Transcript Nutrient Regeneration

FIELD BIOLOGY & METHODOLOGY
Fall 2014 Althoff
Nutrient Regeneration
Lecture
08
Cycling & Nutrient Regeneration
• Elements cycle through ecosystems along
paths dictated by their ______________…
a) which determine their chemical
reactions
b) which determine their biological
reactions
• Processes of nutrient regeneration is different
in terrestrial vs. aquatic systems
Terrestrial System: Nutrient
• Nutrients primarily regenerated in the ______
• New nutrients source is formation of soil
through weathering of bedrock…in the deep
layers of the soil.
• This weathering process is relatively ______,
especially in regard to annual uptake of
nutrients by vegetation…so where is the bulk
of the nutrients made available to plants
coming from????
Organic horizon
Horizon generally
lacking significant
organic matter
Root
penetration
and
development
_________
___________
Bedrock
Hubbard Brook Forest –NH study
• 1960s and 1970s
• Evaluated an entire watershed
• Examined “inputs” and “outputs”
Rain gauges used
To measure nutrient
inputs
A watershed
Hubbard Brook
study
--note the sharp
decline in __ in red
spruce trees
following lowest
pH values in
precipitation &
stream water…and
in stream
--Ca leached from
the watershed
--Ca critical to tree
growth
Terrestrial System: Nutrient
• Weathering estimates: ~10% of what plants
annually take up provided by weathering
process in soil
• The bulk (estimated ~90%) nutrients taken up
by plants annually are “regenerated” by the
breakdown of detritus and small organic
molecules within the soil profile
Detritus
• DEFINED:
Freshly _______________organic
matter
• Almost everywhere in terrestrial habitats:
a) parts of plants (dead) not consumed by
herbivores
b) animal excreta (droppings)
• This “layer” is the location of the breakdown
that results in nutrients transforming into forms
that can be reused by plants
“Processing” detritus to regenerate nutrients
• Breakdown of this “___________” on the forest floor,
for example, occurs in 4 ways:
1) _________ of soluble minerals by ______
2) consumption by ____________________
___________ (millipedes, earthworms,
wood lice, and other invertebrates)
3) ___________ of woody components of leaves
by ________
4) _____________ of about ‘anything’ by
___________
Leaves of different species ……
• Decompose at _________ rates.
• Example of first year leaf decomposition rates in
eastern Tennessee forests:
Weight loss of decaying leaves for….
mulberry was
64%
oak was
39%
sugar maple was 32%
beech was
21%
• Decomposition rates also affected by N, P, and
other nutrient concentrations required by
_______ and ______ for their own growth
Temperate vs. Tropical Ecosystems
• Climate effects weathering
• Climate effects soil properties
• Climate effects the rate of decomposition
Tropical Ecosystems
• Deeply weathered, low in clay content means
soils have poor ability to _______________
(low cation exchange capacity)
• Warmer temperatures year-round means
decomposition _______________
• Higher productivity associated with ________
________________ means nutrient uptake by
plants results in retention of nutrients in the
_____________.
Tropical forest: turnover is __?
• Compared to temperate forest, more
nutrients are tied up in living biomass, above
ground
• If we harvest rainforest, therefore, what are
the consequences?
Soil Fertility is Jeopardized
Carbon Content of Soil (soil organic matter)
Canada
Brazil
Venezuelan
prairie
shrub for. rain forest
Carbon
8.8 kg m-1 3.4 kg m -1 5.1 kg m -1
Activity
farming
farming
farming
Years
65
6
3
Decline
1%/yr
9%/yr
29%
Conclusions
• Cultivated temperate zone soils retain organic
matter _____ longer than tropical soils
• Temperate soils provide more _________ store
of mineral nutrients that can be released by
slower rate of decomposition
Review:
• Distribution of mineral nutrients
Ricklefs (1995) (Table 8.1, page 168 – handout)
compare: ash and oak (temperate)
vs.
tropical
“________________________”
• __________ (“well-nourished”) vs. ___________
(“poorly-nourished”) standing crop & fluxes
Ricklefs (1995) (Table 8.2 – handout)
Aquatic Systems
• Nutrients regenerated __________
• Mostly regenerated in ______ layers of water
and sediment
• Algae and aquatic plants assimilate nutrients
from the water column in the uppermost
(sunlight) zones….far removed from sediments
at bottom [contrast to plants & soils]
• More ___________ conditions in aquatic
sediments than in upper horizons of terrestrial
soils
Aquatic Systems
• Thermal stratification hinders vertical mixing
in aquatic ecosystems
• Layering created largely by influence of solar
radiation warming upper zone(s).
• _____________ can also influence O2
concentration levels…thus, affecting bacteria
respiration rates and the water chemistry
p175,Fig. 8.16 (Ricklef’s 5th edition)
Shaded area
time of O2
depletion
(________
_________)
Also, note
time of
“mixing”
Phosphorus & Eutrophication
• Often scare (limiting) in otherwise high-quality
(O2) lakes
• Addition of nutrients, particularly P, in sewage
and/or runoff & drainage from fertilized
agricultural lands can results in nutrient
loading…can be negative if BIOLOGICAL
OXYGEN DEMAND (BOD) results
BOD (_______________________)
• Oxidative breakdown of the detritus by
microorganisms zaps water of dissolved
oxygen.
• Serious problem, especially in winter when
photosynthesis rates are low and little
oxygen in water column…results in fish kill
and other organisms negatively impacted
In summary…
• Nutrient regeneration in terrestrial ecosystems
takes place in the _____ with nutrients
regenerated from leaf litter
• Tropical forest soils differ markedly from
temperate forest soils when it comes to nutrient
__________ and ________________
• Aquatic sediments are ______________ from
sites of nutrient uptake by plants and
algae…more so than soil-to-plant distances for
terrestrial ecosystems
In summary…
• Vertical mixing in aquatic systems is inhibited
by _____________________
• Nutrient regeneration in aquatic sediments is
by _______________ decomposition of
organic matter—often in highly anaerobic
conditions