Effect of artificial reefs (southern Portugal) on sediment–water transport of nutrients: Importance of the hydrodynamic regime

The present study investigates the differences between nutrient fluxes and particulate organic matter within an artificial reef system (AR) deployed in August 2002 off Faro (Algarve, Southern Portugal) and in a non-reef area (NRA), and how fluxes and suspended material may be affected by the hydrodynamic regime. Surveys to collect sediment cores, suspended/settled particles and overlying water samples were carried out by divers, from March (2006) to October (2007) in AR and NRA. Sediment cores and settled particles were collected to determine grain size, organic and inorganic carbon, nitrogen and phosphorus content. Overlying water and pore water samples were analysed for ammonium, nitrite, nitrate, phosphate, silicate, dissolved organic nitrogen, dissolved organic phosphorus and chlorophyll a. Results from the period studied showed that: (1) the benthic export of dissolved N, P and Si was 2–3 times higher at AR; (2) the particulate organic carbon (POC), nitrogen (PON) and phosphorus (POP) in suspended/settled particles were about 1.5 times higher at AR; (3) at both AR and NRA, the benthic export of dissolved N, P and Si, during a calm weather period, was 2–4 times higher than during or immediately after a storm event; and (4) at both sites, particulate organic compounds (POC, PON and POP) increased about 20 times during a storm event. These findings suggest that both the nutrients transport from sediment to water column and the quantity/quality of suspended/settled particles were highly dependent on the existence of reef structures and on the hydrodynamic regime.     

普里兹湾水文特征与变化

根据澳大利亚学者分别在１９８２年１２月和１９８７年２月普里兹湾的调查资料,并结合中国＂极地＂号南极考察船１９９０～１９９１年间的调查资料印证,提出在中国＂中山站＂所在地普里兹湾在初夏与晚夏期间的水文特征。     

中国参与构建2012年后国际气候制度的战略思考

 2009年将是构建2012年后应对气候变化国际制度的关键时期,而除了温室气体的减排目标和责任分摊之外,减缓和适应气候变化以及相应的技术和资金支持都将会是最为关键的影响要素。在对国际气候制度的关键影响要素进行梳理并对其进程进行分析的基础上,结合不断变化的国际国内政治、经济、环境和社会形势,对中国在2012年后国际气候谈判以及中长期应对气候变化的策略进行了探讨。     

河南境内黄河流域地下水系统划分与系统分析

在河南境内黄河流域地下水系统划分的研究，探讨区域地下水系统划分应依据两个基本条件：（1）依据地质环境因素确定含水层系统；（2）含水层系统是否具有独立的水循环流动系统，即拥有完整的补给，径流，排泄系统。河南境内黄河流域划分成5个区域地下水系统（3个孔隙地下水系统，2个裂隙岩溶水系统），都具有稳定的边界，便于对地下水资源做出准确评价，开发，规划和管理。     

社会—生态系统体制转换视角下的黄土高原乡村转型发展——以长武县洪家镇为例

社会—生态系统理论为中国乡村转型发展的过程格局研究提供了新的分析思路,运用体制转化理论及其研究框架,选取陕西省长武县洪家镇为案例地,从村域尺度社会—生态系统体制变化为切入点揭示了当地乡村转型的背景和环境因素,重点探讨农户尺度的社会—生态系统体制转换影响因素及其稳健性,从微观角度审视西北乡村转型的基本特征,主要结论包括：① 当地乡村社会—生态系统体制已由传统农业体制转变为新型农业体制,其中某些家庭体制正在向非农体制转换。② 家庭特征是农户体制发生转换的客观条件;耕地质量、劳动力数量与质量是农户体制转换的内在动因;户主年龄、文化水平及社会网络是农户体制转换方向的决定因素。③ 农户家庭体制转换呈现出发散和聚合并存现象,且不同家庭的稳健性存在明显差异,基于种植业结构和收入对农户家庭进行分类,不同类型农户家庭体制的稳健型依次表现为其：苹果非农均衡型>非农收入主导型>粮食非农均衡型>苹果收入主导型>传统收入主导型。最后基于农户视角对乡村转型的微观研究进行探讨,并提出后续深化研究的方向和实践启示。     

黄河源区水文模拟中地形和融雪影响

为分析地形和融雪对水文模拟影响,利用SWAT模型在黄河源区进行1960—1990年水文模拟。二者的影响分别通过对子流域划分高程带和运用融雪模块来体现。研究表明,单独考虑融雪影响或考虑融雪、地形的共同影响下,模拟结果均能达到合格;单独考虑地形的影响下能达到良好。相比融雪影响,地形对流域水量平衡的模拟起主要作用。划分高程带对子流域的气温影响较大,对降水影响小。子流域气温的降低使得蒸散发减小,从而增加产水量,其中地下水增加最多,其次是地表径流和壤中流。地形和融雪的影响使地下水的补给来源改变,调整地下水参数后,最终模拟结果达到优秀。地形和融雪在黄河源区水文模拟中的影响可以为其他高山地区水文研究提供参考。     

中小型水库抗暴雨能力的概念与计算方法

我国中小型水库众多,且大多位于山丘区,具有集雨面积小、洪水突发性强、预见期短、防洪能力弱等特点。中小型水库抗暴雨能力预报预警是有效提升中小型水库安全度汛能力的重要非工程措施。系统阐述了中小型水库抗暴雨能力的概念与含义,基于试算反推法给出了抗暴雨能力的计算步骤,并在典型中小型水库进行了应用。研究表明:选用抗暴雨能力作为中小型水库防汛调度参考指标,可以有效延长洪水预见期,大幅提升中小型水库安全度汛能力。     

Biophysical Regulation of Carbon Flux in Different Rainfall Regime in a Northern Tibetan Alpine Meadow

Inter-annual variability in total precipitation can lead to significant changes in carbon flux. In this study, we used the eddy covariance (EC) technique to measure the net CO₂ ecosystem exchange (NEE) of an alpine meadow in the northern Tibetan Plateau. In 2005 the meadow had precipitation of 489.9 mm and in 2006 precipitation of 241.1 mm, which, respectively, represent normal and dry years as compared to the mean annual precipitation of 476 mm. The EC measured NEE was 87.70 g C m^-2 yr^-1 in 2006 and -2.35 g C m^-2 yr^-1 in 2005. Therefore, the grassland was carbon neutral to the atmosphere in the normal year, while it was a carbon source in the dry year, indicating this ecosystem will become a CO₂ source if climate warming results in more drought conditions. The drought conditions in the dry year limited gross ecosystem CO₂ exchange (GEE), leaf area index (LAI) and the duration of ecosystem carbon uptake. During the peak of growing season the maximum daily rate of NEE and P_max and α were approximately 30%-50% of those of the normal year. GEE and NEE were strongly related to photosynthetically active radiation (PAR) on half-hourly scale, but this relationship was confounded by air temperature (T_a), soil water content (SWC) and vapor pressure deficit (VPD). The absolute values of NEE declined with higher T_a, higher VPD and lower SWC conditions. Beyond the appropriate range of PAR, high solar radiation exacerbated soil water conditions and thus reduced daytime NEE. Optimal T_a and VPD for maximum daytime NEE were 12.7℃ and 0.42 KPa respectively, and the absolute values of NEE increased with SWC. Variation in LAI explained around 77% of the change in GEE and NEE. Variations in R_e were mainly controlled by soil temperature (T_s), whereas soil water content regulated the responses of Re to T_s.     

Classifying the flow regimes of Mediterranean streams using multivariate analysis

Rivers in the Mediterranean region often exhibit an intermittent character. An understanding and classification of the flow regimes of these rivers is needed, as flow patterns control both physicochemical and biological processes. This paper reports an attempt to classify flow regimes in Mediterranean rivers based on hydrological variables extracted from discharge time series. Long‐term discharge records from 60 rivers within the Mediterranean region were analysed in order to classify the streams into different flow regime groups. Hydrological indices (HIs) were derived for each stream and principal component analysis (PCA) and then applied to these indices to identify subsets of HIs describing the major sources of variations, while simultaneously minimizing redundancy. PCA was performed for two groups of streams (perennial and temporary) and for all streams combined. The results show that whereas perennial streams are mainly described by high‐flow indices, temporary streams are described by duration, variability and predictability indices. Agglomerative cluster analysis based on HIs identified six groups of rivers classified according to differences in intermittency and variability. A methodology allowing such a classification for ungauged catchments was also tested. Broad‐scale catchment characteristics based on digital elevation, climate, soil and land use data were derived for each long‐term station where these data were available. By using stepwise multiple regression analysis, statistically significant relationships were fitted, linking the three selected hydrological variables (mean annual number of zero‐flow days, predictability and flashiness) to the catchment characteristics. The method provides a means of simplifying the complexity of river systems and is thus useful for river basin management. Copyright © 2015 John Wiley & Sons, Ltd.