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With the rapid development of urbanization, large numbers of cone-shaped or tower-shaped isolated peaks and peak forest were surrounded by a human-dominated urban matrix in the process of urban expansion in Karst areas,forming urban remnant hills (URHs), which are important resources of indigenous plant diversity from the urban environment in these areas.Although the studies on urban plant diversity have been extensive, studies on the plant diversity of the remnant habitats, especially those based on URHs,is very weak.In this study, a total of 143 sample plots were set up on 15 hills based on the combination of slope direction and elevation.Alpha diversity was calculated at four levels, i.e.,tree,shrub,herb and whole plant.Four urban matrix characteristic indices,namely,percent total impervious surface area (PTIA),land use,vegetation coverage (VC) and fragmentation indices (FIs),were measured for each hill.Twenty scales, ranging from 100 m to 2000 m and with increasing steps of 100 m,were used as spatial scales.Pearson correlation analysis and linear regression model were used to study the relationship between URHs plant diversity indices and urban matrix indices.The results showed the following:(1)There was a significant positive correlation between the overall plant diversity of URHs of different sizes and PTIA in the surrounding urban matrix within 1600 m.The overall plant diversity of URHs of different scales was significantly correlated with single or multiple Land-use types.There was no significant correlation between VC,FI and URHs overall plant diversity.(2)There was a significant linear relationship between plant diversity at all levels of different scales URHs and the four urban matrix indices.In addition to the small URHs herbaceous diversity,plant diversity at all levels of URHs was jointly affected by double or multiple factors at the 1800 m spatial scale. plant diversity of URHs of different scales in hilly Karst cities are extremely complex under the combined action of multiple factors and multiple scales.

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