Differences in reproductive effort and sexual recruitment of the seagrass Zostera japonica between two geographic populations in northern China

2020 ◽  
Vol 638 ◽  
pp. 65-81 ◽  
Author(s):  
X Zhang ◽  
Y Zhou ◽  
S Xu ◽  
P Wang ◽  
P Zhao ◽  
...  
Keyword(s):  
Seed Bank ◽  
Seedling Recruitment ◽  
Survey Methods ◽  
Clonal Diversity ◽  
Northern China ◽  
Microsatellite Analysis ◽  
Northwestern Pacific ◽  
Zostera Japonica ◽  
Sexual And Asexual Reproduction ◽  
Local Recruitment

Coastal seagrass beds are pivotal but threatened marine ecosystems throughout the world. The seagrass Zostera japonica Asch. & Graebn. is an endangered species in its native range along the northwestern Pacific coast. In this study, we used ecological survey methods and microsatellite analysis to evaluate sexual reproduction and its role in recruitment of Z. japonica populations at Swan Lake lagoon (SLL) and Huiquan Bay (HQB) in northern China. Mixed annual and continuous meadows of Z. japonica at SLL produced a high number of seeds (mean ± SD: 40244 ± 18666 seeds m-2) and formed a relatively stable seed bank (1460 ± 417 seeds m-2) in the sediment. About 41% of the seed bank and 6% of shoots survived over winter, and recruitment from seeds accounted for 41 ± 24%. In contrast, perennial and fragmented Z. japonica at HQB had lower seed production (12501 ± 5748 seeds m-2) and a much smaller seed bank (10 ± 6 seeds m-2). About 66% of shoots survived over winter, but seedling recruitment was rare at HQB. Thus, relatively large differences in genetic and clonal diversity were predicted between SLL and HQB. Results of the microsatellite analysis of samples collected in 2012 and 2015 showed higher clonal (R) and genetic diversity (Ho) at SLL (2015: R = 1; Ho = 0.55) than at HQB (2015: R = 0.40; Ho = 0.42). These results highlight the role of sexual and asexual reproduction in maintenance and evolutionary connectivity of seagrass populations and emphasize the need to understand local recruitment strategies before starting restoration and management projects.

scholarly journals Reproductive Strategies of the Seagrass Zostera japonica Under Different Geographic Conditions in Northern China

2020 ◽  
Vol 7 ◽  
Author(s):  
Shidong Yue ◽  
Xiaomei Zhang ◽  
Shaochun Xu ◽  
Yu Zhang ◽  
Peng Zhao ◽  
...  
Keyword(s):  
Sexual Reproduction ◽  
Asexual Reproduction ◽  
Reproductive Strategies ◽  
Geographic Location ◽  
Dry Weight ◽  
Northern China ◽  
Shoot Density ◽  
Zostera Japonica ◽  
Sexual And Asexual Reproduction ◽  
Density And Biomass

Seagrasses form a unique group of submerged marine angiosperms capable of both sexual and asexual reproduction. The amounts of sexual and asexual reproduction differ within some species relying on geographic location and environmental factors. Here, we studied the reproductive strategies of different geographic Zostera japonica populations, S1 and S2 at Swan Lake lagoon (SLL), and H1 and H2 at Huiquan Bay (HQB), in northern China. The duration of flowering at SLL was longer than at HQB, whereas flowering initiation at HQB occurred earlier than at SLL. In addition, the timing of seed maturation at HQB occurred earlier than at SLL. The allocation to sexual reproduction at SLL was greater than at HQB. The maximum potential seed production was greatest at S1 (22228.52 ± 8832.46 seeds ⋅ m–2), followed by S2 (21630.34 ± 9378.67 seeds ⋅ m–2), H2 (7459.60 ± 1779.33 seeds ⋅ m–2), and H1 (2821.05 ± 1280.57 seeds ⋅ m–2). The seasonal changes in total shoot density and biomass were small at HQB. There was a relatively large number of overwintering shoots at HQB because of the higher average temperature during winter. The allocation to sexual reproduction was lower than at SLL, and no seedlings were observed at HQB during our study. Thus, the population of Z. japonica at HQB was maintained by asexual reproduction. Compared with HQB, the biomass of overwintering shoots at SLL was less than 30 g dry weight ⋅ m–2. The Z. japonica at SLL relied on asexual and sexual reproduction to maintain the population. The results show the necessity of understanding local reproductive strategies before starting restoration and management projects. The study provides fundamental information and guidance for the conservation and restoration of seagrass beds.

scholarly journals Seed bank dynamics in five Panamanian forests

2005 ◽  
Vol 21 (2) ◽  
pp. 223-226 ◽  
Author(s):  
D. A. Fornara ◽  
J. W. Dalling
Keyword(s):  
Seed Bank ◽  
Seedling Recruitment ◽  
Fruit Production ◽  
Pioneer Species ◽  
Seasonal Fluctuations ◽  
Annual Fluctuation ◽  
Soil Seed Banks ◽  
Successful Recruitment ◽  
Seed Bank Dynamics ◽  
Lowland Forests

Many tropical pioneer species depend on the presence of high seed densities in the soil for successful recruitment following canopy disturbance (Cheke et al. 1979, Dalling & Hubbell 2002, Guevara Sada & Gómez Pompa 1972, Whitmore 1983). However determinants of variation in the composition and abundance of soil seed banks remain poorly understood. Seed bank densities can be affected by rates of seed predation and pathogen infection on the surface and in the soil, by intrinsic rates of loss in viability following dispersal, and by variation in the timing and duration of fruit production (Dalling et al. 1997, Garwood 1983, Murray & Garcia 2002). Here we compare seasonal fluctuations in seed bank density in five Panamanian forests varying in elevation and seasonality of precipitation (Table 1). We predict that lowland forests should show stronger intra-annual fluctuation in seed bank densities than montane forests because seed production and loss rates should be higher under conditions of greater resource availability, and where consistent high temperatures support greater abundance or activity of seed predators and pathogens (Brühl et al. 1999). Secondly, among lowland sites, we predict greater fluctuations in seed bank densities at drier, more seasonal sites where seasonally favourable conditions for seedling recruitment may select for interspecific synchrony in fruit production (Daubenmire 1972, Garwood 1983).

Dispersal of Miconia argentea seeds by the leaf-cutting ant Atta colombica

1998 ◽  
Vol 14 (5) ◽  
pp. 705-710 ◽  
Author(s):  
J. W. Dalling ◽  
Rainer Wirth
Keyword(s):  
Seedling Recruitment ◽  
Atta Cephalotes ◽  
Brazilian Cerrado ◽  
Atta Laevigata ◽  
Cerrado Vegetation ◽  
Brosimum Alicastrum ◽  
Leaf Cutting ◽  
Single Night ◽  
Local Recruitment ◽  
Atta Colombica

While leaf-cutter ants are thought to collect mainly vegetative plant material, they have also been observed collecting seeds or fruit parts on the forest floor (Alvarez-Buylla & Martínez-Ramos 1990, Kaspari 1996). For example, leaf-cutter ants have been observed carrying considerable numbers of Brosimum alicastrum Sw. and Cecropia spp. seeds into their nests (Wirth 1996) and Leal & Oliveira (1998; pers. comm.) found them foraging on the fruits and seeds of 19 different species of Brazilian cerrado vegetation, including six Miconia species. Under some circumstances, seed removal and relocation by leaf cutter ants might even be sufficient to affect local recruitment patterns of trees. For example, in Costa Rica, Atta cephalotes can remove all fallen fig fruit from beneath a Ficus hondurensis crown in a single night (Roberts & Heithaus 1986), while in Venezuela, seedling recruitment of the savanna tree Tapirira velutinifolia was positively associated with the seed harvesting and seed cleaning activities of the ant Atta laevigata (Farji Brenner & Silva 1996).

Seed bank and seedling recruitment of endangered Tephroseris longifolia subsp. moravica (Asteraceae)

2016 ◽  
Vol 51 (4) ◽  
pp. 343-360
Author(s):  
Monika Janišová ◽  
Iveta Škodová ◽  
Katarína Hegedüšová ◽  
Judita Kochjarová
Keyword(s):  
Seed Bank ◽  
Seedling Recruitment

scholarly journals Climatological Features of Cutoff Low Systems in the Northern Hemisphere

2005 ◽  
Vol 18 (16) ◽  
pp. 3085-3103 ◽  
Author(s):  
Raquel Nieto ◽  
Luis Gimeno ◽  
Laura de la Torre ◽  
Pedro Ribera ◽  
David Gallego ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Atlantic Coast ◽  
Northern China ◽  
Bimodal Distribution ◽  
Northwestern Pacific ◽  
Subsequent Paper ◽  
Equivalent Thickness ◽  
Thermal Front ◽  
The Third ◽  
Cutoff Low

Abstract This study presents the first multidecadal climatology of cutoff low systems in the Northern Hemisphere. The climatology was constructed by using 41 yr (1958–98) of NCEP–NCAR reanalysis data and identifying cutoff lows by means of an objective method based on imposing the three main physical characteristics of the conceptual model of cutoff low (the 200-hPa geopotential minimum, cutoff circulation, and the specific structure of both equivalent thickness and thermal front parameter fields). Several results were confirmed and climatologically validated: 1) the existence of three preferred areas of cutoff low occurrence (the first one extends through southern Europe and the eastern Atlantic coast, the second one is the eastern North Pacific, and the third one is the northern China–Siberian region extending to the northwestern Pacific coast; the European area is the most favored region); 2) the known seasonal cycle, with cutoff lows forming much more frequently in summer than in winter; 3) the short lifetime of cutoff lows, most cutoff lows lasted 2–3 days and very few lasted more than 5 days; and 4) the mobility of the system, with few cutoff lows being stationary. Furthermore, the long study period has made it possible (i) to find a bimodal distribution in the geographical density of cutoff lows for the European sector in all the seasons (with the exception of winter), a summer displacement to the ocean in the American region, and a summer extension to the continent in the Asian region, and (ii) to detect northward and westward motion especially in the transitions from the second to third day of occurrence and from the third to fourth day of occurrence. The long-term cutoff low database built in this study is appropriate to study the interannual variability of cutoff low occurrence and the links between cutoff lows and jet stream systems, blocking, or major modes of climate variability as well as the global importance of cutoff low in the stratosphere–troposphere exchange mechanism, which will be the focus of a subsequent paper.

Recruitment of Curly Mitchell Grass (Astrebla Lappacea) in North-Western New South Wales.

1996 ◽  
Vol 18 (1) ◽  
pp. 179 ◽  
Author(s):  
MH Campbell ◽  
AM Bowman ◽  
WD Bellotti ◽  
DJ Munich ◽  
HI Nicol
Keyword(s):  
Seed Bank ◽  
Seedling Recruitment ◽  
New South ◽  
Rainfall Events ◽  
South Wales ◽  
Grazing System ◽  
Dry Conditions ◽  
Annual Weeds ◽  
North Western ◽  
Germinable Seed

The recruitment of Astrebla lappacea was studied from 1986 to 1995 in a pasture in north-western NSW where the density of plants had declined from 1 to 3 plants/m2 in 1970 to 0.023 plants/m2 in 1986. Three treatments were imposed: ungrazed-sprayed-slashed, where annual weeds were treated with herbicides and slashing to reduce competition during recruitment; ungrazed-only; and grazed-only. The seed bank of A. lappacea was measured on four occasions and densities of A. lappacea plants determined after major rainfall events mainly in summer and autumn. On the ungrazed treatments the seed bank of A. lappacea increased from 0 in 1988 to 908, 898 and 286 germinable seed/m2 in, respectively, 1992, 1993 and 1995. Flowering and seedling recruitment occurred each year from 1988 to 1995 but seedlings only survived to become mature plants from the 1988 and 1992 recruitments. The major reason for the death of seedlings was dry conditions in the latter half of the year (1 10 to 135 mm of raid6 months). Frosts and competition from Brassicaceae weeds (mainly Raphistrum rugosum) in winter and spring also contributed to death of seedlings. Recruitment of seedlings and their survival to mature plants was higher on the ungrazed-sprayed-slashed treatment than on the other treatments. Recruitment and survival on the ungrazed-only treatment occurred because Brassicaceae weeds did not establish when recruiting rains fell in summer. Plant densit increased from 0.023 plants/m2 in 1986 to, respectively, 0.86, 0.64 Y and 0.004 mature plantdm and 7.88, 6.37, 0.10 seedlings/m2 on the ungrazed-sprayed-slashed, ungrazed-only and grazed-only treatments in 1995. On the grazed-only treatment the methods used to detect seeds revealed none in the soil during the experiment. However, some seeds were present because there was a low level of recruitment none of which survived to mature plants. The number of mature plants declined from 0.023 to 0.004/m2 indicating that under the present grazing system the complete elimination of A. lappacea from pastures in north-western NSW is possible if some form of managed recruitment is not devised.

scholarly journals Long term monitoring of recruitment dynamics determines eradication feasibility for an introduced coastal weed

NeoBiota ◽  
2019 ◽  
Vol 50 ◽  
pp. 31-53
Author(s):  
John K. Scott ◽  
Kathryn L. Batchelor ◽  
Bruce L. Webber
Keyword(s):  
Western Australia ◽  
Seed Bank ◽  
Soil Seed Bank ◽  
Survey Methods ◽  
Control Program ◽  
Management Program ◽  
Detection Methods ◽  
Soil Core ◽  
National Significance ◽  
Bitou Bush

Bitou bush (Chrysanthemoides monilifera subsp. rotundata) is a Weed of National Significance in Australia and has impacted a significant portion of the eastern coastline. Its discovery in Western Australia was, therefore, a cause for concern. Assessment and control of the isolated and well-defined population began in 2012. To assess the feasibility of eradication in Western Australia as a management outcome for bitou bush, we applied a rigorous data-driven quantification and prediction process to the control program. Between 2012 and 2018 we surveyed over 253 ha of land and removed 1766 bitou bush plants. Approximately 97 person-days were spent over the six years of survey. We measured the seed bank viability for five years starting in 2013, with the 2017 survey results indicating a decline of mean viable seeds/m2 from 39.3 ± 11.4 to 5.7 ± 2.2. In 2018 we found only ten plants and no newly recruited seedlings in the population. No spread to other areas has been recorded. Soil core studies indicate that the soil seed bank is unlikely to persist beyond eight years. Eradication of the population in Western Australia, defined as five years without plants being detected, therefore remains a realistic management goal. The information generated from the documentation of this eradication program provides invaluable insight for weed eradication attempts more generally: novel detection methods can be effective in making surveys more efficient, all survey methods are not entirely accurate and large plants can escape detection, bitou bush seeds persist in the soil but become effectively undetectable at low densities, and migration of seed was unquantifiable, possibly compromising delimitation. Continued monitoring of the Western Australian population will determine how much of a risk these factors represent to eradication as the outcome of this management program.

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