V5

Question 1

Structural features of the vegetation:

Answer 1

• Vegetation can be described by different characteristics:
  
  • height of vegetation cover
  • density of vegetation cover
  • root penetration depth / intensity
  • species composition !!!
  • spectrum of life forms !!!

Question 2

Structural features of the vegetation:

Answer 2

• in the course of evolution, a large number of species have evolved in adaptation to very different site conditions
• but at the same time only a small number of life and growth forms have developed

⇒ ​genotypic differences + similar appearance and function in the ecosystem (= ecological equivalence)

Question 3

Structural features of the vegetation:

Answer 3

• Description of a plant stand by:
  
  • species composition > plant communities
  • spectrum of life forms > plant formations

⇒ Plant formations give information about abiotic environmental conditions by their shape = physiognomic‐ecological vegetation units

⇒ different classification systems

Question 4

Life and growth forms:

Answer 4

• includes total habitus (size, shape, outline) and life span
• plants: especially the shape of the leaves, the type of branching, the degree of lignification or the location of the renewal buds
• animals: additionally the predominant nutrition, the degree of the mobility or prominent behaviors
• Life forms after RAUNKIAER

Question 5

Life forms after Raunkiaer:

Answer 5

Question 6

Ecosystem characteristics:

Answer 6

• Ecosystem turnover
• Growth or defense (primary vs. secondary metabolism)
• Plant interactions (competition, mutualism, niches, resilience, valence)

Question 7

Turnover:

Answer 7

• Net primary production (NPP) depending on site conditions:

1. duration of the vegetation period
2. global radiation
3. air temperature during vegetation period
4. water availability during vegetation period
5. availability of mineral nutrients
6. 1. ‐ 4. climatic

• further turnovers:
  
  • animal feed (=secondary production)
  • Litter decomposition
  • Humification
  • Mineralization
• Net ecosystem exchange (NEE)
• Ecosystem respiration:
  
  • R_eco = CO₂ release from soil + plant

⇒ NEE = GPP ‐ R_eco

Question 8

Change in primary production, biomass growth, litter and respiration:

Answer 8

• Ecosystems are dynamic, longest dwell time in the mature phase

Question 9

Model scheme of a natural/near‐natural ecosystem:

Answer 9

Question 10

Primary production:

photosynthesis and respiration

Answer 10

• light can be the limiting factor

Question 11

Phytomass and primary production in forest systems:

Answer 11

• esp. assimilation areas (LAI)

Question 12

Primary production and evapotranspiration:

Answer 12

• Water use efficiency (g formed dry substance / liter of transpired water)
• Relation between production and water consumption

Question 13

Secondary production (animal feed):

Answer 13

• Animals:
  
  • heterotrophic creatures
• nutrition directly or indirectly from organic products of primary producers
  
  • Consumers
  • Secondary producers
  • Biofages (live substance eaters):
    
    • herbivores, carnivores, omnivores
  • Dead substance eaters:
    
    • detrivors ( ⇒ together with bacteria / fungi (saprobionic plants): decomposers)
  • quantitative importance of biophages:
    
    • a few percent of the above‐ground phytomass eaten by herbivores

Question 14

Four main groups of heterotrophic organisms:

Answer 14

Question 15

Mineral turnover:

Answer 15

Question 16

Primary and secondary metabolism:

Answer 16

• Trade‐off between primary and secondary metabolism
• what is put into defense is no longer available for growth
• Secondary metabolites often “expensive“

Question 17

Plant defense:

Answer 17

• Response to stress caused by environmental conditions (pests, climate, air pollution, scarcity of resources, competition, …)
• New production of secondary metabolites
• Supply of secondary metabolites
• “Toxins”
• “Warning signals”
• “Calls for help”
• Triggering of numerous functions (e.g. maturation)

⇒ not absolutely necessary for cell survival but useful or necessary for the whole organism

Question 18

Plant defense, Example:

desert mugwort (Wüsten‐Beifuß) and wild tobacco

Answer 18

• in one group mugwort pruned, other group unchanged
• emission of VOCs
• tobacco near the pruned mugwort plants switches metabolism to defense
• significantly less feeding damage by locusts
• “eavesdropping” on neighboring plants / species

Question 19

Interaction of individuals of the same or different species:

Answer 19

• Competition
• Mutualism (mutual benefit)
• Dependence on environmental conditions

⇒ Result: site‐specific species clusters

⇒ Plant communities and formations

Question 20

Ecological niche:

Answer 20

• The entity of environmental factors that a uniform group of plants or animals (e.g. species) needs for their survival
• biotic and abiotic factors combine to form a multidimensional hyperspace
• functional relationship between a species and the ecosystem
• within the niche space: competition, mutualism, symbioses

fundamental niche ⇔ realized niche

Question 21

Competition:

Answer 21

• nteraction of organisms (of the same or different species) based on competition for limited resources
• intra‐ and interspecific competition
• mind‐experiment: pure vs. mixed culture
• Picture:
  
  • Species 2 could also grow under extreme conditions, but is displaced by more competitive plants under these conditions

Question 22

Physiological valence:

Answer 22

• every plant species can exist from its physiological constitution under wide ranges of environmental conditions

⇒ physiological range of existence / physiological valence

• depending on the intensity of the influencing factor, different growth and distribution
• range of highest production output: physiological optimum

Question 23

Ecological valence:

Answer 23

• in case of occurrence of several species: mutual displacement/enforcement from more or less large parts of the physiological area of existence ⇒ ecological subsistence area / ecological valence
• ecological optimum
• ecological and physiological optimum coincide only in a few cases (mostly at the physiological edge)
• misleading or wrong: “drought loving”, “in need of warmth”, “lime seeking”
• species only more competitive ⇒ “drought‐bearing”

Question 24

Effects of competition:

Answer 24

• intraspecific competition for water, nutrients and radiation
• e.g. same total biomass production with different numbers of individuals of the same species (e.g. three or six Lolium perenne and three Daucus carota plants)
• die off of the “weak” individuals ⇒ Selection of the best adapted individuals ⇒ Optimization of the genetic adaptation of the species
• interspecific competition
• e.g. three Lolium and three Daucus plants
• Lolium biomass almost as in pure culture
• Daucus biomass only at about 10% of the possible biomass
• total biomass (Lolium + Daucus) same as before
• with a three‐week growth advantage of Daucus:
  
  • Lolium only 40%
• at three‐week growth advance of Lolium:
  
  • Daucus practically at 0
• Adaptation to competition:
  
  • little energy in generative apparatus, more in height growth
• e.g. with Daucus ahead:
  
  • Lolium compared to normal growth 40% stalk and leaf biomass, only 20% ear biomass (few seeds) ⇒ less offspring ⇒ extinction after some generations
• Competition for nutrients and water underground, light above ground

⇒ Plant individuals recognize competing individuals very early via their photoreceptors (e.g. by the red/far red ratio)

Question 25

***Mutualism (mutualistic symbiosis):***

Answer 25

* Interrelation between living beings of two species * at least one partner benefits compared to living alone, the second partner is at least not affected * Increase of the competitive strength * Colonization of more extreme habitats * Improvement of absorption of water and minerals * Making nutrients available from deeper layers * Water storage in cushions ⇒ positive interaction * *_Examples:_* * Central European forest trees and mycorrhiza * organization form of lichens (algae + fungi) ⇒ ‐196°C to +70°C

Question 26

***Plant interactions:***

Answer 26

* each plant individual is involved in a permanent network of relationships between all stand individuals * competition is essential relationship * but also mutual support

Question 27

***Influence of plants on environmental variables:***

Answer 27

* plants influence existential requirements of other species but also of the own species (rejuvenation) * *_light / radiation:_* * strong reduction ⇒ strong selection of species due to lack of light * *_precipitation:_* * interception, fog scavenging ⇒ increase, decrease or redistribution in the stand * *_soil water content:_* * by evapotranspiration lowering of the groundwater level ⇒ drying of the upper soil layers * s*_oil nutrient content:_* * conifers ⇒ acid tolerant plants are grown; Robinia ⇒ N cycle

Question 28

***Ecogram:***

Answer 28

Question 29

***Ecosystem characteristics:*** ***dynamic equilibrium***

Answer 29

* quasi-stationary state of an ecosystem during an observation period (inputs and outputs of energy and matter in equilibrium)