Forest operations,tree species composition and decline in rainfall explain runoff changes in the Nacimiento experimental catchments,south central Chile     

Andrés Iroumé  Julia Jones  James C. Bathurst 《水文研究》2021,35(6):e14257

Few long-term studies have explored how intensively managed short rotation forest plantations interact with climate variability. We examine how prolonged severe drought and forest operations affect runoff in 11 experimental catchments on private corporate forest land near Nacimiento in south central Chile over the period 2008–2019. The catchments (7.7–414 ha) contain forest plantations of exotic fast-growing species (Pinus radiata, Eucalyptus spp.) at various stages of growth in a Mediterranean climate (mean long-term annual rainfall = 1381 mm). Since 2010, a drought, unprecedented in recent history, has reduced rainfall at Nacimiento by 20%, relative to the long-term mean. Pre-drought runoff ratios were <0.2 under 8-year-old Eucalyptus; >0.4 under 21-year-old Radiata pine and >0.8 where herbicide treatments had controlled vegetation for 2 years in 38% of the catchment area. Early in the study period, clearcutting of Radiata pine (85%–95% of catchment area) increased streamflow by 150 mm as compared with the year before harvest, while clearcutting and partial cuts of Eucalyptus did not increase streamflow. During 2008–2019, the combination of emerging drought and forestry treatments (replanting with Eucalyptus after clearcutting of Radiata pine and Eucalyptus) reduced streamflow by 400–500 mm, and regeneration of previously herbicide-treated vegetation combined with growth of Eucalyptus plantations reduced streamflow by 1125 mm (87% of mean annual precipitation 2010–2019). These results from one of the most comprehensive forest catchment studies in the world on private industrial forest land indicate that multiple decades of forest management have reduced deep soil moisture reservoirs. This effect has been exacerbated by drought and conversion from Radiata pine to Eucalyptus, apparently largely eliminating subsurface supply to streamflow. The findings reveal tradeoffs between wood production and water supply, provide lessons for adapting forest management to the projected future drier climate in Chile, and underscore the need for continued experimental work in managed forest plantations.  相似文献   

关于网络企业经济效益的评价理论研究     

岳正华  李黎 《成都信息工程学院学报》2001,16(3):192-198

网络经济是相对于大工业经济而言的，其网络企业经济效益的评价，可以从网络企业成本及收益两个方面讨论，然后以投入产出比等五个方面来建立其评价指标体系。  相似文献   

Feasibility of pre-earthquake strengthening of buildings based on cost-benefit and life-cycle cost analysis, with the aid of fragility curves   总被引：1，自引：1，他引：0  

Andreas J. Kappos  E. G. Dimitrakopoulos 《Natural Hazards》2008,45(1):33-54

There are two fundamental questions this article aims to deal with. First, whether a pre-earthquake strengthening of a large and heterogeneous building stock (the emphasis here is on building types common in S. Europe), is economically feasible or not, and second what is the optimal retrofit level for mitigating the seismic risk. To this purpose contemporary decision making tools, namely cost-benefit and life-cycle cost analyses, are tailored to the needs of the present study, and implemented with the aid of an ad-hoc developed new software application (COBE06). A method for estimating the reduction in structural vulnerability due to retrofit is proposed, as well as a methodology to determine the optimum retrofit level using the fragility curve approach. Finally, the proposed methodology is used in a pilot application that concerns the city of Thessaloniki, and results are drawn for the feasibility of strengthening the reinforced concrete building stock in this city.  相似文献   

Reliability-Based Optimal Design for Very Large Floating Structure     

张淑华 《中国海洋工程》2003,17(1)

1 .ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅａｐｐｒａｉｓａｌｏｆａｇｏｏｄｄｅｓｉｇｎｆｏｒａｖｅｒｙｌａｒｇｅｆｌｏａｔｉｎｇｓｔｒｕｃｔｕｒｅ(ＶＬＦＳ)ｔｈａｔｗｉｌｌｓｅｒｖｅｉｎａｓｐｅｃｉ ｆｉｅｄｏｃｅａｎａｒｅａｒｅｑｕｉｒｅｓｔｈａｔｔｈｅｓｔｒｕｃｔｕｒａｌｓｙｓｔｅｍｂｅｅｃｏｎｏｍｉｃａｌｌｙｄｅｓｉｇｎｅｄ ,ｔｈｅｒｅｑｕｉｒｅｍｅｎｔｓｆｏｒｉｔｓｆｕｎｃｔｉｏｎｂｅｓａｔｉｓｆｉｅｄａｎｄｔｈｅｓｔｒｕｃｔｕｒｅｋｅｅｐｓｓｔａｂｌｅｉｎｉｔｓｗｈｏｌｅｓｅｒｖｉｃｅｐｅｒｉｏ…  相似文献   

不同软基处理方法适用性比较   总被引：8，自引：0，他引：8  

熊丛博  于定勇 《海岸工程》2003,22(1):20-26

总结分析了国内外现有的软土地基处理的各种方法。通过对采用不同方法进行软基处理的工程实例处理效果的定量对比，发现不同软基处理方法的适用性差异很大，多数工程中仅用一种方法很难达到设计要求，而两种或多种方法联合则可望取得更好的效果。  相似文献   

Potential rent and overcapacity in the Swedish Baltic Sea trawl fishery for cod (Gadus morhua)     

Eggert  Hakan; Tveteras  Ragnar 《ICES Journal of Marine Science》2007,64(3):439-445

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Stress Sharing Behavior and Its Mechanism during Consolidation Process in Composite Ground Improved by Sand Compaction Piles with Low Replacement Area Ratio     

S. -K. You  K. Oda  T. -H. Kim 《Marine Georesources & Geotechnology》2006,24(4):287-304

In order to accurately design a sand compaction pile (SCP) with low replacement area ratio, it is important to understand the mechanical interaction between the sand pile and clay ground and its mechanism during consolidation process in composite ground. In this article, therefore, a series of numerical analyses on composite ground improved by SCP with low replacement area ratio were carried out. The applicability of numerical analyses, in which an elasto-viscoplastic consolidation finite element method was applied, were confirmed by comparing the results obtained from a series of laboratory model tests with the composite ground improved by SCP. Through the results of the numerical analyses, mechanical behavior of the sand pile and clay in composite ground during consolidation is elucidated, together with a stress sharing mechanism between sand pile and clay.  相似文献   

The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems   总被引：16，自引：4，他引：16  

Stevens  J. D.; Bonfil  R.; Dulvy  N. K.; Walker  P. A. 《ICES Journal of Marine Science》2000,57(3):476-494

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关于“包装产品的计量标准型一次抽检方案”的确定     

陈峥  赵维谦  李晓川 《中国海洋大学学报(自然科学版)》1989,(4)

本文给出了“包装产品的计量标准型一次抽检方案”,并通过一个实例说明本方案比一般《计量标准型一次抽检方案》更为优越。  相似文献   

Facies distribution of the Lower Cambrian cryptic microbial and epibenthic archaeocyathan-microbial communities, western Anti-Atlas, Morocco     

J. JAVIER ÁLVARO†  SÉBASTIEN CLAUSEN†  ABDERRAZZAK EL ALBANI‡  EL HASSANE CHELLAI§ 《Sedimentology》2006,53(1):35-53

Marine microbial communities recorded in the Moroccan Anti‐Atlas were unaffected across the Neoproterozoic–Cambrian transition. A stromatolite‐dominated consortium was replaced at the beginning of the Atdabanian (ca 20 Myr after the Neoproterozoic–Cambrian boundary) by shelly metazoan and thromboid consortia, which contain the oldest biostratigraphically significant fossils of the Moroccan Cambrian. The associated collapse of microbial mat (stromatolitic) growth appears to coincide with a change from pre‐Atdabanian shallow‐water restricted conditions into Atdabanian deeper, open‐sea conditions. It is postulated that this environmental change led to an episode of improved water circulation over carbonate platform interiors, promoting shelly metazoan immigration into the region. The Tiout/Amouslek lithostratigraphic contact in the early Atdabanian marks the end of an episodically unstable seafloor as suggested by the abundance of slumping and sliding structures, and synsedimentary microfaults and cracks recorded in the underlying Tiout Member. Concurrent with the transition is the occurrence of a network of cryptic fissures and cavities that provided habitats for a coelobiontic chemosynthetic–heterotrophic microbial community composed of stromatolitic crusts, Renalcis–Epiphyton–Girvanella intergrowths, and Kundatia thalli. In the overlying Amouslek Formation, archaeocyathan–thromboid reefs were constrained by substrate stability, water depth and subsidence rate. Four reef geometries are distinguished: (i) patch reefs surrounded by shales, (ii) bioherms in which flank beds intercalate laterally with carbonate and shale inter‐reef sediments, (iii) biostromes or low‐relief structures formed as a result of lateral accretion of patch reefs, and (iv) kalyptrate complexes that nucleated because of a marked tendency for aggregation, and in which patch reefs and bioherms occur stacked together bounded by clay–marl–silt seams.  相似文献