An investigation method with sample plots was used to study insect communities in four different growth phases of natural Populus euphratica forests, which are juvenile, middle aged, over-mature and degraded forests, ...An investigation method with sample plots was used to study insect communities in four different growth phases of natural Populus euphratica forests, which are juvenile, middle aged, over-mature and degraded forests, in Tarim, Xinjiang in July, 2005 and April, 2006. In our studies, 5,116 insect specimens, belonging to 12 orders, 61 families and 141 species, were collected. Lepidoptera and Coleoptera were the dominant orders. In middle-aged forests, species, individual numbers and diversity indices of insect com-munities were higher than those in other woodlands. The species richness and diversity indices were lowest in degraded forests be-cause of extremely scarce vegetation.展开更多
Seed dispersal is a fundamental process affecting destinies of seeds and seedlings, as well as regeneration dynamics and distribution patterns of communities. Recently however, declining Populus euphratica forests hav...Seed dispersal is a fundamental process affecting destinies of seeds and seedlings, as well as regeneration dynamics and distribution patterns of communities. Recently however, declining Populus euphratica forests have failed to regenerate by seeding, while the spatial pattern and utility of their seed rains are unclear. In this study, we designed a model to simulate seed rains based on field investigations by fitting our observations to a normal distribution and testing the model with data from three years, with ac- ceptable results. We examined the simulated results of dispersed seeds patterns on the classification of three factors, i.e., density of Sophora alopecuroides, surface soil moisture and surface soil salinity. The results of seed rain simulation show that over 70% of seeds were dispersed and confined to each of the three plots where their mother trees located. The proportion of 3：7 seeds dispersed inside and outside each plots remained largely unaltered. The differences in the amounts of dispersed seed among the different levels of each of the factors were not significant, although the distributing pattern of P. euphratica in each plot varied. Therefore, in P. eu- phratica communities, the amount of seed does not become a constraint in subsequent germination, although the surface environment does. We conclude that successful P. euphratica seed regeneration relies on less than 30% of seeds dispersed over longer distance to colonize favorable growth habitats.展开更多
文摘An investigation method with sample plots was used to study insect communities in four different growth phases of natural Populus euphratica forests, which are juvenile, middle aged, over-mature and degraded forests, in Tarim, Xinjiang in July, 2005 and April, 2006. In our studies, 5,116 insect specimens, belonging to 12 orders, 61 families and 141 species, were collected. Lepidoptera and Coleoptera were the dominant orders. In middle-aged forests, species, individual numbers and diversity indices of insect com-munities were higher than those in other woodlands. The species richness and diversity indices were lowest in degraded forests be-cause of extremely scarce vegetation.
基金supported by the National Natural Science Foundation of China(No.30570332,31070553)the 11th Five-Year Plan of the National Scientific and Technological Support Projects(2008BADB0B05)
文摘Seed dispersal is a fundamental process affecting destinies of seeds and seedlings, as well as regeneration dynamics and distribution patterns of communities. Recently however, declining Populus euphratica forests have failed to regenerate by seeding, while the spatial pattern and utility of their seed rains are unclear. In this study, we designed a model to simulate seed rains based on field investigations by fitting our observations to a normal distribution and testing the model with data from three years, with ac- ceptable results. We examined the simulated results of dispersed seeds patterns on the classification of three factors, i.e., density of Sophora alopecuroides, surface soil moisture and surface soil salinity. The results of seed rain simulation show that over 70% of seeds were dispersed and confined to each of the three plots where their mother trees located. The proportion of 3：7 seeds dispersed inside and outside each plots remained largely unaltered. The differences in the amounts of dispersed seed among the different levels of each of the factors were not significant, although the distributing pattern of P. euphratica in each plot varied. Therefore, in P. eu- phratica communities, the amount of seed does not become a constraint in subsequent germination, although the surface environment does. We conclude that successful P. euphratica seed regeneration relies on less than 30% of seeds dispersed over longer distance to colonize favorable growth habitats.
