Macrofauna along the Sudanese Red Sea coast: potential effect of mangrove clearance on community and trophic structure          下载免费PDF全文

Rasha A. O. Sabeel  Jeroen Ingels  Ellen Pape  Ann Vanreusel 《Marine Ecology》2015,36(3):794-809

Mangroves along the Sudanese Red Sea coast are under constant anthropogenic pressure. To better understand the influence of mangrove clearance on the intertidal benthic community, we investigated the composition, biodiversity and standing stock of the macrofauna communities at high‐, mid‐ and low‐water levels in three contrasting habitats: a bare sand flat, a cleared mangrove and an intact mangrove. In addition, a community‐wide metric approach based on taxon‐specific carbon and nitrogen isotope values was used to compare the trophic structure between the three habitats. The habitats differed significantly in terms of macrofaunal standing stock, community composition and trophic structure. The high‐ and mid‐water levels of the intact mangroves showed a distinct macrofaunal community characterized by elevated densities and biomass, largely governed by higher decapod and gastropod abundances. Diversity was similar for cleared and intact mangroves, but much lower for the bare sand flat. Community‐wide metrics indicated highest trophic diversity and community niche breadth in the intact mangroves. Differences between the cleared and intact mangroves can be partly attributed to differences in sediment characteristics resulting from mangrove clearance. These results suggest a significant impact of mangrove clearance on the macrofaunal community and trophic structure. This study calls for further investigations and management actions to protect and restore these habitats, and ensure the survival of this ecologically valuable coastal ecosystem.  相似文献   

Effects of differing coverage of moss‐dominated soil crusts on hydrological processes and implications for disturbance in the Mu Us Sandland,China          下载免费PDF全文

Yongsheng Yang  Chongfeng Bu  Xingmin Mu  Kankan Zhang 《水文研究》2015,29(14):3112-3123

To study the effects of biological soil crusts (BSCs) on hydrological processes and their implications for disturbance in the Mu Us Sandland, the water infiltration, evaporation and soil moisture of high coverage (100% BSCs), middle coverage (40% BSCs) and low coverage (0% BSCs, bare sand) of moss‐dominated crusts were conducted in this study, respectively. The conclusions are as follows: (1) the main effects of moss‐dominated crusts in the Mu Us Sandland on the infiltration of rainwater were to reduce the infiltration depths and to retain the limited rainwater in shallow soil; (2) moss‐dominated crusts have no significant effects on daily evaporation when the volumetric water content at 4 cm depth in 100% BSCs (VWC4) was over 24.7%, on enhanced daily evaporation when the VWC4 ranged from 6.5% to 24.7% and on reduced daily evaporation when the VWC4 was less than 6.5%; and (3) decreasing the coverage of moss‐dominated crusts (from 100% to 40%) did not significantly change its effects on infiltration, evaporation and soil moisture. Our results demonstrated that for the growth and regeneration of shrubs, which were dominated by Artemisia ordosica in the Mu Us Sandland, high coverage of moss‐dominated crusts has negative effects on hydrological processes, and these negative effects could not be significantly reduced by decreasing the coverage of moss‐dominated crusts from 100% to 40%. Therefore, for the sustained and healthy development of shrub communities in the Mu Us Sandland, it is necessary to take appropriate measures for the well‐developed BSCs in the sites with high vegetation coverage in the rainy season. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Are peatlands in different states with respect to their thermodynamic behaviour? A simple test of peatland energy and entropy budgets     

Fred Worrall  Ross Morrison  Chris Evans  Joerg Kaduk  Susan Page  Alex Cumming  Mark Rayment  Nicholas Kettridge 《水文研究》2021,35(12):e14431

Whilst all ecosystems must obey the second law of thermodynamics, these physical bounds and controls on ecosystem evolution and development are largely ignored across the ecohydrological literature. To unravel the importance of these underlying restraints on ecosystem form and function, and their power to inform our scientific understanding, we have calculated the entropy budget of a range of peat ecosystems. We hypothesize that less disturbed peatlands are ‘near equilibrium’ with respect to the second law of thermodynamics and thus respond to change by minimizing entropy production. This ‘near equilibrium’ state is best achieved by limiting evaporative losses. Alternatively, peatlands ‘far-from-equilibrium’ respond to a change in energy inputs by maximizing entropy production which is best achieved by increasing evapotranspiration. To test these alternatives this study examined the energy balance time series from seven peatlands across a disturbance gradient. We estimate the entropy budgets for each and determine how a change in net radiation (ΔR_n) was transferred to a change in latent heat flux (ΔλE). The study showed that: (i) The transfer of net radiation to latent heat differed significantly between peatlands. One group transferred up to 64% of the change in net radiation to a change in latent heat flux, while the second transferred as little as 27%. (ii) Sites that transferred the most energy to latent heat flux were those that produced the greatest entropy. The study shows that an ecosystem could be ‘near equilibrium’ rather than ‘far from equilibrium’.  相似文献   

新疆天山地区的波速比异常分析     

张琳琳  高朝军 《中国地震研究》2017,31(1):39-50

Based on the seismic observation report data provided by the Xinjiang Digital Seismic Network from 2009 to 2014,we calculate the wave velocity ratio and its background value for medium and small earthquakes by using the multi-station method in Tianshan,Xinjiang.This paper analyzes the variation of the wave velocity ratio disturbance value to highlight the abnormal,and also back-traces 7 moderate earthquakes at the research area.The results show that:(1)the background value of the wave velocity ratio is almost 1.70,the wave velocity ratio obviously decreases in the middle-eastern part of Tianshan and the region near the Puchang fault;(2)the wave velocity ratio disturbance value is mostly low in the epicenter before four earthquakes of M≥5.0 from 2011 to 2013 in the study area;(3)before 7 moderate strong earthquakes,the earthquake events with low value of the wave velocity ratio account for over 60% of corresponding total events near the epicenters,and the low value of the wave velocity ratio is relatively obvious before moderate earthquakes.  相似文献   

成灌高铁运行对成都地磁台观测数据干扰测试     

钟李彬  林建  李雪浩  胡俊明  李国超  颜晓晔 《地震地磁观测与研究》2017,38(5):81-85

成都地磁台距成灌高铁运行线路垂直距离约1.5 km,使用数字化磁通门磁力仪GM4,在轨道沿线不同距离处进行野外测试。测试结果表明,轨道交通的运行对周围地磁观测环境产生干扰,干扰距离约6 km,干扰主要来自轨道泄露电流及输电线路产生的磁场。  相似文献   

河北省及邻区数字电扰动干扰分析   总被引：1，自引：1，他引：0  

乔子云  罗娜  贾立峰  寇海川  牛淑瑜  茅远哲 《地震地磁观测与研究》2017,38(4):158-164

通过对河北省及邻区数字电扰动观测资料进行分析和环境调查,发现主要干扰因素为供电或漏电干扰。如:昌黎地震台地电阻率整点测量受到供电干扰,三河地震台受到恒远自动化仪表厂工作时段供电干扰,高碑店地震台受到商场大型设备供电干扰,广平地震台受到UPS交流电源漏电干扰,昌平地震台受到地铁运行漏电干扰等。电扰动干扰形态相似,均为超过本底值几倍、数十倍乃至上百倍的高值脉冲变化。  相似文献   

Effects of different types of mechanical disturbances on a charophyte dominated macrophyte community     

Kaire Torn  Georg MartinJonne Kotta  Maarit Kupp 《Estuarine, Coastal and Shelf Science》2010

Charophytes are unique and endangered macroalgae. Mechanical stress is known to damage charophyte communities, however, virtually nothing is known how such disturbance affect seasonal succession and recovery of charophyte communities. We examined the response of a shallow water charophyte community to different types and timing of disturbances by conducting seasonal in situ field experiment in a brackish water ecosystem. The disturbances associated with mechanical removal of vegetation or sediment had the largest impact on the charophyte community. Disturbances that only partly damaged the plants had minor effects and communities were characterized by fast recovery. The timing of disturbance had significant effects on the charophyte community with stronger effects when disturbed at the early stage compared to mid-stage of seasonal succession.  相似文献   

Developing millennial tree ring chronologies in the fire‐prone North American boreal forest     

DOMINIQUE ARSENEAULT  BENJAMIN DY  FABIO GENNARETTI  JULIA AUTIN  YVES BÉGIN 《第四纪科学杂志》2013,28(3):283-292

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Changes in Venice Lagoon dynamics due to construction of mobile barriers     

Michol Ghezzo  Stefano Guerzoni  Andrea Cucco  Georg Umgiesser 《Coastal Engineering》2010

The MoSE project (construction of mobile barrier to safeguard the Lagoon of Venice) entails changes to the structure of the lagoon's inlets. This could have consequences for the areas near the inlets and for the dynamics of the lagoon ecosystem as a whole. In order to predict the effects of the proposed alterations on the hydrodynamics of the lagoon, a well-tested hydrodynamic-dispersion model was applied. Simulations were carried out considering both idealised and realistic tide and wind scenarios.  相似文献   

The concept of ecological succession applied to phytoplankton over four consecutive years in five ponds featuring a salinity gradient     

Hajer Khemakhem  Jannet Elloumi  Mahmoud Moussa  Lotfi Aleya  Habib Ayadi 《Estuarine, Coastal and Shelf Science》2010

The distribution of phytoplankton abundance, biomass and species composition coupled with environmental factors and metazooplankton was studied relatively intensively and over a period of four consecutive years in five ponds featuring a gradient of increasing salinity from near to that of sea water to a nine-fold concentration from 2000 to 2003. The results indicate that the physical characteristics of the water (temperature and salinity) were quite similar over the years. Nutrients, which were concentrated in pond A1, decreased with increases in salt concentration. The composition of the phytoplankton community showed strong seasonality. Diatoms dominated in the first ponds A1, A16 and C2-1, followed by dinoflagellates. Chlorophyceae dominated the phytoplankton community in the hypersaline ponds M2 and TS. Cyanobacteriae were relatively abundant in ponds M2 and TS. The highest phytoplankton density and biomass were found in the ponds with the highest salinity due to the proliferation of Dunaliella salina (Chlorophyta: Volvocales). The inter-annual study of phytoplankton succession in the Sfax solar salterns showed slight differences among the years of study due to the stability of the environmental conditions. Phytoplankton communities were permanently primitive, stage 1 – structured as they failed to build complexity because of salt stress which operates for longer and above any other variables. This reduced frequency of disturbance to the existing course of regulation, allowed the community to “mature” from its “primitive” state, rather than experience frequent structural setbacks.  相似文献