Spatial patterns of Douglas-fir and aspen forest expansion

Spatial patterns, rates, and density of encroaching forests into adjacent grasslands have important implications for long-term land use management and resource planning. This study examines the effects of Douglas-fir (Pseudotsuga menzeisii) and aspen (Populus tremuloides) regeneration mechanisms on sucker and seedling spatial patterns, distance from adult trees, and density in encroaching forests. A total of 8,924 aspen suckers and 1,244 Douglas-fir seedlings were counted and mapped in 2,920 quadrats (5 m × 5 m) in 106 plots along a lower forest-grassland ecotone in the Centennial Valley, MT, USA. Sucker and seedling spatial patterns were analyzed using Morisita’s I index. Average sucker and seedling density per quadrat and distance from adult trees were estimated for each plot and compared between aspen-dominated plots and Douglas-fir-dominated plots using ANOVA tests. Aspen suckers were established in a clustered spatial pattern at a significantly higher density and a significantly shorter distance from the adult trees. In contrast, Douglas-fir seedlings were established in varying spatial patterns at a significantly lower density and a significantly greater distance from the adult trees. Forest encroachment into the adjacent grassland in the Centennial Valley is occurring in contrasting patterns and at varying rates and densities due to the difference in aspen and Douglas-fir regeneration mechanisms.     

红星凤梨与其吸芽种苗生理指标及成品花品质比较

利用饱和乙炔溶液对进口红星凤梨种苗及其吸芽种苗进行催花处理,分析并比较了两者在生理指标及成品花品质上的差异,结果表明:在同等栽培、管理条件下,进口种苗的各项生理指标及成品花品质都优于吸芽种苗;同时,吸芽种苗通过改良驯化技术、加强栽培管理、提前催花等方法,可以在实际生产中达到进口种苗的优良品质。     

Threats, conservation strategies, and prognosis for suckers (Catostomidae) in North America: insights from regional case studies of a diverse family of non-game fishes

Catostomid fishes are a diverse family of 76+ freshwater species that are distributed across North America in many different habitats. This group of fish is facing a variety of impacts and conservation issues that are somewhat unique relative to more economically valuable and heavily managed fish species. Here, we present a brief series of case studies to highlight the threats such as migration barriers, flow regulation, environmental contamination, habitat degradation, exploitation and impacts from introduced (non-native) species that are facing catostomids in different regions. Collectively, the case studies reveal that individual species usually are not threatened by a single, isolated factor. Instead, species in general face numerous stressors that threaten multiple stages of their life history. Several factors have retarded sucker conservation including widespread inabilities of field workers to distinguish some species, lack of basic natural history and ecological knowledge of life history, and the misconception that suckers are tolerant of degraded conditions and are of little social or ecological value. Without a specific constituent group lobbying for conservation of non-game fishes, all such species, including members of the catostomid family, will continue to face serious risks because of neglect, ignorance, and misunderstanding. We suggest that conservation strategies should incorporate research and education/outreach components. Other conservation strategies that would be effective for protecting suckers include freshwater protected areas for critical habitat, restoration of degraded habitat, and design of catostomid-friendly fish bypass facilities. We believe that the plight of the catostomids is representative of the threats facing many other non-game freshwater fishes with diverse life-history strategies globally.