Boreal Forest: Soil-Vegetation Interactions
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___ trees are first to colonize an area, then ___ arrive
deciduous trees conifers
soil characteristics affect the soil ___ and ___ stores that determine the resulting floristic community
moisture nutrients
soil particles have a ___ charge, so ___ ions like __ become ‘affixed to the soil particle Plants must __ or find a way to get these cations if they want them
negative positively calcium exchange
pedosphere=
soil conditions
the pedosphere is affected by 4 other ‘spheres’: These all change with location!
biosphere (organisms) hydrosphere (water) lithosphere (parent material/ earth) atmosphere (air- energy/ gas exchange)
** 4 main components of boreal forest
• physical template - slope - elevation • Climate - clouds, sun, temp, precipitation • Biota - fire - insect outbreaks - forest structure • Soil - soil temp/ permafrost - soil moisture - nutrient availability - forest floor organic layer
black spruce and tamarack will be found in areas with ___ soils (hydric), and ___ active layer and a ___ organic layer
gleysols (waterlogged) thin thick
White spruce, birch, aspen, and firs will be found in ___ sites with ___ active and organic layers
mesic (flowing moisture) medium
Jack pine thrives in ___ sites with ____ soil where there’s a ___ active layer and ___ organic layer
xeric podzols (dry and sandy) thick (or no permafrost) thin
Which 4 factors drive the community segregation in the boreal forest
moisture soil active layer organic layer
why is there a thin active layer in podzols??
not much organic material stays at the surface because water goes through and take it with it (sandy particles allow water too flow through rapidly)
Soil is composed of: 25% ___ 25%___ 45%___ 5%____
25% air 25% water 45% mineral particles 5% organic matter
What’s one way humans are directly changing the soils?
we compress soils with roads etc= changes the open spaces and makes it less permeable (less air and water can get in)
List the following in order from largest to smallest particle size silt clay sand gravel which one carries the least nutrient availability? Which one has a negative charge & retention of cations?
gravel sand silt clay sand clay
____ hold the greatest volume of water b/c of ___ ratio. Is this water avail to plants?
clay SA not available to plants because clay holds it very strongly
field capacity=
content of water remaining in soil a few days after being wetted and free drainage nearly ends
at the ___ ___, water is still available, but it’s strongly attached to soil, so not very accessible to plants
wilting point
the mosaic pattern of forests in boreal region is related to ___ patterns - ___ in wet areas - ___ in dry areas
drainage spruce poplars
Why does soil have layers? If there’s no ___ there’s no layers
the aging of the materials present on the surface (they leech downward) leeching eg in tropical forests
What are the 6 soil horizons?
• O horizon (humus) • A horizon (topsoil) • E Horizon (eluviation layer- movement of particles downward) • B Horizon (subsoil)- illuviation layer ie movement into horizon • C horizon (regolith) • R horizon (bedrock)
Podzolization=
downward transport of Fe and Al in conjunction with organic matter from the A and E horizons to the B horizon
The __ horizon is lighter in color because the minerals have been leeched out, and the ___ horizon is darker because more minerals including oxidized iron (brown/red)
E B
Soil development and formation process: 1 2 3 4
• additions (eg organic matter falling from trees) • losses (eg leeching or eluviation, or erosion) • translocations= eluviation or illuviation • transformations (chemical eg oxidations/ reduction)
___ layer = taking away –> ___ –> ___ layer= bringing to
eluviation translocation illuviation