Category Archives: climate change

The Role of Swamps in Drought: Popes Glen Creek, Blackheath

Alan Lane

Introduction

The important role of swamps in water storage and as regulators of stream flow has been well documented (10.1016/j.geomorph.2018.03.004). Previous EMR project summary reports on Popes Glen Creek, Blackheath, have described the establishment of a swamp on the former highly degraded and weed-infested silt plug at the headwaters of the creek.  (See links at end of this summary.)  That 18-year long project has been documented in “The Full Story”, https://dl.bookfunnel.com/ebgais2pxn and an 8-minute summary video can be viewed at https://www.youtube.com/watch?v=610sas330EQ

The recent severe drought in New South Wales provided the opportunity to monitor the water table in this swamp in the absence of rain and compare the impact on the swamp vegetation with that on more elevated and drier slopes nearby.

How we measured the water table. Six piezometers were installed at the start of this rehabilitation project, located about 50 m apart and midway between the edges of the long, rectangular silt plug. These went down to the bedrock, at depths of between 113 and 152 cm and were used to monitor water table depth and also for sampling water quality and stygofauna.

What we found. During periods of normal or above average rainfall (e.g. September 2019), the water table at each of these bore holes was typically at the depth below soil surface shown in Table 1.

Levels fell almost to bedrock during the drought (Oct 2019 – Dec 2019), before recovering after rains in January and February 2020 (Tables 1, 2). 

Table 1. Water table depths during normal and below-average rainfall periods.

Bore hole number
Depth below surface (cm) 1 2 3 4 5 6
Normal rainfall period (Sept 2019) 31 2 7 11 23 9
After drought period (Dec 2019) 103 106 121 103 123
After recovering rainfall (Feb 2020) 29 0 12 21 13

Table 2.  Rainfall, October 2019 – February 2020.

Month Rainfall (mm)1 5-year average (mm)2 % of average
September 2019 81.4 53.6 151.6
October 2019 23.8 76.7 31.0
November 2019 26.4 82.2 32.1
December 2019 0.4 69.5 0.6
January 2020 99.2 127.9 77.6
February 2020 560.4 183.6 305
  1. From Bureau of Meteorology, Mount Boyce, NSW
  2. From willyweather.com.au, Mount Boyce, NSW

During this period of extreme drought, the vegetation on the slopes above the Popes Glen swamp manifested extreme water stress in a way never before seen (Figs. 1, 2). Many of these extensive expanses of Coral Fern (Glycaenia dicarpa), stands of Fishbone Water Fern (Blechnum nudum) and individual Black Tree Fern (Cyathea australis) plants have not recovered and now appear unlikely to do so.

Figure 1. Expanses of severely water-stressed Glycaenia dicarpa on slopes above the Popes Glen swamp.

Figure 2. Many of the Blechnum nudum and Cyathea australis on slopes above the swamp have failed to recover.

In marked contrast, the vegetation in the swamp area (Fen Sedge (Carex gaudichaudiana), Tassel Sedge (Carex fascicularis), Tall Spikerush (Eleocharis sphacelata) and Juncus sp.) remained lush and vigorous (Fig. 3), suggesting it was sustained by the supply of water retained in the substrate.

This supply was progressively depleted during the drought and the water table had fallen almost to bedrock before the rains in January (Tables 1, 2).

Figure 3. Vegetation in the Popes Glen swamp remained lush throughout the drought.

Implications. It seems inevitable that this water supply would have been completely exhausted had the 2019-2020 drought lasted longer. Temperate Highland Peat Swamps on Sandstone (THPSS), including the Popes Glen swamp, appear threatened by the even more prolonged droughts anticipated as climate disruptions due to global heating become more marked.

Acknowledgements. This work was supported by Blue Mountains City Council and funding from the Environmental Trust of NSW.

Contact. Alan Lane alanlane388@gmail.com

See also EMR Project Summaries:

 

Ku-ring-gai Flying-fox Reserve Habitat Restoration Project at Gordon, 2000 – 2019 UPDATE of EMR feature

Nancy Pallin

[Update to EMR feature –  Pallin, Nancy (2001) Ku-ring-gai Flying-fox Reserve Habitat restoration project, 15 years on.  Ecological Management & Restoration 1:1, 10-20. https://onlinelibrary.wiley.com/doi/10.1046/j.1442-8903.2000.00003.x]

Key words:         bush regeneration, community engagement, wallaby browsing, heat events, climate change

Figure 1. Habitat restoration areas at Ku-ring-gai Flying-fox Reserve within the urban area of Gordon, showing areas treated during the various phases of the project. Post-2000 works included follow up in all zones, the new acquisition area, the pile burn site, the ecological hot burn site and sites where vines have been targeted. (Map provided by Ku-ring-gai Council.)

Introduction. The aim of this habitat restoration project remains to provide self-perpetuating indigenous roosting habitat for Grey-headed Flying-fox (Pteropus poliocephalus) located at Ku-ring-gai Flying-fox Reserve in Gordon, NSW Australia (Fig 1).  The secondary aim was to retain the diversity of fauna and flora within the Flying-fox Reserve managed by Ku-ring-gai Council. Prior to works, weed vines and the activity of flying-foxes in the trees had damaged the canopy trees while dense weed beneath prevented germination and growth of replacement trees.  Without intervention the forest was unable to recover.  Natural regeneration was assisted by works carried out by Bushcare volunteers and Council’s contract bush regeneration team.  The work involved weed removal, pile burns and planting of additional canopy trees including Sydney Bluegum (Eucalyptus saligna), which was expected to cope better with the increased nutrients brought in by flying-foxes.

Figure 2. The changing extent of the Grey-headed Flying-fox camp from the start of the project, including updates since 2000. (Data provided by KBCS and Ku-ring-gai Council)

Significant changes have occurred for flying-foxes and in the Reserve in the last 20 years.

In 2001 Grey-headed Flying-fox was added to the threatened species lists, of both NSW and Commonwealth legislation, in the Vulnerable category.  Monthly monitoring of the number of flying-foxes occupying the Reserve  has continued monthly since 1994 and, along with mapping of the extent of the camp, is recorded on Ku-ring-gai Council’s Geographical Information System. Quarterly population estimates contribute to the National Monitoring Program to estimate the population of Grey-headed Flying-fox.  In terms of results of the monitoring, the trend in the fly-out counts at Gordon shows a slight decline.  Since the extreme weather event in 2010, more camps have formed in the Sydney basin in response to declining food resources.

In 2007, prompted by Ku-ring-gai Bat Conservation Society (KBCS), the size of the Reserve was increased by 4.3 ha by NSW Government acquisition and transfer to Council of privately owned bushland. The Voluntary Conservation Agreement that had previously established over the whole reserve in 1998 was then extended to cover the new area.   These conservation measures have avoided new development projecting into the valley.

From 2009 Grey-headed Flying-fox again shifted their camp northwards into a narrow gully between houses (Fig 2).  This led to human-wildlife conflict over noise and smell especially during the mating season. Council responded by updating the Reserve Management Plan to increase focus on the needs of adjoining residents.  Council removed and trimmed some trees which were very close to houses. In 2018 the NSW Government, through Local Governments, provided grants for home retrofitting such as double glazing, to help residents live more comfortably near flying-fox camps.

Heat stress has caused flying-fox deaths in the Reserve on five days since 2002. Deaths (358) recorded in 2013, almost all were juveniles of that year.  KBCS installed a weather station (Davis Instruments Vantage Pro Plus, connected through a Davis Vantage Connect 3G system) and data loggers to provide continuous recording of temperature and humidity within the camp and along Stoney Creek.  The station updates every 15 minutes and gives accurate information on conditions actually being experienced in the camp by the flying-foxes. The data is publicly available http://sydneybats.org.au/ku-ring-gai-flying-fox-reserve/weather-in-the-reserve/Following advice on the location and area of flying-fox roosting habitat and refuge areas on days of extremely high temperatures (Fig 3.) by specialist biologist Dr Peggy Eby, Council adopted the Ku-ring-gai Flying-fox Reserve 10 Year Management and Roosting Habitat Plan in 2018.  Restoration efforts are now focused on improving habitat along the lower valley slopes to encourage flying-foxes to move away from residential property and to increase their resilience to heat events which are predicted to increase with climate change.

Figure 3. Map showing the general distribution of flying-foxes during heat events, as well as the location of exclosures. (Map provided by Ku-ring-gai Council)

Further works undertaken.  By 2000 native ground covers and shrubs were replacing the weeds that had been removed by the regeneration teams and Bushcare volunteers.  However, from 2004, browsing by the Swamp Wallaby (Wallabia bicolor) was preventing growth of young trees and shrubs.  Bushcare volunteers, supported by KBCS and Council responded by building tree cages made from plastic-mesh and wooden stakes. Reinforcing-steel rods replaced wooden stakes in 2008.   From 2011, the Bushcare volunteers experimented with building wallaby exclosures, to allow patches of shrubs and groundcovers to recover between trees (Figs 3 and 4).  Nineteen wallaby exclosures have been built. These range in size from 7m2 to 225m2 with a total area of 846m2.   Wire fencing panels (Mallee Mesh Sapling Guard 1200 x 1500mm) replaced plastic mesh in 2018.  Silt fence is used on the lower 0.5m to prevent reptiles being trapped and horizontally to deter Brush Turkey (‎Alectura lathami) from digging under the fence.

The wallaby exclosures have also provided an opportunity to improve moisture retention at ground level to help protect the Grey-headed Flying-fox during heat events.  While weed is controlled in the exclosures south of Stoney Creek, those north of the creek retain Trad and privets, consistent with the 10 Year Management and Roosting Habitat Plan.

Madeira Vine (Anredera cordifolia) remained a threat to canopy trees along Stoney Creek for some years after 2000, despite early treatments.  The contract bush regen team employed sInce 2010 targeted 21 Madiera Vine incursions.

A very hot ecological burn was undertaken in 2017 by Council in order to stimulate germination of soil stored seed and regenerate the Plant Community Type (PCT) – Smooth-barked Apple-Turpentine-Blackbutt tall open forest on enriched sandstone slopes and gullies of the Sydney region (PCT 1841).  This area was subsequently fenced. The contract bush regeneration team was also employed for this work to maintain and monitor the regeneration in the eco-burn area (720 hours per year for both the fire and Madiera Vine combined).

Figure 4. Exclusion fence construction method. Pictured are Bushcare volunteers, Jill Green and Pierre Vignal. (Photo N Pallin).

Figure 5. Natural regeneration in 2018 in (unburnt) exclosure S-6 (including germination of Turpentines). (Photo N. Pallin)

Further results to date. The original canopy trees in Phase 1 and Phase 2 (1987 -1997) areas have recovered and canopy gaps are now mostly closed. Circumference at breast height measurements were taken for seven planted Sydney Blue gum trees.  These ranged from 710 to 1410mm with estimated canopy spread from 2 to 6m.  While original Turpentine (Syncarpia glomulifera) had circumferences from 1070 and 2350mm with canopy spread estimated between 5and 8m, those planted or naturally germinated now have circumference measurements between 420 and 980mm with canopy spread estimated from 1.5 to 3m.  A Red Ash (Alphitonia excelsa) which naturally germinated after initial clearing of weeds now has a circumference of 1250mm with a canopy spread of 5m.  Also three Pigeonberry Ash (Elaeocarpus kirtonii) have circumference from 265 to 405mm with small canopies of 1 to 2m as they are under the canopies of large, old Turpentines.  As predicted by Robin Buchanan in 1985 few Blackbutt (Eucalyptus pilularis) juveniles survived while the original large old trees have recovered and the Sydney Bluegum trees have thrived.

In the Phase 3 (1998 – 2000) area south of Stoney Creek the planted Sydney Blue Gum now have circumferences measuring between 368 and 743 (n7) with canopy spread between 2 and 6 m.  in this area the original large trees have girths between 1125 and 1770mm (n7) whereas trees which either germinated naturally or were planted now range from 130 to 678mm (n12).  These measurement samples show that it takes many decades for trees to reach their full size and be able to support a flying-fox camp.

Wallaby exclosures constructed since 2013 south of Stoney Creek contain both planted and regenerated species.  Eight tree species, 11 midstorey species, 27 understorey species and eight vines have naturally regenerated.  Turpentines grew slowly, reaching 1.5m in 4 years.  Blackbutts thrived initially but have since died. In exclosures north of the creek,  weeds including Large-leaved Privet,  Ligustrum lucidum,  Small-leaved privet,  L. sinense,  Lantana, Lantana camara,  and Trad, Tradescantia fluminensis) have been allow to persist and develop to maximise ground moisture levels for flying-foxes during heat events. Outside the exclosures, as wallabies have grazed and browsed natives, the forest has gradually lost its lower structural layers, a difference very evident in Fig 6.

Figure 6. Visible difference in density and height of ground cover north and south of Stoney creek. (Photo P. Vignal)

Coachwood (Ceratopetalum apetalum) were densely planted in a 3 x 15m exclosure under the canopies of mature Coachwood next to Stoney Creek in 2015. In 4 years they have reached 1.5m.  In this moist site native groundcovers are developing a dense, moist ground cover.

Madiera Vine, the highest-threat weed, is now largely confined to degraded edges of the reserve, where strategic consolidation is being implemented with a view to total eradication.

In the hot burn area, which was both fenced and weeded, recruitment has been outstanding. One 20 x 20m quadrat recorded 58 native species regenerating where previously 16 main weed species and only 6 native species were present above ground. A total of 20 saplings and 43 seedlings of canopy species including Eucalyptus spp., Turpentine and Coachwood were recorded in this quadrat where the treatment involved weed removal, burning and fencing  (S. Brown, Ku-ring-gai Council, July 2019, unpublished data).  Unfortunately, however, the timing and location of the burn did not take into account its impact on the flying-fox camp and there was some damage to existing canopy trees. It will be many years before the canopy trees, which are regenerating, will be strong enough to support flying-foxes.

Monitoring from the weather station and data loggers has shown that close to Stoney Creek on a hot day it is typically 2-3° C cooler, and 5-10% higher in humidity, than in the current camp area (pers. comm. Tim Pearson). During heat events the flying-foxes move to this cooler and moister zone, increasing their chances of survival.

Fauna observed other than flying-foxes includes a pair of Wedge-tail Eagle ( Aquila audax plus their juvenile, a nesting Grey Goshawk (Accipiter novaehollandiae) and a Pacific Baza (Aviceda subcristata).  Powerful Owl (Ninox strenua) individuals continue to use the valley. The presence of raptors and owls indicate that the ecosystem processes appear to be functional. Despite the decline of the shrub layer outside fenced areas, the same range of small bird species (as seen prior to 2000) are still seen including migrants such as Rufous Fantail ( Rhipidura rufifrons) which prefers dense, shady vegetation. The first sighting of a Noisy Pitta (Pitta versicolor) was in 2014.  Long-nosed Bandicoot (Perameles nasuta) individuals appear and disappear, while Swamp Wallaby remains plentiful.

Lessons learned and future directions. Climate change is an increasing threat to Pteropus species. On the advice of Dr Eby, Flying-fox Consultant, Council, KBCS and Bushcare Volunteers agreed to retain all vegetation including weeds such as Large-leaved Privet and Small-leaved Privet, patches of the shrub Ochna (Ochna serrulata) and Trad as a moist ground cover in the camp area and areas used by the flying-foxes during heat events.

Building cheap, lightweight fencing can be effective against wallaby impacts, provided it is regularly inspected and repaired after damage caused by falling branches. This style of fencing has the additional advantage of being removable and reusable.  It has been proposed that, to provide understory vegetation to fuel future burns in parts of the reserve away from the flying-fox camp, further such temporary fencing could be installed.

Ku-ring-gai Council has commenced a  program to install permanent monitoring points to annually record changes in the vegetation, consistent with the state-based  Biodiversity Assessment Method.

Stakeholders and Funding bodies. Members of KBCS make donations, volunteer for monthly flyout counts, Bushcare and present educational events with live flying-foxes. KBCS hosts the website www.sydneybats.org.au. Ku-ring-gai Council which is responsible for the Reserve has been active in improving management to benefit both residents and flying-foxes.  Ku-ring-gai Environmental Levy Grants to KBCS have contributed substantially to purchase of fencing materials and the weather station. http://www.kmc.nsw.gov.au/About_Ku-ring-gai/Land_and_surrounds/Local_wildlife/Native_species_profiles/Grey-headed_flying-fox

Thank you to Jacob Sife and Chelsea Hankin at Ku-ring-gai Council for preparing the maps and to volunteer Pierre Vignal for assistance with tree measurements, downloading data loggers and a photo.  Researcher,  Tim Pearson installed the weather station.

Contact information. Nancy Pallin, Management Committee member, Ku-ring-gai Bat Conservation Society Inc.  PO Box 607, Gordon 2072  Tel 61 418748109. Email:  pallinnancy@gmail.com

The palaeoenvironmental history of Temperate Highland Peat Swamps on Sandstone

Scott Mooney, James Goff and Lennard Martin

Key words (<5 words): sediments, palaeoenvironmental reconstruction, radiocarbon dating

Introduction. Palaeoecology (i.e. study of past environments using fossils and sediment cores) is often used to provide information regarding past environmental conditions. In comparison to modern ecological research, the expanded temporal perspective of palaeoecology unlocks an understanding of pre-anthropogenic variability and how ecosystems have responded to past disturbance and perturbations, thereby allowing consideration of their resilience to various environmental change.

Our Temperate Highland Peat Swamps on Sandstone Research Program (THPSSRP) research has investigated a number of sites in the Blue Mountains and on the Newnes Plateau. Our project aimed to use the sediments accumulating in these sandstone swamps to better understand the dynamics of these ecosystems over time frames that far exceed what is possible through environmental monitoring. We have been documenting the stratigraphy of the sediments using probing and sediment coring/sampling, in association with radiometric (14C, 210Pb) dating, and applying various palaeoenvironmental techniques and proxies to characterize these environments. Our ultimate aims were to characterise recent (historic) trends against the backdrop of a much longer temporal perspective from the palaeoenvironmental analyses and to examine the responses of the swamps over both long (since sediments started accumulating) and short (high-resolution) time frames to disturbance, environmental change and climatic variability.

Sydney Basin Meta-study of Accumulating Sediments. The first component of our research involved a meta-analysis of previous data regarding the ages and organic content of sediments in various depositional environments across the Sydney region. Our aim was to consider rates of sediment accumulation in the post-glacial period (the period since the last glacial maximum, about 21,000 years ago): this information informed our subsequent sampling strategies (e.g. depth of coring, resolution of analyses) and can be used in for future research to better target various chronozones. It is probable that rates of sediment accumulation reflect landscape instability/stability and together with organic content, this provides palaeoenvironmental information relevant to the overall aims of this project. For this component we collated and recalibrated radiocarbon dates (n=132) from 44 sites across the Sydney region, and we identified a subset of 12 sites with quantification of the organic content of the accumulating sediments.

Findings. The synthesis of these data revealed that sedimentation rates underwent a dramatic increase from ~0.2 mm/yr to ~0.6 mm/yr at the beginning of the Holocene (about ~11,700 years ago), which probably reflects post-glacial climatic amelioration. Sedimentation rates remained relatively high during the Holocene, between 0. 4 and 0. 5 mm/yr, although brief decreases are evident, for example centred at 8200, 6500, 2000 and 1200 calibrated radiocarbon years before present (cal. y BP). Only in the last 400 cal y BP do sedimentation rates increase above those present for the majority of the Holocene, peaking at 0.7 mm/yr.

In contrast, organic material began accumulating at around 14,400 cal y BP in these depositional environments, earlier than the 11,700 cal BP increase in sedimentation rates. Before this time all sites exhibited relatively low rates of highly minerogenic sedimentation. After ~14,400 cal y BP the organic content of the sites gradually increased in a trajectory that continued throughout the Holocene, albeit with some major excursions from this trend. As an example, organic content peaked between about 7,500 and 6,000 cal y BP, only to fall to a low at about 5,400 cal y BP, which is then followed by a rapid increase to another peak between about 4,500 and 4,000 cal y BP. This last peak in organic content achieves similar values to the surface/modern samples. This peak (6.7ka)-trough (5.4ka)-peak (4.2ka)-trough (3.2ka) sequence suggests considerable variation in the controls of organic matter production and accumulation, which are mostly climatic parameters. The palaeoenvironmental implications of these results are currently being written for submission to a scientific journal.

Field–based Sampling. Field-based sampling for this research has focused on stable depositional environments in the Sydney region:

  1. Goochs Crater in the Upper Blue Mountains. This site appears to have formed after a rock fall dammed the upper reaches of a relatively narrow valley/canyon. The site is presently a freshwater reed swamp with semi-permanent surface water, although the site has both flooded and burnt since first we first visited. After investigating the stratigraphy and depth of the accumulating sediments, three cores have been collected (G1,G2 & G3) along a transect from the edge to the centre. G1 is a 455 cm long core sampled close to the current waters edge: radiocarbon dating indicates that this represents from the present day back to about 9,500 cal y BP. This core is mostly organic-rich (>60% loss-on-ignition) but these authochthonous sediments are interspersed with abrupt (allochthonous) layers of sand and charcoal, probably transported to this location after major fire events. Our G2 core is 985 cm long and spans the period from about 4,000 to 17,500 cal y BP: it is also highly organic (20-95% loss-on-ignition) but does not include sand/charcoal layers. Core G3 extended down to highly minerogenic sediments at a depth of 795 cm and has a very similar stratigraphy to core G2.
  2. Queens Swamp near Lawson in the Blue Mountains. Queens Swamp was (re-)cored to a depth of 3.8 m and the sediment profile revealed alternating layers of sandy and peaty sediments similar to the edge core (G1) from Goochs Crater. Radiocarbon dating of the Queens Swamp cores suggests a rapidly accumulating upper section of sediments overlying a much older basal layer.
  3. Hanging Rocks Swamp located in Penrose State Forest in the Southern Highlands. A 5.6 m sediment core was also obtained Hanging Rock Swamp and these sediments returned a basal date of 14,500 cal y BP.

Field observations and preliminary results from fieldwork have been published in Quaternary Australasia and Australian Plant Conservation.

Radiocarbon Dating of Sediments. Our THPSS research has involved 35 new radiocarbon (14C) analyses so far across the three sites (Goochs, Queens, Hanging Rock) mentioned above, with a few more planned soon. Twenty of these dates resulted from two AINSE grants, which allowed accelerator mass spectrometry (AMS) 14C dates. This dating was undertaken to develop robust chronologies of the sediments so that palaeoenvironmental changes could be well constrained, but we also undertook some experimentation to consider the optimum sediment fraction for future 14C dating. The sediment fractions considered were charcoal, pollen and short-lived plant macrofossils that were all isolated from the same depth in the sediment profiles. Preliminary results, in preparation for submission at the moment, suggest that charcoal has an inbuilt age of 60-500 years and plant macrofossils return an age closest to the true (modeled) age of that depth.

Preliminary Palaeoenvironmental Interpretation and Conclusions. A variety of palaeoenvironmental techniques have been applied to the sediments sampled from Goochs Crater and together they provide information about past environmental conditions. As an example, sediment humification, which provides clues to surface moisture conditions at the time of deposition, suggests that the period from 9,500 to 7,500 cal y BP was relatively dry, which contrasts with previous palaeoclimatic inferences for this region. As different photosynthetic and metabolic pathways mean that the ratio of carbon/nitrogen can distinguish between aquatic and terrestrial sources of organic matter we analysed this ratio in 32 samples across the G2 core from Goochs Crater. These results suggests that aquatic sources of organic material dominated from 17,500 to 15,000 cal y BP and between 15,000 to 10,000 cal y BP conditions favored both aquatic and terrestrial sources. A rapid departure to highly terrestrial sources was evident at 10,000 cal y BP, after which a gradual change towards contemporary conditions, with a small aquatic influence, was evident.

While this demonstrates that much of the (contemporary) accumulating sediments at Goochs Crater are derived from within the site, it also receives inorganic aeolian materials from a larger source area.  To investigate this component we quantified the grainsize along the sediment profile to reveal that although clay content remains near constant (~ 5%) for the entire period, sand-sized particles shows a distinct increase in the period between 10,000 and 7,000 cal y BP before disappearing from the record. X-ray fluorescence scanning was also conducted on the G2 core resulting in elemental profiles for 32 elements at a very high (1mm) resolution. While the geochemical investigation of peat and organic sediments is in its infancy, several elements show considerable promise as palaeoenvironmental proxies. In our record, titanium, probably resulting from freshly weathered materials and washed in during periods of high surface runoff, is variable between 17,500 and 12,000 cal y BP, followed by sustained low values throughout the Holocene except for an abrupt, brief increase at 10,000 cal y BP followed again by high levels from 9,500 to 8,500 cal y BP. Bromine, which indicates the deposition of marine aerosols, shows an opposite trend to titanium, with low values until the early Holocene when a gradual increase begins, most likely indicating increased maritime influence on the hydrology of the site as sea level rose and stabilized in the post-glacial period.

In summary, it appears that Goochs Crater began accumulating organic sediments around 17,500 cal y BP, shortly after which a small, shallow lake developed and persisted in an otherwise sparsely vegetated landscape. The establishment of shoreline vegetation by about 15,000 years ago contributed to the accumulating sediments and this seems to have occurred under a climate of strong but variable westerly winds. A gradual but increasing oceanic influence affected the site until 10,000 cal. BP. before abrupt drying occurred. Increased sand present in the record during the early Holocene and other information suggests a relatively dry period. During the rest of the Holocene, the site returned to a wet, swampy environment: we are currently re-analysing the edge core with a broader suite of proxies to better characterize the late Holocene and it is envisaged that this will result in a complete moisture-focused palaeoenvironmental record from the site from 17,500 cal. BP to present. In the rest of this project (it will run until the end of 2016) we will finalize the interpretation of the other sites and the synthesis will provide a regional picture of palaeoclimatic influences on these important ecological communities. This work will also be compared to high-resolution fire histories that are being developed across the region.

Stakeholders, Funding and Acknowledgements. This research was funded through the Temperate Highland Peat Swamps on Sandstone Research Program (THPSS Research Program). This Program was funded through an enforceable undertaking as per section 486A of the Environment Protection and Biodiversity Conservation Act 1999 between the Minister for the Environment, Springvale Coal Pty Ltd and Centennial Angus Place Pty Ltd.  Further information on the enforceable undertaking and the terms of the THPSS Research Program can be found at www.environment.gov.au/news/2011/10/21/centennial-coal-fund-145-million-research-program. This work has benefited from discussion with Martin Krogh, Doug Benson, Sarsha Gorissen, Geoff Hope, Roger Good and Jennie Whinam.  This work has also been supported by a 2014 and 2015 AINSE Research Award (ALNGRA14019 and 15019) to SM.

Contact information. The project ‘Palaeoenvironments of sandstone peat’ is being undertaken by A/Prof Scott Mooney (School of Biological, Earth and Environmental Science (BEES) UNSW +61 2 9385 8063, s.mooney@unsw.edu.au), Professor James Goff  (School of BEES UNSW j.gof@unsw.edu.au) and Mr Len Martin (PhD candidate, School of BEES, UNSW, +61 2 9385 8063, lennard@student.unsw.edu.au).

A novel multispecies approach for assessing threatened swamp communities

Hannah McPherson and Maurizio Rossetto,

Key words:   Swamp conservation, chloroplast DNA, genetic diversity, landscape connectivity

Introduction. Little is known about the historical or present-day connectivity of Temperate Highland Peat Swamps on Sandstone (THPSS) in the Sydney Basin (NSW). Recent technological advances have enabled exploration of genetic complexity at both species and community levels.  By focusing on multiple plant species and populations, and investigating intraspecific gene-flow across multiple swamps, we can begin to make generalisations about how species and communities respond to change, thereby providing a solid scientific basis from which appropriate conservation and restoration strategies can be developed.

The study area comprised eight swamps distributed across four sites along an altitudinal gradient: Newnes (1200m); Leura (900m); Budderoo (600m); and Woronora (400m), see figure 1.

Map of the Sydney Basin region showing four study sites and eight swamps. Greyscale shows altitude gradient.

Map of the Sydney Basin region showing four study sites and eight swamps. Greyscale shows altitude gradient.

The aims were:

  • To assess the relative genomic diversity among target species representing a range of life-history traits. This was achieved by sequencing chloroplast DNA and detecting variants in pooled samples from 25 species commonly occurring in swamps.
  • To explore geographic patterns of diversity among swamps and across multiple species by designing targeted genomic markers and screening variants among populations within and between sites (for ten species occurring in up to 8 swamps).
  • To develop a set of simple, effective and standardised tools for assessing diversity, connectivity and resilience of swamps to threats (from mining to climate change).
Fig 2. Broad Swamp, Newnes Plateau (Maurizio Rossetto)

Fig 2. Broad Swamp, Newnes Plateau (Maurizio Rossetto)

Our study comprises three main components:

1. Species-level assessment of genetic variation of swamp species

We have taken advantage of new available methods and technologies (McPherson et al. 2013 and The Organelle Assembler at http://pythonhosted.org/ORG.asm/) to sequence and assemble full chloroplast genomes of 20 plant species from swamps in the Sydney Basin and detect within and between-population variation. This enabled a rapid assessment of diversity among representatives of 12 families and a broad range of life-history traits – e.g. table 1. We are currently finalising our bioinformatic sampling of the data to ensure even coverage of chloroplast data across the species, however these preliminary data show that relative estimates are not a product of different amounts of chloroplast data retrieved (e.g. for the seven species with sequence length greater than 100,000 base pairs variation ranges from absent to high).

2. Swamp-level assessment of variation and connectivity using three target species – Baeckea linifolia (high diversity), Lepidosperma limicola (low diversity) and Boronia deanei subsp. deanei (restricted and threatened species).

From the initial species-level study we selected three very different species for detailed population-level studies. We designed markers to screen for variation within and among sites and explore landscape-level connectivity. We identified the Woronora Plateau as a possible refugium and we have uncovered interesting patterns of gene-flow on the Newnes Plateau. Two species, Lepidosperma limicola and Baeckea linifolia seem able to disperse over long distances while Boronia deanei subsp. deanei showed unexpected high levels of diversity despite very limited seed-mediated gene-flow between populations. Its current conservation status was supported by our findings. A unique pattern was found for each species, highlighting the need for a multispecies approach for understanding dynamics of this system in order to make informed decisions about, and plans for, conservation management.

3. Multi-species approach to assessing swamp community population dynamics

Since the population study approach proved successful we expanded our study to include population studies for a further ten species. This required development of new Next Generation Sequencing (NGS) approaches applicable to a wide range of study systems. This kind of approach will allow us to make informed generalisations about swamp communities for conservation management planning.

Fig 3. Paddy’s Swamp, Newnes Plateau (Anthea Brescianini)

Fig 3. Paddy’s Swamp, Newnes Plateau (Anthea Brescianini)

Table 1. Preliminary results showing relative chloroplast variation among 25 swamp species. Sequence length is in base pairs (bp) and relative level of variation was calculated as sequence length divided by number of variants to obtain an estimate of number of SNPs per base pair.  Relative variation was then categorised as: High (one SNP every <1,000 bp); Moderate (one SNP every 1,000 – <5,000 bp); Low (one SNP every 5,000 – <10,000 bp); Very low (one SNP every >10,000 bp); or absent (no SNPs).

table

Fig 4. Banksia ericifolia (Maurizio Rossetto)

Fig 4. Banksia ericifolia (Maurizio Rossetto)

Results to date. We have assembled partial chloroplast genomes of 20 plant species from THPSS in the Sydney Basin and categorised relative measurements of diversity. Preliminary data from the three target species highlighted the need for multispecies studies and we are now finalizing our results from an expanded study (including 13 species) in order to better understand connectivity and resilience of THPSS and provide data critical for more informed conservation planning. We have produced unique, simple methods for assessing genetic diversity and understanding dynamics at both the species and site levels.

Lessons learned and future directions. We found that individual species have unique patterns of genetic variation that do not necessarily correspond with phylogeny or functional traits and thereby highlight the benefit of multispecies studies. We have developed a unique, simple method for screening for genetic variation across whole assemblages which can be applied to many study systems. Since our data capture and analysis methods are standardised it will be possible in the future to scale this work up to include more species and/or more geographic areas and analyse the datasets together to address increasingly complex research questions about the resilience of swamps in a changing landscape.

Stakeholders and Funding bodies. The following people have contributed to many aspects of this research, including design, fieldwork and data generation and analysis: Doug Benson and Joel Cohen (Royal Botanic Gardens and Domain Trust), Anthea Brescianini and Glenda Wardle (University of Sydney), David Keith (Office of Environment and Heritage).

This research was funded through the Temperate Highland Peat Swamps on Sandstone Research Program (THPSS Research Program). This Program was funded through an enforceable undertaking as per section 486A of the Environment Protection and Biodiversity Conservation Act 1999 between the Minister for the Environment, Springvale Coal Pty Ltd and Centennial Angus Place Pty Ltd. Further information on the enforceable undertaking and the terms of the THPSS Research Program can be found at www.environment.gov.au/news/2011/10/21/centennial-coal-fund-145-million-research-program.

Contact. Hannah McPherson, Biodiversity Research Officer, Royal Botanic Gardens and Domain Trust, Mrs Macquaries Road, Sydney 2000; Tel: +61292318181 Email: hannah.mcpherson@rbgsyd.nsw.gov.au