V6

Question 1

Ecosystem characteristics:

self-regulation

Answer 1

• stabilizing interactions

Question 2

Ecosystem characteristics:

ecological stability

Answer 2

• Ecosystem remains practically unchanged in its overall structure or in important characteristics (species composition, productivity, …) over longer periods of time (at least several centuries)
• can be found at any time in its highly ordered state
• under constant external conditions, population sizes of most species in a biocenosis fluctuate only slightly or only briefly around a mean value
• Term problematic, as ecosystems are dynamic

Question 3

Ecosystem characteristics:

ecological stability

Answer 3

• the “stability of ecosystems” does not exist !
• but rather various “stability properties”, which can be used to describe the durability of an ecosystem, its natural development dynamics and its reactions to possible disturbances
• the following stability properties are distinguished:
  
  • consistency
  • cyclicity
  • resistance
  • resilience (elasticity)

Question 4

Consistency and cyclicity:

Answer 4

Question 5

Example of cyclicity:

Mosaic cycle

Answer 5

Question 6

Resistance and resilience:

Answer 6

Question 7

Resilience (elasticity):

Answer 7

• = ability of ecosystems to compensate for sudden aperiodic external influences without sustainable system change
• e.g. disasters, human intervention, storm, fire, immigration of alien species (“invaders“, “invasive species”)
• classic example of an ecosystem with low resilience: tropical rainforest: low resilience after (extensive) clearing
• Most of the so-called “stable” ecosystems react particularly sensitively (little elastic) to external influences
• on the other hand: unstable ecosystems (e.g. successional stages and “used” ecosystems) usually react particularly elastically

Question 8

Resilience, reactivity, return period:

Answer 8

• Reactivity:
  
  • Intensity of the process triggered by a disturbance (time period from the beginning of the reaction to the disturbance to the maximum displacement (amplification)
• Resilience:
  
  • the greater, the shorter the return time and the quicker disturbances subside
• Return time:
  
  • reciprocal value of the resilienc

Question 9

What is the relationship between photosynthesis and temperature?

Answer 9

Question 10

What is the relationship between photosynthesis and radiation?

Answer 10

Question 11

What is meant by “water use efficiency”?

Answer 11

• ratio between production and water consumption
• dry matter formed per liter of transpired water

Question 12

What is meant by physiological and ecological valence?

Answer 12

• physiological range of existence / physiological valence:
  
  • each plant species, by its physiological constitution, can exist under wide ranges of environmental conditions
• ecological range of existence / ecological valence:
  
  • mutual displacement / enforcement
  • from more or less large parts of the physiological range of existence

Question 13

What does growth or defense mean?

Answer 13

Question 14

What is competition?

Answer 14

• interaction of organisms (of the same or different species) based on competition for limited resources
• intra- and interspecific competition

Question 15

Succession:

Answer 15

Question 16

Succession after disturbance:

Answer 16

Question 17

Succession after disturbance:

Answer 17

Question 18

Succession:

Answer 18

Question 19

Succession after disturbance:

Answer 19

Question 20

Ecological climatology:

Answer 20

Question 21

Ecosystem services of forests:

Answer 21

Question 22

Land-atmosphere interactions:

Answer 22

• climate-vegetation interaction
• energy and matter fluxes

Question 23

Climate services of forests:

Answer 23

• albedo
• evapotranspiration
• carbon storage

Question 24

Meso- and microclimate:

Answer 24

Question 25

Global radiation and energy balance:

Answer 25

Question 26

Energetic fluxes in plant stands:

Answer 26

Question 27

Where in a plant stand is the radiation balance greatest?

Answer 27

Question 28

Influence of solar radiation on vegetation:

Answer 28

• provides energy for photosynthesis ⇒ growth
• provides information about competition
• controls regeneration and establishment
• controls physiological processes, productivity
• initiates or prevents seed germination, stem growth, leaf development and orientation, flowering, dormancy

Question 29

Influence of solar radiation on vegetation:

Answer 29

• Only a part of the global radiation can be photosynthesized by plants:
  
  • photosynthetically active radiation (PAR) ~ 400 - 700 nm
  • about 50% of the energy supply by global radiation occurs in this wavelength range
  • biologically/morphogenetically active radiation (MAR) ~ 300 - 800 nm

Question 30

Photosynthetically active radiation (PAR):

Answer 30

Question 31

Spectral reflection:

Answer 31

Question 32

Radiation and structural properties:

Answer 32

• Structural characteristics such as growth habit, coniferous / deciduous tree, leaves and needles, tree crown, tree class, light and shade crown are decisive