholds for (1) ephemeral-gully initiation on grassland hillslopes, (2) permanent-gully initiation on grassland hillslopes, and (3) permanent-gully initiation on cropland hillslopes are concluded to be not >106.7 mm, not >136.1 mm, and not >110.2 mm, respectively. This suggests that the restoration of cropland to grassland would reduce the rainfall threshold for gully initiation.

[Oxygen and hydrogen stable isotope compositions of soil water in deep loess profile under different land use types of northern Shaanxi, China]. / é™•åŒ—é»„åœŸåŒºæ·±å‰–é¢ä¸åŒåœŸåœ°åˆ©ç”¨æ–¹å¼ä¸‹åœŸå£¤æ°´æ°¢æ°§ç¨³å®šåŒä½ç´ ç‰¹å¾.

Investigation of stable isotope composition under different land use types is helpful for understanding soil water movement and hydrological effects of land use change. We collected soil samples in profiles ＞ 15 m deep under four land use types (i.e. farmland, grassland, Salix cheilophila and Populus sp.) in the loess deposits of northern Shaanxi. We measured hydrogen and oxygen stable isotope composition of soil water to explore the mechanism of soil water movement and the impacts of land use types. The isotope compositions of soil water under four land use types were significantly different. The δD values of soil water under farmland, grassland, S. cheilophila and Populus sp. were -81.1‰--60.1‰, -91.2‰--61.0‰, -87.4‰--63.6‰ and -73.5‰--62.2‰, while the δ18O values were -11.2‰--7.6‰, -12.6‰--8.2‰, -11.5‰--8.1‰ and -9.9‰--7.7‰, respectively. The soil water stable isotopes fluctuated across the profiles. The soil water isotope compositions in the layers of 0-3 m changed sharply, with the δD values being -80.2‰--61.8‰, -75.9‰--65.5‰, -76.0‰--63.6‰ and -73.5‰--62.2‰, respectively. In the layers of 3-12 m, the isotope profiles of farmland and grassland were parabolic, whereas those of S. cheilophila and Populus sp. were relatively stable. Soil water isotope compositions in the layers deeper than 12 m were generally stable with the δD values of -80.8‰--71.5‰, -83.0‰--67.5‰, -87.4‰--76.0‰ and -67.5‰--64.3‰, respectively. Across the four land use types, soil water stable isotope compositions were not significantly different either in the shallow layers or in the deep soil layers, but their differences in the layers of 3-12 m were significant. Soil moisture was mainly recharged from precipitation with piston flow as the main form of soil water movement. Soil water under four land use types might be recharged by wet events of different intensities. Soil water under farmland and grassland could be recharged by wet events of small intensity, but that under S. cheilophila and Populus sp. may be mainly recharged by the rainstorm in summer and autumn.

Hybrid Integration Approach of Entropy with Logistic Regression and Support Vector Machine for Landslide Susceptibility Modeling.

The main purpose of the present study is to apply three classification models, namely, the index of entropy (IOE) model, the logistic regression (LR) model, and the support vector machine (SVM) model by radial basis function (RBF), to produce landslide susceptibility maps for the Fugu County of Shaanxi Province, China. Firstly, landslide locations were extracted from field investigation and aerial photographs, and a total of 194 landslide polygons were transformed into points to produce a landslide inventory map. Secondly, the landslide points were randomly split into two groups (70/30) for training and validation purposes, respectively. Then, 10 landslide explanatory variables, such as slope aspect, slope angle, altitude, lithology, mean annual precipitation, distance to roads, distance to rivers, distance to faults, land use, and normalized difference vegetation index (NDVI), were selected and the potential multicollinearity problems between these factors were detected by the Pearson Correlation Coefficient (PCC), the variance inflation factor (VIF), and tolerance (TOL). Subsequently, the landslide susceptibility maps for the study region were obtained using the IOE model, the LR-IOE, and the SVM-IOE model. Finally, the performance of these three models was verified and compared using the receiver operating characteristics (ROC) curve. The success rate results showed that the LR-IOE model has the highest accuracy (90.11%), followed by the IOE model (87.43%) and the SVM-IOE model (86.53%). Similarly, the AUC values also showed that the prediction accuracy expresses a similar result, with the LR-IOE model having the highest accuracy (81.84%), followed by the IOE model (76.86%) and the SVM-IOE model (76.61%). Thus, the landslide susceptibility map (LSM) for the study region can provide an effective reference for the Fugu County government to properly address land planning and mitigate landslide risk.