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world vegetation > exam 3 > Flashcards

exam 3 Flashcards

1
Q

mediterranean size

A
  • smallest biome as it only makes up 2% of the continental Earth with 5 distinct regions (California chapparal, Chile, Cape South Africa, Australia, Mediterranean
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2
Q

common geography of the mediterranean

A
  • subtropics 30-45 N/S
  • west coast of continents
  • cold off shore currents, maritime
  • topographically heterogenous (mixture of land surfaces/ forms– these areas are near mountain ranges)
    -fog desert
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3
Q

mediterranean physiognomy and functional characteristics

A
  • similar physiognomy and functional characteristics support the grouping

physiognomy
- sclerophyllous ; type of vegetation characterized by hard, leathery, evergreen foliage that is specially adapted to prevent moisture loss
- “fine” leafed

Functional characteristics
- response to winter rain and summer aridity
- role of fire; secondary succession– Secondary succession happens when a climax community or intermediate community is impacted by a disturbance. This restarts the cycle of succession, but not back to the beginning—soil and nutrients are still present.
- nutrient poor

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4
Q

mediterranean greatest affinities

A
  • chile and california
  • south africa and australia
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5
Q

mediterranean climate

A
  • winter: cool, wet: tm more or equal to 5C, frost can occur
  • summer: warm, dry: tm more or equal to 18C for 4 months
  • rainfall: 300-1000 mm, plus minus 65% in winter
  • summer drought affects growth of plants and sets up conditions for summer/fall fires
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6
Q

mediterranean soils

A
  • dissected relief; A dissected plateau is a plateau area that has been severely eroded such that the relief is sharp.
  • high erosion
  • hydro-orographic differentiation of soils –> many soil types
  • soils: shallow, infertile, low humus, low N and P, pH nuetral to basic, high clay content
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7
Q

mediterranean floristics

A
  • species diversity is high: Cape more or equal to 6,000 species
  • endemism (Endemism is the state of a species only being found in a single defined geographic location) high: disjunct regions, recent evolution
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8
Q

mediterranean plants: Mediterranean

A

wild olive, oaks, pines, cedars, juniper, lavender, thyme, rosemary, ericas, brooms

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9
Q

mediterranean plants: California

A

chamise, Ca. sagebrush, buckwheat, Ca. lilac, manzanita, oak

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10
Q

mediterranean plants: Australia

A

eucalyptus, casuarina, banksia

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11
Q

mediterranean plants: South Africa

A

protea, lecospermum, ericas

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12
Q

Family Proteaceae

A

come back to these slides

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13
Q

mediterranean life forms

A
  • predominantly phanerophytes (although not tall)
  • some cryptophytes
  • few therophytes (except after fire)
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14
Q

mediterranean lack of understory

A
  • mediterranean ecosystems show little vertical stratification (no understory)
  • this development of understory is prevented by low stature of phanerophytes (trees) and herbivory (deer for instance)

exclosure experiments: –> soil seedbank predators reduce seed numbers (ants, birds, rodents)
–> potential understory browsed (rodents, rabbits)

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15
Q

mediterranean adaptations to climate and soil – life forms

A
  • evergreen, sclerophyllous shrubs
  • drought- deciduous shrubs
  • cryptophytes, therophytes
  • C3 photosynthesis
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16
Q

C3 photosynthesis

A

. C3 requires cool and wet environments. C4 requires tropical and dry environments. 95% of the green plants are C3 plants.

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17
Q

mediterranean adaptations to climate and soil – adaptations to reduce water loss

A
  • small leaf size
  • ericoid leaf shape(small, tough (sclerophyllous) leaves)
    -leaf orientation
  • volatile oils (serve as protection for the plant. The essential oils are good deterrents of insects and other herbivores that may be looking for a snack)
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18
Q

mediterranean adaptations to climate and soil – adaptations to reduce herbivory

A
  • sclerophyll
  • fibres
  • tannins(They have been reported to be responsible for decreases in feed intake, growth rate, feed efficiency, net metabolizable energy, and protein digestibility in experimental animals)
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19
Q

mediterranean adaptations to climate and soil – poor soils

A
  • deep rooted or shallow rooted
  • proteoid roots : NOT hairs, clusters of short roots, true lateral roots –> determinate and not very long
  • mycorrhizae : increases phosphorous uptake
  • carnivory : trapped insects increase nitrogen uptake

cricoid mycorrhizal with hyphal coils in hair roots of Leucopogon verticillatus – saprophytic ability (breaking down things)

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20
Q

mediterranean fire characteristics

A
  • type: crown fire
  • intensity is more than savannas and very intense in Australia
  • extent is very variable – 400 to 10,000 ha
  • frequency – 10 to 80 years , higher in savannas, less frequent here
  • fuel characteristics – fine leaves shrub fuels with varying amounts of dead material, in some cases (ex. fynbos) herbaceous fuels co-occur
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21
Q

californian chaparral shrublands fire statistics

A
  • frequency: fires occur at intervals of between 25 and 100 years
  • season of fires: fires concentrated in dry summer periods
  • intensity of fires: fire intensities can be high (>50,000 kWm-1)
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22
Q

South African fynbos shrublands fire statistics

A
  • frequency: fires occur at intervals of between 5 and 40 years
  • season of fires: fires concentrated in dry summer periods
  • intensity of fires: fire intensities range from 500 to 30,000 kWm-1
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23
Q

Australian eucalyptus woodlands

A
  • some areas burn frequently, even annually (surface fires); stand-replacement crown fires can occur every 100-300 years in wet sclerophyll forests
  • season of fires: dry season
  • intensity of fires: usually low or moderate intensity (500-3000kWm-1) but can get up to high intensity crown fires (7000-70,000kWm-1)
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24
Q

mediterranean fire mosaic hypothesis

A
  • fire occurrence is self regulating and depends on the growth of the fuel
  • fire as a self regulating event influences ideas about: fire suppression (do we suppress or let it burn?) and frequency is increasing in some areas –> weedy vegetation
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25
Q

mediterranean fire response in vegetation

A

THE CYCLE OF VEGETATION FOLLOWING A CHAPARRAL FIRE IN SOUTHERN CALIFORNIA
- 1 year after fire: explosive growth of long dormant seeds and bulbs, perennial herbs appear, sprouted and seeder shrubs begin to be re-established

  • 2-4 years after fire: herbaceous perennial shrubs become more conspicuous
  • 5-9 years after fire: shrubs gradually become dominant, leaving less space for other plants
  • 10-50 years after fire: dense shrub cover with scant understory becomes increasingly vulnerable to wildfires in late summer and early fall
  • > 22-50 years after fire: decadence or senility occurs when thin layers of foliage are on the surface of shrubs, which consist largely of a thicket of dead branches (they’re old–> water transport may not be as efficient, not great growth)
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26
Q

mediterranean plant adaptations to fire

A
  • bark protection
  • resprouting – obligate (Obligate seeders are plants that can only regenerate after fire from seed) , facultative (These are species that regenerate post-fire by both seed and burl resprouting)
  • seed production – bradyspory (Bradyspory is the gradual release of seed from a cone or fruit over a long period of time), myrmechory ( ants bury seeds, seeds have eliasome which is a reward for the ant) , seed viability/ species age , seed germination (heat, charrate, smoke)
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27
Q

Mediterranean plant flammability

A
  • high surface area : volume
  • branching patterns
  • scleromorphic leaves
  • ribbon bark, e.g., Red Shanks –> peels back + hangs down –> “fire ladder”
  • chemical composition
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28
Q

evolution of flammability is debated

A
  • argument 1: little evidence for fire-adapted plant traits in mediterranean climate regions
    -argument 2: fire as an evolutionary pressure shaping plant traits
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29
Q

kill thy neighbor (versus mutch hypothesis)

A

-an individualistic argument for the evolution of flammability
- up the inclusive fitness of flammable species

  • enhanced flammability increases risk of neighbor mortality –> flammable plants exploit gaps created by burning, especially if they have additional growth advantages
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30
Q

mediterranean productivity and nutrient cycling

A

PRODUCTIVITY
- similar to temperate regions
- affected by water shortage / nutrient shortage
-variable

NUTRIENT UPTAKE
- poor soils
N fixation and mycorrhizae
carnivorous and parasitic plants
proteoid roots
sclerophylly
- nutrients are taken up during winter and stored

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31
Q

temperate grasslands geographic location

A
  • middle latitudes (40 N/S) , occur at lower latitudes associated with increased elevation
  • four major regions
    USA: prairies
    Eurasia: steppes
    Argentina: pampas
    South Africa: grasveld/highveld
  • regional names are also associated with distinct growth forms
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32
Q

temperate grasslands climate

A

seasonal – cool winters, warm summers (most rain)

  • temperature – summer: up to +- 25C average per month
    – winter: below freezing
  • rainfall – up to 700 mm y-1
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33
Q

temperate grasslands soils

A

-mollisols: well drained, good structure, rich in humus
- dark fertile soils formed from the accumulation organic matter produced by dense root systems of prairie grasses
- temperate climates with variable seasonal environments
- 21% of land in the United States
- most are cultivated

34
Q

temperate grassland growth forms

A

-dominated by grasses (hemicryptophytes)
-interspersed with - forms (therophytes) and trees (phanerophytes)
- gallery forest: are forests that forms as corridors along rivers or wetlands and project into landscapes that are otherwise only sparsely treed

  • distribution of growth forms and species diversity varies along environmental gradients, esp. along RAINFALL gradients (also temperature)
35
Q

temperate grasslands– factors affecting abundance of different growth forms and species diversity

A

USA – diversity increases to the S (longer growing season)
– diversity increases to the E (higher precipitation)

tall grass, mixed grass and short grass prairies from E to W

36
Q

tall grass prairies

A

more or equal to 2m
- andropogon gerardi
-panicum virgatum

37
Q

mixed grass prairies

A

1.25 m to 30 cm
- andropogon scoparius

38
Q

short grass prairies

A

20 - 50 cm
- drought tolerant short grasses
- bouteloua gracilis

39
Q

temperate grasslands– Eurasia

A

North to South: forest steppe, tuft-grass steppe, sagebrush – grass steppe

40
Q

temperate grasslands – growth habit

A
  • perennial
  • adapted to drought, fire and grazing
41
Q

temperate grasslands– bunchgrass

A
  • short, main stem axis
  • intravaginal tillering (“Tillering” refers to the production of side shoots)
  • occur in harsher environments
42
Q

temperate grasslands – sodgrass

A
  • loosely packed tillers
  • interconnected by underground rhizomes and stolons
  • occur in mild environments
  • water you would likely see in lawns
43
Q

temperate grasslands – selective advantage of bunchgrass under harsh conditions

A
  • holding space and competing with interspecific neighbors (very hard to pull out)
  • modification of microhabitat
  • concentration of nutrients and nutrient cycling
44
Q

temperate grasslands – selective advantage of sodgrasses

A
  • effective against erosion
  • rhizomes/stolons –> cryptophyte (buds protected from heat, cold and grazing)
  • store (CH2O)n aka carbohydrates in rhizomes/stolons
45
Q

temperate grasslands – roots

A

fibrous: course –> dry regions
fine –> wetter areas
- root stratification reduces competition
- surface roots increase absorption of rain

46
Q

temperate grasslands – xeromorphic adaptations

A
  • roots: shoot ratios increase drought (?)
  • leaf transpiration surface area is reduced by: small cell size, leaf rolling (bulliform cells), leaf shedding
    -stomatal position – adaxial
    – crypts
  • desiccation tolerance (he ability of an organism to withstand or endure extreme dryness, or drought-like conditions)
47
Q

temperate grasslands – hot temp responses

A
  • increase in the % of species with C4 photosynthesis
  • number of C4 species is greater in S and on S facing slopes
    -C3 species active earlier in the season
48
Q

temperate grasslands – cold temp response

A
  • bud dormancy
  • snow insulation
    -rhizomes and stolons
49
Q

temperate grasslands – productivity

A

-approximately 600g m-2 y-1
- productivity is seasonal
- factors limiting productivity include: rain, temperature, nutrients

  • lower productivity than temperate deciduous forest and tropical rain forest since too little rain and low temps
50
Q

temperate grasslands – nutrients

A
  • grasslands may be nutrient limited
  • N low due to: lack of legumes, low Azotobacter and Clostridium
  • N decreases with: grazing and tillage
  • plants maximize N by: nutrient recycling and rapid absorption
51
Q

temperate grasslands – decomposers

A
  • bacteria, fungi, nematodes, milipedes
  • distribution of decomposers is affected by temperature and water
  • decomposition and plant growth may not be synchronized
52
Q

temperate grasslands – effects of disturbance GRAZING

A

in the SHORT-grass prairies
- lowers productivity
- does not affect survival
- alters species composition – palatability effects, secondary succession
- increases erosion potential

in the LONG-grass prairies
- increases productivity
-increases light
- lowers carbohydrate accumulation inhibition

53
Q

temperate grasslands – effects of disturbance PRAIRIES DOGS

A
  • in short-grass prairies, the number of plant species, increases because the digging and scratching activities of prairies dogs disturb the soil
  • prairies dog burrows act as aquifers that prevent water from eroding land and help cool it
  • grasses and forbs on a prairie dog town are higher in protein and nitrogen and favored by bison, elk, and pronghorn
  • prairie dogs prefer open patches of grassland, and will move into heavily grazed patches of grassland
  • natural disturbances are an important part of maintaining the prairie ecosystem
54
Q

temperate grasslands – effects of disturbance FIRE

A
  • similar to savannas
  • bunchgrasses more susceptible
  • frequent burns increase weedy annuals and decreases trees
55
Q

temperate grasslands – effects of disturbance HUMANS

A
  • intensity drought effects – weedy forms
  • alter species composition – grazing
  • introduce species , e.g. Bromus arenarius in Eurasia
56
Q

“synthetic nitrogen fertilizers deplete soil nitrogen: a global dilemma for sustainable cereal production”

A
  • Dr. Mulvaney et al. suggest that agricultural soils are being depleted of their soil organic matter because of increased, and sustained, application of fertilizers. Furthermore, the article argues continuous and increased nitrogen application is increasing microbial decomposition of organic matter at an alarming rate, and will be reflected on the global level. this problem may be fixed if soils were aloud a rest, and native grasses were allowed to inhabit an area again. In reality now managed prairie soils are in danger of a slow change to less productive soils
57
Q

deserts– adaptations of plants to arid environments

A
  • adaptations reflect the impact of water stress on carbon economy
  • different strategies have different survival values versus growth potential

(1) Drought escaping
- ephemerals
-therophytes
- annuals
-opportunistic
(2) Drought resisting
a. drought avoiding
- water spenders (high water uptake, high growth rates)
-water savers (reduced water loss, high survival)
b. drought tolerating
-dehydration avoiding
-dehydration tolerating

58
Q

desert drought escape –therophytes

A
  • annuals complete their lifecycle in < 8 weeks
  • rainfall triggers germination and germination is rapid
  • life cycle is rapid
  • shows phenological/phenotype plasticity :
    - greater seed set in wet years
    - facultative selfing if pollinator not present
    - germination over a broad ranger of temperatures in some species
    - temperature specific niche separation
59
Q

desert – seed banks

A
  • soil
  • surface
    -variable densities
  • lowest in washes
  • distribution altered by foraging ants
  • foraging decreases densities but provides germination sites (ants) and seedling competition
60
Q

desert – heteroblasty

A

two types of seeds that differ in their level of dormancy
- 6 +- seeds
- 1 immediate germination
- 1 after 1 year
- other after several years

germination spread in time

61
Q

desert – amphicarpy

A
  • two distinctly different fruits

1st survival –> Subterranean
- larger
-more dispersed
- more drought tolerant
-moisture penetrates along root channels

2nd dispersal –> Aerial
- smaller
-wind dispersed
- do not develop in dry years

62
Q

desert drought avoidance – water spenders

A
  • high water uptake, high growth rates
    -spacing
    -root depth and lateral root spread
    -phreatophytes –a plant with a deep root system that draws its water supply from near the water table.

water spenders use transpiration to cool
Macrophyllous 23 kg H2O m-2
Microphyllous 2.9 kg H2O m-2

63
Q

desert drought avoidance – water savers

A
  • reduced water loss, high survival
  • e.g. succulents
    adaptations to WATER stress:
  • shape, low surface area to volume ratio
  • thick cuticle
    -CAM
  • succulence
    -mucilage
  • “rain roots”
    • surface roots maximize uptake from small rainfall events, grow under rocks
    • “rain roots” – reduce water loss from root area, gaps, increase input in response to rain

adaptations to TEMP stress
- succulence
- spines
-shape

establishment:
- nurse plants –overcome soil temp effects
- El ninon events
- proteinaceous layer beneath seed coat

disadvantage of the water saving strategy is slow growth

some strategies intermediate between spending and saving
- rough deciduousness
- C3 to CAM switch

64
Q

desert – drought tolerance

A

partial
- accumulate solutes to maintain turgor
- die at approximately 30% RWC

total
- resurrection plants
- dormant state physiologically similar to seeds
- lichens, moss, ferns
- angiosperms
- pioneers, little competition

65
Q

fog desert

A
  • dew and fog
  • leaf shape (nebulophytes)
    - Welwitschia mirabalis
    - narrow-leaves rosettes
    - “curly-whirlies” geophytes
  • Hydathodes
    -salt accumulators
    - appear to have water droplets on surface
    -lichens
    - also form part of the cryptobiotic crust in many deserts
66
Q

sand desert

A
  • Psammophorous plants
    - sand adheres to plant surface
    - reduces wind blasting
    - water ?
    -plants of sand dunes
    - very low species diversity
    - underground roots stabilize soil
    - growth stimulated by covering
    - internal dew formation
67
Q

saline desert

A

plants in saline areas of deserts show similar adaptations to those in coastal wetlands, salt glands, succulence, etc

68
Q

desert floras – evolution

A

-many life forms implies a long evolutionary history
- difficult to date origin – Miocene (?) 5 million ybp
- single ancient flora showed evolutionary divergence –> disjunct distribution of similar life forms

69
Q

desert floras – succession

A
  • slow
    -cyclic succesion maintains diversity
70
Q

desert floras – phenology

A
  • strongly influenced by rainfall (e.g. therophytes and leaf drops)
  • temperature extremes and seasons may be important
71
Q

desert – production

A

primary production
- lowest of all biomes
- reflects H2O limitation
- productivity correlated with annual rainfall and topography

72
Q

desert – nutrient cycling

A
  • water limited
  • litter dependent on drought stress
  • nutrients often concentrated near plants
  • soil organism activity is dependent on soil water
  • decomposers – termites, ants, millipedes
  • animal activity affects soil characteristics and vegetation: ants, heuweltjies (little hills), fairy rings
73
Q

desertification

A
  • the process by which fertile land becomes desert, typically as a result of drought, deforestation, or inappropriate agriculture
  • irreversible decrease in productivity (change in vegetation) or arid lands
74
Q

causes of desertification – irrigated croplands

A
  1. irrigated croplands, whose soils are often degraded by the accumulation of salts
    - evapotranspiration results in salt accumulation in surface soils
    - in the US, salt accumulation has lowered crop yields across more than 50,000 square km (19,000 square miles), an area that is about a 1/4 of the country’s irrigated land
75
Q

causes of desertification – rain-fed croplands

A
  1. rain-fed croplands, which experience unreliable rainfall and wind-driven soil erosion
    - crops grown are annuals
    - previously grasslands (mix of annuals and perennials) with 250-500 mm annual rainfall
    - rainfall varies year to year
    - crop failure common in drought years
    - wind erosion and abandonment of land (1% per year)
76
Q

causes of desertification – grazing lands

A
  1. grazing lands, which are harmed by overgrazing, soil compaction, and erosion
    - trampling destroys plants including plant roots that bind soil
    - soil erosion when it rains
    - reduce plant communities and alter the species composition
77
Q

causes of desertification – overconsumption

A
  1. overconsumption of fuelwood in dry woodlands
    - in africa and asia, wood is the principle fuel for heating and cooking
    - often converted into charcoal as charcoal produces less smoke
    - inefficient, up to 75% of the energy potential is lost
78
Q

causes of desertification – increased sedentary population

A

idk

79
Q

causes of desertification – climate change

A
  • more rapid with desertification
  • more variation in climate, increases desertification potential
  • hotter and drier conditions make desertfication more likely
80
Q

large scale solutions to desertification

A
  • economic and technical measures to reduce global warming
  • social and economic measures that support nomadic cultures
81
Q

local scale solutions to desertification

A
  • salt traps
  • cover crops and crop rotation
  • rotational grazing
  • terracing, wind breaks, dune stabilization

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