Forest biogeochemistry

Kalev Jõgiste

In Earth science, a biogeochemical cycle or

substance turnover or cycling of substances is a

pathway by which a chemical substance moves

through both biotic (biosphere) and abiotic

(lithosphere, atmosphere, and hydrosphere)

compartments of Earth.

HUMAN SENSES

• Sight (ophthalmoception), hearing

(audioception), taste (gustaoception), smell

(olfacoception or olfacception), and touch

(tactioception) are the five traditionally

recognized. They help us to recognize the

existence of trees, animals, fish etc. We do

neeed to recognize the process of energy

accumulation at different trophic levels.

• (Kimmins 1997:71).

• Energy enters the ecosystem „goes „ through it and

at the end disappears from the ecosystem

• Chemical substances and compounds which circulate

along with energy flows (they are bound to energy

transfers) are re-used and circulated in the

ecosystem

CYCLES

• 1. Geochemical cycle: transfer and movement of

chemical substances between ecosystems

• 2. Biogeoschemical cycle: movement of chemical

substances within the ecosystem

• 3. Biochemical cycle: transfer and relocation of

chemical components within the organism and between

living organisms

• 96% of plant try biomass consists of atoms of H, O, C N

• MINERAL NUTRIENTS

• Macroelements (H, C, O, N, Ca, K, Mg, P ja S)

• Microelements (B, Cl, Mn, Fe, Cu, Zn, Mo, Ni ja V

micro-organisms)

CLASSIFICATION

• 3. Group (K+, Ca++, Mg++) – Mineral nutrient

essential in many physiological processes including

osmosis regulation , the opening and closing of

stomata (K), photosynthetic transport (K), membran

permeation (Ca), photosynthesis (Mg). K and Mg –

important components of enzymes. The elemets of

this group are bound to ecosystem circulation and

soil

• Enzymes are macromolecular biological catalysts.

They are responsible for thousands of metabolic

processes that sustain life. Enzymes are highly

selective catalysts, greatly accelerating both the rate

and specificity of metabolic reactions, from the

digestion of food to the synthesis of DNA.

• 1. Group (C, H, O) – the components of organic

compounds. C is the scelet of organic substances.

• Carbohydrates: sugar, starch, cellulose, fatty acids,

lipids, phenolic compounds . Those elements are

found in global cycle

• 2. Group (N, S, P) – mineral nutrients which are

bounded with covalent bonds to C (N, S) or O (P and

S). Important components of proteins (N and S);

nucleid accids

• mineraaltoiteained, mis on tugevate kovalentsete

sidemetega ühendatud C-ga (N ja S) või O-ga (P ja

S). Tähtsad proteiinides (N ja S); nukleiinhapetes (N

ja P); aminohapped proteiini tarbeks; ATP-ADP

kompleks. Tugevalt seotud mulla orgaanilise ainega

ja väga tugevast haaratud ringesse.

Microelements

• Group 4. (Fe, Mn, Co, Zn, Mo ja B) – all microelements (except B ) are

important component of enzymes. Fe is important cytochrome and

ferredoxin,

• which are important in electron transport during photosythesis. Many

physiological processes require microelements as activator or mediators.

These elements are bounded to chelate complexes (humus, fulvic acids).

• Geochemic cycle: the input of nutrient to ecosystem

and output

• Is it cycle???

Geochemical cycle - developmental path followed by individual

elements or groups of elements in the crustal and subcrustal zones

of the Earth and on its surface. The concept of a geochemical

cycle encompasses geochemical differentiation (i.e., the natural

separation and concentration of elements by Earth processes) and

heat-assisted, elemental recombination processes.

• C, H, O, N, and S: all those elements enter the

ecosystems or can leave that in gaseous compounds

(but also as vapor, dust or soluble components)

• C, O, N – gaseous intake is main way

Gaseous way

• CO2 – green plants are absorbing from air

• N2 – fixation by microorganisms

• NB! NH3 (ammoniac) the intake by leave from air

can reach 10% of all amount

• N is also in minerals, O is chemically bound, C –

small amount in minerals

• SO2 – small amount is absorbed by leaves

+ (intake)

• SO2 – emitted from leaves and also leaching out

with soluble compounds

• CO2 – emitted with respiration

- output

• All chemical compounds which are mineral

nutrients are moving in sedimentary cycle

• Subdivision: Meteorological cycle

• Intake is realized as dust, aerosol, precipitation

• Output is realized by wind or water erosion

•SEDIMENTARY

• N – Nitrate (NO3-) ja ammonium (NH4+) ion can

enter the ecosystem as wet or dry precipitation

• K, Ca, S, can enter the ecosystem as wet or dry

precipitation

• (P, less than other macro-elements)

+ intake

Nitrate

• Animals: the movement (migration) of animals and

migration of chemical compounds is balanced with

intake and output

BIOLOGICAL MECHANISM

•+ • 1. Weathering and chmeical weathering of rocks

and soil mineral part and release of nutrients.

• 2. Nutrients, compounds that are soluble in water,

and the flow of water entering the soil ecosystem.

•- • Nutrients that have solutions for both soil water and

surface water outflow. Water erosion of organic and

mineral material.

GEOLOGICAL /HYDROLOGICAL

• BIOGEOCHEMICAL CYCLE MEANS THE

CONSTANT MOVING (EXCHANGE) OF

CHEMICAL ELEMETS WITHIN ECOSYSTEM

BETWEEN LIVING AND NONLIVING

COMPONENTS

• 1. Soluble components with water

• 2. Physiological processes

• 2. Mycotrophic

Nutrient uptake

• 1. Leaching with rainwater

• 2. Biomass eaten (consumed) by herbivores

• 3. Reproduction costs

• 4. Litter and mortality

• 5. Litter decomposition

Allocation of nutrients in plants and vegetation:

Movement and exchange in biogeochemical cycle

• LITTER: FALLING DURING ONE YEAR

• LITTER ACCUMULATION

•Mechanism of biogeochemical cycle

Movement of nutrients in plants:

Biochemistry

• Biochemical cycle

• Plant physiology

Proportion % Carbon N H O

Lipids 75-78 - 8-11 9-17

Sugar, starch 40 - 7 52

Hemicellulose,

cellulose

43 - 7 49

Lignin 67 - 6 27

Protein 40-50 10-25 5-10 22-40

The nutrient cycle occupies a key position in ecosystem processes.

Primary production is regulated in large part by the rate at which

nutrients are cycled, and the ability of the system both to store

nutrients and to regulate their release provides stability against

environmental fluctuations and facilitates recovery from

disturbance.

Different plant species and guilds may regulate nutrient cycling in

such a way as to facilitate their own persistence in a community,

thereby creating a self-reinforcing, positive feedback loop between

ecosystem structure and processes.

Nutrient Fluxes in Local Ecosystems

Intraystem Nutrient Cycle

Soil water is the conveyer belt that distributes soluble nutrients

throughout the soil matrix.

Nutrients are exchanged between the soil solution and several

reservoirs.

Plants both take up and release nutrients to solution, and

nutrients in litter and humus are incorporated into the bodies of

microbes and soil animals and eventually released into the soil

solution (where they are available for uptake once again).

Nutrients are exchanged between solution and electrical charges

on the surfaces of clays and organic matter.

Intraystem Nutrient Cycle

Some nutrients, such as iron, from insoluble combinations and

precipitate out of solution, entering again very slowly.

Nutrients may enter soil solution directly from the atmosphere,

and some are released again into the atmosphere as gases.

A few are leached from the local ecosystem to streams, but such

nutrient loss is relatively minor in undisturbed forests.

Components of the Intrasystem Cycle

Intraystem Nutrient Cycle

Any breakdown of ecosystem components is artificial to one

degree or another, we consider the following compartments:

Aboverground plant tissues, along with associated epiphytes and

microbes.

Animals that graze aboveground tissues.

Belowground plant tissues and plant mutualists, including roots,

mycorrhizae, mycorrhizal hyphae, and obligate rhizosphere

bacteria.

Intraystem Nutrient Cycle

Detritus, which is any organic matter that is not contained within

living body or cell or is not incorporated into humus or

organomineral complexes.

There are two distinct forms:

• Litter

• Exudates

A large proportion of detritus derives from plant litter (for

example: leaves, branches, roots, mycorrhizae); litter also includes

dead consumers (for example: microbes, protozoa, invertebrates,

vertebrates and both invertebrate and vertebrate feces.

Exudates are organic compounds that are released into the soil by

roots, mycorrhizae, micorrhizal hyphae, and microbes. A wide

variety of compounds are exuded from living cells, including

simple sugars, organic acids, and enzymes.

Belowground vs. Aboveground Litter – most studies have

focused on aboveground litter (litterfall). However, the few data

that is available suggest that in most forest ecosystems, the death

of roots and mycorrhizae account for two thirds or more of

nitrogen returned to the soil in plant litter.

Aboveground and Belowground Litter

Components of Litterfall in Three

Forest Types: An Example

Nutrient transfers also occur within as well as among

compartments. Trees withdraw nutrients from aging and dead

tissues, and use these to support new growth (for example:

internal cycling). Invertebrates recycle nutrients by eating their

own feces (coprophagy). Decomposers decompose other

decomposers, and grazers feed on other grazers. In general,

belowground food chains are longer and more complex than those

aboveground.

Transfers Among the Various

Compartments

Nitrogen fluxes in a old-growth Douglas-fir

forest in Oregon. Amount of nitrogen input

to this forest in precipitation is quite small,

and roughly equivalent to that leached from

the system.

Nutrient Cycling

The greatest proportion of forests yearly nutrient requirement is

satisfied by elements that are cycled both externally (for example:

in litter) and internally (for example: within the tree).

The relationship between tree uptake (upper line) and release of

nutrients in decomposition (lower line, shaded portion) for an age

sequence of Scots pine plantation in Great Britain. Stands vary

(because of site factors or management practices), but in most cases,

at least 50% of yearly uptake is matched by decomposition.