Carbon input, production and turnover in the interstices of a Lake Tegel bank filtration site, Berlin, Germany     

Anja Hoffmann  Günter Gunkel 《Limnologica》2011,41(3):151-159

The sandy littoral zone of Lake Tegel (Berlin, Germany) was investigated during 2004–2006 down to sediment depths ≥26 cm to derive a scheme of seasonal carbon turnover under induced bank filtration conditions. Carbon turnover processes were quantified regarding external and internal sources of dissolved and particulate organic matter (DOM and POM), primary production, community respiration, redox potential as well as specific loads of soluble chemical compounds such as nitrogen, iron, manganese and DOC.Over the course of the year, infiltrating DOC decreased by about 13–20% within the upper 26 cm sediment of the infiltration stretch. Gradients of all observed soluble compounds that are highly cross-linked to biological activities were highest in the topmost centimetre. In this depth mass balances (output–input) were negative concerning NO₃-N (−1 mg dm⁻² d⁻¹, summer mean) and DOC (−2 mg dm⁻² d⁻¹, winter mean), respectively, while specific loads of cations such as manganese reached up to 0.2 mg dm⁻² d⁻¹ during summer. Carbon mineralization ranged between 3 and 7 mg C dm⁻² d⁻¹ and was nearly twice as high in summer as in winter. The turnover of the infiltrating DOC contributed maximally 25% in summer to 50% in winter to the entire organic carbon mineralization. Gross and net primary production differed up to a factor of >10, indicating very fast turnover reactions and the predominance of community respiration and mineralization, respectively. The POC in the upper sediment layer (10 cm) temporally varied around 1% sediment d.w.; benthic algae, organic seston input and autumnal leaf fall contributed similar percentages to the POC pool.  相似文献   

鄂西地区中二叠统栖霞组下部烃源岩形成机理   总被引：5，自引：1，他引：4       下载免费PDF全文

韦恒叶  陈代钊  遇昊  汪建国 《地质科学》2011,46(1):68-82

中二叠统柄霞组下部烃源岩广泛发育于扬子地台台内盆地和台地边缘.多种古环境参数V/(V+Ni)、V/Cr、Cu、Ni、Zn、Hf、Nb、自生U含量和烃类百分含量的研究表明,栖霞组烃源岩周期性变化的有机质埋藏量主要受控于海洋表层初级生产力,而生产力的变化受气候引起的海平面变化的影响.海平面的上升带来丰富的营养物质,提高海洋...  相似文献   

浅谈啧锚网技术在高边坡防护中的应用     

刘彦东 《中国勘察设计》2011,(2):42-44

喷锚同支护是靠锚杆、钢筋同和混凝上层共同工作来提高边坡岩土的结构强度和抗变形刚度,减小岩(土)体侧向变形,增强边坡的整体稳定性.  相似文献   

Implications of local-scale productivity on compensatory growth in a semi-arid shrubland     

M. Gruntman  A. Novoplansky 《Journal of Arid Environments》2011,75(3):279-283

Grazing is a dominant determinant of aboveground net primary production (ANPP) and composition of plant communities. However, ANPP can be maintained following grazing due to compensatory growth, the level of which might depend on additional environmental factors, such as precipitation and edaphic conditions. Several studies have shown that along large-scale regional gradients, community-level compensatory ability is positively correlated with ANPP and soil resource availability. However, community-level responses to grazing are also expected to be affected by local-scale heterogeneity in ANPP, particularly under low primary productivity typical to arid environments. Here, we studied the effect of local-scale variations in ANPP on the compensatory growth of an annual community in a semi-arid region. For two consecutive years, ANPP was evaluated following shoot damage in sites with different primary productivity. The results demonstrated that annual ANPP varied significantly among sites and among plots within sites; however, compensatory ability was negatively correlated with annual ANPP, with overcompensation in the least productive patches and under-compensation in the most productive patches. This pattern contradicts the positive correlation between ANPP and compensatory ability commonly found along large-scale productivity ecoclines, suggesting that the effects of ANPP on compensatory ability might be scale-dependent.  相似文献   

Carbon and water exchange in semiarid ecosystems in SE Spain     

F. Domingo  P. Serrano-Ortiz  A. Were  L. Villagarcía  M. García  D.A. Ramírez  A.S. Kowalski  M.J. Moro  A. Rey  C. Oyonarte 《Journal of Arid Environments》2011,75(12):1271-1281

The changing climate is affecting biological and physical processes occurring in the biosphere, including the biogeochemical cycles of water and carbon. The response of ecosystem carbon exchange to changes in temperature and the water balance is still very uncertain, a fact that highlights the need for research in order to understand the role of the biosphere in the future global carbon budget. South east Spain is on the borderline between the tropical and mid-latitude climate zones, with climates ranging from sub-humid to arid, and the majority representing the driest area in Europe. Initial predictions on climate change for this region point to decreases in total precipitation and the number of precipitation events, meaning a decrease in water availability underlining the vulnerability of the region to desertification. This region, due to these special climatic conditions, has been the subject of experimental carbon and water field research in recent years. This paper defines the state of the art of carbon and water balance measurement and modelling studies in this region, analyses the different processes involved in aggregate exchanges (vegetation and soil; net ecosystem carbon balance–evapotranspiration, photosynthesis–transpiration, soil respiration–evaporation), and identifies needs for future research.  相似文献   

Nitrogen limitation in arid-subhumid ecosystems: A meta-analysis of fertilization studies     

L. Yahdjian  L. GherardiO.E. Sala 《Journal of Arid Environments》2011,75(8):675-680

Evidence supporting water limitation in arid-semiarid ecosystems includes strong correlations between aboveground net primary production (ANPP) and annual precipitation as well as results from experimental water additions. Similarly, there is evidence of N limitation on ANPP in low precipitation ecosystems, but is this a widespread phenomenon? Are all arid-semiarid ecosystems equally limited by nitrogen? Is the response of N fertilization modulated by water availability?We conducted a meta-analysis of ANPP responses to N fertilization across arid to subhumid ecosystems to quantify N limitation, using the effect-size index R which is the ratio of ANPP in fertilized to control plots. Nitrogen addition increased ANPP across all studies by an average of 50%, and nitrogen effects increased significantly (P = 0.03) along the 50-650 mm yr⁻¹ precipitation gradient. The response ratio decreased with mean annual temperature in arid and semiarid ecosystems but was insensitive in subhumid systems. Sown pastures showed significant (P = 0.007) higher responses than natural ecosystems. Neither plant-life form nor chemical form of the applied fertilizer showed significant effects on the primary production response to N addition. Our results showed that nitrogen limitation is a widespread phenomenon in low-precipitation ecosystems and that its importance increases with annual precipitation from arid to subhumid regions. Both water and N availability limit primary production, probably at different times during the year; with frequency of N limitation increasing and frequency of water limitation decreasing as annual precipitation increases. Expected increase N deposition, which could be significant even in arid ecosystems, would increase aboveground net primary production in water-limited ecosystems that account for 40% of the terrestrial surface.  相似文献   

Assessing gaps in irrigated agricultural productivity through satellite earth observations—A case study of the Fergana Valley,Central Asia     

《International Journal of Applied Earth Observation and Geoinformation》2017

Improving crop area and/or crop yields in agricultural regions is one of the foremost scientific challenges for the next decades. This is especially true in irrigated areas because sustainable intensification of irrigated crop production is virtually the sole means to enhance food supply and contribute to meeting food demands of a growing population. Yet, irrigated crop production worldwide is suffering from soil degradation and salinity, reduced soil fertility, and water scarcity rendering the performance of irrigation schemes often below potential. On the other hand, the scope for improving irrigated agricultural productivity remains obscure also due to the lack of spatial data on agricultural production (e.g. crop acreage and yield). To fill this gap, satellite earth observations and a replicable methodology were used to estimate crop yields at the field level for the period 2010/2014 in the Fergana Valley, Central Asia, to understand the response of agricultural productivity to factors related to the irrigation and drainage infrastructure and environment. The results showed that cropping pattern, i.e. the presence or absence of multi-annual crop rotations, and spatial diversity of crops had the most persistent effects on crop yields across observation years suggesting the need for introducing sustainable cropping systems. On the other hand, areas with a lower crop diversity or abundance of crop rotation tended to have lower crop yields, with differences of partly more than one t/ha yield. It is argued that factors related to the infrastructure, for example, the distance of farms to the next settlement or the density of roads, had a persistent effect on crop yield dynamics over time. The improvement potential of cotton and wheat yields were estimated at 5%, compared to crop yields of farms in the direct vicinity of settlements or roads. In this study it is highlighted how remotely sensed estimates of crop production in combination with geospatial technologies provide a unique perspective that, when combined with field surveys, can support planners to identify management priorities for improving regional production and/or reducing environmental impacts.  相似文献   

东天山红石金矿原生晕轴向分带研究     

陈新蔚  王世新  甘继军 《新疆地质》2013,(3)

分带性是热液矿床重要特征,也是勘查与评价热液矿床的重要方法。为建立矿床完整轴向分带模式,需有矿体不同中段的化探样品分析数据。但对于产状较陡、深部工程少的矿体,要建立较准确的原生晕分带难度较大。以新疆红石金矿L1矿体1137 m、1080 m、1000 m和900 m的样品分析数据,分别采用“格氏”、“克氏”和“重心”法计算矿床轴向分带,再利用计算结果综合确定该矿床的原生晕分带模式。勘探验证表明,确定的分带模式与实际吻合性较好,是一种有效确定分带的方法。  相似文献   

地震相分析技术在滨里海盆地AS油田沉积相分析中的应用          下载免费PDF全文

单中强  王蕴  王运海 《江苏地质》2013,37(2):333-337

针对滨里海AS地区的勘探开发目标层系,运用人工神经网络和主组分分析等技术和方法,对研究区的地震反射波形变化特征及其反映的地质特征进行识别和分类,得到地震相图,应用主要地震相单元中单井相分析成果建立地震相与沉积相的对应关系,将地震相转化为沉积相.该方法弥补了单纯用钻井资料进行沉积相划分的缺陷,提高了沉积相划分精度.  相似文献   

湖南沩山岩体多期云母的Rb-Sr同位素年龄和矿物化学组成及其成岩成矿指示意义   总被引：5，自引：5，他引：0  

丁兴  孙卫东  汪方跃  陈林丽  李秋立  陈福坤 《岩石学报》2012,28(12):3823-3840

华南分布了大量的印支期-燕山期复式花岗岩体,其成岩及相关成矿过程一直存有争议。本文选择湖南典型的花岗质复式大岩基——沩山岩体为例,通过细致研究其中多期云母的单颗粒Rb-Sr年龄及地球化学组成,探讨了它们对相关成岩成矿过程的指示意义。单颗粒云母Rb-Sr等时线定年结果显示,沩山复式花岗岩主体唐市黑云母二长花岗岩中黑云母结晶年龄为221.9±5.8Ma(MSWD=3.8),主体边部的新浦高演化花岗岩中黑云母结晶年龄为227.0±13Ma(MSWD=1.6),主体内部的巷子口二云母花岗岩中白云母结晶年龄为210.1±3.3Ma(MSWD=0.21)。电子探针主量元素及激光探针LA-ICM-MS微量元素测定结果表明,沩山复式花岗岩中黑云母或白云母的成分存在明显差异,由此指示该岩体多期岩浆的温度、氧逸度以及源岩浆成分的差异。本文研究还表明,巷子口二云母花岗岩中白云母属于次生白云母,不能用来限定岩浆源区深度及岩石成因。鉴于多期云母的成分分异趋势及指示意义,我们认为沩山复式花岗岩多期岩浆具有同源关系,均来自于同一深部大岩浆房,是在不同时期不同构造背景下经历分离结晶和/或同化混染作用侵位而成。其中,印支晚期及之后的二云母花岗岩可能最具铀矿找矿前景。  相似文献