In-Network Congestion Control for Multirate Multicast

We present a novel control scheme that dynamically optimizes multirate multicast. By computing the differential backlog at every node, our scheme adaptively allocates transmission rates per session/user pair in order to maximize throughput. An important feature of the proposed scheme is that it does not require source cooperation or centralized calculations. This methodology leads to efficient and distributed algorithms that scale gracefully and can be embraced by low-cost wireless devices. Additionally, it is shown that maximization of sum utility is possible by the addition of a virtual queue at each destination node of the multicast groups. The virtual queue captures the desire of the individual user and helps in making the correct resource allocation to optimize total utility. Under the operation of the proposed schemes backlog sizes are deterministically bounded, which provides delay guarantees on delivered packets. To illustrate its practicality, we present a prototype implementation in the NITOS wireless testbed. The experimental results verify that the proposed schemes achieve maximum performance while maintaining low complexity.National Science Foundation (U.S.) (grant CNS-0915988)National Science Foundation (U.S.) (grant CNS-1116209)United States. Office of Naval Research (grant N00014-12-1-0064

Bandwidth allocation in cooperative wireless networks: Buffer load analysis and fairness evaluation.

In modern cooperative wireless networks, the resource allocation is an issue of major significance. The cooperation of source and relay nodes in wireless networks towards improved performance and robustness requires the application of an efficient bandwidth sharing policy. Moreover, user requirements for multimedia content over wireless links necessitate the support of advanced Quality of Service (QoS) features. In this paper, a novel bandwidth allocation technique for cooperative wireless networks is proposed, which is able to satisfy the increased QoS requirements of network users taking into account both traffic priority and packet buffer load. The performance of the proposed scheme is examined by analyzing the impact of buffer load on bandwidth allocation. Moreover, fairness performance in resource sharing is also studied. The results obtained for the cooperative network scenario employed, are validated by simulations. Evidently, the improved performance achieved by the proposed technique indicates that it can be employed for efficient traffic differentiation. The flexible design architecture of the proposed technique indicates its capability to be integrated into Medium Access Control (MAC) protocols for cooperative wireless networks

Forest vegetation units of Paiko massif and their evaluation from a reforestation aspect

Στην παρούσα έρευνα, μελετήθηκε φυτοκοινωνιολογικά, με την μέθοδο του Braun-Blanquet (1951, 1964), η δασική βλάστηση του όρους Πάικου. Διενεργήθηκαν συνολικά 259 φυτοληψίες. Με τη μέθοδο της επεξεργασίας των φυτοληψιών σε φυτοπίνακες με το χέρι (manual table method), διακρίθηκαν φυτοκοινωνικές μονάδες διάφορης ιεραρχικής ταξινόμισης. Για την διερεύνηση των εδαφικών συνθηκών του σταθμού και τον προσδιορισμό της σχέσης τους με τη βλάστηση, διενεργήθηκαν 19 εδαφοτομές. Μετά την τελική επεξεργασία και την συνταξινόμιση, οι φυτοκοινωνικές μονάδες που προέκυψαν είναι τρεις κλάσεις, τρεις τάξεις, πέντε συνενώσεις, τέσσερεις ενώσεις, εννέα κοινότητες, τέσσερεις υποενώσεις, έντεκα υποκοινότητες, δεκατρείς παραλλαγές και δεκαεννέα όψεις. Η συνταξινόμιση των ενώσεων, κοινοτήτων, υποενώσεων και υποκοινοτήτων παρατίθεται στη συνέχεια: Κλάση: Quercetea pubescentis Doing-Kraft ex Scamoni et Passarge 1959 Τάξη: Quercetalia pubescentis Br.-Bl. 1931 Koινότητα: Quercus pubescens-κοινότητα Συνένωση: Ostryo - Carpinion orientalis Horvat 1959 Κοινότητα: Quercus coccifera - Juniperus oxycedrus ssp. oxycedrus-κοινότητα Κοινότητα: Carpinus orientalis-κοινότητα Υποκοινότητα με Quercus coccifera Τυπική υποκοινότητα Κοινότητα: Ostrya carpinifolia-κοινότητα Υποκοινότητα με Pistacia terebinthus Τυπική υποκοινότητα Συνένωση: Quercion confertae Horvat ex Horvat 1958 Ένωση: Quercetum frainetto Dafis 1966 Υποένωση: Quercetum frainetto genistetosum carinalis subass. nov. Υποένωση: Quercetum frainetto typicum Κοινότητα: Quercus petraea ssp. medwediewii-κοινότητα Υποκοινότητα με Quercus frainetto Yποκοινότητα με Fagus sylvatica ssp. sylvatica Τυπική υποκοινότητα Κοινότητα: Castanea sativa-κοινότητα Τυπική υποκοινότητα Υποκοινότητα με Fagus sylvatica ssp. sylvatica Κλάση: Querco - Fagetea Br.-Bl. et Vlieger in Vlieger 1937 Τάξη: Fagetalia sylvaticae Pawlovski 1928 Συνένωση: Tilio - Acerion Klika 1955 Κοινότητα: Acer platanoides - Ulmus glabra-κοινότητα Συνένωση: Fagion sylvaticae Luquet 1926 Υποσυνένωση: Doronico columnae - Fagenion moesiacae Dzwonko et al.1999 Ένωση: Οrthilio secundae - Fagetum (Barbero et Quezel 1976) Bergmeier 90 Κοινότητα: Fagus sylvatica ssp. sylvatica-κοινότητα Κοινότητα: Epilobium montanum - Fagus sylvatica ssp. sylvatica-κοινότητα Τυπική υποκοινότητα Υποκοινότητα με Geranium robertianum Υποσυνένωση: Doronico orientalis - Fagenion moesiacae Raus 1980 Ενωση: Lathyro alpestris - Fagetum Bergmeier 1990 Yποένωση: Lathyro alpestris - Fagetum typicum Υποένωση: Lathyro alpestris - Fagetum aceretosum opali subass.nov. Κλάση: Populetea albae Br-Bl. 1962 Τάξη: Populetalia albae Br.-Bl. 1931 ex auct (in Br.-Bl. 1931 non valid publ.) Συνένωση: Populion albae Br.-Bl. 1931 ex auct (in Br.-Bl. 1931 non valid publ.) Ένωση: Equiseto telmateiae - Platanetum orientalis Bergmeier 1990In the present study the forest vegetation of Paiko massif (northcentral Greece) was investigated phytosociologicaly, using the Braun-Blanquet (1951, 1964) method. A total amount of 259 releves were carried out. The releves were analysed in phytosociological tables by manual table method and phytosociological units of several syntaxinomic rank were discerned. For the investigation of the soil conditions of the site and the determination of soil relation with vegetation, 19 soil profiles were elaborated. The phytosociological units which resulted from the final analytical tables and syntaxonomy procedure consist of three classes, three orders, five alliances, four associations, nine communities, four subassociations, eleven subcommunities, thirteen varieties and nineteen facies. The syntaxonomy of the associations, communities, subassociations and subcommunities is the following: Class: Quercetea pubescentis Doing-Kraft ex Scamoni et Passarge 1959 Order: Quercetalia pubescentis Br.-Bl. 1931 Community: Quercus pubescens-comm. Alliance: Ostryo - Carpinion orientalis Horvat 1959 Community: Quercus coccifera - Juniperus oxycedrus ssp. oxycedrus-comm. Community: Carpinus orientalis-comm. Subcommunity with Quercus coccifera Typical subcommunity Community: Ostrya carpinifolia-comm Subcommunity with Pistacia terebinthus Typical subcommunity Alliance: Quercion confertae Horvat ex Horvat 1958 Association: Quercetum frainetto Dafis 1966 Subassociation: Quercetum frainetto genistetosum carinalis subass. nov. Subassociation: Quercetum frainetto typicum Community: Quercus petraea ssp. medwediewii-comm. Subcommunity Quercus frainetto Subcommunity with Fagus sylvatica ssp. sylvatica Typical subcommunity Community: Castanea sativa-comm. Typical subcommunity Subcommunity with Fagus sylvatica ssp. sylvatica Class: Querco - Fagetea Br.-Bl. et Vlieger in Vlieger 1937 Order: Fagetalia sylvaticae Pawlovski 1928 Alliance: Tilio - Acerion Klika 1955 Community: Acer platanoides - Ulmus glabra-comm. Alliance: Fagion sylvaticae Luquet 1926 Suballiance: Doronico columnae - Fagenion moesiacae Dzwonko et al.1999 Association: Οrthilio secundae-Fagetum (Barbero et Quezel 1976) Bergm. 90 Community: Fagus sylvatica ssp. sylvatica-comm. Community: Epilobium montanum - Fagus sylvatica ssp. sylvatica-comm. Typical subcommunity Subcommunity with Geranium robertianum Suballiance: Doronico orientalis - Fagenion moesiacae Raus 1980 Association: Lathyro alpestris - Fagetum Bergmeier 1990 Subassociation: Lathyro alpestris - Fagetum typicum Subassociation: Lathyro alpestris - Fagetum aceretosum opali subass.nov. Class: Populetea albae Br-Bl. 1962 Order: Populetalia albae Br.-Bl. 1931 ex auct (in Br.-Bl. 1931 non valid publ.) Alliance: Populion albae Br.-Bl. 1931 ex auct (in Br.-Bl. 1931 non valid publ.) Association: Equiseto telmateiae - Platanetum orientalis Bergmeier 199

Soil Properties and Plant Community Changes along a Goat Grazing Intensity Gradient in an Open Canopy Oak Forest

Understanding how the management practices of silvopastoral systems affect the long-term sustainability of oak ecosystems and what their influence is on nutrient cycling and plant community, is of great interest. The aim of this study was to examine the effects of relative grazing intensity on soil properties and on vegetation characteristics in an open canopy oak forest dominated by Quercus frainetto. The research was conducted in the area of Pentalofos, which is located in Evros region, north-eastern Greece and is grazed by goats. The distance from a goat corral was used to represent relative grazing intensity. In June 2011, soil and vegetation samples were collected along transects placed at 50, 150, 300, 600 and 1200 m from the goat corral, running perpendicular to three replicates. Soil measurements included pH, phosphorous (P) and nitrogen (N) concentrations while vegetation measurements included plant cover, species composition and diversity. Plant cover was not significantly different among grazing intensities. Species diversity, especially of the woody vegetation layer, was significantly higher in the light grazing intensity in comparison to both the heavy and the very light grazing. Heavy grazing reduced soil organic matter while it increased total nitrogen. Grazing intensity did not affect available P and soil pH. Light to moderate goat grazing could ameliorate floristic diversity and increase sustainability of oak forests in the Mediterranean region

Soil Properties and Plant Community Changes along a Goat Grazing Intensity Gradient in an Open Canopy Oak Forest

Understanding how the management practices of silvopastoral systems affect the long-term sustainability of oak ecosystems and what their influence is on nutrient cycling and plant community, is of great interest. The aim of this study was to examine the effects of relative grazing intensity on soil properties and on vegetation characteristics in an open canopy oak forest dominated by Quercus frainetto. The research was conducted in the area of Pentalofos, which is located in Evros region, north-eastern Greece and is grazed by goats. The distance from a goat corral was used to represent relative grazing intensity. In June 2011, soil and vegetation samples were collected along transects placed at 50, 150, 300, 600 and 1200 m from the goat corral, running perpendicular to three replicates. Soil measurements included pH, phosphorous (P) and nitrogen (N) concentrations while vegetation measurements included plant cover, species composition and diversity. Plant cover was not significantly different among grazing intensities. Species diversity, especially of the woody vegetation layer, was significantly higher in the light grazing intensity in comparison to both the heavy and the very light grazing. Heavy grazing reduced soil organic matter while it increased total nitrogen. Grazing intensity did not affect available P and soil pH. Light to moderate goat grazing could ameliorate floristic diversity and increase sustainability of oak forests in the Mediterranean region

Predicting Tree Species Diversity Using Geodiversity and Sentinel-2 Multi-Seasonal Spectral Information

Measuring and monitoring tree diversity is a prerequisite for altering biodiversity loss and the sustainable management of forest ecosystems. High temporal satellite remote sensing, recording difference in species phenology, can facilitate the extraction of timely, standardized and reliable information on tree diversity, complementing or replacing traditional field measurements. In this study, we used multispectral and multi-seasonal remotely sensed data from the Sentinel-2 satellite sensor along with geodiversity data for estimating local tree diversity in a Mediterranean forest area. One hundred plots were selected for in situ inventory of tree species and measurement of tree diversity using the Simpson’s (D1) and Shannon (H′) diversity indices. Four Sentinel-2 scenes and geodiversity variables, including elevation, aspect, moisture, and basement rock type, were exploited through a random forest regression algorithm for predicting the two diversity indices. The multi-seasonal models presented the highest accuracy for both indices with an R2 up to 0.37. In regard to the single season, spectral-only models, mid-summer and mid-autumn model also demonstrated satisfactory accuracy (max R2 = 0.28). On the other hand, the accuracy of the spectral-only early-spring and early-autumn models was significant lower (max R2 = 0.16), although it was improved with the use of geodiversity information (max R2 = 0.25)

Retrieval of Leaf Area Index Using Sentinel-2 Imagery in a Mixed Mediterranean Forest Area

Leaf area index (LAI) is a crucial biophysical indicator for assessing and monitoring the structure and functions of forest ecosystems. Improvements in remote sensing instrumental characteristics and the availability of more efficient statistical algorithms, elevate the potential for more accurate models of vegetation biophysical properties including LAI. The aim of this study was to assess the spectral information of Sentinel-2 MSI satellite imagery for the retrieval of LAI over a mixed forest ecosystem located in northwest Greece. Forty-eight field plots were visited for the collection of ground LAI measurements using an ACCUPAR LP-80: PAR & LAI Ceptometer. Spectral bands and spectral indices were used for LAI model development using the Gaussian processes regression (GPR) algorithm. A variable selection procedure was applied to improve the model’s prediction accuracy, and variable importance was investigated for identifying the most informative variables. The model resulting from spectral indices’ variables selection produced the most precise predictions of LAI with a coefficient of determination of 0.854. Shortwave infrared bands and the normalized canopy index (NCI) were identified as the most important features for LAI prediction

Fine-Scale Spatial Patterns of the Genetic Diversity ofEuropean Beech (Fagus sylvatica L.) around a Mountainous Glacial Refugium in the SW Balkans

Beech (Fagus sylvatica L.) is one of the most important forest trees in Europe and its current broad expanse over the continent is believed to be the outcome of the Holocene postglacial expansion of lineages originating from different glacial refugia. Studies using gene markers, pollen profiles and fossils suggest the main locations of glacial refugia in Southern Europe. In this study, we conduct a fine-scale genetic study on the beech populations surrounding the Almopia basin, an area that is said to have hosted one of the main European glacial refugia for several plant and animal species during the Pleistocene Epoch. We test the hypothesis of the existence of a local refugium in the study area for beech to understand the spatial genetic pattern of the putative refugial beech populations in the area and to investigate possible genetic connections between the local beech populations and the European expansion of the species. The genetic diversity of 100 sampled trees in 20 plots representing the expansion of beech in the area was studied using chloroplast and nuclear DNA microsatellites (cpSSR and nSSR, respectively). All three cpSSR regions were polymorphic, resulting in eight haplotypes, separated spatially in two distinct groups (one on the western and the other on the eastern part of the Almopia basin) that correspond to two different postglacial beech lineages. Furthermore, the cpSSR sequences of the eastern lineage are genetically identical to those of beech populations extending over central and northern Europe. The nSSR markers were highly polymorphic, and the trees studied were separated into two genetic groups that coincided with the cpSSR ones in locations where the topography is more pronounced. These results indicated that the Almopia region was indeed a major refugium for beech that possibly produced two main postglacial lineages for Europe, one of which is connected with the majority of beech populations growing on the continent. These southern refugial populations are important diversity centers that need to be the subject of special management and conservation