Soil seed banks can provide a mechanistic for understanding the recruitment dynamics and can inform conservation management of ecosystems. To investigate the contribution of soil seed banks to vegetation restoration i...Soil seed banks can provide a mechanistic for understanding the recruitment dynamics and can inform conservation management of ecosystems. To investigate the contribution of soil seed banks to vegetation restoration in moving sand dune systems, we compared seed structure and species similarity between soil seed banks and standing vegetation among moving sand dunes, ecotones and dune slacks in northeast China. Average seed density in dune slacks was greater than in ecotones or moving sand dunes. Seed density in the soil layer of 0-10 cm was greater than at 10-20 cm both in the moving sand dunes and the eco- tones, but seed densities were similar at depths of 10-20 and 20-30 cm in moving sand dunes. Moreover, the spatial autocorrelation of seed density on moving sand dunes was weak but was strong on the ecotones and dune slacks. The species in the soil seed bank of moving sand dune systems were nearly all annuals, and the low similarity was mainly due to the lack of perennial species that were common in standing vegetation. Consequently, vegetation restoration cannot mainly rely on the soil seed banks in the movingsand dunes and more attention should be paid to protection of the dune slacks because they are the main source of seed disperse and seedling recruitment in moving sand dune systems.展开更多
Species composition,structure,and regeneration status of trees were assessed in five dry Afromontane forests.In each of the forests,trees having≥5 cm diameter at breast height were identified and measured in 80 quadr...Species composition,structure,and regeneration status of trees were assessed in five dry Afromontane forests.In each of the forests,trees having≥5 cm diameter at breast height were identified and measured in 80 quadrats(20×20m^(2)).We compared tree species composition and similarities,stem densities,frequencies,basal area and importance value index of trees.Harvesting index was calculated to 13.3%in the least disturbed and 22.5%in highly disturbed forests.A total of 1,655 individuals representing 38 species and 28 families were recorded.The tree densities varied from 364.1 to 664.1stem ha^(−1) with an average basal area of 20.7m^(2) ha^(−1).The analysis showed significant differences in basal areas of tree species between the least and highly disturbed forests.Seedling densities ranged from 2000 to 8162.5 stem ha^(−1) and sapling densities ranged from 512.5 to 2562.5 stem ha^(−1).The anthropogenic disturbances revealed high degradation of population structure and regeneration statutes of the trees in the studied forest ecosystem.In conclusion,the study provided empirical results on the dominance,population structure,importance value and regeneration status of tree species,which would be instrumental for the development of successful rehabilitation strategies for the studied forests.展开更多
：In this paper, a class of similar composite systems is discussed, whose interconnections areasymmetrical and mismatched. The interconnection condition is proposed. Based on it, the interconnectionsare divided into t...：In this paper, a class of similar composite systems is discussed, whose interconnections areasymmetrical and mismatched. The interconnection condition is proposed. Based on it, the interconnectionsare divided into two parts. One satisfies the interconnection condition, by means of the two--step method,the decentralized controllers are designed. The other does not satisfy the interconnection condition, but thisis offsetted by good quality of the system itself. Based on these, a sufficient condition is given by some linearmatrix inequalities, which makes the studied systems quadratic stabile via linear decentralized controllers bymaking use of the information of interconnections better.展开更多
In this paper, a class of similar composite systems is discussed, and the interconnections in such systems may be asymmetrical and mismatched. To make full use of the interconnections, the two steps method is proposed...In this paper, a class of similar composite systems is discussed, and the interconnections in such systems may be asymmetrical and mismatched. To make full use of the interconnections, the two steps method is proposed to design the decentralized controllers. First step: design unreal interconnections to change the system into new form with matched condition; second step: design the decentralized controllers by the regular method for the new system. The controllers we have guarantee the system quadratic stability.展开更多
基金supported by National Natural Science Foundation of China(41271115)
文摘Soil seed banks can provide a mechanistic for understanding the recruitment dynamics and can inform conservation management of ecosystems. To investigate the contribution of soil seed banks to vegetation restoration in moving sand dune systems, we compared seed structure and species similarity between soil seed banks and standing vegetation among moving sand dunes, ecotones and dune slacks in northeast China. Average seed density in dune slacks was greater than in ecotones or moving sand dunes. Seed density in the soil layer of 0-10 cm was greater than at 10-20 cm both in the moving sand dunes and the eco- tones, but seed densities were similar at depths of 10-20 and 20-30 cm in moving sand dunes. Moreover, the spatial autocorrelation of seed density on moving sand dunes was weak but was strong on the ecotones and dune slacks. The species in the soil seed bank of moving sand dune systems were nearly all annuals, and the low similarity was mainly due to the lack of perennial species that were common in standing vegetation. Consequently, vegetation restoration cannot mainly rely on the soil seed banks in the movingsand dunes and more attention should be paid to protection of the dune slacks because they are the main source of seed disperse and seedling recruitment in moving sand dune systems.
基金We are grateful to Addis Ababa University(AAU)and Ethiopian Environment and Forestry Research Institute(EERIE)for their financial support.
文摘Species composition,structure,and regeneration status of trees were assessed in five dry Afromontane forests.In each of the forests,trees having≥5 cm diameter at breast height were identified and measured in 80 quadrats(20×20m^(2)).We compared tree species composition and similarities,stem densities,frequencies,basal area and importance value index of trees.Harvesting index was calculated to 13.3%in the least disturbed and 22.5%in highly disturbed forests.A total of 1,655 individuals representing 38 species and 28 families were recorded.The tree densities varied from 364.1 to 664.1stem ha^(−1) with an average basal area of 20.7m^(2) ha^(−1).The analysis showed significant differences in basal areas of tree species between the least and highly disturbed forests.Seedling densities ranged from 2000 to 8162.5 stem ha^(−1) and sapling densities ranged from 512.5 to 2562.5 stem ha^(−1).The anthropogenic disturbances revealed high degradation of population structure and regeneration statutes of the trees in the studied forest ecosystem.In conclusion,the study provided empirical results on the dominance,population structure,importance value and regeneration status of tree species,which would be instrumental for the development of successful rehabilitation strategies for the studied forests.
文摘：In this paper, a class of similar composite systems is discussed, whose interconnections areasymmetrical and mismatched. The interconnection condition is proposed. Based on it, the interconnectionsare divided into two parts. One satisfies the interconnection condition, by means of the two--step method,the decentralized controllers are designed. The other does not satisfy the interconnection condition, but thisis offsetted by good quality of the system itself. Based on these, a sufficient condition is given by some linearmatrix inequalities, which makes the studied systems quadratic stabile via linear decentralized controllers bymaking use of the information of interconnections better.
文摘In this paper, a class of similar composite systems is discussed, and the interconnections in such systems may be asymmetrical and mismatched. To make full use of the interconnections, the two steps method is proposed to design the decentralized controllers. First step: design unreal interconnections to change the system into new form with matched condition; second step: design the decentralized controllers by the regular method for the new system. The controllers we have guarantee the system quadratic stability.
