Seed mass and shape, germination and plant abundance in a desertified grassland in northeastern Inner Mongolia, China

摘要

There is a little information on how seed mass or/and seed shape is associated with germination, meadow-utilizing forms and sand dune types. We collected seeds of 83 plant species (herbs and shrubs) in the desertified grassland of northeastern Inner Mongolia, China, to examine the linkage of seed mass (weight) and shape (variance of three dimensions) to germination. We also selected two types of meadows (for collecting hay and for free grazing) and three sand dune types (i.e. the mobile, the semi-stabilized and the stabilized) to examine whether relevance of seed mass and shape to plant abundance (frequency and density) changes with meadow use and sand dune types. Our results indicate that seed mass or/and shape did not differ significantly between the meadow and the sand dune, between the two types of meadow use, and between the three sand dune types. Germination percentage under standard laboratory conditions was negatively but not significantly related to seed mass, but was positively and significantly related to seed shape (p = 0.001). The relationships between seed shape and plant frequency and density were positive for each meadow use type, but were negative for each sand dune type. The relationship between seed mass and plant frequency was positive for the semi-stabilized and the mobile dunes, but was negative for each of the other meadow-utilizing forms and sand dune types. The relationship between seed mass and plant density was positive for the mobile sand dune, but was negative for each of the other meadow-utilizing forms and sand dune types. Our results suggest that (1) the relationship between seed shape and germination is closer than that between seed mass and germination in the arid temperate desertified grassland, (2) desertification or habitat shift is more likely to result in changes in the seed mass or/and seed shape-plant abundance pattern (for instance, the relationships between seed mass or/and seed shape-plant abundance were positive for meadows, but were negative for sand dunes), rather than changes in the pattern of seed mass or/and seed shape (i.e. seed mass or/and shape did not differ significantly between different meadow and sand dune types); and (3) the seed mass or/and seed shape-plant abundance pattern is related to the degradation intensity of grassland.