外源C、N干扰下吉林黑土区农田土壤动物组成与结构

2011年5月至9月作物生长期间,采用手拣法、改良干漏斗与湿漏斗三种方法,对吉林黑土区7种外源C、N干扰处理,即对照组(不施肥,CK)、0.5倍、1.0倍和2.0倍的外源C和N处理(C0.5、C1.0、C2.0、N0.5、N1.0、N2.0)农田土壤动物组成与结构进行研究.在作物生长季节,5次采样共获得土壤动物56 886只(未鉴定标本80只),隶属3门11纲23目3亚目79科(总科).数据分析显示,农田土壤动物主要集中在0～5 cm,基本上是随着土壤剖面加深而呈现下降趋势;与对照(CK)相比,农田土壤动物个体数与类群数随外源C浓度升高而呈递增趋势;农田大型土壤动物个体数随外源N浓度升高呈递减趋势;农田中小型土壤动物个体数随外源N浓度升高呈递增趋势.在研究时段内,土壤动物个体数与类群数于5-8月份呈现出上升趋势,9月份出现下降.方差分析显示,外源C、N干扰对农田中小型土壤动物个体数与类群数以及大型土壤动物类群数影响显著(p＜0.01),农田土壤动物个体数与类群数在作物生长季节内变化显著(P＜0.01).外源C、外源N分解释放出的养分与中小型土壤动物个体数、类群数以及大型土壤动物类群数密切相关.外源C有益于农田土壤动物功能群、大型与中小型农田土壤动物群落组成多样化.     

Essential Fish Habitat and the Effective Design of Marine Reserves: Application for Marine Ornamental Fishes

Extensive and unregulated harvest of marine ornamental fishes can lead to localized depletion of target species and habitat degradation from inappropriate collecting techniques. One potential solution to these problems is the creation of marine reserves where fishing is prohibited. Marine reserves have been shown to increase fish abundance and protect ecosystems from habitat destruction associated with fishing. If protective areas are to be effective, they must include the diversity of habitats necessary to accommodate the wide range of fish species that are of interest to the marine ornamental fish trade.Fish assemblages with high diversity and abundance are often associated with habitats of high structural complexity. A relationship between fish size and reef complexity suggests the importance of shelter as a refuge for certain fishes in avoiding predation. Many species tend to aggregate to spawn in structurally complex habitats to reduce their risk of predation. Closing of spawning areas during aggregation periods has been shown to be a highly effective management strategy for these species. The limited home ranges and high degree of habitat specificity associated with many marine ornamental fishes should make marine reserves a highly effective strategy for managing these resources.     

Interactions between juvenile roach or perch and their invertebrate prey in littoral reed versus open water enclosures

Abstract – Structural complexity offered by submerged macrophytes was shown to have fundamental effects on interactions between fish and their prey. However, less information is available for littoral reed (Phragmites spp.) stands. A previous field study found juvenile roach and perch to coexist within the reed stands. It was suggested that reed serves mainly as refuge against littoral piscivores, such that coexistence of perch and roach in the reed was externally forced. Several hypotheses were raised to explain why roach nevertheless showed good growth performance. Three of the hypotheses were tested experimentally. In particular, we were interested in how the confinement of fish to one of the reed or open water habitats alters feeding and growth patterns of juvenile age‐1 perch and roach. Fish were stocked separately into littoral enclosures for a 3‐week period in densities which had been found in the surrounding lake. Development of zooplankton and macroinvertebrate biomasses was observed by sampling the enclosures three times over the experimental period. Individual consumption of prey groups by the fish was calculated with a bioenergetics model, and was compared with prey group biomass in the enclosure treatments. The confinement of fish to one littoral habitat had clear effects on diet composition and growth rates. Roach fed less zooplankton and partially switched to macroinvertebrates in the reed enclosures when compared with the open water treatments, and consequently their growth rates were lower in the reed. Perch preferred macroinvertebrates in both habitats, without any difference in growth rates between the habitats. Effects of fish predation on both zooplankton and macroinvertebrate biomass were low in open water and reed enclosures. Daily consumption rates were only in a few cases higher than 40% of the available biomass of the respective prey group, but mainly were below 10% of available biomass. Therefore, we argue that both the diel horizontal migrations of roach and the relatively low consumption rate of fish when compared with the available resource biomass allow the coexistence of juvenile roach and perch in littoral reed stands.     

关于循环卷积的一个快速算法

本文指出文献［３］提出的循环卷积快速算法由于忽略了整数位长与时间复杂度的关系，其一次乘法所耗费的时间至少相当于原有的卷积直接乘的时间，若不考虑整数的位长，只用一次乘法便可算出卷积。     

农地规模经营的制约因素及对策

农地规模经营系统是一个复杂的社会经济系统,系统中存在一些制约农地经营规模扩大及经营效益提升的负反馈结构,只有消除负反馈结构的制约作用,才能更好地促进农地经营规模扩大、经营效益提升与农村经济的发展。利用系统动力学反馈动态复杂性分析理论与技术,建立了有效刻画农地规模经营复杂系统的结构模型,根据系统科学的系统结构决定行为的基本原理,利用基模分析技术分析了系统结构中的反馈关系,进行管理对策的生成研究,实现了以系统科学方法有效分析农地规模经营问题的目的。     

Ecosystem models for fisheries management: finding the sweet spot

The advent of an ecosystem‐based approach dramatically expanded the scope of fisheries management, creating a critical need for new kinds of data and quantitative approaches that could be integrated into the management system. Ecosystem models are needed to codify the relationships among drivers, pressures and resulting states, and to quantify the trade‐offs between conflicting objectives. Incorporating ecosystem considerations requires moving from the single‐species models used in stock assessments, to more complex models that include species interactions, environmental drivers and human consequences. With this increasing model complexity, model fit can improve, but parameter uncertainty increases. At intermediate levels of complexity, there is a ‘sweet spot’ at which the uncertainty in policy indicators is at a minimum. Finding the sweet spot in models requires compromises: for example, to include additional component species, the models of each species have in some cases been simplified from age‐structured to logistic or bioenergetic models. In this paper, we illuminate the characteristics, capabilities and short‐comings of the various modelling approaches being proposed for ecosystem‐based fisheries management. We identify key ecosystem needs in fisheries management and indicate which types of models can meet these needs. Ecosystem models have been playing strategic roles by providing an ecosystem context for single‐species management decisions. However, conventional stock assessments are being increasingly challenged by changing natural mortality rates and environmentally driven changes in productivity that are observed in many fish stocks. Thus, there is a need for more tactical ecosystem models that can respond dynamically to changing ecological and environmental conditions.     

基于新增序偶的传递闭包求解算法

针对在已有传递闭包的基础上新增序偶后的传递闭包求解问题,提出了一种基于新增序偶的传递闭包求解算法,并给出了详细证明过程.该算法在已有的传递闭包基础上,通过把新增序偶及该序偶的所有派生间接指向序偶添加到已有的传递闭包中实现求解过程,从而使算法的时间复杂度降低为O(n2),并且不受稀疏矩阵或序偶链的链长等不确定因素影响,最后通过一个实例说明了该算法的执行过程.     

韩国学生中介语各句长句子状语复杂度发展研究

通过分析韩国学生中介语句长为6—20个词句子的状语复杂度的发展情况,发现：初、中、高三级中介语各句长句子带状语句子比例、多层状语比例呈逐级上升趋势,多处状语比例和句首状语比例则呈逐级下降趋势;韩国学生中介语表现出句首状语比例超量、多处状语比例突出、多层状语比例不足的特点,在句长一定的前提下,多处状语与多层状语之间可能存在此消彼长的对立互补关系;研究同样发现中介语状语复杂度的发展具有不受教学输入语言制约的特点。     

Seasonal floodplain‐tidal slough complex supports size variation for juvenile Chinook salmon (Oncorhynchus tshawytscha)

Population diversity is a mechanism for resilience and has been identified as a critical issue for fisheries management, but restoration ecologists lack evidence for specific habitat features or processes that promote phenotypic diversity. Since habitat complexity may affect population diversity, it is important to understand how population diversity is partitioned across landscapes and among populations. In this study, we examined life history diversity based on size distributions of juvenile Central Valley Chinook salmon (Oncorhynchus tshawytscha) within the Yolo Bypass, a remnant transitional habitat from floodplain to tidal sloughs in the upper San Francisco Estuary (SFE). We used a generalized least squares model with an autoregressive (AR1) correlation structure to describe the distribution of variation in fish size from 1998 to 2014, and tested the effect of two possible drivers of the observed variation: (i) environmental/seasonal drivers within the Yolo Bypass, and (ii) the juvenile Chinook source population within the Sacramento River and northern SFE. We found that the duration of floodplain inundation, water temperature variation, season, and sampling effort influenced the observed time‐specific size distribution of juvenile Chinook salmon in the Yolo Bypass. Given the lack of seasonally inundated habitat and low thermal heterogeneity in the adjacent Sacramento River, these drivers of juvenile size diversification are primarily available to salmon utilizing the Yolo Bypass. Therefore, enhancement of river floodplain‐tidal slough complexes and inundation regimes may support the resilience of imperiled Central Valley Chinook salmon.