Gradient analysis and numerical classification of apple orchard weed vegetation

Importance values based on cover and frequency were determined for 36 weed species in understory samples from 47 apple orchards located in Henderson County, North Carolina. Orchard sub-groups identified by cluster analysis of the weed composition data included two major groupings dominated by grasses and woody perennials, respectively. Ordination by detrended correspondence analysis (DECORANA) was used to extract axes of compositional variation in orchard weed vegetation. Orchard sub-groups identified by cluster analysis could be recognized in the DECORANA ordinations. All grasses, most perennial forbs and all summer-annual forbs decreased in importance along a first ordination axis based upon data from 43 orchards. Two perennial forbs and all woody perennials increased in importance along the same axis, while species-richness of weeds declined. Results of multiple regression indicated that the annual frequency of paraquat application from 1976 to 1979 was the single factor accounting for the greatest compositional variation in the first two axes of the 43-orchard ordination. Tree canopy width and in-row spacing, total extractable soil cations, and percentage soil organic matter also accounted for significant amounts of variation in weed composition. Similar results were obtained from models developed for an ordination of the 35 grass-dominated orchards, suggesting the importance of management, structural and soil factors in determining weed composition in apple orchards.     

陕西民俗文化旅游资源的保护与开发

陕西民俗文化旅游资源丰富,具有较高的社会价值和旅游价值,但由于政府部门的疏于重视和广大民众认识的浅薄,导致陕西民俗文化旅游资源受到严重的破坏,同时也造成不良风气的大量出现,使这些价值未能得以发挥.针对这一现状,以全国民俗文化的保护和开发为参照,结合陕西民俗文化旅游资源的自身特点,从保护和发展两个方面涉及的具体问题为出发点,就具体的问题提出了具体的建议,希望以此引起各方重视.参5.