Background The soil in the lithoid hilly area of North China is poor and the soil erosion is serious, which severely restricts the productivity of these undeveloped mountains. Vegetation restoration is an important measure in recovering ecological environment. A large number of studies have shown that when plants are subjected to drought stress, a series of physiological changes will be produced in plants to adapt to drought stress, but the response characteristics, adaptability and physiological mechanisms of different plants to drought stress vary. Therefore, studying the response characteristics and physiological mechanisms of different tree species under drought stress has important practical significance for its application in barren hills greening and vegetation restoration.

Methods Using the test method of potted water control, 10 2-year old plants and consistent Fraxinus chinensis, Quercus acutissima and Gleditsia sinensis seedlings were selected as test materials, and their photosynthesis parameters, MDA content, cell membrane permeability, relative water content, leaf chlorophyll content, SOD activity, and proline content in response to drought stress under continuous drought conditions were determined. The relationship between each physiological index and drought resistance was compared by grey relational analysis, the drought resistance of three tree species was comprehensively evaluated by membership function method.

Results 1) With the drought increasing, the MDA content, membrane permeability and SOD activity of three tree species increased, while the relative water content and net photosynthetic rate of leaves decreased, and the chlorophyll content of Q. acutissima increased. 2) The proline content of the G. sinensis was greatly increased, and the proline content of the F. chinensis and Q. acutissima remained substantially unchanged. The drought resistance of three tree species under moderate or severe drought stress was ranked by membership function method, the results showed as G. sinensis > Q. acutissima > F. chinensis. 3) Grey correlation analysis showed that the correlation between the indexes of moderate drought conditions and drought resistance was as follows:leaf relative water content (0.784) > SOD activity (0.723) > chlorophyll content (0.652) > cell membrane permeability (0.527) > MDA content (0.526) > net photosynthetic Rate (0.506) > proline content (0.503). The correlation between various indicators and drought resistance in severe drought conditions was as:leaf relative water content (0.749) > cell membrane permeability(0.632) > net photosynthetic rate(0.563) > SOD activity (0.543) > MDA content (0.528) > chlorophyll content (0.508) > proline content (0.506).

Conclusions The three tree species have certain commonality in the means of resisting drought, that is, to prevent drought stress by maintaining the leaf water and SOD to eliminate free radicals and reducing the degree of lipid membrane peroxidation. This research can distinguish the differences between different physiological indicators in the drought stress of plants and screen the drought-resistant tree species to provide reference for the selection and ecological restoration of afforestation species in the lithoid hilly area of North China.