Terrestrial environment Flashcards
soil
Loose outer material of earth’s surace
Soil layers
O horizon
A horizon
B horizon
C horizon
O horizon
At the surface, composed of undecomposed plant material
A horizon
Most M growth, rich in organic material and nutrients
Plant roots release nutrients in exchange for ecosystem function
B horizon
subsoil where organic material leached from A gather, little M activity
C horizon
base that is directly above bedrock and forms from bedrock
No O2 and all microbes strictly chemolithotrophs
Soil groups
Mineral soil
organic soil
Mineral soil
Derived from rock weatherig and other inorganic material
Organic soil
Derived from sedimentation in bogs and marshes
soil composition
40% inorganic mineral
5% organic matter
50% air and water
5% M and macro organisms
Soil formation
Formed by interdependant physical, chemical and biological processes
-CO2 is formed by respiring organisms that form Carbonic acid that breaks down rock
-Physical processes such as freezing and thawing break apart rocks, allowing plant roots to penetrate and form an expanded rhizosphere
Rhizosphere
Area around plant roots where plants secrete sugars and other compounds, is rich in organic matter and microbial life
water availibility
It is variable and dependant on rainfall, plant coverage, drainage and soil composition
Soil solution
Soil water has many dissolved materials
soil and water
Well-drained soils have O2 availibility while waterlogged soils are typically anoxic, with O2 being consumed by soil M
Arid soils
They are dry, have limited plant growth and are home to M communities specialised for extreme conditions
-Arid soils lose more moisture from evapotranspiration than gained from precipitation
-Make 35% of land mass and are extreme environments with low water availibility and varied temp ( below -24 and above 60)
BSC
Biological soil crusts are made of photosynthetic cyanobacteria and filamentous fungi that stabilise soil
BSC and arid
Arid soils are very slow to form and are subject to desertification, where BSC is damaged and soil fertility is decreased
Phylogenetic sampling
Molecular sampling indicates thousands of different M species
Phylotype
A species defined by a 16S rRNA sequence that differs from all other sequences by 3%
M diversity varies with soil type and geological location
Red well
Due to M that convert Fe3+ in soil to Fe2+ that goes into water
Most limiting nutrients
Nitrogen
Phosphorous
Polluted soil
-Undisturbed, unpolluted soils support very high Pro diversity
-soil perturbations trigger measurable shifts in community composition toward species that are more competitive
-Polluted soils reduce richness and increase species abundance
Climate and disturbance effects on soil M
Microbial diversity in any environment is a dynamic entity and will change-sometimes dramatically- in response to environmental changes in conditions and resources
Soil subsurface
-extend for sevral hundred meters below soil surface
-Archae and B exist here in variable concentrations depending on nutrient availibility
-Usually grows in extremely nutrient limited environment
-small cells common
Deep subsurface
Home to a group of organisms that may be Archae and are related to Eu, the lokiarcheota
-Generation time can be days, years or centuries depending on nutrients
Determine microbe diversity
-Suspend soil in sterile liquid and then shake and let settle
-Use DNA extraction kit
-Use 16S ALAnine primers to amplify and then sequence DNA
-Use sequence to determine phylotype of soil M
-If % similarity is lower than 97% of reference genome, it may belong to a new species
-If species can’t be determined than full genome sequencing must be done to discover new species
