scholarly journals Temporal dynamics of seedling emergence among four fire ephemerals: the interplay of after-ripening and embryo growth with smoke

2019 ◽  
Vol 29 (2) ◽  
pp. 104-114
Author(s):  
Siti N. Hidayati ◽  
David J. Merritt ◽  
Shane R. Turner ◽  
Kingsley W. Dixon ◽  
Jeffrey L. Walck
Keyword(s):  
Temporal Dynamics ◽  
Seedling Emergence ◽  
Mediterranean Ecosystems ◽  
Similar Species ◽  
Wet Season ◽  
Physiological Dormancy ◽  
Consistent Manner ◽  
Summer Temperatures ◽  
Smoke Water ◽  
Study Species

AbstractThe flora of Mediterranean ecosystems contains families with species having fully and under-developed embryos in their seeds. After-ripening for physiological dormancy release and smoke influence germination in many species. We investigated how after-ripening and embryo growth interact with smoke to influence the temporal dynamics of seedling emergence among fire ephemerals. Seeds were placed in the field and under standardized (50% relative humidity, 30°C) laboratory conditions to test the effects of summer conditions on physiological dormancy loss. Germination was tested with water or smoke compounds (smoke water, KAR1) at a simulated autumn/winter temperature (18/7°C). The timing and amount of seedling emergence with smoke was observed for seeds exposed to near-natural conditions. During summer, physiological dormancy was broken in all species, enabling germination at autumn/winter but not summer temperatures; no embryo growth occurred in seeds with under-developed embryos. At the start of the wet season, seedling emergence from seeds with fully developed embryos occurred earlier than from seeds with under-developed embryos. In a non-consistent manner among our study species, smoke and smoke compounds influenced the rate of embryo growth and amount of germination. Effects of smoke were noticeable in terms of number of emergents in the first emergence season. Among ecologically similar species, we have shown (1) that both thermal and embryo traits exclude germination in the summer, (2) how embryo size influences the timing of seedling emergence in autumn–winter, and (3) a reduced requirement for smoke in the second emergence season after a fire with a shift to reliance on seasonal cues for emergence.

scholarly journals Rainfall as a significant contributing factor to butterfly seasonality along a climatic gradient in the neotropics

2019 ◽  
Author(s):  
María F. Checa ◽  
Elisa Levy ◽  
Jaqueline Rodriguez ◽  
Keith Willmott
Keyword(s):  
Temporal Dynamics ◽  
Dry Forest ◽  
Butterfly Species ◽  
Climatic Gradient ◽  
Wet Season ◽  
Precipitation Regimes ◽  
Butterfly Communities ◽  
Set Up ◽  
Study Sites ◽  
Seasonal Forests

AbstractWe analyzed the dynamics of multi-species butterfly communities along a climatic gradient with varying precipitation regimes for three consecutive years, and determine how climatic variables associate with observed butterfly seasonality. To provide a baseline for future studies of how climate change might affect these butterfly populations, we additionally explored the role of butterfly seasonality as a potential contributing factor for their susceptibility to climate variation. As far as we know, this represents the first study that simultaneously sampled and described seasonality patterns of tropical butterfly communities across ecosystems with varying climatic seasonality. A 3-year survey was carried out at three sites (i.e., wet, transition and dry forests) across a climatic gradient in western Ecuador. Butterflies were sampled using traps baited with rotting banana and prawn every two months from Nov 2010 to Sep 2013. Traps were set up at two heights, in the understory and canopy. In total, 7046 individuals of 212 species were sampled over 180 sampling days.Butterfly communities exhibited conspicuous intra and inter-annual variation in temporal dynamics with certain elements (e.g., maximum abundance recorded) of seasonality patterns likely synchronized in seasonal forests (i.e., transition and dry forest) across years but not in aseasonal forests (i.e., wet forest). In addition, the highest numbers of species and individuals occurred during the wet season across all study sites and years; indeed, rainfall was significantly positively associated with temporal abundance. Likewise, butterfly species displaying stronger seasonality were significantly associated with higher rainfall periods in seasonal forests. Variation in precipitation regimes might significantly affect more seasonal species.

Morphological and physiological dormancy in seeds of Aegopodium podagraria (Apiaceae) broken successively during cold stratification

2009 ◽  
Vol 19 (2) ◽  
pp. 115-123 ◽  
Author(s):  
Filip Vandelook ◽  
Nele Bolle ◽  
Jozef A. Van Assche
Keyword(s):  
Low Temperature ◽  
Seedling Emergence ◽  
Early Spring ◽  
Temperate Climate ◽  
Cold Stratification ◽  
Dormancy Breaking ◽  
Morphophysiological Dormancy ◽  
Temperature Requirement ◽  
Physiological Dormancy ◽  
Chilling Period

AbstractA low-temperature requirement for dormancy break has been observed frequently in temperate-climate Apiaceae species, resulting in spring emergence of seedlings. A series of experiments was performed to identify dormancy-breaking requirements of Aegopodium podagraria, a nitrophilous perennial growing mainly in mildly shaded places. In natural conditions, the embryos in seeds of A. podagraria grow in early winter. Seedlings were first observed in early spring and seedling emergence peaked in March and April. Experiments using temperature-controlled incubators revealed that embryos in seeds of A. podagraria grow only at low temperatures (5°C), irrespective of a pretreatment at higher temperatures. Seeds did not germinate immediately after embryo growth was completed, instead an additional cold stratification period was required to break dormancy completely. Once dormancy was broken, seeds germinated at a range of temperatures. Addition of gibberellic acid (GA3) had a positive effect on embryo growth in seeds incubated at 10°C and at 23°C, but it did not promote germination. Since seeds of A. podagraria have a low-temperature requirement for embryo growth and require an additional chilling period after completion of embryo growth, they exhibit characteristics of deep complex morphophysiological dormancy.

Seed Dormancy and Adaptive Seedling Emergence Timing in Giant Ragweed (Ambrosia trifida)

Weed Science ◽  
2012 ◽  
Vol 60 (1) ◽  
pp. 19-26 ◽  
Author(s):  
Brian J. Schutte ◽  
Emilie E. Regnier ◽  
S. Kent Harrison
Keyword(s):  
Seedling Emergence ◽  
Early Spring ◽  
Soil Conditions ◽  
Inhibitory Influence ◽  
Burial Site ◽  
Crop Fields ◽  
Giant Ragweed ◽  
Physiological Dormancy ◽  
Embryo Dormancy ◽  
Time Required

Giant ragweed germination is delayed by both a physiological dormancy of the embryo (embryo dormancy) and an inhibitory influence of embryo-covering structures (covering structure-enforced [CSE] dormancy). To clarify the roles of embryo and CSE dormancy in giant ragweed seedling emergence timing, we conducted two experiments to address the following objectives: (1) determine changes in germinability for giant ragweed dispersal units (hereafter “involucres”) and their components under natural burial conditions, and (2) compare embryo and CSE dormancy alleviation and emergence periodicity between successional and agricultural populations. In Experiment 1, involucres were buried in crop fields at Columbus, OH, periodically excavated, and brought to the laboratory for dissection. Involucres, achenes, and embryos were then subjected to germination assays at 20 C. In Experiment 2, temporal patterns of seedling emergence were determined at a common burial site. Reductions in embryo and CSE dormancy were compared with controlled-environment stratification followed by germination assays at 12 and 20 C, temperatures representative of soil conditions in spring and summer. Results indicated that overwinter dormancy loss involved sequential reductions in embryo and CSE dormancy. CSE dormancy, which may limit potential for fatal germination during fall, was caused by the pericarp and/or embryo-covering structures within the pericarp. In Experiment 2, successional populations emerged synchronously in early spring, whereas agricultural populations emerged throughout the growing season. Levels of embryo dormancy were greater in the agricultural populations than the successional populations, but CSE dormancy levels were similar among populations. In 12 C germination assays, embryo dormancy levels were positively correlated with time required to reach 95% cumulative emergence (run 1:r= 0.81, P = 0.03; run 2:r= 0.76, P = 0.05). These results suggest that late-season emergence in giant ragweed involves high levels of embryo dormancy that prevent germination at low temperatures in spring.

Seasonal Variation in Bee-Plant Interactions in an Inselberg in the Atlantic Forest in Southeastern Brazil

Sociobiology ◽  
2018 ◽  
Vol 65 (4) ◽  
pp. 612 ◽  
Author(s):  
Marcelita França Marques ◽  
Mariana Scaramussa Deprá ◽  
Maria Cristina Gaglianone
Keyword(s):  
Plant Species ◽  
Atlantic Forest ◽  
Temporal Dynamics ◽  
Interaction Network ◽  
Dry Season ◽  
Floral Resources ◽  
Southeastern Brazil ◽  
Plant Interactions ◽  
Wet Season ◽  
Bee Plant

Studies on bee-plant interactions are relevant to the understanding of temporal patterns in neotropical communities. In isolated habitats such as inselbergs little is yet known about the temporal dynamics in the availability of fl oral resources and interacting bee. In the present study, the objective is to verify the eff ect of seasonality on the bee-plant interaction in an Atlantic Forest inselberg in southeastern Brazil. The bees were sampled monthly in the dry (April/2008-September/2008) and wet seasons (October/2008-March/2009) using an entomological net. A total of 322 bees of 33 species were captured on fl owers of 34 species of plants during the year. Bees richness was similar between seasons (22 species in the wet season and 21 in the dry season), but abundance was higher in the wet season (60% of individuals) and higher diversity occurred in the dry season. Augochloropsis sp1 were the most abundant species and visited the largest number of plant species at each season. In the interaction network, plants with the highest degree were distinct between the seasons. The number of possible interactions was higher in the dry season compared to the wet season and connectance was similar; nestedness however varied between the seasons. The composition of plant and bees species was distinct between the seasons, as well as the interactions between them, mainly due to the alteration in the composition of the plant species and the change in the choice of the bees for the floral resources between the seasons.

scholarly journals Seed germination of Solanum spp. (Solanaceae) for use in rehabilitation and commercial industries

2008 ◽  
Vol 56 (4) ◽  
pp. 333 ◽  
Author(s):  
L. E. Commander ◽  
D. J. Merritt ◽  
D. P. Rokich ◽  
G. R. Flematti ◽  
K. W. Dixon
Keyword(s):  
Seed Germination ◽  
Food Industry ◽  
Incubation Temperature ◽  
Solanum Species ◽  
Seed Embryo ◽  
Physiological Dormancy ◽  
Incubation Temperatures ◽  
Smoke Water ◽  
Solanum Spp ◽  
Seeds Germination

Effective methods for propagation of native Solanum species are required for mine rehabilitation and the native food industry in Australia. This study investigated seed germination of eight native Solanum species with respect to incubation temperature and the efficacy of germination-promoting compounds gibberellic acid (GA3), the butenolide isolated from smoke (karrikinolide, KAR1) and smoke water (SW). Seeds of all species were tested under a temperature regime of 26/13°C or 33/18°C. In these conditions, seeds of only two species, S. cunninghamii Benth. and S. phlomoides Benth. germinated to high levels without treatment. Of the remaining six species, GA3 alone promoted germination in S. chippendalei Symon, S. diversiflorum F.Muell. and S. sturtianum F.Muell., whereas GA3, KAR1 and SW were effective at promoting germination of S. centrale J.M.Black, S. dioicum W.Fitzg. and S. orbiculatum Dunal ex Poir. to varying degrees. Additional incubation temperatures (10, 15, 20, 25 and 30°C) were examined for S. centrale and S. orbiculatum. For both species, broadly similar patterns were noted in the response of seeds to GA3, KAR1 and SW across all temperatures. However, for S. centrale seeds, germination percentages were higher at 26/13°C than at any of the constant temperatures, and there was a trend of increasing germination with increasing constant temperature for S. orbiculatum seeds. Analysis of seed embryo type and imbibition characteristics and consideration of the subsequent germination results indicates that dormant Solanum seeds possess physiological dormancy.

Fire and torrential rainfall: effects on seedling establishment in Mediterranean gorse shrublands

2005 ◽  
Vol 14 (4) ◽  
pp. 413 ◽  
Author(s):  
Martín de Luís ◽  
José Raventós ◽  
Josí C. González-Hidalgo
Keyword(s):  
Seedling Survival ◽  
Seedling Emergence ◽  
Extreme Rainfall ◽  
Mediterranean Ecosystems ◽  
Western Mediterranean ◽  
Rainfall Simulation ◽  
Vegetation Recovery ◽  
Precipitation Event ◽  
Extreme Rainfall Events ◽  
Torrential Rainfall

Soil degradation and desertification are key problems facing Mediterranean ecosystems and these have worsened recently with the increasing frequency of fires. Moreover, rainfall in western Mediterranean areas is characterized by high intensity, and extreme rainfall events after fire strongly affect the equilibrium between soil erosion and vegetation recovery. These facts led us to carry out experimental fires in a fire-prone vegetation community (dominated by Mediterranean gorse, Ulex parviflorus Pourr.) to study the effect of a torrential rainfall event (through rainfall simulation) on the short-term vegetation regeneration process (seedling emergence and survival). The results indicate that, in Mediterranean gorse shrublands after fire, an extreme precipitation event does not affect seedling emergence (either through seed loss or from seed germination). In contrast, it has a significant effect on the reduction of seedling survival both from direct impact (seedlings buried by sediment or seedlings totally or partially unearthed) and indirectly as a result of soil and litter losses. As a consequence, the combination of fire and torrential rainfall has an important and persistent effect on vegetation recovery, and may cause further degradation, which eventually becomes irreversible.

scholarly journals Propagation of Pawpaw—A Review

2003 ◽  
Vol 13 (3) ◽  
pp. 428-433 ◽  
Author(s):  
Robert L. Geneve ◽  
Sharon T. Kester ◽  
Kirk W. Pomper ◽  
Jonathan N. Egilla ◽  
Cynthia L.H. Finneseth ◽  
...  
Keyword(s):  
Seedling Emergence ◽  
Shoot Proliferation ◽  
Chilling Temperature ◽  
Secondary Products ◽  
Small Tree ◽  
Asimina Triloba ◽  
Morphophysiological Dormancy ◽  
Seedling Explants ◽  
Physiological Dormancy ◽  
Medicinal Properties

Pawpaw (Asimina triloba) is an under-exploited small tree with commercial potential as a fruit crop, ornamental tree, and source of secondary products with insecticidal and medicinal properties. It is most often propagated from seeds that are recalcitrant and must be stored moist at a chilling temperature. Seeds display combinational (morphophysiological) dormancy. Endogenous, physiological dormancy is broken by about 100 days of chilling stratification followed by a period of warm moist conditions where the small embryo develops prior to seedling emergence about 45 days after the warm period begins. Pawpaw cultivars with superior fruit characteristics are propagated by grafting onto seedling understocks. The most common practice is chip budding. Other methods of clonal propagation have proven problematic. Pawpaw can be propagated from cuttings, but only in very young seedling stock plants. Micropropagation from mature sources is not yet possible, but shoot proliferation has been accomplished from seedling explants and explants rejuvenated by induction of shoots from root cuttings of mature plants. However, rooting of microcuttings and subsequent acclimatization has not been successful.

scholarly journals Spatial and temporal dynamics of CO<sub>2</sub> partial pressure in the Yellow River, China

2014 ◽  
Vol 11 (10) ◽  
pp. 14063-14096
Author(s):  
L. Ran ◽  
X. X. Lu ◽  
J. E. Richey ◽  
H. Sun ◽  
J. Han ◽  
...  
Keyword(s):  
Partial Pressure ◽  
Temporal Dynamics ◽  
Yellow River ◽  
Dilution Effect ◽  
High Pco2 ◽  
The Yellow River ◽  
Wet Season ◽  
Co2 Partial Pressure ◽  
River Waters ◽  
Air Interface

Abstract. Carbon transport in river systems is an important component of the global carbon cycle. Most rivers of the world act as atmospheric CO2 sources due to high riverine CO2 partial pressure (pCO2). We investigated the pCO2 dynamics in the Yellow River watershed by using historical water chemistry records (1950s–1984) and recent sampling along the mainstem (2011–2012). Except the headwater region where the pCO2 was lower than the atmospheric equilibrium (i.e., 380 μatm), river waters in the remaining watershed were supersaturated with CO2. The average pCO2 for the watershed was estimated at 2810 ± 1985 μatm, which is 7-fold the atmospheric equilibrium. This indicates a strong CO2 outgassing across the water-air interface. As a result of severe soil erosion and dry climate, waters from the Loess Plateau in the middle reaches had higher pCO2 than that from the upper and lower reaches. From a seasonal perspective, the pCO2 varied from about 200 μatm to >30 000 μatm with higher pCO2 usually occurring in the dry season and low pCO2 in the wet season (at 73% of the sampling sites), suggesting the dilution effect of water. While the pCO2 responded positively to total suspended solids (TSS) transport when the TSS was less than 100 kg m−3, it slightly decreased and remained stable when the TSS exceeded 100 kg m−3. This stable pCO2 is largely due to gully erosion that mobilizes subsoils characterized by low organic matter for decomposition. In addition, human activities have changed the pCO2 dynamics. Particularly, flow regulation by dams can diversely affect the temporal changes of pCO2, depending on the physiochemical properties of the regulated waters and adopted operation scheme. Given the high pCO2 in the Yellow River waters, the resultant CO2 outgassing is expected to be substantial and warrants further investigation.

scholarly journals The contribution of trees and grasses to productivity of an Australian tropical savanna

2016 ◽  
Vol 13 (8) ◽  
pp. 2387-2403 ◽  
Author(s):  
Caitlin E. Moore ◽  
Jason Beringer ◽  
Bradley Evans ◽  
Lindsay B. Hutley ◽  
Ian McHugh ◽  
...  
Keyword(s):  
Land Surface ◽  
Carbon Flux ◽  
Temporal Dynamics ◽  
Carbon Sink ◽  
Tropical Savanna ◽  
Wet Season ◽  
Carbon Dioxide Fluxes ◽  
Dynamic Partitioning ◽  
Eddy Covariance Measurements ◽  
Competition For Resources

Abstract. Savanna ecosystems cover 20 % of the global land surface and account for 25 % of global terrestrial carbon uptake. They support one fifth of the world's human population and are one of the most important ecosystems on our planet. Savanna productivity is a product of the interplay between trees and grass that co-dominate savanna landscapes and are maintained through interactions with climate and disturbance (fire, land use change, herbivory). In this study, we evaluate the temporally dynamic partitioning of overstory and understory carbon dioxide fluxes in Australian tropical savanna using overstory and understory eddy covariance measurements. Over a 2-year period (September 2012 to October 2014) the overall net ecosystem productivity (NEP) of the savanna was 506.2 (±22 SE) g C m−2 yr−1. The total gross primary productivity (GPP) was 2267.1 (±80 SE) g C m−2 yr−1, of which the understory contributed 32 %. The understory contribution was strongly seasonal, with most GPP occurring in the wet season (40 % of total ecosystem in the wet season and 18 % in the dry). This study is the first to elucidate the temporal dynamics of savanna understory and overstory carbon flux components explicitly using observational information. Understanding grass productivity is crucial for evaluating fuel loads, as is tree productivity for quantifying the tree carbon sink. This information will contribute to a significant refinement of the representation of savannas in models, as well as improved understanding of relative tree-grass productivity and competition for resources.

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