关键词: 柠条, 沙化草地, 土壤颗粒组分, 富集率, 荒漠草原

Abstract: Introduction of artificial shrubs in arid area is a common ecological restoration measure. Artificial shrubs can stabilize soil surface environment and promote restoration of desertified land through its function of warding off wind and fixing sand. Caragana intermedia is a typical xeric shrub for sand control in desertified land. However, the effect of C. intermedia on desertified grassland after years of introduction is still lacking in terms of regional summary and analysis. By adopting methods of classical statistics and geostatistics, we divided the typical desert steppe located in central Ningxia into 37 spatial grids, sizing 20 km×20 km each and selecting 4 sample plots in each grid, which totals up to 148 sample plots, in accordance with different varieties of vegetation (C. intermedia and desertified grassland) and slope direction (northern and southern slope). With these data, we compared the desertified grassland and grassland with C. intermedia (artificial C. intermedia plantations) in terms of soil particle composition. We then analyzed the effect on soil particle composition and clay enrichment capacity both in desertified grassland and artificial C. intermedia plantations in designated area, with the aim of providing decisionmaking reference for restoration of desertified land of similar type. Preliminary research result shows that there is no significant difference in soil particle composition between artificial C. intermedia plantations and desertified grassland. On the shrub scale, the enrichment capacity of clay is relatively higher at the northern slope of artificial C. intermedia plantations, with a rate of 0.11 on average and maximum rate of 1.09 and with northern slope in the north part of the study area; whereas, the rate in the south part gradually descends and, by contrast, its enrichment capacity at southern slope is mostly in the negative, with an average of -0.08. Compared with shrub scale, enrichment capacity of clay is significantly lower on the patch scale; ratio at the northern slope is still in positive, but decreases sharply, while that of the southern slope is in the negative with an enhancing tendency and an average of -0.17. In conclusion, the introduction of C. intermedia is an important engineering measure for restoring desertified grassland in desert steppe and its effect not only relates to desertified degree of the soil, but also relates to micro-habitat (slope direction). So, far, as the area under study is concerned, C. intermedia’s effect after its introduction, instead of significantly enhancing the area’s clay content, it spatially promoted clay redistribution. To a certain extent, it demonstrated a negative effect as a result of the shrub encroachment; and such negative effect would be strengthened with increases in desertified degree of the soil in desert steppe.

Key words: Caragana intermedia, desertified grassland, soil particles, enrichment ratio, desert steppe