关键词: 植被, 土壤团聚体, 对数正态分布, 分形维数, 团聚体稳定性指数

Abstract: This paper studied the seed germination and seedling growth of four perennial drought-tolerant rhizome grasses Leymus chinensis, Agropygron elongatum, Festuca arundinacea and Elymus junceus under effects of 0, 50, 100, 150, 200, 300, 400, and 500 mmol NaCl·L-1. With increasing NaCl concentration, the seed germination rate of test grasses had a decreasing trend. L. chinensis had the lowest salt tolerance. Its seed germination rate was only 15% at 300 mmol NaCl·L-1, and no seeds germinated at >300 mmol NaCl·L-1. A. elongatum, F. arundinacea and E. junceus had higher salt tolerance. Their seed germination rate reached 173%, 20%, and 181%, respectively, at 500 mmol NaCl·L-1. The root length and shoot height of test grasses were significantly negatively correlated with NaCl concentration. With the increase of NaCl concentration, E. junceus had the greatest decrement of its root length while A. elongatum had the smallest one, and L. chinensis had the greatest decrement of its shoot length while A. elongatum had the smallest one. The root/shoot ratio of L. chinensis increased while that of the other three grasses decreased with increasing NaCl concentration, illustrating that for L. chinensis, the inhibitory effect of NaCl was stronger on root growth than on shoot growth, while for the other three grasses, it was in adverse. In sum, L. chinensis had the lowest salt tolerance during its germination and seedling stages, while the other three grasses had higher salt tolerance in their seed germination and seedling growth.

Key words: Vegetation, Soil aggregate, Logarithmic normal distribution, Fractal dimension, Soil aggregate stability index