Seed-bank properties of an Appalachian sphagnum bog and a model of the depth distribution of viable seeds

1987 ◽  
Vol 65 (10) ◽  
pp. 2028-2035 ◽  
Author(s):  
James B. McGraw
Keyword(s):  
Depth Profile ◽  
Seed Bank ◽  
Soil Surface ◽  
High Elevation ◽  
Seed Rain ◽  
Historical Change ◽  
Seed Burial ◽  
Depth Profiles ◽  
A Minor ◽  
Sphagnum Bog

Seed banks were examined in four plant communities in a high-elevation sphagnum bog in West Virginia, U.S.A. A germination assay was used to detect germinable seed densities. Vertical depth distributions were determined for one community in which the soil cores were transported intact to the greenhouse. Seed densities ranged from 12 874 in a Sphagnum-dominated community to 377 041 seeds m−2 in a sedge-dominated community. The seed bank in all communities was dominated numerically by Juncus effusus, although this species comprised a minor part of the aboveground vegetation. Three types of depth profiles were observed, including one distribution showing a simple decline in seed numbers with depth, another showing a unimodal peak below the soil surface, and a third with two distinct peaks at depth. A matrix model of seed burial was devised to account for the different depth profiles. By assuming that soil compression occurred and that the rate of compression declined with time, the model showed that either of the first two depth profiles could be produced with no need to invoke a historical change in the seed rain. The model was unable to account for the bimodal depth profile with the assumption of a constant seed rain. However, the fact that the model of seed burial could explain a unimodal peak in the depth profile suggests that simple historical interpretations of past abundance using a buried seed profile are difficult.

Effects of Soil Texture and Seed Placement on Emergence of Four Subshrubs

Weed Science ◽  
1983 ◽  
Vol 31 (3) ◽  
pp. 380-384 ◽  
Author(s):  
H. S. Mayeux
Keyword(s):  
Seed Bank ◽  
Soil Texture ◽  
Seedling Emergence ◽  
Soil Surface ◽  
Seed Burial ◽  
Seed Placement ◽  
Buried Seed ◽  
Rate Of Emergence ◽  
Gutierrezia Sarothrae

Seedling emergence of broom snakeweed [Gutierrezia sarothrae(Pursh) Britt. & Rusby], threadleaf snakeweed [G. microcephala(DC.) Gray], common goldenweed [Isocoma coronopifolia(Gray) Greene], and false broomweed (Ericameria austrotexanaM.C. Johnston) was studied in the glasshouse. Germination of these species is known to be light-stimulated. Seed of all four subshrubs germinated readily if placed on the surface or partially pressed into the soil. Emergence was reduced by covering seed with soil to a depth of less than 1 mm. Few seedlings emerged from a depth of 1 cm, and none emerged from a depth of 2 cm. Rate of emergence also decreased with increasing depth of placement. Soil texture had little effect on emergence. Rapid germination on the soil surface is consistent with other aspects of the regenerative strategy of common goldenweed and false broomweed, which do not depend upon a buried seed bank for regeneration. Seed burial probably provides a form of enforced dormancy in the small, long-lived seeds of the two snakeweed species.

A seed trap for monitoring the seed rain in terrestrial communities

1995 ◽  
Vol 73 (5) ◽  
pp. 794-796 ◽  
Author(s):  
Gary W. Schott
Keyword(s):  
Life History ◽  
Seed Bank ◽  
Soil Surface ◽  
Seed Rain ◽  
Andropogon Gerardii ◽  
Sampling Methodology ◽  
Grassland Community ◽  
Species Population ◽  
Seed Trap ◽  
Pvc Pipe

Monitoring the seed rain of a species, population, or community is important to quantify that component of life history that follows anthesis yet precedes establishment in the seed bank or as a seedling. I have developed a unique seed trap that is ideal for monitoring the seed rain of a grassland community. The trap consists of a 10-cm diameter funnel attached by Velcro to one end of a 15-cm long PVC pipe. The trap is sunk into the ground with 1.5–2 cm protruding above the soil surface to prevent soil and ground-dwelling insects from entering the trap. A small cotton bag is attached to the stem of the funnel and acts as the reservoir for trapped seeds. I was able to trap propagules ranging in size from 0.5-mm seeds (Juncus interior) to > 2 cm long awned spikelets (Andropogon gerardii). Because this trap minimizes prédation, is easy to construct and monitor, and is inexpensive, it is superior to traps used by previous researchers. Key words: seed trap, seed rain, sampling methodology.

Weed Seed Pools Concurrent with Corn and Soybean Harvest in Illinois

Weed Science ◽  
2008 ◽  
Vol 56 (4) ◽  
pp. 503-508 ◽  
Author(s):  
Adam S. Davis
Keyword(s):  
Seed Bank ◽  
Soil Seed Bank ◽  
Soil Surface ◽  
Seed Rain ◽  
Weed Seed ◽  
Weed Species ◽  
East Central ◽  
Giant Foxtail ◽  
Central Illinois ◽  
Prickly Sida

At the time of grain harvest, weed seeds can be classed into one of four pools on the basis of dispersal status and location: (1) undispersed, remaining on the mother plant; (2) dispersed in the current year, on the soil surface; (3) dispersed in the current year and collected by harvest machinery; and (4) dispersed in a previous year and persisting within the soil seed bank. Knowledge of the relative sizes of these seed pools for different weed species under different crop environments will be useful for determining the best way to reduce the size of inputs to the soil seed bank. In fall 2004 and fall 2005, four randomly selected commercially managed corn and soybean fields in east-central Illinois were sampled to quantify weed seed pools at time of crop harvest. Thirty randomly located 0.125-m2quadrats were placed within each field, the four seed pools mentioned above were sampled for each quadrat, and the species composition and abundance of each seed pool was determined. The magnitude of the weed seed rain varied among species and between years and crops. Twenty-six weed species were found to contribute to at least one of the four seed pools. However, the weed seed pools were consistently dominated by six species: velvetleaf,Amaranthuscomplex (redroot pigweed and waterhemp), ivyleaf morningglory, giant foxtail, prickly sida, and common cocklebur. For each of these species, the ratio of undispersed seeds to seeds in the soil seed bank at harvest time was ≥ 1 in at least one crop during one of the two experimental years, indicating a potential for the soil seed bank to be completely replenished or augmented by that year's seed rain. This analysis demonstrates the urgent need for techniques to limit weed seed inputs to the soil seed bank at the end of the growing season.

scholarly journals Influence of Slope Direction on the Soil Seed Bank and Seedling Regeneration of Castanopsis hystrix Seed Rain

Forests ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 500
Author(s):  
Zong Zhao ◽  
Yong Liu ◽  
Hongyan Jia ◽  
Wensheng Sun ◽  
Angang Ming ◽  
...  
Keyword(s):  
Seed Bank ◽  
Temporal Dynamics ◽  
Soil Seed Bank ◽  
Soil Layer ◽  
Seed Rain ◽  
Seed Vigor ◽  
Study Results ◽  
The Impact ◽  
Mature Seeds

Objective: To investigate the impact of different slope directions on the quantity and quality of the soil seed bank and seedling germination process of Castanopsis hystrix plantations. Method: Fixed sample plots in forest stands of Castanopsis hystrix were established on different slope directions (sunny slope, semi-sunny slope, semi-shady slope, and shady slope). The characteristics of the forest stand were investigated, and per-wood scaling was carried out. The temporal dynamics of the seed rain and seed bank were quantified using seed rain collectors and by collecting soil samples from different depths. The quantity and quality of the seeds were determined, and the vigor of mature seeds was measured throughout the study. Results: (1) The diffusion of Castanopsis hystrix seed rain started in mid-September, reached its peak from late October to early November, and ended in mid-December. (2) The dissemination process, occurrence time, and composition of the seed rain varied between the different slope directions. The seed rain intensity on the semi-sunny slope was the highest (572.75 ± 9.50 grains∙m−2), followed by the sunny slope (515.60 ± 10.28 grains∙m−2), the semi-shady slope (382.13 ± 12.11 grains∙m−2), and finally the shady slope (208.00 ± 11.35 grains∙m−2). The seed rain on the sunny slope diffused earliest and lasted the longest, while the seed rain on the shady slope diffused latest and lasted the shortest time. Seed vigor and the proportion of mature seeds within the seed rain were greatest on the semi-sunny slope, followed by the sunny slope, semi-shady slope, and the shady slope. (3) From the end of the seed rain to August of the following year, the amount of total reserves of the soil seed banks was highest on the semi-sunny slope, followed by the sunny slope then the semi-shady slope, and it was the lowest on the shady slope. The amount of mature, immature, gnawed seeds and seed vigor of the soil seed bank in various slope directions showed a decreasing trend with time. The seeds of the seed bank in all slope directions were mainly distributed in the litter layer, followed by the 0–2 cm humus layer, and only a few seeds were present in the 2–5 cm soil layer. (4) The seedling density of Castanopsis hystrix differed significantly on the different slope directions. The semi-sunny slope had the most seedlings, followed by the sunny slope, semi-shady slope, and the shady slope. Conclusions: The environmental conditions of the semi-sunny slope were found to be most suitable for the seed germination and seedling growth of Castanopsis hystrix, and more conducive to the regeneration and restoration of its population.

Point Contact Current Voltage Measurements of 4H-SiC Samples with Different Doping Profiles

2017 ◽  
Vol 897 ◽  
pp. 287-290 ◽  
Author(s):  
Matthias Kocher ◽  
Michael Niebauer ◽  
Mathias Rommel ◽  
Volker Haeublein ◽  
Anton J. Bauer
Keyword(s):  
Epitaxial Layer ◽  
Depth Profile ◽  
Point Contact ◽  
Surface Preparation ◽  
Epitaxial Layers ◽  
Depth Profiles ◽  
Current Voltage ◽  
Measured Resistance ◽  
Doping Profiles ◽  
Good Agreement

Point contact current voltage (PCIV) measurements were performed on 4H-SiC samples, both for n- an p-doped epitaxial layers as well as samples with rather shallow doping profiles realized by N- or Al-implantation in a range from 1016 cm-3 to 1019 cm-3. Surface preparation and measurement parameters were investigated in order to determine their influence on the measured resistance profiles. Furthermore depth profile measurements were performed on both an epitaxial layer as well as on implanted samples. These depth profiles could be measured reproducibly and showed good agreement with expected profiles for Al-implanted samples as well as for epitaxial layer whereas for N-implanted samples deviations between measured and expected profiles could be observed. It could be proven that PCIV profiling technique is a promising method for characterizing doped profiles in 4H-SiC, especially on Al-implanted samples.

Implantation of Nitrogen into Ti/Al, Ni/Ti, and Ni/Al Bilayers

1991 ◽  
Vol 235 ◽  
Author(s):  
D. O. Boerma ◽  
T. Corts
Keyword(s):  
Nuclear Reaction Analysis ◽  
Si Substrate ◽  
Major Fraction ◽  
High Chemical ◽  
Gaussian Shape ◽  
Depth Profiles ◽  
Implantation Temperature ◽  
Projected Range ◽  
A Minor ◽  
Metal Layers

ABSTRACTTi/Al, Ni/Ti, and Ni/Al bilayers were produced by evaporation on a Si substrate. The thicknesses of the composing layers were in the 50–200 nm range. The as-evaporated bilayers were implanted with doses of 0.4–2.5 · 1017 of 15N ions/cm2. The 15N energy was chosen so that the calculated projected range was either in the middle of the top Ni layer, or coincided with the interface between the metal layers. The implantation temperature was varied in the range from 25 °C to 245 °C. The 15N depth profiles as measured with nuclear reaction analysis (NRA) were found to have the expected Gaussian shape for the Ti/Al bilayers. However, in the Ni/Ti and Ni/Al layers very asymmetric 15N profiles were observed, with a major fraction of N atoms in the Ti or Al layer, and a minor fraction in the Ni layer. The N concentrations in the Al or Ti layers were found to be almost constant. A massive redistribution of N atoms must have taken place in all three metals during the implantations, to form the observed profiles. We speculate that this remarkable phenomenon, which occurs even below 80°C, can be explained by interstitial diffusion of N atoms and subsequent trapping in Ti or Al, which have a high chemical affinity for nitrogen. The N atoms remaining in the Ni layer after implantation were found to migrate out of this layer during annealing at temperatures ≥250°C.

scholarly journals The effect of claying upon the settling of the soil surface on cultivated Sphagnum bogs

1960 ◽  
Vol 32 (1) ◽  
pp. 5-7
Author(s):  
Yrjö Pessi
Keyword(s):  
Soil Surface ◽  
Sphagnum Bogs ◽  
Sphagnum Bog

The present investigation concerns a Sphagnum bog area that has been under cultivation for 35 years. According to the results, the effect of the claying during this time has been the settling of the surface of the soil on an average 12.5 cm more than in unclayed bog.

scholarly journals Implications of the form of the Flow Law for Vertical Velocity and Age–Depth Profiles in Polar Ice

1986 ◽  
Vol 32 (112) ◽  
pp. 366-370 ◽  
Author(s):  
E.W. Wolff ◽  
C.S.M. Doake
Keyword(s):  
Velocity Profile ◽  
Depth Profile ◽  
Vertical Velocity ◽  
Experimental Error ◽  
Ice Sheet ◽  
Polar Ice ◽  
Depth Profiles ◽  
Devon Island ◽  
Vertical Velocity Profile ◽  
Flow Law

AbstractTwo situations are studied in relation to the flow law of polar ice. In each case, models are used with a flow-law exponent of one, and with the more traditional exponent of three. The horizontal velocity profile at Devon Island, Arctic Canada, is better fitted byn= 1; for the vertical velocity profile,n= 3 gives a better fit, but both model profiles fall well within experimental error. For the Camp Century age–depth profile, onlyn= 1 gives an acceptable fit when temperature is allowed for. The large discrepancy between isothermal and non-isothermal models forn= 3 shows the importance of allowing for temperature in studies of ice-sheet properties.

The role of seed bank and seed rain in the recolonization of disturbed sites along an aridity gradient

1993 ◽  
Vol 23 (1-4) ◽  
pp. 561-580 ◽  
Author(s):  
Claus Holzapfel ◽  
Wolfgang Schmidt ◽  
Avishai Shmida
Keyword(s):  
Seed Bank ◽  
Seed Rain ◽  
Aridity Gradient
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