International audienceBackground and aims - Livestock grazing exclusion was widely used to manage degraded grassland ecosystems, but little is known on the effects of long-term grazing exclusion on aboveground and belowground species diversity of the steppe vegetation in China. Material and methods - The species composition of the aboveground vegetation and the soil seed bank were examined on sites after a 25-year grazing exclusion in a typical steppe on the Loess Plateau, NW China. Key results - Results showed that long-term grazing exclusion significantly improved vegetation cover, biomass and aboveground species evenness. Long-term grazing exclusion significantly increased species richness and seed density in the soil seed bank, but significantly decreased belowground species evenness. The seeds were mainly present in the litter and the topsoil (0-5 cm), accounting for about 76% of the total seed number. Exclusion of grazing significantly decreased seed depletion in soil seed bank from April to July as compared to grazed sites. The Sørensen similarity index between aboveground and belowground species composition was low in the typical steppe, and long-term grazing exclusion did not significantly improve this similarity. Conclusion - Our results suggest that long-term grazing exclusion can significantly improve both aboveground and belowground species diversity in the steppe vegetation of the Loess Plateau, but has little or no effect on the similarity in composition between the two compartments

The paper presents a study by taking the soil seed banks and vegetation successions of the forests in Ziwuling Mountain as indicators to analyze the effects of the ages, and the litter layers and soil depths at growing locations in seven types of forest communities on their seed bank formations and soil quality. The results showed that the seed banks at different growing locations in the communities increased in the order of upper slope, middle slope, and lower slope; the seed storages of the seed banks in the different layers of the communities varied, much more higher in the litter layers than in 0-15 cm, and the seed storages of the seed banks in the seven types of forest communities ranked in the increasing order of Pinus tabulaeformis forest, Pinus shenkaneusis forest, Quercus liaotungensis forest, Populus davidiana forest, Betula platyphylla forest, scrub communities, and grassland communities; in the meantime, the seed storage of seed banks peaked in 30-50 years old P. shenkaneusis forest, 30-40 years old P. tabulaeformis forest, 15-30 years old Q. liaotungensis, and P. davidiana and B. platyphylla forests, and 10-15 years old scrub and grassland communities, and the ages of the communities varied with the seed storages of the seed banks in a significantly correlative manner following a fitted exponential equation. In addition, the soil seed banks of the seven types of communities consisted of rich and diverse species with the herbaceous and shrub species greatly outnumbering the arbor species; in general, the coniferous forests were composed of 31 kinds of plants, the deciduous and broadleaf forests consisted of 20-29 plant species, the shrubs contained 27 plant species, and the herbaceous plants numbered 20 plant species; The various species compositions contained only 4-6 arbor species with most being foreign species. In each of the compositions, Bothriochloa ischemum was the grassland plant with the highest occurrence frequency, Sophora viciifolia and Hippophae reamnoides were the shrub plants with the highest occurrence frequencies, and Q. liaotungensis was the arbor plant with the highest occurrence frequency, and they followed by P. shenkaneusis and P. tabulaeformis. These results showed that soil seed banks and forest successions are better indicators for soil quality from natural successions.

Whether and how seed mass and shape are related to seed persistence in soil is a controversial topic in plant ecology. There is little information on this relationship in sandy habitats. We tested whether or not this pattern is retained among 141 species within a range of growth forms, from a wide range of families, in the Horqin sandy land of northern China, which belongs to the inland sand ecosystem. We collected information on seed mass, shape and persistence of these species in this region from published articles. Seed mass and shape were found to be significantly and negatively correlated to persistence in the soil in the Chinese flora, in the same way as in most other floras examined, but not in the same way as the Israeli coastal sand dune flora. The value of seed mass and shape as good predictors of persistence in the soil could be applied to the Horqin sandy land. Although many factors affect the relationship between seed mass, shape and persistence, ease of burial appears to be the main potential interpretation in the Horqin sandy land.

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