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【Background and objective】 Saline-alkali soils are widely distributed in Ningxia. Because of the scarcity of precipitation, such soils are often reclaimed by flooding rice field combined with subsurface drain. This paper presents the results of an experimental study of water and salt movement in a paddy field as affected by the sand filter in the subsurface drain. 【Method】 The field experiment was designed based on our current understanding and previous experimental results of the subsurface drains in different regions across the province. The experiment compared three filters: fine sand, mixture of fine sand and fine gravel sand at 1∶2 ratio and fine gravel. In each treatment, we measured spatiotemporal dynamics of soil water and soil salt. 【Result】 The filter with mixture of fine sand and fine gravel at 1∶2 ratio effectively reduced water content in the top 0~60 cm soil, increasing soil desalination during irrigation period as a result. Decrease in water content in the top 0~60 cm soil reduced evaporation, thereby alleviating salt accumulation in the root zone and reliveing salt stress to the crop. 【Conclusion】 The most effective filter for the subsurface drain in the studied paddy field is a mixture of fine sand and fine gavel at 1∶2 ratio.

Understanding the influence of afforestation on soil microorganisms, the major drivers of soil processes, is essential for maintaining soil health and sustainability. However, in a desert‐oasis ecotone, variations in the microbial community along shrub afforestation years remain unclear. We conducted a metagenomic analysis to study the temporal changes in microbial community structure in 0–100 cm soil following 3‐, 7‐, and 10‐year afforestation of Tamarix ramosissima Ledeb. on the southern edge of the Taklimakan Desert. Compared to the unreclaimed desert land, in 3‐year or 7‐year stands, soil organic carbon (SOC), nitrate nitrogen, available phosphorus and potassium (AK) contents significantly increased on average by 60%, 852%, 72%, and 299%, respectively. Soil archaeal and bacterial community composition were significantly affected by afforestation; their α‐diversity increased on average by 5.9% and 11.1%, respectively, after afforestation, showing a unimodal pattern along afforestation years. In contrast, fungal α‐diversity and community composition did not show significant variation over the afforestation period. The influence of AK outweighed that of SOC and other nutrients on soil microbial community composition. These findings suggest that T. ramosissima afforestation in the desert‐oasis ecotone has significant impacts on the community composition and α‐diversity of archaea and bacteria, but not fungi, by modifying soil physicochemical properties. This research provides valuable implications for soil management and microbial processes related to the afforestation of salt‐secreting shrubs. [ABSTRACT FROM AUTHOR]

In order to realize the power line extraction of long distance linear airborne light detection and ranging (LiDAR), a power line extraction method of long-distance airborne LiDAR based on cloth simulation was proposed. On the basis of data preprocessing, the function between cloth and corresponding airborne LiDAR point cloud was analyzed by simulating the falling process of cloth. The position where cloth stayed after gravity faUing was determined as the power line point cloud with similar height, and then the straight line was fitted in the xOy plane. The distances from points to the fitting line were used to judge the number of power lines whether odd or even. And the power line point clouds were divided by the judgment of points on both sides of the line to achieve the extraction of a single power line. The experimental results show that the accuracy of the proposed method is 98.9%, with high degree of automation and not sensitive to the lack of local point cloud, which has good engineering application value for intelligent poweriine inspection and automatic analysis of transmission channel spatial structure. [ABSTRACT FROM AUTHOR]