Depth-time distributions of detritus depositions in Lake Nemi (volcanic lake of central Italy)

The depth-time distributions of detritus depositions onto lake bottom and the amount of resident organic matter on the upper layer of the bottom have been assessed in a volcanic lake. Depositions were sampled monthly across the lake at four depths (0.2 m; 2 m; 6 m; 30 m) during two years (1983–1984). Organic and ash fractions of sediment cores collected along a depth gradient were assessed in the summer of 1984. The result show:

On the stability of the stock-harvesting system controlled by a feedback management procedure

Stability of the stock-harvesting system regulated by a feedback control procedure of catch quota is examined. In the procedure considered, catch quota is changed proportionally to the difference between current and the target stock level (with a proportionality constant h) and to the annual stock growth rate (with a proportionality constant g). Condition for the local stability of the target equilibrium is obtained as a function of the stock-recruitment relation, survival probability of adults, target stock level, time lag before implementation of regulation, age of sexual maturity of the stock, and proportionality constants g and h. It is shown that, (1) the procedure has the stabilizing effect; it can stabilize the target stock level that is unstable under constant harvest, (2) lower target stock level favors larger g and smaller h, when the target is set around MSYL (the stock level that gives MSY), (3) the degree of stability, measured by the time required to recover the target stock level, is an increasing function of the target stock level, (4) stability and sustainable yield are in trade-off, (5) time delay caused by the time needed before sexual maturity does not affect the stability significantly, but the effect of the time lag before implementation of regulation is significant. Comparison between harvest-control and effort-control procedures is also made, and the advantage of the latter in terms of stability is shown.     

Carbon steady-state model of the planktonic food web of Lake Biwa, Japan

1. A steady‐state model of carbon flows was developed to describe the summer planktonic food web in the surface mixed‐layer of the North Basin in Lake Biwa, Japan. This model synthesised results from numerous studies on the plankton of Lake Biwa. 2. An inverse analysis procedure was used to estimate missing flow values in a manner consistent with known information. Network analysis was applied to characterise emergent properties of the resulting food web. 3. The system strongly relied on flows related to detrital particles. Whereas primary production was mainly by phytoplankton >20 μm, microzooplankton were active and mainly ingested detritus and bacteria. 4. The main emergent property of the system was strong recycling, through either direct ingestion of non‐living material by zooplankton, or ingestion of bacteria after degradation of detritus to release dissolved organic carbon.     

Cellulase activity of leaf litter and stream-dwelling,shredder macroinvertebrates

The magnitude and temporal variability of exocellulase (-1,4-exoglucanase) activity in leaf litter and guts of shredding macroinvertebrates was determined over one year in four streams in Virginia, USA. The streams flowed in three physiographic provinces and hence varied as to geomorphology, hydrology, water chemistry and riparian landscape. No significant difference in exocellulase activity occurred between streams over the year. Considerable temporal variation in activity did occur in all streams, with peaks in autumn-early winter and again in spring, corresponding to the primary periods of input of fresh allochthonous organic matter. Litter bag studies showed that peak exocellulase activity occurred after about one month of processing. Exocellulase activity in the guts of shredders was generally correlated with activity in their detrital food, suggesting that gut enzyme activity was acquired.     

生态韧性视角下绿色空间时空演变及优化研究进展

在快速城镇化以及全球气候变化的背景下,城市面临着严重的生态环境挑战。如何提升生态系统韧性,增强城市抵抗内外干扰的能力对区域可持续发展至关重要,已引起学界及社会各界的高度重视。绿色空间是协调生态环境与城乡发展的重要抓手,也是落实生态韧性提升的重要载体,结构完整、功能完善的绿色空间能够有效提升城市应对环境风险的能力。因此,在梳理多学科背景下绿色空间研究视角与研究内容的基础上,阐述绿色空间时空演变、驱动机制、情景模拟等方面的研究进展。此外,基于对生态韧性理论发展历程以及国内外相关研究的梳理,总结不同尺度下以生态韧性提升为导向的绿色空间优化路径,探讨各尺度绿色空间生态韧性分析及优化与现行绿地系统规划、国土空间规划体系的衔接。最后,对比国内外研究进展,提出国内未来研究应更加关注多层级生态韧性评价体系构建、社会-生态系统的整体分析以及阈值视角下不同生态韧性绿色空间的分区治理,以期扩展绿色空间规划与建设的思路,助力自然和社会空间的协调配合与共同发展。     

The use of a rapid radiolabeling method for measuring ingestion rates of detritivores

Utilization of the organic components of senescent Spartina alterniflora Loisel detritus by the grass shrimp, Palaemonetes pugio Holthuis, was investigated in laboratory feeding studies. A ¹⁴C-dimethyl sulfate labeling procedure was utilized to label the sterilized detritus. The formed covalent bond is stable to autoclaving, freezing and extremes of pH. An ingestion rate of 2.0 × 10^?4CS·h^?1 was determined for P. pugio. Estimates for rate of incorporation, gross growth efficiency, and total biomass incorporated are presented. An inverse relationship was demonstrated between shrimp size and rates of ingestion and incorporation.     

Flow and retention of particulate organic matter in riparian fluvial habitats under different climates

The flow and retention of particulate organic matter were compared in two fluvial systems under different climates: the French upper Rhone (temperate climate) and the lower Moulouya in Morocco (Mediterranean climate). In both systems, a breakdown gradient was observed. This gradient was correlated with water motion, oxygen content, richness in hyphomycete species and occurrence of their mycelia and spores on submerged leaves, invertebrate density and consumption by shredders.U.A. CNRS 1451 Ecologie des Eaux Douces et des Grands FleuvesU.A. CNRS 1451 Ecologie des Eaux Douces et des Grands Fleuves     

矿山生态恢复研究进展——基于连续三届的世界生态恢复大会报告

最近连续三届世界生态恢复大会都将矿山生态系统列为大会交流的主题之一。为了解矿山生态修复的最新进展,本文采用文献分析方法和统计分析法,全面对比了这三届大会的论文和报告,包括参会国家、主要机构、热点矿区、修复要素、矿山类型、修复技术等。在此基础上,归纳了新开发的生态修复技术,包括植被恢复、土壤修复和景观恢复等新技术;总结了当前的研究热点,主要有复垦的土壤和修复的植物之间相互作用的机理、矿山生态修复的监测新技术、本土物种保持、污染土壤修复新技术、应对全球气候变化的矿山生态修复新思维和矿山生态系统服务价值等;介绍了会议提出的新观点,如自然恢复和人工恢复选择的新标准、矿山生态恢复力新理论、新型矿山生态系统及其设计等。最后对未来研究趋势进行了预测。     

Species aggregation: the influence of detritus in a benthic invertebrate community

Species aggregation with detritus was examined in a zoobenthic stream community. Detritus was quantified (dry weight in particle size categories) in contiguously arranged quadrats along four transects within a 40m stream section. Total organism density was found to be positively related to increasing detrital biomass (dry weight) in all transects, although the magnitude of this association was influenced by the detrital particle size distribution in each quadrat. Eliminating certain particle size categories of detritus resulted in substantial changes in the magnitude of association. For example, in one transect, total organism density and total detrital biomass showed no association. However, when one particle size category (greater than 10 mm) was removed a highly significant relationship was found. Total detrital biomass was found to be a useful predictor of organism distribution, however, inordinately high detrital biomass and variance within larger particle size categories can mask a relationship. This result suggests that the use of discrete size categories is necessary when considering species/ detrital relationships.Significant associations were found between the density of particular species and total biomass of detritus. The magnitude, as well as significance, of these associations were found to vary when correlations were calculated with restricted particle size categories of detritus. Species associations were often not consistent between transects, possibly due to local characteristics of detritus or overriding environmental factors. Current velocity was found to be unimportant in determining the detrital biomass held in the substrate. Likewise, few associations were found between current velocity and organism density in three out of four transects. Results of this study suggest that habitat selection by some taxa is influenced by local variation in detrital biomass, as well as detrital particle size composition.     

Life History of Lepidostoma hirtum in an Iberian Stream and its Role in Organic Matter Processing

The goal of this research was to determine the role of Lepidostoma hirtum Fabricius 1775 in the fragmentation of allochtonous organic material, in a segment of a mountain river in central Portugal. For this purpose, we measured leaf fragmentation and growth rates at four temperatures (9, 12, 15 and 18 °C) and four leaf types (alder, Alnus glutinosa L.; oak, Quercus andegavensis Hy; poplar, Populus × canadensis Moench; and chestnut, Castanea sativa Mill.). Growth rates ranged from 0.012 to 0.049 mg AFDW day⁻¹ with no significant effect of temperature and leaf type. Fragmentation/consumption rates were significantly higher for alder (1.62 mg animal⁻¹ day⁻¹) than for other leaf types, and significantly lower at 9 °C (0.70 mg animal⁻¹ day⁻¹) than at any other temperature (1.12 mg animal⁻¹ day⁻¹). In the studied stream, L. hirtum larvae had a univoltine life history, with an asynchronous development. Secondary production of L. hirtum ranged from 53.95 mg m⁻² year⁻¹ (pools) to 63.12 mg m⁻² year⁻¹ (riffles). Annual P/B ratios differ between habitats: they were 4.01 year⁻¹ for pools and 4.49 year⁻¹ for riffles. Considering the average density of this species in the study river and their consumption rates, this species has the potential to fragment 8.6 times the mean annual standing stock of organic matter, in the study location.     

生态学数学模型的研究进展

当前许多生态学的研究工作使用了数学的方法和手段。因为它可以对生态现象进行量化的研究,而且理论上的分析往往还能使研究结果得以深化。数学模型是数学的思想和方法应用于生态学研究的桥梁。自从60年代数学模型的研究在生态学上再次被人们重视以来,其发     

基于GISP模型的城市绿色基础设施多功能性评估

绿色基础设施建设是加强城市生态弹性力的重要手段之一。绿色基础设施多功能性是实现城市生态系统服务功能综合效益最大化的前提,这一点已被众多学者认可。构建绿色基础设施规划(GISP,Green Infrastructure Spatial Planning)模型,基于绿色基础设施的雨洪管理、绿色空间可达性、净化空气、缓解热岛效应、景观连通性五大功能指标,开展城市绿色基础设施多功能性评估,明确合肥市绿色基础设施的高需求地区,探讨绿色基础设施不同功能之间的权衡和协同关系。结果表明:合肥市东北部对于绿色基础设施缓解城市热岛效应、净化空气的需求最强烈,城市一环区域对于绿色基础设施的雨洪管理需求最为强烈,城市东部、南部对于绿色基础设施的绿色空间可达性需求显著;总体而言,绿色基础设施选址的热点区域为城市一环内及东北区域;绿色基础设施的雨洪管理、缓解城市热岛和净化空气间存在着协同关系,与景观连通性之间存在着权衡关系;运用GISP模型评估合肥生态空间体系控制规划以及合肥市域空间绿道网络系统建设总体规划,规划中绿地选址不在绿色基础设施的高需求区域,也没有在战略上整合绿地多功能的生态系统服务、获得更大的生态弹性力。     

Radio-tracking rafts of giant kelp: local production and regional transport

Forests of giant kelp Macrocystis pyrifera (L.) C.A. Agardh are among the most productive communities on earth. Much of the annual production of kelp in central California is exported from the forests as large floating rafts. Since these rafts may float for days and perhaps weeks, they are capable of being transported long distances but the fate of this material remains largely unknown. Naturally occurring and artificially created M. pyrifera rafts were tagged with radiotransmitters near their point of origin along the shores of the Monterey Peninsula in Monterey County, California, on each of four seasonal tracking experiments. Their movements were followed by aircraft for 5–7 days and the transmitters were then recovered. 39 tagged kelp rafts were recovered within Monterey Bay and one transmitter was lost at sea. Most were recovered ashore. While surface currents in Monterey Bay flow to the north much of the year, the kelp rafts drifted before the prevailing northwest winds (i.e., to the southeast) in the spring, summer and autumn. Rafts tagged during the winter moved primarily toward the north. The regional deposition pattern of locally produced kelp rafts suggests that this material may be delivered to offshore benthic communities as large parcels which may play an important role as food and/or habitat.