Soil vs. Canopy Seed Storage and Plant Species Coexistence in Species-Rich Australian Shrublands (original) (raw)
Related papers
2016
To determine the effects of fire-related germination cues, time-since-fire and habitats, soil-borne seed bank samples of rocky outcrops and forest habitats of Torrington State Conservation Area were examined under glasshouse conditions. A total of 1766 seedlings were recorded from the 128 sample trays over the trial duration of 9 weeks. After 9 weeks, no more seedlings emerged. The seedlings were identified as belonging to 44 species from 38 genera and 23 plant families; comprising 21 woody species, 17 forb species, 3 graminoid species and 3 grass species. The most prominent plant families were Fabaceae (8 woody species) followed by Myrtaceae (4 woody species), Apiaceae (4 forb species) and Epacridaceae, Poaceae and Asteraceae with 3 species each. Both seedling emergence and species richness was greater for heat and combinatorial effect of heat and smoke induced treatments than for control and smoke treatments. However, only the species richness was significant for treatments. Time-since-fire significantly affected the community composition. There were a total of 1351 seedlings germinated from the sites with long time-since-fire (>10 yrs.) and 415 seedlings were emerged from the sites with short time-since-fire (18 months). Germinants were mostly shown from the long-burnt rocky outcrops. There was a habitats effect with rocky outcrop samples having significantly more germinable seeds (1522 seedlings) than soil samples collected from forest habitats (144 seedlings). Examination of the soil seed bank samples and the ground standing vegetation of the study sites showed that the species composition was similar. However, there was a large difference in species richness, with richness showing higher in the ground standing vegetation than the soil samples. ii DECLARATION I certify that the substance of this thesis has not been submitted for any other degree or award and is not currently being submitted for any other qualification. In addition, I declare that to the best of my knowledge, all assistance and sources of information in the preparation of this thesis have been acknowledged. ………………………… Kinzang Dorji iii Acknowledgements My profound and heartfelt thanks to my academic supervisor Associate Professor Dr. Peter Clarke for his close supervision, proper guidance, advice, invaluable support and encouragement throughout the duration of this research. Thanks for many other fruitful discussions and constant positive reinforcements.
Journal of Vegetation Science, 2007
Is primary dormancy required for seed bank persistence of Leucopogon species? How does the distinction between dormancy and persistence affect our understanding of seed bank dynamics in fire-prone regions? Location: Sclerophyllous plant communities, Sydney region, southeastern Australia. Methods: Seed bank longevity of three morphophysiologically dormant species was ascertained using seed burial trials. Seeds of each species were buried in situ in replicate mesh bags and retrieved annually over three years. Laboratory germination trials and embryo growth measurements over time were used to establish in which order each component of dormancy was overcome, and whether seed banks persisted after the loss of primary dormancy. Results: All species had long-term persistent seed banks, with estimated half-lives between 3.5 and 5.5 years. Physiological dormancy was broken by stratification prior to embryo growth, during the first year of burial. Seeds were able to germinate after retrieval, in light and at warm temperatures. Only low levels of germination occurred in situ over three years of burial, and did not increase over time. During germination trials, embryos remained underdeveloped unless seeds germinated, indicating that seeds were committed to germination once embryo growth was initiated. Conclusions: Long-lived seed banks are an important trait of plants from fire-prone communities, but cues observed to promote germination in situ are not necessarily the ones that break dormancy. A failure to distinguish between these two factors can divert attention away from mechanisms actually controlling dormancy and seed bank dynamics.
Ecological Modelling, 2008
Modelling and empirical studies have shown that input from the regional seed pool is essential to maintain local species diversity. However, most of these studies have concentrated on simplified, if not neutral, model systems, and focus on a limited subset of species or on aggregated measures of diversity only (e.g., species richness or Shannon diversity). Thus they ignore more complex species interactions and important differences between species. To gain a better understanding of how seed immigration affects community structure at the local scale in real communities we conducted computer simulation experiments based on plant functional types (PFTs) for a species-rich, fire-prone Mediterranean-type shrubland in Western Australia. We developed a spatially explicit simulation model to explore the community dynamics of 38 PFTs, defined by seven traits-regeneration mode, seed production, seed size, maximum crown diameter, drought tolerance, dispersal mode and seed bank type-representing 78 woody species. Model parameterisation is based on published and unpublished data on the population dynamics of shrub species collected over 18 years. Simulation experiments are based on two contrasting seed immigration scenarios: (1) the 'equal seed input number' scenario, where the number of immigrant seeds is the same for all PFTs, and (2) the 'equal seed input mass' scenario, where the cumulative mass of migrating seeds is the same for all PFTs. Both scenarios were systematically tested and compared for different overall seed input values. Without immigration the local community drifts towards
Journal of Vegetation Science, 1994
Abstract. Post-fire seed germination, seedling mortality and seed banks were investigated in scrub-heath (kwongan) in SW Australia. Study species included herbaceous and woody, obligate seeders and resprouters in two non-bradysporous but significant plant families (Restionaceae and Epacridaceae). In all species, seedlings were recruited only in the first autumn-spring after fire and occurred in similar densities as the estimated germinable annual seed input. Seedlings were absent from unburnt vegetation. Although most species retained some residual seeds after fire, tests (excised embryo culture) indicated that a negligible number of seeds were germinable. Regardless of fire response or species, there appeared to be a large loss of seeds each year and in most cases, only a small proportion of the annual seed production was used in post-fire recovery of plants. Based on seedling: parent ratios, all species had the capacity to reconstitute parent densities from germinants in the first year after fire, but high seedling mortality and no further recruitment resulted in less seedlings than replacements for four resprouter Restionaceae and three Epacridaceae (all obligate seeders) at the end of the third year after fire.
Fire, environment, and the shrubby understorey of heathy-woodland
2016
Soil seedbanks play a key role in the post-fire recruitment of many plant species. Seedbank diversity can be influenced by spatial variability (e.g. geographic location), environmental variability (e.g. soils) and temporal disturbance heterogeneity (e.g. time since fire, TSF) across the landscape. Unlike for aboveground vegetation, relationships between these factors and soil seedbank diversity remain largely unknown. Partitioning the influence of spatial and environmental variability from that of TSF, and explaining how these factors interact with seedbank diversity, will assist conservation managers in their application of prescribed burning. We germinated soil seedbank samples from sites ranging from 1 to 75 years since fire in a heathy-woodland ecosystem across the Otway Ranges in Victoria, Australia. We also measured spatial and environmental variability across sites to partition the influence of these variables and TSF on propagules available for recruitment. We found weak pos...
Soil seed bank composition and diversity in a managed temperate deciduous forest
Biodiversity and Conservation, 2004
Little is known about the influence of forest management on the interaction between seed bank and aboveground vegetation. We surveyed seed banks and vegetation in 10 forest stands under similar abiotic conditions but submitted either to a coppice-with-standards treatment (n = 5) or to a selective-cutting system (n = 5). We analyzed species composition and diversity, community ecological profile, and distribution of taxa among different life forms, strategy, morphology and functional type categories. A total of 2085 seedlings (8296 seeds m−2) germinated-corresponding to 28 species, among which Juncus effusus was the most abundant. Fifty-seven percent of the species were also recorded in the aboveground vegetation, the dominant species being Rubus fruticosus agg., but only 28% of the aboveground species were present in the seed bank. Our results suggest that (1) vernal geophytes and shade-tolerant perennials, which group most true forest species, are not incorporated in the seed bank, (2) parent plants of most seeds were present either in the stand in an earlier dynamic stage or apart from the stand and long-distance dispersed, (3) as expected, early-successional species are well represented in the seed bank, (4) forestry vehicles seem to be a major means of dispersion for stress-tolerant species normally found in forest lanes and wheel tracks. We conclude that seed banks contain species that have a potentially negative impact on the true forest flora and, thus, forest management should minimize soil disturbance and retain remnants of old-coppice woods to conserve disturbance-sensitive true forest species.
Journal of Applied Ecology, 2002
Australia's savannas typically are burnt every 1-3 years. Although there are concerns about the effect of frequent fire on recruitment of Australian savanna species, there is a lack of information. This research aimed to determine whether seed or microsite availability limits seedling recruitment of the overstorey tree Eucalyptus miniata and the midstorey shrub Acacia oncinocarpa , whether seed or microsite availability is affected by frequent fire, and the consequent effect on seedling recruitment. 2. Quadrats were established in unburnt areas. Experimental manipulations were addition of seed and /or disturbance of the soil surface to increase the number of microsites suitable for germination. In a second experiment, seed was added to quadrats established in three fire regimes after the annual burning event (unburnt, burnt early in the dry season, burnt late in the dry season). 3. In unburnt areas, seedling regeneration was limited by both seed supply and microsite availability. Both burning regimes reduced seedling emergence, possibly because the reduced canopy cover caused unfavourable microclimate, the increased grass and forb ground cover increased competition for resources, and there was increased loss of seed to seed harvesters. 4. The results indicate that sexual regeneration of these common species is disadvantaged by current burning practices because both seed supply and the number of microsites are reduced. Thus, long-term changes in savanna floristic structure seem likely unless fire managers aim to increase the fire-free intervals. The relative abundance of species able to reproduce vegetatively may increase under frequent fire regimes. Such a change may take a long time to detect given the fire-resistant and long-lived nature of overstorey species, and the capacity for vegetative regeneration in many savanna species. The impacts of fire on limiting seedling regeneration will require savanna managers to consider fire-free intervals of several years for effective recruitment of dominant woody species.