Atmospheric deposition of nitrogen at five subtropical forested sites in South China

Elevated concentrations of reactive nitrogen (N) in precipitation have been reported for many cities in China. Due to increased use of fossil fuels and expansion in agriculture, further increases in deposition of ammonia (NHx) and reactive N oxides (NOy) are predicted. Increased deposition of reactive N is likely to affect N dynamics and N runoff in forest ecosystems. Yet, in China little work has been done to quantify the levels of atmospheric N deposition in such systems. Here, we assess the deposition of inorganic N (ammonium, NH4+ and nitrate, NO3-) for five subtropical forest ecosystems in remote and urban areas of South China. Annual volume-weighted concentrations in bulk precipitation range from 0.18 to 1.55 mg NH4+ -N L(-1) and from 0.12 to 0.74 mg NO3- -N L(-1). These values are large and several times greater than those reported for remote sites of the world. The fluxes of total inorganic N (TIN) in wet-only deposition range from 0.8 to 2.3 g N m(-2) yr(-1), with NH4+ -N contributing 54% to 77%. Both the tree canopy and the ground vegetation layer are important in determining the net N flux reaching the forest floor, but the net effect varies from site to site. At TieShanPing (TSP), close to Chongqing city, and at CaiJiaTang (CJT), near Shaoshan (Hunan province), the canopy represents a net source of N, probably due to dry deposition. At the other three sites (LiuChongGuan (LCG), LeiGongShan (LGS), both in Guizhou province, and LiuXiHe (LXH) in Guangdong), a net loss of reactive N from precipitation water occurs in the canopy, probably due to uptake processes. The total annual atmospheric TIN load is estimated to range from at least 0.8 g N m(-2) yr(-1) to 4.0 g N m(-2) yr(-1), with a considerable contribution from dry deposition. Concentrations and fluxes of inorganic N in tree canopy throughfall are greater than those in North America. Also the contribution of NH4+ -N to TIN fluxes in throughfall (40% to 70%) is greater than in North America. Our sites have N deposition levels and NH4+ -N contributions similar to those found in Northwest and central Europe. The TIN loads at TSP and CJT far exceed 2.5 g N m(-2) yr(-1), which is the N deposition load above which NO3- leaching is expected in temperate and boreal forests.     

植被增加边坡降雨入渗对边坡稳定性影响研究

植被根系提高土壤渗透性和抗侵蚀性,植被盖度越大径流起始时间越长,植被提高边坡的入渗率和减少土壤流失相互促进,共同作用的结果是保持水土,所以植被增加边坡降雨入渗的作用是十分显著的.大多数植物的根系分布在浅层,根际区土壤储水能力强,由于植被对根际区下层土壤的渗透性影响不大,而且认为植被对降雨入渗对根际区土壤水分的影响明显,而对边坡根际区下层土壤水分影响不明显,植被增加边坡降雨入渗不影响边坡深层稳定性.     

岩质边坡喷混植生护坡技术浅析

1概述随着我国综合国力的不断增强,铁路和高速公路建设事业蓬勃发展,各方面都取得了很大的成就。但在修路的过程中会有大量的开山挖方,改变了原始地貌,造成沿线植被破坏、水土流失、生态失去平衡,甚至造成山体坍塌和滑坡。随着社会的进步,人们对生态环境保护的要求也越来越高。     

道路生态护坡技术探讨

针对高速公路护坡工程的需要,提出一种新型护坡形式——生态护坡技术,研究了生态植被护坡作用机理,阐述了生态植被护坡工程的施工工艺流程,并通过工程实例证明了该护坡技术的可行性。     

浅谈公路边坡生态护坡技术

重点就喷混植生防护技术的基质选择和配比、植物品种的选择和适用以及施工工艺流程进行了分析和阐述,并简要介绍了其他几种较为常见的边坡生态防护技术,以帮助工程技术人员合理选择边坡防护类型,提高边坡防护的经济效益和生态效益。     

怒江地区泥石流形成机理初探

结合具体工程实例,从地形地貌、气象与水文方面入手,对怒江地区泥石流形成条件进行了深入剖析,并对泥石流的地形、冲蚀、淤积物和植被特征进行了阐述,为野外鉴定泥石流提供了参考。     

Landscape dynamics of Mediterranean montane grasslands over 60 years and implications for habitats conservation. A case study in the northern Apennines (Italy)

Widespread trends of abandonment have strongly affected Mediterranean mountains after the Second World War, triggering spontaneous recolonisation of forests. A diachronic analysis of the landscape in a Natura 2000 site (Tuscany, Italy) was carried out using digital aerial photographs (1954, 2013) and a GIS-based methodology, focusing on territories above 1300 m a.s.l. The detected variations of total areas, patch shape, patch dimensions and selected metrics showed a notable shift of the vegetation towards woody types and a drastic reduction of open grasslands, some with high conservation value, accompanied by a strong increase in patch number, surface and edge. A decrease of SDI and SEI diversity indices was also observed. Considering that fragmentation is one of the main causes threatening habitats and species, our results point out a clear necessity for a monitoring programme and suitable actions aimed at improving the status of biodiversity-rich montane grasslands.     

生态位理论及其在工程植被护坡中的指导意义

生态位理论（niche theory）是目前国内外生态学领域的研究热点,主要从生态位的概念出发,阐述了生态位理论在植物研究中的应用价值,并指出生态位理论在工程护坡中,对物种引进、植物选型和配置的指导意义及具体做法。     

自棕地到湿地——高雄中都湿地公园植群复育计划

高雄市政府为贯彻“高雄市都会型湿地生态廊道串连计划”,定于2010年完成开辟高雄市内9处与市区紧邻的湿地公园,作为动植物生态可自由迁移于都会区内的“带状湿地生态廊道”.中都湿地公园即是此计划完成的最后一处湿地工程.高雄的生态系丰富多样,其中包含森林生态系的热带季雨林、海洋生态系的海岸林以及河口生态系的红树林.中都显地公园内规划各类植群的生长环境,期望复育成功后可诱发其所属生态系.本湿地公园完工后建议高雄市政府拟订公园内动物及植群监测计划,记录中都湿地的生态变迁,说明高雄在全球地理位置上所占的重要生态地位,并制定植群维护管理计划,使中都湿地公园可持续兼具生态及景观休憩机能.     

地表温度与植被指数相关性的空间尺度特征——以重庆市为例

为了揭示植被改善城市热岛的量化关系,以重庆市主城区为例,在不同的尺度上分析了地表温度与归一化植被指数之间的相关性,分别从全局和局部出发分析了两者之间的线性关系.结果发现,在120m尺度上两者之间的相关性最强,空间相关场表明相关性在空间上呈现较强的异质性;全局普通线性回归和地理加权回归分析发现,两者之间没有显著的线性关系,这说明可能还存在其他多种因素的复杂影响.