Lecture 12 Flashcards
(11 cards)
What is the biosphere?
The entire global ecosystem, including living organisms and the environment (from which they get energy and nutrients)
How does increased temperature affect precipitation?
Increased temperature means more rainfall. Combined with changing rainfall (as a result of climate change), this results in reductions in soil moisture
What is the difference between the composition of savannas and forests?
Forests are made up of mostly trees, while savannas are composed of trees and grass. As a result, savannas have frequent fires, while forests do not have fires
Describe the positive feedback loop concerning fires in a typical savanna
Typically, open canopies allow grass to grow/cure. More grasses lead to fires. Fires kill trees or prevent them from establishing. This leads to a savanna environment, which reinforces the open canopy (less trees)
Describe the positive feedback loop concerning fire in typical forests.
The closed canopy prevents grass from growing. Less grass leads to a lack of fires. A lack of fires means trees survive and establish. Many trees leads to a forest environment, which reinforced the closed canopy.
What are alternative stable states?
Two different types of ecosystems in existing in the same environment
What is ecosystem resilience?
The capacity of a system to absorb perturbations + variability to recover from disturbances.
Describe the negative feedback loop that occurs when fires happens in forests.
Fire causes trees to die.. This leads to an open canopy, allowing grass to invades. More grass leads to more fire
Name an example of an alternative stable state?
The experimental lakes area is an example of an alternative stable state ecosystem where scientists study how changes in nutrient levels can case a lake to shift between clear water (dominated by aquatic plants) and a turbid state (dominated by algae).
What is hysteresis?
It is dependence of the state of the system on its history. More specifically, it is when the path to recover from a disturbance is different from the path taken to cause the disturbance. It is a hallmark of bistability.
What are the three main takeaways regarding resilience of the biosphere?
- Increasing atmospheric CO2 (and CH4 and N20) is resulting in warming and changing precipitation patterns.
- Biosphere responses to these changes depends on their resilience
- Systems with alternative stable states can experience large and irreversible changes in response to disturbances and/or changes in the environment - responses can depend on the state of system (hysteresis)
