Conservation biology of banksias: insights from natural history to simulation modelling

2007 ◽  
Vol 55 (3) ◽  
pp. 280 ◽  
Author(s):  
Byron B. Lamont ◽  
Neal J. Enright ◽  
E. T. F. Witkowski ◽  
J. Groeneveld
Keyword(s):  
Seed Production ◽  
Western Australia ◽  
Seed Set ◽  
Conservation Management ◽  
Fire Regime ◽  
Simulation Modelling ◽  
Detailed Knowledge ◽  
Long Distance ◽  
Viable Seeds ◽  
Growing Conditions

We have studied the ecology and conservation requirements of Banksia species in the species-rich sandplains of south-western Australia for 25 years. Loss of habitat through land-clearing has had the greatest impact on their conservation status over the last 50 years. Ascertaining optimal conditions for conservation management in bushland requires detailed knowledge of the species under consideration, including demographic attributes, fire regime, growing conditions and interactions with other species. Where populations have been fragmented, seed production per plant has also fallen. The group most vulnerable to the vagaries of fire, disease, pests, weeds and climate change are the non-sprouters, rather than the resprouters, with population extinction so far confined to non-sprouting species. Recent short-interval fires (<8 years) appear to have had little impact at the landscape scale, possibly because they are rare and patchy. Fire intervals exceeding 25–50 years can also lead to local extinction. Up to 200 viable seeds are required for parent replacement in Banksia hookeriana when growing conditions are poor (low post-fire rainfall, commercial flower harvesting) and seed banks of this size can take up to 12 years to be reached. Seed production is rarely limited by pollinators, but interannual seasonal effects and resource availability are important. Genetic diversity of the seed store is quickly restored to the level of the parents in B. hookeriana. Florivores and granivores generally reduce seed stores, although this varies markedly among species. In Banksia tricuspis, black cockatoos actually increase seed set by selectively destroying borers. Potential loss of populations through the root pathogen Phytophthora cinnamomi also challenges management, especially in the southern sandplains. Prefire dead plants are a poor source of seeds for the next generation when fire does occur. Harvesting seeds and sowing post-fire have much to commend them for critically endangered species. Bare areas caused by humans can result in ideal conditions for plant growth and seed set. However, in the case of B. hookeriana/B. prionotes, disturbance by humans has fostered hybridisation, threatening the genetic integrity of both species, whereas fine-textured soils are unsuitable for colonisation or rehabilitation. Few viable seeds become seedlings after fire, owing to post-release granivory and herbivory and unsuitable germination conditions. Seedling-competitive effects ensure that season/intensity of fire is not critical to recruitment levels, except in the presence of weeds. Water availability during summer–autumn is critical and poses a problem for conservation management if the trend for declining rainfall in the region continues. Our simulation modelling for three banksias shows that the probability of co-occurrence is maximal when fire is stochastic around a mean of 13 years, and where fire-proneness and post-fire recruitment success vary in the landscape. Modelling results suggest that non-sprouting banksias could not survive the pre-European frequent-fire scenario suggested by the new grasstree technique for south-western Australia. However, we have yet to fully explore the conservation significance of long-distance dispersal of seeds, recently shown to exceed 2.5 km in B. hookeriana.

scholarly journals Maximising seed production potential in white clover: factors influencing seed set per floret

1996 ◽  
Vol 6 ◽  
pp. 41-44
Author(s):  
R.G. Thomas
Keyword(s):  
Seed Production ◽  
White Clover ◽  
Management Practices ◽  
Seed Set ◽  
Head Development ◽  
Light Intensities ◽  
Ovule Sterility ◽  
Growing Conditions ◽  
High Level ◽  
Seed Yields

The causes of low seed set per floret in white clover (Trifolium repens L.) are reviewed. Three stages of flower head development are distinguished as important for a high level of seed set: a pre-fertilisation stage, a stage of anthesis leading to pollination, and a postfertilisation stage in which seed provisioning occurs. In sunny conditions the percentage seed set is limited at the pre-fertilisation stage by up to 20-30% ovule sterility. Relatively low light intensities during the postfertilisation stage can lead to abortion of a high proportion of fertilised ovules and developing seeds. Experimental results suggest that seed yields under optimal growing conditions can be limited solely by the level of pre-fertilisation ovule sterility and probably cannot be bettered, but further understanding of the seed-provisioning requirements for photosynthate could lead to improved management practices for seed production under conditions of lower light intensities. Keywords: abortion, light intensity, ovule, seed provisioning, sterility, white clover

Seed production by skeleton weed (Chondrilla juncea L.) in Western Australia in relation to summer drought

1987 ◽  
Vol 38 (4) ◽  
pp. 689 ◽  
Author(s):  
J Dodd ◽  
FD Panetta
Keyword(s):  
Soil Water ◽  
Seed Production ◽  
Western Australia ◽  
Summer Rainfall ◽  
Soil Water Storage ◽  
First Year ◽  
Root Penetration ◽  
Summer Drought ◽  
Air Temperatures ◽  
Viable Seeds

Seed production in Forms A and C of C. juncea was measured at 11 wheatbelt sites in Western Australia and under glasshouse conditions. Most field-grown plants produced abundant viable seeds, even without substantial summer rainfall. Up to 27.6 x l03 seeds per plant were recorded, and their viability was frequently between 80 and 90%. Even in their first year, some plants produced more than 10000 seeds each. Through the summer, seed production often followed either a positively skewed, or a bimodal curve. Falls of rain in summer did not increase seed output or affect its quality in established plants. Exceptionally high air temperatures appeared to depress seed numbers and/or viability at several, but not all, sites. At the end of summer, when young plants were 9-12 months old, soil water extraction had occurred to 310 cm, indicating root penetration to this depth. Conservative water use by C. juncea during summer was indicated by low values of soil water depletion. In glasshouse-grown plants, simulated drought reduced seed numbers, viability, primary dormancy and seed weight, although the two forms responded differently. Given adequate winter rainfall to recharge soil water storage, C. juncea appears capable of producing large quantities of viable seeds throughout the Western Australian wheatbelt.

Knotweed (Fallopia spp.) Invasion of North America Utilizes Hybridization, Epigenetics, Seed Dispersal (Unexpectedly), and an Arsenal of Physiological Tactics

2016 ◽  
Vol 9 (1) ◽  
pp. 71-80 ◽  
Author(s):  
Sharon Gillies ◽  
David R. Clements ◽  
Jennifer Grenz
Keyword(s):  
North America ◽  
Seed Production ◽  
Japanese Knotweed ◽  
Male Sterile ◽  
Long Distance ◽  
Large Numbers ◽  
Ability To Regenerate ◽  
Bohemian Knotweed ◽  
Viable Seeds ◽  
Giant Knotweed

AbstractMore than 100 years ago, Japanese knotweed was introduced to North America. Given its vigorous rhizome system and capability to grow from rhizome and stem fragments, it persists and spreads locally, forming monotypic stands. The Japanese knotweed clone originally introduced was a male sterile female clone; thus, early in the invasion, reproduction from seed was not an issue. The implication was that long-distance dispersal was relatively rare. However, recently, widespread hybridization between Japanese knotweed and Sakhalin (giant) knotweed has been reported, with the hybrid species, Bohemian knotweed, forming the majority of knotweed plants in many areas and possessing higher variability than the parent species. The hybrids produce large numbers of wind-dispersed viable seeds that germinate at rates approaching 100% in some populations. As temperatures increase, knotweed is predicted to expand its range farther north and to higher elevations. With the ability to regenerate from vegetative fragments and disperse via seeds, invasive knotweed species are on the move. An arsenal of chemical weapons, the ability to shade out competitors, and the ability to adapt rapidly through epigenetic change makes knotweed a formidable invader. We observed that knotweed species clearly possess 8 of the 12 ideal weed characteristics, with Bohemian knotweed likely exhibiting still more because of prolific seed production. More research is needed to answer pressing questions. How does hybridization affect knotweed epigenetics? Under what conditions might seed production become more frequent? What kind of niche expansion is possible with the increased variability? Given the considerable challenges posed by knotweed species that promise to become even greater with the proliferation and spread of Bohemian ecotypes, only a thoroughly researched, well-informed approach to knotweed management across North America can be successful.

scholarly journals Prescribed burning in a mediterranean-climate region mitigates the disturbance by bushfire to a critical food resource for an endangered bird, the Carnaby’s cockatoo

Fire Ecology ◽  
2019 ◽  
Vol 15 (1) ◽  
Author(s):  
Valerie S. Densmore ◽  
Emma S. Clingan
Keyword(s):  
Seed Production ◽  
Prescribed Burning ◽  
Fire Regime ◽  
Fire Hazard ◽  
Food Resource ◽  
Management Tool ◽  
Fire Intensity ◽  
Prescribed Burns ◽  
Low Intensity ◽  
Percentage Survival

Abstract Background Prescribed burning is used to reduce fire hazard in highly flammable vegetation types, including Banksia L.f. woodland that occurs on the Swan Coastal Plain (SCP), Western Australia, Australia. The 2016 census recorded well over 1.9 million people living on the SCP, which also encompasses Perth, the fourth largest city in Australia. Banksia woodland is prone to frequent ignitions that can cause extensive bushfires that consume canopy-stored banksia seeds, a critical food resource for an endangered bird, the Carnaby’s cockatoo (Calyptorynchus latirostris, Carnaby 1948). The time needed for banksias to reach maturity and maximum seed production is several years longer than the typical interval between prescribed burns. We compared prescribed burns to bushfires and unburned sites at three locations in banksia woodland to determine whether low-intensity prescribed burns affect the number of adult banksias and their seed production. Study sites were matched to the same vegetation complex, fire regime, and time-since-fire to isolate fire intensity as a variable. Results Headfire rates of spread and differenced normalized burn ratios indicated that prescribed burning was generally of a much lower intensity than bushfire. The percentage survival of adult banksias and their production of cones and follicles (seeds) did not decrease during the first three years following a prescribed burn. However, survival and seed production were significantly diminished followed high-intensity bushfire. Thus, carrying capacity for Carnaby’s cockatoo was unchanged by prescribed burning but decreased markedly following bushfire in banksia woodland. Conclusions These results suggest that prescribed burning is markedly different from bushfire when considering appropriate fire intervals to conserve canopy habitats in fire-resilient vegetation communities. Therefore, low-intensity prescribed burning represents a viable management tool to reduce the frequency and extent of bushfire impacts on banksia woodland and Carnaby’s cockatoo.

The influence of floral morph ratios and low plant density on mating and fertility in a tristylous colonizing species

Botany ◽  
2018 ◽  
Vol 96 (8) ◽  
pp. 533-545 ◽  
Author(s):  
Christopher M. Balogh ◽  
Spencer C.H. Barrett
Keyword(s):  
Field Experiment ◽  
Seed Set ◽  
Plant Density ◽  
Pollen Limitation ◽  
Lythrum Salicaria ◽  
Long Distance ◽  
Experimental Conditions ◽  
Wide Range ◽  
Morph Ratios ◽  
Floral Morph

Sexual reproduction in heterostylous populations may be vulnerable to demographic conditions because of the small number of mating types in populations. Here, we investigate mating and fertility under natural and experimental conditions in tristylous Lythrum salicaria L., an invasive species that exhibits a wide range of floral morph ratios and demographic contexts. We grew 147 open-pollinated seed families from six populations with different morph structures to estimate intermorph mating (d). In a field experiment, we used progeny ratios from 47 spatially isolated individuals to estimate d, and measured the intensity of pollen limitation experienced by the morphs. The M- and S-morphs experienced high rates of d, regardless of population size or morph ratio. Estimates for the L-morph revealed low levels of intramorph mating in three dimorphic and two trimorphic populations, but near complete intramorph mating in a monomorphic population. Despite high levels of intermorph mating in the field experiment, the morphs experienced significant pollen limitation of fruit and seed set, but this did not differ in intensity among the morphs. Our field experiment demonstrates that although plant isolation was associated with pollen limitation of seed set, “long-distance” bee-mediated pollen flow served to maintain intermorph mating. Tristyly in L. salicaria is remarkably robust to the demographic variation associated with colonization.

scholarly journals Fire regime and ecosystem responses: adaptive forest management in a changing world (Part 2)

2019 ◽  
Vol 28 (7) ◽  
pp. 471
Author(s):  
Daniel Moya ◽  
Giacomo Certini ◽  
Peter Z. Fulé
Keyword(s):  
Fire Ecology ◽  
Fire Regime ◽  
Wildland Fire ◽  
Landscape Management ◽  
Rapid Change ◽  
Simulation Modelling ◽  
Population Pressure ◽  
Management Decision ◽  
Ongoing Research ◽  
The World

Fire is an ecological factor in ecosystems around the world, made increasingly more critical by unprecedented shifts in climate and human population pressure. The knowledge gradually acquired on the subject is needed to improve fire behaviour understanding and to enhance fire management decision-making. This issue (Volume 28, issue 7, International Journal of Wildland Fire) is Part 2 of a special issue aimed at synthesising ongoing research on preventive management and post-fire restoration, including characterisation of the wildland–urban interface (WUI) and assessing the post-fire restoration of wilderness and WUI areas. Landscape management was also investigated using remote sensing techniques and simulation modelling to improve ecosystem resilience. As in Part 1 (Volume 28, issue 5, International Journal of Wildland Fire), the current issue covers diverse forest settings under scenarios of changing climate and land use. The broad geographical range of these studies highlights key similarities of wildfire issues around the world, but detailed data show unique local circumstances that must be considered. The new information from these six papers helps advance fire ecology and management during a period of rapid change.

Management of Chrysanthemoides monilifera subsp. rotundata in Western Australia

2014 ◽  
Vol 7 (1) ◽  
pp. 190-196 ◽  
Author(s):  
John K. Scott ◽  
Kathryn L. Batchelor
Keyword(s):  
Western Australia ◽  
Native Species ◽  
Initial Step ◽  
Buffer Zone ◽  
Industrial Area ◽  
Long Distance ◽  
Awareness Campaign ◽  
First Time ◽  
Established Population ◽  
Bitou Bush

AbstractOne of Australia's most serious weeds, Chrysanthemoides monilifera subsp. rotundata (bitou bush) was recently found for the first time in Western Australia as a well established population in Kwinana, a major port and industrial area south of Perth, the State's capital. This population is remote from other bitou bush infestations in Australia and had escaped detection despite extensive surveys in the same State for the other subspecies that is present in Australia, Chrysanthemoides monilifera subsp. monilifera (boneseed). The main reasons it went undetected are thought to be the tightly controlled access to this area because of mineral processing and port activities, the unusual invasion route via a heavy industrial area and the morphological similarity to a native species when it is not flowering. Two surveys defined the core population of 1038 plants that are spread along the coast over a 25-ha semi-circle with about a 500-m (1640 ft) diameter. Subsequent surveys of first a 500 m buffer zone and later a 1-km (0.621 mi) buffer found four additional plants, indicating that there is considerable potential for dispersal. We concluded that the survey has not delimited the distribution because of the potential and evidence for long distance dispersal. Cooperation by the various land managers has led to all plants being killed, as an initial step to management of this species. Other steps to be undertaken include an awareness campaign in the area that would need to be surveyed for delimitation of the spatial distribution and seed bank assessment to measure potential dispersal both in space and through time. It remains to be determined what is the best strategic response: eradication or containment.

Using simulation to map fire regimes: an evaluation of approaches, strategies, and limitations

2003 ◽  
Vol 12 (4) ◽  
pp. 309 ◽  
Author(s):  
Robert E. Keane ◽  
Geoffrey J. Cary ◽  
Russell Parsons
Keyword(s):  
Geographical Information Systems ◽  
Fire History ◽  
Fire Regime ◽  
Wildland Fire ◽  
Fire Regimes ◽  
Simulation Modelling ◽  
Fire Frequency ◽  
Geographical Information ◽  
Spatially Explicit ◽  
Eastern Australia

Spatial depictions of fire regimes are indispensable to fire management because they portray important characteristics of wildland fire, such as severity, intensity, and pattern, across a landscape that serves as important reference for future treatment activities. However, spatially explicit fire regime maps are difficult and costly to create requiring extensive expertise in fire history sampling, multivariate statistics, remotely sensed image classification, fire behaviour and effects, fuel dynamics, landscape ecology, simulation modelling, and geographical information systems (GIS). This paper first compares three common strategies for predicting fire regimes (classification, empirical, and simulation) using a 51�000�ha landscape in the Selway-Bitterroot Wilderness Area of Montana, USA. Simulation modelling is identified as the best overall strategy with respect to developing temporally deep spatial fire patterns, but it has limitations. To illustrate these problems, we performed three simulation experiments using the LANDSUM spatial model to determine the relative importance of (1) simulation time span; (2) fire frequency parameters; and (3) fire size parameters on the simulation of landscape fire return interval. The model used to simulate fire regimes is also very important, so we compared two spatially explicit landscape fire succession models (LANDSUM and FIRESCAPE) to demonstrate differences between model predictions and limitations of each on a neutral landscape. FIRESCAPE was developed for simulating fire regimes in eucalypt forests of south-eastern Australia. Finally, challenges for future simulation and fire regime research are presented including field data, scale, fire regime variability, map obsolescence, and classification resolution.

scholarly journals Sheep gut passage and survival of Mediterranean shrub seeds

2005 ◽  
Vol 15 (1) ◽  
pp. 21-28 ◽  
Author(s):  
Pablo Manzano ◽  
Juan E. Malo ◽  
Begoña Peco
Keyword(s):  
Potential Role ◽  
Central Spain ◽  
Long Distance ◽  
Retama Sphaerocarpa ◽  
Gut Passage ◽  
Lavandula Stoechas ◽  
Significant Difference ◽  
Ecological Importance ◽  
Viable Seeds

Although viable seeds of Mediterranean dry-fruited shrubs are found in herbivore dung, the ecological importance of this observation is still not well understood. We analysed seed retrieval percentages, defecation time and germinability after sheep gut passage for the five most common shrub species of an area in central Spain (Retama sphaerocarpa, Cytisus scoparius, Halimium umbellatum subsp. viscosum, Cistus ladanifer and Lavandula stoechas subsp. pedunculata). Five ewes were fed seeds, and their dung was collected regularly during the following week. Seeds were hand-sorted from dung subsamples and tested for germinability. The defecated seeds were clustered in time, with a majority retrieved in the 24–40 h period, although over 1% of the seeds were retained in the gut for more than 72 h. Data suggested a possible link between seed size and retrieval, with medium-sized seeds less damaged (16–23%) than larger and smaller seeds (10–12%), although only a small number of species were studied. Germination results showed an increased percentage of germination after gut passage for H. umbellatum (x2 test, P<0.05) and a marginally significant difference for C. scoparius (P<0.1). Soft-seeded L. stoechas did not germinate after gut passage. The results indicate a potential role of herbivore endozoochory for the long-distance dispersal of dry-fruited shrubs and their potential colonization of distant sites.

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