UAV RGB,thermal infrared and multispectral imagery used to investigate the control of terrain on the spatial distribution of dryland biocrust     

Javier Blanco-Sacristán  Cinzia Panigada  Rodolfo Gentili  Giulia Tagliabue  Roberto Garzonio  M. Pilar Martín  Mónica Ladrón de Guevara  Roberto Colombo  Thomas P. F. Dowling  Micol Rossini 《地球表面变化过程与地形》2021,46(12):2466-2484

Biocrusts (topsoil communities formed by mosses, lichens, bacteria, fungi, algae, and cyanobacteria) are a key biotic component of dryland ecosystems. Whilst climate patterns control the distribution of biocrusts in drylands worldwide, terrain and soil attributes can influence biocrust distribution at landscape scale. Multi-source unmanned aerial vehicle (UAV) imagery was used to map and study biocrust ecology in a typical dryland ecosystem in central Spain. Red, green and blue (RGB) imagery was processed using structure-from-motion techniques to map terrain attributes related to microclimate and terrain stability. Multispectral imagery was used to produce accurate maps (accuracy > 80%) of dryland ecosystem components (vegetation, bare soil and biocrust composition). Finally, thermal infrared (TIR) and multispectral imagery was used to calculate the apparent thermal inertia (ATI) of soil and to evaluate how ATI was related to soil moisture (r² = 0.83). The relationship between soil properties and UAV-derived variables was first evaluated at the field plot level. Then, the maps obtained were used to explore the relationship between biocrusts and terrain attributes at ecosystem level through a redundancy analysis. The most significant variables that explain biocrust distribution are: ATI (34.4% of variance, F = 130.75; p < 0.001), Elevation (25.8%, F = 97.6; p < 0.001), and potential solar incoming radiation (PSIR) (52.9%, F = 200.1; p < 0.001). Differences were found between areas dominated by lichens and mosses. Lichen-dominated biocrusts were associated with areas with high slopes and low values of ATI, with soil characterized by a higher amount of soluble salts, and lower amount of organic carbon, total phosphorus (P_tot) and total nitrogen (N_tot). Biocrust-forming mosses dominated lower and moister areas, characterized by gentler slopes and higher values of ATI with soils with higher contents of organic carbon, P_tot and N_tot. This study shows the potential to use UAVs to improve our understanding of drylands and to evaluate the control that the terrain has on biocrust distribution.  相似文献   

Aragonite stromatolitic buildups from Santorini (Aegean Sea,Greece): Geochemical and palaeontological constraints of the caldera palaeoenvironment prior to the Minoan eruption (ca 3600 yr bp)     

Pere Anadón  Carles Canet  Walter L. Friedrich 《Sedimentology》2013,60(5):1128-1155

The pyroclastic deposits of the Minoan eruption (ca 3600 yr bp ) in Santorini contain abundant xenoliths. Most of these deposits are calcareous blocks of laminated‐botryoidal, stromatolite‐like buildups that formed in the shallow waters of the flooded pre‐Minoan caldera; they consist of (i) light laminae, of fibrous aragonite arranged perpendicular to layering, and (ii) dark laminae, with calcified filaments of probable biological origin. These microstructures are absent in the light laminae, suggesting a predominant inorganic precipitation of aragonite on substrates probably colonized by microbes. Internal cavities contain loose skeletal grains (molluscs, ostracods, foraminifera and diatoms) that comprise taxa typical of shallow marine and/or lagoon environments. Most of these forms are typical of warm water environments, although no typical taxa from hydrothermal vents have been observed. Past gasohydrothermal venting is recorded by the occurrence of barite, pyrolusite and pyrite traces. The most striking features of the stable isotopic data set are: (i) an overall wide range in δ¹³C_PDB (0·16 to 12·97‰) with a narrower variation for δ¹⁸O_PDB (?0·23 to 4·33‰); and (ii) a relatively uniform isotopic composition for the fibrous aragonite (δ¹³C = 12·40 ± 0·43‰ and δ¹⁸O = 2·42 ± 0·77‰, n = 21). The δ¹³C and δ¹⁸O values from molluscs and ostracods display a covariant trend, which reflects a mixing between sea water and a fluid influenced by volcano‐hydrothermal activity. Accordingly, ⁸⁷Sr/⁸⁶Sr from the studied carbonates (0·708758 to 0·709011 in fibrous aragonite and 0·708920 to 0·708991 in molluscs) suggests that the aragonite buildups developed in sea water under the influence of a hydrothermal/volcanic source. Significant differences in trace elements have been detected between the fibrous aragonite and modern marine aragonite cements. The caldera water from which the fibrous aragonite crusts formed received an input from a volcano‐hydrothermal system, probably producing diffuse venting of volcanogenic CO₂ gas and of a fluid enriched in Ca, Mn and Ba, and depleted in Mg and probably in Sr.  相似文献   

Fault‐related folding: Tulcumba Ridge,western New England     

G. J. H. McCall 《Australian Journal of Earth Sciences》2013,60(3):349-355

An overturned angular fold in the Currabubula Formation at Tulcumba Ridge has a north‐south axial trace exposed along the western side of this ridge. The geometry and position of this fold adjacent to the Mooki Thrust is consistent with its formation as a fault‐propagation fold involving a thrust step‐up angle of ～ 30° from a décollement. Overturned strata also occur adjacent to the Mooki Thrust near the Rocky Creek Syncline to the north and to the south on Gunnan Ridge and in the Werrie Syncline. Overturning of strata in these areas may be the result of fault‐propagation folding. It is suggested that folding in the Tamworth Belt involves thin‐skinned deformation that is dominantly fault‐related.  相似文献   

中国多金属结核西示范区的结核小尺度分布特征   总被引：1，自引：0，他引：1  

梁东红  何高文  朱克超 《海洋学报》2014,36(4):33-39

利用在中国多金属结核西示范区加密调查中获取的海底视像资料,通过水下定位数据处理和结核覆盖率计算,并结合多波束地形测量数据,从结核覆盖率分布角度对多金属结核的小尺度分布特征进行研究。研究结果表明:多金属结核分布与地形有一定的对应关系,在地形平缓区域,结核覆盖率变化较平缓,而在某些地形陡峭区域,由于块状结壳的形成,结核/结壳覆盖率出现明显的跃升;西示范区为结核高覆盖率分布区,结核覆盖率沿东西方向变化不大,由北向南呈增高趋势;地形坡度对结核分布有明显的影响,在区内0°~3.6°的坡度范围内,坡度越大,结核覆盖率越高。  相似文献   

中太平洋海山富钴结壳成矿的空间分布规律研究     

马维林  杨克红  包更生  张恺  董如洲  初凤友 《海洋学报》2014,36(7):77-89

海山是富钴结壳主要的成矿载体,结壳成矿分布不仅受到海洋最低含氧带、碳酸盐补偿深度、生物生产力、物质来源、海水氧含量等大尺度宏观因素的影响,同时也受到海山地形、沉积作用和底层海流冲刷等小尺度微观因素的控制。通过对以中太平洋R海山为主的水下结壳成矿与分布的深入研究,发现结壳富集区以海山浅水区域为主;地形地貌上的尖顶高地区、顶坡过渡带、山体鞍部、山脊、斜坡上部等区域结壳质量较好,覆盖率高;下斜坡、山谷、山顶平坦区和斜坡区平缓台地是结壳贫乏区,结壳厚度小、覆盖率也低;15°以下的小坡度地形结壳成矿较好,3°~7°最佳,15°以上的大坡度区质量有所下降,陡崖区最差。地形对结壳分布和成矿起基础性影响作用,沉积作用和底流冲刷分别起到阻滞和促进作用,海流是保持低坡度区结壳长期稳定生长的关键因素,地形控矿本质上是和底层流联合对抗沉积堆积作用的过程。  相似文献   

基于深海采矿过程的环境影响分析与管理对策建议          下载免费PDF全文

刘大海  万浏  王春娟  李成龙 《海洋科学进展》2022,40(3):367-378

深海矿产开发所产生的环境影响是目前制约深海采矿的重要问题之一,了解开发全过程的环境影响和生态响应是商业化开采的前提。本文以多金属结核、富钴结壳和多金属硫化物三种具有代表性的深海固体矿产资源为例,分析了开发前赋存环境、开发过程中及开发后的环境影响。结果表明：①不同深海固体矿产资源的分布规律、深度以及生物特征等赋存环境存在较大差异,因采矿活动带来的赋存环境改变、对环境的影响以及采矿潜在影响区域、影响时长和恢复潜力也有所不同。②多金属结核开采的环境影响着重考虑了沉积物羽流的影响,结壳开采活动从沉积物扰动、外壳去除以及栖息地改变三个方面考虑环境影响,多金属硫化物开采的环境影响还要增加对有毒物质的释放以及栖息地移除两个方面的考虑。③深海采矿对底栖生物种群的数量和物种组成皆会造成不同程度的影响。最后,从持续跟进监测评估、充实数据、提升采矿技术与设备、顶层设计与决策管理、规则制定等方面提出了环境保护与可持续发展对策建议,为深海采矿的环境影响评价及规则制定提供参考。  相似文献   

西太平洋卡罗琳洋脊CM4海山铁锰结壳矿物学和地球化学特征     

侯晓帆  王珍岩  李文建  刘凯  王青 《海洋与湖沼》2020,51(5):1118-1126

2017年8月中国科学院海洋研究所在西太平洋低纬度海区的卡罗琳洋脊CM4海山开展了多学科综合调查,发现该海山山体表面分布着大量的铁锰结壳。本文对该海山的5个铁锰结壳样品进行了矿物学和地球化学研究,利用X射线衍射(XRD)、电感耦合等离子光谱及质谱(ICP-OES、ICP-MS)等测试技术分析了铁锰结壳的矿物组成、主微量元素和稀土元素含量,并进一步探讨了铁锰结壳的成因类型。结果表明,该海山铁锰结壳的矿物组成以水羟锰矿为主,含有少量钡镁锰矿、水钠锰矿、针铁矿、纤铁矿、石英和方解石。该海山铁锰结壳的Mn、Fe、Co、Ni、Cu元素平均含量分别为24.24%、15.14%、0.16%、0.34%、0.01%。与全球各大洋海山区铁锰结壳相比,该海山样品的Cu含量很低。该海山铁锰结壳的稀土元素(REY)含量相对偏低,总体为轻稀土(LREE)富集;稀土(REY)配分模式显示相对平坦的特征,呈明显的Ce正异常,轻微的Y负异常和Ho正异常。样品的矿物组成、元素比值、元素组合等都表明该海山铁锰结壳属于水成成因,未受明显的成岩作用影响。  相似文献   

A comparison between manganese nodules and cobalt crust economics in a scenario of mutual exclusivity     

Simone Martino  Lindsay M. Parson 《Marine Policy》2012,36(3):790-800

The past 20 years have been characterised by limited interest in the economic viability of deep seabed mining with the exception of those mineral ores rich in precious metals such as polymetallic sulphides. This paper goes against the tide. After reviewing the most significant literature, it compares the economic feasibility of mining polymetallic manganese nodules and cobalt-rich ferromanganese crusts in a scenario of mutual exclusivity. It uses a new indicator, the cobalt-nickel price ratio, whose aim is to verify at what metal prices the net present value of the two mining projects equalises. Previous research has shown that the turning margin between manganese nodules and cobalt crusts is a cobalt price of $50/kg. The present paper revises this by showing that the choice between mining crust and nodules depends on fluctuations in the price of nickel. A Monte Carlo simulation proves that cobalt crust mining could be reasonably preferred to manganese nodules at cobalt prices of $40-60/kg if the price of nickel fell below $11/kg. Within this condition, investors would receive the minimum acceptable internal rate of return of 15%, which is at a level of risk closer to the land-based mining. However, when the price of nickel passes the $11/kg threshold, the equilibrium between the two ventures can be reached only at a cobalt price greater than $100/kg, causing cobalt crust to become uncompetitive. Finally, the paper, recognising that prices are not unique drivers, introduces legal, political, technological and environmental concerns to show that the final choice between the two mining ventures cannot be merely driven by economic issues.  相似文献   

Geoacoustic Inversion via Genetic Algorithm and Its Application to Manganese Sediment Identification     

Woojae Seong  Cheolsoo Park 《Marine Georesources & Geotechnology》2013,31(1):37-50

Abstract

An acoustic inversion method using a wide-band signal and two near field receivers is proposed and applied to multiple layered seabed models including a manganese sediment. The inversion problem can be formulated into a probabilistic model comprised of signals, a forward model, and additive noise. The forward model simulates wide-band signals, such as chirp signals, and is chosen to be the source-wavelet-convolution plane wave modeling method. The wavelet matching technique, using weighted least-squares fitting, estimates the sediment sound-speed and thickness on which determination of the possible numerical ranges for a priori uniform distribution is based. The genetic algorithm is applied to a global optimization problem to find a maximum a posteriori solution for determined a priori search space. Here the object function is defined by an L₂ norm of the difference between measured and modeled signals. Not only the marginal pdf but also its statistics are calculated by numerical evaluation of integrals using the samples selected during importance sampling process of the genetic algorithm.  相似文献   

Deep-Sea Nodules and Co-rich Mn Crusts     

G. P. Glasby  Zhilei Sun 《Marine Georesources & Geotechnology》2013,31(1):72-78

The mining of deep-sea manganese nodules has been a topic of interest since J.L. Mero undertook his preliminary studies in the 1960s to evaluate the prospects for mining deep-sea nodules. Despite the great deal of investment in deep-sea mining over more than 40 years, there has still been no successful attempt to mine the deep-sea nodules on a commercial scale. One of the major problems is that the nodules cannot be brought to the surface with the necessary amounts of recoverable nickel, cobalt and zinc to warrant the initial high investment necessary for this operation. It therefore appears that in the short term, deep-sea manganese and Co-rich Mn crusts will not be mined on a commercial scale in the foreseeable future. Nonetheless, investigations of deep-sea mineral deposits by a number of nations will continue and enable us to understand the deep-sea environment in increasing detail, which is necessary in view of the great extent of the deep oceans which cover an area of about 66% of the Earth's surface.  相似文献