Nesting interactions of the social wasp Dolichovespula saxonica [F.] (Hymenoptera: Vespinae) in wooden nest boxes for birds in the forest reserve „Las Piwnicki” in the Chełmno Land (Northern Poland)

The aim of this research was to investigate the process of colonization in wooden nest boxes for birds by the wasp Dolichovespula saxonica [F.] in the forest reserve “Las Piwnicki” during 1986-1987. About 69% of 150 nest boxes were colonized (36% by D. saxonica) in 1986 and 35% (10% by D. saxonica) in 1987. Parasite Shecophaga vesparum Court was observed inside small cell nests (SC) and large cell nests (LC) in the ratio of 5(SC) : 3(LC). During the two seasons, the decrease in the number of parasited nests followed with the ratio of 10(1986) : 1(1987). Competition of the „wasp - wasp” type (VV) compared to other competition types, such as „wasp - bird” (VA) and different types with wasps (DT), was the most frequent one among the interactions and followed with the ratio 1(VV) : 7(VA) : 5(DT). The number and proportions of construction types of nests during the studied growing seasons seem to prove the regular and irregular development of the Dolichovespula saxonica colony

PHENOLOGY OF SOCIAL WASPS (HYMENOPTERA: VESPINAE) IN THE KUJAWY REGION (NORTHERN POLAND) UNDER THE INFLUENCE OF CLIMATIC CHANGES 1981–2000

Duration of flight periods were determined for most numerous species of social wasps for two decades 1981–1990 and 1991–2000. The tendency to shorten the duration of wasps’ flight periods by 12–18% was observed during 1990s. An attempt was undertaken to associate this phenomenon with observed climatic changes that shape nutritional resources of Vespinae.

Rising temperatures advance the main flight period of Bombus bumblebees in agricultural landscapes of the Central European Plain

Funder: Poznan University of Life SciencesAbstractThis study examined shifts over a 35-year period in the phenology of the four most important bumblebee species (Bombus terrestris, B. lapidarius, B. pascuorum and B. hortorum) in Central Europe. The species showed similar temporal trends, significantly advancing components of their main flight period in association with rising temperatures such that, for example, mid-dates of the main flight period advanced by 10–23 days over the study period. Drivers of this change differed between the four species. Trends in, and drivers of, the timing of first queens, first workers and first males were less consistent. Aspects of the phenology of the least common species, B. hortorum, were up to a month earlier than the other species and climatic effects less clear cut. There were some suggestions of differences between species trends. These results stress the importance of considering changes and drivers of change for the Bombus family on a species-specific basis with the need to pay more attention to the life history traits of the study organisms.</jats:p

Modulo N Backoff Scheme for Effective QoS Differentiation and Increased Bandwidth Utilization in IEEE 802.11 Networks, Journal of Telecommunications and Information Technology, 2009, nr 2

The paper presents a new modulo N channel access scheme for wireless local area networks (WLANs). The novel solution derives from the distributed coordination function (DCF) of the IEEE 802.11 standard, further elaborated as enhanced distribution channel access (EDCA) by the 802.11e draft specification. The main innovation concerns improvement of the binary exponential backoff scheme used for collision avoidance in 802.11 networks. The most appealing feature of the new modulo N backoff scheme is that it outperforms the original 802.11 solution in terms of channel utilization ratio under any traffic conditions. Furthermore, the modulo N proposal can be naturally augmented with QoS differentiation mechanisms like 802.11e extensions. The prioritized modulo N scheme achieves better throughput-delay characteristics for multimedia traffic when compared with the original 802.11e proposal. At the same time, the new solution retains backward compatibility and includes all features which have made IEEE 802.11 networks extremely popular nowadays

Rising temperatures advance the main flight period of Bombus bumblebees in agricultural landscapes of the Central European Plain

Funder: Poznan University of Life SciencesAbstractThis study examined shifts over a 35-year period in the phenology of the four most important bumblebee species (Bombus terrestris, B. lapidarius, B. pascuorum and B. hortorum) in Central Europe. The species showed similar temporal trends, significantly advancing components of their main flight period in association with rising temperatures such that, for example, mid-dates of the main flight period advanced by 10–23 days over the study period. Drivers of this change differed between the four species. Trends in, and drivers of, the timing of first queens, first workers and first males were less consistent. Aspects of the phenology of the least common species, B. hortorum, were up to a month earlier than the other species and climatic effects less clear cut. There were some suggestions of differences between species trends. These results stress the importance of considering changes and drivers of change for the Bombus family on a species-specific basis with the need to pay more attention to the life history traits of the study organisms.</jats:p

Associate Supervisor

Unlike FDMA or TDMA systems, CDMA is interference limited and has a soft capcity that changes depending on the interference felt at the base station at a given time. Admitting a new call and user movement increases the interference level in the system. Therefore a robust Call Admission and Power Control Mechanism is needed. This thesis discusses the main approaches mentioned in the literature on Call Admission Control and Power Control and analyses two modern solutions, namely the QoS aware Power Control and Handoff Prioritization scheme introduced by [T. Rachidi, A. Y. Elbatji, M. Sebbane, and H. Bouzekri 2004] and the Received Power based simulation model discussed in [A. Capone and S. Redana 2001], in greater detail. Then we proceed to recommend improvements that are then tested in a MATLAB simulation environment. The recommended changes improve the overall dropping and handoff loss probabilities. The impact of the NRT overload mechanism discussed in [T. Rachidi, A. Y. Elbatji, M. Sebbane, and H. Bouzekri 2004] is also investigated. The investigations determined th

Three-dimensional microdistribution of

Despite the worldwide distribution and ecological importance of Chironomus larvae in both freshwater and brackish water ecosystems, patterns of their spatial distribution have been rarely studied. This study was conducted in summer, spring and autumn (2010–2011) in the deep-water zone of the polymictic, strongly eutrophic Vistula Lagoon. Its objective was to test whether temporal changes in density of the larvae affect their horizontal microdistribution and burrowing depth. Horizontal distribution, as inferred from indices of dispersion and patchiness, was density-dependent. The larvae spread more regularly with increasing density. The decreased density was associated with an increase in clustered distribution. The larvae burrowed into sediments up to a depth of 25 cm. The maximum burrowing depth positively correlated with total density, but also depended on the size of the larvae. The smallest individuals (<10 mm) did not occur deeper than 5 cm. Larger larvae were encountered throughout the sediment profile. The largest larvae did not always burrow the deepest. In spring before pupation, the larvae gathered below the sediment surface.The paper focuses on a crucial and overlooked aspect of the ecology of chironomid larvae. Their more regularly distribution was associated with seasonally increased density, and a clustered one with decreased density. The maximum burrowing depth (up to 25 cm) positively correlated with total density, but also depended on the size of the larvae

A common error in calculating density of invertebrates in sediment core sections of unequal lengths

In benthic studies, an absolute measure of invertebrate density with depth in the sediment is desirable. It can be expressed as invertebrates per unit of sediment volume or invertebrates per unit of sediment surface area. Calculations are often distorted, however, by whether the core is divided into unequal or equal segments. This is demonstrated in a study conducted in the Vistula Lagoon (South Baltic Sea). We collected 30 cores, and performed an analysis of distribution of invertebrates along the sediment profiles divided into sections of different lengths, or of equal lengths. In both cases, animal density/biomass was calculated both per unit area (m2) and per unit volume (L). When cores are divided into equal sections, various ways of data computing do not affect the final results. If, for any reason, the cores are divided into sections varying in length, the only way to obtain an accurate measure of invertebrate distribution in the sediment profile is to express the data per unit volume. In many studies, calculations have been made per unit area using unequal segments, and these calculations are erroneous. The same error is made if density is expressed as the percentage contribution of the numbers/biomass or number of specimens recorded in particular unequal sections.The study shows that for sediment core sections of unequal lengths (which is frequently the case because researchers expect higher variability in the surface layers compared to the deeper ones), the only correct approach is to express all density measurements per unit volume (not area). Given the high number of studies using incorrect calculations, the study paves the way for better practices in benthic sampling