scholarly journals Long-term changes in size and composition of seed bank during succession: from meadow to forest

2014 ◽  
Vol 67 (3-4) ◽  
pp. 301-311 ◽  
Author(s):  
Krystyna Falińska
Keyword(s):  
Seed Bank ◽  
Vegetation Structure ◽  
Canopy Structure ◽  
Spatial Dynamics ◽  
Floristic Composition ◽  
Perennial Herb ◽  
Mirror Reflection ◽  
Seed Migration ◽  
Initial Stage

Studies of the relation between the size and floristic composition of the seed bank and the vegetation during succession were conducted in the years 1976-1996. The results of the research did not confirm the hypothesis of directional changes in the density of seeds as the observed changes were of fluctuating nature. At the start of succession the seed bank was small (2970 seeds/m<sup>2</sup>), and in subsequent years the density of seeds increased successively to reach the highest level after 15 years (9170/m<sup>2</sup> ), then dropped again. After 20 years the density of seeds reached the value recorded at the initial stage (2468/m<sup>2</sup>). Successional changes in floristic richness of seed bank were directional with the number of species falling from 52 to 24. All data indicate that the floristic composition of the seed bank is not a mirror reflection of the vegetation structure, but rather a record of a long-term turnover of species and many different events which in various periods of time influenced the inflow of seeds to the soil (spatial dynamics of the necromass, perennial herb and willow canopy structure, seed migration).

Effect of hydroperiod on seed-bank composition in semipermanent prairie wetlands

1989 ◽  
Vol 67 (3) ◽  
pp. 856-864 ◽  
Author(s):  
Karen A. Poiani ◽  
W. Carter Johnson
Keyword(s):  
Seed Bank ◽  
Floristic Composition ◽  
Open Water ◽  
Seed Density ◽  
Prairie Wetlands ◽  
Water Zone ◽  
Significant Difference ◽  
Total Seed ◽  
Frequent Exposure

Bottom samples were collected from two semipermanent prairie wetlands to determine if known hydroperiod differences were reflected in seed-bank composition. Samples were also taken a 2nd year in one wetland to assess between-year variation. Seed density and composition were determined by counting and identifying seedlings that emerged from samples placed in a greenhouse. Most seed-bank characteristics were statistically indistinguishable between wetlands, including floristic composition and total seed density. A significant difference occurred, however, in the relative importance of mudflat annuals and émergents. The mudflat group was much more abundant in the wetland with the shorter hydroperiod (82 vs. 51%). More frequent exposure of the substrate probably yielded greater seed production. Also, a longer hydroperiod depressed seed density in the open water zone (open water zone, 1309 seeds/m2; two emergent zones, 2840 and 9893 seeds/m2). A seed-bank assay may detect subtle hydroperiod differences among wetlands of the same permanence class more quickly and economically than long-term hydrological monitoring. A sharp increase in mudflat seeds in the 2nd year of sampling after a drawdown supports the use of seed banks in determining hydroperiod events in these wetlands.

scholarly journals A Novel Deep Learning Approach for Machinery Prognostics Based on Time Windows

2019 ◽  
Vol 9 (22) ◽  
pp. 4813 ◽  
Author(s):  
Hanbo Yang ◽  
Fei Zhao ◽  
Gedong Jiang ◽  
Zheng Sun ◽  
Xuesong Mei
Keyword(s):  
Time Windows ◽  
Remaining Useful Life ◽  
Sensor Data ◽  
Time Interval ◽  
Kernel Module ◽  
Initial Stage ◽  
Research Task ◽  
Consecutive Time ◽  
Useful Life

Remaining useful life (RUL) prediction is a challenging research task in prognostics and receives extensive attention from academia to industry. This paper proposes a novel deep convolutional neural network (CNN) for RUL prediction. Unlike health indicator-based methods which require the long-term tracking of sensor data from the initial stage, the proposed network aims to utilize data from consecutive time samples at any time interval for RUL prediction. Additionally, a new kernel module for prognostics is designed where the kernels are selected automatically, which can further enhance the feature extraction ability of the network. The effectiveness of the proposed network is validated using the C-MAPSS dataset for aircraft engines provided by NASA. Compared with the state-of-the-art results on the same dataset, the prediction results demonstrate the superiority of the proposed network.

Studies on the control of water-dropwort (Oenanthe pimpinelloides) in South Australia

1995 ◽  
Vol 35 (4) ◽  
pp. 483
Author(s):  
GJ Mitchell ◽  
RJ Carter ◽  
SR Chinner
Keyword(s):  
Stem Elongation ◽  
South Australia ◽  
Perennial Herb ◽  
Metsulfuron Methyl ◽  
Rate Of Spread ◽  
Herbicide Treatments ◽  
Direct Drilling ◽  
Water Dropwort

Water-dropwort (Oenanthe pimpinelloides L.), a tuberous perennial herb, is currently known in South Australia from only a single locality in the Mount Lofty Ranges. There is little information on water-dropwort control, and 2 experiments were conducted to assess the effects of sowing pasture, with or without presowing herbicides, on the control of this weed. Phalaris (Phalaris aquatica L.) and perennial clovers were successfully introduced into infested pastures by direct drilling in autumn. Water-dropwort regenerated from seed more densely in unsown plots than plots of established perennial pasture, suggesting that upgrading pastures may be a strategy to reduce the rate of spread by seed of this weed. A range of herbicide treatments applied to waterdropwort at the stem elongation stage in spring before autumn sowing of pastures provided effective shortterm control. The best short-term control was provided by glyphosate at 1440 g a.i./ha; metsulfuron methyl at 6, 12, and 36 g a.i./ha; and metsulfuron methyl at 12 g a.i./ha tank-mixed with glyphosate or 2,4-D amine at 720 or 1000 g a.i./ha, respectively. These treatments, and chlorsulfuron at 21 g a.i./ha, also significantly (P<0.05) reduced water-dropwort abundance (relative to untreated areas) for up to 18 months after sowing and initially improved the density of sown pasture species, but these improvements were not evident 14 months after resowing. Although prior season herbicide treatments controlled water-dropwort in newly sown pastures, 2 separate applications of herbicides, in May and October, gave no better control of water-dropwort than a single herbicide application in spring. Water-dropwort infestations do not appear to prevent successful direct drilling of phalaris and perennial clovers. Although pasture renovation did not provide long-term suppression of water-dropwort, the maintenance of vigorous pastures may reduce the rate of population growth from seedlings of this weed. Recropping restrictions may limit the role of chlorsulfuron for water-dropwort control in pasture renovation situations.

scholarly journals FCCSP IMC growth under reliability stress follows automotive criteria

2019 ◽  
Vol 3 (1) ◽  
pp. 70-83
Author(s):  
Wei Wei Liu ◽  
Berdy Weng ◽  
Scott Chen
Keyword(s):  
High Temperature ◽  
Flip Chip ◽  
Stress Test ◽  
Temperature Cycling ◽  
Content Type ◽  
Initial Stage ◽  
High Temperature Storage ◽  
Temperature Cycling Test ◽  
Temperature Storage

Purpose The Kirkendall void had been a well-known issue for long-term reliability of semiconductor interconnects; while even the KVs exist at the interfaces of Cu and Sn, it may still be able to pass the condition of unbias long-term reliability testing, especially for 2,000 cycles of temperature cycling test and 2,000 h of high temperature storage. A large number of KVs were observed after 200 cycles of temperature cycling test at the intermetallic Cu3Sn layer which locate between the intermetallic Cu6Sn5 and Cu layers. These kinds of voids will grow proportional with the aging time at the initial stage. This paper aims to compare various IMC thickness as a function of stress test, the Cu3Sn and Cu6Sn5 do affected seriously by heat, but Ni3Sn4 is not affected by heat or moisture. Design/methodology/approach The package is the design in the flip chip-chip scale package with bumping process and assembly. The package was put in reliability stress test that followed AEC-Q100 automotive criteria and recorded the IMC growing morphology. Findings The Cu6Sn5 intermetallic compound is the most sensitive to continuous heat which grows from 3 to 10 µm at high temperature storage 2,000 h testing, and the second is Cu3Sn IMC. Cu6Sn5 IMC will convert to Cu3Sn IMC at initial stage, and then Kirkendall void will be found at the interface of Cu and Cu3Sn IMC, which has quality concerning issue if the void’s density grows up. The first phase to form and grow into observable thickness for Ni and lead-free interface is Ni3Sn4 IMC, and the thickness has little relationship to the environmental stress, as no IMC thickness variation between TCT, uHAST and HTSL stress test. The more the Sn exists, the thicker Ni3Sn4 IMC will be derived from this experimental finding compare the Cu/Ni/SnAg cell and Ni/SnAg cell. Research limitations/implications The research found that FCCSP can pass automotive criteria that follow AEC-Q100, which give the confidence for upgrading the package type with higher efficiency and complexities of the pin design. Practical implications This result will impact to the future automotive package, how to choose the best package methodology and what is the way to do the package. The authors can understand the tolerance for the kind of flip chip package, and the bump structure is then applied for high-end technology. Originality/value The overall three kinds of bump structures, Cu/Ni/SnAg, Cu/SnAg and Ni/SnAg, were taken into consideration, and the IMC growing morphology had been recorded. Also, the IMC had changed during the environmental stress, and KV formation was reserved.

scholarly journals Crop rotation and tillage system on the Italian ryegrass seed bank after long-term field management

2021 ◽  
Vol 78 (5) ◽  
Author(s):  
André Guareschi ◽  
Joanei Cechin ◽  
Mario Antonio Bianchi ◽  
Ivan Carlos Maldaner ◽  
Sergio Luiz de Oliveira Machado
Keyword(s):  
Crop Rotation ◽  
Seed Bank ◽  
Italian Ryegrass ◽  
Field Management ◽  
Tillage System ◽  
Term Field

scholarly journals Floristic composition and taxonomic structure of algae in the hyperhaline reservoirs of the northwestern Azov Sea coast (Ukraine)

Algologia ◽  
2020 ◽  
Vol 30 (4) ◽  
pp. 393-405
Author(s):  
A.M. Solonenko ◽  
◽  
O.G. Bren ◽  
Keyword(s):  
Water Exchange ◽  
Salt Water ◽  
Floristic Composition ◽  
Hydrological Regime ◽  
Taxonomic Structure ◽  
Azov Sea ◽  
The Family ◽  
Saline Habitats ◽  
Saline Land

The article represents the results of long-term algological studies of hyperhaline reservoirs of the northwestern coast of the Azov Sea. The features of the floristic composition and taxonomic structure of algae in aquatic (water column and bottom), aquatic-terrestrial (water’s edge, dried up water bodies, drying area) and terrestrial (elevated non-flooding areas) habitats of these objects are displayed. A specificity of the studied algoflora lies in the absence of representatives of certain characteristic phyla for the salt-water and non-saline land and water habitats of the territory of Ukraine. It was established that species composition of the studied reservoirs is depleted in comparison with other non-saline and marine ecosystems. Totally, 123 algae species were identified. They represente 7 phyla, 10 classes, 27 orders, 47 families, 68 genera. The largest number of species included three phyla: Cyanoprocaryota – 65 species (52.9% of the total number of identified species), Bacillariophyta – 26 (21.1%), Chlorophyta – 22 (17.9%). The first places among the six leading orders were taken by cyanoprocaryotes from Oscillatoriales, Nostocales, Chroococcales and diatoms from Naviculales. The most numerous species at the family level are trichomous cyanoprocaryotes from Nostocaceae, Pseudanabaenaceae, and Phormidiaceae. There were found 23 leading genera – their species richness exceeds the average indicator (1.81 species). According to the results of original studies, it was noted that all taxonomic levels of algoflora of the hyperhaline reservoirs shows features of not only saline habitats, but also of the freshwater, marine and terrestrial extreme ecosystems. Such diversity of the algal population indicates an unstable hydrological regime and complex relations of water exchange between the hyperhaline reservoirs and nearby terrestrial and aquatic habitats.

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