exam 1 Flashcards
vegetation
plants considered collectively, especially those found in a particular area or habitat. can speak of its appearance (physiognomy) size, spacing, and seasonal changes
biome
a major terrestrial climax community defined by the physiognomic similarity of the dominant plants
requirements for plant growth
interplay of climate (light, water, temperature) and soil (inorganic nutrients) determine the suitability of the environment for plant growth
Climate
-is the long term expected weather of an area (at least 30 years)
-includes the region’s general pattern of weather conditions, seasons and weather extremes like hurricanes, droughts, or rainy periods
-air temperature and precipitation are the most important factors
climate diagrams
- includes average temperature (in C) on the left and average rainfall (mm) on the right, per month
-includes years and lat + longitude + altitude
solar constant
is the amount of solar energy that falls per second on an area of 1m^2 above the Earth’s atmosphere that is at right angles to the sun’s rays
- average value is about 1400 Wm-1
incoming solar energy is 100%
-6% reflected by the atmospere
- 20% reflected by the clouds
- 4% reflected from earth’s surface
-16% absorbed by atmosphere
around 51% absorbed by land and oceans
-atmosphere is heated by conduction of heat from the Earth’s surface
solar input and latitude
- solar input is directly related to the latitude –> and heating is greater at lower latitudes
- heating is most intense when incoming solar radiation strikes perpendicular to the earth’s surface (directly overhead)
- the higher latitudes are cooler than the tropics because the same quantity of solar radiation is dispersed over a greater surface area and because the same quantity of solar radiation must pass through a thicker layer of the filtering atmosphere
Earth’s rotation, solar radiation and seasons
- the earth rotates about its axis, which is tilted at 23.5 degrees, this results in the earth’s seasons –> whichever hemisphere with most direct interception of light experiences summer
- sun’s rays perpendicular to the Tropic of Cancer (23.5 N) – Northern Hemisphere summer solstice (June 21)
- sun’s rays perpendicular to the Equator (0) –Equinox (21 March and 21 September)
- sun’s rays perpendicular to the Tropic of Capricorn (23.5 S) – Northern Hemisphere winter solstice (December 21)
Wind’s components
-Vertical component: “Hadley Cell” + “hot air rises” , equatorial heating causes moisture laden air to rise, sets up patterns of atmospheric circulation
-Horizontal component: surface winds move from high to low pressure, deflected by Earth’s rotation
ascending air cools –> rain
descending air heats –> dry
Hadley Cell
- air warms and rises
- cooling as it travels up, cannot hold as much moisture causing rain
- from higher pressure to lower pressure so descends down where it warms again
ocean currents
- surface circulation is driven by the winds
- Northern hemisphere: clockwise gyres
- Southern hemisphere: anti-clockwise gyres
W-coast = COLD
E-coast = WARM
rainfall patterns
average annual precipitation is a function of:
-latitude
-elevation
-distance from moisture sources
-position within the continental land mass
-prevailing wind direction
-relation to mountain ranges
-relative temperatures of land and bordering oceans
rainfall pattern – mountain ranges
-evaporation causes moisture air to rise
-wind pushes moist air towards the mountain where rain then ensues and trickles down the mountain side
- dry air then continues to travel to the other side of the mountain which creates a hot side of the mountain range called a rain shadow
- adiabatic lapse rate: rate of cooling ascending v heating descending (faster), dry air heats faster than humid air cools
irregular climate fluctuations – ITCZ
- the Inter-Tropical Convergence Zone, the solid band of clouds may extend for many hundred of miles and is sometimes broken into smaller line segments
- ITCZ follows the sun –> most places get higher rainfall in the season of high sun (except Mediterranean climate)
-position varies seasonally. it moves north in the northern summer and south in the northern winter. the ITCZ is responsible for the wet and dry seasons in the tropics
irregular climate fluctuations – El nino
- the southern oscillation refers to changes in sea level air pressure patterns in the Southern Pacific Ocean between Tahiti and Darwin, Australia
- El Nino refers to the warm episode of ENSO while the cool episode of ENSO is called la nina
Microclimate
- southern slopes are warmer and drier in the northern hemisphere
- southern facing slopes get direct sun rays which comes with intense heating and drying
- slope blocks rays with causes oblique sun rays for the northern facing side of the slope which then has less intense heating and more moisture
- different plant types on each side
- rocks may also provide shelter from wind
soil formation
soils are formed by weathering of parent rock and the addition of organic matter
- geologic factor: nature of parent material influences soil characteristics
- climatic factor: temperature and moisture significant to soil formation
- topographic factor: slope and drainage significant
- biological factor : disturbance, earthworms, nematodes, termites, microorganisms
- time factor : soil processes are very slow, length of time needed depends on parent material and environmental characteristics
- soil degradation or erosion can occur in only a few years
- from human perception of time, nonrenewable resource
soil formation process - laterization
- in wet, tropical areas (forests)
- breakdown of humus (organic matter) is rapid
- iron and aluminum oxides precipitate as insoluble compounds, laterites
- excess rain leaches silica (desilifications) and results in loss of cations
- excess rain leads to loss of anions, clay particles and humus have negative surface charge – retention of cations and loss of anions
- very nutrient poor soils
soil formation process - podzolization
- much plant growth, little microbial activity
- humus accumulates
- acids from humus percolate downwards and replace cations that are removed from leaching (rain leaches to rivers and ocean)
soil formation process - gleization
- abundant organic matter builds up at the surface, often as peat
- rich in organic acids, low pH
- clay layer in a partially reduced condition below organic layer
- no leaching
soil formation process - calcification
-semiarid climates with little leaching and calcareous bedrock
- little percolating water
- different productivity depending on vegetation
- poor soils if little plant growth, dependent on input
soil formation process - salinization
- in semi arid areas, capillary action brings water to surface
- intense evaporation leaves behind salts on surface
- white color to the soil
extreme soils
- reflect unusual parent rock
- may result in different vegetation and soil endemics (native)
- e.g. serpentine soils –> state rock
The severely deficient levels of N, P, K, and Ca lead to most serpentine soils inhospitable to normal terrestrial plants
soil texture
- affects drainage and nutrients
- can feel for particle sizes
- sand is largest
- then silt
- then clay
- separates in size classification groups – relative sizes effect water and nutrients, capillary spaces
- look at texture triangle !!
clay high in clay (duh) , low in silt and btwn 30 - 70 % clay
then you can have sandy clay, silty clay, etc
biome geographic distribution
biomes show a strong latitudinal distribution
- reflects climate, soil and topography
- left to right: trees –> grasses + other growth forms
biome geographic distribution – Arctic
ARCTIC : extreme seasonality, freezing temp
- 66.5 N or S
- Left = boreal forests , Right = polar/ arctic biomes
- left to right; decrease in precipitation
biome geographic distribution – Temperates
TEMPERATES : seasonality, cool
- 23.5 to 66.5 N or S
- Left = temperate forests, Right = temperate grasslands
- left to right; decreased precipitation
biome geographic distribution – Tropics
TROPICS : little seasonality, direct sunlight
- 0 to 23.5 N or S
- Left = tropical forests, Right = deserts
- left to right: increasing acidity
Vegetation classification schemes
use climate to predict the vegetation zones/ biomes
WHITTAKER
- more simple, annual precipitation v. average temperate can tell us what biome will thrive in that climate
HOLDRIDGE
- more complex, triangle that takes into account factors: latitudinal regions, altitudinal belts, and humidity provinces, potential evapotranspiration ratio, and annual precipitation (mm)
Plant Classification: Phylogenetic - Evolution
closely related species are grouped together in the taxonomic hierarchy
Plant Classification: Functional - Ecophysiology
bridges the gap between plant physiology and ecosystems
- plant growth forms such as trees
- plant functional types such as photosynthetic strategy
convergent evolution
the independent evolution of similar features in species of different lineages, often results in similar growth forms and functional traits in similar environments, e.g. cactic and euphorbs or aloe and agave
- reflects adaptation to the environment
physiognomy
external appearance of vegetation growth forms:
- type
- abundance
- spacing
growth forms
reflects adaptive strategies to unfavorable seasons
- will look specifically at Raunkiaer’s classification that is based on the position of the perennating bud relative to the soil –> dormant perennating buds resume growth in spring
- growth forms differ in abundance in each biome
Raunkiaer’s classification - Phanerophyte
buds on exposed branch tips : trees
Raunkiaer’s classification - Chameophytes
buds close to the ground, protected by the snow
Raunkiaer’s classification - Hemicryptophytes
buds at soil level, protected by dieback : grass
Raunkiaer’s classification - cryptophytes
bulbs, rhizomes, corms, etc., protected by soil
Raunkiaer’s classification - therophytes
seeds
Life form classification beyond Raunkier
life forms based on other criteria, e.g., longevity, succulence, and leaf traits
(1) annual herb
(2) broadleaf evergreen trees
(3) drought-deciduous shrub
(4) broadleaf deciduous tree
(5) stem succulent
(6) bulbous herbaceous perennial
(7) needle evergreen
Plant functional types
plant functional types are nonphylogenetic groupings of species that show similarities in their response to environmental and biotic controls
- derived from traits based on species morphology, physiology and/or life history
- traits used depend on aim and scale of research
- extends Raunkiaer and used extensively in vegetation/climate modeling
Floristics
the study of the distribution, number, types, and relationships of plant species in an area or areas
- historical (does it arrive?) , physiological (can it germinate, grow, survive, and reproduce?) and biotic (does it successfully compete and defend itself?) filters determine species composition
Floristics - historical filter
Is explained by millions of years of evolution in the context of factors such as climate change and continental drift
- explains coefficient of biotic similarity: “shared plant families” found between different regions
- closer relationships exist between continental land masses that remained contiguous for longer periods of time
Floral Kingdom
a large geographic area with a relatively uniform composition of plant species
- have a high degree of FAMILY y endemism
- floristic regions by a high degree of GENERIC endemism, floristic provinces has a high degree of SPECIES endemism
endemic
distribution is restricted in to a particular geography
- may reflect tight ecological relationships
- paleoendemics: relict species (more widespread or diverse in the past)
- neoendemics: “newly” evolved
Plant Function Types Traits - size
ability to capture and control resources at the site (respiration requirements of greater biomass)
Plant Function Types Traits - woody v herbaceous
support: water loss; potential for water uptake and for photosynthesis; permanent occupancy of space
Plant Function Types Traits - annual/perennial
all-or-nothing colonization strategy vs. storage and growth
Plant Function Types Traits - evergreen/deciduous
use or whole growing season: competition vs. stress tolerance strategy
Plant Function Types Traits - root turnover/longevity
investment in opportunistic vs. reliable water and nutrient uptake
Plant Function Types Traits - root/shoot ratios
ratio of water loss to water uptake surface areas; re growth reserves
Plant Function Types Traits - branching height
taller growth if single main stem: greater control over available light
Plant Function Types Traits - branching pattern
potentially taller if monopodial (with side branches), greater leaf area
Plant Function Types Traits - root spread/depth
opportunistic vs. reliable water and nutrient uptake
Plant Function Types Traits - suffrutescence
permanent root system for water uptake and re-sprouting
Plant Function Types Traits - leaf size
potential light capture (photosynthesis) vs. overheating (water loss)
Plant Function Types Traits - leaf shape
control over water loss and internal hydration
Plant Function Types Traits - surface ‘hardness’
control over water loss (vs. potential photosynthetic rate)
Plant Function Types Traits - chlorophyll density
shade tolerance vs. light requirements
Plant Function Types Traits - photosynthetic pathway
enhanced photosynthesis in hot (C4) or dry (CAM) environments; reduction of photorespiratory losses
Plant Function Types Traits - CO2 requirements
response to CO2 enrichment (tissue C:N ratios)
Plant Function Types Traits - fruit size/number
dispersal strategy
Plant Function Types Traits - seed size/number
colonization vs. investment strategies
Plant Function Types Traits - re-sprouter/ non-sprouter
re-growth after severe loss of above-ground biomass
Plant Function Types Traits - vegetative spread
reproduction under differing conditions; re growth potential
geographic distribution - tropical forests
latitudinal distribution: occur between the Tropics of Cancer and Capricorn (23.5 N and S)
within this region – where rainfall is more than 1500 mm per year and no frost
3 geographic regions recognized…
(1) American (50%) – Neotropical, most diverse
(2) Asian (30%) – Indo Malaysian
(3) African (20%) – West African, least diverse
climate - tropical forests
temperature – means are above 18 C every month, no more than 5 C variation annually, no frost
rainfall – more than 1500 mm per month, no month is less than 60 mm, little seasonality
altitude affects trees/plant life – higher up can create Elfin Forests and Cloud Forests while lower will form lower montane rainforest and lowland rainforest
intertidal: of or denoting the area of a seashore which is covered at high tide and uncovered at low tide
species diversity - tropical forests
species diversity is high
- trend of increasing diversity towards the equator (makes sense as less extreme conditions) –> trees 10 x increase, birds + bats + reptiles + amphibians 5 x increase
- Neotropics most diverse, African tropics least diverse
Refugium Hypothesis (Haffer 1969)
- explanation for high species diversity in the Neotropics
- a cyclical vicariance mechanism results in a speciation pump
- during the Pleistocene, advances and retreats in glaciation occurred –> these cyclical climate changes are associated with Milankovitch Cycles and resulted in reversible fragmentation of the forests –> allopatric speciation occurred in isolated fragments or ‘refugia’ –> re-establishment of forest between refuge resulted in sympatry of daughter species –> increased local diversity
Milankovitch Cycles
The three main orbital variations
(1) Eccentricity: changes in the shape of the Earth’s orbit
(2) Obliquity: changes in the tilt of the Earth’s rotational axis
(3) Precession: wobbles in the Earth’s rotational axis
Interact to produce climate changes over 10,000 to 100,000 years
Responsible for advances and retreats of glaciation during Pleistocene
Allopatric Speciation
two populations experience gene flow –> gene flow is interrupted by a geographic barrier. variant types appear –> drift and different selection pressures cause divergence between isolated gene pools –> reproductive isolation is present even though geographic barrier has been removed. speciation is complete
Evidence FOR the Refugium Hypothesis
regions of high endemism in present day plant and animal distribution correlate with supposed distributions of refugia
Evidence AGAINST the Refugium Hypothesis
- refugia were areas of environmental uniformity
- entire Amazon Basin experienced depressed temperatures
- molecular clock suggests some ‘sister lineages’ split before
Andes as a species pump hypothesis
- possible explanation for high species diversity in the Neotropics
- cycles of sympatry (glacial) and allopatry (interglacial)
- vicariance based speciation after uplift
- dispersal based speciation after uplift
Area hypothesis
- possible explanation for high species diversity in the Neotropics
-larger areas support greater number of species –> greater area covers more habitats and bigger areas are larger geographical targets for isolating barriers to arise
Favorable climate hypothesis
- possible explanation for high species diversity in the Neotropics
- fewer species can tolerate climatically harsh conditions
Biotic interactions - competition hypothesis
- lack of seasonality allows more intense competition
- competition narrows niche breaths and allows greater species packing along resource axes
Structural characteristics - tropical forests
STRATIFICATION
vertically stratified; 5 strata
A stratum: discontinuous emergents
B stratum: intermediate, denser
C stratum: shortest
D stratum: palms, herbs, ferns
E stratum: herbaceous, tree seedlings
A-C = trees
- crown shape varies with stratum: canopies become progressively conical with decreasing height
- stratification and crown shape are adaptations to sunflecks
Sunflecks and Temperate forests
sunfleck: light that reaches the forest floor through the canopy
- vertically, light entering a gap passes through a triangle
- decreasing intensity as you go down
-BUT triangles from adjacent gaps will overlap to create a zone of spatially uniform light in the lower forest
optimum tree hight = the upper limit of the spatially uniform light
- competition would drive plants to upper limit of spatially uniform light
- exceeding the limit would be disadvantageous as the heterogenous light environment increases construction and maintenance costs
consequences of vertical stratification
-increases species packing and increases species diversity
-microenvironment differs in different strata: canopy extreme, floor less variable
tropical forests - trees
Raunkiaer’s phanerophytes
- ROOTS – buttress (support), stilt (support + breathing). and pneumatophores (breathing)
- STEMS – lack growth rings or rings not seasonal
- LEAVES – leaf form is very variable, leaf size is large and increases light interception, gradient of increasing size from canopy to floor, heat dissipation by compound leaves (loose heat more effectively by conduction and convection) and steep leaf angles (vertical leaves absorb less radiant energy and loose heat more effectively by convection)
- also have drip tips which increase runoff and hydathodes which release water in order to prevent flooding
tropical forests - epiphytes
plants growing on other plants for support
- selective advantage: space in the sun at low carbon cost
- environmental stress: shortage of water and nutrients
- examples; Bromeliaceae and Orchidaceae
tropical forests – adaptations to water shortage
(1) desiccation tolerance
(2) tanks and trichomes
(3) leaf and stem succulence
(4) valemen
(5) crassulacean acid metabolism (CAM)
tropical forests – desiccation tolerance
the ability of an organism to withstand or endure extreme dryness, or drought like conditions
tropical forests – tanks and trichomes
water accumulation in plant
-water stress was associated with increased trichome density due to plasticity in cell size
tropical forests – leaf and stem succulence
- thick stems for H2O storage
tropical forests – valamen
- outer layer of empty cells in aerial roots
-The velamen radicum is an important adaptive structure for orchids in epiphytic habitats because it allows for rapid water-absorption under wet conditions but also provides a barrier to transpirational water loss from the internal cells of the roots when the environment is dry
tropical forests – CAM
stomata are open at night thus conserving water (enzyme activities are separated in time)
-In this pathway, stomata open at night, which allows CO2 to diffuse into the leaf to be combined with PEP and form malate. This acid is then stored in large central vacuoles until daytime. During the day, malate is released from the vacuoles and decarboxylated.
- In CAM plants, photosynthesis is proportional to vacuolar storage capacity, so CAM plants usually have thick and fleshy water-storing leaves or stems
- water leaves when stomata open but needs to be open to make energy (metabolism) –> results in low productivity and slow growth
adaptation to mineral nutrient shortage..
(1) tanks - humus
(2) Velamen
(3) Trichomes
(4) Carnivory – to obtain nutrients like nitrogen + nitrates
(5) mutualism with ants – ants put waste into certain areas, very nutrient rich and taken up by plants
Lianas
- climbers, woody vines, semi-epiphytes
- rooted in soil
- uses trees as support away from the ground
- SELECTIVE ADVANTAGE: save carbon investment in thick stems
- ADAPTATIONS: tendrils, anomalous secondary thickening resists torsion, wide xylem vessels
phenology
the study of periodic biological phenomena in relation to climate
leaf development
leaf replacement - occurs for all species
- leaf life span 3m to 3y
- asynchronous: evergreen, wet
- synchronous: deciduous, dry
- deciduousness increases higher in canopy and at higher latitudes
flowering
dependent on whether dry seasons occur
- none: same time each year but can be any time of year, hydroperiodic
- yes dry season: staggered flowering reduced competition for pollinators
staggered fruiting
- reduces competition for dispersers
gregarious fruiting
- many trees/species in a population show synchronous fruiting
- reduce predation
masting
- production of many seeds by a plant every two or more years in regional synchrony with other plants of the same species
-reduce predation
dioecious species
20-40% enhances outcrossing
- male and female flowers on different plants
synoecious species
- male and female in same flower
monoecious species
male and female flowers on same plant
pollination
- little wind pollination
- birds, insects, reptiles, and bats act as pollinators
- co-evolution increases cross pollination
- nectar composition and volume reflects pollinator
- ants are inefficient pollinators: extra floral nectaries
- raindrops can also cause self pollination
cauliflory
- flowers on stems
- common in C and D strata
- associated with large animal pollinators and preduncleflory
caulicarpy
-fruit on stems
- allows small trees to attract specialized feeders of understory
- enhances dispersal
seeding patterns – dispersal
- decreases predation
- locates germination sites
- dispersal agents include birds, bats, rodents, and monkeys
- effectiveness of agent depends on eating habits
seeding patterns – predation
- high
- may enhance germination – not common in the tropics
- enhances species diversity ESCAPE HYPOTHESIS
escape hypothesis
- predators are relatively species specific
- thus predation is greatest near parent plant where most seeds fall
- probability of survival is inversely related to predation and hence increases with distance from the parent plant
- therefore max recruitment is at a distance from the parent plant
- parent plant will not be replaced by itself, increases diversity
- masting may increase the chances of self replacement
seedling patterns – germination
- most germinate within 6 weeks, i.e., many species have RECALCITRANT (versus orthodox) seeds
- growth is arrested at the seedling stage: OSKARS
- gap formation and light releases oskars to mature
Gaps
- gaps form when trees fall due to: age, hurricanes, flooding/rain, clearing
- gaps have higher light intensity
- gap light environment depends on: gap type, gap size, gap direction
- light and successional stage affect species composition
-small gaps, low light, promote oskars - very large gaps (and clearing) light stress for oskars
tropical forests represent a mosaic of successional phases: gap, building, mature
intermediate disturbance hypothesis
- gap formation increases species diversity
- intermediate disturbance such as an intermediate amount of gaps (not enough to get to clearing), can support both k and r selected species
k-selected= exhibit logistic growth, have longer life spans
r-reselected= short life spans, exponential growth
illipe nuts
a borneo case study of disturbance effects on a gregarious fruiting species
- illipe nuts are obtained from dipterocarps
- dipterocarps show closely coordinated fruiting but on an irregular schedule (super organism)
- El nino trigger
- records come from illipe nut exports
- fruiting occurs every 3-6 years, coinciding with El Nino –> drought July/Aug, flowering Sept, fruit Feb/Mar
- fruiting is synchronous/gregarious, but irregular: animals cannot learn
- predator population remains small
time between el nino events
Decreased time between el ninos leads to reproductive failure
- disturbance –> fewer trees –> fewer seeds: all eaten
tropical forests – productivity
high for tropical rainforests because of
- light
- water
- mesic temperatures
- low seasonality
productivity
rate of accumulation of energy or biomass
nutrient cycling
- nutrients cycle between abiotic and biotic compartments
- compartments may act as reservoirs
- rate of nutrient cycling (not reservoir size) most important in determining plant productivity
- “efficient cycles have low outputs”
tropical forests – nutrient cyclingars
- soils: poor, low nutrient status
- most nutrients in plants and recently dead organic matter
–> plants are recapturing dissolved minerals as they are released during decomposition
DECOMPOSITION: rapid, agents used are termites, bacteria, fungi
MECHANISM TO ENHANCE UPTAKE: mycorrhizae, surface roots, sclerophylly
REPLENISHMENT OF SOIL NUTRIENTS FROM: weathering of parent rock, atmosphere –> very low amounts and slowwww
Ancient African fish dust nourishes Amazon
-dust blown from the Sahara to the Amazon contains essential nutrients
- Phosphorous in the dust is derived from the bones and scales of fish and other organisms that lived in Megalake Chad, thousands of years ago
- fish phosphorous more soluble than that from rocks
tropical rain forests show fragility to…
- clearing
- slash and burn
- logging
