西安高陵人工林土壤干层与含水量季节变化研究

通过野外调查和室内测定,利用烘干称重法对高陵地区丰水年前后不同人工林下0~6 m土壤含水量及土壤水分的季节变化进行研究。结果表明,2002年高陵田家村中国梧桐林和杨树林下160~400 cm范围内均已发育了土壤干层。经过2003年丰水年充沛的降水补给,2004年高陵团庄槐树林、杏树林0~6 m土层均未出现土壤干层,说明水分在丰水年得到很好恢复。丰水年后梨、杏、槐三种人工林160~400、410~600 cm层位土壤含水量均显示春季最高,夏季次之,秋季降到最低或略微上升。     

陕西黄土高原人工林土壤干层及形成原因

1 Introduction Abroad, a lot of research on soil water removal, seeping and evaporation has been done (Ole, 1998; Rapp, 2000). A seeping model of soil water was suggested (Yuin, 1998) and it was known that water removal is very slow in the unsaturated zon…     

渭河平原全新世气候与季风强度变化

为探讨渭河平原全新世黄土沉积时期的气候、土壤与季风变化,本研究以2.15 m厚度的宝鸡宝陵剖面为研究对象,选取了化学元素、碳酸钙以及土壤微结构作为研究指标,对全新世气候特征、土壤类型以及季风降水与强度变化进行探讨。实验结果表明,S₀发育时期表现为中等化学风化,CaCO₃含量在S₀中下部小于1%,在全新世黄土层中的平均含量为12.14%。S₀以发育新生红色粘土胶膜的致密块状微结构为主要特征,L₀以孔隙发育的团块结构为主要特征。主要结论如下：1)晚全新世L₀黄土堆积时气候相对冷干,年均降水量为500～600 mm,冬季风增强,冬季风与夏季风强度相近,并非冬季风占主导地位;2)晚全新世L₀发育时夏季风带来的降水量占当时年降水量的50%左右,与其他来源的降水量基本相同;3)晚全新世发育的L₀黄土受成壤作用较弱,具有碱性褐色土的特征。中全新世的成壤作用较强,发育的S₀古土壤为湿润条件下的亚热带黄棕壤;...     

A new approach for detecting and mapping sewage impacts

Increased nitrogen loading has been implicated in eutrophication occurrences worldwide. Much of this loading is attributable to the growing human population along the world's coastlines. A significant component of this nitrogen input is from sewage effluent, and delineation of the distribution and biological impact of sewage-derived nitrogen is becoming increasingly important. Here, we show a technique that identifies the source, extent and fate of biologically available sewage nitrogen in coastal marine ecosystems. This method is based on the uptake of sewage nitrogen by marine plants and subsequent analysis of the sewage signature (elevated delta 15N) in plant tissues. Spatial analysis is used to create maps of delta 15N and establish coefficient of variation estimates of the mapped values. We show elevated delta 15N levels in marine plants near sewage outfalls in Moreton Bay, Australia, a semi-enclosed bay receiving multiple sewage inputs. These maps of sewage nitrogen distribution are being used to direct nutrient reduction strategies in the region and will assist in monitoring the effectiveness of environmental protection measures.