Linking atmospheric circulation to daily precipitation patterns over the territory of Bulgaria

An eight states non-homogeneous hidden Markov model is developed for linking daily precipitation amounts data at a network of 32 stations broadly covering the territory of Bulgaria to large-scale atmospheric patterns. At each site a 40-year record 1960?C2000 of daily October?CMarch precipitation amounts is modeled. The atmospheric data consists of daily sea-level pressure, geopotential height at 500 and 850?hPa, air temperature at 850?hPa and relative humidity at 700 and 850?hPa on a 2.5?×?2.5 grid based on NCEP-NCAR reanalysis data set covering the Europe-Atlantic sector 30W?C60E, 20N?C70N for the same period. The first 30?years data are used for model fitting purposes while the remaining 10?years are used for model evaluation. Detailed model validation is carried out on various aspects. The proposed model reproduces well the rainfall statistics for the observed and reserved data whereas the identified states are found to be physically interpretable in terms of regional climatology.     

Movement patterns of the limpet Cellana grata (Gould) observed over a continuous period through a changing tidal regime

Time-lapse videography of limpets mounted with light-emitting diodes was used to monitor the movements of a population of the non-homing Cellana grata on a vertical gully wall in Hong Kong. Animals were monitored for >7 days to examine spatial and temporal variation in their behaviour as the tides transited from a semi-diurnal to an almost diurnal pattern. Movement was synchronised with the tides, irrespective of the day–night cycles. Limpets rested low on the shore and were stimulated to move by the rising tide. Individuals moved up shore with the flooding tide, maintaining themselves in the awash zone, and then down shore on the ebbing tide, until they reached a resting height when the tide then fell beneath them, exhibiting ‘zonal shuttling’. A tight coupling of limpet position to tide height persisted through the changing tidal pattern, and almost all animals displayed the same organisation of activity over all tides. Initiation of activity and maximum height reached were probably controlled by the tides, but the cessation of activity may have been controlled by an internal clock. The pattern observed is consistent with the threat of attack from aquatic predators coupled with the need to minimise physical stresses while exposed. It is also consistent with the avoidance of grazing lower on the shore where interspecific competition may be more intense. Limpets showed two peaks of activity per tide, corresponding to when the rate of change of tide height was the greatest, except when tides became much reduced during the transit to a diurnal pattern. Movement was triphasic: an initial rapid phase, followed by a slower phase in the high shore and then a rapid phase before the limpets stopped moving. This structure is common in limpets and in this case is likely to be a consequence of animals maintaining themselves within the awash zone. Tide height appears to determine foraging activity, but with modifications in the behaviour in response to factors operating at more local temporal and spatial scales.     

Size-specific changes in amount of lipid and daily growth rate of early larval sardine, Sardinops melanostictus, in the main Kuroshio Current and its offshore waters off eastern Japan

The size-specific nutritional conditions of larval sardines, Sardinops melanostictus, from the main Kuroshio Current and its offshore waters off eastern Japan were assessed by lipid analysis. A rapid lipid analysis technique (diagnostic kits for human serum lipids) was used to measure the different lipid components of individual sardine larvae as indicators of their nutritional condition. Size-specific growth trajectories of individual larvae were estimated by the biological intercept method, and the recent daily growth rate of standard length (SL) was calculated from the 3 d outer increment width on the otolith. Relationships between the amount of larval phospholipid (PL; tissue weight indicator) and SL, and the recent daily growth rate of larva (Gr) and SL, could be expressed by the equations PL = 0.459 SL ^1.77 and Gr = 0.0809 SL − 0.341, respectively. There was no notable difference in these values between the two survey areas. The relationship between the amount of triglyceride (TG) and SL could be expressed allometrically (TG = 0.013 SL ^2.63). The relationship between the index of starvation tolerance (TG/PL) and SL could be expressed by the allometric equation TG/PL = 0.0288 SL ^0.865, suggesting that larger sardine have a higher starvation tolerance than smaller sardine. The TG of the 8 to 9 mm SL size-class larvae in the offshore area was higher than in the main Kuroshio Current. To test whether the TG for each larval sardine in the 8 to 9 mm SL size-class could be correlated with variables (temperature, chlorophyll a and distribution density of the sardine larvae) measured at the sampling stations, correlation analyses were performed. A highly significant negative correlation between TG and distribution density of the sardine larvae was found. A density-dependence effect seemed to influence the fluctuation of the larval storage energy component for short-term needs. Received: 12 March 1998 / Accepted: 26 March 1999     

Modeling patterns of nonlinearity in ecosystem responses to temperature, CO2, and precipitation changes.

It is commonly acknowledged that ecosystem responses to global climate change are nonlinear. However, patterns of the nonlinearity have not been well characterized on ecosystem carbon and water processes. We used a terrestrial ecosystem (TECO) model to examine nonlinear patterns of ecosystem responses to changes in temperature, CO2, and precipitation individually or in combination. The TECO model was calibrated against experimental data obtained from a grassland ecosystem in the central United States and ran for 100 years with gradual change at 252 different scenarios. We primarily used the 100th-year results to explore nonlinearity of ecosystem responses. Variables examined in this study are net primary production (NPP), heterotrophic respiration (R(h)), net ecosystem carbon exchange (NEE), runoff, and evapotranspiration (ET). Our modeling results show that nonlinear patterns were parabolic, asymptotic, and threshold-like in response to temperature, CO2, and precipitation anomalies, respectively, for NPP, NEE, and R(h). Runoff and ET exhibited threshold-like pattern in response to both temperature and precipitation anomalies but were less sensitive to CO2 changes. Ecosystem responses to combined temperature, CO2, and precipitation anomalies differed considerably from the responses to individual factors in terms of response patterns and/or critical points of nonlinearity. Our results suggest that nonlinear patterns in response to multiple global-change factors were diverse and were considerably affected by combined climate anomalies on ecosystem carbon and water processes. The diverse response patterns in nonlinearity have profound implications for both experimental design and theoretical development.     

Simulation modeling of material and energy flow through an ecosystem: Methods and documentation

This paper discusses the process of development of large-scale ecological simulation models as it proceeds through steps divided between two major phases — conceptualization and implementation. The activities in these phases are strongly influenced by model objectives. Activities transpiring in each step are discussed and documentation methods both for the modelling process and its product are introduced for each of the steps. Examples are given from CONIFER, a large-scale coniferous forest model developed by the author in cooperation with another investigator. The role of the model documentation, both in aiding model development and in clearly communicating and allowing criticism of the model, is emphasized. Model evaluation, checking that the model satisfies its objectives, is seen as an area of model development which indicates which parts of the model need reworking.     

Effects of experimental protocol on global vegetation model accuracy: A comparison of simulated and observed vegetation patterns for Asia

Prognostic vegetation models have been widely used to study the interactions between environmental change and biological systems. This study examines the sensitivity of vegetation model simulations to: (i) the selection of input climatologies representing different time periods and their associated atmospheric CO₂ concentrations, (ii) the choice of observed vegetation data for evaluating the model results, and (iii) the methods used to compare simulated and observed vegetation. We use vegetation simulated for Asia by the equilibrium vegetation model BIOME4 as a typical example of vegetation model output. BIOME4 was run using 19 different climatologies and their associated atmospheric CO₂ concentrations. The Kappa statistic, Fuzzy Kappa statistic and a newly developed map-comparison method, the Nomad index, were used to quantify the agreement between the biomes simulated under each scenario and the observed vegetation from three different global land- and tree-cover data sets: the global Potential Natural Vegetation data set (PNV), the Global Land Cover Characteristics data set (GLCC), and the Global Land Cover Facility data set (GLCF). The results indicate that the 30-year mean climatology (and its associated atmospheric CO₂ concentration) for the time period immediately preceding the collection date of the observed vegetation data produce the most accurate vegetation simulations when compared with all three observed vegetation data sets. The study also indicates that the BIOME4-simulated vegetation for Asia more closely matches the PNV data than the other two observed vegetation data sets. Given the same observed data, the accuracy assessments of the BIOME4 simulations made using the Kappa, Fuzzy Kappa and Nomad index map-comparison methods agree well when the compared vegetation types consist of a large number of spatially continuous grid cells. The results of this analysis can assist model users in designing experimental protocols for simulating vegetation.     

Numerical modeling of simultaneous tracer release and piscicide treatment for invasive species control in the Chicago Sanitary and Ship Canal,Chicago, Illinois

In December 2009, during a piscicide treatment targeting the invasive Asian carp in the Chicago Sanitary and Ship Canal, Rhodamine WT dye was released to track and document the transport and dispersion of the piscicide. In this study, two modeling approaches are presented to reproduce the advection and dispersion of the dye tracer (and piscicide), a one-dimensional analytical solution and a three-dimensional numerical model. The two approaches were compared with field measurements of concentration and their applicability is discussed. Acoustic Doppler current profiler measurements were used to estimate the longitudinal dispersion coefficients at ten cross sections, which were taken as reference for calibrating the longitudinal dispersion coefficient in the one-dimensional analytical solution. While the analytical solution is fast, relatively simple, and can fairly accurately predict the core of the observed concentration time series at points downstream, it does not capture the tail of the breakthrough curves. These tails are well reproduced by the three-dimensional model, because it accounts for the effects of dead zones and a power plant which withdraws nearly 80 % of the water from the canal for cooling purposes before returning it back to the canal.     

Persistence of carbaryl and its risk assessment through consumption of treated grapes

The average initial deposits of carbaryl were observed to be 1.4 and 3.1?mg?kg^?1, respectively, following four applications of the insecticide at 4.95 and 9.9?kg active ingredient per hectare. Residues of carbaryl dissipated below its limit of quantification of 50?µg?kg^?1 after 7 and 10 days at single and double the application dosage, respectively. The half-life values (t _1/2) of carbaryl were worked out to be 1.3 and 0.7 days, respectively, at single and double dosages. The acceptable daily intake (ADI) for carbaryl has been fixed at 8?µg?kg^?1 body weight per day. Keeping in view the residues of carbaryl observed one day after the last application, a child of 10?kg and an adult of 60?kg will have an intake of 77 and 154?µg carbaryl after consumption of 100 and 200?g grapes, in comparison to its ADI of 80 and 480?µg; thus, no health risk is to be expected. Therefore, a waiting period of 1 day has been suggested for the safe consumption of carbaryl-treated grapes to avoid any health hazards.     

Analysis of neighborhood dynamics of forest ecosystems using likelihood methods and modeling.

Advances in computing power in the past 20 years have led to a proliferation of spatially explicit, individual-based models of population and ecosystem dynamics. In forest ecosystems, the individual-based models encapsulate an emerging theory of "neighborhood" dynamics, in which fine-scale spatial interactions regulate the demography of component tree species. The spatial distribution of component species, in turn, regulates spatial variation in a whole host of community and ecosystem properties, with subsequent feedbacks on component species. The development of these models has been facilitated by development of new methods of analysis of field data, in which critical demographic rates and ecosystem processes are analyzed in terms of the spatial distributions of neighboring trees and physical environmental factors. The analyses are based on likelihood methods and information theory, and they allow a tight linkage between the models and explicit parameterization of the models from field data. Maximum likelihood methods have a long history of use for point and interval estimation in statistics. In contrast, likelihood principles have only more gradually emerged in ecology as the foundation for an alternative to traditional hypothesis testing. The alternative framework stresses the process of identifying and selecting among competing models, or in the simplest case, among competing point estimates of a parameter of a model. There are four general steps involved in a likelihood analysis: (1) model specification, (2) parameter estimation using maximum likelihood methods, (3) model comparison, and (4) model evaluation. Our goal in this paper is to review recent developments in the use of likelihood methods and modeling for the analysis of neighborhood processes in forest ecosystems. We will focus on a single class of processes, seed dispersal and seedling dispersion, because recent papers provide compelling evidence of the potential power of the approach, and illustrate some of the statistical challenges in applying the methods.     

The occurrence of lithium in the environment of the Jordan Valley and its transfer into the food chain

Lithium is found in trace amounts in all soils. It is also found in plants and in nearly all the organs of the human body. Low Li intake can cause behavioral defects. Thus, this study was conducted to investigate the concentration and distribution of water-soluble Li in soils of the Jordan Valley and its concentration in citrus trees and some important food crops in view of the significant implications of Li for human health. The concentration of soluble Li was measured in 180 soil samples collected at two depths (0–20 and 20–40 cm) whereas its content was determined in fully expanded leaves collected from citrus and different vegetable crops. Concentrations of soluble Li in soils vary from 0.95 to 1.04 mg l⁻¹ in topsoil and from 1.06 to 2.68 mg l⁻¹ in subsoil, while Li concentration in leaves ranged from 2 to 27 mg kg⁻¹ DM. Lithium concentrations in leaves of crops of the same family or different families vary with location in the valley; i.e., they decreased from north to south. It is concluded that soluble Li in soils and the plant family did not solely affect Li transfer in the food chain. In addition, soil EC, Ca, Mg, and Cl, which increased from north to south, might adversely affect plant Li uptake. The current study also showed that consuming 250–300 g FW of spinach day⁻¹ per person is recommended to provide consumers with their daily Li requirement necessary for significant health and societal benefits.     

Spatial and temporal occurrence of the parasitic dinoflagellate Duboscquella cachoni and its tintinnine host Eutintinnus pectinis in Chesapeake Bay

Eutintinnus pectinis (Kofoid, 1905) Kofoid and Campbell is a seasonally important component of the Chesapeake Bay, USA, microzooplankton. During the summers of 1986 and 1987, E. pectinis populations commonly reached densities well above 10³ cells l^-1 and were often heavily infected by Duboscquella cachoni Coats, 1988, a lethal parasitic dinoflagellate. The temporal and spatial occurrence of D. cachoni suggests that this parasite has a significant impact on E. pectinis populations and may, under appropriate conditions, regulate host abundance. Infection levels above 10% were frequently encountered and epizootic events with 20 to 50% of host individuals parasitized by dinoflagellates were observed over broad areas. Epizootic infections were usually recorded in regions of the Bay that had high concentrations of E. pectinis, and data for vertical profiles, when integrated with depth, showed a significant positive correlation (p0.01) between host abundance and parasite prevalence. However, peak E. pectinis density and maximum levels of parasitism were often not vertically coincident at stations, and a clear relationship between host abundance and parasite prevalence was not evident for data from discrete samples. These vertical distributions and the absence of a correlation between host density and parasite prevalence for discrete samples may reflect death of E. pectinis as epizootics spread through the host population. Bay-wide infection levels averaged 10.4% (±1.73 SE) for eight cruises in 1986 and indicate that parasite-induced mortality removes 7 to 24% of the E. pectinis standing stock per day. Comparison of these values to ingestion rates for copepods on tintinnine ciliates reveals that parasite-induced mortality of E. pectinis is comparable to predation pressure by the dominant mesozooplankton grazers in Chesapeake Bay.     

A hydrodynamic and water quality modeling study of spatial and temporal patterns of phytoplankton growth in a stratified lake with buoyant incoming flow

A three-dimensional hydrodynamic and water quality model was applied to Lake Paldang, a lake in South Korea that is stratified by incoming flows. The spatial and temporal patterns of phytoplankton growth in this lake were determined from the model. The model was calibrated and verified using data measured under different hydrological conditions. The model results were in reasonable agreement with the field measurements, in both the calibration and verification phases. The distributions of water quality and residence time in the lake and phytoplankton response to changes in nutrient loads were examined with the model, and the influence of the hydrodynamics on phytoplankton response was analyzed. The simulation results indicated that Lake Paldang is an essentially phosphorus-limited system, but that phytoplankton growth is limited by low water temperature and short residence time during the winter and the summer monsoon period, respectively. The results of sensitivity analyses also suggested that the hydrodynamics within the lake may have an indirect influence on phytoplankton responses to changes in the limiting nutrient loads, and that reducing phosphorus loading from Kyoungan Stream should be a high priority policy for controlling algal blooms during the pre- and post-monsoon periods. From this study, it was concluded that the three-dimensional water quality model incorporating hydrodynamic processes could successfully simulate phytoplankton response to changes in nutrient loads and that it could become a useful tool for identifying the essential factors determining phytoplankton growth and for developing the best management policy for algal blooms in Lake Paldang.     

中国种子植物物种丰富度的大尺度分布格局及其与地理因子的关系

地理因子对物种多样性空间分布格局的影响具有重要意义.文章利用大尺度的物种分布数据以及地理信息,结合GIS和数理统计方法,探讨了中国种子植物物种丰富度的空间分布格局及其与地理因子的关系.结果表明,从南到北,研究区域内物种丰富度总体上呈递减趋势;在经度梯度上,从东到西,物种丰富度呈递增趋势,这可能与其它地理因子的影响有关;在排除其它因子影响的情况下,物种丰富度随着面积的增加,呈递增趋势.但在其它地理因子的综合影响下,面积的影响作用被掩盖或弱化.物种丰富度随着海拔变幅的增加,呈显著递增趋势;物种丰富度与纬度变幅、经度变幅之间不存在显著的(偏)相关性.总体上,纬度、面积和海拔变幅均显著影响物种丰富度的分布格局,但相对而言,面积和纬度起着更为重要的影响.相对海拔变幅而言,海拔变幅与纬度之比值能更好地反映"生境异质性"效应,说明,海拔梯度的"纬度效应"值得关注.     

鼎湖山锥栗种子特征及其对动物取食格局的影响

通过对鼎湖山自然保护区锥栗种子特征的分析及进行种子取食实验，研究探讨了锥栗种子特征对动物取食格局的影响。结果表明，锥栗作为鼎湖山季风常绿阔叶林中的重要建群种之一，其更新困难的主要原因就在于种子扩散前后面临巨大的取食压力。动物对种子取食偏爱同种子大小呈现出一定的相关性，随着种子尺寸增加，取食率有线性增加的趋势。但是，锥栗应对动物取食并非完全被动的，它也发展了一些特有的生活史策略。锥栗种子的颜色与环境凋落物及土壤色相似，可以减少被取食者发现的机率。更重要的是，锥栗种子带刺的总苞有良好的保护作用。具总苞的种子取食的强度，显著低于无总苞的种子（P〈0．01）。     

Characterization of phosphorus species and modeling for its organic forms in eutrophic shallow lake sediments,North China

Variations of phosphorus （P） and its species in surface sediment of Baiyangdian Lake, a eutrophic shallow lake located in North China, were investigated through combination of field survey and numerical calculation based on cluster analysis. P fractionation was performed by a sequential extraction scheme, categorized as loosely bound P （NH4Cl-P）, reductant soluble P （BD-P）, metallic oxide bound P （NaOH-P）, calcium bound P （HCl-P） and organic P （Org-P）. P concentrations exhibited regional similarities and a total of four sub-areas were identified in which the same rank was HCl-P 〉 Org-P 〉 BD-P ,=NaOH-P 〉NH4Cl-E NH4Cl-P, BD-P and Org-P were found to contribute to P enrichment in overlying water column. Specifically, labile Org-P acted as a potential pool with a greater contribution in aerobic layer compared to anaerobic layer. A hysteresis （lag = 4 months） existed when labile Org-P concentration was negatively correlated with aerobic layer thickness. In view of magnitude of identified P contributors in sub-areas, higher potential of P release was present in Fuhe River and Tang River estuary areas. On the basis of calibration and verification, the mathematical model with parameter settings applied in this study was improved to serve as a tool for limnology management and eutrophic control.     

The Scotia Sea krill fishery and its possible impacts on dependent predators: modeling localized depletion of prey

The nature and impact of fishing on predators that share a fished resource is an important consideration in ecosystem-based fisheries management. Krill (Euphausia superba) is a keystone species in the Antarctic, serving as a fundamental forage source for predators and simultaneously being subject to fishing. We developed a spatial multispecies operating model (SMOM) of krill-predator fishery dynamics to help advise on allocation of the total krill catch among 15 small-scale management units (SSMUs) in the Scotia Sea, with a goal to reduce the potential impact of fishing on krill predators. The operating model describes the underlying population dynamics and is used in simulations to compare different management options for adjusting fishing activities (e.g., a different spatial distribution of catches). The numerous uncertainties regarding the choice of parameter values pose a major impediment to constructing reliable ecosystem models. The pragmatic solution proposed here involves the use of operating models that are composed of alternative combinations of parameters that essentially try to bound the uncertainty in, for example, the choice of survival rate estimates as well as the functional relationships between predators and prey. Despite the large uncertainties, it is possible to discriminate the ecosystem impacts of different spatial fishing allocations. The spatial structure of the model is fundamental to addressing concerns of localized depletion of prey in the vicinity of land-based predator breeding colonies. Results of the model have been considered in recent management deliberations for spatial allocations of krill catches in the Scotia Sea and their associated impacts on dependent predator species.     

Incidence,occurrence and distribution of the nematode Echinomermella matsi in its echinoid host,Strongylocentrotus droebachiensis,in northern Norway

The incidence, occurrence and distribution of the nematode Echinomermella matsi (Jones and Hagen) in its host, the echinoid Strongylocentrotus droebachiensis Müller, were examined in Norwegian waters from Nordmre (63° N) to the Russian border (70° N) in a range of habitats (e.g. kelp cover and community type) from 1982 to 1992. The results are used to examine the likely influence of the parasite on fitness (individual growth and gonad production) and its potential in regulating the population size of its echinoid host. The nematode infections are restricted to areas between Vikna (Vega) and middle Troms, with the highest prevalence (40 to 88% infected) in the Bodø area, the focus of the distribution. The prevalence rates are similar on kelp beds and barren grounds. No difference in growth rates between infected and noninfected sea urchins was found. Nematode-infected sea urchins in kelp bed populations had gonads weighing about one-sixth of those of equivalent uninfected individuals. This indicates that nematodes are really parasites causing reduced reproductive capacity. Areas with high prevalence (>40% infected) of nematodes had low sea urchin densities. High nematode intensities were found in the areas with high prevalence. The mean abundance in high prevalence areas was highest (eight nematodes) in the 4-to 7-yr-old age group and decreased to zero among the oldest age groups. The ratio of variance/mean abundance was also highest among 5-to 8-yr-old sea urchins. At highly and slightly infected locations, the relationships between the log of the variance and the log of the mean abundance of parasites were 1.35 and 1.69, respectively. Measurements of the frequency distribution of nematodes in sea urchins and the corresponding estimates of the negative binomial distribution showed significantly higher counts in estimated than observed subpopulations exceeding 20 nematodes per sea urchin. These results may explain nematode-induced sea urchin mortality. The low density of the host in the Bodø area, which had high prevalence, may be a result of increased host mortality caused by nematodes, by lower recruitment because of reduced gonad production, or by other factors. Low prevalence among older sea urchins may be caused by nematodeinduced host mortality or by cycles in infection. However, studies on the life cycle of the nematode and long term investigations of host density and nematode intensity/prevalence will be needed before any true conclusions can can be drawn.     

区域农田生态系统生产力的时空格局及其影响因子研究——以山东省为例

在统计数据的基础上,以山东省为例,利用模型量化了农田生态系统净初级生产力（NPP）,并研究了农田生态系统NPP的时空格局及其影响因素。研究发现,2000—2006年间,山东省农田生态系统NPP在时间序列上整体呈上升的趋势,由2000年的476.5g·m-2·a-1（以C计）上升到2006年的544.2g·m-2·a-1（以C计）。空间格局中以鲁东、鲁中和鲁南较高,鲁西南和鲁北较低。各地市中以枣庄最高,为691g·m-2·a-1（以C计）;东营最低,约424.4g·m-2·a-1（以C计）。另外,莱芜、临沂及菏泽等地也相对偏低。通过对影响农田生态系统NPP的自然因子和人为因子分别进行主成分分析发现：气候因子中对山东省农田生态系统NPP贡献最大的为降水;人为因子中以农膜的贡献最大,其次为农药、机械、化肥,而劳动力的贡献则随着科技的发展而降低,人口密度的过大对农田生态系统生产力具有较大的负面影响。