Environmental and economic costs of soil erosion and conservation benefits

Soil erosion is a major environmental threat to the sustainability and productive capacity of agriculture. During the last 40 years, nearly one-third of the world's arable land has been lost by erosion and continues to be lost at a rate of more than 10 million hectares per year. With the addition of a quarter of a million people each day, the world population's food demand is increasing at a time when per capita food productivity is beginning to decline.     

1994—2014年西方乡村研究: 从乡村景观到乡村社会

目的研究余姚市30个新农村文化广场绿地的树种构成及其多样性,为该地区及地区新农村绿化建设规划提供科学参考。方法利用群落学调查方法,分析调查样地内的树种组成、优势树种重要值、物种多样性及树木胸径结构特征。结果样地内共有木本植物41科55属64种,其中以蔷薇科的种类最丰富,其次为冬青科、木犀科和芸香科等;但仅含1属1种的科占多数。各样地中,乔木以香樟的重要值最突出(28.08%),其次为桂花(9.58%)、银杏(6.60%)和女贞(4.72%)等;灌木以石楠(31.80%)、檵木(12.90%)和杜鹃(8.38%)等占有较大优势。各样地的树木多样性普遍偏低,相公潭村的树木多样性优于其他样地。本区域文化广场绿化树木的选用多以中、低龄乔木为主,径级结构多呈正金字塔形。结论提升树种多样性、优化树种组成结构和增加乡土树种占比是本区域新农村绿化建设需关注的重点问题。