EFFECTS OF PLACER GOLD MINING ON PRIMARY PRODUCTION IN SUBARCTIC STREAMS OF ALASKA1

ABSTRACT: Turbidity, total residues, settleable solids, vertical light extinction, and primary production were measured in mined and unmined streams located in the interior highlands of Alaska. Undisturbed streams had low turbidities (< 1 NTU), total residue concentrations averaging 120 mg 1^?1, and undetectable settleable solids. During active mining, turbidity, total residues, and settleable solids levels in a moderately mined stream averaged 170 NTU, 201 mg 1^?1, and < 0.1 ml 1^?1, respectively. In a heavily mined stream, turbidity and total residues were two orders of magnitude higher than in unmined streams and settleable solids nearly always exceeded 0.2 ml 1^?1. Vertical extinction coefficients and turbidity were positively correlated. In undisturbed streams gross primary productivity (g-O₂m^?2d^?1) ranged from 0.20 shortly after spring breakup to a maximum of 1.20 in early fall. Productivity in the moderately mined stream was reduced by 50 percent while photosynthetic efficiency doubled. Primary production was undetectable in a heavily mined stream. Maximum standing crops of periphyton measured as chlorophyll a occurred in fall in an undisturbed stream after 13 weeks of exposure and ranged from 4.5 to 11.8 mg-chl a m^?2. The highest chlorophyll a densities recorded in the moderately mined stream was 3.8 mg m^?2, and no chlorophyl a was detected in the heavily mined stream.     

Diagnostic variables as predictors of ecological risk

The state of an ecosystem may be represented by a multidemensional state vector,x. The goal of ecosystem management is to insure that the ecosystem remains within some setX of acceptable states, such thatx X. Since ecosystem management decisions must be based on limited knowledge, a small number of diagnostic variables must be found which accurately reflect ecosystem state. If the vector of diagnostic variables, , is found to be within a specified set , the state vectorx is predicted to be withinX. The selection and use of such diagnostic variables is examined in the context of an aquatic ecosystem simulation model. Techniques used in searching for diagnostic criteria include multiple linear regression, discriminant analysis, and visual inspection of graphical data displays. The adequacy of a diagnostic criterion as a predictor of ecological risk is demonstrated to be a function of the associated rates of type I and type II statistical errors. A simple cost-benefit analysis is undertaken to illustrate one approach for choosing an optimal balance between these error rates.     

论天然气水合物与海底地质灾害、气象灾害和生物灾害的关系

论述了天然气水合物与海底滑坡、全球变暖和海底生物灭绝等地质、气象、生物灾害的关系。海底天然气水合物的分解能够减小沉积物的胶结强度,并导致沉积层孔隙压力的过剩,进而诱发海底滑坡的发生。天然气水合物与全球变暖关系密切。从天然气水合物释放出来的甲烷可使地球温度升高4℃至8℃,升温的结果一方面可能中和全球变冷的趋势,另一方面也可能加剧全球变暖的趋势。全球天然气水合物大规模的分解,导致了海底单细胞生物大量灭亡,对海底生物多样性的保持构成巨大危害。在天然气水合物开发利用的设计阶段和实施阶段,必须有足够的防范意识和技术措施,防止或尽可能减少天然气水合物开发利用造成的各种环境灾害。     

钢在热带海洋大气中的腐蚀

研究低碳钢和中碳钢在新加坡陆地与海上浮筏的大气腐蚀，浮筏上低碳钢的腐蚀比在陆地上快，含碳量高的钢腐蚀慢，此文试图将温度，湿度，润湿时间，降雨量，太阳辐射与干喷砂低碳钢在陆地试验点的腐蚀率联系起来，提出了冬季暴露几个月的样品失重的腐蚀深度表达式0．1078＋0．000596xum，扫描电镜检查显示在陆地曝露的样品氧化膜呈斑状，而浮筏上的样品有连续的氧化膜且氧化膜上裂纹也是连续的，能谱分析表明，浮筏上样品的氧化膜含有大量的氯化物和原子吸附，研究认为氧化膜是由FeOOH构成的，在陆地暴露2年的试样腐蚀率为0．016mm/year，浮筏上海洋大气曝露0．6年的腐蚀率为0．659mm/year。     

Predicting Plant Extinction Based on Species-Area Curves in Prairie Fragments with High Beta Richness

Abstract:  Species-area relationships and island biogeography theory are commonly used to predict how species richness will decline with fragmentation. There are a variety of largely untested assumptions in these approaches, including the assumptions that populations are distributed uniformly before fragmentation, and that local extinctions are due to effects of small population sizes. If populations are not distributed uniformly, then populations can be abundant locally but rare globally. This would cause extinction rates to be smaller than predicted. We tested extinction theory by developing estimates of the number of plant species that should be present in small tallgrass prairie fragments and then testing the uniformity assumption by partitioning species richness into α (within site) and β (among site) components in Iowa prairies. Many more native prairie plant species were present in surveys of prairie fragments (491) than was predicted based on theory (27–207). A large proportion (75%) of the total species richness was β richness. We suggest that the high proportion of β richness was responsible for the shallow species-area slopes and the lower than expected number of species losses and that a better understanding of what determines β diversity will improve predictions of fragmentation effects on richness of plants. We also suggest that plants in prairie remnants may be best conserved by protecting different prairie types rather than by protecting a few large areas containing a single prairie type.     

对虾高位池循环水养殖水体悬浮物等环境因子的变化特征

为了弄清对虾高位池循环水养殖过程中水体环境因子的变动规律,有效调控水体环境质量,提高养殖效益和生态效益,以凡纳滨对虾(Litopenaeus vannarnei)为试验对象,研究了高位池循环水养殖过程中水体溶解氧(DO)、悬浮物(SS)、pH值和叶绿素a(Chl-a)等环境因子的变化特征。设计了3种不同循环处理量组,即20m3/h组(P1组)、40m3/h组(P2组)和60m3/h组(P3组)。结果表明:不同循环处理量组的循环水养殖系统均能有效提高水体中DO质量浓度,相对空白对照组,P1、P2、P3对DO质量浓度的相对增长率分别为8%、15%、18%;各循环处理量组水体pH值均稳定在7.84～7.96;P1、P2对SS处理效果不明显,P3对SS的相对降低率达到34%;P1组Chl-a质量浓度变化不明显,P2、P3组Chl-a质量浓度分别降低13%和28%。综合比较分析:对虾高位池循环水养殖系统能明显提高水体DO质量浓度,维持水体pH值稳定平衡,降低水体SS和Chl-a质量浓度;60m3/h循环处理量组对水质调控效果最好,40 m3/h组次之,20 m3/h组较差。     

Population level effects of reduced fecundity in the fish species perch (Perca fluviatilis) and the implications for environmental monitoring

A 40% reduction in relative gonad size in perch (Perca fluviatilis) has been observed over that past two decades at the Swedish national reference site Kvädöfjärden. This biomarker response could be interpreted as a reduction in fecundity and increased risk of local extinction. However, abundance estimates from the same area has not provided any evidence of a reduction in population size. In the present study, a matrix population model was developed to investigate if a reduction in fecundity can be expected to have long term effects on population viability for perch and to evaluate the probability to detect such effects through abundance estimates. The model was parameterized from 17 years of population data from Kvädöfjärden as well as from other studies on perch. The model included density dependence and environmental stochasticity. The results indicated that a reduction in fecundity that is in level with the observed reduction in relative gonad size in Kvädöfjärden will cause a substantial risk for local extinction. The risk that the population will fall below 20% of the carrying capacity within 50 years is 44% when the fecundity is reduced by 40%. However, due to variability in abundance measurements it will take some time before a reduction in gonad size leads to statistically significant effects on the population. If the fecundity is reduced by 40% successively over a 10-year period, the probability to detect this through abundance estimates within 10 years is less than 50%. The results of the present study clearly show that relevant biomarkers have an important role in environmental monitoring as early warning signals, preferably in combination with measurements at higher levels of biological organization.     

Comparison of sensitivity analysis techniques: A case study with the rice model WARM

The considerable complexity often included in biophysical models leads to the need of specifying a large number of parameters and inputs, which are available with various levels of uncertainty. Also, models may behave counter-intuitively, particularly when there are nonlinearities in multiple input-output relationships. Quantitative knowledge of the sensitivity of models to changes in their parameters is hence a prerequisite for operational use of models. This can be achieved using sensitivity analysis (SA) via methods which differ for specific characteristics, including computational resources required to perform the analysis. Running SA on biophysical models across several contexts requires flexible and computationally efficient SA approaches, which must be able to account also for possible interactions among parameters. A number of SA experiments were performed on a crop model for the simulation of rice growth (Water Accounting Rice Model, WARM) in Northern Italy. SAs were carried out using the Morris method, three regression-based methods (Latin hypercube sampling, random and Quasi-Random, LpTau), and two methods based on variance decomposition: Extended Fourier Amplitude Sensitivity Test (E-FAST) and Sobol’, with the latter adopted as benchmark. Aboveground biomass at physiological maturity was selected as reference output to facilitate the comparison of alternative SA methods. Rankings of crop parameters (from the most to the least relevant) were generated according to sensitivity experiments using different SA methods and alternate parameterizations for each method, and calculating the top-down coefficient of concordance (TDCC) as measure of agreement between rankings. With few exceptions, significant TDCC values were obtained both for different parameterizations within each method and for the comparison of each method to the Sobol’ one. The substantial stability observed in the rankings seem to indicate that, for a crop model of average complexity such as WARM, resource intensive SA methods could not be needed to identify most relevant parameters. In fact, the simplest among the SA methods used (i.e., Morris method) produced results comparable to those obtained by methods more computationally expensive.     

Convexity in projection matrices: Projection to a calibration problem

Convexity, as a fundamental property of sets and functions defined on convex sets, plays an important role in many mathematical and applied disciplines, including extremal and optimal-control problems. We prove the set of all feasible projection matrices in a general class of matrix models for stage-structured population dynamics to be convex and the dominant eigenvalue (λ₁) of any projection 2 × 2 matrix to be either a convex, or a concave function on a simplex of the matrix first-row entries (i.e., stage-specific reproduction rates). The latter is also conjectured for the general n × n case. Though looking far from practical needs of matrix population models, this mathematical result has appeared to be quite useful in solving a practical problem to calibrate the projection matrix, i.e., to estimate all the stage-specific vital rates, from empirical data. The data from monitoring of individual life histories of marked plants on permanent sample plots during successive years enable direct calculation of the stage-specific survival and ontogenetic transition rates, but the rates of reproduction do remain uncertain as far as the parent plants can hardly be determined for the (not yet marked!) recruitment.     

不同植茶年龄茶园蒸散速率的日变化——以宜兴市为例

以宜兴市盛道茶场3、9和20 a 3个不同植茶年龄的茶园为研究对象,基于静态箱/红外气体分析仪法,辅以植被生态监测和土壤湿度监测,研究茶园清明采茶前蒸散速率日变化特征。结果发现：（1）3个不同植茶年龄的茶园日蒸散速率变化趋势一致,呈以12〖DK〗∶00~15〖DK〗∶00蒸散速率为峰值的单峰曲线;（2）虽然3 a茶园叶面积指数（LAI）最低,但最大平均日蒸散速率、一日内蒸散速率的极值、6〖DK〗∶00~18〖DK〗∶00最大总蒸散量、一日内不同时段的蒸散速率最大变化幅度均出现在3 a茶园;（3）茶园日蒸散速率与气温的日变化趋势相似,且两者存在极显著相关性（R2=081*〖KG-*2〗*）,在湿润条件下与土壤含水率日变化相关性不明显,但两者呈相反的变化趋势