ESS 411
Professor D. Cusack
Midterm 2: Review concepts and processes from special topics/guest lectures
Thresholds
Carbon Cycle feedbacks (Steffen et al 2018)
Hothouse Earth Pathway
Biogeophysical Feedbacks
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Negative – Maintain trajectory of the Earth System in a given state (Holocene-like conditions)
o Carbon uptake by land and ocean systems
Positive – Can amplify a perturbation and drive a transition to a different state
o Permafrost Thawing
o Relative weakening of land and ocean physiological C sinks
o Increased bacterial respiration in the ocean
o Amazon forest dieback
o Boreal forest dieback
Alternative Stabilized Earth Pathway
Human Feedbacks in the Earth System
-
-
Negative – to steer the Earth System toward Stabilized Earth
o Reduce greenhouse gas emissions
 Changes in behavior, technology and innovation, governance and values
o Enhancing or creating carbon sinks
o Modifying Earth’s energy balance systems
 Solar radiation management
Positive
Planetary thresholds
2oC
Dead zones
Phase space and ecosystem dynamics
Oscilations and equilibrium
The paradox of enrichment (productivity, return times, and feasibility)
Oscilations and equilibrium
Global Water Cycle and Change
Major fluxes and pools in global water cycle (Abbott 2019)
Pools (103km3):
Fluxes (103km3 * yr-1):
Atmosphere over land: 3.0 ± 10%
Total Human Water Appropriation: 24 ± 20%
Snowpack (annual maximum): 2.7 ±20%
Green Water Use: 19 ± 20%
Ice Sheets and Glaciers: 26,000 ± 10%
Blue Water Use: 4.0 ± 30%
Atmosphere over Ocean: 10 ± 20%
Grey Water Use: 1.4 ± 40%
Saline Lakes: 95 ± 10%
Land Precipitation: 110 ± 10%
Reservoirs: 11 ± 40%
Land Evapotranspiration: 69 ± 10%
Fresh Lakes: 110 ± 20%
Ocean to land atmospheric flux: 46 ± 20%
Permafrost: 210 ± 100%
Ocean Precipitation: 380 ± 20%
Rivers: 1.9 ± 20%
Endoheic Discharge: 0.8 ± 30%
Wetlands: 14 ± 20%
Land Ice Discharge: 3.1 ± 40%
Biological Water: 0.94 ± 30%
Ocean Evaporation: 420 ± 20%
Soil moisture: 54 ± 90%
Groundwater Recharge: 13 ± 50%
Renewable Groundwater: 630 ± 70%
Groundwater Discharge to Ocean: 4.5 ± 70%
Non-Renewable Groundwater: 22,000 ± 80%
River Discharge to Ocean: 46 ± 10%
Surface Ocean: 130,000 ± 30%
Interbasin Ocean Circulation: 5,000 ± 20%
Deep Ocean: 1,200,000 ± 8%
Vertical Ocean Circulation: 2,100 ± 30
Anthropogenic interferences in the global water cycle (Abbott 2019)
Human activity alters the water cycle in three distinct but interrelated ways.
1. Green Water Use: Water appropriation through livestock, crop, and forestry use of soil moisture
2. Disturbance of ¾ of ice-free land surface that includes agriculture, deforestation, and wetland
destruction
3. Climate Change
Emissions and Climate Change Mitigation
Global carbon budget, major sources of emissions, sinks
relative sizes of carbon fluxes
Green House Grass Effect
The Kaya identity
Class discussion on CO2 drawdown options
Nitrogen Deposition
Reactive nitrogen sources
Nitrous Oxide (N2O)
Nitrogen Oxides (NOx)
Ammonia (NH4)
Ammonium nitrate (NH4NO3)
Sources: Primarily Fossil fuel combustion and agriculture
The nitrogen challenge
-
Feed the worlds growing populations, while reducing N Deposition
Environmental impacts of nitrogen
-
Smog/Haze
Loss of Biodiversity
Acidification
Eutrophication & Dead Zones
Climate Change
Ozone Holes
Nitrogen cascade
-
-
Fossil fuel combustion releases Nitrous Oxide (N2O) and Nitrogen Oxides (NOx)
o This impacts GHG balance, Urban Air Quality, Stratospheric ozone losses, and
Tropospheric ozone formation
Agricultural practices also release Nitrous Oxide (N2O) and Nitrogen Oxides (NOx)
o As well as Ammonia (NH4)
 When NH4 and NOx react it creates Ammonium nitrate (NH4NO3) and attach to
Particulate Matter which falls as dust or enters the water cycle as rain and
when it enters terrestrial ecosystems can cause Terrestrial Eutrophication, Soil
Acidification, and Freshwater Eutrophication
 These same outcomes can occur from NO3 leaching out of ag systems
 This then leads to Nitrate (NO3) in streams, groundwater, and coastal
seas, which ultimately results in Marine Eutrophication
N deposition effects on RMNP alpine ecosystems
-
-
-
-
Changes Alpine vegetation composition
o Wildflowers to more grasses
Forest biogeochemistry
o Tree foliar chemistry Eastern RMNP vs. Western RMNP
 Higher needle and soil N
 Lower C:N ratios
 Higher soil mineralization and nitrification rates
Soil Chemistry
o Mineralization/Nitrification
Control
Fert
max
min
max
min
pH
5.2
4.9
4.8
4.4
pH lower in fert by approximately 0.4 - 0.5
%C
38
30
32
28
Soil Carbon Content Lower in Fert by around 4%
Microbial
2.75
1.75
2.25
1.25
Biomass
Microbial biomass carbon lower in fert by approximately
Carbon
0.5 mgC/g dry soil lower
B:F
7.5
3
6
1.5
Soil microbes, fungi, food webs
Arbuscular
3.60
2.95
2.55
2.10
Mychorrizal
Mychorrhizal Fungi lower in fert by approximately 0.45 - 1.05 mol%
Fungi
Saprotrophic
18.5
16.0
17.5
13.0
Fungi
Sap fungi lower by approximately 1-3 mol%
o Higher average biomass/kg dry soil in fertilized areas for all trophic groups
o Nematode Community Composition of fertilized areas
 Higher proportion of Predaceous, Omnivorous, and Bacterial Feeder nematodes
 Lower proportion of Fungal feeding and plant parasite nematodes
Lake and Stream Chemistry
Lake algal assemblages
Lake productivity
P deficiency in zooplankton
CSU nitrogen emissions
-
Goals: 25% reduction
Sources of Nitrogen at CSU – 110 metric tons
o Utilities – 46 metric tons
 Other – 12 metric tons
 Purchased electricity – 32 metric tons
 Transmission and distribution losses – 2 metric tons
o Transportation – 10 metric tons
-
 Direct – 2 metric tons
 Air travel – 3 metric tons
 Staff – 1 metric tons
 Students – 5 metric tons
o Food Production/Consumption – 0 metric tons (offset by compost)
 Dining halls and LSC – 50 metric tons
 Compost (nitrogen offset) – 50 metric tons
o Research Animals & Agriculture
 Work w/ one another?
o Fertilizer – 45 metric tons
 Fert – 45 metric tons
CSU Nitrogen Footprint Network
o Small group of institutions working to reduce nitrogen output in higher ed
o Originated from UV- Jim Galloway and Allison Leach
o Funded by EPA
Soil Carbon
Drivers of soil carbon cycling
-
Physical – Temperature and moisture
o Strong dependency and feedbacks to climate
Chemical – Nutrients, pH, Mineralogy
o Dependency on N deposition, environmental, and land use change
Biological – Plant, microbial, and soil fauna traits
o Dependency on land use, vegetation cover, management
Relative quantities of C in soils vs. atmosphere, impact of soil C losses
-
Soil
o
-
0-30 cm
 Nitrogen – 50 Pg C
 Carbonate-C – 200 Pg C
 Organic Carbon – 750 pg C
 Total C – 1000 Pg C
o 0-100 cm
 Nitrogen – 100 Pg C
 Carbonate-C – 800 Pg C
 Organic Carbon – 1400 Pg C
 Total C – 2300 Pg C
o 0-200 cm
 Organic Carbon – 2500 Pg C
Atmosphere – 800 Pg C
Global distribution of soil C stocks
-
Belowground
o NPP
o Belowground allocation
Modes of soil C storage/stabilization
-
Mechanisms
o Intrinsic
How decomposition works
CO2 fertilization effects on soil C storage
Humification
Idea of carbon saturation in soils
Deforestation and Forest Management under Climate Change
Global patterns of deforestation and afforestation over last 200 years
-
Has primarily been occurring in tropics and boreal forests
Different successional trajectories after tropical deforestation
Deforestation effects on ecosystem properties and processes, and feedback to global change
-
Negative effect on
o Plant growth
o Carbon storage
 AGB decrease
 Roots decrease
 Soil (mixed)
-
Neutral effect on
o Nutrient Availability
 N (decrease)
 P(mixed)
 Base Cations (m)
o Biodiversity
 Plant (decrease)
 Insect (decrease)
 Microbes (increa)
-
Positive effect on
o Disturbance Regimes
 Fire (increase)
 Flooding (increase)
 Drying (increase)
 Local Warming (Incre)
Climate Change (warming), CO2 fertilization and Unmanaged landcover change (grass and farm invasion)
all have positive relationships with deforestation and the above ecosystem responses<
Reforestation effects on ecosystem properties and processes, and feedback to global change
-
Secondary Forest Regeneration
o Has positive relationship with
 Plant growth
 Carbon Storage
 AGB (increase)

 Roots (mixed)
 Soil (no change)
Disturbance Regimes

No known
effect


Nutrient Availability
 N (increase to baseline)
 P (decrease to baseline)
Biodiversity
 Plant (increase)
 Animal (increase)
Invasive grass/herbaceous effects on tropical forest ecosystem properties and processes, and
feedback to global change
Invasive grasses (introduced for agriculture) can be permanent changes to environments
Management approaches for forest adaptation to and mitigation of climate change
Assumptions
-
Future environments will be different from present
Can’t be certain about specifics of change
Toolbox approach
-
No “one size fits all”; need flexibility and site-specific approaches
o Try many different adaptation and mitigation methods
 Adaptation Strategies
 Resistance to Change (avoidance)
 Resilience to Change (bounce back)
 Management Response/Preparation for change
o Assist transitions, population adjustments, range shifts, and
other natural adaptations
o Increase redundancy and buffers
o Expand genetic diversity w/in and among species
o Manage for asynchrony and use establishment phase to reset
succession
o Establish novel-native forests
o Promote connected landscapes
o Realign significantly disrupted conditions
o Anticipate surprises and threshold effects
o Experiment with refugia
 Mitigation Strategies (referring to climate change)
 Reduce GHGs
o Reduce CO2 and other GHG emissions
o Sequester C in plants and soils