Forest health and restoration in a drier and warmer world

Transcription

1 Forest health and restoration in a drier and warmer world Katinka Ruthrof Marleen Buizer, George Matusick, Joe Fontaine, Collin Ahrens, Paul Rymer, Donna Bradbury, Paul Rymer, David Tissue and Giles Hardy

2 Ecosystems in our Mediterranean-type climate region are projected to undergo considerable changes as a result of a shifting climate A number of forest die-off events have already occurred - impacting jarrah, marri, tuart, peppermint and banksia

3 Long term shift Protracted drought: Post-1970 s decline in rainfall in the Swan Coastal Plain region Flow on effects: Lake levels (e.g. Lake Cooloongup) have declined by up to 2 m since 1920 s Sommer and Froend 2010 Declining bore levels DoW 2008

4 Extreme events Precipitation Matusick et al Driest year on record 40-50% below average rainfall Temperature 2 nd warmest year on record 9 days greater than 35 o C Matusick et al. 2012

5 Study species: distribution and description Eucalyptus gomphocephala (Tuart) Endemic to the SW of Western Australia Restricted distribution to narrow coastal dunes Dominant or co-dominant forest or woodland species Life history characteristics similar to other temperate eucalypts: serotiny, post-disturbance regeneration, transient soil seed banks

6 Threats Complex history of disturbance: Clearing for housing and agriculture => fragmentation Rainfall decline (long and short term drought) Increasing temperature Hydrological changes Grazing by introduced species: damage to trees, compaction, erosion Feral animal grazing of understorey Altered fire regimes => lack of regeneration Loss of mycorrhizal fungi and bacteria Altered nutrition => further stress of canopy Result: in only ~30% remaining

7 Tuart collapse: south of Perth Lake Cooloongup Mass canopy collapse coincided with extreme drought and heat conditions in early (February and March) 2011 and found to be concentrated in distinct areas

8 Aerial photo: Brett Glossop Using a combination of remote sensing and field- based approaches: Characterizes the extent and severity of canopy collapse Quantified tree mortality Investigated associations between health and potential predisposing factors

9 Patterns In the affected area: ~90 ± 5% of trees damaged vs 6 ± 6% Mortality was low (3%) Crown retraction was 50 ± 7% vs 10 ± 2% Structural difference: 13.4m vs 23.1m Tree density in the unaffected area was 4.5 times higher

10 Patterns cont. Drainage patterns are different - the affected area: water shedding Potential causes of collapse: o Dropping groundwater levels, a shallow soil profile, drought and heat (Matusick et al. 2012) Implications: reproductive phenology (capacity to flower), seedbank dynamics (serotiny), resilience to fire, costs to fauna, costs to restoration (seed quantity)

11 =tkl7pztldqqchm:&imgrefurl= Without management intervention these woodlands will suffer local extinction We have choices as a society: No management intervention watch potential vegetation shifts Regeneration facilitation Revegetation or assisted migration using climate hardy provenances

12 Restoration: approach 1. Managing threats Increasing degradation clearing invasive species native herbivores 2. Reversing ecosystem degradation water infiltration compaction 3. Reintroducing species fauna flora fungi Adapted from Lamb 1994

13 1. Managing threats Clearing and fragmentation require sensitive planning, disincentives, biodiversity conservation grants Pest control: e.g. kangaroos, rabbits, weeds (e.g. kikuyu) Altered disturbance regimes: awareness raising and disincentives ch&tbnid=i0kkmxfnjgu3vm:& =0ahUKEwi50OGK8bjOAhUENJQKHSkkBZAQ_AUIBigB#imgrc=JKv0I6TGoL7V8M%3A Photo: Kat Sambrooks

14 2. Reversing ecosystem degradation Ameliorating existing conditions: Nutrients - run-off and water quality Competition - from weeds, other trees Erosion - riverbank stabilisation Moisture - water infiltration Compaction Photo: Kat Sambrooks

15 3. Reintroducing species The regeneration niche Collecting seed Growing seedlings local native plant nursery Planting seedlings not just putting plants in the soil Building faunal habitat Reintroduction of soil microbes, if required E.g. fungi and bacteria dling+growing+in+nature&imgrc=_dva RmTwNsf1RM%3A

16 Tuart: specific regeneration niche Post-fire, canopy gap regenerator, often in ashbeds Serotinous seed falls following fire Satiation of seed predators such as ants Transient soil seedbank ~6-12 months Mass recruitment, higher survival and growth rates on ashbeds (Ruthrof et al. 2002, 2003, 2010)

17 The ashbed effect Ruthrof et al Increases water infiltration and water availability (Hatch 1960) Reduces competition for resources (Wellington & Noble 1985) Reduces biological opposition to germination and growth (micro organisms, pathogens, herbivores) (Renbuss et al. 1973) Increases available nutrients (N and P) (Humphries & Lambert 1965) Reduces bulk density (Hatch 1960)

18 1. Raked ashbed 2. Bulked up seeds with sand 3. Broadcast seeded with tuart seeds 4. Raked lightly to protect from harvesters

19 No. seedlings/m Jun13 Sep13 Aug14 Time of monitoring (Ruthrof et al. 2015) Results: Good start, poor finish.. Key: protection from herbivores Requires further collaborative work with agencies

20 Creating Ash Beds - YouTube Peel Harvey Catchment Council overview&list=uutfgdmpoxstt_0ldbo8cp3g

21 Seed collection: Eucalyptus Location of seed collection sites permits provenance healthy trees in affected areas (resistance) Optimising seed collection timing throughout the year: serotiny amounts only 10% method: when valves are visible cost Collection and afterwards place into calico or paper bags dry passively store seed in fridge and/or send to nursery

22 Drought hardy provenances: previous and current work Eleanor O Brien: Jarrah from low rainfall sites had smaller stem diameters (perhaps reflecting slower growth). This could prevent drought stress. Trees from high rainfall site had the fastest growth and poorest survival at the drier site. Supports habitat matching (O Brien et al. 2007) Survival of jarrah over 18 months and emergence of marri were higher in local plants, providing at least weak evidence for local adaptation (O Brien and Krauss 2010) Donna Bradbury: Tuart seed source had no effect on early growth or survival. Optimizing environmental factors for establishment at the planting site will be more important for early restoration success (Bradbury et al. in prep) Trudy Paap/Cielito Marbus/Giles Hardy/Paul Rymer/ Collin Ahrens (current): Marri from different provenances are being grown at 3 sites across SWWA Examining survival, growth, response to heat, drought and biotic factors Marri were grown under drought conditions in the glasshouse those from drier sites had significantly higher survival than those from wetter sites.

23 Planting and seeding Ludlow 2007 Ruthrof et al Yalgorup, Lake Clifton 2012 Yalgorup 2009

24 Site preparation Ripping: reduces bulk density increases water infiltration stratifies the moisture profile, and increases rooting depth and survival - even in deep sandy soils Ruthrof et al. (2013) Ruthrof et al. (2015) Merely adding propagules may not ensure successful revegetation

25 Biochar+Typhoon Control Late planting Manutec x1 Manutec x2 Typhoon Survival (%) Cell Mean Temporal influences When do naturally occurring germinants establish successfully? Can we mimic this in revegetation activities? Seeding or planting early in the wet season Planting late in the wet season significantly reduced survival of seedlings Ruthrof et al. (2013) Tuart survival after 1 yr Interaction Bar Plot for survival Effect: plant treatment Error Bars: ± 1 Standard Error(s) Plant treatment Cell

26 Plant treatments Ruthrof et al. (2010) Ruthrof et al. (2013) Ruthrof et al. (2012) For some species and sites, control plants have very low establishment success For other species, the addition of nutrients increases survival - mimicking regeneration requirements?

27 Community/ restoration interface The involvement of the community through volunteering and citizen science cannot be underestimated in this field They should not be seen as merely a labour force These are hard working, enthusiastic, are reliable and have a growing expertise Drive conservation efforts into the future with a sense of stewardship They enhance the scale and quantity of scientific work possible Mutually beneficial: contributions and the needs of the restoration site and the humans involved in restoration (Ruthrof and Valentine 2011)

28 Community/ restoration interface cont. Volunteers do not reveal misconceived, romantic, or sentimental attitudes to historical landscapes They raised questions about translocation of species and because of possible unforeseen consequences for ecosystems as a whole They have nuanced thoughts on restoration and should interact with scientists and help develop restoration plans (Buizer et al. 2011)

29 Timetables Outreach/ Community involvement

30 Conclusions Forest health and ability to regenerate is being compromised Conservation will require the timely tracking of health changes to decipher past and future vegetation shifts o Provide evidence for how population contractions (or expansions) may occur o Inform ongoing management and restoration An understanding of the regeneration requirements, revegetation techniques and drought hardy provenances may increase revegetation success. This will become more important as: o some regions are projected to become hotter and drier o ecosystem degradation will become more prevalent o revegetation will become increasingly difficult Involvement of community is vital for continued conservation and restoration and will maintain connections between people and their environment

31 Acknowledgements Friends of Island Point Friends of Paganoni Swamp Men of the Trees, Peel Branch Department of Parks and Wildlife Peel Harvey Catchment Council City of Mandurah City of Rockingham Men of the Trees, Rockingham Fairbridge Trainees NowGreen Teams: Rockingham and Peel Veronica Ingrilli Colleagues: Katherine Sambrooks, Leonie Valentine, Michael Craig Katinka Ruthrof: For more information: