Investigating geomorphic and ecological recovery following the disturbance of dam removal. Desiree Tullos USGS November, 2008

Transcription

1 Investigating geomorphic and ecological recovery following the disturbance of dam removal Desiree Tullos USGS November, 2008

2 Ecosystem dynamics investigating common concepts Stability (Strahler (1957) and Hack (1960)) an open system in a steady state in which there is a continuous inflow and output of materials, in which the form or character of the system remains unchanged. Disturbance (sensu Townsend and Hildrew 1994) - a discrete event that leads to replacement of individuals by members of the same or different taxa

3 Flow disturbance=ecological benefits High flows - move sediment through the system and engage floodplain processes, necessary for fish spawning, nutrient processing/cycling, energy dissipation, deposition of fine sediments, etc. Low flows - create ideal conditions for maintaining food web components, dissolved oxygen, and habitats that are critical to all order of aquatic organisms.

4 Engineering disturbance = ecological disaster

5 Disturbance: Ecological view Temperton et al Environmental filters select species from regional pool

6 Environmental filtering and equilibrium Temperton et al. 2004

7 Disturbance and filtering in streams Disturbance modifies filters Food Stability Thermal regime (Poff et al. 2006) + Disturbance as a filter Magnitude survival Frequency reproduction Abruptness/timing colonizing

8 Disturbance: Geomorphic view Knighton 1998

9 Geomorphic adjustment and equilibrium Knighton 1998

10 Restoration: Parallels in recovery from disturbance? Geomorphic Recovery Ecological Recovery? = Knighton 1998

11 channel reconfiguration as restoration

12 channel reconfiguration as disturbance

13 habitat diversity Environmental Variables Upstream Restored # pools/60 meters Bankfull Width (m) Rural Agricultural Urban P- value Upstream Restored P- value Upstream Restored P- value % Vegetation Cover Epifaunal Substrate/Available Cover Variability in Velocity/Depth Regime Channel Flow Status Rapid Bioassessment Protocol Score Tullos et al. 2008

14 taxonomic differences Rural Agricultural Urban Diversity Upstream Restored P-value Upstream Restored P-value Upstream Restored P-value Shannon Functional Trait Tullos Tullos et al. 2006, et al. 2008

15 functional trait differences life history Life History Upstream Rural Restored Agricultural P- value Upstream Restored P- value Voltinism Univoltine _ Development Synchronization of emergence Multivoltine fast seasonal slow seasonal poor well Adult life span very short Tullos et al. 2008

16 functional trait differences - mobility Upstream Rural Restored Agricultural P- value Upstream Restored P-value Mobility Occurrence in drift rare abundant Maximum crawling rate very low low Swimming ability Strong weak Tullos et al. 2008

17 functional trait differences morphology and ecology Rural Agricultural Upstream Restored P-value Upstream Restored P-value Morphology Size at maturity small medium Ecology sprawl cling Habit swim Collector Gatherers Shredder Trophic Herbivore Tullos et al. 2008

18 indicator species Rural Upstream Helichus (IV=63; a =0.02) Dixa (IV=67; a =0.009) Rural Restored Chironomus (IV=72; a=0.04) Agricultural Restored Dixa (IV=60; a =0.03) Agricultural Restored Baetis (IV=57; a =0.04)

19 Restoration as a disturbance Parallels in geomorphic and ecological recovery? Stable habitats and channels Taxa replacement Disturbance traits: greater mobility ability to reproduce and grow rapidly opportunism in selecting habitat and food resources

20 Characterizing dam removal as disturbance How well-coordinated are ecological geomorphic recovery?

21 Inverts: Traits of hydrologic disturbance Small size High mobility Habitat generalism Ability to cling Streamlined body Two or more lifestages outside of stream Townsend et al. 1997

22 Inverts: Traits of dam removal disturbance? Geomorphic Mechanisms Movement of bed sediments Change in food web Refugia? Thermal regime?? Biological responses Small size High mobility Habitat and food generalism Grow and reproduce rapidly?

23 Describing Geomorphic Disturbance: Channel stability Channel evolution models Simon and Hupp 1986

24 Channel stability Erosion of bed/bank material

25 Geomorphic stability disturbance? Disturbance characteristics Rate Magnitude (disturbance and recovery) Direction Frequency Duration Spatial extent Legacy Sensitivity/resistance to/specificity

26 Geomorphic stability and disturbance with dam removal Rate Aspect ratio of knickpoint Magnitude (recovery channel stability?) RBS = Dgm/Dcbf = bkf/ critical = mobility ratio WDR, Wfpa/Wbkf, BHR Bar spacing Riffle pool frequency Rc/w Magnitude (disturbance) Stored vol/qs Direction Frequency Duration Spatial extent Legacy Sensitivity/resistance to/specificity Response reaches instream and riparian veg

27 The Brownsville dam removal: detectable disturbance?

28 Pre-removal bugs at Brownsville

29 Pre-removal bugs at Brownsville Upstream and DS1 Multivoltine Poorly synchronized emergence Streamlined body Swimmers Opportunistic feeders DS 2 Univoltine Well-synchronized emergence Common occurrence in drift Medium size at maturity

30 Change in bar width at cross sections (m) Geomorphologic response to Brownsville Far DS Reach Near DS Reach Upstream Reach Distance from Dam (m) Field Surveys Aerials DS1 to DS2 Dam

31 What are the parallels in ecological and geomorphic recovery from dam removal? Challenges Describing disturbance and recovery Spatial and temporal scales, methods for sampling Establishment of causation

32 Scales of dam removal recovery Project specific.

33 Process unspecific. Geomorphic Recovery Ecological Recovery Sequential? Parallel?

34 why linking recovery matters No problem can be solved from the same level of consciousness that created it.

35 why linking recovery matters When we try to pick out anything by itself, we find it hitched to everything else in the Universe.

36 For more information: Thank you. Questions? Comments?