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ha
Landscape
Region
1/10 ha
Week Month Year Decade Century
Landscape Dynamics ForestSelection
Tree
Disease
Forest Competition
Species Selection
Species Competition
BiomeSelection
BiomeCompetition
Insect
Scale Uncertainty 6
Global Change Certainty across Southeastern United States Ecosystems:
Impacts and Implications
Steven McNulty
Research Ecologist
USDA Forest Service
Raleigh, NC
7
Very Likely Impacts In Southeastern Forests(independent of climate change)
Increased Population
Increased Fuel loads
11
This will lead to…
Further forest fragmentation
Further restrictions in forest management options
Increase Fire Severity and Frequency
16
Likely Impacts In Southeastern Forests(with and without climate change)
Inter-annual precipitation variability
18
Percent of the continental USA with a much above normal proportion of total annual precipitation from
1-day extreme events (more than 2 inches or 50.8mm)
Karl et al. 1996
BW 7
19
Likely Impacts In Southeastern Forests(with and without climate change)
Inter-annual precipitation variability
Extended growing season and warming
26
> 25% DECLINE
5%-25% DECLINE
<5% CHANGE
5%-25% INCREASE
Timberland Acreage Shift 1993 – 2040: No Climate Change Baseline
30
Timberland Acreage Shifts by 2040 Due to Hadley Climate Change
5%-25% DECLINE
<5% CHANGE
5%-25% INCREASE
31
Unknown Impacts In Southeastern Forests(dependent of climate change)
Increasing CO2 on forest growth
Insect and disease impacts
Integrated stress impacts
35
How a different critical nitrogen load could be determined within the same ecosystem
N dep = 10 kg/ha/yr
N leaching = 0Mortality = 0%
Critical N > 10 kgLoad
N dep = 10 kg/ha/yr
N leaching = 1Mortality = 10%
Critical = 10 kgLoad
+ 3 yr Drought Stress
N dep = 10 kg/ha/yr
N leaching = 15Mortality = 75%
Critical = 8 kgLoad
+ 3 yr Drought Stress
+ insects
N dep = 10 kg/ha/yr
N leaching = 25Mortality = 100%
Critical < 5 kgLoad
+ 3 yr Drought Stress
+ insects
S dep = 10 kg/ha/yr
36
Conclusions
• There is sufficient certainty regarding several areas of global change for assessing probable ecosystem impacts across the southern US during the next 50 years
• Other less certain impacts need to be prioritized for future research study based on cost and potential impact
• Synergistic impacts will be very difficult, if not impossible to predict
37
Conclusions (cont.)
• Thresholds and positive feedback impacts are poorly understood and could have the greatest potential for catastrophic change
• More emphasis should be placed on coping and mitigating those impact which have a high probability of occurrence while time and funding exist to address these issues
38