Predicting Ecosystem Change in Response to Climate Change Scenarios: Plant Species and Community Responses

Transcription

1 Predicting Ecosystem Change in Response to Climate Change Scenarios: Plant Species and Community Responses John Volin, Arnold van der Valk, Paul Wetzel

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3 Wetland Hydrology Annual and interannual hydroperiods (water-level fluctuations) are the main drivers that control the development of landscape features. These include the composition of plant and animal communities, and the distribution and abundance of individual plant and animal species.

4 Hydroperiods can be described using harmonic analysis. Both the primary (annual) and secondary (interannual) harmonics of water-level fluctuations.

5 The maximum range in water level over an interannual cycle seems to be a good indicator of the number of vegetation zones found in a wetland. For prairie potholes, if the range is small (<5 cm), only one or two vegetation zones will be found, whereas a hydrologic range of > cm will create four or five vegetation zones (Stewart and Kantrud 97, van der Valk 5).

6 Sharitz & Pennings 6 Hydrology dominates the position and composition of vegetation communities

7 Stabilizing water levels compresses vegetation zonation Keddy

8 Variable hydrology creates Vegetation Mosaic cm gradient enough to change plant community Graminoid Marsh 7 d Eleocharis 5 d Forb Emergent arsh 6 d Brd Lvd/Mixed Evergreen Shrub 5 d Swamp Forest 6-8 d Floating Leaved Veg. 6 d Sawgrass d

9 Estimates of the interannual range (second harmonic) in the in ridge and slough landscapes of the Everglades is from data in McVoy et al (; Table., Figure., and Table A.). woody vegetation (tree islands) Emergent eleocharis marsh Emergent sawgrass marsh Floating-leaved aquatic (water lilies)

10 Idealized predrainage annual hydroperiods over a wet-dry cycle in the Everglades in wet, normal, and dry years.

11 Probable responses of plant assemblages that likely characterized the pre-drainage Everglades over a wet-dry cycle. Species Assemblage Wet Year Normal Year Dry Year Flood intolerant tree species Negative Neutral Positive a Flood tolerant tree species Neutral Neutral Positive a Sawgrass Negative Neutral Positive a Slough Species Positive Neutral Negative b Wet prairie species Positive Neutral Negative b a Negative with respect to increased fire damage. b Positive with respect to recruitment.

12 Climate Change Scenarios A- NP

13 Water Depth (ft) 6 - Gauge A Decrease Rainfall Increase Rainfall Decrease RF, increase ET Decrease RF, increase ET, no Canals Increase ET Increase RF, increase ET Base % time exceeded vs bins Water Depth (ft) 6 - Percent Time Value is Exceeded Gauge NP Percent Time Value is Exceeded

14 Annual Maximum Water Depths (ft) Annual Minimum Water Depths (ft) Gauge A Baseline Decrease RF Decrease RF, increase ET Increase ET Increase RF Increase RF, increase ET Year

15 Gauge A Increase RF Greatest Annual Maximum Minimum Range (feet) - - Baseline Decrease RF, increase ET Year

16 Annual Maximum Water Depths (ft) 6 5 Gauge A Increase RF Baseline Decrease RF, increase ET Annual Minimum Water Depths (ft) Year

17 Water Level (feet) Gauge A Baseline Daily Water Levels 7yr Average Baseline 7yr Average Increase RF 7yr Average Decrease RF, increase ET Year Gauge NP Water Level (feet) Year

18 Gauge A Increase RF Water Depth (feet) Water Depth (feet) Baseline Wet Year 6 Wet Year 6 Normal Year 6 Normal Year 6 Dry Year 6 Annual Hydroperiod Mean. ft.7 ft.5 ft Range.8 ft. ft.9 ft Interannual Hydroperiod Mean. ft Range 6.5 ft Dry Year 6 Annual Hydroperiod Mean.5 ft. ft. ft Range ft.5 ft. ft Interannual Hydroperiod Mean.8 ft Range 6.5 ft

19 Decrease RF, increase ET Water Depth (feet) Water Depth (feet) Baseline Wet Year 6 Wet Year 6 Gauge A Normal Year 6 Normal Year 6 Dry Year 6 Annual Hydroperiod Mean.5 ft. ft. ft Range ft. ft.6 ft Interannual Hydroperiod Mean.8 ft Range 6. ft Dry Year 6 Annual Hydroperiod Mean.5 ft. ft. ft Range ft.5 ft. ft Interannual Hydroperiod Mean.8 ft Range 6.5 ft

20 Summary () All of the climate change scenarios will result in little change in the range of water levels over interannual cycles. () This suggests that climate change driven changes in hydrology will not alter the number of vegetation zones in the Everglades. climate change per se will have little impact on the distribution and composition of vegetation types in the Everglades. () The length of interannual cycles may shift, mostly to longer dry phases in some scenarios. Other ecosystem features such as fire frequency could be affected. () The Everglades are currently declining because of a compression in the range of water-level fluctuations over a wet-dry cycle. Climate change will not reverse the compression, but it may be exacerbated by a decline in rainfall and increase in ET. (5) The scenarios of increases and decreases in rainfall seem unrealistic. Increases in rainfall are more likely to occur in the wet season.

21 Questions?

22 Annual Maximum Minimum Range (feet) Gauge NP Year Baseline Increase RF Decrease RF, Increase ET

23 Increase RF Gauge NP Greatest Annual Maximum Minimum Range (feet) Baseline Decrease RF, increase ET Year

24 Annual Maximum Water Depths (ft) Gauge NP Baseline Decrease RF Decrease RF, increase ET Increase ET Increase RF Increase RF, increase ET Annual Minimum Water Depths (ft) Year

25 Annual Maximum Water Depths (ft) Gauge NP Increase RF Baseline Decrease RF, increase ET Annual Minimum Water Depths (ft) Year

26 Gauge NP Increase RF Water Depth (feet) Water Depth (feet) - - Baseline - - Wet Year 6 Wet Year 6 Normal Year 6 Normal Year 6 Dry Year 6 Annual Hydroperiod Mean. ft. ft. ft Range.7 ft.7 ft. ft Interannual Hydroperiod Mean. ft Range.8 ft Dry Year 6 Annual Hydroperiod Mean.9 ft. ft. ft Range.7 ft.8 ft.5 ft Interannual Hydroperiod Mean.7 ft Range.7 ft

27 Decrease RF, increase ET Water Depth (feet) Water Depth (feet) Baseline Wet Year 6 Wet Year 6 Gauge NP Normal Year 6 Normal Year 6 Dry Year 6 Annual Hydroperiod Mean.5 ft. ft. ft Range ft.8 ft. ft Interannual Hydroperiod Mean. ft Range. ft Dry Year 6 Annual Hydroperiod Mean.9 ft. ft. ft Range.7 ft.8 ft.5 ft Interannual Hydroperiod Mean.7 ft Range.7 ft

28 Gauge A- 6 Annual Maximum Minimum Range (feet) Year Baseline Increase RF Decrease RF, increase ET