关键词: 改良措施, 药用植物, 连作障碍, 土壤养分, 土壤微生物

Abstract: Based on the second national land resource survey database of Tianshui City in 2013, the attribute data such as rural settlements, rivers and roads were extracted. The spatial distribution characteristics of rural settlements at county and city levels were analyzed by using landscape spatial pattern indexes and landscape pattern analysis model. The results showed that an obvious spatial differentiation in landscapes of rural settlements of Tianshui City was found at county level. The rural settlements of Qin’an County were in shape of small patches, but intensively distributed, with villages being relatively close to each other. However, the rural settlements of Qingshui County were totally opposite to those of Qin’an County. The settlement patches of Qingshui, Gangu and Qin’an counties were complex and irregular, and presented a fragmented, random distribution. However, the settlement patches of other counties were simpler, with a lower degree of fragmentation and a regular distribution. In addition, there were obvious spatial features in the size, shape and pattern of distribution of rural settlements at Tianshui City scale. The differences between patch size of township rural settlements and the city’s average patch size were not obvious, so the size of rural settlements had a high level of homoplasy due to similar architectures and terrain characteristics in adjacent regions. Meanwhile, the dense rural settlements were mainly distributed in the north of the city and along the middle Weihe River, while rural settlements in the south and east of the city were sparse, presenting clear directivity of environment. The distribution of patch number and patch density showed an obvious "U" shape in northsouth direction, and a pattern of ‘west high and east low’ in westeast direction. They also showed a decreasing trend from central area to the eastwest sides.

Key words: soil nutrient, soil microbe, medicinal plant, amendment method, consecutive monoculture problem