共查询到20条相似文献，搜索用时 23 毫秒
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Agatova A. I. Lapina N. M. Torgunova N. I. Sapozhnikov V. V. Milovskaya L. V. 《Water Resources》2004,31(6):639-648
The concentration of dissolved and particulate organic matter (OM) in Lakes Kuril'skoe and Azabach'e is shown to depend on the rate of its production by phytoplankton (and by macrophytes in Lake Azabach'e) and on the amount of allochthonous OM delivered by rivers. The rate of OM transformation in the production–destruction cycle and the regeneration of phosphates were evaluated based on the activities of redox enzymes of the electron-transport system and the hydrolytic enzymes of alkaline phosphatase and protease. The intense assimilation of allochthonous OM in lake ecosystems was found to take place due to active hydrolytic disintegration of the arriving OM. 相似文献
3.
Currently, the weakened connectivity of wetland ecosystems is the most important factor leading to the destruction, degradation, and disappearance of wetlands. Studying changes in wetland ecosystems connectivity enables the understanding the hydrological processes in wetland ecosystems and provides significant support for the study of ecological water demand. However, recent research on the connectivity of wetland ecosystems has primarily focused on intuitive Heilongjiang River Basin in China (HRBC) connectivity in terms of hydrology and geomorphology, while the impact of wetland ecosystems on habitats has been ignored. The present study applied an innovative method to evaluate and regulate the stereoscopic spatial connectivity (SSC) of the wetland ecosystems in the HRBC. In this method, the water requirements of typical organisms in the region were considered, and the hydrological trends in the wetland ecosystems along with the status of the SSC were analysed using remote sensing images. A regulation mode for improving the stereoscopic spatial connectivity index (SSCI) was proposed. The results revealed that over the past 35 years, the wetland ecosystems in the study area shrank significantly, with the SSCI decreasing from 41.30% in 1980 to 35.08% in 2015. By comparing the correlations among temperature, precipitation, agricultural land, construction land, and the wetland ecosystems during the same period, it was proven that human activity serves as the major driving force behind the observed loss of wetlands in the system. Subsequently, the key protected areas needing protection to maintain the SSC of the wetland ecosystems were clarified, and the key recovery areas were determined based on three scenarios featuring high, medium, and low feasibility, which greatly improved the SSCI and generalization route after regulation. In general, the proposed SSC evaluation and regulation method is widely applicable to all kinds of wetland ecosystems located on animal habitat and migration routes, which can fully reflect the ecological effects of wetland ecosystems, and this method has certain reference significance for the evaluation and regulation of wetland ecosystems in other regions. 相似文献
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Petrooshina M 《Marine pollution bulletin》2003,47(1-6):187-192
The purpose of this investigation is to study structure, evolution and present ecological state of background and anthropogenically modified landscapes of the Abrau Peninsula. This region has been recommended as one of the main conservation sites on the Russian Black Sea coast due to its relatively low anthropogenic transformation and its historical importance. The ecological situation is aggravated today by the construction of a pipe-line and oil terminal near Novorossiysk and by an increase in unregulated recreation activity within the peninsula's narrow coastal zone. A special landscape-ecological map has been compiled for the model area. All ecosystems shown on the map can be grouped into four main categories based on changes of landscape structure resulting from direct impact of human activity and indirect impact mainly from chemical pollution. Ecosystems exhibiting a high degree of transformation are more typical for regions characterized by settlements, vineyards and the coastal recreation zone. Ecosystems with moderate changes also exist in the coastal area, including, for example, some unique ecosystems with pine-tree forests, pistachio-juniper and juniper open-lands. Nearly 50% of pine-tree (Pinus pithyusa) forests are in the fourth and fifth stages of recreation degradation. Some protection measures are suggested to maintain biodiversity and sustainable development of these coastal landscapes and to improve their current condition. 相似文献
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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 (ΔRn) 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
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The geophysical, thermodynamic and dielectric properties of snow are important state variables that are known to be sensitive to Arctic climate variability and change. Given recent observations of changes in the Arctic physical system (Arctic Climate Impact Assessment, 2004), it is important to focus on the processes that give rise to variability in the horizontal, vertical and temporal dimensions of the life‐history of snow on sea ice. The objectives in this study are to present these ‘state’ variables and to investigate the processes that govern variability in the vertical, horizontal and temporal dimension by using a case study over land‐fast first‐year sea ice for the period December 2003 to June 2004. Results from two sampling areas (thin and thick snowpacks) show that differences in snowpack thickness can substantially change the vertical and temporal evolution of snow properties. During the late fall and early winter (cooling period) we measured no significant changes in the physical properties, except for thin snow‐cover salinity, which decreased throughout the period. Fall‐snow desalination was only observed under thin snowpacks with a rate of ?0·12 ppt day?1. Significant changes occurred in the late winter and early spring (warming period), especially for snow grain size. Snow grain kinetic growth of 0·25–0·48 mm·day?1 was measured coincidently with increasing salinity and wetness for both thin and thick snowpacks. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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A. N. Chetyrbotskii 《Water Resources》2008,35(4):397-407
The problems of parametric representation of the initial formation and the subsequent evolution of fast ice in freezing seas are discussed within the framework of the model of marine ice cover evolution. The mathematical form of this representation takes into account the processes of transformation of sea ice formations in open water areas in coastal regions into fast ice during its formation and inverse processes at the stage of its destruction. The parametric identification of the model was based on samples of long-term distributions of ice cover characteristics in the Sea of Japan, as well as the distributions of air temperature and wind speeds over sea water area. The model can be used to predict the state of fast ice in the ice cover of the Sea of Japan. 相似文献
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Discussion on the relationship between the Yanshanian Movement and cratonic destruction in North China 总被引：3，自引：0，他引：3
The relationship between the Yanshanian Movement, destruction of the North China Craton(NCC), and subduction of the western Pacific plate is crucial to reconstructing the middle-late Mesozoic tectonic evolution of the eastern Asian continent and margin. The Yanshanian Movement was a globally important change in crustal tectonics during the Middle-Late Jurassic.Previous research has systematically studied the formation and evolution of the Yanshanian Movement, focusing on the timing and location of tectonic movements, and the sedimentary and volcanic strata. However, the question of whether the tectonic activity occurred globally, and the characteristics of the Yanshanian Movement remain debated. The main argument is that if a tectonic movement can only be characterized by a regional or local disconformity, and if the tectonic movement occurred in an intracontinental setting, with extensive deformation but with no disconformity despite volcanic eruptions and magmatic intrusions, accompanied by changes in crustal structure and composition, should it be defined as a tectonic event or process? This question requires further analysis. The main aim of this study is to distinguish whether the Yanshanian Movement is a local feature of the eastern Asian continent, or a global tectonic event related to subduction of the Pacific Plate. In this paper, based on previous research, we discuss the spatial and temporal evolution of the Yanshanian Movement, the controlling tectonic mechanisms, and its relationship to the reactivation and destruction of the NCC and the subduction of the western Paleo-Pacific slab.We emphasize that the Yanshanian Movement in the Middle-Late Jurassic is distinct from the lithospheric thinning responsible for Early Cretaceous extension and magmatism related to the destruction of the NCC. The various tectonic stages were constrained by different dynamics and tectonic settings, or by different tectonic events and processes. Therefore, it is possible that the deformation and reactivation of the NCC contributed to its destruction, in addition to lithospheric thinning. Finally, we discuss whether the Yanshanian Movement was associated with the destruction of the NCC. 相似文献
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Natural ecosystems in the region of the lower Tarim River in northwestern China strongly deteriorated since the 1950s due to an expanding desertification. As a result, the downstream Tarim River reaches became permanently dry land. This historical evolution in land‐use change is typically the result of the anthropogenic impact on natural ecosystems. On the basis of a spatially distributed hydrological catchment model bidirectionally linked with a fully hydrodynamic MIKE11 river model, land‐use changes characterized by historical changes in leaf area index (LAI) of vegetation, as well as the evolution of irrigated surface areas, can be causally related to changes in water resources (groundwater storage and surface water resources). An increased surface area of irrigated (agricultural) land, together with a majority of inefficient irrigation methods, did lead to a strong increase of water resources consumption of the farmlands located in the upper Tarim River area. Evidently, this evolution influenced available water resources downstream in the Tarim basin. As a result, farmland has been gradually relocated to the upstream regions. This has led to reduced flows from the upper Tarim stream, which subsequently accelerated the dropping of the groundwater level downstream in the basin. This study moreover demonstrates that land surface biomass changes (cumulative LAI) along the lower Tarim River are strongly related to the changes in groundwater storage. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
10.
湍流输送是一种热力学不可逆过程,本文利用非线性热力学研究了湍流输送的特征. 将热力学流对热力学力以平衡态作为参考态进行Taylor展开,可以得到湍流输送系数是系统宏观参量梯度的Taylor级数. 线性湍流输送系数是Reynolds湍流闭合方案的K闭合湍流输送系数;而湍流输送系数非线性项则是系统偏离热力学平衡态所造成的热力学非线性效应. 湍流输送系数这一热力学性质提供了一种热力学湍流闭合方案. 线性湍流输送系数是正定的,湍流输送只能使系统宏观参量均匀化;而在远离平衡态的热力学非线性区,可能导致湍流输送系数负黏性现象. 在最小熵产生态的条件下,热力学流对热力学力Taylor展开的各级系数间存在一种递推关系. 利用这种递推关系大大减少了由实验确定的Taylor级数的系数个数. 相似文献
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On the biogeochemical response of a glacierized High Arctic watershed to climate change: revealing patterns,processes and heterogeneity among micro‐catchments 
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下载免费PDF全文 Our novel study examines landscape biogeochemical evolution following deglaciation and permafrost change in Svalbard by looking at the productivity of various micro‐catchments existing within one watershed. It also sheds light on how moraine, talus and soil environments contribute to solute export from the entire watershed into the downstream marine ecosystem. We find that solute dynamics in different micro‐catchments are sensitive to abiotic factors such as runoff volume, water temperature, geology, geomorphological controls upon hydrological flowpaths and landscape evolution following sea level and glacial changes. Biotic factors influence the anionic composition of runoff because of the importance of microbial SO42? and NO3? production. The legacy of glaciation and its impact upon sea level changes is shown to influence local hydrochemistry, allowing Cl? to be used as a tracer of thawing permafrost that has marine origins. However, we show that a ‘glacial signal’ dominates solute export from the watershed. Therefore, although climatically driven change in the proglacial area has an influence on local ecosystems, the biogeochemical response of the entire watershed is dominated by glacially derived products of rapid chemical weathering. Consequently, only the study of micro‐catchments existing within watersheds can uncover the landscape response to contemporary climate change. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Wei-Yu Chen Yun-Ru Ju Chia-Jung Lin Jeng-Wei Tsai Szu-Cheih Chen Chung-Min Liao 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(6):1545-1555
Environmental change not only undergoes in mean environmental conditions but also in their degree of stochasticity. Changes in waterborne metal variability are often associated with altered disturbance regimes and temporal patterns of source availability. Here copper (Cu) was used as an example because Cu sulfate (CuSO4) has been extensively used as a chemical tool to exterminate phytoplankton for controlling skin lesions and gill disease of fish in aquatic ecosystems. This study showed that increased variability of waterborne Cu concentrations strongly promotes a key process of biokinetics, bioaccumulation. In experimental tilapia populations, the mean growth cost coefficient in pulsed Cu exposures was 7 % lower than the control group. On the other hand, the double-pulse, constant low, and single-pulse scenarios had similar effect on biomass change (2.2–2.4 %). The greatest biomass change (~10 %) occurred where Cu concentrations were gradually increasing over time or at a constant high rate. Most importantly, this study demonstrated that chronic exposure of tilapia to a low Cu concentration rate that approximated a single large pulse of field-realistic levels damaged bioenergetic mechanisms and increased energy acquisition. This study also showed that interactions across multiple pulsed or fluctuating Cu exposures were involved in accumulation changes that could also be achieved by controlling pulse timing and duration. It can be concluded that increased metal variability can promote biokinetic and bioenergetic responses in fish; and that changes in environmental variability may interact with other global change processes and thereby substantially accelerate change in aquatic ecosystems. 相似文献
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对琼北地区确定性井下人工爆破和天然地震事件波形特征进行梳理,分析人工爆破与天然地震波不同判据特征。结果表明:P波初动方向、振幅比是识别人工爆破和天然地震的2个主要判据;尾波持续时间、S波最大振幅与持续时间比可作为识别人工爆破和天然地震的一般判据;发震时间可根据事件的强度、规律性,并结合其他判据,仅作为识别过程中的参考因素。 相似文献
14.
Vertical wells with radial extension at the well bottom can improve the rate of water production. No study has yet investigated the effects of the transient state and anisotropy in directional hydraulic conductivities on the wellbore flux rate for this type of well. This study derives a semianalytical transient drawdown solution for constant-head pumping at a fully penetrating well radially extended at the bottom of a confined, anisotropic aquifer by applying Laplace transform and separation of variables as well as conducting a Fourier analysis. The results of this new solution indicate that transient and steady-state wellbore flux rates can be increased by a factor of two for greater radial extension of the well. Compared with an isotropic aquifer (a ratio of vertical and horizontal hydraulic conductivities equal to one), an anisotropic aquifer with the ratio less than one may produce a higher transient wellbore flux rate and lower steady-state wellbore flux rate. Moreover, the time required to achieve the steady-state wellbore flux rate can be substantially affected by anisotropy of the aquifer. 相似文献
15.
水温、光能对春季太湖藻类生长的耦合影响 总被引：5，自引：2，他引：3
环境因素对藻类生长的影响机制是探讨蓝藻水华暴发的基础,其中水温和光能均是影响藻类生长的关键物理因子.基于2015年春季于太湖观测的11次藻类总初级生产力、水温廓线和营养盐浓度等,探讨水温、光能及营养盐对藻类生长过程的影响.结果表明:春季,水温、光能是影响藻类生长的关键因素,而营养盐的影响贡献相对较弱.深层水体中光能是藻类生长的关键性限制因子,浅层表现为水温、光能的共同影响,而表层主要表现为光能的抑制.水温的升高促进藻类对光能的获取和利用,提高光抑制的光能阈值,造成深层水体中光能限制程度的加强,藻类生长呈现光限制的深度变浅.本研究有利于确定气候变化下水生生态系统演变的方向,为水生生态系统的恢复提供理论依据. 相似文献
16.
The results of studying the hydrocarbon composition of organogenic bottom sediments of oil-polluted lakes and lakes of similar types remote from centers of anthropogenic activity are given. To correctly assess the oil pollution of organogenic materials one has to take into account the presence of native hydrocarbons in their composition and to choose the main criterion of oil pollution based on the presence of specific oil components not characteristic of aquatic ecosystems in their natural state. The most promising among such components are alkylbenzenes С15–С25, which slowly degrade under the conditions typical of northern aquatic ecosystems and can be retained for a long time by organogenic matrix. 相似文献
17.
湖泊生态系统的修复必须建立在历史生态环境演化过程与驱动机制认识的基础之上.针对草型湖泊演化历史研究相对不足的现状,以长江中游典型草型湖泊梁子湖为研究对象,结合210Pb和137Cs年代测试,通过对沉积柱高分辨率的多指标分析(硅藻、元素地球化学和粒度)以及流域历史资料重建近百年来梁子湖生态环境的演化过程,并在此基础上利用冗余分析定量区分影响该湖泊生态环境演化的关键驱动因子.结果显示,沉积物总磷和重金属元素Cu是影响该湖泊生态环境演化的2个显著变量,它们分别单独解释硅藻组合的12.7%和8.5%变率.这表明近百年来人类活动引起的营养输入对梁子湖生态环境演化起关键性作用,而重金属污染也是影响梁子湖环境演变的重要因子.本研究结果可以为梁子湖及长江中下游其他类似湖泊的环境治理提供科学依据. 相似文献
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2022年9月5日四川泸定发生M6.8地震,为研究泸定地震孕震区的应力变化,选取b值、小震调制比和丛集率这3个参数,对泸定地震前的区域地震活动状态进行计算研究。结果显示:泸定及周边区域几次强震发生前,区域地震活动均存在持续时间较长的低b值时段,且在低b值状态下震前短期内出现小震高丛集、高调制比的现象;鲜水河断裂带的地震活动状态分析显示,此次泸定地震前该断裂带存在持续时间近10个月的低b值状态,且短期内出现丛集率升高、调制比高值现象。通过对比分析,认为泸定地震是鲜水河断裂带构造运动的结果。综合分析认为,结合应力场背景和构造条件研究地震活动b值、固体潮调制比和丛集率的时空变化有助于理解大地震的孕育演化过程。 相似文献
19.
During the implementation of the Belt and Road Initiative(BRI), simulating the change trends of terrestrial ecosystems in Eurasia under different climate scenarios is a key ecological issue. The HLZ ecosystem model was improved to simulate the changes in the spatial distribution and types of terrestrial ecosystems in Eurasia based on the climate data from Eurasian meteorological stations from 1981 to 2010 and the data from the RCP26, RCP45 and RCP85 scenarios released by CMIP5 from 2010 to 2100. Ecological diversity and patch connectivity index models were used to quantitatively calculate the future changes in ecological diversity and patch connectivity of terrestrial ecosystems in Eurasia. The results show that(1) cold temperate wet forest, cool temperate moist forest and desert are the major terrestrial ecosystem types and cover 36.71% of the total area of Eurasia.(2) Under all three scenarios, the polar/nival area would shrink more than other terrestrial ecosystem types and would decrease by 26.75 million km2 per decade on average, and the subpolar/alpine moist tundra would have the fastest decreasing rate of 10.49% per decade on average from 2010 to 2100.(3) Under the RCP85 scenario, the rate of terrestrial ecosystem changes will be greater than that under the other two scenarios, and the subpolar/alpine moist tundra would exhibit the fastest decreasing rate of 10.88% per decade from 2010 to 2100.(4) The ecological diversity would generally show decreasing trends and decrease by 0.09%, 0.13% and 0.16% per decade on average under the RCP26, RCP45 and RCP85 scenarios,respectively.(5) The patch connectivity would first increase and then decrease under all three scenarios. In general, the trends of the changes in terrestrial ecosystems would show an obvious difference in the different regions throughout the BRI area. 相似文献
20.
In this article we craft process‐specific algorithms that capture climate control of hillslope evolution in order to elucidate the legacy of past climate on present critical zone architecture and topography. Models of hillslope evolution traditionally comprise rock detachment into the mobile layer, mobile regolith transport, and a channel incision or aggradation boundary condition. We extend this system into the deep critical zone by considering a weathering damage zone below the mobile regolith in which rock strength is diminished; the degree of damage conditions the rate of mobile regolith production. We first discuss generic damage profiles in which appropriate length and damage scales govern profile shapes, and examine their dependence upon exhumation rate. We then introduce climate control through the example of rock damage by frost‐generated crack growth. We augment existing frost cracking models by incorporating damage rate limitations for long transport distances for water to the freezing front. Finally we link the frost cracking damage model, a mobile regolith production rule in which rock entrainment is conditioned by the damage state of the rock, and a frost creep transport model, to examine the evolution of an interfluve under oscillating climate. Aspect‐related differences in mean annual surface temperatures result in differences in bedrock damage rate and mobile regolith transport efficiency, which in turn lead to asymmetries in critical zone architecture and hillslope form (divide migration). In a quasi‐steady state hillslope, the lowering rate is uniform, and the damage profile is better developed on north‐facing slopes where the frost damage process is most intense. Because the residence times of mobile regolith and weathered bedrock in such landscapes are on the order of 10 to 100 ka, climate cycles over similar timescales result in modulation of transport and damage efficiencies. These lead to temporal variation in mobile regolith thickness, and to corresponding changes in sediment delivery to bounding streams. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献