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Biological and physical cycle in nature (自然界の生物・物質循環)

Mount Usu / Sarobetsu post-mined peatland
From left: Crater basin in 1986 and 2006. Cottongrass / Daylily

geosphere (地圏)
domain of the earth inside

↓ lithosphere
↓ asthenosphere
↓ mesosphere
↓ outer core
↓ inner core

hydrosphere (水圏)
domain consisting of water ≈ ocean + lake + river
atmosphere (大気圏)
domain covered with air
biosphere (生物圏)
domain where natural life forms occur (s.l.) → biota (s.s.)

[biogeochemical cycle, nitrogen cycle, water cycle, biomagnification, trophic level, photosynthesis]

Material and energy cycles

Balance of energy
One of Commoner's lasting legacies is his four laws of ecology, as written in The Closing Circle in 1971. The four laws are:
  1. Everything is connected to everything else. There is one ecosphere for all living organisms and what affects one, affects all.
  2. Everything must go somewhere. There is no "waste" in nature and there is no "away" to which things can be thrown.
  3. Nature knows best. Humankind has fashioned technology to improve upon nature, but such change in a natural system is, says Commoner, "likely to be detrimental to that system"
  4. There is no such thing as a free lunch. Exploitation of nature will inevitably involve the conversion of resources from useful to useless forms.

Biogeochemical cycle (生物地球化学循環)

Circulation at global scale → material cycle observed between atmosphere-hydrosphere-geosphere-biosphere
thermal cycling
water cycle = hydrologic cycle
atmospheric circulation
thermohaline circulation
material circulation,
Classification by materials
nitrogen cycle (N)
oxygen cycle (O)
carbon cycle (C)
phosphorus cycle (P)
sulfur cycle (S)
water cycle (H2O)
hydrogen cycle (H),

Stemflow (樹幹流)

(Parker 1983)

[ isotope ( 同位体 )]

Stable isotope (安定同位体)

Detecting: direct linkage between lithosphere, biosphere, atmosphere, etc.


Sample ratio as it relates to the standard is in the following form:
δX (‰) = (Rsample - Rstd)/Rstd × 1000
______ = (Rsample/Rstd - 1) × 1000

δ: the isotopic notation
X: the element in its heavy form (e.g., 13C and 15N)
R: the ratio of heavy to light isotopes (e.g., 13C:12C)


Δ = {(δsource - δsample)/(1 + δsample/103)} × 103 or
Δ = δsource - δsample

International standards
A 0‰ value of the δ-scale
Internal lab standards must be corrected to international reference standards
δ13C = Vienna peedee belemnite (VPDB)
δ15N = atmospheric nitrogen

Fractionation (分別)

Equilibrium fractionation, e.g.,
α18Owater-vapor = (18O/16Owater/18O/16Ovapor)

occurring when substrates and products of chemical equilibrium reactions differ in their isotope ratios because the heavier isotopes create stronger bonds with either the substrate or product
Ex. CO2 + H218O ↔ H+ + HCO3- ↔ C18O2 + H2O

Kinetic fractionations (= non-equilibrium fractionations), e.g.,
α = Rreactant/Rproduct

occurring when a single type of molecule changes phase (e.g., from liquid to gas) or when the chemical reaction is non-reversible
Ex. in colder temperatures evaporation of H2O molecules from a water body is faster than D2O ones because the intermolecular bonds for the former are weaker

Fig. Interactions between processes that influence stable isotope ratios of herbivores and carnivores, showing biochemical, physiological (underlined), and behavioral (in rectangles) processes. Solid lines represent ecological interactions; dotted lines represent factors affecting diffusion rates and enzymatic reactions (i.e., photosynthesis, nutrient routing and nutrient recycling). A single isotopic value obtained from tissue of a carnivore is the emergent property of multiple ecological, behavioral, and physiological processes of various ecosystem components. (Modified from Ben-David et al. 2001). (a) Effects of marine subsidies on wolf diets and ungulate population dynamics are described in Adams et al. (2010).
Fig. Trophic enrichment in δ13C and δ15N from primary producers (plants), to herbivores, to predators for terrestrial ecosystems. The panel also shows differences in δ13C between food webs based on C3 (black symbols) and C4 plants (gray symbols). Values (mean ± SE) are adapted from the following sources: willows (Salix) from Ben-David et al. (2001); moose (Alces alces) and wolves (Canis lupus) from Szepanski et al. (1999); grasses from Wang et al. (2010); zebra (Equus burchellii) and lions (Panthera leo) from Codron et al. (2007). (Ben-David & Flaherty 2012)
Plant samples
Measurement: TCEA-IRMS (isotope-ratio mass spectrometry)
Sample: dried at 60-80°C → grinded the samples at 40 μm

The smaples are stable after drying up

Nitrogen cycle (窒素循環)

Fig. δ15N in an ecosystem. The unit of numeral is ‰.

Atmospheric reservoir of 0‰
Fractionation is generally low
Nitrification and denitrification are the key sources of fractionation

Nitrogen cycle
Fig.1. Biogeochemical and physical-chemical (pc) processes affecting the speciation of nitrogen in aquatic systems. Highlighted are some of the major reactions considered in the current study, including nitrification, denitrification, anammox, and NH4+ exchange with solids
assimilation (同化), anammox (anaerobic ammonium oxidation) (嫌気性アンモニア酸化), denitrification (脱窒), mineralization (無機化), nitrification (硝化, 硝化作用), nitrogen fixation (窒素固定)
Norg: proteins of plants, animals and microbes, etc.

A. Nitrogen fixation (窒素固定)

B. Nitrogen assimilation (窒素同化)

C. Denitrification (脱窒)

Microbially facilitated process of whcih nitrate (NO3-) is reduced and finally produces N2
Half reactions

NO3 + 2H+ + 2e → NO2 + H2O (nitrate reductase)
NO2 + 2H+ + e → NO + H2O (nitrite reductase)
2NO + 2H+ + 2e → N2O + H2O (nitric oxide reductase)
N2O + 2H+ + 2e → N2 + H2O (nitrous oxide reductase)

The complete process is expressed as a net balanced redox reaction, where nitrate (NO3-) fully reduces to dinitrogen (N2):

2NO3 + 10e + 12H+ → N2 + 6H2O

Carbon cycle (炭素循環)

Fig. δ13C in an ecosystem. The unit of numeral is ‰.

Atmospheric CO2 (≈ -8‰)
C3 photosynthesis ≈ -20‰ fractionation (-28‰ plant tissue)
C4, CAM photosynthesis ≈ 5‰ (-13‰)

Biomagnification (生態濃縮)

Bioaccumulation (生体蓄積・生物蓄積・生物濃縮)
= biological accumulation
the biological sequestering of a substance at a higher concentration than that at which it occurs in the surrounding environment or medium
→ biomagnification + bioconcentration
Biomagnification (生態濃縮)
= bioamplification or biological magnification
the increase in concentration of a substance, such as a pestside, in organisms along a food chain or web as a consequence of:

persistence (not broken down by environmental processes)
food web energetics
low (or non-existent) rate of internal degradation or excretion of the substance, often due to water-insolubility

→ bioaccumulation + bioconcentration
Bioconcentration (生物濃縮)
= biological concentration
the accumulation of a chemical in the tissues of an organism as a result of direct exposure to the surrounding medium, such as water (i.e., it does not include food web transfer)

The three terms described above are often jumbled up.