Forestry Midterm

Main causes of soil erosion

changes to land use and management practice that do not prioritize soil conservation

1) Abiotic factors

2) Biotic factors

Two factors soil consists of

Soil conservation

the balancing of the rate at which parent material is broken down and organic material is mineralized with the rate at which soil is removed through erosion

1) weathering of parent material (underlying rock)

2) deposition of organic matter

Two ways soil is formed

Forest impact on soil formation

1) root systems promote rock weathering by giving access to air and water

2) roots provide a structure that holds developing soil in place

3) provides residues like branches, leaves, and organic matter that decompose and provide acids, nutrients, and top soil.

Humus

Dark, organic material that forms in soil when plant/animal matter decays and is accumulated in organic carbon

• Key energy source for the soil biota central to decomposition

organic carbon

carbon-containing compounds that typically come from living organisms and their remains

1) easier access to food (leaves, fruits, and insects)

2) more resilient body sizes

benefits to the primates of arboreal lifestyle

difference between fruit and leave based-diets

Leaves are readily available in trees, while fruits are dispersed and harder to get. Fruits also have larger energy outputs. Eating fruits meant less fruit was needed, and more memory and effort were required to find them → resulting in monkeys of similar sizes having brains 25% larger → leading to further sophisticated developement.

1) larger brains = larger bodies, which are harder to move in in trees.

2) The Clambering hypothesis - larger monkeys with larger brains evolved to have self-aware sense in order to move in trees

→ results in the age of the Great Apes

the costs and result of arboreal lifestyle

Development of adaptations from grasslands and savannah.

• 25 million years ago, climates started cooling, causing wet seasons to be interspersed with longer dryer seasons.

• From these longer, dryer seasons, forests retreated and herbaceous plants and grasses took over.

• adaptations to live in these conditions included traveling between scattered trees, accessing new food such as roots and grazing animals, and protection from larger predators

benefits of cooking food after the development of fire

1) being able to cook food: breaks down structural components within meat and plants to make them more digestible and allows for more energy to be retained

2) less time to digest food allowed more time for further brain development, including tool-making, building camps, and managing fire

3) changes in teeth and skeleton that allowed for the facial development of homo erectus

Results from utilizing fire

1) change in diet, energy intake, and body structure

2) moving from hunter-gatherer to being able to manipulate vegetation patterns and improve access to food

ecological consequences to utilizing fire

1) loss of forested area and increase in grassland

2) communal hunting that used fire and tools made from fire that moved homosapiens to the top of the food chain.

• promoted grasslands > forests

expansion of agriculture through deforestation

Tools developed from fire and stones became utilized for felling and removing trees, allowing for more grasslands to be made and land to be utilized for agriculture

Problem with early, Mesolithic shift to agriculture

great arsonists, not great agriculturalists

removal of forests with fire caused an initial level of fertility, but over time caused yield decreases from the depletion of nutrients.

this pattern lead early agriculturalists to move and burn through patches of forest fast.

Neolithic shift to agriculture

first shit to sustainable agriculture

used deforested floodplains and valleys for agriculture because regular floods rejuvenatedThe the fields with nutrients

benefits to the development of sustainable agriculture

1) development of argicultural technology like manures, terracing, following, and mixed rotation

2) increased food output which in turn lead to more significant settlement sizes

the advent of civilizations

• Triggered by the ability of humans to produce more food than they needed and not requiring everyone to be involved in food production

• lead to designated systems and development of arts/crafts and more questioning about political power

Causes for the fall of civilizations (ex: Mesopotamia)

Ultimately when food and fuel systems are so weakend that they can no longer meet the demands of a growing civilization, also caused by

• overgrazing

• loss of upstream soil and nutrients from deforestation

• yields of food and fuel maintaining while population increases

Genetic Biodiversity

genetic variation within population and species

• Care about protecting it to protect species against environmental and biological threats

• ex: sequioia trees

species biodiversity

the number of species present

• identifying and caring for threatened and endangered species and reducing the rate of species extinctions

• ex: predator free NZ

Ecological Biodiversity

the variability within and between ecosystems

• maintaining intact ecosystems to safeguard genes, species diversity and ecosystem processes

• ex: National Parks act 1980

Problems with Measuring biodiversity

1) definitions of species and ecosystems is not precise

2) knowledge on taxonomic groups is very poor (estimated potential number of species is 50 million with only 1.8 defined)

geographical patterns with biodiversity

decreases as latitude and longitude increases (increases as approach equator)

threats to biodiversity

• Habitat Change - mainly from forest clearing activities like deforestation

• Climate Change

• Invasive Species

• Over exploitation

• Pollution

Dominant drivers of tree cover loss

1) Wildfires

2) Shifting Agriculture

3) Forestry

4) Commodity-driven deforestation

reasons to conserve biodiversity

1) Utilitarian; biodiversity is of direct benefits to humans such as food, medicine, wood products, ect..

2) Ethical: All species have the right to exist so that biodiversity has a value in its self, reason independent of humans

3) Identarian: Human identity is linked to a sense of connection to place to which the presence of wild places and species contribute. It provides us with a sense of belonging

Transition from ancient civilizations to the dark ages (400CE-1100CE)

By the end of the Roman Empire, temperate Europe had witnessed mass deforestation (15% of forests left), causing populations to go into rapid decline.

Transition from Dark Ages to middle ages (1100-1500 CE)

European forests started recovering from the Dark Ages following climate cooling, causing crops to start surplus-yielding again, new agrotechnology to be implemented, and centralized authority to rise again.

Forests during this time was also seen as a resource to be utilized by nobles.

Rural Modernity (1500-1800 CE)

Following rising wealth and population from the Middle Ages, individual land ownership became more popularized, and pressure on forests moved from hunting to fuelwood, construction, and shipbuilding while more land clearing.

The reduction of forests caused government and rudimental regulations to be implemented to manage practices.

Colonization of foreign lands for land and forests also started during this period.

Deforestation of Central America by colonization

European countries started colonizing for forest resources. Central American countries provided temperate and tropical rainforests, which land was taken and used for sugar, coffee, bananas, and cotton.

Greatest rate of deforestation, which occurred in the later half of the 19th century.

Deforestation and Colonization in SE Asia

European Colonists promoted deforestation to promote the growth of cash crops for exports to meet population demands. Local forests also had timber specialty value.

Urban Modernity - (1800CE - present)

The Industrial Revolution significantly impacted where people lived, the productivity of agriculture, and the materials required for goods.

More people moved to cities, coal, oil, and gas replaced wood fuel, and agricultural production became more efficient within smaller land boundaries.

The relationship between population growth and loss of forest land area reversed

Change in attitudes towards the natural world (1500-1800)

Argued by Thomas- Anthropogenic views of the world started being questioned regarding humans placed at the center of the universe.

examples include …

• zoology studying animals for their knowledge, not use

• pets

• Astronomers/geologists arguing the world is not at the center of the universe

• romanticizing forests in landscapes

arguments against sustainable plantations

• fewer biodiverse species and environmental services

• impact on local communities

• nutrient depletion

• monocultures of exotics

Arguments for sustainable agriculture

• Reduce the amount of wood taken from native forests.

• highly productive and efficient

• Used for soil stabilization and rehabilitation of degraded land as well as for timber production.

pyrolysis

process of heating something without oxygen.

Lack of oxygen causes material to heat up to a hotter temperature

used to make charcoal

can make solid, liquid, and gaseous biofuels this way

Gaseous Biofuels

used in the mid 19th - 20th century automobiles

starting product for liquid fuels

liquid biofuels

pyrolysis oil - diesel substitute

ethanol/methanol - petrol substitute, made by bio/chemical conversion with or wood fermentation from gaseous pyrolysis

Fischer - Tropsch

Methods of Carbon Capture and storage

• Bio-Energy with Carbon Capture and Storage (BECCS) - needs renewable electricity, higher investment, smaller environmental impacts

• Direct Air Carbon Capture and Storage (DACCS) - produces electricity, lower investment, and larger environmental impacts.

Why is wood a good material?

Utilization - it has been used for 1.5 million years, is easy to shape and use, provides raw material for lots of other materials and energy

Health - promotes well-being and generally has positive attributes.

Environmental benefits - it is sustainable, favorable CO2 balance, biodegradable product

classifications for application of wood

structural application - practicality

appearance application - visuality

benefits of wood being a variable material

with a range of different wood-materials, there is more choice for what could be used

costs of wood being a variable material

wood can be unpredictable and unreliable in long-term use

Why wood can’t be physically replaced with a man-made material

Wood natural wood is organized at a complex level where each component within the wood can be adjusted in any way( it is both isotropic and anisotropic depending on the angle). No man-made material can replicate the versatility of wood.

• has been tried but can’1 even replicate the basic components of cellulose

Three key molecules in the cell wall of wood

• lignin (an organic polymer)

• cellulose (organic polymer, polysaccharide)

• hemicellulose (polysaccharide)

cellulose

most abundant polymer on earth, gives strength to the cell wall because it aligns in fibrils

used in paper, cotton, and fuel

sourced from wood, annual crops, and weird sea bacteria

lignin

• second(maybe third) most abundant polysaccharide on earth

• creates the hard(able to withstand compression forces), woody tissue within trees that also makes them more durable compared to plants

• was practically the molecule that allowed for trees to conqueror land

• mainly burned and used as an energy source

Microfibril Angle (MFA)

The angle at which cellulose fibrils run against the cell wall (the grain) of the tree

• low angle indicates that the fibrils run closer to the grain (up and down) while a high angle (90* max) indicates that the fibrils run away from the grain

• typically, trees have higher angles when they are young so they can bend, and then the MFA lowers as the tree gets bigger and older.

• the lower angles are typically preferred for structural wood applications because the wood does not bend

Soil Layers

1) hummus

2) topsoil

3)subsoil

4) weathered rock fragments

5) bedrock

Humus contributes to the formation of stable soil aggregates which…

1) Increased the diffusion of water and air through the soil

2) form an ion exchange surface (adsorption) that hold soil nutrients

Universal Soil Loss equation

A = RKLSCP

• A = mass of soil lost per unit area

• R = rainfall

• K = soil erodibility factor

• L = length of slope

• S = slope gradient

• C = cropping management factor

• P = erosion preventability factor

Temperate Forest

• Largest source of industrial wood sources

• large continuous canopy with broad-leaf trees

• located between 25-50 degrees lat of the equator

Boreal Forest

• Open Conifer forests that grow on swampy grounds typically covered in lichen.

• characteristically covering northern Eurasia and North American

• Can withstand changing seasons and colder temperatures

subtropical forests

• tropical forests but just a little more north

• located between 10-25 degrees lat of the equator

Tropical Forests

• largest type of forest worldwide

• marked by evergreen trees and continuous canopy’s

• located within 10 degrees of the equator and receives at least 250 cm of rainfall annually

Four Key Factors that influence forest type and distribution

1) Climate

2) Soil

3) Topography

4) Disturbance

Photosynthesis and Tree growth

• For trees to grow, the rate of photosynthesis must be greater than the rate of respiration. ratio = (photosynthesis/respiration)

• Ratio = 10 for a growing community

• Ratio = 0 for a climax community

• Ratio < 0 for a declining community

Factors that impact tree growth (photosynthesis)

• sunlight availability (radiation)

• water access (roots)

• temperature

• CO2

• nutrient availability

• Oxygen (roots)

Forest will be more complex(diverse) in …

• places that are warm

• places that have plenty of light

• where soil has plenty of water and nutrients

• where soil is fertile

• where the soil is deep and has sufficient air to support root respiration

Productivity and Diversity of forests increase with..

• Increase in temperature

• Increase in water (with the exception of humidity. cause too much humidity causes osmosis)

Factors that influence climate for tree growth

1) Irradiance; increases growth my increasing temperature and energy in photosynthesis

2) Temperature; Decreases along with productivity as as latitude and altitude increase

3) Water availability: Precipitation(P)-Evaopration(Et)

• if P>Et, the forest has sufficient water

• if P<Et, forest does not have sufficient water- which will close stromata in leaf cells and reduce the rate of photosynthesis

Global Hydrological Water cycles

• hydrological cycle on a continental scale

• describes the flow of water from Ocean→ Evaporation → Land precipitation→ Rivers/lakes/groundwater → Ocean

• Water is measured in massive scales

Catchment Hydrologic Cycles

• Cycle of water entering and leaving a specific area/ecosystem

• Measures the change in the storage of water in a specific area

Water Table

the plane underground that separates unsaturated soil(air+water) fr

Transpiration

• When evaporative demands of the atmosphere exceed adhersion force

Water Balance in a catchment equation

Q = P - (E - S + G)

Q = Water yield(streamflow)

P = precipitation

E =evaporation of water from soil, litter, and transpiration

S = change in soil water storage

G = Change in groundwater storage

Factors that impact water yield (streamflow)

• Forest slope

• Vegetation

• Soil Depth

• Texture

Relationship between water yield and forest growth

Planting forests reduces water yield

removing vegetation increases water yield

Factors that measure water quality

• Turbidity (a measure of suspended particles in water (measure of purity))

• pH (level of alkalinity/Acidity)

• Dissolved Oxygen (indicates the ability of water to support aquatic life)

• Temperature

• Presence/absence of nutrients and bacteria

Salinization

• The process by which water-soluble salts accumulate on the surface of soil

• Mainly caused when the water table rises too high → forests prevent salinization by keeping the water table underneath the roots

Ground Water

Water in the saturated zone → below the water table

Two important flows in a hydrologic catchment system

Precipitation (P) → water entering the cycle

Evaporation (Et) → water leaving the cycle

Forest catchment systems

The water yields from this catchment system are the lowest out of any environment because transpiration and leaf volume are favored and promoted

soil particle classifications

• clay (0.002 nm)

• silt (0.002-0.05 nm)

• sand (> 0.05 nm)

Sand soils

• mainly contains particles that are large in size

• Pores have room for air but not for water

Clay soils

• Mainly contains particles that are small in size

• contain a lot of water and little air

Loam Soils

• Soils that have a range of particles sizes (sand and clay)

• has a good balance of air and water - making it ideal for plant growth

Rule of thumb for soil depth

the deeper the soil, the better the growth and resilience

Two sources of essential elements for soils

1) parent material

2) Soil organic matter

Nutrient recycling

The release of nutrients from decomposing litter

• allows for forests to grow on poor soils because they put nutrients into the soil

Nutrient recycling

• Internal - within trees through translocation from old leaves to new

• External - dead plant and animal matter that is broken down by microorganisms