| The exploitation of natural resources has been increasing rapidly along with the development of economy and the modernization. The quarry is necessary to provide stones for the human beings, but it will destroy the landscape and natural ecosystem greatly. So, the restoration and reconstruction of damaged ecosystem caused by the quarry has become a hot topic of restoration ecology.The ecosystem restoration was studied in an abandoned quarry in Xishan Mountain in Beijing (Mentougou District) using ecosystems in different restoration stages to substitute the temporal restoration stages. Based on the pilot study, four typical plots and one comparison plot were selected to represent the different temporal restoration stages. The soil properties, the changes of the vegetation, the soil seed bank and the mechanisms of the community succession were studied to test and enrich the ecological theories and direct the ecological restoration practice.The studies on the soil properties and the vegetation characters in the abandoned quarry in Xishan Mountain found that: The soil particle size, soil bulk density and soil pH decreased along with the natural restoration, while the soil thickness, soil water content and soil nutrients increased along with the natural restoration. The increased soil nutrients include soil organic matter, total N, total P, total K, available N, available P, available K. The physical and chemical characteristics of soil were ameliorated significantly. The Pearson correlation analysis found that the species diversity, species richness and the aboveground biomass were correlated negatively with the soil bulk density and soil pH, while correlated positively with soil water content, percentage of fine sand (2-20μm)(%), percentage of clay (<2μm)(%), soil organic matter, total N, total P, total K, available N, available P, available K. These results showed that the changes of soil properties were corresponding to the changes of community structure. The interaction between the soil and vegetation may promote the community succession together.The dominant species of the communities changed with the ecological restoration. The Eleusine indica, Setaria viridis, Chloris virgata and Setaria viridis, Vitex negundo van heterophytla are the dominant species in the plots after one year, five years, fifteen years and thirty two years of restoration, respectively. Along with the community succession, the structure of the community changed significantly in terms of the composition of species, family and life forms. The number of species showed the trends of increase while the number of families increased gradually, which made the community more complex and diverse along with the succession time. The important value of annuals decreased, while the important value of perennials and shrubs increased gradually along with the restoration time. Only sporadic trees were found in the late of the restoration and their important value are small in the all the plots, which suggested that the natural restoration itself cannot restore forest ecosystems in 32 years and the human activities were needed to promote the restoration towards the forest ecosystems with more ecosystem services.The species diversity and species richness increased with the succession time at first and then tended to stabilize. The vegetation coverage and aboveground biomass increased along with the restoration stages in the study. The correlation analysis showed that the net aboveground primary production was correlated significantly with the Shannon-Wiener diversity index and Margalef richness index (p < 0.01). In the plots after one-year restoration, the net aboveground primary production was correlated negatively with the diversity indices; In the plots after five-year or fifteen-year restoration, the net aboveground primary production was correlated positively with the diversity indices; In the late restoration stages ( >32a ), a unimodal relationship was found between the net aboveground primary production and the diversity indices. The study suggested that the richness of species has the trend to promote the primary productivity of the ecosystem, but the relationship between them is not simple. In the ecological restoration, the restoration is of species richness is needed for the primary productivity, but the functional group and dominant species may play more important role in the function of the ecosystem.The studies on the vegetation in different restoration stages suggested that: (1) The abandoned quarry in Xishan Mountain could be restored by nature forces in the early stages. The restored herbs and shrubs could protect the topsoil and maintain the structure and function of the ecosystems. The important values of trees are small in the all the plots (including the comparison plot after more than 50 years of natural restoration), which suggested that the natural restoration itself cannot restore forest ecosystems in the studied sun-facing slopes and the human activities were needed to promote the restoration. (2) The richness of species is needed in maintain the function of the ecosystem, but the functional group and dominant species may play more important role in the function of the ecosystem. So, the composition of the functional group and the selection and build up of the dominant species may be more important in the ecological restoration.Based on the studies on the soil seed bank in abandoned quarry in the different restoration stages, 35 plants species belonging to 11 families were found in the soil bank. The number of species belonging to Poaceae, Compositae, Verbenaceae and Leguminosae amount to 69.23%-92.86% of all the species across different restoration stages. In the plots after one-year restoration, the annuals amount to the 76.9% of all the species. Along with the restoration time, the number of annual species decreased gradually, while the number of perennial and shrub species increased significantly. No seeds of trees were found in the seed bank of the studied plots in all the restoration stages.The density of soil seed bank varied significantly (from 269 to 5002 grain m-2)between the plots in different restoration stages. The density of soil seed in the plotafter 15-year restoration was the biggest, and then decrease gradually. The number ofseeds in soil bank decreased with the depth of the soil, the pattern is that 0-3cm > 3-6cm> 6-10cm. Along with the restoration stages, the dominance index decreased while the species richness index, evenness index and Shannon-Wiener diversity index increased gradually and come to the highest value in the plots after 32-year restoration. The soil seed bank and vegetation are similar in the study. 73% of the variance of the vegetation can be attributed to the variance of the soil seed bank. The indices of similarity (Ochiai, Dice and Jaccard) between the soil seed bank and vegetation have similar change trend. The three indices of similarity varied from 0.5 to 0.73, from 0.49 to 0.73, from 0.33 to 0.57, respectively. The indices of similarity in the plots after one-year restoration are the smallest and that in the plots after fifteen-year restoration are biggest After 15 years of restoration, the indices of similarity may tend to decrease along with the time. The results showed that the soil seed bank contributed significantly to the vegetation. In the late restoration stages, the composition of community was more influenced by the interactions between the plant species and the influences of seed bank may decrease gradually.The studies on the seed bank of different restoration stages suggested that: (1) There were abundant seeds that could germinate in suitable conditions in the abandoned quarry in Xishan Mountain in Beijing, which can provide seed resources for the elementary restoration. (2) The soil seed bank and vegetation are similar in terms of species composition, density, the indices of the diversity and similarities. The seed bank contributed to the formation of relatively stable communities of herbs and shrubs. So, the natural restoration using the soil seed bank should be considered first in the elementary restoration of abandoned quarry and preserving the topsoil to utilizing the soil seed bank is the economic and effective measure. (3). No seeds of trees were found in the seed bank of the studied plots in all the restoration stages, which suggested that the seed bank cannot restore forest ecosystems in the studied sun-facing slopes and the human activities were needed for the restoration towards the potential forest ecosystems.The studies on the biomass allocation of green foxtail (Setaria viridis (L.) Beauv.) in different restoration stages found that: Along with the restoration stages, the total biomass and the biomass of stems and leaves both increased. The biomass of stems increased the most, which is up to 30%. But, the biomass of roots and reproduction decreased gradually. The biomass of reproduction in the plots after 32 years of restoration decrease 37.6% comparing with that in the plots after 15 years of restoration.Along with the community succession, the green foxtail increased the percentage of biomass to the stems significantly while decreased the allocation to the reproduction and roots. The biomass to the leaves increased only a little. The ratio of belowground biomass to the aboveground biomass and the ratio of root to stem both decreased significantly along with the community succession, while the ratio of stems to leaves increased significantly. The correlation analysis found that the allocation of biomass to stem was negatively correlated with the allocation of biomass to other organs including roots, leaves and reproduction, which suggested the there was a tradeoff between the allocation of biomass to stems and to other organs.The studies on the biomass allocation found that the green foxtail increased the allocation of biomass to the stems while decreased the allocation to the reproduction in the late of the community succession, which is an adaptive response to scrabble for light resources. But this allocation pattern will passively decrease the seed production and may cause the green foxtail fade from the community succession.In conclusion, the study found that there were abundant seeds of herbs and shrubs that could germinate in suitable conditions in the abandoned quarry in Xishan Mountain in Beijing, which can provide seed resources for the elementary restoration. But the human activities were needed for the restoration towards the potential forest ecosystems.
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